[LeArc] Forecast Discussion : MLI@ 4/7/2003 3:43:25 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 072040
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
340 PM CDT MON APR 7 2003

UPPER LOW SEEN ON WATER VAPOR IMAGERY CHURNING OVER NORTHWEST IOWA 
AT 19Z. 12Z ANALYSIS INDICATED THAT UPPER LOW WAS NEARLY STACKED AND 
MORNING MODEL RUNS CONTINUE TO SLOW PROGRESSION OF SYSTEM. MSAS 
SHOWED MAIN SURFACE LOW WELL TO SOUTHEAST OVER KY AND PRESSURE 
GRADIENT HAS RELAXED CONSIDERABLY OVER PAST 12 HOURS WITH RESULTING 
WINDS DOWN TO 10 TO 20 KTS. FORECAST CHALLENGE IS LINGERING 
PRECIPITATION AND TYPE TONIGHT INTO TUESDAY AS UPPER LOW MOVES OVER 
REGION. 

FORECAST MODELS IN SIMILAR AGREEMENT WITH H5 LOW TRACKING TO EAST 
CENTRAL IOWA BY 12Z AND WENT WITH ETA/GFS BLEND. WIDESPREAD LIGHT 
SNOW OCCURRING MAINLY ALONG AND NORTH OF LOW TRACK AND SLOW 
PROGRESSION WILL BRING BULK INTO AREA LATE TONIGHT. LOOKS TO BE A 
HIGH POP AND LOW QPF EVENT AND HAVE BUMPED TO 60 PERCENT POPS IN 
NORTHWEST HALF...KEEPING HIGH SCATTERED IN SOUTHEAST. WILL MENTION 
ADDITIONAL ACCUMULATIONS UP TO AN INCH MAINLY NORTH OF HIGHWAY 30. 
PATCHY DRIZZLE OCCURRING AT DVN THIS AFTERNOON AND DIFFICULT TO 
DISCERN FROM ASOS REPORTS WITH WIDESPREAD VISIBILITIES BELOW 3 MILES 
THIS AFTERNOON. CURRENT THINKING IS THAT THIS WILL CONTINUE UNTIL 
UNTIL LOW SHIFTS EAST-SOUTHEAST AND COLUMN COOLS WITH COLD POOL 
MOVING INTO AREA. THIS ALONG WITH UPPER LEVEL MOISTURE AND CLOUDS 
WILL END ZL POTENTIAL BY MIDNIGHT. TEMPERATURES AND PRECIP TO KEEP 
TEMPERATURES FROM DROPPING MUCH AND DID NOT STRAY FAR FROM MAV 
GUIDANCE WITH MID 20S NORTH TO AROUND 30 SOUTH.

CYCLONIC LOW LEVEL FLOW WITH LINGERING MOISTURE TRAPPED BELOW 
INVERSION AROUND H85 WILL KEEP CLOUDS AROUND THROUGH TUESDAY. ENOUGH 
LIFT REMAINS UNDER DEPARTING CLOSED LOW UNTIL ABOUT MIDDAY FOR 
CONTINUED CHANCES OF LIGHT SNOW AND RAISED POPS ABOVE GUIDANCE TO 40 
PERCENT IN SOUTHEAST WITH 30 NORTHWEST...THEN FLURRIES WORDING FOR 
AFTERNOON. TEMPERATURES WILL NOT CLIMB MUCH...AND COMPROMISE BETWEEN 
COLDEST NGM MOS AND GFS MOS LOOKS GOOD WITH ONLY 30S ACROSS CWFA. 
MODELS MAY BE TRYING TO CLEAR THINGS OUT TOO QUICKLY TUESDAY NIGHT 
AS SURFACE RIDGE MOVES ONLY INTO CENTRAL IA WITH LOCAL LINGERING LOW 
LEVEL MOISTURE FROM SNOWFALL. THIS WILL MAKE LOW TEMPERATURE 
FORECAST TRICKY. WENT NEAR TO BELOW MAV IN NORTH...AND ABOVE IN 
SOUTH.  

MUCH LESS THAN ANTICIPATED SNOW COVER WILL ALLOW TEMPERATURES TO 
RISE FASTER IN MID TO LATE WEEK TIMEFRAME. MOST OF 1 INCH SNOW HERE 
ALREADY GONE...AND THINK BY MIDDAY WEDNESDAY WILL ONLY HAVE SNOW 
COVER ALONG HARDEST HIT AREA NORTH OF HIGHWAY 20...WHERE AMOUNTS
AROUND 6 INCHES REPORTED. STILL...HAVE LEFT IMPACT IN NORTH AND KEPT 
TEMPS BELOW GUIDANCE WITH 40S NORTH AND 50S SOUTH. CLEAR SKIES AND 
RIDGE OVERHEAD WILL SET STAGE FOR NIGHT IN 20S THURSDAY MORNING.

IN EXTENDED...ALL MODELS HAVE UPPER RIDGE THAT BUILDS OVER WEST 
THROUGH MID WEEK SLIDING EAST WITH WARMING TREND INTO WEEKEND. MADE 
ONLY MINOR UPWARD ADJUSTMENTS TO TEMPERATURES. MOVED CHANCES FOR 
SHOWERS AND THUNDERSTORMS TO SATURDAY NIGHT TIMEFRAME AS DEVELOPING 
HIGH PLAINS LOW PUSHES WARM FRONT THROUGH AREA. 

.DVN...
IA...NONE.
IL...NONE.
MO...NONE.

$$
DLS