AREA FORECAST DISCUSSION
NWS SAN DIEGO
AFDSAN 410 AM PST THU FEB 19 2004
.SYNOPSIS...CLOUDS AND LINGERING SHOWERS WILL DECREASE THIS MORNING
AS WEAK HIGH PRESSURE BRIEFLY BUILDS INTO SOUTHWEST CALIFORNIA. LOW
PRESSURE WILL DEVELOP ALONG THE CALIFORNIA COAST FRIDAY AND
STRENGTHEN DURING THE WEEKEND. SHOWERS MAY RETURN FRIDAY OR SATURDAY
WITH HEAVIER AND WIDESPREAD PRECIPITATION POSSIBLE BY SUNDAY...
DECREASING MONDAY. ANOTHER EXTENDED PERIOD OF PRECIPITATION...HEAVY
AT TIMES...IS POSSIBLE TUESDAY INTO THURSDAY OR FRIDAY.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES.
WED STORM SYSTEM IS NOW OVER ERN AZ AND CONTINUING TO MOVE EAST.
LINGERING "ISLAND EFFECT" SHOWERS IN SAN DIEGO COUNTY SHOULD DECR
QUICKLY THIS MORNING. THERE WL ALSO BE SOME RADIATION FOG IN THE
VLYS THIS MORNING. OTHERWISE...CLOUDS BANKED UP AGAINST THE COASTAL
SLOPES WL GRADUALLY CLR TODAY WITH OTHER AREAS SEEING QUITE A BIT OF
SUNSHINE. WIND ADVISORIES HAVE BEEN CANCELED AS SURFACE WINDS HAVE
DECREASED TO BLO ADV LVLS AND ACARS SOUNDINGS SHOW STEADILY DECRG
WINDS ALF.
HIGH CLOUDS WILL BEGIN TO THICKEN TONIGHT AND LOWER FRI. MESOETA
ALSO SHOWS A WK CSTL EDDY FOR LATE TONIGHT INTO FRI MORNING. SOME
SHOWERS...MAINLY OVR THE MTNS...ARE POSSIBLE FRI AND FRI NIGHT AS
MOIST CYCLONIC FLOW DEVELOPS ACROSS SRN CA AND BECOMES ENTRENCHED
THROUGH THE WEEKEND. MDLS CONTINUE TO DIFFER IN THE DETAILS WITH
EACH RUN...BUT IN GENERAL...IT LOOKS LIKE THOUGH THERE WL BE QUITE A
LOT OF CLOUD COVER FOR FRI THRU SAT...MOST PRECIPITATION AMOUNTS
SHOULD BE FAIRLY LIGHT AND NOT TOO WIDESPREAD.
FOR SAT NIGHT INTO SUN NIGHT...GFS AND ECWMF CONTINUE TO ADVERTISE
THE POTENTIAL FOR A PROLONGUED PD OF PRECIPITATION WITH MDT TO HVY
TOTALS POSSIBLE...ESPECIALLY SUNDAY. AS IN THE NR TERM...THERE
CONTINUE TO BE DIFFERENCES IN THE DETAILS WITH EACH RUN.
GFS/ECMWF SHOW SOME DRYING FOR MON NIGHT...WITH ANOTHER EXTENDED PD
OF PRECIPITATION ARRIVING TUE AND CONTINUING INTO THU OR FRI. MDT TO
HVY TOTALS ARE POSSIBLE DURG THIS PD.
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
HYDROLOGIC OUTLOOK (SPECIAL ISSUANCE)...................LAXESFSGX.
MARINE WEATHER STATEMENT (TIDAL OVERFLOW THRU FRIDAY)...LAXMWSSGX.
SPECIAL WEATHER STATEMENT...............................LAXSPSSGX.
&&
$$
XXX666
AREA FORECAST DISCUSSION
NWS CHICAGO IL
AFDCHI 545 AM CST THU FEB 19 2004
.AVIATION...
THE ACARS SOUNDING OUT OF RFD AT 0903 UTC SHOWS AN INVERSION UP TO
837 MB. THERE IS FOG AS WARM AIR OVERRUNS EXTREMELY SHALLOW COLD AIR
THIS MORNING. THE GFS MOS GUIDANCE SHOWS FORECAST OF VERY LOW
CEILINGS AFTER 03 UTC. THE INVERSION IS FORECAST AS SEEN ON THE
BUFKIT SOUNDINGS FROM THE ETA MODEL. THE WATER VAPOR LOOPS SHOW A
STRONG CIRCULATION MOVING INTO THE ARIZONA AND NEW MEXICO. LIGHTNING
RETURNS SHOW THE INSTABILITY PRESENT FAVORING CYCLONE DEVELOPMENT AS
A RESULT OF INCREASE VORTICITY. THIS IS USING THE ZO DEVELOPMENT
MODEL. THIS WILL INCREASE THE PRESSURE GRADIENT AND GIVE MODERATE
SOUTH WIND. THE WIND WILL BRING IN MORE MOISTURE INTO THE TAFS AND
HENCE THE LOW CEILINGS TONIGHT AND RAIN. THE ETA MODEL AND GFS MODEL
SHOW THE CYCLONE AND ITS DEVELOPMENT. WILL FORECAST CEILINGS AT 1000
FT AND PROBABILITY OF RAIN TONIGHT AFTER MIDNIGHT. THE NEXT SET OF
TAFS MAY HAVE RAIN AS EARLY AS MIDNIGHT. WITH THE STRONG WARM AIR
ADVECTION EXPECTED TONIGHT A DEEP LAYER OF AIR IS FORECAST TO BE
ABOVE FREEZING SO WILL NOT ADD FREEZING RAIN AT THIS TIME. WHW
&&
.DISCUSSION...
BROAD SCALE PATTERN APPEARS HEADED FOR WESTERN CANADIAN BLOCK NEXT
WEEK WHICH MEANS SPLIT FLOW THROUGH THE MID PART OF THE COUNTRY WITH
VARYING STRENGTH IN SRN STREAM. FOR GT LAKES ON FRONT END OF BLOCK
WE ARE VULNERABLE TO WEAK DISTURBANCES IN NW FLOW WHILE DEEPER
MOSITURE AND STRONGER SHORT WAVES TRAVERSE WELL TO THE S.
IN SHORT TERM..BEFORE ABOVE PATTERN SETS UP..SHORT WAVES MOVING
TOWARD 4-CORNERS THIS MORNING IS INITIATING SFC LOW OVER WESTERN
KANSAS. WITH OLD ARCTIC HIGH CAMPED OVER CNETRAL GULF RETURN OF
MOISTURE WILL BE SLOW AS 50 DEW PTS STILL ONLY ALONG S TX COAST. SFC
LOW FORECAST TO TRACK TOWARD CHI PASSING OVER OR PERHAPS JUST N OF
CITY FRI AFTERNOON. THIS WILL INSURE A RAIN EVENT. BEST FORCING WILL
BE WELL N IN WISC SO RAIN FOR NRN IL MAY ARRIVE IN TWO
BATCHES...FIRST WITH SOME WARM ADVECTION LATE TONIGHT OR EARLY FRI
THEN ASSOCIATED WITH CENTER OR TRAILING FRONT DURING THE AFTERNOON.
BRIEF BACKWASH SHOWERS FRI NIGHT WILL END BY SAT MORNING. SOME
CHANGE TO SNOW POSSBILE A TAIL END OF PRECIP MOSTLY TOWARD RFD AREA.
AIRMASS BEHIND SYSTEM NOT VERY COLD SO TEMPS SETTLING TO NEAR
SEASONAL LEVELS LIKELY OVER THE WEEKEND BEFORE NEXT SYSTEM
APPROACHES FROM NW. THIS ONE WILL RELY ON WARM ADVECTION/ISENTROPICS
FOR CLOUDS AND LIGHT PRECIP WHICH SHOULD START AS SNOW BUT MAY
BECOME MIXED WITH RAIN BEFORE ENDING MON NIGHT.
CONTINUED WIDEPREAD SNOW FIELD OVER NRN 2/3 OF FCST AREA ALONG WITH
WIDSPREAD HIGH CLOUDS WILL TEMPER TEMPERATURE RISE TODAY . IT MAY
ALSO IMPACT HIGHS FRIDAY. IF SFC DEW POINTS RISE ENOUGH THERE COULD
BE SOME ADVECTIVE FOG AREAS FORMING ON FRI IN SLY FLOW. FOG/HAZE
FORMATION THIS MORNING HAS ALSO BE SLOW DUE TO CLOUDS SO WILL TAKE
ANY MENTION OF DENSE FOG FROM FCST. MOS NUMBERS GENLY REASONABLE.
KML
&&
.LOT...WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LK MI...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
AFDFWA 645 AM EST THU FEB 19 2004
.AVIATION...
MVFR VSBYS DUE TO RADIATIONAL COOLING FOG EXPECTED AT TERMINALS
THROUGH MID/LATE MORNING. BARRING ANY STRATUS FORMING EARLY THIS
MORNING, SHOULD JUST HAVE HIGH CLOUDS TODAY. SOME MINOR RESTRICTIONS
TO VSBY DUE TO SNOW MELT SHOULD LINGER THROUGH THE DAY. WITH WARM
FRONT DEVELOPING JUST TO SOUTH OF TERMINALS THIS AFTN AND LOW LEVEL
MOISTURE SURGING NE AHEAD OF LOW LIFTING NE OUT OF SRN PLAINS
TONIGHT, EXPECT CIGS/VSBYS TO COME DOWN TO IFR BY LATE TONIGHT.
&&
.PREV DISCUSSION...
SHORT TERM...
PROFILER/ACARS/ASOS INDICATE STILL FAIRLY GOOD MIXING OVER CWA WITH
ONLY LIGHT FOG. WITH SURFACE RIDGE MOVG INTO THE AREA WIND MAY DIE
OFF ENOUGH FOR SOME THICKER FOG OVER NWRN PORTION OF CWA AROUND DAWN
SO HAVE CONTINUED WITH MENTION THERE BUT DROPPED IN SE WHERE WINDS A
LITTLE STRONGER AND DEWPOINTS LOWER.
MODELS IN GOOD AGREEMENT THAT RIDGE WILL MOVE QUICKLY EAST TODAY AND
A WARM FRONT WILL DEVELOP FROM CENTRAL OH/IN/IL SW TO INTENSIFYING
SOUTHERN PLAINS LOW. DECENT LIFT WILL DEVELOP IN THE WAA REGIME
TODAY BUT MOISTURE LACKING FOR ANY PRECIP AND WILL JUST GO WITH
PARTLY CLOUDY SKIES. DRY LAYER IN MID LEVELS SHOULD PERSIST TONIGHT
BUT AS SURFACE LOW LIFTS NE INTO MID MS VALLEY LOW LEVEL MOISTURE
WILL INCREASE. THIS COMBINED WITH FAIRLY STRONG/DEEP LIFT SHOULD
RESULT IN SOME LIGHT RAIN/DRIZZLE DVLPG. WENT WITH HIGHEST POPS NW
WHERE GREATEST MOISTURE FCST BUT KEPT IN CHC CATEGORY AS STILL
QUESTIONABLE IF IT WILL BE MORE THAN A TRACE EVENT OVERNIGHT. WITH
RELATIVELY WARM MOIST AIR OVERSPREADING COLD SNOW COVERED GROUND
LEFT AREAS OF FOG IN FCST OVER MOST OF THE AREA TONIGHT. GENERALLY
WENT WITH MOS CONSENSUS FCST FOR TEMPS AS GUIDANCE FAIRLY CLOSE.
&&
LONG TERM...
FRIDAY THROUGH WEDNESDAY...GFS SHOWING CONSISTENCY IN THE TRACK OF
THE SFC LOW ACROSS NE IL AND SW LOWER MI...BUT THE GFS MODEL TRENDS
OF TOO SLOW AND NOT DEEP ENOUGH WITH THE SFC LOW CONTINUE...THE LAST
SEVERAL RUNS BACK TO MONDAY EVENING HAVE SHOWN A DEEPER AND MORE
PROGRESSIVE SYSTEM. LAST NIGHTS RUN WAS ABOUT 6 HOURS FASTER WITH
THE SFC LOW FOR FRIDAY EVENING THAN THE RUN FROM THE PREVIOUS NIGHT.
MOS FROM NGM...ETA AND GFS ALL ARE SHOWING STRONGER WIND SPEEDS
FRIDAY. THE MESO ETA WAS SHOWING AN IMPRESSIVE LOW LEVEL WIND FIELD
AT 925 MB ALONG WITH THE DEEPENING SYSTEM FRIDAY MORNING. SO HAVE
RAISED WIND SPEEDS INTO THE BREEZY CATEGORY FRIDAY. HAVE EXTENDED
DURATION OF FOG INTO FRIDAY MORNING OVER ANTICIPATED SNOW COVERED
AREAS IN THE NORTH. SNOW DEPTHS THURSDAY MORNING STILL SHOWED
SEVERAL INCHES AT A NUMBER OF LOCATIONS IN FAR SW LOWER MI. LESS
SNOW COVER WAS OVER N INDIANA AND NW OH. WILL FOLLOW THE TREND OF
THE GFS BRINGING EVEN COLDER AIR THAN EARLIER INDICATED FOR
SATURDAY...SO HAVE REMOVED ALL MENTION OF RAIN EXCEPT FOR THE FAR SE
INCLUDING AOH. AMOUNTS WILL BE LIGHT. WILL KEEP SUNDAY THROUGH
WEDNESDAY DRY WITH TEMPS NEAR NORMAL. CONSENSUS OF ECMWF...CANADIAN
AND MFR WAS TO DEVELOP A DEEP TROF ALONG THE WEST COAST WITH A
WEAKER SYSTEM OVER THE NE CONUS. THE ECMWF DOES BRING MORE ENERGY IN
THE MID MISSISSIPPI VALLEY THAN THE OTHER MODELS. THE CANADIAN
ENSEMBLES FROM LAST NIGHT REFLECTED THE MODEL CONSENSUS. WITH THIS
PATTERN...AMOUNT AND TIMING OF ENERGY EJECTED DURING THE FIRST HALF
OF NEXT WEEK FROM WESTERN TROF UNDER THE UPPER RIDGE OVER THE
CENTRAL CONUS STILL IN QUESTION. WILL THEREFORE KEEP FORECAST DRY
WITH TEMPS NEAR NORMAL.
&&
.IWX WATCHES/WARNINGS/ADVISORIES...
IN...NONE.
MI...NONE.
OH...NONE.
&&
$$
JT/SKIP