[LeArc] Forecast Discussion : MLI@ 2/3/03 4:23:50 PM

[learc@mailman.qth.net]

The following weather message is provided by McDonough County E.S.D.A.


FXUS63 KDVN 032228
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
430 PM CST MON FEB 3 2003

BUSY DAY TODAY WITH A GOOD STRONG DEFORMATION ZONE HEADING OUR WAY 
FOR LATER THIS AFTERNOON AND THIS EVENING.  VSBYS IN THE DEF ZONE 
ARE A HALF-MILE OR LESS.  SNOW IS ACCUMULATING AS MUCH AS AN INCH AN 
HOUR IN SOME PLACES.  IN FACT...OMA AT 19Z CAME IN WITH A SNOW 
INCREASING REMARK...WITH AN INCH ON THE GROUND.  LATEST SURFACE 
ANALYSIS INDICATED THAT SURFACE LOW WAS OVER NORTHEAST ILLINOIS... 
AND WAS RAPIDLY MOVING NORTHEAST WITH PRESSURE FALLS OVER LOWER 
MICHIGAN OF GREATER THAN 5 MB/HR.  NORTH WINDS KICKING IN OVER CWA 
QUITE STRONGLY...WITH GUSTS IN THE CWA TO 20 KTS SO FAR...THOUGH 
ALONG AND RIGHT BEHIND THE DEF ZONE GUSTS ARE OVER 30 KTS.  UPPER 
LEVEL ANALYSES SHOWING 850MB TRACK HAS GONE RIGHT OVER CWA...WITH 
VERY STRONG CAA OVER UPPER MIDWEST...WITH TEMPS WELL BELOW ZERO.  AT 
500 THE BEST HEIGHT FALLS AND DIVERGENCE WERE OVER KANSAS AS OF 
12Z...THERE IS SOME CONCERN THAT AS THE SYSTEM ROTATES EAST THE 
DIVERGENCE WILL WEAKEN...AND THAT THE DEF ZONE WILL ALSO WEAKEN.  
IMPRESSIVE 150KT JET OVER SRN NM...WEAKENING TO JUST UNDER 100KTS AT 
KDVN.  AGAIN...CONVERGENCE AT THIS LEVEL MAY WEAKEN DEF ZONE.

MIAN CONCERN THIS FORECAST INCLUDES THE HIGHLIGHTS AND SNOW AMOUNTS 
TONIGHT...AND THEN TEMPS TUESDAY THROUGH WEDNESDAY.  WEDNESDAY NIGHT 
SNOW CHANCES ALSO OF CONCERN.

12Z MODELS HANDLING THE EXITING SYSTEM TONIGHT IN A VERY SIMILAR 
MANNER...RUNNING HEAVY SNOW BAND THROUGH NORTHWEST CWA AROUND  
00Z...AND ENDING ALL BUT FLURRIES AROUND MIDNIGHT.  FOR NOW MODELS 
ARE SO CLOSE...HAVE GONE WITH A BLEND FOR TONIGHT...AND THEN LEANED 
TOWARDS THE AVN FOR LATTER PERIODS.  

SNOW BEGAN ACROSS THE CWA BETWEEN 3 AND 4 PM...BEGINNING IN A FEW 
LOCATIONS WITH A BIT OF RAIN OR SLEET.  SNOW AMOUNTS FROM UPSTREAM 
LEAD CREDENCE TO GOING FORECAST SNOW AMOUNTS...WITH THE MAX REPORTED 
SO FAR OF ABOUT 3 INCHES. QPF FROM ETA THE HIGHEST...AND WOULD 
RESULT IN ABOUT 4 INCHES ASSUMING STRONGEST SCENARIO.  AS DEF ZONE 
HAS BEEN DIMINISHING SOME AS IT MOVES TOWARDS THE AREA...4 INCH 
AMOUNTS NOT ESPECIALLY LIKELY...BUT WILL LEAVE AS MAX POSSIBLE IN 
ZONE TEXT.  NEXT FORECAST PROBLEM  TONIGHT IS THE CLEARING OF CLOUDS 
AFTER THE PRECIP MOVES OUT...WITH ATTENDANT AFFETCS ON LOW TEMPS. 
TONIGHT MAV AND ETA TEMPS TOO COOL...AS THEY ACTUALLY CLEAR OUT THE 
CLOUDS BEFORE 12Z.  AM GOING JUST SLIGHTLY COOLER THAN THE FWC LOWS 
IN MOST PLACES...WITH THE NGM HANGING ONTO CLOUDS UNTIL MID 
MORNING.  

TUESDAY HIGH TEMPS WITH SNOW ON THE GROUND ARE GOING TO MAKE WARM 
FWC TEMPS HARD TO REACH...DESPITE QUITE A BIT OF SUNSHINE.  HAVE 
GONE ON THE COOL SIDE...BUT NOT AS COOL AS MAV OR ETA TEMPS.  
WEDNESDAY NIGHT IS GOING TO BE THE COLD ONE...AND HAVE GONE WITH A 
BLEND OF THE COLDER ETA AND MAV TEMPS.  ON WEDNESDAY...THOUGH THERE 
IS A COLD FRONT MOVING TOWARDS THE AREA...EXPECT LITTLE EXTRA 
WARMING AHEAD OF IT AS THERE IS LITTLE OR NO SOUTHWEST RETURN FLOW 
TO ASSIST IN WARMING TEMPS UP.  HAVE STAYED WITH COOLER GOING 
TEMPS.  SNOW ON WEDNESDAY THROUGH THURSDAY KIND OF QUESTIONABLE. THE 
ETA HAS THE STRONGEST FEATURES...BUT THE AVN AND NGM ARE NEARLY 
DRY.  CANNOT RULE SNOW OUT DUE TO VICINITY OF UPPER LEVEL CYCLONIC 
FLOW AND WEAK SURFACE FEATURES...BUT LIMITING FACTOR WILL BE 
MOISTURE AVAILABILITY.  HAVE DECIDED NOT TO GO WITH ANY PRECIP ON 
WEDNESDAY FOR NOW...BUT LATER SHIFTS WILL HAVE TO RE-EVALUATE.  
WEDNESDAY NIGHT AND THURSDAY HAVE KEPT POPS ON THE LOW SIDE.

EXTENDED...FRIDAY THROUGH MONDAY
JUST ONE FAIRLY MARGINAL SYSTEM EXPECTED TO MOVE THROUGH THE AREA 
LATE ON SATURDAY AND SUNDAY.  FOR THE MOST PART...WHILE THERE WILL 
BE LARGE SCALE CYCLONIC FLOW THROUGH THE ENTIRE PERIOD...ONLY THE 
ONE SURFACE FRONT MOVES THROUGH...AND IS OTHERWISE TOO DRY FOR 
PRECIP.  WILL TWEAK UP WARMER TEMPS FOR SATURDAY AHEAD OF THE 
FRONT...BUT THEN THE REST OF THE WEEKEND IS BACK BELOW NORMAL...AND 
DO NOT INTEND TO VARY MUCH FROM FMR/MEX TEMPS.  WILL KEEP MONDAY ON 
THE COOL SIDE...AS IT DOES NOT APPEAR THAT THERE WILL BE ANY 
SOUTHERLY RETURN FLOW TO WARM TEMPS UP MUCH.

.DVN...
IA...WINTER WEATHER ADVISORY TONIGHT NEAR AND NORTHWEST OF A LINE 
FROM FAIRFIELD TO IOWA CITY TO MAQUOKETA TO DUBUQUE...AND A WIND 
ADVISORY FOR TONIGHT FOR THE REMAINDER OF IOWA COUNTIES.
IL...WINTER WEATHER ADVISORY TONIGHT FOR JO DAVIESS COUNTY...AND A 
WIND ADVISORY FOR TONIGHT FOR ALL OTHER ILLINOIS COUNTIES.
MO...WIND ADVISORY TONIGHT.

$$

LRE