AREA FORECAST DISCUSSION
NWS BALTIMORE MD/WASHINGTON DC
AFDLWX 930 PM EST WED JAN 21 2004
UPDATE...SKIES CURR CLEAR ACROSS ENTIRE AREA EXCEPT FAR W. THIS HAS
ALLOWED FOR EXCELLENT RADIATIONAL CONDITIONS AND AS RESULT TEMPS
HAVE FALLEN QUICKLY. DOWN TO 17 AT MRB AND 16F HERE AT WFO LWX.
THINK LOWS WILL BE REACHED PRIOR TO MIDNIGHT THEN LEVEL OFF OR EVEN
SLIGHTLY RISE THEREAFTER AS CLOUDS INCREASE AND THICKEN TOWARD
MORNING. HAD TO LOWER MINT AS CURR READINGS ALREADY LOWER THAN CURR
FCST IN SOME SPOTS BUT NOT EXPECTING TO DROP TOO MUCH FROM WHAT THEY
ARE RIGHT NOW. AS FOR ANY SNOW WITH THIS CLIPPER SYSTEM BEST CHANCE
LOOKS TO BE TOMORROW MAINLY COUNTIES ADJACENT TO THE PA BORDER.
THEREFORE WILL CONTINUE WITH A DRY FCST FOR TONIGHT.
18Z GFS HAS TRENDED MUCH COLDER WITH SUNDAYS STORM SYSTEM PUMPING
OUT MORE THAN SEVEN INS OF SNOW HERE AT DC. HOWEVER THIS MODEL HAS
BEEN INCONSISTENT REGARDING WEEKEND FCST. SO DO NOT BUY ITS SOLUTION
ENTIRELY AT THIS POINT. WE ARE JUST GOING TO WAIT AND SEE UNTIL
MODELS COME INTO BETTER AGREEMENT.
ROSA
PREVIOUS AFD...
.SHORT TERM (TONIGHT THROUGH THURSDAY NIGHT):
WATER VAPOR LOOP SHOWS A WAVE DIVING INTO THE NORTHERN GREAT LAKES
FROM CENTRAL CANADA WITHIN NORTHERN STREAM OF EASTERN CONUS PHASED
FLOW. A CUTOFF UPPER LEVEL LOW IS LOCATED OVER SOUTHERN CALIFORNIA.
300MB ANALYSIS SHOWS A DOMINATE SOUTHERN STREAM JET FROM BAJA
CALIFORNIA NORTHEAST INTO THE SOUTHEAST CONUS AND NORTH THROUGH THE
WESTERN ATLANTIC (WITH A 170KT JET STREAK ACROSS THE SOUTHEAST
CONUS). THE OTHER JET OF INTEREST IS A 180KT JET LOCATED IN THE
NORTHERN STREAM OVER WESTERN CANADA. 12Z SURFACE ANALYSIS PLACES A
TROUGH OVER THE APPALACHIANS INDICATIVE OF LOWER LEVEL WARM
ADVECTION. 1026MB HIGH PRESSURE IS LOCATED FROM THE SOUTH CENTRAL
STATES NORTHEAST INTO THE OHIO VALLEY. A CLIPPER SYSTEM IS NEARING
THE UPPER GREAT LAKES REGION...WITH ITS ASSOCIATED WARM/STATIONARY
BOUNDARY ACROSS THE NORTHERN GREAT LAKES...AND A COLD FRONT CUTTING
THROUGH MINNESOTA.
KIAD AND REGIONAL ACARS SOUNDINGS SHOW STRONG WARM ADVECTION BETWEEN
750-900MB DURING THE PAST 24HRS. THIS IS SUPPORTING MIDLEVEL CLOUDS
WHICH WILL BE ACROSS THE REGION INTO TONIGHT. THEN EXPECT MIDLEVEL
WARM ADVECTION TO PASS TO THE NORTHEAST...WHILE LOW LEVEL WARM
ADVECTION SHOULD YIELD A LOWER CLOUD DECK DURING THE LATER OVERNIGHT
HOURS. GIVEN WARM ADVECTION IN THE 850-950MB LEVELS ADVERTISED BY
THE MODELS...EXPECT THE HIGHER TERRAIN TO SEE A SLIGHT TEMPERATURE
FALL EARLY TONIGHT...WITH MODERATING TEMPERATURES AFTER MIDNIGHT.
EXPECT TEMPERATURES TO FALL OVERNIGHT EAST OF THE MOUNTAINS TO ABOUT
20 DEGREES. WINDS WILL REMAIN LIGHT...BEFORE BECOMING SOUTHWEST AS
THE SURFACE RIDGE PASSES TO OUR EAST.
MODELS SHOW SIMILAR TIMING WITH THE COLD FRONT...AROUND NOON ACROSS
THE NORTHWEST FORECAST AREA...TO THE EARLY-MID AFTERNOON ACROSS THE
METRO AREAS...AND CLEARING THE SOUTHEAST FORECAST AREA BY EARLY
EVENING. EXPECT MAINLY CLOUDY SKIES WITH LOW LEVEL WARM ADVECTION
CLOUDS ACROSS THE MID ATLANTIC. TEMPERATURES WILL HAVE A CHANCE TO
JUMP INTO THE 40S EAST OF THE BLUE RIDGE...WHILE LITTLE TO NO
TEMPERATURE RISES ARE EXPECTED WITH THE QUICK FRONTAL PASSAGE ALONG
THE HIGHER TERRAIN. DEPENDING ON THE SPEED OF THE FRONT...A SHARP
TEMPERATURE FALL MAY OCCUR IN THE METRO AREA DURING THE MID TO LATE
AFTERNOON HOURS.
PRECIPITATION IS NOT MUCH OF A CONCERN THIS FAR SOUTHEAST WITH THE
FRONT...GIVEN THE RATHER WEAK CONVERGENCE AND LACK OF DEEPER LOW
LEVEL MOISTURE. AM HOWEVER THINKING SOME SNOW SHOWERS MAY BLEED OVER
THE RIDGES INTO OUR WESTERN AND NORTHERN FORECAST AREA...AS
THOSE AREAS FURTHER NORTHWEST AND WEST OF OUR FORECAST AREA WILL SEE
FAVORABLE UPSLOPE AND LAKE EFFECT MOISTURE FOR SEVERAL HOURS BEHIND
THE FRONT. COVERED WITH SLIGHT CHANCE POPS FOR NOW.
THE WINDS AND MUCH COLDER TEMPERATURES WILL BE THE MAIN STORY LATE
THURSDAY AND THURSDAY NIGHT...WITH WINDS BECOMING SUSTAINED AROUND
15 TO 20 MPH IN TIGHTENING PRESSURE GRADIENT. ETA BUFKIT SOUNDINGS
SHOW MOMENTUM TRANSFER OF NEARLY 40KTS...WHICH SHOULD YIELD 30 MPH
WIND GUSTS. THIS...WHEN COMBINED WITH COLD LOW TEMPERATURES THURSDAY
NIGHT SHOULD PRODUCE WIND CHILLS NEAR ZERO EAST OF THE BLUE
RIDGE...WHEREAS A WIND CHILL ADVISORY MAY BE NEEDED WEST OF THE BLUE
RIDGE WITH READINGS FROM 0 TO -10F IN THE CITY CENTERS AND -15 TO
-20F ACROSS THE HIGHEST TERRAIN. EXPECT CLOUDS TO QUICKLY ERODE IN
THE SHENANDOAH VALLEY EAST ACROSS LOWER SOUTHERN MARYLAND...WHILE
STATOCU WILL LIKELY PERSIST FROM THE MOUNTAINS EAST TO THE METRO
AREA (WITH STRONG NORTHWEST FLOW ADVECTING IN UPSLOPE MOISTURE).
WILL KEEP SLIGHT CHANCE POPS ALONG THE MOUNTAINS THURSDAY
NIGHT...BUT ANY SNOW SHOWERS WILL QUICKLY COME TO AN END GIVEN
INCREASED LOW LEVEL SHEAR AND BUILDING ANTICYCLONIC FLOW.
.MARINE: SMALL CRAFT CONDITIONS EXPECTED THURSDAY AFTERNOON AND
NIGHT BEHIND THE COLD FRONT.
ROGOWSKI
.LONG TERM(FRIDAY THROUGH WEDNESDAY)...
IT WILL BE VERY COLD FRIDAY MORNING WITH NORTHWEST FLOW ALOFT AND
HIGH PRESSURE BUILDING INTO THE AREA FROM THE GULF COAST STATES. H8
TEMPS WILL RANGE FROM -24 IN TH NORTHWEST TO -20 IN THE SOUTHERN
ZONES. EXPECT DAYTIME FROM THE MID 20S TO THE LOWER 30S.
FOR SATURDAY AND SUNDAY: THE WEEKEND STARTS OFF DRY BUT CLOUDS AND
MOISTURE INCREASE AS WARM AIR IS ADVECTED INTO THE AREA AHEAD OF AN
APPROACHING SOUTHERN STREAM SHORTWAVE. COLUMN WILL FINALLY BE MOIST
ENOUGH FOR PRECIP TO START REACHING THE GROUND LATE SATURDAY
NIGHT/EARLY SUNDAY. THE PRECIP WILL START OFF AS ALL SNOW AND CHANGE
TO RAIN IN THE SOUTH BY SUNDAY AFTERNOON.
THE SURFACE LOW IS PROGGED TO MOVE OFF THE EAST COAST MONDAY
MORNING...BUT WILL KEEP LOW END CHANCE POPS THROUGH EARLY MONDAY.
ALTHOUGH LATEST TRENDS SHOW MOST OF THE PRECIP SHOULD BE OUT OF THE
AREA BEFORE DAWN MONDAY. TEMPS WILL CONTINUE TO MODERATE FOR MONDAY
AND TUESDAY...WITH HIGHS REACHING THE 40S ACROSS THE SOUTHERN
TIER.
ANOTHER LOW PRESSURE SYSTEM WILL APPROACH ON WEDNESDAY. THIS WILL
BRING ANOTHER CHANCE FOR PRECIP TO THE AREA. /09
$$
.LWX...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.
AREA FORECAST DISCUSSION
NWS BALTIMORE MD/WASHINGTON DC
AFDLWX 310 PM EST WED JAN 21 2004
.SHORT TERM (TONIGHT THROUGH THURSDAY NIGHT):
WATER VAPOR LOOP SHOWS A WAVE DIVING INTO THE NORTHERN GREAT LAKES
FROM CENTRAL CANADA WITHIN NORTHERN STREAM OF EASTERN CONUS PHASED
FLOW. A CUTOFF UPPER LEVEL LOW IS LOCATED OVER SOUTHERN CALIFORNIA.
300MB ANALYSIS SHOWS A DOMINATE SOUTHERN STREAM JET FROM BAJA
CALIFORNIA NORTHEAST INTO THE SOUTHEAST CONUS AND NORTH THROUGH THE
WESTERN ATLANTIC (WITH A 170KT JET STREAK ACROSS THE SOUTHEAST
CONUS). THE OTHER JET OF INTEREST IS A 180KT JET LOCATED IN THE
NORTHERN STREAM OVER WESTERN CANADA. 12Z SURFACE ANALYSIS PLACES A
TROUGH OVER THE APPALACHIANS INDICATIVE OF LOWER LEVEL WARM
ADVECTION. 1026MB HIGH PRESSURE IS LOCATED FROM THE SOUTH CENTRAL
STATES NORTHEAST INTO THE OHIO VALLEY. A CLIPPER SYSTEM IS NEARING
THE UPPER GREAT LAKES REGION...WITH ITS ASSOCIATED WARM/STATIONARY
BOUNDARY ACROSS THE NORTHERN GREAT LAKES...AND A COLD FRONT CUTTING
THROUGH MINNESOTA.
KIAD AND REGIONAL ACARS SOUNDINGS SHOW STRONG WARM ADVECTION BETWEEN
750-900MB DURING THE PAST 24HRS. THIS IS SUPPORTING MIDLEVEL CLOUDS
WHICH WILL BE ACROSS THE REGION INTO TONIGHT. THEN EXPECT MIDLEVEL
WARM ADVECTION TO PASS TO THE NORTHEAST...WHILE LOW LEVEL WARM
ADVECTION SHOULD YIELD A LOWER CLOUD DECK DURING THE LATER OVERNIGHT
HOURS. GIVEN WARM ADVECTION IN THE 850-950MB LEVELS ADVERTISED BY
THE MODELS...EXPECT THE HIGHER TERRAIN TO SEE A SLIGHT TEMPERATURE
FALL EARLY TONIGHT...WITH MODERATING TEMPERATURES AFTER MIDNIGHT.
EXPECT TEMPERATURES TO FALL OVERNIGHT EAST OF THE MOUNTAINS TO ABOUT
20 DEGREES. WINDS WILL REMAIN LIGHT...BEFORE BECOMING SOUTHWEST AS
THE SURFACE RIDGE PASSES TO OUR EAST.
MODELS SHOW SIMILAR TIMING WITH THE COLD FRONT...AROUND NOON ACROSS
THE NORTHWEST FORECAST AREA...TO THE EARLY-MID AFTERNOON ACROSS THE
METRO AREAS...AND CLEARING THE SOUTHEAST FORECAST AREA BY EARLY
EVENING. EXPECT MAINLY CLOUDY SKIES WITH LOW LEVEL WARM ADVECTION
CLOUDS ACROSS THE MID ATLANTIC. TEMPERATURES WILL HAVE A CHANCE TO
JUMP INTO THE 40S EAST OF THE BLUE RIDGE...WHILE LITTLE TO NO
TEMPERATURE RISES ARE EXPECTED WITH THE QUICK FRONTAL PASSAGE ALONG
THE HIGHER TERRAIN. DEPENDING ON THE SPEED OF THE FRONT...A SHARP
TEMPERATURE FALL MAY OCCUR IN THE METRO AREA DURING THE MID TO LATE
AFTERNOON HOURS.
PRECIPITATION IS NOT MUCH OF A CONCERN THIS FAR SOUTHEAST WITH THE
FRONT...GIVEN THE RATHER WEAK CONVERGENCE AND LACK OF DEEPER LOW
LEVEL MOISTURE. AM HOWEVER THINKING SOME SNOW SHOWERS MAY BLEED OVER
THE RIDGES INTO OUR WESTERN AND NORTHERN FORECAST AREA...AS
THOSE AREAS FURTHER NORTHWEST AND WEST OF OUR FORECAST AREA WILL SEE
FAVORABLE UPSLOPE AND LAKE EFFECT MOISTURE FOR SEVERAL HOURS BEHIND
THE FRONT. COVERED WITH SLIGHT CHANCE POPS FOR NOW.
THE WINDS AND MUCH COLDER TEMPERATURES WILL BE THE MAIN STORY LATE
THURSDAY AND THURSDAY NIGHT...WITH WINDS BECOMING SUSTAINED AROUND
15 TO 20 MPH IN TIGHTENING PRESSURE GRADIENT. ETA BUFKIT SOUNDINGS
SHOW MOMENTUM TRANSFER OF NEARLY 40KTS...WHICH SHOULD YIELD 30 MPH
WIND GUSTS. THIS...WHEN COMBINED WITH COLD LOW TEMPERATURES THURSDAY
NIGHT SHOULD PRODUCE WIND CHILLS NEAR ZERO EAST OF THE BLUE
RIDGE...WHEREAS A WIND CHILL ADVISORY MAY BE NEEDED WEST OF THE BLUE
RIDGE WITH READINGS FROM 0 TO -10F IN THE CITY CENTERS AND -15 TO
-20F ACROSS THE HIGHEST TERRAIN. EXPECT CLOUDS TO QUICKLY ERODE IN
THE SHENANDOAH VALLEY EAST ACROSS LOWER SOUTHERN MARYLAND...WHILE
STATOCU WILL LIKELY PERSIST FROM THE MOUNTAINS EAST TO THE METRO
AREA (WITH STRONG NORTHWEST FLOW ADVECTING IN UPSLOPE MOISTURE).
WILL KEEP SLIGHT CHANCE POPS ALONG THE MOUNTAINS THURSDAY
NIGHT...BUT ANY SNOW SHOWERS WILL QUICKLY COME TO AN END GIVEN
INCREASED LOW LEVEL SHEAR AND BUILDING ANTICYCLONIC FLOW.
.MARINE: SMALL CRAFT CONDITIONS EXPECTED THURSDAY AFTERNOON AND
NIGHT BEHIND THE COLD FRONT.
ROGOWSKI
.LONG TERM(FRIDAY THROUGH WEDNESDAY)...
IT WILL BE VERY COLD FRIDAY MORNING WITH NORTHWEST FLOW ALOFT AND
HIGH PRESSURE BUILDING INTO THE AREA FROM THE GULF COAST STATES. H8
TEMPS WILL RANGE FROM -24 IN TH NORTHWEST TO -20 IN THE SOUTHERN
ZONES. EXPECT DAYTIME FROM THE MID 20S TO THE LOWER 30S.
FOR SATURDAY AND SUNDAY: THE WEEKEND STARTS OFF DRY BUT CLOUDS AND
MOISTURE INCREASE AS WARM AIR IS ADVECTED INTO THE AREA AHEAD OF AN
APPROACHING SOUTHERN STREAM SHORTWAVE. COLUMN WILL FINALLY BE MOIST
ENOUGH FOR PRECIP TO START REACHING THE GROUND LATE SATURDAY
NIGHT/EARLY SUNDAY. THE PRECIP WILL START OFF AS ALL SNOW AND CHANGE
TO RAIN IN THE SOUTH BY SUNDAY AFTERNOON.
THE SURFACE LOW IS PROGGED TO MOVE OFF THE EAST COAST MONDAY
MORNING...BUT WILL KEEP LOW END CHANCE POPS THROUGH EARLY MONDAY.
ALTHOUGH LATEST TRENDS SHOW MOST OF THE PRECIP SHOULD BE OUT OF THE
AREA BEFORE DAWN MONDAY. TEMPS WILL CONTINUE TO MODERATE FOR MONDAY
AND TUESDAY...WITH HIGHS REACHING THE 40S ACROSS THE SOUTHERN
TIER.
ANOTHER LOW PRESSURE SYSTEM WILL APPROACH ON WEDNESDAY. THIS WILL
BRING ANOTHER CHANCE FOR PRECIP TO THE AREA. /09
$$
.LWX...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.