[LeArc] Forecast Discussion : MLI@ 1/13/03 2:50:03 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 132059
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
300 PM CST MON JAN 13 2003

SURFACE LOW OVER WRN NE EARLY THIS AFTERNOON.  SWATH OF LIGHT TO 
MODERATE SNOW ONGOING NORTHEAST OF LOW FROM ERN ND INTO SERN MN.
MODELS APPEAR TO BE DOING REASONABLY WELL WITH THIS SYSTEM.  
ALTHOUGH BY 18Z THE GFS WAS HANDLING THE SURFACE SYSTEM BETTER WHILE 
THE ETA WAS TOO WEAK AND TOO FAR TO THE NE.  BASED ON VISIBILITIES 
IN THE SNOW AREA...IT LOOKS LIKE BOTH THE ETA AND GFS QPF FIELDS 
NEED TO BE SHIFTED A TAD TO THE NORTHEAST.

MAIN CONCERN THIS ISSUANCE WILL BE THE SNOWFALL TONIGHT ASSOCIATED 
WITH THE SYSTEM OVER THE PLAINS.  AGAIN...MODELS ARE HANDLING THIS 
SYSTEM REASONABLY WELL. ISENTROPICS ON THE 285 AND 290 SURFACES 
ALONG WITH Q VECTOR AND OMEGA AROUND H7 ALL SUGGEST THAT THERE IS 
ENOUGH FORCING TO PRODUCE UP TO A COUPLE OF INCHES OF POWDERY SNOW 
OVERE NERN CWA.  BELIEVE MOST OF ACCUMULATION WILL BE THIS EVENING 
WITH FLURRIES LINGERING INTO TUESDAY MORNING.  WILL GO WITH 1 TO 2 
INCHES NORTHEAST OF A LINE...FROM JUST WEST OF DUBQUE TO
JUST EAST OF THE QUAD CITIES...THEN TAPER OFF TO JUST A DUSTING TO 
THE SOUTHWEST.  

A HIGH PRESSURE RIDGE BUILDS IN BEHIND SYSTEM FOR TUESDAY INTO EARLY 
WEDENSDAY...BRINGING ANOTHER ROUND OF FRIGID TEMPS TO THE REGION 
TUESDAY NIGHT.  TEMPS WILL GENERALLY FAVOR THE COLDER MAV NUMBERS 
THROUGH THE PERIOD.  TUESDAY NIGHT SHOULD BE THE COLDEST NIGHT WITH 
CLEAR SKIES MOST OF THE NIGHT AND LIGHT WIND. IF SNOW MATERIALIZES 
AS EXPECTED TONIGHT...THEN NERN CWA SHOULD SEE TEMPS WELL BELOW ZERO 
WEDNESDAY MORNING.

MODELS STILL SUGGESTING A MORE SOUTHERLY TRACK FOR THE WEDNESDAY 
NIGHT/THURSDAY SYSTEM.  ECMWF HOWEVER CONTINUES TO SUGGEST A MORE 
NORTHERLY TRACK.  TAKING THIS INTO ACCOUNT AND THE ETA/GFS HINTING 
THE H5 LOW MAY CLOSE OFF BRIEFLY THURSDAY MORNING MAKING DEG ZONE 
PCPN POSSIBLE FURTHER N...WILL LEAVE GOING FORECAST INTACT.

EXTENDED (FRIDAY THROUGH MONDAY)
BROAD H5 TROF OVER CENTRAL U.S. IS DOMINANT THROUGH THE WEEKEND INTO 
EARLY NEXT WEEK.  SEVERAL REINFORCING SHOTS OF COLD AIR MOVE OUT OF 
CANADA EARLY IN PERIOD.  TIMING OF THESE FEATURES WILL HAVE A LARGE 
IMPACT ON TEMP FORECAST.  FOR NOW WILL STICK CLOSE TO MEX SINCE 
SINCE A FEW HOURS VARIATION ON PLACEMENT OF RIDGE AXIS OR FRONTS 
COULD HAVE A SIGNIFICANT EFFECT ON TEMPS.  MOST NOTABLE FEATURE WILL 
BE SFC LOW MOVING THROUGH CENTRAL CANADA...DRAGGING A COLD FRONT 
THROUGH THE MID MISSISSIPPI VALLEY MONDAY.  SYSTEM LOOKS POTENT 
ENOUGH TO JUSTIFY THE MENTION OF SOME LIGHT SNOW.  

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

DLF