655 
FXUS63 KMPX 120014
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
614 PM CST WED JAN 11 2012

.UPDATE...

UPDATED TO INCLUDE 00Z AVIATION DISCUSSION BELOW.

&&

.DISCUSSION...
PRIMARY FORECAST CONCERNS ARE IN THE SHORT TERM... TONIGHT THROUGH
THURSDAY EVENING... AS WE CONTEND WITH GUSTY WINDS... MUCH COLDER
TEMPERATURES... AND ACCUMULATING SNOWS OVER THE EASTERN PORTION OF
THE AREA. LATEST WATER VAPOR IMAGERY SHOWS A SHARP UPPER TROUGH
EXTENDING FROM CENTRAL CANADA INTO THE NORTHERN PLAINS. THIS
FEATURE WILL BE MOVING INTO OUR AREA TONIGHT... WITH MUCH COLDER
TEMPERATURES THAN WE/VE SEEN IN QUITE A WHILE. THE VERY STRONG
NORTHWEST WINDS WE/VE SEEN TODAY WILL START TO SETTLE DOWN THIS
EVENING... AS THE UPPER TROUGH BEGINS TO PIVOT AND LEAD TO THE
INTENSIFICATION OF A SURFACE LOW IN THE LOWER GREAT LAKES TONIGHT
THROUGH THURSDAY. AN BAND OF POST-FRONTAL CONTINUES TO MOVE EAST
ACROSS THE CWFA THIS AFTERNOON... AND LOOKS TO HANG UP OVER THE
FAR EASTERN FORECAST AREA THIS EVENING AS THE SURFACE LOW TAKES
SHAPE WELL TO OUR SOUTHEAST. THE SHORT RANGE GUIDANCE IS IN DECENT
AGREEMENT ON THE EVOLUTION OF THINGS OVER THE NEXT TWO DAYS...
ALTHOUGH THERE ARE DEFINITELY SOME DIFFERENCES ON WHERE THE
WESTERN EDGE OF THE BETTER PCPN WILL BE. AM INCLINED TO STICK
CLOSER TO THE NAM... WHICH KEEPS THE BULK OF THE BETTER AMOUNTS OF
OVER 0.25 INCHES EAST OF OUR AREA... ALTHOUGH DID BLEND A BIT WITH
THE GFS AND SREF SOLUTIONS. MAIN REASONS FOR NOT BEING OVERLY
OPTIMISTIC ABOUT SIGNIFICANT PCPN IN OUR CWFA ARE THE QUICK
TRANSITION TO ISENTROPIC DESCENT AND A SHIFT INTO THE UNFAVORABLE
LEFT ENTRANCE REGION OF THE UPPER JET. HOWEVER... EVEN A FEW
TENTHS OF AN INCH OF PCPN COULD LEAD TO SNOWFALL TOTALS OF 2 TO 4
INCHES OVER THE FAR EASTERN CWFA FROM LATE THIS AFTERNOON THROUGH
THURSDAY AFTERNOON.

CYCLONIC FLOW AND LINGERING DEEPER LAYER MOISTURE WILL KEEP THE
POTENTIAL FOR SOME LIGHT SNOW GOING ACROSS THE EASTERN CWFA
THROUGH THURSDAY NIGHT... ALTHOUGH IT LOOKS LIKE ANY ACCUMULATING
SNOW SHOULD END BY THURSDAY EVENING. WE WILL THEN SIT UNDER THE
SURFACE RIDGE FOR ABOUT 18 HOURS BEFORE A QUICK MOVING SHORTWAVE
AND ACCOMPANYING SURFACE LOW EMBEDDED IN THE NORTHWEST FLOW DROP
SOUTHEAST ACROSS THE AREA LATE FRIDAY NIGHT INTO SATURDAY. THIS
LOOKS TO BRING A CHANCE FOR SOME LIGHT SNOW... MAINLY TO THE
EASTERN HALF OF THE FORECAST AREA... ON SATURDAY AS A SLUG OF
ISENTROPIC LIFT AND MID-LEVEL FRONTOGENESIS WORK ACROSS THE AREA.
ANOTHER SURFACE RIDGE WILL MAKE A VERY BRIEF APPEARANCE OVER THE
AREA SATURDAY NIGHT INTO SUNDAY... THEN ROBUST WARM ADVECTION
LOOKS TO WORK INTO THE REGION SUNDAY AND SUNDAY NIGHT... WITH
ABOVE NORMAL TEMPERATURES ONCE AGAIN. HOWEVER... THIS LOOKS TO BE
FAIRLY SHORT-LIVED AS THE GFS AND ECMWF ARE IN GOOD AGREEMENT ON
BRINGING ANOTHER COLD FRONT THROUGH THE AREA ON MONDAY... TAKING
READINGS BACK DOWN CLOSE TO NORMAL AGAIN. THE BEST CHANCES FOR
PCPN WITH THE SYSTEM ON MONDAY ONCE AGAIN LOOK TO BE OVER THE
EASTERN PORTION OF THE AREA... WHERE DEEP SATURATION LOOKS MOST
LIKELY TO OCCUR WHILE THERE IS STILL SOME LARGE SCALE FORCING IN
PLACE. SOME LIGHT ACCUMULATIONS MAY OCCUR ONCE AGAIN DURING THAT
TIME FRAME... MAINLY OVER WEST CENTRAL WISCONSIN. DRY WEATHER AND
COLDER TEMPERATURES WILL THEN HANG ON ACROSS THE AREA THROUGH
TUESDAY... BUT THE BRISK UPPER LEVEL FLOW LOOKS TO MOVE ANOTHER
SHORTWAVE ALONG THE INTERNATIONAL BORDER BY WEDNESDAY... WITH WARM
ADVECTION RAPIDLY DEVELOPING ACROSS OUR AREA IN ADVANCE OF IT.
PCPN WITH THIS NEXT SYSTEM CURRENTLY LOOKS LIKE IT WILL HOLD OFF
UNTIL WEDNESDAY NIGHT... BUT GIVEN THE QUICK UPPER FLOW IT IS
CERTAINLY POSSIBLE IT COULD ARRIVE SOONER WHICH MIGHT LEAD TO THE
INCLUSION OF POPS ON WEDNESDAY. BUT... FOR NOW WILL KEEP THINGS
DRY DURING THE TUESDAY-WEDNESDAY TIME FRAME.

&&



.AVIATION.../00Z TAF ISSUANCE/ 

CDFNT NOW THROUGH ALL TAF SITES...INTO CENTRAL WI AND EASTERN
IA...WITH SOLID NORTHWEST WINDS. ORIGINAL BAND OF SNOW HAS
DISSIPATED WHILE NORTHWEST FLOW WILL BRING IN PERIODIC FLURRIES
AND SNOW SHOWERS WITH THE HEAVIEST OF ANY SNOW AT KRNH-KEAU. MAIN
CONCERN OVERNIGHT THRU MOST OF TMRW ARE CEILINGS. MODEL GUIDANCE
IS ON THE SIDE OF HOLDING CEILINGS IN THE LOW-END MVFR RANGE WHILE
A FEW MODELS /PARTICULARLY SREF/ DO BRING DOWN CIGS INTO IFR
RANGE. LAMP GUIDANCE AND MOS GUIDANCE KEEP CIGS IN MVFR RANGE...
SO THAT COMBINED WITH NO UPSTREAM OBS INDICATING IFR AND WINDS
EXPECTED TO REMAIN QUITE ELEVATED...HAVE OPTED TO HALT CIGS AT NO
LOWER THAN 1000 FT. THAT SAID...IFR CIGS CANNOT BE RULED OUT
DURING THE EARLY MORNING HOURS THRU AROUND NOON TMRW. AS FOR
VSBY...SINCE THE MN TAF SITES WILL BE MOSTLY DEVOID OF SNOW THRU
THE DAY TMRW...VSBYS ARE NOT EXPECTED TO BE ANY LOWER THAN 5SM. AS
FOR THE WI SITES...MVFR VSBYS WILL BE COMMON BUT IFR VSBYS MAY
OCCUR FROM TIME TO TIME...BOTH THIS EVENING AND MIDDAY TMRW WHEN
THE UPPER LEVEL LOW BECOMES MORE ORGANIZED. CONDITIONS THEN
IMPROVE LATE TMRW AFTN INTO TMRW EVE AS THE LARGE STORM SYSTEM
BEGINS TO PULL AWAY.

MSP...MAIN CONCERN IS CEILINGS THRU TMRW AFTN. CIGS ARE ALREADY
WITHIN THE UPPER LIMITS OF MVFR BUT ARE EXPECTED TO GRADUALLY DROP
THROUGH THE OVERNIGHT HOURS TO LOW-END MVFR...OR AT LEAST BELOW
THE 1800 FT THRESHOLD. ARGUMENTS CAN BE MADE FOR AND AGAINST THERE
BEING IFR CIGS AROUND DAYBREAK THROUGH MID-TMRW AFTN...BUT WITH
MOST MODEL GUIDANCE UNSUPPORTIVE OF IFR CIGS PLUS LACK OF UPSTREAM
OBSERVATIONS SUGGESTING AS SUCH...HAVE ONLY BROUGHT CIGS DOWN TO
LOW-END MVFR BUT WITH THE CAVEAT THAT IFR CIGS CANNOT BE RULED OUT
DURING THAT TIME. A FEW ADDITIONAL SNOW BANDS ARE POSSIBLE WHICH
COULD DEGRADE VSBYS INTO MVFR RANGE BUT CHCS ARE TOO LOW FOR THEIR
INCLUSION. CIGS THEN SLOWLY IMPROVE TMRW AFTN INTO TMRW EVENING.
WINDS WILL REMAIN SOLIDLY NW IN GENERALLY THE 15G25KT AREA. 

OUTLOOK...
THU NIGHT THROUGH FRI NIGHT...VFR UNDER HIGH PRESSURE.
SAT...POSSIBLE MVFR CONDITIONS AND -SN AS A FRONTAL SYSTEM MOVES
THROUGH. 
SAT NIGHT THROUGH MON...VFR AHEAD OF NEXT SYSTEM. 
MON NIGHT INTO TUE...POSSIBLE MVFR CONDITIONS AND -SN AS ANOTHER
FRONTAL SYSTEM MOVES THROUGH.

&&

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

&&

$$

JPC