[LeArc] Forecast Discussion : MLI@ 4/17/2003 3:15:24 AM

[learc@mailman.qth.net]

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


FXUS63 KDVN 170810
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
310 AM CDT THU APR 17 2003

SYNOPTIC PICTURE THIS MORNING SHOWS SURFACE LOW JUST EAST OF STL
HEADING TOWARDS EVV...WITH STACKED 500MB LOW.  DRIZZLE HAS SHIFTED
MAINLY EAST OF THE AREA...BUT EXTENSIVE CLOUD COVER EXTENDS BACK
INTO NEBRASKA AND THE DAKOTAS. NORTHEAST WINDS ARE STILL GUSTING TO
30 MPH.

THE MODELS INITIALIZED WELL AT THE SURFACE AND 500MB.  THE PRIMARY
FORECAST CONCERNS ARE THE DEPARTING SYSTEM...AND A COMPLEX SYSTEM
MOVING OUT OF THE CENTRAL PLAINS IN THE FRIDAY EVENING THROUGH SUNDAY
TIME FRAME.

THE DEPARTING SYSTEM WILL MOVE EAST OF THE AREA TODAY...WITH THE
SURFACE LOW TO JUST WEST OF SDF BY 00Z.  PRECIP...IN THE FORM OF
LIGHT RAIN OR DRIZZLE WILL LINGER IN THE EXTREME EASTERN COUNTIES
THIS MORNING.

THE MODELS...BOTH SHORT AND MEDIUM RANGE...ARE ALL OVER THE PLACE ON
THE INCOMING SYSTEM.  SIGNIFICANT DISAGREEMENT EXISTS FOR ALL OF
THE MAJOR PARAMETERS...INCLUDING SURFACE LOW...500MB LOW...AND
TIMING.  THE MODELS DO AGREE ON THE LOW MOVING OUT OF THE CENTRAL
ROCKIES AND INTO THE PLAINS ON FRIDAY...WITH A DOUBLE-LOW
STRUCTURE.  IT IS THAT DOUBLE LOW WHICH PRESENTS ONE OF THE
PROBLEMS.  IF THE SOUTHERN LOW PREDOMINATES...THEN STORM PASSAGE OVER
THE WEEKEND WOULD BY PRIMARILY COOL AND OCCLUDED IN TYPE.  IF THE
NORTHERN LOW PREDOMINATES...THEN WE GET INTO A SIGNIFICANT WARM
SECTOR PERIOD...BRACKETED BY WARM AND COLD FRONT PASSAGES.  THE
BEST CONSENSUS IS THAT THE SURFACE AND 500MB LOWS WILL LIFT TO OUR
WEST AND NORTH.  A VORT LIFTS THRU THE AREA FRIDAY AFTERNOON
AND EVENING...WITH WARM FRONT PASSAGE FRIDAY NIGHT.  WE STAY WARM
SECTOR INTO SUNDAY WITH COLD FRONT PASSAGE SUNDAY AFTERNOON OR
EVENING.  HOWEVER...THE ETA AND AVN BOTH SPIT OUT AN INCH PLUS OF
QPF IN-BETWEEN THESE FRONTS ON SATURDAY AND SATURDAY NIGHT...IN
RESPONSE TO PVA...STRONG VV'S...AND ESPECIALLY FOR SATURDAY STRONG
300MB DIVERGENCE.  MAY EVEN HAVE TO HANG ONTO PRECIP MONDAY...AS A
TRAILING TROF ROTATES AROUND THE RECEDING LOW AND SOUTH THRU
FORECAST AREA.

WILL STAY CLOSE TO ONGOING FCST...WHICH BANKS ON WARM SECTOR SOLUTION
AND PRECIP IN SEVERAL PERIODS.  ONLY MINOR TWEAKS.

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

$$

REA