FXUS63 KMPX 042116
AFDMPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
316 PM CST FRI DEC 4 2009
.DISCUSSION...
MAIN CONCERN DURING THE SEVEN DAY FORECAST REVOLVES AROUND A
POTENTIAL SIGNIFICANT SNOW EVENT FOR PORTIONS OF THE FORECAST AREA
TUESDAY INTO WEDNESDAY. MORE ON THAT IN A BIT.
IN THE SHORT TERM...FLURRIES AND SNOW SHOWERS CONTINUE TO STREAM
SE ACROSS MUCH OF THE FA AHEAD OF A SHORT WAVE ENTERING NW MN.
THIS FEATURE WILL MOVE ACROSS THE CWA TONIGHT. BEST LAYER
MOISTURE...ISENTROPIC OMEGA AND 400 MB PV ADVECTION IS SHOWN
ACROSS WEST CENTRAL WI EARLY TONIGHT. THIS IS ALSO WHERE THE SREF
PROBABILITY FOR MEASURABLE PRECIP IS HIGHEST. WILL USE SCT SNOW
SHOWERS FOR THIS AREA WITH UP TO A HALF INCH OF ACCUMULATION. KEPT
FLURRIES ACROSS THE MN CWA FOR MUCH OF THE NIGHT. A WEAK RIDGE OF
HIGH PRESSURE ACROSS THE EASTERN DAKOTAS WILL MOVE IN OVERNIGHT. A
DECREASE IN CLOUDINESS IS EXPECTED AS A RESULT WITH MORE OVERNIGHT
LOWS IN THE SINGLE DIGITS ACROSS MUCH OF THE MN CWA.
THE LOW LEVEL FLOW WILL TURN MORE SOUTHERLY ON SATURDAY AHEAD OF A
LOW PRESSURE SYSTEM FORMING OVER THE NORTHERN PLAINS. THE SURFACE
LOW IS IN RESPONSE TO AN UPPER LEVEL LOW DROPPING SE FROM BRITISH
COLUMBIA. A HALF WAY DECENT DAY IS EXPECTED TOMORROW WITH
AFTERNOON HIGHS IN THE MIDDLE TO UPPER 20S. CLOUDINESS WILL BEGIN
TO THICKEN ACROSS THE NORTHERN PORTIONS OF THE FA DURING THE
AFTERNOON AS MID FRONTOGENESIS BEGINS.
THE SURFACE LOW WILL SLIDE OFF TO OUR EAST SATURDAY NIGHT AND
SUNDAY AS THE UPPER LOW TO OUR WEST SHEARS APART. A SHORT WAVE FROM
THE UPPER LOW IS NOW PROJECTED TO PASS FURTHER SOUTH OF US SUNDAY
NIGHT AND EARLY MONDAY BY ALL OF THE DETERMINISTIC RUNS TODAY.
THIS HAS NOW PUSHED THE BULK OF THE PRECIPITATION INTO THE FAR
SOUTHERN REACHES OF MN FOR SUNDAY NIGHT. THE GFS ENSEMBLE FOR THE
PAST TWO DAYS HAS BEEN SHOWING VERY LOW PROBABILITIES FOR
MEASURABLE PRECIPITATION TO OUR SOUTH AND THIS IS STARTING TO
LOOK MORE AND MORE LIKE THE CASE. WITH THE SYSTEM STILL 48 TO 60
HOURS AWAY...WAS CAREFUL TO NOT LOWER POPS TO MUCH OVER SOUTHERN
MN. MAIN CHANGE WAS TO ELIMINATE POPS ACROSS CENTRAL AREAS OF
MN...ESPECIALLY FROM KSTC TO KAXN ON NORTH.
IN THE WAKE OF THIS FEATURE ON MONDAY...A 1044 MB HIGH IS
FORECAST OVER SOUTHERN ALBERTA WITH SUBSTANTIAL RIDGING ACROSS THE
NORTHERN PLAINS AND UPPER MISSISSIPPI VALLEY. WHAT THIS TRANSLATES
INTO IS MORE LOW LEVEL COLD AIR FOR THE BEGINNING OF NEXT WEEK
WITH 850 MB TEMPERATURES VERY SIMILAR TO WHAT WE HAVE HAD THE PAST
TWO DAYS. HENCE...MORE LOWS IN THE SINGLE DIGITS WITH HIGHS IN THE
TEENS AND LOWER 20S.
BEYOND MONDAY...A STRONG SHORT WAVE IS SHOWN BY THE ECMWF...GFS
AND CANADIAN TO PASS ACROSS THE FOUR CORNERS AREA ON TUESDAY AND
REACH THE TN AND OH VALLEYS ON WEDNESDAY. TIMING AND DEPTH IS NOT
TOO BAD FOR A FEATURE 120 HOURS OUT. SURFACE LOW PRESSURE IS
PROJECTED FROM THE OK PANHANDLE TO IN/OH FROM TUESDAY INTO
WEDNESDAY. THIS PLACES THE SOUTHEAST HALF OF THE FORECAST AREA IN
A FAVORABLE AREA FOR SNOW ACCUMULATION...ALTHOUGH THE ECMWF AND
CANADIAN WOULD FAVOR THE HEAVIEST SNOW WELL TO OUR SOUTH WHILE
THE GFS IS A FURTHER NORTH AND WOULD FAVOR AREAS TO THE SOUTH AND
EAST OF THE TWIN CITIES. PLENTY WILL CHANGE BETWEEN NOW AND THEN
BUT FOR NOW HAVE RAISED POPS INTO THE LIKELY CATEGORY FOR TUESDAY
NIGHT TO THE EAST AND SOUTH OF THE TWIN CITIES WITH CHANCE POPS TO
THE WEST AND NORTH.
THE FORECAST PERIOD ENDS WITH HIGH PRESSURE BUILDING IN FOR
THURSDAY AND FRIDAY WITH MORE BELOW NORMAL TEMPERATURES FOR BOTH
DAYS.
&&
.AVIATION... /18Z TAF ISSUANCE/
UPPER LEVEL LOW PRESSURE CONTINUES TO BRING SNOW SHOWERS TO ALL
BUT KRWF THIS AFTERNOON. CEILINGS AND VISIBILITY ARE HIGHLY
VARIABLE WITH CIGS PRIMARILY MVFR AND VISIBILITY MOSTLY VFR
OUTSIDE OF SNOW SHOWERS BUT IFR/MVFR IN SNOW SHOWERS. LIGHT FLUFFY
ACCUMULATIONS CONTINUE UNDER THE MORE INTENSE SNOW SHOWERS. SNOW
SHOWERS WILL DIMINISH FROM WEST TO EAST LATE THIS AFTERNOON AND
EARLY THIS EVENING. EXPECT CEILINGS TO IMPROVE TO VFR FROM WEST TO
EAST THIS EVENING AND OVERNIGHT AS DRIER LOW LEVEL AIR MOVES IN.
SCATTERED LOW CLOUDS MAY DEVELOP SATURDAY MORNING. WEST SOUTHWEST
WINDS WILL CONTINUE THIS AFTERNOON BEFORE BECOMING SOUTHERLY
TONIGHT THEN SOUTHEASTERLY SATURDAY MORNING.
KAXN...LIGHT SNOW CONTINUES BUT COVERAGE WILL BE DECREASING OVER
THE NEXT FEW HOURS LEADING TO IMPROVING VISIBILITY. MVFR CEILINGS WILL
CONTINUE WITH IMPROVEMENT TO VFR EXPECTED BY EARLY THIS EVENING.
MID AND HIGH CLOUDS WILL REMAIN OVER THE AREA TONIGHT.
KSTC...LIGHT SNOW SHOWERS WILL CONTINUE THROUGH THE AFTERNOON.
EXPECT VISIBILITY PRIMARILY IN THE 3 TO 5 SM RANGE IN -SN BUT A
BRIEF DROP TO 2SM REMAINS POSSIBLE. MVFR CIGS WITH VARIABLE BASES WILL
CONTINUE INTO EARLY EVENING WITH A SLIGHT INCREASE IN LOWEST BASES
FROM 1500 FT TO AROUND 2500 FT LATE THIS AFTERNOON.
KRWF...VFR LOOKS TO PREVAIL WITH MVFR CIGS HELD OFF TO THE NORTH
AND EAST. SOME LIGHT SNOW REMAINS POSSIBLE BUT VISIBILITY IS
EXPECTED TO REMAIN ABOVE 6 SM IF THIS OCCURS.
KMSP...VARIABLE CLOUD BASES WILL CONTINUE THROUGH THE AFTERNOON
WITH CIGS PRIMARILY ABOVE 1700 FT WITH PERIODIC DIPS TO AROUND
1500 FT AS MORE INTENSE SNOW SHOWERS PASS. VISIBILITY WILL BE
HIGHLY VARIABLE AS WELL WITH VALUES PRIMARILY AROUND 6SM WITH
DROPS TO 3 OR 4SM WITH SNOW SHOWERS WITH A BRIEF 2SM POSSIBLE.
CEILINGS ARE EXPECTED TO IMPROVE TO ABOVE 3000-4000 FT EARLY THIS
EVENING AS THE SNOW TAPERS OFF.
KEAU...VARIABLE MVFR CIGS BETWEEN 1500 AND 3000 FT WILL CONTINUE
AS SNOW SHOWERS INCREASE IN COVERAGE AND INTENSITY EARLY THIS
AFTERNOON. VISIBILITY WILL BE VARIABLE AND LIKELY DROP TO AROUND
2SM FOR SHORT TIMES THIS AFTERNOON. VFR CONDITIONS WILL TAKE A
LITTLE LONGER TO EXIT BUT EXPECT THAT VFR CONDITIONS WILL RETURN
LATE THIS EVENING.
KRNH...1500 TO 2500 FT CEILINGS WILL CONTINUE AS WILL SNOW
SHOWERS. VISIBILITY IS EXPECTED TO FALL TO 3 OR 4SM IN THE MORE
INTENSE SNOW SHOWERS WITH DECREASES TO AROUND 2SM POSSIBLE AT TIMES.
1500 FT BASES WILL BE LESS LIKELY BY LATE AFTERNOON WITH PRIMARILY
2500 FT BASES EXPECTED AT THAT TIME. VFR IS FORECAST TO RETURN
THIS EVENING AND CONTINUE THROUGH THE PERIOD. ..MDB..
&&
.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
&&
$$
RAH/MDB
