Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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000
FXUS63 KMKX 200303
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
903 PM CST FRI DEC 19 2014

.UPDATE...

WILL DELAY ANY FREEZING DRIZZLE. LATEST NAM DOES NOT SATURATE THE
925 MB AND BELOW AREA AS FAST.

&&

.AVIATION/06Z TAFS/...

SOUNDINGS CONTINUE TO SHOW SOME LOW LEVEL MOISTURE TRAPPED BELOW
AN INVERSION AROUND 3 KFT. DURING THE NIGHT WEAK WESTERLY MIDLEVEL
FLOW WILL BE PUSHING LOW AND MIDLEVEL CLOUDS EASTWARD ACROSS
SOUTHERN WI. WILL DELAY ANY FREEZING DRIZZLE. LATEST NAM DOES NOT
SATURATE THE 925 MB AND BELOW AREA AS FAST. THERE WILL BE A RATHER
CHAOTIC MIX OF MVFR AND VFR CIGS. SOME OF THE LAKE CLOUD CIGS
WILL BE MVFR...ALONG WITH LINGERING AREAS OVER SOUTH CENTRAL
WISCONSIN. AS MOISTURE INCREASES DURING THE DAY SATURDAY MORE MVFR
CIGS EXPECTED.

&&

.PREV DISCUSSION... /ISSUED 350 PM CST FRI DEC 19 2014/

TONIGHT AND SATURDAY...FORECAST CONFIDENCE IS MEDIUM.

HIGH PRESSURE WILL SLOWLY MOVE EAST TONIGHT BEFORE WEAK SOUTHERLY
FLOW STARTS TO TAKE OVER ON SAT. WARM AIR ADVECTION ON SOUTHWEST
FLOW KICKS IN THIS EVENING AHEAD OF A MID LEVEL SHORTWAVE MOVING
ACROSS NORTHERN ILLINOIS ON SAT. ISENTROPIC LIFT AND NAM/GFS
SOUNDINGS SUPPORT THE POTENTIAL FOR LIGHT FREEZING DRIZZLE SAT
MORNING. THE GREATEST CHANCE IS FROM MADISON WESTWARD WHERE
SOUNDINGS ARE MORE SATURATED. NAM MAY BE OVERDOING THE MOISTURE BUT
SINCE GFS DOES SHOW DRIZZLE POTENTIAL HAVE ADDED IT TO THE FORECAST.
SOME DRIZZLE IS POSSIBLE IN SE WI DURING THE AFTERNOON BUT
CONFIDENCE IS NOT AS HIGH SO LEFT OUT OF FORECAST. CLOUDS ARE
EXPECTED TO LINGER THROUGH SAT.

SATURDAY NIGHT THROUGH SUNDAY NIGHT...FORECAST CONFIDENCE IS
MEDIUM.

THE MID LEVEL FLOW UNDERGOES A TRANSITION FROM A LOW AMPLITUDE
NORTHWEST FLOW TO A HIGHER AMPLITUDE SOUTHWEST FLOW AS A CLOSED
UPPER LEVEL LOW FORMS OVER THE NORTHERN HIGH PLAINS BY SUNDAY
NIGHT.

THE INCREASING SOUTHERLY COMPONENT TO THE OVERALL FLOW WILL BRING
OUR FIRST SHOT OF WARM ADVECTION THAT COULD RESULT IN SOME LIGHT
FREEZING DRIZZLE WEST OF MADISON SATURDAY NIGHT. AS THE WARMER AND
MORE MOIST FLOW CONTINUES...COMBINED WITH SOME EJECTING SHORT WAVE
ENERGY...THE CHANCE OF FREEZING RAIN POSSIBLY MIXED WITH SNOW
WILL CONTINUE INTO SUNDAY MORNING. AS TEMPS WARM ON SUNDAY...ANY
FREEZING PRECIP WILL TRANSITION TO A LIGHT RAIN/SNOW MIX...OR JUST
LIGHT RAIN. LOOK FOR THESE SMALL CHANCES TO PERSIST INTO SUNDAY
NIGHT AS LOW PRESSURE ORGANIZES WEST OF WISCONSIN.

MONDAY AND TUESDAY...FORECAST CONFIDENCE IS MEDIUM.

MOST OF THE MODELS ARE IN GENERALLY GOOD AGREEMENT THROUGH THIS
PERIOD. THE UPPER LOW CONTINUES TO DIG INTO THE UPPER MIDWEST AND
WESTERN GREAT LAKES THROUGH TUESDAY. THE CORRESPONDING SURFACE
LOW SHOULD TRACK FROM THE EASTERN DAKOTAS TO SOUTHERN LAKE
MICHIGAN BY TUESDAY AFTERNOON. THIS IS A FAIRLY WARM SOLUTION WITH
MOST OF THE AREA LIKELY TO JUST SEE SOME RAIN. SOME AREAS WILL SEE
A RAIN/SNOW MIX...MAINLY NORTH AND WEST OF MADISON...BUT IMPACT
UP TO THIS POINT SHOULD BE MINIMAL.

WEDNESDAY AND THURSDAY...FORECAST CONFIDENCE IS LOW.

AT THIS POINT THE MODELS DIVERGE SIGNIFICANTLY. THERE IS LOTS OF
CHATTER OUT THERE ABOUT A RAPIDLY DEEPENING LOW PRESSURE SYSTEM
THAT WILL IMPACT HOLIDAY TRAVEL. WE HAVE 3 PRIMARY MODELS TO USE
AT THIS POINT. THE GFS TRACKS AND DEEPENS THE LOW UP OVER FAR NRN
WI AND THE UPPER PENINSULA. THIS SCENARIO IS FAIRLY LOW IN IMPACT
FOR SOUTHERN WISCONSIN WITH COLD ADVECTION KICKING IN LATER
TUESDAY NIGHT WITH LIGHT RAIN CHANGING TO LIGHT SNOW. WE COULD SEE
AN INCH OR TWO OF ACCUMULATION OVER A FAIRLY LONG PERIOD.

THE SECOND SOLUTION IS FROM THE EUROPEAN ECMWF MODEL. IT HAS BEEN
THE MOST AGGRESSIVE WITH A VERY RAPID DEEPENING...MAY REACH BOMB
STATUS...WED THROUGH WED NIGHT. THIS OCCURS FARTHER EAST...
TRACKING FROM OHIO TO LAKE HURON. THIS WOULD LIKELY HAVE EVEN
LESS IMPACT AS THE ASSOCIATED PRECIP WOULD STAY MOSTLY TO OUR
EAST. WE WOULD JUST SEE STRONG COLD ADVECTION WITH SOME VERY
STRONG/GUSTY NORTHWEST WINDS. SOME LIGHT SNOW WOULD BE
POSSIBLE...BUT ACCUMS WOULD BE MORE LIMITED THAN EVEN THE GFS.

THE THIRD SOLUTION IS THE CANADIAN GEM AND IT/S TRACK LOOKS LIKE
BLEND OF THE GFS AND THE ECMWF...TRACKING THE LOW OVER SOUTHWEST
LOWER MICHIGAN WITH TIME. THIS TRACK WOULD HAVE THE GREATEST
IMPACT ON SOUTHERN WISCONSIN...POTENTIALLY BRINGING HIGHER
ACCUMULATING SNOWS THAT WOULD INTRODUCE TRAVEL HAZARDS FOR
WEDNESDAY.

GIVEN THE WIDE VARIABILITY IN THE OPERATIONAL RUNS AND THE
INDIVIDUAL MODEL ENSEMBLE SOLUTIONS...CONFIDENCE IN ANY ONE
SOLUTION IS QUITE LOW AT THIS POINT. THE CURRENT FCST IS HEDGED
TOWARD THE GFS SINCE IT/S ENSEMBLE SUITE AND OPERATIONAL TRACK
HAVE BEEN THE MOST CONSISTENT.

FRIDAY...FORECAST CONFIDENCE IS LOW.

THERE IS EVIDENCE THAT A SECONDARY LOW DEVELOPMENT...WHICH MAY BE
A CLIPPER MERGING WITH SOME ENERGY FROM THE SOUTHERN
STREAM...COULD BRING US A ROUND OF SNOW THE DAY AFTER CHRISTMAS.
THAT ONE COULD BE INTERESTING.

AVIATION/00Z TAFS/...

SATELLITE IMAGERY SHOWS LAKE EFFECT CLOUDS CONTINUE TO MOVE INLAND
OVER SE WI. DUE TO STATIONARY SURFACE FLOW...EXPECT THESE VFR CLOUDS
TO CONTINUE THROUGH MOST OF THE NIGHT AT EASTERN TAF SITES WHILE
MVFR CEILINGS SHOULD CONTINUE AT MSN. SOUNDINGS CONTINUE TO SHOW LOW
LEVEL MOISTURE TRAPPED BELOW AN INVERSION AROUND 3 KFT. DURING THE
NIGHT WEAK WESTERLY MIDLEVEL FLOW WILL BE PUSHING LOW AND MIDLEVEL
CLOUDS EASTWARD ACROSS SOUTHERN WI. THIS MAY LEAD TO FREEZING
DRIZZLE OR LIGHT SNOW IN THE MORNING AT MSN AND UES AND LATE MORNING
TO EARLY AFTERNOON AT MKE AND ENW.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...NONE.
&&

$$

UPDATE...HENTZ
TONIGHT/SATURDAY AND AVIATION/MARINE...MARQUARDT
SATURDAY NIGHT THROUGH FRIDAY...DAVIS


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