[LeArc] Forecast Discussion : MLI@ 4/22/2003 2:49:33 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 221947
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
230 PM CDT TUE APR 22 2003

SURFACE RIDGE AXIS INTO WESTERN SECTIONS OF CWA WITH SUBSIDENCE
RESULTING IN COPIOUS AMOUNTS OF SUNSHINE...THOUGH FAIR WX
CUMULUS HAS POPPED WITH AFTERNOON HEATING IN SOUTH AND WEST ZONES.
ALOFT...RIDGE WAS LOCATED OVER THE PLAINS WHILE UPPER LOW WAS
CENTERED OVER SOUTHERN NEVADA...LIFTING OUT PER PRESSURE FALLS AND
MAIN CORE OF JET WITH 100+ KT WINDS SHIFTING TO EAST SIDE
OF CIRCULATION. THIS SYSTEM WILL BE PLAYER IN OUR WX LAST HALF OF
THE WEEK.

MAIN CONCERNS IN SHORT TERM ARE WITH MINS AND POTENTIAL FOR FROST
TONIGHT. IN LATER PERIODS...THE FOCUS SHIFTS TO THE UPPER LOW AND
ASSOCIATED PCPN CHANCES/TIMING.

TONIGHT...RIDGE AXIS WILL SLIDE EAST OVERNIGHT WITH COLDEST READINGS
EXPECTED IN EASTERN ZONES. SOME PATCHY FROST AROUND THIS MORNING
AND SHOULD SEE REPEAT PERFORMANCE MAINLY EAST OF MISSISSIPPI
RIVER CLOSER TO RIDGE AXIS...AND WILL MAKE MENTION THESE LOCATIONS.
STILL A TAD BIT EARLY TO GO WITH FROST ADVISORY WITH FREEZING TEMPS
NOT THAT FAR OFF (<10 DEGS) FROM CLIMO FOR LATE APRIL.

WEDNESDAY...WITH SOME MOISTURE AT H85 AND RELATIVELY STEEP LAPSE
RATES EXPECT TO SEE SCT CU DEVELOP TOWARD NOON. ALSO...SOME
CIRRUS...BUT BOTH SHOULD NOT BE ENOUGH TO RUIN M/SUNNY WORDING.
AS FOR MAXES...TEMPERATURES AT 19Z IN M/U60S TO NEAR 70 ON BACKSIDE
OF HIGH FROM WESTERN IA INTO EASTERN NE...AND WITH CWA IN
SIMILAR LOCATION...PLUS DECENT MIXING AND PLENTY OF LATE APRIL SOLAR
INSOLATION...WILL GO WITH SIMILAR READINGS...OR CLOSER TO WARMEST
MET GUIDANCE.

WEDNESDAY NIGHT...TOP DOWN SATURATION PROCESS BEGINS AIDED BY LEAD
IMPULSE EJECTING FROM UPPER LEVEL LOW. MODELS INDICATE
ATMOS SATURATES SUFFICIENTLY FOR PCPN IN SOUTH AND WEST ZONES...SO
WILL NEED TO INTRODUCE POPS. WILL GO WITH JUST CHC POPS
SINCE GOING FROM DRY FORECAST. 20 MB CONDENSATION PRESSURE DEFICIT
IS USUALLY GOOD INDICATOR FOR WHEN PRECIPITATION STARTS...AND
ON 295K SURFACE ETA SHOWS THIS REACHING A WASHINGTON...TO MOUNT
PLEASANT...TO FORT MADISON LINE BETWEEN BETWEEN 06Z-12Z THU...LIKELY
MORE IN THE 09Z-12Z TIMEFRAME. NORTH OF THIS LINE...TO NEAR THE
QUAD CITIES AND MONTICELLO...FEEL AT WORST MAINLY SOME SPRINKLES WITH
STILL DRY AIR TO OVERCOME IN THE LOW LEVELS. WILL KEEP FORECAST
DRY IN NORTHEAST IA AND NORTHWEST IL PER DRY LOW LEVELS.
UPPER JET STAYS SOUTH...SO EXPECT JUST RAIN WITH ANY CONVECTION
STRATIFYING OUT AS IT APPROACHES.

LOOKING FURTHER AHEAD...THE SHORT AND MEDIUM RANGE MODELS AGREE ON
A SURFACE LOW MOVING INTO WESTERN KS THURSDAY MORNING...WITH A WARM
FRONT DEVELOPING DURING THE DAY ACROSS CENTRAL MISSOURI.  THE LOW
MOVES SOUTH OF THE AREA THROUGH SOUTHERN MISSOURI ON FRIDAY...WITH
A CLOSED 500MB LOW TRAILING CLOSE BEHIND.  LOOKING AT THE
DYNAMICS...STRONG VV'S AND 300MB DIVERGENCE LIFT CONTINUE TO LIFT
ACROSS THE FORECAST AREA THURSDAY...DIMINISHING IN THE MORNING
SOUTHWEST...MIDDAY CENTRAL...AND CONTINUING THRU THE DAY NORTHEAST.
ISENTROPIC LIFT ALSO CONTINUES INTO THE MORNING...BUT IS GONE BY
MIDDAY.  MODERATE VV'S AND 300MB DIVERGENCE CONTINUE THURSDAY
NIGHT...ENDING FRIDAY MORNING SOUTHEAST.  RAINFALL TOTALS WITH THIS
EVENT HAVE THE POTENTIAL TO BE AN INCH OR MORE FROM BRL SOUTH...WITH
UP TO A HALF INCH ALONG THE I-80 CORRIDOR...AND A QUARTER INCH OR
LESS IN DBQ.

THE NEXT SYSTEM WILL LIFT OUT OF THE SOUTHERN PLAINS SUNDAY NIGHT...
FORMING AN INVERTED TROF ACROSS THE AREA.  THE TROF STAYS ACROSS
THE AREA THROUGH MONDAY NIGHT...POSSIBLY MEANDERS WEST A BIT
MONDAY...ALLOWING FOR THUNDERSTORM ACTIVITY...AND THEN KICKS EAST
ON TUESDAY. RAINFALL AMOUNTS OF A HALF INCH TO AN INCH WILL BE
POSSIBLE FROM SUNDAY NIGHT INTO TUESDAY...WITH HIGHER AMOUNTS
POSSIBLE IF CONVECTION SETS UP IN THE MONDAY TIME FRAME.

WILL STAY CLOSE TO ONGOING FORECAST...AS MODELS ARE IN FAIR
AGREEMENT FOR A CHANGE.  WILL BE GENERAL CONTINUATION OF COOLER
WEATHER FOR THE NEXT 7 DAYS...WITH TWO GOOD PRECIP CHANCES.


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

$$

REA/MWM