AREA FORECAST DISCUSSION
NWS BALTIMORE MD/WASHINGTON DC
AFDLWX 900 PM EST SUN JAN 28 2007
.EVENING UPDATE...
VIGOROUS UPPER TROUGH ORIENTED ACROSS OHIO AND EASTERN KENTUCKY ATTM
WITH STRONG VORT MAX EMBEDDED WITHIN TROUGH. TROUGH IS STILL
FORECAST BY SHORTRANGE GUIDANCE TO BECOME NEGATIVELY TILTED AS IT
MOVES INTO THE MID ATLANTIC AND INTERACTS WITH MINOR RESIDUAL
MOISTURE.
SNOW SHOWER ACTIVITY OUT AHEAD OF THE S/W FEATURE IS HAVING TROUBLE
ORGANIZING ACROSS WEST VIRGINIA AND INTO WESTERN MD. BELIEVE SOME
ORGANIZATION OF THE SN SHWR ACTIVITY WILL OCCUR ACROSS THE NRN
PORTION OF OUR CWFA BETWEEN ABOUT 10PM AND 2AM BUT WILL GENERALLY BE
LIGHT. A FEW SMALL SHOWERS WILL CONTAIN BURSTS OF HEAVIER SNOW WHICH
WILL REDUCE VISIBILITY BELOW 1 MILE...BUT HAVE TROUBLE ACCUMULATING
MUCH SNOW...ESPECIALLY GIVEN THE VERY STRONG NW WINDS DEVELOPING UP
TO 30 KT. TROUGH MOVES EAST OF OUR REGION AFTER 06Z AND ANY SNOW
SHWRS WILL DIE OFF LATE TNGT (EXCEPT FOR THE UPSLOPE SNOWS OUT
WEST).
GIVEN THE ABOVE MENTIONED TRENDS HAVE DECIDED TO KEEP ALL HEADLINES
INTACT OUT WEST...BUT LOWERED POPS AND ACCUMS ACROSS THE
BOARD...WITH SCATTERED SNOW SHOWERS FOR A GOOD PART OF THE NGT MOST
AREAS BUT LITTLE OR NO ACCUMS...EXCEPT FOR NRN MD INCLUDING
CBE...HGR...FDK...AND NORTH OF BALTIMORE AREAS WHERE UP TO ONE INCH
OF SNOW WILL BE PREDICTED. ACCUMS OUT WEST HAVE BEEN LWRD TO 3-6" IN
OUR WINTER STORM WARNING AREA IN THE FAR NW 3 COUNTIES...AND 1-3" IN
HIGHLAND AND PENDLETON COUNTIES. DID CONSIDER INCLUDING EASTERN
ALLEG/MIN/GRANT CNTS IN THE ADVISORY BUT BELIEVE ANY ACCUMS ABOVE 1"
WILL BE ISOLATED THERE. AT ANY RATE THIS WILL BE ONE COLD AND
BLUSTERY NIGHT FOR ALL LOCATIONS! WIND CHILL READINGS DOWN INTO THE
SINGLE DIGITS WILL OCCUR EVEN IN THE METRO AREAS LATER TNGT.
JB
&&
.SHORT TERM /TONIGHT THROUGH MONDAY/...
...SIGNIFICANT UPSLOPE SNOW EVENT EXPECTED ACROSS THE MOUNTAINS...
...POSSIBLE LIGHT ACCUMULATIONS ACROSS THE METRO AREAS THIS EVENING
AND EARLY TONIGHT...
WATER VAPOR LOOP SHOWS A SHORT WAVE MOVING EAST THROUGH THE
CAROLINAS...WITH A SHEAR AXIS ACROSS THE FORECAST AREA. THE NEXT AND
MORE VIGOROUS WAVE IS DROPPING SOUTHEAST THROUGH THE MIDWEST. ACARS
400-250MB WIND OBSERVATIONS REVEAL A 100-120KT SOUTHWESTERLY JET
FROM THE MIDWEST INTO NEW ENGLAND...AND A 130-150KT SOUTHWESTERLY
JET FROM THE NORTHERN GULF OF MEXICO THROUGH THE CAROLINAS. 11Z
SURFACE ANALYSIS PLACED A COLD FRONT FROM THE WESTERN GULF OF MEXICO
TO NEAR CHARLOTTESVILLE...THEN EAST ACROSS THE DELMARVA. A 1029MB
ANTICYCLONE WAS LOCATED ACROSS THE CENTRAL CONUS...WITH THE ARCTIC
COLD FRONT STRETCHED FROM THE UPPER MIDWEST EAST ACROSS THE GREAT
LAKES AND NORTH INTO NEW ENGLAND.
A SIGNIFICANT UPSLOPE SNOW EVENT IS UNDERWAY ACROSS THE WESTERN
MOUNTAINS. BAYARD AND MOUNT STORM CHECKED IN WITH 1-1.5" ALREADY
EARLY THIS MORNING. THE NAM HAS BEEN VERY CONSISTENT WITH INDICATING
ABOUT A HALF INCH OF LIQUID EQUIVALENT THROUGH 12Z MONDAY...AND THE
SHORT RANGE ENSEMBLES ALSO HAVE BEEN CLUSTERED BETWEEN 0.5-0.7" FOR
THE PAST FEW RUNS AT KEKN. THE DENDRITIC SNOW GROWTH LAYER IS ALSO
WITHIN THE VERTICAL MOTION FORCED BY THE TERRAIN. WITH REPORTS OF
HEAVY SNOW AND THE ARRIVAL OF UNSTABLE AIR LATE THIS
AFTERNOON...HAVE A WINTER STORM WARNING ACROSS THE FAR NORTHWEST 3
COUNTIES...AND A SNOW ADVISORY ACROSS HIGHLAND AND PENDLETON
COUNTIES.
THIS EVENING AND EARLY TONIGHT APPEAR INTERESTING WITH THE ARRIVAL
OF A VIGOROUS SHORT WAVE. INSTABILITY IS VERY APPARENT WITH 7-9C/KM
LAPSE RATES FROM THE SURFACE TO ABOVE 700MB. EXPECT SNOW SHOWERS TO
ARRIVE FROM THE NORTH AND WEST THIS EVENING WITH THE INSTABILITY.
MODEL GUIDANCE AND MOS DO NOT PRESENT MUCH QPF OR PROBABILITY OF
PRECIPITATION...HOWEVER THIS IS A CASE FOR GOING WELL ABOVE
GUIDANCE. IT DOES NOT TAKE MUCH MOISTURE TO DEVELOP PRECIPITATION
WITHIN AN UNSTABLE AIRMASS ALONG A VIGOROUS SHORT WAVE. IT COULD
SNOW HEAVILY FOR A BIT IN SOME PLACES AS THE DENDRITIC SNOW GROWTH
LAYER IS WITHIN THE UNSTABLE 900-700MB LAYER.
APPEARS BEST CHANCES FOR ACCUMULATION ARE ALONG AND EAST OF
INTERSTATE 95...WHERE THE INCOMING INSTABILITY WILL INTERSECT
REMAINING SHEAR AXIS ALOFT. TO NARROW IT DOWN FURTHER...THE
BALTIMORE METRO AREA HAS THE BEST CHANCES OF AN INCH OR GREATER. FOR
NOW HAVE MENTIONED AN INCH OF SNOW...BUT EVENING SHIFT WILL HAVE TO
MONITOR RADAR TRENDS FOR A POSSIBLE SNOW ADVISORY AS INSTABILITY
COMES IN TO SEE HOW MUCH OF A PLAYER THE SHEAR AXIS IS FOR FOCUSING
SNOW SHOWERS. HAVE ISSUED A SPECIAL WEATHER STATEMENT AS STRONG
INSTABILITY SHOULD PROVIDE FOR HIGH IMPACT SUB ADVISORY CONDITIONS
WITH BRIEF REDUCTION IN VISIBILITIES BELOW A HALF MILE.
WINDS INCREASE OVERNIGHT AS A CYCLONE QUICKLY DEVELOPS WELL OFFSHORE
AND THE GRADIENT STRENGTHENS WITHIN STRONG COLD ADVECTION REGIME.
BUILDING HEIGHTS WILL ALLOW ANTICYCLONIC FLOW TO BUILD IN...CAUSING
UPSLOPE SNOW SHOWERS TO DISSIPATE MONDAY. DOWNSLOPE FLOW...ALBEIT
WEAKENING THROUGH THE DAY...SHOULD BE ENOUGH TO ERODE LOW LEVEL
MOISTURE FROM THE SHENANDOAH VALLEY EASTWARD DURING THE DAY. WENT
BELOW MOS GUIDANCE FOR HIGH TEMPERATURES WITH PRESENCE OF STRONG
COLD ADVECTION AND SOME AREAS OF ANTICIPATED LIGHT SNOW ACCUMULATION
OVERNIGHT.
&&
.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
RELATIVELY QUIET EXTENDED...UNTIL THE END OF THE WORK-WEEK.
ZONAL FLOW IN THE MID LEVELS AT THE BEGINNING OF THE PERIOD. THIS
PRETTY MUCH WILL BE STATUS QUO UNTIL THURSDAY. SEVERAL PIECES OF
SHORTWAVE ENERGY TRAVEL EAST WITHIN THE FLOW...WITH TWO NOTABLE
SHORTWAVES...ONE LATE TUESDAY/WEDNESDAY AND THE OTHER ON THURSDAY.
THE ZONAL FLOW WILL TURN MORE SOUTHWEST LATER THURSDAY AS A TROUGH
DIGS OVER THE WEST-CENTRAL PART OF THE COUNTRY. THE LONGWAVE TROUGH
WILL MOVE EAST THROUGH FRIDAY BEFORE SETTING UP ALONG THE EAST COAST
ON SATURDAY.
HIGH PRESSURE WILL BE BUILDING IN MONDAY EVENING. A FRONTAL BOUNDARY
COMES TROUGH ON TUESDAY...BUT PRECIP REMAINS CONFINED TO WEST OF THE
BLUE RIDGE. UPSLOPE SNOW SHOWERS WILL CONTINUE THROUGH LATE
TUESDAY/EARLY WEDNESDAY. MOISTURE BEGINS TO INCREASE ON THURSDAY
AHEAD OF THE NEXT FRONTAL BOUNDARY AND A DEVELOPING COASTAL LOW
PRESSURE SYSTEM. THE COASTAL LOW IS EXPECTED TO MOVE UP THE EAST
COAST ON FRIDAY. HIGH PRESSURE BUILDS IN FOR THE WEEKEND.
DID NOT REALLY DEVIATE FROM GUIDANCE FOR MOST OF THE EXTENDED...JUST
MADE SOME MINOR TWEAKS. THERE ARE SOME INDICATIONS OF A WINTRY MIX
ON FRIDAY W OF THE BLUE RIDGE...AND WILL HAVE RN/SN MIX FOR NOW.
&&
.AVIATION...
STRONG MID LEVEL INSTABILITY WILL ENTER THE REGION FROM THE NORTH
AND WEST THIS EVENING...ALLOWING CONVECTIVE SNOW SHOWERS TO DEVELOP
THROUGH THE FIRST PORTION OF THE NIGHT. LIFR VISIBILITIES AND MVFR
CEILINGS WILL BE POSSIBLE WITHIN THE HEAVIER SNOW SHOWERS...WHICH
WILL BE ENDING FROM WEST TO EAST BEHIND THE SHORT WAVE BEGINNING
AROUND MIDNIGHT. STRONG COLD ADVECTION WILL MAINTAIN STRONG
NORTHWEST WIND GUSTS THROUGH THE NIGHT...UNTIL THE GRADIENT RELAXES
MONDAY MORNING.
&&
.MARINE...
SMALL CRAFT ADVISORY IN EFFECT. OBSERVED WIND GUSTS ALONG AND WEST
OF THE BLUE RIDGE ARE 20KTS.
12Z ETA/MAV MOS AT THOMAS POINT INDICATE SUSTAINED WINDS INCREASE TO
20KT LATE TONIGHT AND MONDAY. 12Z NAM/GFS PROXIMITY BUFKIT FORECAST
SOUNDINGS SHOW ADDITIONAL MOMENTUM TRANSFER INCREASE TO JUST OVER
30KT LATE TONIGHT. WITH STRENGTHENING GRADIENT AS A CYCLONE QUICKLY
DEVELOPS OFF THE COAST THIS EVENING AND STRONG DYNAMICS PASSING
OVERHEAD...WILL GO SLIGHTLY MORE PESSIMISTIC THAN GUIDANCE AND RAISE
A GALE WARNING FOR 35KT WIND GUSTS THROUGH 10AM.
SMALL CRAFT CONDITIONS ARE STILL POSSIBLE TUESDAY INTO WEDNESDAY
BEHIND THE FRONTAL BOUNDARY. HAVE INCREASED WINDS TO AROUND 15 KTS
OVER THE WATERS...SOME 20KT MAY SHOW UP IN THE BAY.
AS THE COASTAL LOW TRAVELS UP THE EASTERN SEABOARD ON
FRIDAY/SATURDAY WINDS MAY ONCE AGAIN INCREASE TO SMALL CRAFT
ADVISORY LEVELS.
&&
.TIDES...
WATER LEVELS ARE CURRENTLY ABOUT A HALF FOOT ABOVE ASTRONOMIC
PREDICTIONS. THE LUNAR CYCLE IS WAXING TOWARD A FULL MOON IN EARLY
FEBRUARY (79% FULL).
THE CHESAPEAKE BAY OPERATIONAL FORECAST SYSTEM AND THE NOAA
EXTRATROPICAL STORM SURGE MODEL BOTH SUGGEST TIDAL DEPARTURES REMAIN
AT CURRENT DEPARTURES OR GRADUALLY RETURN TO ASTRONOMIC PREDICTIONS
THROUGH TONIGHT.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...WINTER STORM WARNING UNTIL 7 AM EST MONDAY FOR MDZ501.
WIND CHILL ADVISORY FROM 10 PM THIS EVENING TO 10 AM EST
MONDAY FOR MDZ501.
VA...WIND CHILL ADVISORY FROM 10 PM THIS EVENING TO 10 AM EST
MONDAY FOR VAZ021.
SNOW ADVISORY UNTIL 7 AM EST MONDAY FOR VAZ021.
WV...WINTER STORM WARNING UNTIL 7 AM EST MONDAY FOR WVZ501-503.
WIND CHILL ADVISORY FROM 10 PM THIS EVENING TO 10 AM EST
MONDAY FOR WVZ054-501-503.
SNOW ADVISORY UNTIL 7 AM EST MONDAY FOR WVZ054.
MARINE...GALE WARNING FROM MIDNIGHT TONIGHT TO 9 AM EST MONDAY FOR
ANZ530>537.
SMALL CRAFT ADVISORY FROM 9 AM TO 6 PM EST MONDAY FOR
ANZ530>537.
&&
$$
SHORT TERM/AVIATION/TIDES...ROGOWSKI
LONG TERM...LISTEMAA
MARINE...ROGOWSKI/LISTEMAA
AREA FORECAST DISCUSSION
NWS BALTIMORE MD/WASHINGTON DC
AFDLWX 328 PM EST SAT JAN 27 2007
.SHORT TERM /TONIGHT THROUGH SUNDAY/...
WATER VAPOR LOOP SHOWS AN UPPER LOW LIFTING THROUGH THE PLAINS AS
THE SOUTHERN BRANCH JET PUNCHES INTO THE GULF STATES (WITH COPIOUS
MOISTURE ALOFT). THIS IS AHEAD OF THE NORTHERN STREAM WAVE DIGGING
INTO THE UPPER MIDWEST. A RIDGE IS OVER THE EASTERN CONUS. ACARS
400-250MB WIND OBSERVATIONS REVEAL SOUTHWESTERLY 100-120KT JET FROM
THE MIDWEST THROUGH NEW ENGLAND. A 120-160KT SOUTHWESTERLY JET
EXTENDED FROM MEXICO THROUGH THE GULF STATES. 11Z SURFACE ANALYSIS
PLACED A 990MB OCCLUDED CYCLONE ACROSS THE UPPER GREAT LAKES...WITH
THE OCCLUDED FRONTAL BOUNDARY STRETCHED SOUTHEAST TO NEAR
DETROIT...THEN SOUTHWEST AS A COLD FRONT THROUGH THE PLAINS. A
STATIONARY BOUNDARY EXTENDED EAST FROM THE TRIPLE POINT ACROSS
SOUTHERN NEW ENGLAND (WITH A 1014MB ARCTIC HIGH ACROSS QUEBEC). A
FRONTAL BOUNDARY WHICH DEVELOPED OVERNIGHT IS MOVING NORTHEAST AS A
WARM FRONT FROM ERIE PENNSYLVANIA SOUTHEAST TO NEAR
CHARLOTTESVILLE...THEN EAST ACROSS THE DELMARVA. A TROUGH WAS NOTED
IN THE LEE OF THE APPALACHIANS.
EXPECT STRATO-CU TO BUILD SOUTH AS WARM ADVECTION CONTINUES WITH
COOLING ATOP THE BOUNDARY LAYER AFTER SUNSET. MEANWHILE...MID LEVEL
MOISTURE CONTINUES TO STREAM NORTHEAST TOWARD THE MID ATLANTIC AS
THE UPPER LEVEL RIDGE AMPLIFIES IN ADVANCE OF THE NEXT NORTHERN
STREAM WAVE. THIS IS CAUSING THE UPPER LOW ACROSS THE PLAINS TO
WEAKEN AND ERODE INTO PIECES DOWNSTREAM.
BULK OF PRECIPITATION SEEN ON NATIONAL RADAR LOOP WILL REMAIN SOUTH
OF THE SOUTHERN STREAM JET...ACROSS THE GULF STATES AND SOUTH
CAROLINA. OUR PRECIPITATION CHANCES REST ON THE SHEAR AXIS DEVELOPED
AHEAD OF THE NORTHERN STREAM WAVE...CURRENTLY PRODUCING LIGHT
PRECIPITATION (T OR .01 VIA METARS) FROM SOUTHERN ILLINOIS INTO OHIO
VALLEY. BELIEVE THE GFS (AND GFS MOS) IS OVERPLAYING CHANCES OF
SEEING PRECIPITATION...AND LEANED TOWARD THE DRIER NGM/NAM/LWX
WRF-NMM. THERMAL PROFILES WOULD ORIGINALLY FAVOR RAIN...BUT WITH
COOLING BEFORE SUNRISE...COULD SUPPORT SNOW EAST INTO THE METRO
AREA. GIVEN THE LOW PROBABILITY OF ANY PRECIPITATION...LOW QPF...AND
MARGINAL THERMAL PROFILES...AM NOT TOO CONCERNED ABOUT SNOW
ACCUMULATION EAST OF THE HIGHER TERRAIN OF THE ALLEGHENY FRONT.
ALONG AND WEST OF THE ALLEGHENY FRONT IS A DIFFERENT STORY. UPSLOPE
PRECIPITATION COULD ACCUMULATE AS SNOW AS COLD ADVECTION BEGINS
LATER TONIGHT BEHIND THE COLD FRONTAL PASSAGE. 09Z SHORT RANGE
ENSEMBLES INDICATE BETWEEN 0.15-0.30" OF LIQUID EQUIVALENT THROUGH
SUNDAY. HAVE PLACED 1-2" OF SNOW IN THE FORECAST FOR UPSLOPE REGION
(WITH GOOD AGREEMENT FROM NEIGHBORS AND HPC AS WELL). AN ADVISORY
WOULD LIKELY BE NEEDED SUNDAY BEFORE THE SNOW INTENSIFIES SUNDAY
EVENING. WINDS WILL CONTINUE TO GUST 25-30 MPH.
&&
.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
A BUSY EXTENDED FORECAST ON TAP.
BY 00Z MONDAY...LONGWAVE TROUGH AND ASSOCIATED STRONG SHORTWAVE
ENERGY COMING THROUGH THE CWFA. THE TROUGH SHOULD BE EAST OF THE
CWFA BY EARLY MONDAY. ZONAL FLOW RETURNS TO THE AREA LATE ON MONDAY.
A SECOND STRONG SHORTWAVE COMES THROUGH ON TUESDAY. ZONAL FLOW WILL
BE THE RULE UNTIL FRIDAY WHEN THE FLOW TURNS MORE SOUTHWEST AS A
TROUGH DIGS OVER THE MIDDLE PART OF THE COUNTRY.
SURFACE LOW PRESSURE IS OFF THE COAST BY SUNDAY NIGHT WITH UPSLOPE
FLOW OCCURRING OVER THE WESTERN RIDGES. IN ADDITION...THE GFS IS
HINTING AT SOME BANDING OVER NORTHEAST MD AGAIN ON THE BACKSIDE OF
THE LOW CENTER. THE UPSLOPE SNOW SHOWERS SHOULD CUT OFF EARLY ON
MONDAY AS HIGH PRESSURE BUILDS IN FROM THE SOUTH. A FROPA IS
EXPECTED ON TUESDAY. THE GFS IS STILL KEEPING MOST OF THE PRECIP
OVER THE WESTERN THIRD OF THE CWFA. HIGH PRESSURE ONCE AGAIN BUILDS
IN FROM THE SOUTH ON WEDNESDAY THROUGH THURSDAY. BY LATE FRIDAY INTO
SATURDAY...ANOTHER COLD FRONT IS EXPECTED. IN ADDITION...A COASTAL
LOW IS PROGGED TO DEVELOP OFF THE MID ATLANTIC COAST.
THE MOST ACTIVE PERIOD IN THE LONG TERM IS EXPECTED TO BE SUNDAY
NIGHT AS THE STRONG SHORTWAVE DIVES DOWN FROM CANADA. BOTH THE GFS
AND NAM ARE PROGGING GOOD QPF ALONG THE WESTERN RIDGES WITH THIS
SYSTEM. HAVE UPPED THE POPS TO LIKELY IN THIS AREA...WITH SNOWFALL
ACCUMULATIONS AROUND FOUR INCHES FOR SUNDAY NIGHT PROGGED BY BOTH
THE NAM AND GFS. IN ADDITION...THE GFS IS HINTING AT SOME BANDING OF
PRECIP OVER THE NE MARYLAND FOR OVERNIGHT SUNDAY. HAVE GONE AHEAD
AND PUT SOME HIGHER POPS/QPF IN THIS REGION. SINCE THE BANDING WILL
BE HARD TO NAIL DOWN...ESPECIALLY THIS FAR OUT...WILL ONLY ADD SOME
SLIGHTLY HIGHER QPF THAN PROGGED.
WINDS WILL ALSO BE GUSTY LATE SUNDAY NIGHT INTO MONDAY ON THE
BACKSIDE OF THE SURFACE LOW. BUFKIT SOUNDINGS KEEP THE GUSTS BLO
WIND ADVISORY CRITERIA FOR NOW...BUT MODELS CAN UNDERESTIMATE THE
WINDS.
PRETTY MUCH FOLLOWED GUIDANCE THROUGH SATURDAY. THIS DIDN`T CAUSE
MUCH OF A CHANGE FOR THE REMAINDER OF THE EXTENDED.
&&
.AVIATION...
SOUTHWESTERLY WINDS SLACKEN WITH SUNSET AS STRATO CU INVADES FROM
THE NORTH AND NORTHWEST...AND MID LEVEL MOISTURE ADVECTS IN FROM THE
SOUTHWEST. LEFT MENTION OF PRECIPITATION OUT OF TERMINALS AS
PROBABILITY OF MEASUREMENT AND VISIBILITY RESTRICTION IS LOW.
&&
.MARINE...
SMALL CRAFT ADVISORY IN EFFECT TODAY. OBSERVED WIND GUSTS IN THE
MOUNTAINS ARE BETWEEN 25-31KTS. OBSERVED WINDS BETWEEN
900-950MB ARE 25-30KTS ON THE 12Z KIAD RAOB AND MORNING ACARS
SOUNDINGS. EXPECT MOST OF THIS MOMENTUM WILL BE ABLE TO BREAK THE
MARINE INVERSION (WATER TEMPERATURES ARE 39F...AIR TEMPERATURES OVER
THE WATERS EXPECTED IN THE MID 40S). DEEPER MIXING IS EXPECTED TO
REACH THE NORTHERN BAY BEFORE SUNSET.
12Z ETA/MAV MOS AT THOMAS POINT INDICATE SUSTAINED WINDS SLACKEN TO
LESS THAN 10KT OVERNIGHT...BEFORE INCREASING TO 10-13KTS TOMORROW.
12Z NAM/GFS PROXIMITY BUFKIT FORECAST SOUNDINGS SHOW ADDITIONAL
MOMENTUM TRANSFER OF 18-20KTS POSSIBLE SUNDAY.
SMALL CRAFT CONDITIONS...MAINLY FOR GUSTS...WILL BE ONGOING FOR
SUNDAY NIGHT. AS THE GRADIENT TIGHTENS THE WIND SPEED AND GUSTS WILL
INCREASE RAPIDLY LATE SUNDAY NIGHT. A GALE WARNING WILL BE LIKELY
LATE SUNDAY NIGHT INTO MONDAY. SINCE THIS IS VERY LATE THIRD
PERIOD...WILL GO AHEAD AND HAVE HIGH END SCA GUSTS IN FOR THIS TIME
FRAME.
&&
.TIDES...
WATER LEVELS ARE CURRENTLY A HALF FOOT ABOVE ASTRONOMIC
PREDICTIONS. THE LUNAR CYCLE IS WAXING (70% FULL). WATER LEVELS
HAVE RECOVERED FROM A RECENT BLOWOUT.
THE CHESAPEAKE BAY OPERATIONAL FORECAST SYSTEM AND THE NOAA
EXTRATROPICAL STORM SURGE MODEL BOTH SUGGEST TIDAL DEPARTURES REMAIN
AT CURRENT DEPARTURES OR GRADUALLY RETURN TO ASTRONOMIC PREDICTIONS
THROUGH TONIGHT.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 5 PM EST THIS AFTERNOON FOR
ANZ530>537.
SMALL CRAFT ADVISORY FROM 9 AM SUNDAY TO 6 AM EST MONDAY FOR
ANZ530>537.
&&
$$
SHORT TERM/AVIATION/TIDES...ROGOWSKI
LONG TERM...LISTEMAA
MARINE...ROGOWSKI/LISTEMAA
AREA FORECAST DISCUSSION
NWS BALTIMORE MD/WASHINGTON DC
AFDLWX 945 AM EST SAT JAN 27 2007
.SHORT TERM...
WATER VAPOR LOOP SHOWS AN UPPER LOW LIFTING THROUGH THE PLAINS AS
THE SOUTHERN BRANCH JET PUNCHES INTO THE GULF STATES (WITH COPIOUS
MOISTURE ALOFT). THIS IS AHEAD OF THE NORTHERN STREAM WAVE DIGGING
INTO THE UPPER MIDWEST. A RIDGE IS OVER THE EASTERN CONUS. ACARS
400-250MB WIND OBSERVATIONS REVEAL SOUTHWESTERLY 100-120KT JET FROM
THE MIDWEST THROUGH NEW ENGLAND. A 120-160KT SOUTHWESTERLY JET
EXTENDED FROM MEXICO THROUGH THE GULF STATES. 11Z SURFACE ANALYSIS
PLACED A 990MB OCCLUDED CYCLONE ACROSS THE UPPER GREAT LAKES...WITH
THE OCCLUDED FRONTAL BOUNDARY STRETCHED SOUTHEAST TO NEAR
DETROIT...THEN SOUTHWEST AS A COLD FRONT THROUGH THE PLAINS. A
STATIONARY BOUNDARY EXTENDED EAST FROM THE TRIPLE POINT ACROSS
SOUTHERN NEW ENGLAND (WITH A 1014MB ARCTIC HIGH ACROSS QUEBEC). A
FRONTAL BOUNDARY WHICH DEVELOPED OVERNIGHT IS MOVING NORTHEAST AS A
WARM FRONT FROM ERIE PENNSYLVANIA SOUTHEAST TO NEAR
CHARLOTTESVILLE...THEN EAST ACROSS THE DELMARVA. A TROUGH WAS NOTED
IN THE LEE OF THE APPALACHIANS.
STRONG WARM ADVECTION (WELL ABOVE +15C) SUPPORTED WIDESPREAD STRATUS
GROWTH TO THE NORTH LAST NIGHT...WHICH BUILT SOUTH TO THE MARYLAND
BORDER AT DAY BREAK. WITH RELATIVELY WEAKER WARM ADVECTION FURTHER
SOUTH AND DIURNAL MIXING...DONT ANTICIPATE MUCH MORE SOUTHERLY
PROGRESS...AND IN FACT THE SOUTHERN FRINGE WILL LIKELY ERODE.
CUMULUS GROWTH WITH MIXING IS EXPECTED ALONG AND NORTH OF INTERSTATE
66 WHERE THE INVERSION IS MORE PRONOUNCED...WITH A SUNNY SKY
REMAINING ACROSS THE SOUTHERN ZONES.
MIXING WILL TRANSPORT WINDS OF 20-25 MPH TO THE SURFACE...WITH
BREEZY CONDITIONS EXPECTED IN HIGHER TERRAIN. TAPPING THE WARM
AIRMASS ALOFT WILL ALLOW TEMPERATURES TO SURPASS 50F...ESPECIALLY
ACROSS VIRGINIA.
&&
.AVIATION...
SOUTHWESTERLY WIND GUSTS WITH MIXING DURING THE MIDDAY. STRATUS WILL
LIKELY REMAIN NORTH OF THE METRO TERMINALS...HOWEVER SCATTERED
CUMULUS EXPECTED TO DEVELOP.
&&
.MARINE...
SMALL CRAFT ADVISORY IN EFFECT TODAY. OBSERVED WIND GUSTS IN THE
MOUNTAINS ARE BETWEEN 25-31KTS. OBSERVED WINDS BETWEEN
900-950MB ARE 25-30KTS ON THE 12Z KIAD RAOB AND MORNING ACARS
SOUNDINGS. EXPECT MOST OF THIS MOMENTUM WILL BE ABLE TO BREAK THE
MARINE INVERSION (WATER TEMPERATURES ARE 39F...AIR TEMPERATURES OVER
THE WATERS EXPECTED IN THE MID 40S).
00Z ETA/06Z MAV MOS AT THOMAS POINT INDICATE SUSTAINED WINDS BETWEEN
10-14KTS TODAY. 06Z NAM/GFS PROXIMITY AND 09Z 6KM LWX WRF-NMM MARINE
BUFKIT FORECAST SOUNDINGS SHOW ADDITIONAL MOMENTUM TRANSFER OF
18-24KTS FROM MIDDAY THROUGH THE AFTERNOON.
&&
.TIDES...
WATER LEVELS ARE CURRENTLY A HALF FOOT ABOVE ASTRONOMIC PREDICTIONS.
THE LUNAR CYCLE IS WAXING (67% FULL). WATER LEVELS HAVE RECOVERED
FROM A RECENT BLOWOUT.
THE CHESAPEAKE BAY OPERATIONAL FORECAST SYSTEM AND THE NOAA
EXTRATROPICAL STORM SURGE MODEL BOTH SUGGEST TIDAL DEPARTURES REMAIN
AT CURRENT DEPARTURES OR GRADUALLY RETURN TO ASTRONOMIC PREDICTIONS
THROUGH TONIGHT.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 10 AM TO 5 PM EST TODAY
FOR ANZ530>537.
&&
$$
SHORT TERM/AVIATION/MARINE/TIDES...ROGOWSKI
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
AFDCTP 1107 AM EST SAT JAN 27 2007
.SHORT TERM /REST OF TODAY/...
NOT A LOT TO REPORT THIS MORNING...A SOLID OVERCAST AND ONLY
SPOTTY LIGHT PRECIP AROUND THE AREA. THE WARM FRONT HAS MOVED THRU
MY WESTERN ZONES...BUT LIGHT WINDS AND CHILLY TEMPS REMAIN OVER
THE SUSQ VALLEY WHERE COLD AIR DAMMING IS HANGING TOUGH. WE WILL
STAY VULNERABLE TO PRECIP INTO TONIGHT AS WE REMAIN UNDER THE
INFLUENCE OF MOIST CYCLONIC FLOW. NOT MUCH WILL CHANGE UNTIL LATER
TOMORROW AND TOMORROW NIGHT WHEN A RENEWED SURGE OF ARCTIC AIR
HEADS OUR WAY IN THE WAKE OF A DEVELOPING STORM THAT WILL MOVE
WELL OFF THE EASTERN SEABOARD.
LA CORTE
&&
.PREV DISCUSSION...
/ISSUED 715 AM EST SAT JAN 27 2007/
AVIATION /12Z-12Z/...
MVFR/VFR SC HAS OVERSPREAD ALL BUT XTRM SRN PA THIS MORNING AS SFC
LOW CONTINUES TO SLIDE ESEWD TOWARD WRN NY STATE. WARM FRONT STILL
WAVERING ACROSS ECENT PA WITH CLD FNT INTO NW OH. WDLY SCT -RA OR
-SN SHRA PSBL LATE AM THRU THIS AFT ALTHOUGH PROBS A BIT TO LOW
AND MSTR IS QUITE LIMITED SO ONLY INCLUDED VCSH ACROSS THE CENTRAL
SITES WITH TEMPO FOR -FZDZSN AT KBFD EARLY/MID AM. AS WARM FRONT
LIFTS NEWD...WELL-MIXED BLYR WILL SUPPORT WSWRLY SFC WND GUSTS
20-25KTS.
PREV DISCUSSION...
/ISSUED 400 AM EST SAT JAN 27 2007/
SHORT TERM /TODAY THROUGH MONDAY/...
SFC WARM FRONT PUSHING INTO WESTERN PENN EARLY THIS MORNING WAS
HELPING TO PRODUCE AN EXTENSIVE AREA OF STRATO CU CLOUDS ACROSS NRN
AND EASTERN PENN...EXTENDING BACK ACROSS NRN OHIO AND THE UPPER
GLAKES.
NO PRECIP ECHOES SEEN WITH THIS RELATIVELY SHALLOW AND WARM CLOUD
DECK...AND I EXPECT JUST SOME PATCHY FREEZING DRIZZLE POSSIBLE
ACROSS THE ALLEGHENY PLATEAU WHERE WE`LL SEE THE COMBINED EFFECT OF
ISENT LIFT IN THE 280-290K THETA RIBBON...AND OROGRAPHIC LIFT VIA
THE BOUNDARY LAYER SOUTHWESTERLY FLOW BENEATH THE NOSE OF A 50-55KT
LLVL JET.
AS THIS LLVL LIFT SHIFT TO THE EAST THIS MORNING...THE CLOUDS WILL
CONTINUE TO OVERSPREAD THE REST OF THE SOUTHERN PENN
COUNTIES...WHICH ARE CURRENTLY CLEAR TO PARTLY CLOUDY.
THIS WILL BE THE MILDEST DAY (5-7F ABOVE NORMAL) WE`LL SEE OVER THE
UPCOMING WEEK WITH AFTERNOON TEMPS BEHIND THE WARM FRONT REACHING
THE M/U 30S ACROSS THE CENTRAL AND NRN MTNS...AND 40 TO 45 ACROSS
OUR SE ZONES.
ANY BREAKS IN THE CLOUD COVER WILL OCCUR MAINLY ACROSS THE FAR SCENT
ZONES AND LOWER SUSQ VALLEY WHERE THE CURRENT LIGHT AND VARIABLE
WIND WILL VEER TO AND INCREASE TO A 10 TO 15 KT DOWNSLOPE...WEST
NORTHWEST COMPONENT BY LATE TODAY.
A SFC COLD FRONT...TRAILING SOUTHWARD FROM THE LOW PRESS CENTER
TRACKING EAST ACROSS NEW YORK TODAY...WILL CROSS THE REGION THIS
AFTERNOON. GRADUALLY COLDER BOUNDARY LAYER AIR WILL ADVECT EAST AND
CHANGE ANY VERY LIGHT MIXED PRECIP OR FZDZ TO SCATTERED SNOW SHOWERS
ACROSS THE WRN MTNS BY DUSK.
FLAT SOUTHERN STREAM SHORT WAVE WILL STREAK EAST ACROSS THE CENTRAL
APPALACHIANS TONIGHT...PUSHING SOME LIGHT PRECIP NORTH TOWARD THE
MASON/DIXON LINE. 21Z SREF 6-HR POPS FOR LIGHT QPF SHOWS ONLY A 20
PERCENT CHC FOR UP TO 0.05 OF AN INCH ACROSS THE LOWER SUSQ VALLEY
TONIGHT...SO OUR CURRENT CHC FOR LIGHT SNOW/RAIN LOOKS GOOD FOR THAT
AREA. A RELATIVE MIN IN PRECIP WILL OCCUR ACROSS THE CENTRAL
ZONES...WITH SNOW SHOWERS BECOMING MORE NUMEROUS ACROSS NWRN PENN
LATE TONIGHT AND SUNDAY AHEAD OF THE NEXT RATHER
IMPRESSIVE...DIGGING NRN STREAM SHORT WAVE.
THIS UPPER TROUGH AMPLIFIES SIGNIFICANTLY SUNDAY/SUNDAY NIGHT AS IT
MOVES ACROSS PENN. A POCKET OF VERY COLD MID/UPPER LEVEL TEMPS /-24C
AT 700 HPA...AND -39C AT 500 HPA/ WILL ACCOMPANY THE PASSAGE OF
ANOTHER ARCTIC FRONT. THIS WILL LEAD TO NUMEROUS SNOW SHOWERS ACROSS
MOST OF THE FCST AREA WITH THE CHC FOR A FEW HOUR PERIOD OF
STEADY...MODERATE SNOW MAINLY ACROSS THE NRN HALF OF THE STATE WHERE
1-2 INCHES LOOKS LIKE A PROBABLE AMOUNT
MUCH COLDER AIR WITH TEMPS IN THE TEENS NW...TO LOWER AND MID 20S
ACROSS THE SUSQ VALLEY...WILL FOLLOW FOR MONDAY...SIMILAR TO WHAT WE
EXPERIENCED THIS PAST THURSDAY. NUMEROUS MTN SNOW SHOWERS AND
LOCALLY HEAVY LAKE EFFECT SNOW WILL FALL ACROSS THE NW ZONES...WITH
SCATTERED SNOW SHOWERS AND SQUALLS ELSEWHERE.
LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
COLD...MAINLY DRY CONDITIONS UNDER A PERSISTENT WEST TO NW FLOW
ALOFT WILL OCCUR FOR THE MID TO LATE PART OF THE UPCOMING WEEK WITH
SCATTERED MAINLY MTN SNOW SHOWERS...ENHANCED AT TIMES BY THE PASSAGE
OF A FEW...RELATIVELY WEAK NRN STREAM TROUGHS.
AVIATION /09Z-06Z/...
WARM FRONT MAKING SLOW NEWD PROGRESS EARLY THIS MORNING JUST NORTH
OF A DUJ-FIG-UNV LINE. XPECT MVFR CIGS TO PERSIST AT KBFD WITH VFR
CONDS ELSEWHERE THRU THE PREDAWN HOURS. SOME LLVL MIXING EVIDENT IN
THE WARM SECTOR ACROSS THE SWRN HALF OF PA WITH OCNL SFC WND GUSTS
TO 20-30KTS. THIS TREND SHOULD HOLD IN ADVANCE OF A SFC CLD FNT MOVG
EWD ACROSS THE LWR GRT LKS.
MID LVL DRYING AND NO ICE INTRODUCTION ALOFT WILL ALLOW FOR
SUPERCOOLED WATER TO FORM WITHIN THE CLOUD LAYER /AOB 5KFT/ AT KBFD
WITH PATCHY -FZDZ PSBL. IN ADDITION...AIRCRAFT FLYING THROUGH THIS
AREA MAY ENCOUNTER LGT TO MOD RM IC.
THE MAIN AVIATION WX CONCERN TAKES PLACE AFT 12Z AS A SFC LOW
PRESSURE SYS MOVES ESE ACROSS THE CENTRAL GRT LKS AND INTO UPSTATE
NY BY THE AFTERNOON...DRAGGING THE AFOREMENTIONED CLD FRONT ALONG
WITH IT. LOW CLOUDS MAKING THEIR WAY ACROSS LAKE ERIE WILL SPILL
SOUTH AND EAST DURING THE MORNING HOURS AS THE COLD FNT MAKES ITS
WAY INTO W-CENT PA AROUND MIDDAY. WITH LIMITED MOISTURE...PCPN
SHOULD BE LIGHT AND SCT IN NATURE. GUSTY PRE-FRONTAL WSWERLY FLOW IN
THE WARM SECTOR SHOULD LEAD TO RISING TEMPS AND THUS SCT -RA OR -SN
SHRA ACROSS ALL SITES EXCEPT KBFD...WHERE PCPN SHOULD REMAIN FROZEN.
(MAINLY DRY) FROPA/WIND SHIFT SLATED TO OCCUR BTWN 18-23Z WITH CAA
CHANGING ANY LINGERING PCPN TO -SNSH. XPECT LOW END VFR/HIGH END
MVFR CONDS TO PREVAIL WITH IFR VIS PSBL AT KBFD. NWERLY BLYR FLOW
BEHIND THE CLD FRONT WILL BRING LE/OROGRAPHIC -SHSN BACK INTO PLAY
AFT 00Z ACROSS THE WRN MTNS.
LASTLY...A FAIRLY STRONG WRLY LLJ /50-60KTS AROUND 5KFT AGL/ WILL
ALLOW FOR A BRIEF PD OF LLWS THRU 15Z OR SO ACROSS THE
WESTERN/CENTRAL AIRFIELDS AS THE NOCTURNAL INVERSION MIXES OUT BY
THE LATE MORNING/EARLY AFTERNOON.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...
AREA FORECAST DISCUSSION...UPDATED
NWS STATE COLLEGE PA
AFDCTP 715 AM EST SAT JAN 27 2007
.AVIATION /12Z-12Z/...
MVFR/VFR SC HAS OVERSPREAD ALL BUT XTRM SRN PA THIS MORNING AS SFC
LOW CONTINUES TO SLIDE ESEWD TOWARD WRN NY STATE. WARM FRONT STILL
WAVERING ACROSS ECENT PA WITH CLD FNT INTO NW OH. WDLY SCT -RA OR
-SN SHRA PSBL LATE AM THRU THIS AFT ALTHOUGH PROBS A BIT TO LOW
AND MSTR IS QUITE LIMITED SO ONLY INCLUDED VCSH ACROSS THE CENTRAL
SITES WITH TEMPO FOR -FZDZSN AT KBFD EARLY/MID AM. AS WARM FRONT
LIFTS NEWD...WELL-MIXED BLYR WILL SUPPORT WSWRLY SFC WND GUSTS
20-25KTS.
&&
.PREV DISCUSSION...
/ISSUED 400 AM EST SAT JAN 27 2007/
SHORT TERM /TODAY THROUGH MONDAY/...
SFC WARM FRONT PUSHING INTO WESTERN PENN EARLY THIS MORNING WAS
HELPING TO PRODUCE AN EXTENSIVE AREA OF STRATO CU CLOUDS ACROSS NRN
AND EASTERN PENN...EXTENDING BACK ACROSS NRN OHIO AND THE UPPER
GLAKES.
NO PRECIP ECHOES SEEN WITH THIS RELATIVELY SHALLOW AND WARM CLOUD
DECK...AND I EXPECT JUST SOME PATCHY FREEZING DRIZZLE POSSIBLE
ACROSS THE ALLEGHENY PLATEAU WHERE WE`LL SEE THE COMBINED EFFECT OF
ISENT LIFT IN THE 280-290K THETA RIBBON...AND OROGRAPHIC LIFT VIA
THE BOUNDARY LAYER SOUTHWESTERLY FLOW BENEATH THE NOSE OF A 50-55KT
LLVL JET.
AS THIS LLVL LIFT SHIFT TO THE EAST THIS MORNING...THE CLOUDS WILL
CONTINUE TO OVERSPREAD THE REST OF THE SOUTHERN PENN
COUNTIES...WHICH ARE CURRENTLY CLEAR TO PARTLY CLOUDY.
THIS WILL BE THE MILDEST DAY (5-7F ABOVE NORMAL) WE`LL SEE OVER THE
UPCOMING WEEK WITH AFTERNOON TEMPS BEHIND THE WARM FRONT REACHING
THE M/U 30S ACROSS THE CENTRAL AND NRN MTNS...AND 40 TO 45 ACROSS
OUR SE ZONES.
ANY BREAKS IN THE CLOUD COVER WILL OCCUR MAINLY ACROSS THE FAR SCENT
ZONES AND LOWER SUSQ VALLEY WHERE THE CURRENT LIGHT AND VARIABLE
WIND WILL VEER TO AND INCREASE TO A 10 TO 15 KT DOWNSLOPE...WEST
NORTHWEST COMPONENT BY LATE TODAY.
A SFC COLD FRONT...TRAILING SOUTHWARD FROM THE LOW PRESS CENTER
TRACKING EAST ACROSS NEW YORK TODAY...WILL CROSS THE REGION THIS
AFTERNOON. GRADUALLY COLDER BOUNDARY LAYER AIR WILL ADVECT EAST AND
CHANGE ANY VERY LIGHT MIXED PRECIP OR FZDZ TO SCATTERED SNOW SHOWERS
ACROSS THE WRN MTNS BY DUSK.
FLAT SOUTHERN STREAM SHORT WAVE WILL STREAK EAST ACROSS THE CENTRAL
APPALACHIANS TONIGHT...PUSHING SOME LIGHT PRECIP NORTH TOWARD THE
MASON/DIXON LINE. 21Z SREF 6-HR POPS FOR LIGHT QPF SHOWS ONLY A 20
PERCENT CHC FOR UP TO 0.05 OF AN INCH ACROSS THE LOWER SUSQ VALLEY
TONIGHT...SO OUR CURRENT CHC FOR LIGHT SNOW/RAIN LOOKS GOOD FOR THAT
AREA. A RELATIVE MIN IN PRECIP WILL OCCUR ACROSS THE CENTRAL
ZONES...WITH SNOW SHOWERS BECOMING MORE NUMEROUS ACROSS NWRN PENN
LATE TONIGHT AND SUNDAY AHEAD OF THE NEXT RATHER
IMPRESSIVE...DIGGING NRN STREAM SHORT WAVE.
THIS UPPER TROUGH AMPLIFIES SIGNIFICANTLY SUNDAY/SUNDAY NIGHT AS IT
MOVES ACROSS PENN. A POCKET OF VERY COLD MID/UPPER LEVEL TEMPS /-24C
AT 700 HPA...AND -39C AT 500 HPA/ WILL ACCOMPANY THE PASSAGE OF
ANOTHER ARCTIC FRONT. THIS WILL LEAD TO NUMEROUS SNOW SHOWERS ACROSS
MOST OF THE FCST AREA WITH THE CHC FOR A FEW HOUR PERIOD OF
STEADY...MODERATE SNOW MAINLY ACROSS THE NRN HALF OF THE STATE WHERE
1-2 INCHES LOOKS LIKE A PROBABLE AMOUNT
MUCH COLDER AIR WITH TEMPS IN THE TEENS NW...TO LOWER AND MID 20S
ACROSS THE SUSQ VALLEY...WILL FOLLOW FOR MONDAY...SIMILAR TO WHAT WE
EXPERIENCED THIS PAST THURSDAY. NUMEROUS MTN SNOW SHOWERS AND
LOCALLY HEAVY LAKE EFFECT SNOW WILL FALL ACROSS THE NW ZONES...WITH
SCATTERED SNOW SHOWERS AND SQUALLS ELSEWHERE.
LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
COLD...MAINLY DRY CONDITIONS UNDER A PERSISTENT WEST TO NW FLOW
ALOFT WILL OCCUR FOR THE MID TO LATE PART OF THE UPCOMING WEEK WITH
SCATTERED MAINLY MTN SNOW SHOWERS...ENHANCED AT TIMES BY THE PASSAGE
OF A FEW...RELATIVELY WEAK NRN STREAM TROUGHS.
AVIATION /09Z-06Z/...
WARM FRONT MAKING SLOW NEWD PROGRESS EARLY THIS MORNING JUST NORTH
OF A DUJ-FIG-UNV LINE. XPECT MVFR CIGS TO PERSIST AT KBFD WITH VFR
CONDS ELSEWHERE THRU THE PREDAWN HOURS. SOME LLVL MIXING EVIDENT IN
THE WARM SECTOR ACROSS THE SWRN HALF OF PA WITH OCNL SFC WND GUSTS
TO 20-30KTS. THIS TREND SHOULD HOLD IN ADVANCE OF A SFC CLD FNT MOVG
EWD ACROSS THE LWR GRT LKS.
MID LVL DRYING AND NO ICE INTRODUCTION ALOFT WILL ALLOW FOR
SUPERCOOLED WATER TO FORM WITHIN THE CLOUD LAYER /AOB 5KFT/ AT KBFD
WITH PATCHY -FZDZ PSBL. IN ADDITION...AIRCRAFT FLYING THROUGH THIS
AREA MAY ENCOUNTER LGT TO MOD RM IC.
THE MAIN AVIATION WX CONCERN TAKES PLACE AFT 12Z AS A SFC LOW
PRESSURE SYS MOVES ESE ACROSS THE CENTRAL GRT LKS AND INTO UPSTATE
NY BY THE AFTERNOON...DRAGGING THE AFOREMENTIONED CLD FRONT ALONG
WITH IT. LOW CLOUDS MAKING THEIR WAY ACROSS LAKE ERIE WILL SPILL
SOUTH AND EAST DURING THE MORNING HOURS AS THE COLD FNT MAKES ITS
WAY INTO W-CENT PA AROUND MIDDAY. WITH LIMITED MOISTURE...PCPN
SHOULD BE LIGHT AND SCT IN NATURE. GUSTY PRE-FRONTAL WSWERLY FLOW IN
THE WARM SECTOR SHOULD LEAD TO RISING TEMPS AND THUS SCT -RA OR -SN
SHRA ACROSS ALL SITES EXCEPT KBFD...WHERE PCPN SHOULD REMAIN FROZEN.
(MAINLY DRY) FROPA/WIND SHIFT SLATED TO OCCUR BTWN 18-23Z WITH CAA
CHANGING ANY LINGERING PCPN TO -SNSH. XPECT LOW END VFR/HIGH END
MVFR CONDS TO PREVAIL WITH IFR VIS PSBL AT KBFD. NWERLY BLYR FLOW
BEHIND THE CLD FRONT WILL BRING LE/OROGRAPHIC -SHSN BACK INTO PLAY
AFT 00Z ACROSS THE WRN MTNS.
LASTLY...A FAIRLY STRONG WRLY LLJ /50-60KTS AROUND 5KFT AGL/ WILL
ALLOW FOR A BRIEF PD OF LLWS THRU 15Z OR SO ACROSS THE
WESTERN/CENTRAL AIRFIELDS AS THE NOCTURNAL INVERSION MIXES OUT BY
THE LATE MORNING/EARLY AFTERNOON.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
AVIATION...STEINBUGL
AREA FORECAST DISCUSSION
NWS STATE COLLEGE PA
AFDCTP 400 AM EST SAT JAN 27 2007
.SHORT TERM /TODAY THROUGH MONDAY/...
SFC WARM FRONT PUSHING INTO WESTERN PENN EARLY THIS MORNING WAS
HELPING TO PRODUCE AN EXTENSIVE AREA OF STRATO CU CLOUDS ACROSS NRN
AND EASTERN PENN...EXTENDING BACK ACROSS NRN OHIO AND THE UPPER
GLAKES.
NO PRECIP ECHOES SEEN WITH THIS RELATIVELY SHALLOW AND WARM CLOUD
DECK...AND I EXPECT JUST SOME PATCHY FREEZING DRIZZLE POSSIBLE
ACROSS THE ALLEGHENY PLATEAU WHERE WE`LL SEE THE COMBINED EFFECT OF
ISENT LIFT IN THE 280-290K THETA RIBBON...AND OROGRAPHIC LIFT VIA
THE BOUNDARY LAYER SOUTHWESTERLY FLOW BENEATH THE NOSE OF A 50-55KT
LLVL JET.
AS THIS LLVL LIFT SHIFT TO THE EAST THIS MORNING...THE CLOUDS WILL
CONTINUE TO OVERSPREAD THE REST OF THE SOUTHERN PENN
COUNTIES...WHICH ARE CURRENTLY CLEAR TO PARTLY CLOUDY.
THIS WILL BE THE MILDEST DAY (5-7F ABOVE NORMAL) WE`LL SEE OVER THE
UPCOMING WEEK WITH AFTERNOON TEMPS BEHIND THE WARM FRONT REACHING
THE M/U 30S ACROSS THE CENTRAL AND NRN MTNS...AND 40 TO 45 ACROSS
OUR SE ZONES.
ANY BREAKS IN THE CLOUD COVER WILL OCCUR MAINLY ACROSS THE FAR SCENT
ZONES AND LOWER SUSQ VALLEY WHERE THE CURRENT LIGHT AND VARIABLE
WIND WILL VEER TO AND INCREASE TO A 10 TO 15 KT DOWNSLOPE...WEST
NORTHWEST COMPONENT BY LATE TODAY.
A SFC COLD FRONT...TRAILING SOUTHWARD FROM THE LOW PRESS CENTER
TRACKING EAST ACROSS NEW YORK TODAY...WILL CROSS THE REGION THIS
AFTERNOON. GRADUALLY COLDER BOUNDARY LAYER AIR WILL ADVECT EAST AND
CHANGE ANY VERY LIGHT MIXED PRECIP OR FZDZ TO SCATTERED SNOW SHOWERS
ACROSS THE WRN MTNS BY DUSK.
FLAT SOUTHERN STREAM SHORT WAVE WILL STREAK EAST ACROSS THE CENTRAL
APPALACHIANS TONIGHT...PUSHING SOME LIGHT PRECIP NORTH TOWARD THE
MASON/DIXON LINE. 21Z SREF 6-HR POPS FOR LIGHT QPF SHOWS ONLY A 20
PERCENT CHC FOR UP TO 0.05 OF AN INCH ACROSS THE LOWER SUSQ VALLEY
TONIGHT...SO OUR CURRENT CHC FOR LIGHT SNOW/RAIN LOOKS GOOD FOR THAT
AREA. A RELATIVE MIN IN PRECIP WILL OCCUR ACROSS THE CENTRAL
ZONES...WITH SNOW SHOWERS BECOMING MORE NUMEROUS ACROSS NWRN PENN
LATE TONIGHT AND SUNDAY AHEAD OF THE NEXT RATHER
IMPRESSIVE...DIGGING NRN STREAM SHORT WAVE.
THIS UPPER TROUGH AMPLIFIES SIGNIFICANTLY SUNDAY/SUNDAY NIGHT AS IT
MOVES ACROSS PENN. A POCKET OF VERY COLD MID/UPPER LEVEL TEMPS /-24C
AT 700 HPA...AND -39C AT 500 HPA/ WILL ACCOMPANY THE PASSAGE OF
ANOTHER ARCTIC FRONT. THIS WILL LEAD TO NUMEROUS SNOW SHOWERS ACROSS
MOST OF THE FCST AREA WITH THE CHC FOR A FEW HOUR PERIOD OF
STEADY...MODERATE SNOW MAINLY ACROSS THE NRN HALF OF THE STATE WHERE
1-2 INCHES LOOKS LIKE A PROBABLE AMOUNT
MUCH COLDER AIR WITH TEMPS IN THE TEENS NW...TO LOWER AND MID 20S
ACROSS THE SUSQ VALLEY...WILL FOLLOW FOR MONDAY...SIMILAR TO WHAT WE
EXPERIENCED THIS PAST THURSDAY. NUMEROUS MTN SNOW SHOWERS AND
LOCALLY HEAVY LAKE EFFECT SNOW WILL FALL ACROSS THE NW ZONES...WITH
SCATTERED SNOW SHOWERS AND SQUALLS ELSEWHERE.
&&
.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
COLD...MAINLY DRY CONDITIONS UNDER A PERSISTENT WEST TO NW FLOW
ALOFT WILL OCCUR FOR THE MID TO LATE PART OF THE UPCOMING WEEK WITH
SCATTERED MAINLY MTN SNOW SHOWERS...ENHANCED AT TIMES BY THE PASSAGE
OF A FEW...RELATIVELY WEAK NRN STREAM TROUGHS.
&&
.AVIATION /09Z-06Z/...
WARM FRONT MAKING SLOW NEWD PROGRESS EARLY THIS MORNING JUST NORTH
OF A DUJ-FIG-UNV LINE. XPECT MVFR CIGS TO PERSIST AT KBFD WITH VFR
CONDS ELSEWHERE THRU THE PREDAWN HOURS. SOME LLVL MIXING EVIDENT IN
THE WARM SECTOR ACROSS THE SWRN HALF OF PA WITH OCNL SFC WND GUSTS
TO 20-30KTS. THIS TREND SHOULD HOLD IN ADVANCE OF A SFC CLD FNT MOVG
EWD ACROSS THE LWR GRT LKS.
MID LVL DRYING AND NO ICE INTRODUCTION ALOFT WILL ALLOW FOR
SUPERCOOLED WATER TO FORM WITHIN THE CLOUD LAYER /AOB 5KFT/ AT KBFD
WITH PATCHY -FZDZ PSBL. IN ADDITION...AIRCRAFT FLYING THROUGH THIS
AREA MAY ENCOUNTER LGT TO MOD RM IC.
THE MAIN AVIATION WX CONCERN TAKES PLACE AFT 12Z AS A SFC LOW
PRESSURE SYS MOVES ESE ACROSS THE CENTRAL GRT LKS AND INTO UPSTATE
NY BY THE AFTERNOON...DRAGGING THE AFOREMENTIONED CLD FRONT ALONG
WITH IT. LOW CLOUDS MAKING THEIR WAY ACROSS LAKE ERIE WILL SPILL
SOUTH AND EAST DURING THE MORNING HOURS AS THE COLD FNT MAKES ITS
WAY INTO W-CENT PA AROUND MIDDAY. WITH LIMITED MOISTURE...PCPN
SHOULD BE LIGHT AND SCT IN NATURE. GUSTY PRE-FRONTAL WSWERLY FLOW IN
THE WARM SECTOR SHOULD LEAD TO RISING TEMPS AND THUS SCT -RA OR -SN
SHRA ACROSS ALL SITES EXCEPT KBFD...WHERE PCPN SHOULD REMAIN FROZEN.
(MAINLY DRY) FROPA/WIND SHIFT SLATED TO OCCUR BTWN 18-23Z WITH CAA
CHANGING ANY LINGERING PCPN TO -SNSH. XPECT LOW END VFR/HIGH END
MVFR CONDS TO PREVAIL WITH IFR VIS PSBL AT KBFD. NWERLY BLYR FLOW
BEHIND THE CLD FRONT WILL BRING LE/OROGRAPHIC -SHSN BACK INTO PLAY
AFT 00Z ACROSS THE WRN MTNS.
LASTLY...A FAIRLY STRONG WRLY LLJ /50-60KTS AROUND 5KFT AGL/ WILL
ALLOW FOR A BRIEF PD OF LLWS THRU 15Z OR SO ACROSS THE
WESTERN/CENTRAL AIRFIELDS AS THE NOCTURNAL INVERSION MIXES OUT BY
THE LATE MORNING/EARLY AFTERNOON.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&
$$
SHORT TERM...LAMBERT
LONG TERM...LAMBERT
AVIATION...STEINBUGL
AREA FORECAST DISCUSSION
NWS SEATTLE WA
AFDSEW 845 PM PST FRI JAN 26 2007
.SYNOPSIS...THE PACIFIC NORTHWEST WILL REMAIN UNDER A STRONG RIDGE
OF HIGH PRESSURE FOR THE NEXT WEEK. THE RIDGE WILL PRODUCE DRY
WEATHER...SUNSHINE...AND SLIGHTLY WARMER THAN NORMAL DAYTIME
TEMPERATURES.
&&
.SHORT TERM...SATELLITE IMAGERY SHOWS UPPER LEVEL RIDGE OVER
WASHINGTON AND BRITISH COLUMBIA WITH AN UPPER LEVEL LOW WEST OF
KSFO. OFFSHORE SURFACE GRADIENTS IN PLACE WITH KOTH-KSEA STILL BELOW
-4 MB. ACARS SOUNDINGS INTO KSEA AND KBFI SHOW A SHARP INVERSION HAS
ALREADY SET UP WITH THE TOP OF THE INVERSION NEAR 2500 FEET. ACARS
SOUNDINGS ALSO SHOW WINDS ALOFT UP TO THE INVERSION NORTHEASTERLY AT
10 TO 20 KNOTS. WITH THE OFFSHORE SURFACE GRADIENTS AND THE DRYING
NELY WINDS RIGHT OFF THE GROUND WOULD NOT EXPECT MUCH IN THE WAY OF
FOG FORMING SATURDAY MORNING. LITTLE CHANGE FOR SUNDAY AND MONDAY
WITH THE BLOCKED UPPER LEVEL PATTERN REMAINING IN PLACE AND THE LOW
LEVEL FLOW REMAINING OFFSHORE. FIRST LOOK AT THE 00Z RUNS INDICATING
OFFSHORE GRADIENTS A LITTLE STRONGER ON MONDAY WHICH COULD HELP WITH
THE POSSIBLE AIR STAGNATION PROBLEMS THE FIRST PART OF NEXT WEEK.
CURRENT FORECAST IN GOOD SHAPE TONIGHT. NO UPDATES. FELTON
.LONG TERM...PREVIOUS DISCUSSION FOLLOWS. EXTENDED MODELS IN FAIRLY
GOOD AGREEMENT WITH HIGH AMPLITUDE UPPER LEVEL RIDGE IN PLACE OVER
THE EASTERN PACIFIC THROUGH THE EXTENDED PERIOD. OFFSHORE SURFACE
GRADIENTS SLOWLY WEAKEN TUESDAY AND WEDNESDAY WITH THE SURFACE
GRADIENTS BECOMING FLAT LATE IN THE WEEK. GFS TRYING TO BRING A
SYSTEM THROUGH THE RIDGE BUT THE MODEL IS TRENDING WEAKER WITH THIS
FEATURE WITH IN THE LAST COUPLE OF RUNS. WILL STAY WITH THE SUNNY
FORECAST WITH JUST SOME PATCHY MORNING FOG THROUGH NEXT FRIDAY.
FELTON
&&
.AVIATION...SKIES WILL REMAIN CLEAR OVERNIGHT WITH ONLY PATCHY FOG
DEVELOPING IN THE MOST FOG PRONE AREAS...IE KOLM. THE LIGHT TO
MODERATE BREEZY OCCURRING IN MANY LOCATIONS WILL CONTINUE TO DIE OFF
OVERNIGHT AS GRADIENTS WEAKEN AND A RADIATIONAL COOLING STRENGTHENS
UP THE LOW LEVEL INVERSION.
KSEA...NOT EXPECTING FOG TO AFFECT THE AIRPORT THROUGH SATURDAY. NLY
WIND 5-9 KT SHOULD EASE UP A BIT AND COME AROUND MORE EASTERLY
THROUGH THE NIGHT. CERNIGLIA
&&
.SEW WATCHES/WARNINGS/ADVISORIES...
.SMALL CRAFT ADVISORY COAST...WEST ENTRANCE.
$$