Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 151932
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
232 PM CDT TUE APR 15 2014

.UPDATE...FOR SHORT TERM AND 18Z AVIATION DISCUSSION

&&

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY NIGHT)
ISSUED AT 232 PM CDT TUE APR 15 2014

FOCUS IS ON THE SHORTWAVE TROUGH TRACKING FROM THE PACIFIC
NORTHWEST ACROSS THE NORTHERN ROCKIES ON AFTERNOON WATER VAPOR
IMAGERY. A HEALTHY LOW LEVEL JET WILL KICK IN OVERNIGHT AHEAD OF SAID
FEATURE...WITH WARM AIR ADVECTION PROCESSES ENSUING LOCALLY AFTER
06Z WEDNESDAY. EXPECT A BAND OF SNOW TO EXPAND WEST TO EAST ACROSS
CENTRAL MN INTO WEST CENTRAL WISCONSIN BETWEEN 06Z AND 12Z.
SOUTHERN SITES /SOUTH OF INTERSTATE 94/ COULD ESCAPE THIS PRIMARY
BAND OVERNIGHT...BUT A MORE WIDESPREAD/FORMIDABLE AREA OF PRECIP
WILL OVERSPREAD THE AREA DURING THE LATE MORNING AND AFTERNOON
HOURS ON WEDNESDAY. PRECIP TYPE IS CERTAINLY CHALLENGING WITH THIS
EVENT...BUT CONFIDENCE IS FAIRLY HIGH THAT THE PRIMARY FORM OF
PRECIP IN NORTHERN AREAS /LONG PRAIRIE TO CAMBRIDGE MN AND ALONG
AND NORTH OF HWY 8 IN WI/ WILL BE SNOW. ALL OF THE MODELS INDICATE
AT LEAST 6-10 INCHES WILL FALL IN THE WARNING AREA BETWEEN EARLY
WEDNESDAY MORNING AND THURSDAY MORNING...WITH 15.12Z RUNS OF THE
NAM...GFS...AND GEM MODELS EVEN INDICATING A BAND OF 12-18 INCHES
ACROSS POLK/BARRON/RUSK COUNTIES. WHILE THE FORCING IS CERTAINLY
THERE...COULD LOSE A FAIR AMOUNT OF THAT PRECIP AS RAIN IF THE
MODELS ARE OFF ON THEIR TIMING OF THE CHANGEOVER. HAVE THEREFORE
LEANED A BIT MORE CONSERVATIVELY TOWARD THE 15.12Z ECMWF...WHICH
FEATURES 5-10 INCHES ACROSS THE WARNING AREA...AND A ECMWF/NAM
BLEND FOR THE TWIN CITIES TO EAU CLAIRE...WHICH YIELDS 1-3 INCHES.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 357 AM CDT TUE APR 15 2014

PICKING UP WEDNESDAY MORNING AS A LEADING BAND OF WARM ADVECTION SNOW
WILL BE SETUP ACROSS NORTH CENTRAL MINNESOTA...AND WILL BE MAINLY
AFFECTING THE NORTHERN TIER OF COUNTIES IN THE MPX FA. ADDITIONAL
PRECIPITATION WILL DEVELOP TO THE SOUTHWEST OF THIS BAND AND
EVENTUALLY MERGE WITH THE INITIAL BAND AS THE SURFACE LOW ENTERS
SOUTHERN MINNESOTA DURING THE DAY. THE MAIN CONCERNS WITH THIS
FORECAST PACKAGE ARE THE TIMING DIFFERENCES BETWEEN THE FAST
GFS AND SLOW ECMWF. THE NAM SPLITS THESE SOLUTIONS IN TERMS OF
TIMING...SO STILL DETAILS TO BE SORTED OUT IN THAT REGARD. DESPITE
THESE TIMING DIFFERENCES...THERE IS DECENT AGREEMENT IN
PRECIPITATION AMOUNTS...AND THE NORTHERN THIRD OF THE CWA IS STILL
EXPECTED TO RECEIVE THE HEAVIEST PRECIPITATION. WENT AHEAD AND
UPPED POPS TO CATEGORICAL ACROSS THE ABOUT THE NORTHERN HALF OF
THE CWA DURING THE DAY. THE HEAVIES SNOW WILL FALL DURING THE DAY
AS THE FORCING COMES TOGETHER. A WELL DEFINED PV ANOMALY WILL PUSH
EAST ACROSS SOUTHERN MINNESOTA...WHILE STRONG 700H OMEGA IS
MAXIMIZED ON ITS NORTHERN PERIPHERY (BETWEEN ST. CLOUD AND
BRAINERD) OFF THE NAM WHICH LINES UP WELL WITH THE GREATEST FN
VECTOR CONVERGENCE...AND ON THE SOUTHERN EDGE OF THE STRONGEST
FRONTOGENESIS. DIFFERENTIAL DIVERGENCE FROM JET LEVEL DOWN TO THE
LOW LEVELS INDICATES THIS AREA ALONG THE SOUTHERN PERIPHERY OF THE
STRONGEST LIFT AS WELL. CROSS SECTIONS OFF THE NAM INDICATE
NEGATIVE EPV ALOFT AND THE AGEOSTROPHIC CIRCULATION EXEMPLIFIED
THE DEEP LIFT ACROSS THIS SAME AREA. PRECIPITATION TYPE WILL
OBVIOUSLY PLAY A LARGE ROLE ON SNOW ACCUMULATIONS AND IMPACT.
LITTLE CHANGE WAS NEEDED TO THE PRECIPITATION TYPE FORECAST AS THE
TIMING DIFFERENCES AMONGST THE MODELS STILL LENDS UNCERTAINTY TO
THE RAIN/SNOW LINE. BUT OVERALL...NORTH OF ST. CLOUD STILL LOOKS
TO BE PRIMARILY SNOW...WITH THE POSSIBILITY OF A LITTLE RAIN
MIXING IN WEDNESDAY AFTERNOON...WHILE THE TWIN CITIES METRO WILL
SEE PRIMARILY RAIN DURING THE DAY BEFORE SWITCHING OVER TO SOME
LIGHT SNOW AT THE TAIL END OF THE EVENT. THE PRECIPITATION WILL
COME TO AN END WEDNESDAY NIGHT THROUGH THURSDAY MORNING FROM WEST
TO EAST. CONFIDENCE TO ISSUE A WINTER STORM WARNING WAS NOT
ACHIEVED WITH THE LATEST MODEL RUNS...SO DECIDED TO CONTINUE THE
WINTER STORM WATCH FOR THE SAME COUNTIES FOR NOW.

CANADIAN HIGH PRESSURE WILL BE ON THE HEELS OF THE STORM...AND
WILL KEEP TEMPERATURES COLDER THAN NORMAL TO FINISH OUT THE WORK
WEEK. BOTH THE GFS AND EC ADVERTISE A WAVE BRINGING RAIN TO THE
REGION SATURDAY NIGHT...BUT THERE WILL BE A GOOD DEAL OF DRY AIR
TO COMBAT...SO DECIDED CHANCE POPS WERE IDEAL FOR NOW. WE`RE STILL
EXPECTING A WARMING TREND THROUGH THE WEEKEND WITH A RETURN TO
MORE SPRING LIKE TEMPERATURES...ESPECIALLY BY MONDAY.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 232 PM CDT TUE APR 15 2014

VFR CONDITIONS ARE EXPECTED THIS EVENING UNTIL SNOW MOVES INTO
WEST CENTRAL MN LATE TONIGHT. THE FIRST BAND WILL AFFECT KAXN AND
KSTC BETWEEN 09Z AND 12Z WEDNESDAY. THE OTHER SITES WILL LIKELY
MISS OUT ON THE FIRST WAVE OF PRECIP OVERNIGHT...BUT THEN
WIDESPREAD PRECIP WILL EXPAND ACROSS THE AREA THROUGHIGH
CONFIDENCE IN MVFR/IFR CONDITION LATE IN THE DAY TOMORROW. PRECIP
TYPE DURING THE DAY WILL LIKELY BE RAIN OR RAIN/SNOW AT ALL SITES
EXCEPT KAXN AND POSSIBLY KSTC/KRNH...BUT THEN SITES WILL GRADUALLY
CHANCE BACK OVER TO SNOW ON WEDNESDAY EVE.

WINDS WILL BE SCREAMING BETWEEN 1000-3000FT BETWEEN 06Z AND 15Z
WEDNESDAY. THE THREAT FOR LOW LEVEL WIND SHEAR WILL BE THE HIGHEST
FROM SOUTH CENTRAL MN INTO WEST CENTRAL WI /KEAU/ WHERE 0-1KM
SHEAR MAGNITUDE IS PROGGED TO BE AROUND 50 KTS/KM.

KMSP...
THERE IS A SLIGHT CHNACE OF VERY LIGHT SNOW OR RAIN/SNOW AFTER 09Z
WEDNESDAY...BUT THE MEASURABLE PRECIP WILL HOLD OFF UNTIL AFTER
17Z WED. SHOULD BE IN THE FORM OF RAIN THROUGH THE
AFTERNOON...WITH A CHANGEOVER TO WET SNOW WEDNESDAY EVE. A
40-50KT LOW LEVEL JET WILL DEVELOP OVERNIGHT...ALTHOUGH HAVE NOT
INCLUDED A MENTION OF LLWS IN THE TAF AS IT LOOKS TO BE MORE OF A
SPEED VS. DIRECTIONAL SHEAR.

/OUTLOOK FOR KMSP/

WED NGT...MVFR/IFR. RAIN CHANGING TO SNOW EARLY. WINDS NNE 10-15 KTS.
THU...VFR. WINDS NNE 10-15 KTS.
FRI...MAINLY VFR. SLGT CHC MVFR CIGS WITH -RA/-SN.
FRI NIGHT. WINDS NE 10 KTS.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...WINTER STORM WARNING FROM 4 AM WEDNESDAY TO 4 AM CDT THURSDAY
     FOR MNZ042>045-050-052-053.

WI...WINTER STORM WARNING FROM 4 AM WEDNESDAY TO 4 AM CDT THURSDAY
     FOR WIZ014.

     WINTER STORM WARNING FROM 7 AM WEDNESDAY TO 7 AM CDT THURSDAY
     FOR WIZ015-016.

&&

$$


SHORT TERM...LS
LONG TERM...SPD
AVIATION...LS






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