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000
FXUS63 KMKX 112122
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
322 PM CST WED DEC 11 2013

.TONIGHT AND THURSDAY...FORECAST CONFIDENCE MEDIUM.

ANOTHER CLIPPER WILL SWING ACROSS MN AND CENTRAL WI TONIGHT. WEAK
SHORTWAVE ENERGY ALONG AN 850MB BAROCLINIC ZONE WILL ALLOW FOR A
BAND OF WARM AIR ADVECTION... FRONTOGENESIS AND WEAK RISING MOTION.
HIGHER CONFIDENCE IN LIGHT SNOW SPREADING ACROSS CENTRAL AND
PORTIONS OF SOUTHERN WI AROUND MIDNIGHT AND EXITING AROUND 7 AM.
INCREASED POPS TO LIKELY IN THE NORTHERN MKX COUNTIES. LIGHT SNOW
SHOULD MAKE IT AS FAR SOUTH AS MADISON AND MILWAUKEE...BUT ONLY
EXPECT TRACE TO 0.1 SNOW ACCUMULATION. THE 18Z NAM IS TRENDING
SLOWER WITH THIS CLIPPER AND THE 12Z REGIONAL CANADIAN IS THE
FURTHEST SOUTH AND HAS HIGHEST QPF. SNOW WILL BE FLUFFY WITH 19-20:1
SNOW RATIOS.

THE OTHER CONCERN FOR TONIGHT IS THE COLD TEMPERATURES WHICH LEAD TO
THE WIND CHILL ADVISORY.

THERE IS A VERY COLD AND DRY AIR MASS OVER MN AND IOWA TODAY WHICH
WILL TRANSLATE SOUTHEAST THIS EVENING. 925MB TEMPS WILL BE -20C AT
00Z THIS EVENING. WITH THE HIGH PRESSURE RIDGE WEDGING INTO SOUTHERN
WI...WINDS WILL DIMINISH TO LESS THAN 10 KNOTS THIS EVENING.
EXPECTING AT LEAST MINOR DECOUPLING INLAND FROM THE LAKE AND
TEMPERATURES SHOULD DROP QUICKLY INTO THE UPPER SINGLE DIGITS BELOW
ZERO. WITH A TEMP OF -7F AND WINDS OF 5 KNOTS OR GREATER...THE WIND
CHILLS WOULD REACH -20F OR LOWER...WHICH MEETS CRITERIA FOR A WIND
CHILL ADVISORY. UPPER LEVEL TEMPERATURES BEGIN INCREASING AFTER
MIDNIGHT...ALONG WITH CLOUDS AND SNOW SPREADING ACROSS AT LEAST THE
NORTHERN MKX FORECAST AREA. THIS WILL HELP TO STOP TEMPS FROM
DROPPING ANY MORE...AND TO WARM SURFACE TEMPS UP TO AROUND ZERO BY 7
AM.

OPTED TO LEAN TOWARD COLDER GUIDANCE FOR MIN TEMPS TONIGHT...DESPITE
MANY OF THE 12Z MODELS SUGGESTING OTHERWISE. THERE IS A LOT OF
UNCERTAINTY IN THE TEMPERATURE FORECAST.

.THURSDAY...FORECAST CONFIDENCE HIGH.

MID LEVEL CLOUDS ARE EXPECTED TO HANG AROUND THROUGH MOST OF THE DAY
THURSDAY AS VERY WEAK RIPPLES IN THE 500MB FLOW ALONG WITH HIGH RH
IN THE UPPER LEVELS CONTINUE TO ROLL ACROSS CENTRAL WI IN THE
VICINITY OF THE 850MB BAROCLINIC ZONE. 925MB TEMPS WILL MODERATE TO
AROUND -7C BY 00Z FRI WITH SOUTHWEST SURFACE WINDS. EXPECT MAX TEMPS
TO INCREASE INTO THE MID TO UPPER TEENS BY THE AFTERNOON.

.FRIDAY AND SATURDAY - CONFIDENCE...MEDIUM
LONG DURATION LIGHT SNOW EVENT EXPECTED. PRIMARY SURFACE AND 850
LOWS SHOWING BETTER ORGANIZATION FROM THE CENTRAL PLAINS INTO THE
OHIO VALLEY. THIS KEEPS THE MORE FAVORED SWATH OF DECENT SNOW
ACCUMULATIONS TO OUR SOUTH AND EAST. FRONTOGENETICAL BAND PROGGD
TO DEVELOP ACROSS SRN WI FOR FRIDAY WITH SYSTEM SNOWS ASSOCIATED
WITH INVERTED TROUGH/NRN PERIPHERY OF LOW ARRIVING FRIDAY NIGHT
AND LASTING INTO SATURDAY. USING A BLENDED APPROACH WITH THE QPF
NUMBERS AND FAIRLY HIGH SNOW RATIOS CAME UP WITH A GENERAL 1-2
INCH EVENT. HOWEVER FAVORED THE SOMEWHAT HIGHER GFS QPF NUMBERS IN
THE EAST DUE TO THE PERSISTENT FLOW OFF THE LAKE WITH DELTA T
NUMBERS AROUND 17C. SO FOR NOW JUST A SUBTLE UPTICK IN THE QPF
RATHER THAN GOING TOO HIGH. POTENTIAL FOR SOME HIGHER TOTALS
EVOLVING DEPENDING ON FRIDAY NIGHT INTO SATURDAY IF LOWER LEVEL
FLOW TURNS MORE NE AND SETS UP A PRIMARY BAND.

.SUNDAY AND MONDAY - CONFIDENCE...LOW TO MEDIUM
UNSETTLED NORTHWEST FLOW REGIME EXPECTED TO CONTINUE. PARADE OF
PERIODIC SHORTWAVES WILL KEEP LIGHT SNOW CHANCES IN THE FORECAST.
MODEL DIFFERENCES ON TIMING OF THE FEATURES THOUGH SOME CONSENSUS
FOR LIGHT SNOW FOCUSES IN THE SUNDAY NIGHT PERIOD AND THEN AGAIN
MONDAY AND MONDAY NIGHT THOUGH MODELS NOT IN SYNC WITH TIMING.

.TUESDAY AND WEDNESDAY - CONFIDENCE...LOW
WHILE SOME CONFIDENCE THAT A DRY PERIOD WILL PAN OUT THERE IS A
LARGE MODEL DISCREPANCY BETWEEN THE GFS AND ECMWF WITH RESPECT TO
TEMP FIELDS. 500 MILLIBAR PATTERN EVOLVES TO LARGELY ZONAL THOUGH
GFS MAINTAINS A COLD FLOW IN THE LOW LEVELS RESULTING IN A 15-20
DEGREE CELSIUS DIFFERENCE WITH THE ECMWF AT 850 MILLIBARS. 925
TEMPS OFF THE GFS ARE IN THE NEGATIVE TEENS CELSIUS AND THE THE
ECMWF SHOWING ANYWHERE FROM 4-6 CELSIUS ON THE PLUS SIDE. HOWEVER
12Z ECMWF HAS TRENDED COLDER THAN THE 00Z RUN. GIVEN THE DISPARITY
WILL USE THE ALLBLEND TEMP GUIDANCE...HOWEVER APPEARS THE ECMWF IS
TRENDING TOWARDS THE GFS AT THIS POINT.

&&

.AVIATION/00Z TAFS/...VFR CONDITIONS EXPECTED THROUGH THE EVENING.
TEMPS WILL BE VERY COLD TONIGHT...DROPPING INTO THE SINGLE DIGITS
BELOW ZERO.

A CLIPPER SYSTEM WILL LIKELY SPREAD LIGHT SNOW ACROSS CENTRAL WI
FROM MIDNIGHT TONIGHT TO 7 AM THURSDAY. CIGS/VSBYS COULD DROP TO
MVFR WITH THE SNOW...ESPECIALLY NORTH OF MSN AND MKE. LESS THAN A
HALF INCH ACCUMULATION EXPECTED NORTH OF MSN AND MKE...AND A TRACE
TO 0.1 INCH ALONG THAT LINE.

&&

.MARINE...NORTHWEST WINDS AND GUSTS STRUGGLED TO 25 KNOTS DURING THE
DAY. WINDS WILL CONTINUE TO DIMINISH THIS EVENING. THUS...CANCELLED
THE SMALL CRAFT ADVISORY WITH THE 330 PM NSH ISSUANCE.

THE NEXT CHANCE FOR HIGH WINDS AND WAVES WILL BE FRIDAY NIGHT AS
NORTHEAST WINDS PERSIST FOR A LONG PERIOD OF TIME AND BUILD HIGH
WAVES THROUGH SATURDAY.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...WIND CHILL ADVISORY FROM 6 PM THIS EVENING TO 6 AM CST THURSDAY
     FOR WIZ046-047-051-052-056>060-062>072.

LM...NONE.
&&

$$
TONIGHT/THURSDAY AND AVIATION/MARINE...MRC
THURSDAY NIGHT THROUGH WEDNESDAY...COLLAR