[LeArc] Forecast Discussion : MLI@ 3/29/2003 3:41:21 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 292136
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
335 PM CST SAT MAR 29 2003

RADAR WELL LIT UP THIS AFTERNOON WITH NUMEROUS SNOW SHOWERS...SOME
OF THEM REDUCING VISIBILITIES TO LESS THAN A MILE...WITH LIGHT
ACCUMULATIONS OF ABOUT A TENTH OF AN INCH.  SNOW MELTING QUICKLY AS
IT HITS THE GROUND...SO AS SOON AS THE SUN BREAKS OUT AGAIN THE SNOW
IS GONE.  LAPSE RATES THIS AFTERNOON OFF OF RUC SOUNDINGS WELL OVER
7C/KM THROUGH MOST OF THE LOWER LAYERS...HELPING TO KICK OFF THE
SHOWERS.  ALSO THERE IS A VORT MAX DROPPING ACROSS THE AREA...WHICH
SHOULD EXIT THE AREA EARLY THIS EVENING.

MAIN FORECAST PROBLEM IS PRECIP CHANCES NEXT FEW DAYS AND WARMING
TREND FOR MID WEEK.

12Z MODELS APPEAR TO HAVE INITIALIZED REASONABLY WELL...THOUGH THE
AVN HAS THE BEST HANDLE ON THE PRECIPITATION CURRENTLY ONGOING OVER
EASTERN IOWA AND ILLINOIS.  HAVE LEANED PRETTY HEAVILY ON IT
THROUGH THE FORECAST PERIOD.

TONIGHT WITH THE RIDGE TO THE WEST OF THE AREA...THE MAIN QUESTION
IS HOW MUCH SKIES WILL CLEAR AFTER THE SNOW SHOWERS SHUT OFF.  MID
LEVEL RH QUICKLY EXITS OFF TO THE EAST DURING THE EVENING...THINK
THAT RH IS NOT BEING WELL HANDLED TODAY...AND HAVE DECIDED TO HANG
ONTO CLOUDS A LITTLE LONGER THAN INDICATED...AND WILL BE GOING WITH
MOSTLY CLOUDY DURING THE EVENING AND GRADUAL CLEARING AFTER MIDNIGHT.
THIS BRINGS UP THE QUESTION OF LOW TEMPS.  CLOUDS MOST OF THE
NIGHT...AM LOOKING AT MID 20S FOR LOWS.  CLOUDS CLEAR OUT BY 9 PM...
AM LOOKING AT UPPER TEENS.  WITH GOING THINKING ON CLOUD TRENDS AM
GOING TO SPLIT THE DIFFERENCE AND GO WITH TEMPS IN THE LOW 20S.

SUNDAY WILL BE TRICKY...AS THERE ARE FAIRLY GOOD INDICATIONS THAT
THERE WILL BE MORE SNOW SHOWERS DURING THE AFTERNOON.  THERE ARE
GOOD MID LEVEL LAPSE RATES...AND WHILE THERE WILL BE LESS MOISTURE
THAN TODAY...AND THE UPPER LEVEL DYNAMICS ARE NOT QUITE AS GOOD...
THINK FLURRIES FROM THE AFTERNOON CU THAT SHOULD POP ARE QUITE
LIKELY...AND PERHAPS EVEN THE SHOWERS WITH A DUSTING OF
ACCUMULATION LIKE TODAY.  HAVE GONE WITH 20 POPS EAST AND 10 WEST...
ASSOCIATED WITH THE BEST LAPSE RATES.  850 TEMPS WARM ENOUGH THAT
THERE MIGHT BE SPRINKLES WITH THESE SHOWERS...ESPECIALLY LATE IN THE
AFTERNOON.

SUNDAY NIGHT AND MONDAY ARE QUIET...WITH THE SURFACE RIDGE AGAIN
KEEPING WINDS LIGHT FOR SUNDAY NIGHT.  MONDAY SOUTHWESTERLY FLOW
KICKS IN AGAIN...AND TEMPS JUMP QUITE A BIT OVER SUNDAY.  HAVE GONE
CLOSE TO GOING FCST...THOUGH HAVE COOLED OFF THE NORTHERN ZONES A
LITTLE. A SURFACE WARM FRONT DEVELOPS JUST NORTH OF THE AREA...AND
BEFORE IT SHIFTS EVEN FARTHER NORTH...THERE MAY BE SOME LIGHT RAIN
ALONG IT FOR THE FAR NORTHERN COUNTIES MONDAY EVENING. HAVE KEPT POPS
LOW.

TUESDAY IS IN QUESTION AS THE SURFACE FRONT MAY SAG SOUTH AGAIN TO
AFFECT THE NORTHERN COUNTIES. HAVE DECIDED TO LEAVE OUT POPS FOR
NOW...AS THIS HAS NOT BEEN WELL HANDLED BY MODELS...THOUGH AN
INCREASE IN CLOUDS WARRANTED. SOUTHWEST WINDS WILL BEGIN TO REALLY
WARM THE SOUTHERN COUNTIES...AND THERE WILL BE QUITE A GRADIENT FROM
NORTH TO SOUTH.

EXTENDED...WED-SAT
VERY CHANGEABLE PATTERN...WITH THE DIFFERENCE BETWEEN YESTERDAY AND
TODAY FOR THE FRIDAY AND SATURDAY FORECAST RATHER LARGE. ON
YESTERDAYS RUN THE GFS RAN A SURFACE LOW FROM NERN CO THROUGH IOWA TO
SRN WISCONSIN.  THE NEW RUN IS MUCH FASTER AND FURTHER NORTH...
INSTEAD MOVING ACROSS NORTH DAKOTA...MINNESOTA...AND NORTHERN
WISCONSIN LATE ON THURSDAY.  THIS CHANGE HAS PRODUCED HIGHER POPS
ON THE MRF MOS FOR THE CWA DURING THIS TIME FRAME.  OTHER EXTENDED
RANGE MODELS AGREE WITH THE FASTER TIMING...BUT ARE FURTHER SOUTH
RUNNING THE SURFACE LOW ACROSS THE NORTHERN IOWA/SOUTHERN MINNESOTA
AREA.  DO NOT YET BUY INTO THIS NEW SOLUTION...AND WILL ONLY ADD
PRECIP TO THURSDAY NIGHT AND FRIDAY. A NEW SYSTEM DEVELOPS OVER THE
HIGH PLAINS TO AFFECT SATURDAY...BUT LATE IN THE PERIOD. WILL
CONTINUE THE TREND EARLIER SET BY HAVING WARMER THAN GUIDANCE TEMPS
FOR WEDNESDAY AND THURSDAY...THEN COOLING AGAIN FOR FRIDAY AND
SATURDAY.

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

$$

LRE