[LeArc] Forecast Discussion : MLI@ 1/13/03 1:41:30 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 130751
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
145 AM CST MON JAN 13 2003

.OVERVIEW...NEXT SURGE OF ARCTIC AIR ALMOST THROUGH ALL OF AREA WITH
LEADING EDGE OF FRONT EXTENDING AT 06Z FROM NEAR CHICAGO BACK TO
KANSAS CITY MOVING SOUTHEAST AT 25-30 MPH ON BRISK NW WINDS OF 15-25
MPH.  LITTLE SENSIBLE WEATHER NOTED ACROSS AREA IN FORM OF CLOUDS...
BUT CLOUDS AND LIGHT SNOW NOW BREAKING OUT UPSTREAM ACROSS DAKOTAS IS
DIVING SE AT 45-50 MPH. THIS IS DUE TO WEAK SHORT WAVE INTERACTING ALONG
BAROCLINIC ZONE OF ARCTIC FRONT. AWIPS DISTANCE TIME FEATURES SUGGEST
THESE LOW/MID CLOUDS TO MOVE ACROSS AREA BETWEEN 10 AND 15Z FROM WEST
TO EAST. UPPER AIR ANALYSIS SUPPORTS WEAK WAVE OF THIS SYSTEM TO SLIDE
ACROSS AREA NEXT 24 HOURS.

...ASSESSING CLOUDS AND LIGHT SNOW CHANCES LATE TODAY AND TONIGHT
AND THEN SNOW CHANCES WITH NEXT SYSTEM MID WEEK MOST NOTABLE
FORECAST ISSUES...

.DIAGNOSIS AND DAY 1-3...LIGHT NORTHERN PLAINS PRECIPITATION HANDLED
WITH NORMAL AVN TOO WET AND ETA/NGM TOO DRY TRENDS...IN LINE FOR
MARGINAL FORCED AND MOIST STARVED EVENTS.  MODELS CAPTURE ADEQUATELY
UVV AND DO WELL ON STRONG BAROCLINIC ZONE.  THUS WILL COMBINE THESE WITH
NOWCAST TOOLS FOR PRECIPITATION FORECASTS. THIS SUPPORTS A TYPICAL
WEAK NW IMPULSE WITH AREA BECOMING CLOUDY WITH SOME FLURRIES TO
DEVELOP TOWARD MID AFTERNOON IN IOWA.  THEN NARROW BANDS OF LIGHT TO
BRIEFLY MODERATE SNOW TONIGHT OVER NE 2/3 AREA AS DISTURBANCE SLIDES
ACROSS REGION.  WITH FAIRLY COLD TEMPS AND EXPECTED SNOW OF AT LEAST
A FEW HUNDREDTHS...WILL GO LIKELY POPS THERE TONIGHT WITH SNOW AMOUNTS
AN INCH OR LESS WITH 20 TO 25 TO 1 RATIOS EXPECTED. TEMPS WILL TREND
WITH LOTS OF CLOUDS AND GOOD CAA...NEAR TO BELOW TODAY BLEND. TONIGHT
WITH CLOUDS AND SOME PRECIPITATION EXPECT LOWS 1-2 CATEGORIES ABOVE
BLEND AND THEN NEAR TUESDAY.  GOOD RADIATIONAL CONDITIONS COOLING
WEDNESDAY AM SFC RIDGE OVERHEAD AND MOSTLY CLEAR SKIES...LIGHT WINDS.
INCREASING HIGH CLOUDS LATE WEDNESDAY WITH FLURRIES OR LIGHT SNOW
POSSIBLE SOUTHERN 1/2 AREA PER UKMET AND AVN-GFS AHEAD OF NEXT MODERATE
STRENGTH SYSTEM.

.EXTENDED (THU-SUN)...FORCING PER BOTH AVN-GFS/UKMET SUGGEST SYSTEM
TO SLIDE MOSTLY SOUTH PER RECENT EL NINO INFLUENCED SYSTEMS...ALSO DUE
TO STRONG NW FLOW UPSTREAM.  ECMWF FURTHER NORTH BUT MODEL BLEND OF
BAROCLINIC ZONES SUGGEST IT IS MORE LIKELY TO FOLLOW CLOSER TO SOUTHERN
TRACK.  HOWEVER...FORCING AND THERMAL FIELDS OF BOTH MODELS SUGGEST
AREAS ALONG AND SOUTH OH HIGHWAY 34 TO SEE SOME SNOW WILL MINOR
ACCUMULATIONS OF A FEW INCHES....THUS UP CHANCES TO LIKELY THERE WITH
MINOR ACCUMULATION WORDING.  KEEP CHANCE OF LIGHT SNOW NORTH OF THIS
AREA WITH UPPER TROUGH ROTATING.  TEMPS...PLAN TO TREND GENERALLY NEAR
FMR/MEX.  GENERALLY DRY REST OF PERIOD WITH NW FLOW THOUGH SOME FLURRIES
POSSIBLE IN EMBEDDED WEAK UPPER DISTURBANCES BUT LEAVE OUT FOR NOW DUE
TO WEAK FORCING.

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

NICHOLS