[LeArc] Forecast Discussion : MLI@ 1/29/03 1:18:18 PM

[learc@mailman.qth.net]

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


FXUS63 KDVN 291927
AFDMLI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
125 PM CST WED JAN 29 2003

.OVERVIEW...NEXT SURGE OF ARCTIC AIR CENTERED OVER SOUTHERN MN MOVING SE
AT 25-30 MPH.  UPPER AIR ANALYSIS SHOWS EMBEDDED UPSTREAM DISTURBANCES
IN NW JET WITH LIMITED RIDGING PER HEIGHT RISES. SATELLITE SUPPORTS THIS
WITH LOTS OF LOW CLOUDS SOUTH AND WEST OF FORECAST AREA. IMPACT OF
YESTERDAY/S SNOWCOVER EVIDENT WITH TEMPS 3-5 DEGREES LOWER THAN DRY
LOCATIONS DESPITE LOTS OF SUNSHINE AT 18Z. SURFACE RIDGE TO PASS ACROSS
AREA BETWEEN 01Z AND 07Z PER AWIPS DISTANCE TIME FEATURE...MAX
RADIATIONAL COOLING AT THOSE TIMES TONIGHT.

TIMING CLOUD RETURN TONIGHT AND IMPACTS ON TEMPS NEAR TERM ISSUE
WITH FRIDAY PRECIPITATION TYPE COVERAGE AND INTENSITY...THEN MONDAY
SYSTEM MEDIUM RANGE ISSUE...

.DIAGNOSIS AND DAYS 1-3...BIGGEST ISSUE IS NEARBY LOW CLOUDS WHICH
WILL MERGE CURRENT 18Z TRENDS WITH GFS-AVN/NGM WORKING BEST.  THUS AS
SFC HIGH SLIDES EAST WILL SEE CLOUDS RETURN MAINLY AFTER MIDNIGHT TO
SW SECTIONS. THUS LOWS MOST AREAS TO BE EARLY WITH SLOWING RISING
TEMPS DUE TO CLOUDS AND INCREASING SOUTH WINDS.  TREND SLIGHTLY BELOW
EAST AREAS TONIGHT WITH EARLY RADIATIONAL COOLING AND SNOW AND NEAR TO
JUST ABOVE SW AREAS.  TOMORROW...SOME CLEARING FROM SW BY MID DAY AND
TAKE TEMPS NEAR TO SLIGHTLY BELOW MODEL BLEND DUE TO CLOUDS AND SOME
SNOW IMPACTS MOST AREAS EXCEPT SW.  THEN...EARLY FRIDAY AM GETS TRICKY
WITH DIVING SYSTEM OUT OF NW WITH REASONABLE CONFIDENCE MOST AREAS TO
GET LIKELY POPS DUE TO GENERAL TRACK...FAVORABLE LOW LEVEL CONVERGENCE
AND FORCING. PROBLEM IS BOUNDARY LAYER TEMPS AND THUS TYPE...WILL TRY
LOOK AT 18Z ETA BUT PLAN FOR NEAR AVN/UKMET LOW LEVEL TEMPS OR RAIN WITH
SOME MIXTURE SOUTH AND MIXTURE CENTRAL AND NORTHERN AREAS WITH SNOW FAR
NE. UPDATE HWO FOR THIS EVENT BUT APPEARS POPS TO BE GENERALLY LESS THAN
1 TO 15 HUNDREDTHS...IF SIGNIFICANT ICING MORE PROBABLE THEN MID SHIFT
NEEDS TO CONSIDER ADVISORY.   NOT COMFORTABLE ETA HAS YESTERDAY/S SNOW
PROPERLY PER ETA 2M TEMPS DON/T SHOW COOLING FROM SNOWCOVER ALONG/SOUTH
HIGHWAY 30 AT 18Z.  THIS AFOREMENTIONED POINT AND NEXT SYSTEM TRIPLE
POINT PASSING TO SW SHOULD LIMIT LOW LEVEL WARMING...THUS RISKING TEMPS
STAYING COLDER THAN WARMER ETA AND EVEN A BIT COOLER THAN AVN-GFS.
AFTERWARDS...THEN...QUIET WEATHER WITH TEMPS NEAR TO SLIGHTLY ABOVE
GUIDANCE BLEND.

.EXTENDED (SUN-WED)...MODELS SUGGEST SIGNIFICANT CHANGE TO UPPER FLOW
WITH MORE LATE WINTER EARLY SPRING REGIME WITH RIDGING IN SE CONUS
FOR MORE FAVORABLE MOISTURE INFLOW (GULF OPEN) AND MAJOR STORM TRACK
OVER REGION FOR FIRST TIME QUITE A WHILE BY MONDAY.  ALL MEDIUM-RANGE
MODELS AGREE ON VIGOROUS STORM MONDAY AND THUS GO LIKELY POPS.  EXACT
LOW TRACK UNCERTAIN BUT ALL SUGGEST...LOW NEARBY OR OVER AREA FOR
COPIOUS RAINS LATE SUNDAY AND MONDAY CHANGING TO SNOW LATE MONDAY OR
EARLY TUESDAY. WILL TRY NOT GET TO SPECIFIC AND MENTION THIS FOR NW
2/3 AREA WITH JUST RAIN SE 1/3.   TYPE SYSTEM NORMALLY GENERATES
WIDESPREAD .5" TO 1.0" LIQUID OR LIQUID EQUIVALENT AMOUNTS WHICH WOULD
PUT SOME MOISTURE BACK IN OUR DRY SOIL.  UPDATE HWO HERE AS WELL...
INTERESTING TO SEE HOW MODELS RESOLVE/PHASE THINGS NEXT 2-3 DAYS.

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

NICHOLS