Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 222153
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
353 PM CST SAT NOV 22 2014

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 238 PM CST SAT NOV 22 2014

MAIN CONCERN DURING THE SHORT TERM PERIOD IS THE TREND OF STRATUS
AND THE POTENTIAL EXTENT OF FOG TONIGHT. A SECONDARY CONCERN IS WITH
PRECIP POTENTIAL TONIGHT INTO SUNDAY...THOUGH MODELS CONTINUE TO
SHOW PRECIP AMOUNTS BEING PRETTY UNDERWHELMING THROUGH SUNDAY ACROSS
THE ENTIRE MPX AREA...WITH DEEPER MOISTURE GOING ACROSS ERN WI AND
MICHIGAN.

EXTENSIVE STRATUS ACROSS ALL BUT THE NW PORTION OF THE MPX CWA HAS
HELD TEMPERATURES IN CHECK ALL DAY. LOOKING TO THE SOUTH...THERE ARE
A COUPLE OF MOISTURE SURGES HEADING OUR WAY. THE FIRST IS QUICKLY
MOVING INTO NRN IA AND WILL LIKELY BE TO THE I-90 CORRIDOR BY 00Z
THIS EVENING. IT IS CHARACTERIZED BY DEWPS IN THE 40S AND MORE
CONCERNING FOR THE CLOUD FORECAST TONIGHT...CLEAR SKIES. THE SECOND
MOISTURE SURGE IS JUST NOW GETTING TO I-80 AND IT IS ASSOCIATED WITH
DEWPS IN THE 50S...AND A RETURN TO LIFR STRATUS AND FOG. THE
ECMWF/GEM SHOW THIS SECOND MOISTURE SURGE AND ITS ASSOCIATED LOWER
50 DEWPS GETTING CLEAR UP TO I-90 SUNDAY MORNING BEFORE GETTING
SHUNTED OFF TO THE EAST. CERTAINLY DEWPS IN THE 40S WITH SNOW ON THE
GROUND FAVORS STRATUS CONTINUING THROUGH THE NIGHT AND THE CURRENT
FORECAST CERTAINLY READS THAT WAY...BUT WE WILL HAVE WATCH HOW THAT
CLEARING EVOLVES.

FOR FOG...ONE THING WE ARE POSITIVE ABOUT IS IT WILL BE HAZY TROUGH
THE NIGHT GIVEN DEWPS ABOVE FREEZING WITH SNOW ON THE GROUND. THERE
WAS TALK OF A DENSE FOG ADVISORY...BUT NOT CONFIDENT ENOUGH ON WHERE
TO PUT ONE OTHER THAN ANYONE UNDER STRATUS NOW...WHICH IS JUST ABOUT
OUR ENTIRE CWA AND DID NOT WANT TO ISSUE SUCH A LARGE ADVY AT THIS
POINT. ON TOP OF THAT...WE WILL BE MAINTAINING 8-12 KT WINDS THROUGH
THE NIGHT...SO THAT WILL SUPPLY A CERTAIN DEGREE OF MIXING AS WELL.
NOT TO MENTION WE HAVE THAT CLEARING RACING NORTH OUT OF IA. AT THIS
POINT...HIGHEST CONFIDENCE IN DENSE FOG IS WHERE OUR DEEPEST SNOW
RESIDES ACROSS THE NRN MPX CWA. THE HRRR WOULD SUPPORT THIS IDEA AS
IT DOES SHOW VSBYS IMPROVING THROUGH THE NIGHT ACROSS SRN MN AS THAT
SLUG OF SLIGHTLY DRIER AIR ACROSS IA WORKS INTO MN.

FOR TEMPERATURES...THEY MAY GO NOTHING BUT UP THROUGH THE NIGHT.
FIRST RUN OF THE HOURLY TEMPERATURE TOOL WITH THE LOCAL SUPERBLEND
BROUGHT A TEMPERATURE OF 53 TO ALBERT LEA BY 7Z TONIGHT. DID NOT GO
QUITE THAT AGGRESSIVE...BUT DO THINK MUCH OF THE AREA EAST OF A NEW
ULM TO MORA LINE WILL RISE INTO THE 40S OVERNIGHT. GIVEN THE MILD
START...ALSO GAVE HIGHS SUNDAY A BIT OF AN UPWARD NUDGE TO ABOUT A
50/50 BLEND BETWEEN THE PREVIOUS FORECAST AND THE 22.12 GEM/ECMWF.
THE GEM/ECMWF SHOW HIGHS IN THE LOW 50S FOR SE MN/WRN WI TOMORROW.
GIVEN THE EXTENSIVE CLOUD COVER...DO NOT THINK WE WILL GET THAT
HIGH...BUT DO HAVE HIGHS INTO THE MID/UPPER 40S FOR ALL BUT WRN AND
CENTRAL MN.

FOR PRECIP...THAT CONTINUES TO LOOK UNDERWHELMING. OUR BIGGEST
PROBLEM THROUGH TONIGHT CONTINUES TO BE THE FACT THAT THE ATMO CAN
NOT TAKE ON MUCH MORE MOISTURE BELOW 900 MB...BUT ABOVE THAT...ITS
BONE DRY. CONTINUED TO RUN WITH HIGHEST POPS SUNDAY OUT IN ERN AREAS
AS THEY WILL BE CLOSER TO THE H85 MOISTURE TRANSPORT...BUT LIKING
THE IDEA THE GFS/SREF/NMM/ARW SHOW OF A NARROW BAND OF RAIN CENTERED
ON FGEN IN THE H7-H6 LAYER COMING OUT OF SODAK TONIGHT AND WORKING
ACROSS SRN MN THROUGH SUNDAY MORNING. THE 22.18 HOPWRF MEMBERS ALSO
SHOW THIS BAND OF PRECIP BY 9Z /THE END OF THOSE RUNS/ MOVING INTO
THE WRN PORTION OF THE FSD FORECAST AREA...SIMILAR TO WHAT THE
MODELS MENTIONED ABOVE SHOW. DID BOOST POPS IN SW MN INTO THE HIGH
CHANCE CATEGORY SUNDAY MORNING FOR NOW. THIS MAY VERY WILL END UP
BEING THE BEST CHANCE AT SEEING MEASURABLE PRECIP WITH THIS SYSTEM
FOR MUCH OF OUR MN FORECAST AREA.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 238 PM CST SAT NOV 22 2014

SUNDAY NIGHT THROUGH MONDAY WILL BRING A PERIOD OF STRONG WINDS
AND LIGHT PRECIPITATION TO THE FORECAST AREA...IN THE WAKE OF A
DEEPENING MID LATITUDE CYCLONE. THE STRONGEST WINDS ARE EXPECTED
ACROSS THE WESTERN FORECAST AREA AND THE HIGHEST POTENTIAL FOR
ACCUMULATING SNOW REMAINS ACROSS FAR EASTERN MN...BUT ESPECIALLY
IN WEST CENTRAL WI.

BY 00Z MONDAY...RAPID CYCLOGENESIS WILL BE ONGOING IN THE MID
MISSISSIPPI RIVER VALLEY IN RESPONSE TO A DEEP TROUGH DIGGING IN
ACROSS THE CENTRAL CONUS AND A LARGE AREA OF 120-150M 500MB 12-HR
HEIGHTS FALLS MOVING ACROSS THE AREA. THE AMOUNT OF DEEPENING IS
STILL QUITE VARIABLE DEPENDING ON WHICH 12Z SOLUTION ONE CHOOSES TO
FOLLOW. THE 22.12Z GFS IS BY FAR AND AWAY THE MOST AGGRESSIVE IN
STRENGTHENING THE LOW OVER THE SOUTHERN HALF OF LAKE MICHIGAN BY
06Z MONDAY TO 975MB...969MB OVER NORTHERN MICHIGAN BY 12Z...AND
966MB AS IT MOVES NORTH OF THE GREAT LAKES BY 18Z. THE NAM AND
ECMWF SEEM MORE REASONABLE WITH A BIT MORE MODEST DEEPENING.
TYPICALLY...THE KIND OF DEEPENING THE GFS IS SHOWING ONLY OCCURS
WITH VERY STRONG BAROCLINICITY AND/OR A NEGATIVELY TILTED UPPER
TROUGH. WE REALLY DON`T HAVE EITHER. THERE IS STRONG COLD
ADVECTION AND A DECENT TEMPERATURE GRADIENT ACROSS THE MID/UPPER
MISSISSIPPI VALLEY...BUT THEY SEEM MORE IN LINE WITH THE NAM/ECMWF
THAT ARE BIT MORE PROGRESSIVE WITH THE LOW AND NOT AS WOUND UP.
THEREFORE...WE DID NOT JUMP ON THE GFS SNOWFALL FORECAST THAT
WOULD GIVE 6-8" TO PORTIONS OF WEST CENTRAL WI. WE THINK THE
HEAVIEST PRECIP SHOULD BE EAST OF THE FORECAST AREA AND THE
DYNAMIC COOLING ON THE BACK SIDE OF THE LOW WILL BE WEAKER THAN
THE GFS INDICATES. IT IS NOTABLE THAT THE 22.15Z SREF AND GEM ALSO
SHOW THE POTENTIAL FOR SEVERAL INCHES OF SNOW NEAR OR JUST EAST OF
THE FORECAST AREA. THIS IS SOMETHING TO FOLLOW OVER THE NEXT 12-18
HOURS...BUT WE SIMPLY DIDN`T HAVE ENOUGH CONFIDENCE TO ISSUE A
WINTER STORM WATCH AT THIS POINT. FURTHERMORE...EVEN WITH THE
EXPECTED STRONG WINDS...THE WARM TODAY HAS LIKELY LIMITED THE
AMOUNT OF SNOW AVAILABLE FOR BLOWING AND DRIFTING. THERE WERE A
LOT OF HIGHS IN THE UPPER 30S AND LOWER 40S IN WESTERN MN TODAY.

THE NEXT SYSTEM TO WATCH ARRIVES ON WEDNESDAY AND THERE IS AGAIN
SIGNIFICANT DIFFERENCES BETWEEN THE GFS AND ECMWF. THE ECMWF HAS A
POTENT CLIPPER SYSTEM WITH 1-4" OF SNOW...IMPRESSIVE COLD
ADVECTION AND A TIGHT PRESSURE GRADIENT ON THE BACK SIDE OF THE
SYSTEM. THE 22.12Z ECMWF HAS SUSTAINED 25-30KTS NEAR THE ND/SD/MN
BORDER EARLY WEDNESDAY MORNING - QUITE IMPRESSIVE GIVEN ITS
COARSER RESOLUTION. THE GFS HAS A WEAK SURFACE TROUGH AND MUCH
LESS LIFT. THIS MID WEEK SYSTEM PRETTY MUCH LOCKS IN OUR CHANCE
FOR A WELL BELOW NORMAL THANKSGIVING. IT LOOKS VERY COLD.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1148 AM CST SAT NOV 22 2014

IFR AND LOWER STRATUS CONTINUES TO SLOWLY CRAWL NW ACROSS
MN...STILL QUESTIONABLE WHETHER OR NOT IT REACHES AXN...BUT WITH
12Z TAF HAVING IT GETTING THERE...KEPT THAT TREND GOING. THESE
CIGS WILL ONLY MARGINALLY IMPROVE THROUGH THE AFTERNOON...LIKELY
JUST GOING FROM LIFR TO IFR BEFORE GOING BACK TO LIFR TONIGHT.
GIVEN CONTINUED SOUTH WINDS AND INCREASING MOISTURE OVER THE SNOW
THROUGH THE NIGHT...KEPT THE TREND FOR FG TONIGHT FROM 12Z TAFS
GOING. UNCERTAINTY STARTS TO INCREASE TOMORROW WITH THE POTENTIAL
FOR CIGS TO QUICKLY GO VFR. FOR NOW...TIMED IMPROVEMENT IN CIGS TO
WHEN WINDS ARE FORECAST TO SWING AROUND TO 240 DEGS OR GREATER.
SREF MVFR CIG PROBABILITY DROPS TO NEAR ZERO SUNDAY MORNING OUT
WEST...SO WE COULD VERY WELL SEE CIGS IMPROVE FASTER THAN
CURRENTLY INDICATED ACROSS MN. FOR PRECIP...LOOKING LIKE OUR BEST
CHANCE THIS TAF PERIOD WILL BE WITH A NARROW BAND OF RAIN THE
NMM/ARW/GFS/SREF SHOW COMING OUT OF SODAK LATE TONIGHT AND WORKING
ACROSS MN DURING THE MORNING.

KMSP...CONFIDENCE IS HIGH IN MINIMAL IMPROVEMENTS TO CIGS/VIS
THROUGH THE DAY. CONTINUED MOIST SRLY FLOW WILL ALSO LEAD TO A
LOWERING IN CONDITIONS TONIGHT...THOUGH THERE IS LESS CONFIDENCE
IN THE TIMING ON WHEN CIGS DROP BACK BELOW 005. 50/50 CONFIDENCE
ON THE FOG TEMPO GROUP...BUT WITH IT ALREADY IN THE TAF...LEFT IT
THERE. CONFIDENCE IS CONSIDERABLY LOWER THIS FAR OUT WITH
IMPROVEMENTS IN THE TAF BY SUNDAY AFTERNOON...BUT FOLLOWED THE
IDEA OF THE NAM/SREF ON THAT FOR NOW.

/OUTLOOK FOR KMSP/
MON...MVFR/IFR CIGS CHC -SN. WINDS NW 20G30 KT.
TUE...VFR. WINDS W 5-10 KT.
WED...MVFR/IFR CHC -SN. WINDS NW 10KTS.

&&

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

$$

SHORT TERM...MPG
LONG TERM...CLF
AVIATION...MPG







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