Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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000
FXUS63 KMKX 180234
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
934 PM CDT WED SEP 17 2014

.UPDATE...BACK DOOR CDFNT EXTENDS FROM NEAR KMTW TO NEAR KSTE AND
IS PROGRESSIVING STEADILY SOUTHWARD. SHOULD MOVE ACROSS SRN WI
BETWEEN 04Z AND 10Z. MOIST LOW LEVEL FLOW IN ITS WAKE AND COLD AIR
ADVECTION EXPECTED TO PRODUCE INCREASING STRATUS FIELD ACROSS MOST
OF CWA AFTER 06Z. STRATUS WILL LIKELY STICK AROUND FOR A TIME ON
THURSDAY DUE TO LINGERING THERMAL TROUGH AND MOIST NORTHEAST FLOW.

PATCHY LIGHT FOG LIKELY TO DEVELOP IN SUSCEPTIBLE AREAS UNTIL
WINDS PICKUP BEHIND CDFNT. LOWERED MINIMUM TEMPS A FEW LOCATIONS
AS COLDER AIR SETTLES IN LATE.

&&

.AVIATION/06Z TAFS/...SOME LIGHT FOG MAY DEVELOP AROUND OR SHORTLY
AFTER MIDNIGHT...HOWEVER INCREASING NORTHEAST WINDS BEHIND CDFNT
WILL SCOUR MOST OF THE FOG OUT LATER TONIGHT. EXPECT IFR STRATUS
TO AFFECT ALL TAF SITES LATER TONIGHT THRU THU MRNG BEFORE
LIFTING.

&&

.MARINE...STILL THINKING A 1 TO 3 HOUR PERIOD OF GUSTY WINDS
EXCEEDING 22 KNOTS EXPECTED TO AFFECT NORTHERN MARINE ZONE AFTER
BACK DOOR COLD FRONT MOVES THROUGH. CDFNT SHOULD MOVE THROUGH
SGNW3 AROUND 04Z...REACHING WINTHROP HARBOR AROUND 07-08Z. WL
ISSUE MWS TO HIGHLIGHT ABRUPT WIND SHIFT AND INCREASE IN WIND SPEED.

&&

.PREV DISCUSSION... /ISSUED 341 PM CDT WED SEP 17 2014/

TONIGHT AND THURSDAY...FORECAST CONFIDENCE IS HIGH.

SURFACE HIGH PRESSURE OVER THE OHIO RIVER VALLEY AND EASTERN GREAT
LAKES WILL CONTINUE TO SLIDE EAST OVERNIGHT. MEANWHILE...AN UPPER
TROUGH WILL AMPLIFY OVER HUDSON BAY AND PUSH A COLD FRONT DOWN
THROUGH MICHIGAN AND WISCONSIN. THIS FRONT WILL ACCELERATE DOWN THE
LONG AXIS OF LAKE MICHIGAN OVERNIGHT AND GRADUALLY SPREAD INLAND
TOWARD CENTRAL WI AND MADISON. WE CALL THIS A BACK DOOR COLD FRONT.

THE LEADING EDGE OF THE FRONT SHOULD ARRIVE IN SHEBOYGAN AROUND
MIDNIGHT...MADISON AND MILWAUKEE BY 3 AM...AND KENOSHA BY 6 AM. THE
FRONT WILL COME THROUGH DRY...JUST SOME GUSTY NORTHEAST WINDS. WINDS
WILL WEAKEN...BUT EXPECT LOW CLOUDS ALONG AND BEHIND THE FRONT TO
LINGER THROUGH THURSDAY MORNING. THEY WILL GRADUALLY BREAK UP AND
SCATTER TOWARD LATE AFTERNOON...ESPECIALLY IN SOUTHEAST WI.
THUS...UNDERCUT GUIDANCE FOR MAX TEMPS.

THURSDAY NIGHT TO FRIDAY NIGHT...FORECAST CONFIDENCE HIGH.

SOUTHEAST WINDS ON THE BACKSIDE OF HIGH PRESSURE WILL BECOME
SOUTHERLY ON FRIDAY AHEAD OF LOW PRESSURE APPROACHING FROM THE
NORTHWEST. MODELS ARE IN GOOD AGREEMENT KEEPING THE AREA DRY THROUGH
FRIDAY AFTERNOON AS THE MAIN CORE OF PRECIPITATION ASSOCIATED WITH
WARM AIR ADVECTION AND SHORTWAVE ENERGY WILL BE TO THE NORTHWEST.
THE EUROPEAN AND SREF INDICATE LIGHT QPF FOR THE NORTHERN HALF OF
THE CWA FRIDAY EVENING. THINK LIGHT SHOWERS ARE POSSIBLE GIVEN THE
INCREASING MOISTURE AND FAVORABLE LOW LEVEL Q VECTOR CONVERGENCE AND
FRONTOGENESIS FIELDS BRUSHING THE NORTHWEST CWA. PRECIP MORE LIKELY
IN THE NORTHWEST CWA OVERNIGHT AS THE SURFACE TROUGH AND LOW
LEVEL JET MOVES CLOSER TO THE REGION.

SATURDAY AND SATURDAY NIGHT...FORECAST CONFIDENCE MEDIUM.

DEW POINTS WILL SURGE UPWARD INTO THE 60S ON SATURDAY AS THE LOW
LEVEL JET RAMPS UP OVER SOUTHERN WISCONSIN. PRECIP EXPECTED SOMETIME
ON SATURDAY WITH THUNDERSTORMS POSSIBLE DUE TO ABOUT 1500 MU CAPE.
THERE IS CONSIDERABLE UNCERTAINTY WITH THE TIMING OF THE PRECIP
DESPITE GOOD AGREEMENT ON THE TIMING OF THE FRONTAL PASSAGE. THE
EUROPEAN INDICATES A MORNING PRECIP EVENT WITH AFTERNOON PRECIP
REDEVELOPING SOUTHEAST OF OUR AREA WHILE THE GFS IS DRY UNTIL THE
AFTERNOON. WENT WITH MODEL CONSENSUS OF PRECIP CHANCES THROUGHOUT
THE DAY DUE TO THIS UNCERTAINTY. SURFACE TROUGH SHOWN TO EXIT THE
SOUTHEAST LATE IN THE EVENING BRINGING A QUICK END TO THE MAIN CORE
OF PRECIPITATION.

SUNDAY THROUGH WEDNESDAY...FORECAST CONFIDENCE HIGH.

GFS AND CANADIAN MODELS DIG A DEEP UPPER TROUGH DOWN THROUGH THE
REGION ON SUNDAY. A FEW SHOWERS MAY LINGER INTO SUNDAY MORNING IN
THE EAST WITH THIS CYCLONIC FLOW. THE EURO IS A LITTLE LATER
DEVELOPING THIS FEATURE RESULTING IN SOME LIGHT QPF ON MONDAY IN THE
EAST. HAVE VERY LOW POPS IN THE FORECAST TO REFLECT THIS
POSSIBILITY BUT WITH HIGH PRESSURE MOVING INTO THE REGION EXPECT
OTHERWISE DRY CONDITIONS DURING THIS TIME. THE UPPER TROUGH SLIDES
EAST ON MONDAY PUTTING SOUTHERN WISCONSIN IS UNDER A 500MB RIDGE
BY WEDNESDAY.

AVIATION/00Z TAFS/...

MOSTLY CLEAR SKIES AND LIGHT WINDS THIS EVENING MAY LEAD TO PATCHY
LIGHT FOG. THEN A POTENT BUT DRY COLD FRONT WILL DROP SOUTHWESTWARD
ACROSS SOUTHERN WI AFTER MIDNIGHT TONIGHT. THE FRONT WILL ACCELERATE
DOWN LAKE MICHIGAN RESULTING IN A PERIOD OF BRISK NORTHEAST WINDS
FOR KMKE/KUES/KENW FROM ABOUT 06-09Z THU.  IN ADDITION...IT LOOKS
LIKE A PERIOD OF IFR OR LOWER CIGS WILL DEVELOP IN THE
COOLER...MOIST AIR BEHIND THE FRONT AND THEN LINGER INTO THURSDAY
BEFORE LIFTING AND SCATTERING OUT.

MARINE...

WINDS WILL QUICKLY INCREASE OUT OF THE NORTHEAST TONIGHT AS A DRY
COLD FRONT DROPS DOWN LAKE MICHIGAN. WIND GUSTS WILL APPROACH SMALL
CRAFT ADVISORY CRITERIA FOR A FEW HOURS JUST BEHIND THE FRONT AND
DIMINISH EARLY THURSDAY MORNING. WAVES ARE EXPECTED TO RISE TO
AROUND 4 FEET FOR UP TO 6 HOURS AND THEN SUBSIDE. THEREFORE AT THIS
TIME... WE ARE NOT PLANNING ON ISSUING A SMALL CRAFT ADVISORY FOR
THIS EVENT.

&&

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

$$

UPDATE...MBK



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