Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 090857
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
357 AM CDT TUE SEP 9 2014

.TODAY AND TONIGHT...FORECAST CONFIDENCE IS HIGH.

THE UPPER TROUGH OVER THE WESTERN U.S. WILL MOVE INTO THE
NORTHERN AND CENTRAL ROCKIES THIS AFTERNOON AND INTO THE NORTHERN
AND CENTRAL PLAINS TONIGHT. A 100 KNOT 250 MB JET ALREADY EXTENDS
ACROSS NEVADA AND INTO THE CENTRAL PLAINS.

ONE INITIAL JET MAX OF 85 KNOTS MOVES ACROSS SOUTHERN WISCONSIN
TODAY...WHILE THE STRONGER JET MAX IS OVER NEBRASKA LATE TONIGHT
WITH SOUTHERN WISCONSIN IN THE EXIT REGION. WEAK TO MODERATE UPPER
DIVERGENCE MOVES ACROSS SOUTHERN WISCONSIN WITH THE FIRST JET
MAX...THEN STRONG DIVERGENCE MOVES INTO SOUTHERN WISCONSIN DURING
THE EARLY MORNING HOURS WEDNESDAY.

700 MB WARM AIR ADVECTION TODAY BECOMES QUITE STRONG TONIGHT...AS
A LOW STARTS TO INTENSIFY. THE 700 MB SOUTH WINDS INCREASE TO 25
KNOTS THIS EVENING...AND TO 50 KNOTS EARLY WEDNESDAY MORNING WITH
STRONG MOISTURE CONVERGENCE. 850 MB LAYER IS SIMILAR WITH A 55
KNOT 850 MB JET PUSHING INTO SOUTHERN WISCONSIN DURING THE EARLY
MORNING HOURS.

THIS RESULTS IN STRONG 700 MB UPWARD MOTION DURING THE EARLY
MORNING HOURS. WITH THE STRONG CYCLOGENESIS THE ATMOSPHERE BECOMES
SATURATED WITH MODELS MAINLY MOIST ADIABATIC RESULTING IN LOW
CAPE. HOWEVER STRONG WINDS/SHEAR PRESENT SO SEVERE THREAT WOULD BE
WINDS...MAINLY OVER SOUTH CENTRAL WISCONSIN WHERE SPC HAS A SLIGHT
RISK OF SEVERE.

MAIN CONCERN WILL BE HEAVY RAINFALL. PRECIPITABLE WATER VALUES
RISE TO AROUND 2.20 INCHES ALONG THE ILLINOIS BORDER BY 7 AM CDT
WEDNESDAY...TO ALMOST 2 INCHES NORTH TOWARD THE DELLS/FOND DU LAC
AND SHEBOYGAN.

MOST MODELS ARE SHOWING 1.50 TO 2.00 INCHES OF RAINFALL FOR SOUTH
CENTRAL WISCONSIN...WITH THE HEAVY RAINS JUST BEGINNING LATE OVER
THE FAR SOUTHEAST. HOWEVER WITH THE FAIRLY QUICK PROGRESSION OF
THE STRONG DYNAMICS...EXPECT THE MAIN FLOODING CONCERNS EARLY
WEDNESDAY MORNING TO BE URBAN AND LOW LAND FLOODING IN SOUTH
CENTRAL WISCONSIN.

FLASH FLOOD VALUES ARE FAIRLY HIGH WITH 3 HOUR FLASH FLOOD VALUES
AROUND 2.50 INCHES AND 6 HOUR TOTALS NEAR 3.00 INCHES. OF
COURSE...URBAN AREAS WILL BE LESS. THE WPC SLIGHT RISK OF
EXCESSIVE RAINFALL DURING THIS TIME FRAME EXTENDS INTO AREAS
SOUTHWEST OF MADISON...MAINLY TOWARD THE ILLINOIS BORDER.

.SHORT TERM...WEDNESDAY THROUGH THURSDAY NIGHT...FORECAST
CONFIDENCE IS HIGH.

SHORT TERM MODELS CONTINUE SHOW SURFACE LOW UNDERGOING
CYCLOGENESIS AS IT SHIFTS FROM NORTHEAST IOWA INTO NORTHERN LOWER
MICHIGAN ON WEDNESDAY. STRONG UPWARD VERTICAL MOTION CONTINUES
INTO THE MORNING HOURS WEDNESDAY...PER AREA FORECAST SOUNDINGS
FROM NAM/GFS.

ELEVATED CAPE IS MODEST WITH MOIST ADIABATIC LAPSE RATES...WITH
VERY STRONG VERTICAL WIND SHEAR. COULD STILL SEE GUSTY WINDS WITH
STRONGER STORMS IN THE MORNING HOURS...AS STRONG LOW LEVEL WINDS
COULD BE TRANSFERRED TO THE SURFACE WITH STORMS.

MAINTAINED HEAVY RAINFALL WORDING IN FORECAST 12Z TO 15Z
WEDNESDAY...AS PRECIPITABLE WATER VALUES REMAIN AROUND 2 INCHES
ACROSS THE AREA WITH STRONG UPWARD VERTICAL MOTION. ANOTHER 1/2 TO
1 INCH OF RAINFALL IS POSSIBLE WEDNESDAY MORNING...HIGHEST IN THE
EAST. AS STATED EARLIER...MAINLY URBAN AND LOWLAND FLOODING RISK
GIVEN QUICK PROGRESSION OF STORMS. WPC KEEPS AREA OUT OF EXCESSIVE
RAINFALL OUTLOOK ON WEDNESDAY.

STRONG 850 MB LOW LEVEL JET NOSE OVER THE AREA AT 12Z WEDNESDAY
SHIFTS NORTHEAST BY 18Z WEDNESDAY...TAKING THE BEST UPWARD
VERTICAL MOTION OUT OF THE AREA BY THE AFTERNOON. KEPT POPS FOR
SHOWERS GOING IN AFTERNOON...WITH 500 MB VORTICITY MAXIMUM MOVING
INTO THE AREA LATER IN THE DAY. KEPT LIKELY POPS AND CHANCES FOR
THUNDER IN THE FAR SOUTHEAST...NEAR BEST LOW LEVEL FRONTOGENESIS
RESPONSE WITH PASSING COLD FRONT.

FAR SOUTHEAST COUNTIES REMAIN IN SPC DAY 2 SLIGHT RISK FOR SEVERE
STORMS...AS COLD FRONT MOVES THROUGH THAT AREA LATER IN THE
AFTERNOON. FEEL THE BEST CHANCES FOR SEVERE STORMS WILL REMAIN TO
THE SOUTH AND EAST OF THE AREA...WHERE BETTER INSTABILITY WILL
RESIDE. STRONG DEEP LAYER SHEAR WILL REMAIN WEDNESDAY
AFTERNOON...SO CANNOT RULE OUT SEVERE TOTALLY.

STRONG COLD AIR ADVECTION...WITH BRISK NORTHWEST WINDS...WILL
BRING MUCH COOLER AND DRIER AIR INTO THE REGION BY WEDNESDAY NIGHT
INTO THURSDAY. THIS WILL QUICKLY DRY THINGS OUT ACROSS THE AREA.
DRY CONDITIONS WILL THEN LINGER THURSDAY AND THURSDAY NIGHT...WITH
COOL TEMPERATURES CONTINUING. HIGHS WILL STRUGGLE TO REACH 60 ON
THURSDAY...WITH LOWS IN THE LOWER TO MID 40S INLAND THURSDAY
NIGHT.

.LONG TERM...FRIDAY THROUGH MONDAY...FORECAST CONFIDENCE IS HIGH.

ECMWF/GFS IN AGREEMENT WITH BRINGING A STRONG 500 MB SHORTWAVE
TROUGH EAST THROUGH THE AREA LATER FRIDAY INTO FRIDAY NIGHT. AREA
FORECAST SOUNDINGS FROM GFS SHOWING DEEP LAYER SATURATION DURING
THIS PERIOD...WHICH RESULTS IN CHANCES FOR SHOWERS ACROSS THE
AREA.

HIGH PRESSURE THEN BRINGS QUIET WEATHER FOR SATURDAY INTO SUNDAY
NIGHT...WITH COOL TEMPERATURES LINGERING ACROSS THE AREA.
GFS/ECMWF THEN DISAGREE WITH TIMING ON NEXT SYSTEM FOR EARLY NEXT
WEEK. USED CONSENSUS MODEL BLENDED POPS AND TEMPERATURES FOR
MONDAY.

&&

.AVIATION/12Z TAFS/...

CLOUDS WILL INCREASE AND CIGS LOWER TODAY...AHEAD OF DEVELOPING
LOW PRESSURE EXITING THE COLORADO HIGH PLAINS AND INTO THE
IOWA/MINNESOTA AREA DURING THE EARLY MORNING HOURS. THE LOW THEN
BEGINS TO RAPIDLY INTENSIFY.

SOME PATCHY MVFR/IFR FOG...MAINLY IN LOW AREAS UNTIL JUST AFTER
SUNRISE. THEN MAINLY VFR CIGS/VSBYS TODAY...ALTHOUGH SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS ARE POSSIBLE MAINLY OVER SOUTH
CENTRAL WISCONSIN TODAY. CIGS/VSBYS WILL BECOME IFR LATE
TONIGHT...AS HEAVY RAIN AND THUNDERSTORMS MOVE ACROSS SOUTHERN
WISCONSIN.

SOME LOW LEVEL WIND SHEAR CONCERNS...AS THE LOW LEVEL JET OF 55
KNOTS PUSHES INTO SOUTHERN WISCONSIN TONIGHT.

&&

.MARINE...

WINDS/WAVES WILL LIKELY REACH SMALL CRAFT ADVISORY CONDITIONS
LATE TONIGHT...AND APPROACH GALE WARNING CRITERIA ON WEDNESDAY AND
WEDNESDAY EVENING...AS AN UNUSUALLY STRONG EARLY SEASON LOW
INTENSIFIES OVER WISCONSIN WEDNESDAY.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...SMALL CRAFT ADVISORY FROM 4 AM WEDNESDAY TO NOON CDT THURSDAY
     FOR LMZ643>646.

&&

$$

TODAY/TONIGHT AND AVIATION/MARINE...HENTZ
WEDNESDAY THROUGH MONDAY...WOOD



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