Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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000
FXUS63 KMKX 042109
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
310 PM CST WED MAR 4 2015

.TONIGHT AND THURSDAY...CONFIDENCE - HIGH.

SURFACE HIGH PRESSURE OVER THE NORTHERN PLAINS WILL SLIDE INTO IOWA
TONIGHT AND ILLINOIS ON THURSDAY. THE PRESSURE GRADIENT SHOULD
BECOME WEAK ENOUGH OVER SOUTHERN WI TO ALLOW FOR DECOUPLING LATE
TONIGHT AND THUS LIGHT WINDS. I UNDERCUT MODEL BLENDS A BIT TO DROP
TEMPS INTO THE SINGLE DIGITS BELOW ZERO... MOS GUIDANCE WAS ALREADY
ON THE LOWER SIDE BUT THE MODEL BLENDS WERE HIGHER. MINIMUM WIND
CHILLS WILL BE IN THE -12 TO -19F RANGE. A FEW AREAS MAY HIT -20 FOR
AN HOUR OR TWO... BUT OPTED NOT TO ISSUE A WIND CHILL ADVISORY GIVEN
THE MARGINAL CONDITIONS. PER COORDINATION WITH NEIGHBORING
OFFICES... ISSUED A SPECIAL WEATHER STATEMENT.

THERE IS A FAIR AMOUNT OF CLOUD COVER OVER SOUTHERN MN THIS
AFTERNOON... ASSOCIATED WITH A LOW LEVEL THERMAL TROUGH AND MID
LEVEL VORTICITY ADVECTION. THIS APPEARS TO BE SUPPORTED BY STEEP LOW
LEVEL LAPSE RATES. EXPECT THE LAPSE RATES TO WEAKEN AFTER DARK BY
THE TIME THE THERMAL TROUGH SLIDES ACROSS SOUTHWEST/SOUTH CENTRAL WI
OVERNIGHT. THUS... EXPECTING CLEAR SKIES THROUGH THE NIGHT.

PLAN ON ABUNDANT SUNSHINE AND A LIGHT WESTERLY BREEZE ON THURSDAY AS
THE HIGH PRESSURE RIDGE SLIDES INTO ILLINOIS. HIGHS WILL ONLY BE IN
THE LOWER TO MID TEENS... SLIGHTLY COLDER THAN TODAY.

.THURSDAY NIGHT THROUGH SATURDAY...CONFIDENCE - MEDIUM.

INCREASING LOW LEVEL WESTERLY WINDS TO THE NORTH OF SPRAWLING HIGH
PRESSURE WL DEVELOP LATER THURSDAY NIGHT AND CARRY INTO FRIDAY...AND
WILL COMMENCE FIRST SURGE OF LONG AWAITED WARM AIR ADVECTION. 925H
TEMPS WARM 10 TO 15C THRU FRIDAY ON BREZY WEST TO SOUTHWEST WINDS.
COLUMN MOISTURE WILL BE LIMITED WITH THIS FIRST
SURGE...ESPECIALLY ABOVE 4K FEET.  WEAK WAA AND PASSING WEAK LOW
PRESSURE TROF MAY BE ABLE TO SHAKE OUT A FEW FLURRIES ON FRIDAY.

COLUMN MOISTURE CONTINUES TO INCREASE FRIDAY NIGHT INTO
SATURDAY...AS PRECIPITABLE WATER RISES TO .4 TO .5 INCH...WHICH IS
REACHING THE 75TH PERCENTILE FOR EARLY MARCH.  NAM AND GFS SHOWING
COMPACT SHORT WAVE TROF PASSING ACROSS SRN WI REGION ON SAT...WHILE
ECMWF MUCH WEAKER AND FARTHER NORTH.  DUE TO INCONSISTENCIES IN
SHORT TERM GUIDANCE...WL CONTINUE DRY FORECAST FOR SATURDAY.  WOULD
NOT BE SURPRISED IF FUTURE SHIFTS ADD AT LEAST LOW POPS FOR -SN FOR
THIS PERIOD HOWEVER.  EVEN WITH CLOUD COVER...DAYTIME TEMPS SHOULD
WARM INTO THE MID TO UPPER 30S ON SAT...AFTER STARTING OUT IN THE
20S THAT MRNG.

.SATURDAY NIGHT THROUGH WEDNESDAY...CONFIDENCE - MEDIUM.

THE MAIN FOCUS DURING THIS PERIOD REMAINS THE SHIFTING WEATHER
PATTERN AND STEERING WINDS.  MEDIUM RANGE GUIDANCE IN REASONABLE
AGREEMENT ON WEAKENING PERSISTENT POLAR LOW PRESSURE LOCATED IN NRN
QUEBEC/HUDSON STRAIT VCNTY.  AS A RESULT OF WEAKENING LOW ALONG WITH
APPROACHING AMPLIFYING SHORT WAVE TROF IN THE PACIFIC
NORTHWEST...STEERING WINDS TO BECOME MORE ZONAL DURING THIS PERIOD.
THIS WILL ALLOW WARMER...MORE SEASONAL CONDITIONS TO FINALLY RETURN
TO THE REGION.  85H TEMPS EXPECTED TO RISE ABV ZERO F MONDAY AND
POSSIBLY APPROACH 8-10C BY WED.  THIS WILL DEPEND UPON TIMING OF
PASSING WEAK LOW PRESSURE WELL TO THE NORTH.  TUESDAY MORNING
YIELDED 1 TO 4 INCHES OF FRESH MOISTURE LADEN SNOW ACROSS SRN CWA SO
WL TAKE A LITTLE MORE TIME TO MELT...HOWEVER THIS DEEPER SNOWPACK
CONFINED TO SRN CWA INTO NORTHERN IL.  OLD SNOW COVER PRIOR TO TUE
EVENT HAS MUCH LESS SNOW-WATER EQUIVALENT TO WORK WITH...SO WL MELT
MORE RAPIDLY NEXT WEEK.  EXPECT AREAS OF ICE LINGERING IN NEAR SHORE
WATERS TO MELT AND SOME LAND AREAS TO LOSE MAJORITY OF SNOW COVER BY
THE END OF NEXT WEEK.  COLUMN REMAINS FAIRLY DRY DURING THE EXTENDED
PERIOD SO NO SIGNIFICANT PRECIP EXPECTED AS TEMPS WARM.  HOWEVER WL
HAVE TO WATCH FOR SNEAKY STRATUS DEVELOPMENT AS UPSTREAM SNOW COVER
BEGINS TO MELT IN SOUTHWEST LOW LEVEL FLOW.

500H 5-DAY ANOMALY FORECAST BASED ON THE GFS SHOWS HEIGHTS RISING TO
OVER 50METER ABOVE NORMAL CENTERED AT 00Z/12 ACROSS THE WESTERN
GTLAKES.

&&

.AVIATION/00Z TAFS/...

DRY AIR WILL ALLOW FOR NEARLY CLEAR SKIES OVER THE REGION TONIGHT
AND THURSDAY. THE GUSTY WNW WINDS WILL DIMINISH THIS EVENING AS HIGH
PRESSURE SLIDES FROM THE NORTHERN PLAINS THROUGH IOWA TONIGHT AND
INTO ILLINOIS ON THURSDAY.

&&

.MARINE...

WILL CONTINUE SMALL CRAFT ADVY THROUGH THE AFTERNOON DUE TO
OCCASIONAL NORTHWESTERLY GUSTS TO AROUND 25KTS. A WEAKENING PRESSURE
GRADIENT WILL ALLOW GUSTS TO GRADUALLY DIMINISH EARLY THIS EVE.
LATEST VISIBLE HI RES IMAGERY TODAY SHOWED MORE OPEN WATER SO KEPT
WAVES IN THE NEARSHORE FORECAST.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...

WI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 6 PM CST THIS EVENING FOR LMZ643>646.

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



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