[LeArc] Forecast Discussion : MLI@ 4/13/2003 3:53:43 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 132049
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
349 PM CDT SUN APR 13 2003

ANOTHER VERY QUIET...MOSTLY CLEAR...AND DRY DAY ACROSS THE CWFA.
STRENGTHENING WARM FRONT OVER WESTERN IA SLOWLY BEING PUSHED
TOWARDS THE AREA BY STRONG SOUTHERLY FLOW.  THIS FRONT SHOULD MOVE
THROUGH THE AREA OVERNIGHT TONIGHT.  TEMPERATURES ON THE SOUTHWEST
SIDE OF THIS FRONT HAVE BEEN IN THE LOW TO MID 80S...WITH ONLY A
LITTLE MORE CUMULUS THAN WE HAVE NOW...WITH DEWPOINTS IN THE MID TO
UPPER 40S.

MAIN FORECAST PROBLEM OF TODAY INCLUDE TEMPERATURES MONDAY AND
TUESDAY...AND THEN THE ONSET OF PRECIPITATION TUESDAY.

12Z MODELS APPEAR TO HAVE INITIALIZED REASONABLY WELL.  AM HAVING
TO REVERSE YESTERDAYS CHOICE...BY TAKING THE MORE SOUTHERLY SOLUTION
OF THE ETA RATHER THAN THE AVN.  REASONS INCLUDE:  MOST OTHER
MODELS INDICATING THE MORE SOUTHERLY SOLUTION.  THIS TIME OF YEAR
WITH COLD LAKE MICHIGAN...THERE IS A TENDENCY FOR FRONTS TO DRAPE
JUST TO ITS SOUTH...RATHER THAN ACROSS THE CENTER OF IT. WITH ANY
SORT OF EASTERLY FLOW...COLD AIR TO THE NORTH OF THE FRONT IN
ENHANCED...CAUSING THE FRONT TO DROP SOUTH.  THAT SAID...AM GOING
WITH THE MORE SOUTHERLY ETA MODEL FOR THE MOST PART.

MONDAY TEMPERATURES HAVE BEEN THE SOURCE OF MUCH THOUGHT LATELY.
HAVE CONTINUED THE TREND OF GOING WELL ABOVE GUIDANCE...THOUGH
THINK THAT THE ETA HAS GONE OVERBOARD THIS TIME.  850 TEMPS AROUND
16 WOULD MIX DOWN DRY-ADIABATICALLY TO A HIGH AROUND 86...SO HAVE
GONE WITH TEMPS IN THE LOW TO MID 80S EVERYWHERE...WHICH SHOULD
MATCH FAIRLY WELL WITH SURROUNDING FCSTS...AND IS SIMILAR TO GOING
FORECAST.  THESE TEMPS ARE ALL RECORD OR NEAR RECORD VALUES...AND WILL
KEEP WORDING IN FOR THAT ALL ZONES.

TUESDAY THE MAIN QUESTION HAS BEEN HOW WARM TO GO WITH INCOMING
PRECIPITATION.  HAVE DECIDED THAT A WAA WING WILL PASS ACROSS THE
AREA DURING THE AFTERNOON...AND COMBINED WITH SOME PRETTY JUICY LOW
TO MID 50S DEWPOINTS...SHOULD GET SHOWERS AND TSTMS DURING THE
AFTERNOON.  WHILE WE WILL BE WELL MIXED AGAIN...WE WONT GO DRY
ADIABATIC OR SUPER-ADIABATIC AT ALL...AND MORE MOIST ADIABATIC.

TUESDAY NIGHT AND WEDNESDAY MORNING THE FRONT SAGS SOUTH TO ACROSS
THE NORTHERN PORTIONS OF THE CWA WITH EASTERN EDGES SOUTH OF THE
LAKE...AND WILL MAKE FOR BIG POTENTIAL BUST ON TEMPS.  LIKE
PREVIOUS SHIFT HINTED...HAD TO LOWER TEMPS ACROSS THE NORTH
SIGNIFICANTLY...AND NOW HAVE NEARLY A 15 DEGREE DIFFERENCE ACROSS
FA.  HAVE HUNG ON TO FAIRLY HIGH POPS (LIKELY) FOR BOTH PERIODS...
THOUGH DROPPED TO CHANCE FOR SOUTHERN TWO-THIRDS FOR TUESDAY NIGHT.

EXTENDED...WEDNESDAY NIGHT THROUGH SUNDAY
NOT GOING TO CHANGE MUCH IN THIS TIME FRAME.  NEW MODELS SHOWING
VARIABILITY THAT WAS NOT HERE YESTERDAY...ESPECIALLY IN THE EJECTION
OF THE UPPER LEVEL LOW FROM THURSDAY ON...AND THE TIMING OF THE
PRECIPITATION SATURDAY.  LIKE HPC...WILL BE FAVORING THE SLOWER OF
THE SOLUTIONS...AND HAVE DELAYED PRECIP A LITTLE FOR THURSDAY.
FRIDAY STILL DRY...BUT AM BRINGING IN PRECIP TO ALL CWA FRIDAY
NIGHT AND SATURDAY.  WILL BE CONTINUING PRECIPITATION INTO SUNDAY...
BUT SHOULD END BY SUNDAY EVENING.

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

$$

LRE