FXUS63 KMPX 281146
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
546 AM CST SAT NOV 28 2009

.DISCUSSION...

OVERALL A TRANQUIL PERIOD INTO EARLY NEXT WEEK WITH A FEW MINOR
PRECIP CHANCES THROUGH THE MIDDLE OF NEXT WEEK. TEMPERATURES WILL
BE THE MAIN ITEM OF INTEREST WITH SOME UPS AND DOWNS INTO EARLY
NEXT WEEK BEFORE MUCH COLDER AIR ARRIVES BY MIDWEEK. GENERAL AIR
FLOW PATTERN WILL BE ACTIVE THROUGH THE PERIOD BUT THERE IS PRETTY
GOOD CONFIDENCE IN THE OVERALL EVOLUTION DURING THAT TIME. EARLY
MORNING MOISTURE CHANNEL IMAGERY SHOWS FAIRLY FLAT UPPER RIDGING
OVER THE CENTRAL U.S. WITH A ZONAL FLOW OVER THE MID SECTION OF
SOUTHERN CANADA. THE TROUGH THAT HAS BEEN SLOWLY WORKING EASTWARD
ACROSS THE GREAT LAKES AND NORTHEAST THE LAST SEVERAL DAYS IS
MAKING PROGRESS TOWARDS THE GULF OF ST. LAWRENCE. BACK TO THE
WEST...A DEEP CLOSED LOW HAS COME ON SHORE OVER CALIFORNIA WIT A
TROUGH AXIS EXTENDING TO ITS NORTH. THE FLOW ASSOCIATED WITH THIS
TROUGH IS BEGINNING TO SPLIT OVER IDAHO WITH THE CALIFORNIA LOW
BECOMING CUTOFF. TO THE NORTH OF THIS LOW IN THE NORTHERN
STREAM...A SHORTWAVE IS EVIDENT MOVING ACROSS CENTRAL SASKATCHEWAN
AND WILL BE AFFECTING THE LOCAL WEATHER TONIGHT AND SUNDAY.

TODAY THROUGH SUNDAY...WEAK SFC FRONTAL BOUNDARY WHICH APPROACHED 
THE FORECAST AREA LAST NIGHT HAS SLOWED TO A CRAWL ACROSS CENTRAL MN 
THIS MORNING. THE APPROACH OF THE SHORTWAVE FROM SASKATCHEWAN WILL 
HELP INCREASE THE EASTWARD PROGRESS OF THE FRONT THIS AFTERNOON BUT 
UNTIL THEN LIGHT SOUTH FLOW WILL BE FOUND ACROSS THE EASTERN HALF OF 
THE AREA WITH LIGHT NORTH FLOW ACROSS THE WEST THIS MORNING BEFORE 
INCREASING INTO THE AFTERNOON. LOW LEVEL TEMPS HAVE MODIFIED 
SLIGHTLY WITH H85 TEMPS IN THE +4 TO +8 RANGE OVER THE AREA BUT THE 
APPROACHING TROUGH WILL HELP THOSE TO START COOLING BY EVENING. 
ABUNDANT CIRRUS CONTINUES TO STREAM NORTHEASTWARD ON THE BACK SIDE 
OF THE WEAK UPPER RIDGE KEEPING THE NORTHERN CWA UNDER THE MOST 
PERSISTENT COVERAGE WITH MORE VARIABLE CIRRUS COVER OVER THE SOUTH 
TODAY. HIGHS SHOULD MAKE IT INTO MID 40S WITH A BIT MORE UNIFORM 
DISTRIBUTION ACROSS THE CWA THAN YESTERDAY. THE SASKATCHEWAN TROUGH 
WILL MOVE INTO WESTERN MN TONIGHT. RIGHT ENTRANCE REGION OF 100 KT 
UPPER JET WILL MOVE ACROSS THE SOUTHERN THIRD OR SO OF MN THIS 
EVENING/TONIGHT AS BAND OF Q-VECTOR CONVERGENCE SWINGS ACROSS THE 
SAME AREA. THE GFS IS MOST AGGRESSIVE WITH MAGNITUDE OF 
FRONTOGENESIS THAT DEVELOPS AND SWINGS ACROSS THE AREA WITH GOOD 
FORCING ON THE -15C ISOTHERM SFC...WHICH IS LIKELY A BIT OVERDONE. 
NAM AND CANADIAN ARE MORE MUTED WITH THE FORCING. EVEN IF THE 
STRONGER FORCING DOES PAN OUT THE MOISTURE IS THE MAIN LIMITING 
FACTOR. WITH THE FORCING FOCUSED FAIRLY HIGH IN THE ATMOSPHERE AND 
MEAGER MOISTURE BELOW IT...SO MEAGER THAT COLUMN SATURATION IS 
UNLIKELY...IT WILL BE DIFFICULT TO GET MUCH SNOW TO THE GROUND. WILL 
GO AHEAD AND ADD SLIGHT AND LOW CHANCE POPS ALONG AND NORTH OF A 
LINE FROM MORRIS TO NEW RICHMOND TO LADYSMITH WITH THE HIGHEST POPS 
FROM ABOUT LONG PRAIRIE TO ST. CLOUD TO AMERY. THESE AREAS HAVE THE 
POTENTIAL TO SEE A BAND OF LIGHT SNOW MOVE ACROSS THIS EVENING AND 
TONIGHT. IF THE BAND CAN DEVELOP THEN A DUSTING/COATING OF SNOW IS 
POSSIBLE...ESPECIALLY ACROSS THE FAR NORTH. THE WEAK SFC LOW OVER 
THE AREA WILL SHIFT OFF TO THE EAST THEN INTENSIFY AS THE UPPER 
TROUGH ARRIVES WHICH WILL TIGHTEN THE SFC PRESSURE GRADIENT TONIGHT 
INTO SUNDAY MORNING. THIS WILL RESULT IN BRISK NORTHWESTERLY WINDS 
FOR AT LEAST THE FIRST PART OF SUNDAY. THE PASSAGE OF THE TROUGH 
WILL BRING SHARP COLD ADVECTION AS H85 TEMPS FALL TO -6 TO -8 C BY 
MIDDAY SUNDAY. HIGHS WILL RANGE FROM THE UPPER 30S TO AROUND 40. 

SUNDAY NIGHT THROUGH THURSDAY...THE UPPER TROUGH WILL CONTINUE TO 
INCREASE IN SCALE AS IT PHASES WITH AN UPPER LOW DEVELOPING OVER 
JAMES BAY. THE CALIFORNIA CUTOFF LOW WILL DRIFT SOUTHEASTWARD INTO 
NORTHERN MEXICO BY MONDAY AS RIDGING BUILDS IN TO ITS NORTH. FAST 
NORTH-NORTHWEST FLOW WILL BE OVERHEAD LOCALLY MONDAY BEFORE THE 
RIDGING WORKS EASTWARD TOWARDS THE AREA. A WEAK SHORTWAVE WILL ZIP 
ACROSS THE AREA MONDAY BUT ONLY LOOKS TO BRING AN INCREASE IN CLOUD 
COVER. A STRONGER TROUGH WILL MOVE INTO THE NORTHERN STREAM ACROSS 
ALBERTA AND SASKATCHEWAN RESULTING IN A DEVELOPING SFC LOW ACROSS 
THE CANADIAN PRAIRIES INTO TUESDAY. GFS/ECMWF/NAM/UKMET HAVING 
TROUBLE AGREEING ON WHAT HAPPENS WITH THIS SYSTEM. RUN TO RUN 
CONTINUITY HAS VARIED WITH THE GFS EXHIBITING SOME CONSISTENCY WITH 
MAGNITUDE OF THE SFC LOW /SUB 995 MB/ AND SPEED WHILE THE ECMWF HAS 
TRENDED WEAKER FOR SEVERAL RUNS BUT IS NOW COMING IN STRONG AND 
CLOSER TO THE GFS WITH ITS 28/00Z RUN. WHILE THE DETAILS ARE 
UNCERTAIN AT THE MOMENT THE BIGGER PICTURE IS A BIT MORE CLEAR. WITH 
THE TROUGH APPROACHING...WARM ADVECTION WILL COMMENCE OVER THE 
REGION SO FEEL PRETTY CONFIDENT THAT THERE WILL BE AT LEAST A SLIGHT 
WARMUP FOR TUESDAY. THE MODELS DO AGREE THAT THE APPROACHING UPPER 
TROUGH WILL PHASE WITH LOW HEIGHTS OVER JAMES/HUDSON BAY AND EVOLVE 
INTO A LARGE TROUGH OVER EASTERN CANADA AND THE EASTERN U.S. 
WEDNESDAY AND THURSDAY WITH A LONGWAVE RIDGE TO ITS WEST. THIS 
PATTERN WILL SUPPORT THE ADVECTION OF SOME OF THE COLDEST AIR YET 
THIS SEASON WITH H85 TEMPS STILL LOOKING TO FALL TO COLDER THAN -12 
C OR SO WEDNESDAY AND THURSDAY. IN TERMS OF PRECIPITATION...THIS 
CLIPPER TYPE SYSTEM WILL HAVE ITS FORCING FOCUSED MOSTLY TO THE 
NORTH OF THE AREA AND BE MOISTURE STARVED SO RIGHT NOW MINIMAL 
SNOWFALL LOOKS TO OCCUR TO THE SOUTH OF THE LOW TRACK. THAT COMBINED WITH 
THE UNCERTAINTY OF THE MAGNITUDE AND TRACK RESULTS IN CONTINUATION 
OF MINIMAL POPS ACROSS THE NORTHERN CWA INTO WEDNESDAY WITH THE 
CYCLONIC FLOW AND COLD ADVECTION ON THE BACK SIDE OF THE LOW.  
..MDB..

&&

.AVIATION.../12Z TAF ISSUANCE/ 

A SURFACE TROUGH ACROSS THE ST CROIX RIVER VALLEY AT 12Z THIS
MORNING WILL SHIFT EAST OF THE TAF SITES BY 15Z ALLOWING FOR NNW
WINDS TO GRADUALLY INCREASE INTO THIS AFTN. MVFR FOG ALONG THE
TROUGH WILL LAST THROUGH 15Z AT MOST TAF SITES WITH SOME PATCHY
IFR FOG POSSIBLE NEARBY TO SOME OF THE OUTLYING AIRFIELDS. SCT
MID AND BKN HIGH CLOUDS TO PREVAIL TODAY BEFORE THICKENING AND
LOWERING ENSUES TONIGHT AHEAD OF AN UPPER LEVEL SHORT WAVE FROM
THE NW. CORRIDOR OF ASCENT WITH THIS WAVE PASSES FROM WEST TO EAST
OVER THE TAF SITES FROM 04Z TO 12Z...AND OVERLAP WITH DEEP
MOISTURE IS EVEN A SMALLER WINDOW. AT NRN AND ERN TAF SITES HAVE
MENTIONED THE BRIEF POSSIBILITY OF SNOW DURING THOSE TIME WINDOWS
WITH MOST CONFIDENCE AT KRNH. AT THIS TIME HELD OFF MENTION OF
ANYTHING AT KMSP. ANY SNOW WOULD BE LIGHT. NW WINDS WILL DROP
SLIGHTLY THIS EVE THEN HOLD STEADY TONIGHT AT 6 TO 9 KTS BEFORE
INCREASING WITH POSSIBLE GUSTS DURING THE DAY SUNDAY.

&&

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

$$

MDB/MTF