000
FXUS63 KMPX 272141
AFDMPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
340 PM CST MON DEC 27 2010
.DISCUSSION...
SIGNIFICANT WARM UP THE NEXT FEW DAYS....BUT WEATHER SITUATION
BECOMES COMPLICATED WEDNESDAY NIGHT AS LIGHT FREEZING PRECIPITATION
SPREADS INTO AREA FOLLOWED BY A TRANSITION TO MAINLY SNOW.
DURING THE NEXT 24 HOURS SHARP UPPER RIDGE OVER AREA BECOMES
FLATTENED AS DEEP LOW PRESSURE OFF NE COAST MOVES OUT TO SEA AND
RATHER STRONG SHORTWAVE MOVING ACROSS EXTREME SOUTHERN SASKETCHEWAN
PLOWS ACROSS MB INTO OT. THIS ALLOWS MILD PACIFIC FLOW TO INFILTRATE
THE AREA. THIS ALLOWS TEMPERATURES TOMORROW TO RISE 6 TO 10 DEGREES
ABOVE TODAYS LEVELS WITH A FURTHER RISE ON WEDNESDAY AS WE BEGIN TO
TAP A SOUTHERLY STREAM. SHOULDN'T SEE MUCH FOR CLOUDS
TONIGHT...EXCEPT SC MN INTO WI BEING BRUSHED BY MVFR CLOUDS NOW
ACROSS W IA INTO THE FRM AREA.
MODELS CONSISTENT IN DEVELOPING A LARGE AMPLITUDE UPPER TROUGH TO
THE LEE OF THE ROCKIES BY EARLY THURSDAY...BUT STILL SIGNIFICANT
DIFFERENCES IN HOW THE WEATHER UNFOLDS AS SYSTEM EJECTS. BOTH THE
ECMWF AND GFS SOLUTIONS BRING IN A MOIST SOUTHERLY FETCH WEDNESDAY
NIGHT WITH FZDA OR -FZRA...STRATUS AND FOG A LIKELY OUTCOME.
SHORTWAVE EJECTING FROM DIGGING UPPER TROUGH BRINGS THE FIRST WAVE
OF MORE SIGNIFICANT PRECIPITATION ON THURSDAY WITH THE BEST FORCING
ACROSS WC INTO CENTRAL MN. BY THE TIME THIS EVENT ARRIVES THERE
SHOULD BE SUFFICIENT WARMING (THICKNESS CONSIDERATIONS AND
TEMPERATURES PROFILES) FOR PRECIP TO BE MAINLY RAIN...WITH FREEZING
RAIN POSSIBLE MAINLY NW CWA DURING THE MORNING.
WHERE MAIN DIFFERENCE OCCURS BETWEEN ECMWF AND GFS IS WITH HANDLING
OF SECOND WAVE OF PRECIP. GFS MUCH MORE AGGRESSIVE ON DEVELOPING A
SECOND STRONGER SURFACE LOW IN OK THURSDAY NIGHT AND THEN EJECTING
IT RAPIDLY NE INTO WC WI BY FRIDAY EVENING. THIS SOLUTION WOULD
FAVOR MAINLY A SNOW EVENT FOR FRIDAY ACROSS MOST OF THE MN CWA AS
COLD AIRMASS IS DRIVEN FARTHER EAST. THE CANADIAN GEM SOLUTION IS
SIMILAR TO THE GFS. ECMWF HOWEVER STILL KEEPS THIS SECOND SURFACE
LOW FARTHER WEST KEEPING SIGNIFICANT SNOW CHANCES TO OUR NW. NOT A
LOT OF CONFIDENCE AT THIS POINT ON HOW FRIDAY WILL PAN OUT IN TERMS
OF PCPN AMOUNT AND TYPE.
ALL MODEL SOLUTIONS HOWEVER BEGIN TO PLOW A SLUG OF VERY COLD AIR
ACROSS THE REGION BEGINING ON FRIDAY/FRIDAY NIGHT WITH VERY STRONG
NW WINDS. WITH POTENTIAL OF STRONG WINDS...ANY SNOW COULD BECOME
PROBLEMATIC.
COLD THEN THRU THE WEEKEND WITH SOME MODERATION MONDAY. ONCE THE
ABOVE SYSTEM EXITS LATE FRIDAY/EARLY SATURDAY THE REMAINDER OF THE
WEEKEND INTO EARLY NEXT WEEK LOOKS QUIET.
&&
.AVIATION... /18Z TAF ISSUANCE/
THE TAF PERIOD BEGINS WITH VFR CONDITIONS AT ALL TAF SITES AS
AN INCREASING SURFACE PRESSURE GRADIENT HAS HELPED MIX OUT THE
STRATUS OVER THE REGION FROM EARLIER THIS MORNING. THE GRADIENT IS
TIGHTEST THIS AFTERNOON FROM KRWF THROUGH KAXN WHERE SOUTHERLY
WINDS AT 15 TO 20 KNOTS ARE LIKELY. MNDOT WEBCAMS WEST OF THESE
TWO TAF SITES SHOWING SOME BLOWING/DRIFTING SNOW WITH SURFACE
VISIBILITY BEING IN THE MVFR RANGE. DIDN'T INDICATE THIS POTENTIAL
FOR THESE TWO SITES AS THEIR VISIBILITY HAS HELD BETTER THAN 6
MILES THIS MORNING WITH 15+ KNOT SUSTAINED WINDS.
SOME LOW CLOUD CONCERNS REMAIN IN THE FORECAST PERIOD AHEAD. A
PACIFIC WARM FRONT OVER THE CENTRAL DAKOTAS ATTM WILL BE MOVING
ACROSS THE MN/WI TAF SITES THIS EVENING. SOME LOW LEVEL MOISTURE
IS INDICATED...BUT DON'T FEEL STRONGLY ON MVFR CEILINGS. NAM
275-280 THETA SURFACES ARE NOT SHOWING MUCH IN THE WAY OF SATURATION
OR ADIABATIC OMEGA. HOWEVER...THERE ARE SOME LOW CEILINGS IN
EASTERN NEBRASKA RIGHT NOW...BUT THE TREND THIS MORNING WAS FOR A
SLOW EASTWARD MOVEMENT. THE VSREF AND HRRR WERE OF LITTLE USE AS
THEY DIDN'T FORECAST THE CLEARING THIS MORNING AND KEEP THE AREA
WITH MVFR OR LESS CONDITIONS THROUGH THEIR FORECAST PERIOD. IN THE
END...DID INDICATE SOME SCT015 FOR KRWF ON NORTHEAST THROUGH THE
TWIN CITIES AND KRNH AND KEAU. WITH THE PASSAGE OF THE WARM
FRONT...SURFACE WINDS WILL BECOME MORE WSW WITH SPEEDS OVERNIGHT
AND TUESDAY MORE NEAR 10 KNOTS.
KMSP...SHOULD BE ABLE TO MAINTAIN VFR CONDITIONS THROUGH THIS
EVENING...IF NOT THROUGH THE ENTIRE TAF PERIOD. SMALL
PROBABILITIES FOR BKN015 DURING THE LATE EVENING/OVERNIGHT
HOURS...PRIMARILY AFTER 28/04Z...BUT CONFIDENCE NOT HIGH. SE SURFACE
WINDS EARLY THIS AFTERNOON BECOMING MORE SOUTHERLY (180-200) BY
THIS EVENING AND THEN SW (230-250) OVERNIGHT AND TUESDAY. SPEEDS
IN THE 7 TO 12 KNOT RANGE.
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
BAP/RAH
