Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 222039
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
340 PM CDT SUN MAR 22 2015

.TONIGHT AND MONDAY...FORECAST CONFIDENCE - MEDIUM.

A BAND OF MODERATE SNOW SPREAD INTO SOUTHWEST WISCONSIN THIS
AFTERNOON AND NOW EXTENDS ALL THE WAY BACK INTO SOUTHERN MN. THIS
BAND IS ASSOCIATED WITH VORTICITY ADVECTION AND STRONG MID LEVEL
FRONTOGENESIS AND STRONG UPWARD MOTION. VISIBILITIES ARE DOWN TO A
HALF TO ONE MILE OR EVEN LESS WITHIN THIS BAND. EXPECT AROUND AN
INCH ACCUMULATION THROUGH EARLY EVENING WITH THIS INITIAL FEATURE...
DESPITE THE RELATIVELY WARM GROUND.

THE MODELS WERE INDICATING SORT OF A LULL BETWEEN THIS INITIAL FGEN
BAND AND ANOTHER ROUND OF MORE STEADY SNOW MAINLY BETWEEN MIDNIGHT
AND 8 AM. LOOKING AT REGIONAL RADAR... THERE MAY NO LONGER BE A LULL
THIS EVENING. STILL SOME UNCERTAINTY.

THEN A POTENT 500MB SHORTWAVE WILL TRACK ACROSS THE UPPER MIDWEST
TONIGHT INTO MONDAY MORNING. MORE WIDESPREAD SNOW WILL SPREAD INTO
SOUTHWEST WI ALONG WITH THE STRONG 850-700MB BAROCLINIC ZONE...
ARRIVING IN MKX AREA AROUND MIDNIGHT. ENHANCED FRONTOGENESIS AND
ISENTROPIC UPGLIDE WILL SUPPORT ADDITIONAL SNOWFALL ACCUMULATIONS OF
3 TO 4 INCHES ROUGHLY FROM A BARABOO TO VERONA TO JANESVILLE LINE
AND SOUTHWEST. THE WINTER WEATHER ADVISORY IS IN EFFECT FROM NOW
THROUGH 8 AM MONDAY.

MILWAUKEE COULD SEE ABOUT AN INCH TONIGHT WITH LOWER AMOUNTS NORTH
OF THERE DUE TO A CONTINUOUS FEED OF VERY DRY AIR IN THE LOW LEVELS.
I USED A BLEND OF THE 12Z GFS...CANADIAN AND ECMWF MODELS FOR QPF
AMOUNTS WITH THIS SYSTEM. THE NAM APPEARS VERY OVERDONE ON QPF...
BUT HAS THE SAME GENERAL PLACEMENT OF THE HIGHEST AMOUNTS.

THERE IS STILL SOME UNCERTAINTY ABOUT HOW LONG THE PRECIP WILL TAKE
TO END FROM NORTH TO SOUTH MONDAY MORNING... BUT MODELS ALL SHOW IT
ENDING BY 1 PM/18Z. IT IS LOOKING LESS LIKELY FOR A PERIOD OF
FREEZING DRIZZLE MONDAY MORNING AS THE PRECIPITATION COMES TO AN END
BASED ON FORECAST SOUNDINGS REMAINING SLIGHTLY COLDER.

.MONDAY NIGHT THROUGH WEDNESDAY...CONFIDENCE - HIGH.

QUIET MONDAY NIGHT INTO TUESDAY MORNING AS SHORT WAVE RIDGING PASSES
ACROSS THE UPPER MIDWEST.  SPREAD CHANCE POPS FARTHER EAST TUESDAY
AFTN AS RIDGING PUSHES OFF TO THE EAST AND STRONG SURGE OF MOISTURE
ADVECTION AND CONVERGENCE PROGRESSES RAPIDLY NWD AHEAD OF
APPROACHING. STILL SOME UNCERTAINTY REGARDING LOW TRACK BUT APPEARS
ITS TAKING AIM ON SRN WI TUE NIGHT.  STRONG MOISTURE SURGE AND MID-
LEVEL SHORT WAVE STILL EXPECTED TO BRING A PERIOD OF RAIN TO ALL OF
SRN WI...WITH BENEFICIAL QPF OF 0.2 TO 0.5 INCH.  SOME CONCERN OF
THIS RAPID RAINFALL FALLING ON FRESH SNOWCOVER OVER SWRN CWA LIKELY
TO RESULT IN AT LEAST PONDING OF WATER AND MINOR STREET FLOODING.

ALSO STARTING TO SEE SOME ELEVATED INSTABILITY ON FORECAST SOUNDINGS
FOR SRN WI.  WITH EXPECTED DYNAMICS FROM THIS SYSTEM...WL ADD A
CHANCE FOR T TO SRN CWA.  STRONG LIFT SHIFTS RAPIDLY OFF TO THE
NORTHEAST LATE TUESDAY NIGHT AND WED MRNG AS DRIER AIR WRAPS IN FROM
THE WEST.  MUCH OF WEDNESDAY EXPECTED TO BE DRY AND SEASONAL BUT
BREEZY.

.WEDNESDAY NIGHT THROUGH SUNDAY...CONFIDENCE - MEDIUM.

SECONDARY SHORT WAVE TROF AND SURGE OF COLD AIR MAY BRING SOME LIGHT
SNOW OR SNOW SHOWERS TO SRN WI WED NGT INTO THU.  YET ANOTHER PIECE
OF ENERGY CAUGHT IN INCREASING NORTHWEST FLOW FROM S CENTRAL CANADA
MAY AFFECT THE WRN GTLAKES THU NGT.  INCREASING COLD FLOW A RESULT
OF AMPLIFYING LONG WAVE TROF OVER ERN CONUS.  HENCE WE NEED TO BRACE
FOR MORE BELOW NORMAL TEMPS TO FINISH OFF THE WORK WEEK.  NORMAL
HIGHS REACH 46-48 BY THIS PERIOD.  SRN WI LIKELY TO BE 5 TO 10
DEGREES BELOW NORMAL THU/FRI.

SOME SHORT TERM WARMING IS EXPECTED OVER THE WEEKEND HOWEVER BOTH
ECMWF AND GFS IN REASONABLE AGREEMENT ON STRONG NORTHWEST CLIPPER
SYSTEM MOVING ACROSS THE AREA IN THE SUN/SUN NGT TIME FRAME.
HOWEVER MEDIUM RANGE GUIDANCE HAS SOME DIFFERENCES IN TRACK AND
TIMING OF THIS CLIPPER SYSTEM.  FASTER ECMWF SOLUTION RESULTS IN A
BETTER CHANCE FOR MIXED PRECIP AT THE ONSET SATURDAY NIGHT...WHILE
GFS SLOWER...ALLOWING FOR MORE DAYTIME HEATING AND BETTER CHANCE FOR
MORE LIQUID PRECIP ON SUN.  BULK OF THE PRECIP WITH THIS SYSTEM
LOOKS TO BE LIQUID.  THIS SYSTEM LOOKING VERY DYNAMIC...SIMILAR TO
TUESDAY...AS TO BE EXPECTED IN LATE MARCH.

500H 5 DAY ANOMOLIES BASED ON THE GFS CONTINUES TO SHOW THE LARGE
NEGATIVE ANOMOLY OVER ERN NOAM AT 00Z/29 EASING A BIT OVER THE GREAT
LAKES BY THE START OF APRIL AS LONG WAVE TROF WEAKENS.

&&

.AVIATION/00Z TAFS/...

MID CLOUDS COVER ALL OF SOUTHERN WI WITH MID LEVEL FRONTOGENESIS...
BUT A STEADY FEED OF DRY AIR ON A BRISK EASTERLY BREEZE IS HELPING
TO FEND OFF ANY PRECIP AT THE GROUND... THUS VIRGA PREVAILS AT THE
EASTERN TAF SITES.

A BAND OF MODERATE SNOW SPREAD INTO SOUTHWEST AND SOUTH CENTRAL WI
THIS AFTERNOON AND COULD LINGER INTO THE EARLY EVENING. THE SNOW IS
REMAINING SOUTH OF MADISON AS OF 3 PM... BUT OBSERVATIONS UPSTREAM
SHOW A GOOD CHANCE OF IT SPREADING INTO MSN THROUGH 7 PM. SEE THE
MAIN FORECAST DISCUSSION FOR DETAILS.

ANOTHER ROUND OF MORE WIDESPREAD... STEADY SNOW WILL SLIDE INTO
SOUTHERN WISCONSIN AROUND MIDNIGHT TONIGHT AND LINGER THROUGH MONDAY
MORNING. THE HEAVIEST SNOW WILL BE STAYING MAINLY TO THE WEST AND
SOUTH OF A DELLS TO MADISON TO JANESVILLE LINE. SEE THE LATEST
SNOWFALL GRAPHICS ON OUR WEBSITE. FREEZING DRIZZLE IS LOOKING LESS
LIKELY FOR MONDAY MORNING BUT CANNOT RULE IT OUT COMPLETELY.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...

WI...WINTER WX ADVY UNTIL 8 AM CDT MONDAY FOR WIZ056-062-063-
     067>069.
LM...NONE.

$$
TONIGHT AND MONDAY/AVIATION...MRC
MONDAY NIGHT THROUGH SUNDAY/MARINE...MBK


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