Area Forecast Discussion
Issued by NWS Twin Cities, MN

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000
FXUS63 KMPX 231813
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1213 PM CST TUE DEC 23 2014

.UPDATE...
ISSUED AT 1159 AM CST TUE DEC 23 2014

UPDATED TO INCLUDE 18Z AVIATION DISCUSSION BELOW.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 321 AM CST TUE DEC 23 2014

THERE WILL BE ONE LAST ROUND OF PRECIPITATION WITH THIS SYSTEM
BEFORE IT FINALLY EXITS THE AREA WEDNESDAY. TEMPERATURES ACROSS
THE ENTIRE UPPER MIDWEST ARE HOLDING STEADY IN THE LOW OR MID
30S WITH REALLY NO COLD AIR ANYWHERE TO BE FOUND. THIS TREND WILL
CONTINUE TODAY MAKING FOR ANOTHER TRICKY SITUATION IN TERMS OF
PRECIPITATION TYPE. THE ONE THING TODAY HAS THAT PRIOR DAYS DID
NOT IS MORE INTENSE PRECIPITATION ASSOCIATED WITH DEFORMATION
BANDING ON THE BACKSIDE OF THE LOW. THIS SHOULD...ONE WOULD
THINK...ALLOW FOR MORE SNOW POTENTIAL DESPITE NEAR OR ABOVE
FREEZING TEMPS. HOW MUCH OF AN IMPACT IT WILL HAVE ON THE ROADS IS
THE BIGGEST QUESTION...BUT IF RATES INCREASE AS EXPECTED THEN
THERE COULD BE AT LEAST SOME IMPACT THIS MORNING FROM ALBERT LEA
TO EAU CLAIRE AND LADYSMITH. THAT IS WHERE THE HIGHEST POTENTIAL
FOR ACCUMULATING SNOW WILL RESIDE THIS MORNING AND EARLY
AFTERNOON. INTENSITY AND THEREFORE AMOUNTS WILL TAPER OFF TO THE
WEST OF HERE...WITH AREAS WEST OF NEW ULM AND THE TWIN CITIES
PROBABLY NOT SEEING MUCH...IF ANY ACCUMULATING SNOW.

SNOW RATIOS USING THE AIR FORCE METHOD LEAVE A LOT TO BE DESIRED
WITH ITS 4 OR 5:1 VALUES. THE ROEBBER SNOW RATIO TECHNIQUE FROM
UW- MILWAUKEE ALSO LEANS TOWARD HEAVY SNOW RATIOS OF LESS THAN
9:1...ALTHOUGH THERE ARE SOME PROBABILITIES LEANING INTO THE
AVERAGE RANGE OF 9:1 TO 15:1 AS WELL. TOOK A COMPROMISE OF ALL OF
THIS WITH AN 8:1 RATIO OFFICIALLY. THIS LEAVES A SWATH OF 2 TO 3
INCHES OF WET SNOW FROM KAEL TO KEAU. THE SNOW WILL TAPER OFF BY
MID AFTERNOON WITH ONLY DRIZZLE OR FLURRIES CONTINUING INTO
TONIGHT AS THE MID LEVELS DRY OUT. ADDED EAU CLAIRE COUNTY TO THE
ADVISORY...AND TRIMMED THE BACK END OF THE TIME TO 21Z INSTEAD OF
00Z.

DRIER AIR WILL WORK IN TONIGHT AND PUT AN END TO THE PRECIP FROM
NORTHWEST TO SOUTHEAST. CLOUDS AND FAIRLY UNIFORM TEMPS AROUND
WILL KEEP TEMPS FROM FALLING TOO MUCH...AND WILL PROBABLY REMAIN
IN THE LOW 30S.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 321 AM CST TUE DEC 23 2014

LONG TERMS CONCERNS REMAIN THE DEVELOPMENT OF THE THURSDAY
NIGHT/FRIDAY SYSTEM AND THEN OVERALL PATTERN TOWARD COLDER
WEATHER LATE IN THE WEEKEND AND CONTINUING EARLY NEXT WEEK.

INITIALLY...IN THE WAKE OF TUESDAY SYSTEM...CLOUDS REMAIN ONCE
AGAIN. TEMPERATURES WILL REMAIN ON THE MILD SIDE AS WELL.

THE NEXT WAVE WORKS EAST LATER THURSDAY. THE UPPER FLOW DOES
APPEAR TO BE PARTIALLY SPLIT...BUT THE SOUTHERN STREAM ENERGY
LIFTS AHEAD OF THE CANADIAN TROUGH AND THEY THEN PHASE AS THE
SYSTEM LIFTS THROUGH THE AREA FRIDAY. THERE SHOULD BE A FAIRLY
DISTINCT BAROCLINIC ZONE ASSOCIATED WITH THE TROUGH...AND
ISENTROPIC FORECASTS INDICATE A NICE PRECIPITATION BAND IS
FORECAST ACROSS THE CENTRAL CWA. THIS SHOULD BE IN THE FORM OF
SNOW AS TEMPERATURES COOL DYNAMICALLY AS THE TROUGH LIFTS THROUGH
THE AREA. STILL SOME QUESTION HOW FAR SOUTH THIS WILL DEVELOP SO
WE CONTINUE THE THE HIGH CHANCE POPS OVER THE CENTRAL CWA FOR NOW.
THIS DOES HAVE THE POTENTIAL FOR A HEADLINE TYPE EVENT.

THE GFS DRAGS COOLER AIR OR BELOW NORMAL TEMPERATURES OVER THE
AREA FOR THE WEEKEND. BOTH THE GFS AND ECMWF MOVE A 1030+MB HIGH
OVER THE NORTHERN PLAINS DURING THE PERIOD. THE NEXT THREAT OF
SNOW MOVES INTO THE AREA SUNDAY NIGHT AND MONDAY AS THE LONG TERM
MODELS DRAG A FORMIDABLE ARCTIC FRONT THROUGH THE AREA. THE LONG
TERM CFS ENSEMBLE PLUMES CONTINUE THIS TREND...BUT ONLY FOR A
SHORT TIME...WITH A WARMING TREND DEVELOPING FOR LATER NEXT WEEK.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1159 AM CST TUE DEC 23 2014

PERSISTENT DEGRADED CONDITIONS TO LAST THROUGH MUCH OF TOMORROW AS
A LARGE LOW PRESSURE SYSTEM LUMBERS EASTWARD THROUGH THE REGION.
CEILINGS ARE STRADDLING THE MVFR/IFR THRESHOLD AT INITIALIZATION
TIME...AND ARE EXPECTED TO DROP INTO IFR RANGE FOR ALL SITES THIS
EVENING THRU TMRW MRNG. THE TRICKY PART WILL BE DETERMINING
VISIBILITY DUE TO THE PATCHY/BANDED NATURE OF ONGOING
PRECIPITATION. THE PRECIP AS A WHOLE WILL STEADILY WEAKEN...BUT
THERE IS A CHANCE THAT SOME MOD/HVY PATCHES OF THE PRECIP MAY HIT
ONE OF THE MPX TERMINALS...SPECIFICALLY RNH-MSP. NOT LOOKING FOR
ANYTHING LONG-DURATION...BUT ENOUGH TO DROP VSBY INTO IFR RANGE.
OTHERWISE...PREVAILING VSBY AT ALL SITES WILL BE MVFR AS THE
PRECIP WILL BE VERY LIGHT /-SHSN/. WINDS WILL SLOWLY BACK FROM NNE
TO NW OVERNIGHT THRU TMRW MRNG.

KMSP...MSP STARTS OUT WITH MVFR CEILINGS BUT MAY DROP EASILY INTO
UPPER-END IFR AT ANY POINT THIS AFTN INTO THIS EVE SO THAT WILL
NEED TO BE MONITORED. ASIDE FROM THE POTENTIAL FOR A MOD-HVY BAND
OF -SN IN THE FIRST COUPLE HRS OF THE 18Z TAF...PRECIP INTENSITY
WILL BY AND LARGE BE LIGHT...BUT SO LIGHT THAT IT MAY RESULT IN
MIST THAT WOULD REDUCE VSBY. ATTM...AM THINKING ONLY MVFR VSBY
CATEGORY IN THAT CASE. CONDS TO REMAIN DEGRADED THRU THE DAY
TMRW...INCLUDING A STRONG LIKELIHOOD OF IFR CEILINGS OVERNIGHT
INTO TMRW AFTN.

/OUTLOOK FOR KMSP/
WED...MVFR. WINDS NW 10-15 KTS.
THU...VFR.  WINDS W 5-10 KTS.
FRI...MVFR WITH CHC -SN. WINDS NW 10 KTS.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...WINTER WEATHER ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR WIZ016-
     027-028.

&&

$$

UPDATE...JPC
SHORT TERM...BORGHOFF
LONG TERM...DWE
AVIATION...JPC





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