[LeArc] Forecast Discussion : MLI@ 5/20/2003 4:22:46 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 202114
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
414 PM CDT TUE MAY 20 2003

RELATIVELY QUIET WEATHER DAY ACROSS CWA...WITH ABUNDANT SUNSHINE...
AND DEWPOINTS IN THE 30S AND LOW 40S.  TEMPS HAVE RISEN INTO THE
UPPER 50S TO MID 60S...AND MAY TOP OUT IN THE UPPER 60S IN A FEW
LOCATIONS.  SURFACE RIDGE BUILDING IN NICELY...THOUGH BEST PRESSURE
RISES ARE ACROSS MICHIGAN...SO RIDGE SHOULD PASS TO THE NORTH OF
THE CWA. SURFACE FRONT THAT BROUGHT IN THE COOLER AND DRIER AIR NOW
WELL TO THE EAST OF THE MIDWEST.  UPPER LEVELS INDICATING THE TROUGH
AT 700MB ON UP...STILL OVER CWA BUT THE 850 TROUGH EAST OF THE CWA
WITH THE RIDGE BUILDING INTO THE UPPER MIDWEST.

MAIN CONCERNS INCLUDE TEMPS NEXT FEW DAYS...AND THE PRECIP CHANCES
INTO THE WEEKEND.

12Z MODELS APPEAR TO BE REASONABLY WELL INITIALIZED...THOUGH SOME
INTERESTING INTERACTIONS GOING ON WITH THE GFS FROM RUN TO RUN...
FROM ABOUT 72 HRS ON OUT.  FOR THE EARLIER PERIODS...HAVE GONE WITH
A BLEND OF THE MODELS.

TONIGHT THERE IS THE POSSIBILITY FOR FROST...WITH THE SURFACE RIDGE
JUST TO THE NORTH OF THE AREA...AND WINDS DROPPING OFF IN THE
VICINITY OF THE RIDGE.  SOME OF THE CIRRUS MOVING THROUGH THE UPPER
LEVEL FLOW MAY MANAGE TO GET OVER THE AREA TO REDUCE RADIATIONAL
POTENTIAL. SURFACE WINDS WILL ALSO SERVE TO KEEP THE RADIATIONAL
POTENTIAL DOWN...BY NOT DROPPING OFF COMPLETELY.  HAVE DECIDED TO
MENTION PATCHY FROST IN THE NORTHERN GROUPS...WONT BE WIDESPREAD
ENOUGH FOR ADVISORY.

THURSDAY NIGHT SOME UPPER LEVEL IMPULSES MOVE THROUGH THE FLOW
AHEAD OF THE UPPER LEVEL LOW FOR THE WEEKEND AND SHOULD INCREASE
CLOUDS OVER THE CWA AT THE LEAST.  THERE MAY BE ENOUGH MOISTURE
FRIDAY MORNING FOR SOME SHOWERS...BUT THIS LOOKS PRETTY IFFY AND
HAVE GONE WITH ONLY A SLIGHT CHANCE FOR FRIDAY.  FRIDAY NIGHT LOOKS
QUITE DRY...BEING BETWEEN WAVES AND MOISTURE BANDS.

EXTENDED DISCUSSION...DAYS 4 THROUGH 7.
MAIN WEATHER STORY FOR SATURDAY THROUGH TUESDAY PERIOD IS AMPLIFIED
PATTERN WITH NORTH-NW UPPER LEVEL FLOW OVER FORECAST AREA AS RESULT
OF UPPER LEVEL RIDGE OVER ROCKIES AND CUT OFF LOW OVER GREAT LAKES
INTO NORTHEAST CONUS. 12Z GFS NOT AS BULLISH AS 06Z RUN WITH DEPTH
AND WESTWARD PLACEMENT OF H5 LOW AND IS NOW CLOSER TO YESTERDAYS
WEAKER ECMWF AND UK SOLUTIONS THAT HAVE BEEN MORE CONSISTENT OVER
PAST FEW RUNS. THEY NOW PLACE UPPER LOW OVER EASTERN OHIO/WESTERN PA
SATURDAY NIGHT. THIS WOULD RESULT IN MORE ANTICYCLONIC UPPER LEVEL
FLOW OVER FORECAST AREA AND LESS FAVORABLE FOR DAILY RAIN CHANCES.
GUIDANCE TEMPERATURES LOOK TO BE ON COOL SIDE FOR THIS LATEST TREND
AND LITTLE CHANGES MADE TO GRIDS THAT WERE ALREADY TRENDED FOR LESS
PESSIMISTIC SOLUTION. KEPT IN CHANCES FOR SHOWERS SUNDAY NIGHT AND
MONDAY WITH GFS SHOWING CHANNELED VORTICITY ROTATING AROUND UPPER
VORTEX TO DROP OVER AREA...ALTHOUGH BOTH CONFIDENCE AND QPF LOW AS
WILL BE DIFFICULT TO RESOLVE WEAK WAVES IN FLOW AND FOR ANY PRECIP
TO SATURATE DRY LOW LEVELS.

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

$$

LE/SHEETS