[LeArc] Forecast Discussion : MLI@ 4/28/2003 2:31:01 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 281929
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
228 PM CDT MON APR 28 2003

AN AREA OF RAIN WITH EMBEDDED THUNDERSTORMS MAKING ITS LEISURELY WAY
ACROSS THE SOUTHERN HALF OF THE CWA THIS MORNING AND AFTERNOON...
THOUGH MOST OF IT SHOULD BE EAST OF THE CWA BY ISSUANCE TIME.  UPPER
LEVELS INDICATING A COMPLICATED PATTERN ACROSS THE AREA...WITH A
WEAK 850MB LOW OVER EASTERN KANSAS WITHIN A LARGER SCALE TROUGH
DRAPED FROM JAMES BAY TO WEST TEXAS.  NO MOISTURE YET BEING BROUGHT
NORTH IN THE SOUTHERLY FLOW OUT OF THE GULF...THOUGH EXPECT THAT
VERY SOON THE SOUNDINGS WILL BEGIN TO SHOW DEEPER MOISTURE LAYERS
DOWN SOUTH.  THE UPPER LEVEL SYSTEM THAT WILL BRING RAIN TO THE AREA
ON WEDNESDAY AND THURSDAY JUST NOW MOVING ON SHORE OVER NORTHERN
CALIFORNIA...WITH SOME MODERATE HEIGHT FALLS OVER CALIFORNIA.

MAIN CONCERN THIS FORECAST INCLUDES PRECIP CHANCES THROUGH THE
PERIOD...FROM WEAK MCS LIKE FEATURES THAT ROLL ACROSS THE AREA
DURING THE PERIOD.

12Z MODELS...LIKE THE 00Z RUNS FROM LAST NIGHT HAVING DIFFICULTY
COMING INTO DECENT AGREEMENT ON POSITION OF SURFACE FRONT NEXT 24
TO 48 HOURS.  POSITION OF THIS FRONT IS CRITICAL FOR PLACING
PRECIPITATION...AS MCS LIKE FEATURES TO INITIATE ON IT...AND THEN
MOVE EAST IN THE 700MB FLOW.  INITIATION TO DEPEND ON WEAK FEATURES
IN THE UPPER LEVEL FLOW...WHICH CAN BE TRICKY TO TIME.  UNTIL
MODELS GET A GOOD HANDLE ON SYSTEM THAT WAS JUST COMING ON SHORE TO
BE EVEN PARTIALLY SAMPLED AT 12Z...HAVE LITTLE CONFIDENCE IN MODELS
PLACEMENT OF SUCH SMALL SCALE FEATURES. THAT SAID...HAVE DECIDED TO
GO MAINLY WITH THE ETA SOLUTION...WITH THE FRONT SINKING SOUTH TO
ALONG I-70 TONIGHT...AND STAYING THERE AS NEW MCS INITIATES OVER
WESTERN NEBRASKA.  BY TUESDAY MORNING...THE MCS SHOULD BE OVER THE
EASTERN KANSAS/NEBRASKA BORDER AREA...THEN TO THE DVN CWA FOR THE
AFTERNOON HOURS.  THE FRONT REMAINS ALONG OR JUST NORTH OF I-70 FOR
MOST OF TUESDAY.  TUESDAY NIGHT THE SURFACE LOW WITH THE MAIN UPPER
LEVEL SYSTEM FINALLY DEVELOPS OVER EASTERN COLORADO...AND THE FRONT
BEGINS TO SHIFT NORTH.  BY WEDNESDAY MORNING THE FRONT WILL BE
APPROACHING THE SOUTHERN FRINGES OF THE CWA...AND IT AND A BAND OF
NICE WARM AIR ADVECTION WING PRECIPITATION WILL MOVE ACROSS THE
AREA ON WEDNESDAY...WITH SOME CHANCES FOR PRECIP WEDNESDAY NIGHT
TOO.  THE FRONT MOVES TO NORTH OF THE CWA FOR THURSDAY...BUT AM NOT
CONVINCED THAT THERE WON'T BE ANY PRECIP WITH THE SURFACE COLD
FRONT...AND HAVE HUNG ONTO PRECIP CHANCES FOR THAT TIME FRAME.  ALL
IN ALL...THIS FORECAST IS NOT A LOT DIFFERENT FROM THE GOING
FORECAST...AND WILL BE TWEAKING FOR THE MOST PART.

EXTENDED...FRIDAY THROUGH MONDAY
FRIDAY IS IN QUESTION...THERE ARE SOME TIMING CONCERNS ABOUT THE
EXITING SHORTWAVE...AND MAY EVENTUALLY NEED SOME POPS FOR EARLY
FRIDAY.  FOR NOW...CHANCES ARE LOOKING KIND OF SKIMPY SO HAVE LEFT
OUT.  OTHERWISE...A RIDGE BUILDS IN FOR SATURDAY AND EARLY
SUNDAY. GOING FORECAST FOR SATURDAY LOOKS GOOD...AND ABOVE GUIDANCE
TEMPS FOR SUNDAY ARE REASONABLE DUE TO STRONG SOUTHERLY FLOW.  CWA
MAY BE NORTH OF THE FRONT...SO DONT WANT TO GO TOO FAR. SUNDAY NIGHT
AND MONDAY THE PRECIPITATION MOVES IN AGAIN WITH THE GFS BRINGING THE
SURFACE LOW ACROSS IA.

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

$$

LE