FXUS63 KMPX 041204
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
345 AM CST FRI DEC 4 2009

.DISCUSSION...

FORECAST CONCERN NEAR TERM IS THE CONTINUING THREAT OF SNOW
SHOWERS OVER MAINLY THE NORTHERN PORTION OF THE CWA DURING THE
DAY. MODELS CONTINUE TO TREND WHAT APPEARS TO BE VIGOROUS VORT
MAXIMA ROTATING VCNTY OF LAKE WINNIPEG THIS MORNING. TREND OF THE
NAM_WRF WAS TO INTENSIFY IT A BIT AS IT MOVES SOUTH SOUTHEAST
DURING THE AFTERNOON/EVENING. SOME DECENT LIFT/Q VECTOR
CONVERGENCE MOVES OVER THE NORTHEAST CWA THIS AFTERNOON/EVENING.
THIS IS ENOUGH FOR CHANCE POPS OVER THE NORTHERN AREA FOR MORE
SNOW SHOWERS TODAY. CLOUDS DID BREAK OPEN OVER THE SOUTHWEST IN
THE WAKE/SUBSIDENCE OF THE PREVIOUS SHORT WAVE. THIS PROVIDED NICE
TEMP DROP IN LIGHTLY SNOW COVERED REGION OF THE SOUTHWEST. SHOULD
SEE CLOUDS MOVE BACK IN EARLY THIS MORNING AS NEXT WAVE
APPROACHES. SOME WEAK CAA CONTINUES INTO THIS MORNING AND WITH
EXPECTED CLOUDS...LITTLE RISE IN TEMPERATURES EXPECTED. WENT WITH
A COLDER NAM GUIDANCE TEMPERATURES CONSIDERING TRAJECTORY OF
AIRMASS FROM YESTERDAY.

SYSTEM EXITS TO THE EAST OF THE AREA OVERNIGHT. SHOULD SEE SOME
CLEARING OVER THE WESTERN AND CENTRAL CWA DURING THE NIGHT. CLOUDS
MAY HANG INTO WC WI THROUGH THE NIGHT AS SFC RDG BUILDS INTO THE
WESTERN CWA. UNCLEAR HOW MUCH CLOUD COVER WILL BE AROUND SAT AND
SUNDAY AS TROUGH SHEARS OFF TO THE EAST. TEMPERATURES WILL BE
DE PENDANT OF CLOUD COVER INTO SUNDAY...SO WENT CLOSE TOM MAV
NUMBERS FOR NOW. MODELS DIVERGE SOMEWHAT ON HANDLING OF NEXT SHORT
WAVE TROUGH FOR SUN NIGHT INTO MONDAY. GFS HOLDS THE WAVE A BIT
FARTHER SOUTH THAN PREVIOUS RUNS...WITH THE COLD SFC HIGH WINNING
OUT ACROSS THE AREA. THE 00Z NAM_WRF AND 00Z ECMWF CONTINUE TREND
OF CLIPPING THE FAR SOUTHERN CWA WITH THIS SYSTEM. WILL TRIM POPS
A BIT TO THE NORTH BUT CONTINUE THE CHANCE POPS OVER THE FAR
SOUTHERN CWA. 

LONGER TERM...MODELS HAVE BEEN TRENDING TOWARD DEVELOPMENT OF
SIGNIFICANT LONG WAVE TROUGH OVER THE NATIONS MIDSECTION TOWARD
MIDWEEK. 00Z RUNS CONTINUE THE TREND OF SIGNIFICANT CYCLOGENESIS
NEAR THE CO/OK PANHANDLE REGION LATE TUE AND LIFTING NORTHEAST TO 
SOUTHERN LK MICHIGAN REGION BY WED MORNING. THIS TRACK WOULD
AFFECT MAINLY OUR SOUTHERN CWA AS THE LOW TRACKS SOUTH AND EAST.
THE HEAVIER SNOWS WOULD CLIP OUR SOUTHERN CWA WITH THE HEAVIEST SNOW
BAND OVER IOWA AND WI. THIS COULD BE OUR FIRST SIGNIFICANT STORM
OF THE SEASON AND WILL HIGHLIGHT THIS THREAT IN THE HWO.

&&

.AVIATION.../06Z TAF ISSUANCE/ 

MAIN AVIATION CONCERN IS TIMING OF NEXT -SN EVENT TODAY AND HOW
LOW TO DROP VSBYS. VSBYS HAVE BEEN MOSTLY VFR THIS EVENING...WHICH
SHOULD CONTINUE THROUGH MOST OF THE TAF SITES THRU 09/12Z...AXN/STC
WILL BEGIN TO SEE SLIGHTLY LOWER CEILINGS/VSBY AS THE NEXT WAVE
BEGINS TO AFFECT THIS REGION. 

CEILINGS HAVE BEEN PROBLEMATIC WHICH IS ANOTHER CONCERN LATER
TODAY AS MOISTURE LEVELS REMAIN HIGH BELOW 85H...AND ANY DIURNAL
HEATING WILL AID IN CLD DEVELOPMENT. IN ADDITION...ANOTHER WAVE
WILL BEGIN TO AFFECT THE TAFS BY LATE MORNING/AFTN WITH VSBYS AS
LOW AS 2SM...ESPECIALLY FOR STC/MSP/RNH/EAU WHERE BEST LIFT AND
DEEPER MOISTURE WILL RESIDE. 

HAVE CONTINUED MVFR CEILINGS FOR THE MOST PART...BUT THERE COULD
BE A TEMPORARY PERIOD OF IFR CEILINGS IF THE SNOWFALL IS LOCALLY
HEAVY. NOT ANTICIPATING ANYTHING TOO DRASTIC AS UPSTREAM
CONDITIONS IN SOUTH CENTRAL CANADA REMAIN MVFR...WITH BRIEF
PERIODS OF IFR VSBYS. AFT 00Z/05...CONDITIONS SHOULD GRADUALLY
IMPROVE AS DRIER AIR WILL BEGIN TO FILTER ACROSS THE DAKOTAS...AND
INTO WESTERN MN. ..JLT..

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&

$$

DWE/JLT