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