[LeArc] Forecast Discussion : MLI@ 5/8/2003 5:02:50 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 082152
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
452 PM CDT THU MAY 8 2003

BAND OF SHOWERS AND A FEW THUNDERSTORMS FINALLY MANAGING TO DROP
PRECIPITATION ACROSS THE CWA. THIS PRECIP FORMED OFF OF THE 850MB
FRONT...WITH THE SURFACE FRONT STILL ACROSS CENTRAL KS/MO AS OF
18Z. THE SURFACE FRONT IS LIGHTING UP NOW...WITH SOME PRETTY
SIGNIFICANT STORMS APPARENT ON SATELLITE AND RADAR IMAGERY.  UPPER
LEVELS ANALYSIS INDICATING THE STRONG LOW LEVEL JET HELPING TO FIRE
CONVECTION EXTENDING FROM SOUTHERN TX TO EASTERN KS...WITH PLENTY OF
MOISTURE HAVING STREAMED UP OVER MUCH OF THE MIDWEST.  500MB TROUGH
STILL OVER THE ROCKIES...BUT SOME PRETTY SIGNIFICANT SHORT WAVES
MOVING OUT OF THE ROCKIES TO OVER KANSAS...AGAIN ASSISITING
CONVECTION THERE.

MAIN CONCERNS THIS FORECAST INCLUDE THUNDERSTORM TIMING TONIGHT
THROUGH SATURDAY...WITH ATTENDANT SEVERE AND FLOODING CONCERNS.

12Z MODELS APPEAR TO HAVE INITIALIZED REASONABLY WELL THIS MORNING...
WITH BETTER AGREEMENT THROUGH THE PERIOD THAN ON YESTERDAYS RUNS.
ETA IS STILL MORE PROGRESSIVE AT 500 MB THAN THE OTHER MODELS...EVEN
TO THE POINT OF BEING THE ODD ONE OUT BY 36 HRS.   HOWEVER...SURFACE
FEATURES ARE VERY CLOSE...AND NGM APPEARS TO BE THE ODD ONE OUT
THEN WITH ITS TOO FAR INTO THE COLD AIR BIAS.  WILL BE GOING WITH A
BLEND BETWEEN MODELS FOR THIS FORECAST.

DUE TO 3 HOUR FFG VALUES BETWEEN 1.5 TO AROUND 2 INCHES...
WIDESPREAD HEAVY RAINFALL OF BETWEEN .75 AND 1.5 DUE IN...WITH
LOCALLY HIGHER AMOUNTS POSSIBLE OF UP TO 3 INCHES...HAVE DECIDED TO
GO WITH A FLOOD WATCH TONIGHT...FOR THE WESTERN 1/3 TO 1/2 OF THE
CWA.  SEVERE THREAT ALSO EXISTS FOR TONIGHT...MAINLY HAILERS...BEING
NORTH OF THE SURFACE FRONT.  CONVECTION NOW DEVELOPING OVER
SOUTHEASTERN NEBRASKA SHOULD CONTINUE TO DEVELOP ALONG THE 850MB
FRONT AND MOVE NNE...GETTING INTO THE CWA BY MID TO LATE EVENING.
STORMS COULD BE QUITE STRONG WITH DECENT DYNAMICS ALOFT...AND STRONG
SOUTHERLY 850MB JET BRINGING IN HIGH DEWPOINT AIR.

FRIDAY IS MORE OF A QUESTION.  THE WARM FRONT WILL BE NORTH OF THE
AREA...WITH A WIND SHIFT LINE/WEAK COLD FRONT MOVING FROM WEST TO
EAST ACROSS THE AREA.  850MB LOW LEVEL JET WILL SHIFT BACK WEST IN
THE MORNING...AND MORE CONVECTION SHOULD FIRE IN THE EASTERN KANSAS
AND WESTERN MISSOURI AREA...WITH MAY MANAGE TO AFFECT THE SOUTHERN
AREAS OF THE CWA DURING THE EVENING.  MUCH DEPENDS ON WHAT THE
FRONT DOES TONIGHT...AND HAVE HUNG ONTO PRECIP CHANCES FOR ENTIRE
CWA FRIDAY NIGHT.

SATURDAY COULD BE ANOTHER VERY BUSY DAY/NIGHT WITH A SURFACE LOW TO
MOVE FROM EASTERN KANSAS AROUND 12Z TO NORTHEAST IOWA BY 00Z.
SEVERE WEATHER IS POSSIBILITY ONCE AGAIN WITH THIS TRACK. THERE ARE
ENOUGH DIFFERENCES IN THE MODELS FOR THE TRACK OF THIS LOW TO DO
MUCH NARROWING DOWN...AND HAVE KEPT THINGS PRETTY WELL BROAD BRUSHED
FOR NOW.

.EXTENDED (MON-THU)...MONDAY LARGE UPPER LEVEL LOW DRAWS OFF TO THE
EAST...ALLOWING RIDGING TO BEGIN BUILDING OVER THE AREA FOR TUESDAY
AND WEDNESDAY. THURSDAY BEGINNING TO LOOK QUESTIONABLE...WITH AN
INVERTED TROUGH PUSHING UP INTO THE AREA AT THE SURFACE...AND A
SHORTWAVE DUCKING SOUTH OF THE RIDGE ACROSS THE AREA.  FOR NOW...
HAVE JUST PUT CHANCES FOR SHOWERS AND THUNDERSTORMS ON THURSDAY...
THOUGH MAY EVENTUALLY NEED PRECIP FOR WEDNESDAY NIGHT AS WELL.

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

$$

LRE