Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 251058 AAA
AFDMKX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
558 AM CDT FRI JUL 25 2014

.UPDATE...

CHANGED WORDING IN FORECAST TO ISOLATED/SCATTERED AS OBS UNDER UPSTREAM
RETURNS APPROACHING PORTIONS OF EAST CENTRAL WI ARE REPORTING
SPRINKLES/LIGHT RAIN SHOWERS WITH TRACE AMOUNTS. A FEW GROUND
STROKES WEST OF MADISON SO ISOLATED/SCT THUNDERSTORMS THERE.

ALSO EXPANDED POPS FOR LATER THIS MORNING AS LINE OF CONVECTION
MOVING INTO WEST CENTRAL WI TRACKING MORE WITH THE 850-300 MB MEAN
WIND ALMOST DUE EAST VERSUS THE ANTICIPATED SOUTH-SOUTHEAST PER
CORFIDI VECTORS.

&&

.PREV DISCUSSION... /ISSUED 345 AM CDT FRI JUL 25 2014/

TODAY AND TONIGHT...FORECAST CONFIDENCE IS MEDIUM.

POCKETS OF CONVECTION EXTENDING FROM NORTHEAST SOUTH DAKOTA AND
SW MN INTO ERN NEBRASKA DEVELOPING ALONG LEADING EDGE OF SFC TO
850 MB MOISTURE PLUME IN REGION OF DEEP MOISTURE CONVERGENCE AND
THETA-E ADVECTION AHEAD OF 850 MB LOW/SFC LOW WITH MOST UNSTABLE
CAPE OF 1000 J/KG OR HIGHER.

THESE POCKETS OF CONVECTION ARE SETTING UP TO THE SW AND WEST OF
STRONG 850 MB FRONTOGENETIC RESPONSE TO THE LOW LEVEL JET
IMPINGING ON 850 MB BAROCLINIC ZONE STRETCHING ACROSS W CENTRAL TO
SOUTH CENTRAL MN INTO NE IOWA.

HI RES/RAPID UPDATE MODELS CATCHING ON TO LACK OF MOISTURE AND
INSTABILITY OVER WI AND KEEPING PCPN OUT OF CWA UNTIL AFTER
12Z...WITH A FEW ACCAS SPRINKLES POSSIBLE BEFORE THEN.

MODELS AGREE THAT AREAL COVERAGE AND AMOUNT OF PRECIPITATION WILL
DIMINISH AS WEAKENING FORCING AND OMEGA PUSHES ACROSS STATE WITH
DIURNALLY WEAKENING LLJ THIS MORNING/EARLY AFTERNOON. WILL KEEP
POPS IN CHANCE/SCATTERED CATEGORY AND MAINLY SHOWERS WITH ONLY A
SLGT CHANCE OF THUNDER DUE TO CAPPING AND MARGINAL MID LEVEL
LAPSE RATES.

LOOKING FOR A BREAK IN THE PCPN MID AFTERNOON...THEN REDEVELOPING
AS LOW LEVEL JET BEGINS TO STRENGTHEN LATE THIS AFTERNOON AND
EVENING. CAP AT 700 MB ERODES EARLY TO MID EVENING...BUT STILL
SOME QUESTION TO AMOUNT OF SURFACE BASED CAPE. HOWEVER DECENT
ELEVATED CAPE FOR THUNDERSTORMS. 0 TO 6KM SHEAR SUFFICIENT FOR
SUSTAINED UPDRAFTS...AND WITH STEEPENING MID-LEVEL LAPSE
RATES...SOME HAIL NOT OUT OF THE QUESTION THOUGH PROBABILITY FOR
SEVERE HAIL IS LOW. PW/S REACH NEAR 2 INCHES BY 06Z SO HEAVY
DOWNPOURS POSSIBLE... ESPECIALLY IN THE FAR SOUTH AND SOUTHEAST.

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

MODELS SHOWING QPF ASSOCIATED WITH MAIN PUSH OF WARM AIR ADVECTION
MOVING OFF TO THE EAST ON SATURDAY. AREA FORECAST SOUNDINGS
SHOWING CAPPED AIRMASS OVER SOUTHERN WISCONSIN...WITH NOT MUCH
FORCING FOR UPWARD VERTICAL MOTION SEEN. THUS...KEPT SATURDAY DRY
ACROSS THE AREA. WARM AND HUMID CONDITIONS WILL PREVAIL...WITH
HIGHS REACHING THE MID 80S IN MOST AREAS PER 925 MB TEMPERATURE
FIELDS.

KEPT LOW POPS IN THE WESTERN COUNTIES SATURDAY NIGHT...WITH
APPROACH OF 500 MB SHORTWAVE TROUGH. HOWEVER...THIS WILL STILL
HAVE TO CONTEND WITH FAIRLY STRONG CAP OVER THE AREA. SO...MOST OF
THE NIGHT MAY REMAIN DRY IN THIS AREA.

MODELS THEN BRING COLD FRONT SOUTHEASTWARD THROUGH THE AREA SUNDAY
MORNING INTO EARLY AFTERNOON...WITH TRAILING 500 MB SHORTWAVE
TROUGH MOVING THROUGH DURING THE AFTERNOON AND EARLY EVENING. AREA
FORECAST SOUNDINGS DO MIX OUT CAP DURING THE DAY...THOUGH IT MAY
BE AFTER THE FRONTAL PASSAGE IN NORTHERN PORTIONS OF THE AREA.

KEPT LIKELY POPS FOR THUNDERSTORMS MOST OF SUNDAY...THOUGH BEST
CHANCES WILL BE IN THE MORNING BEFORE FRONTAL PASSAGE. SOME
QUESTION AS TO HOW MUCH MEAN LAYER CAPE WILL EXIST BEFORE FRONT
MOVES THROUGH. THIS WILL DETERMINE IF THERE WILL BE A HAIL
RISK...GIVEN THE STRONG DEEP LAYER SHEAR.

COLD AIR ADVECTION SUNDAY NIGHT SHOULD BRING IN COOLER AND LESS
HUMID AIR...AND END THE POPS DURING THE EVENING HOURS.

LONG TERM...MONDAY THROUGH THURSDAY...FORECAST CONFIDENCE IS
MEDIUM.

GFS/ECMWF SHOWING HIGH PRESSURE SLIDE SOUTHEAST FROM THE NORTHERN
PLAINS INTO THE MIDDLE MISSISSIPPI RIVER VALLEY REGION MONDAY INTO
WEDNESDAY. 500 MB TROUGH REMAINS ANCHORED OVER THE NORTHEAST AND
MIDDLE ATLANTIC STATES...WITH NORTH NORTHWEST FLOW OVER THE
WESTERN GREAT LAKES REGION.

VARIOUS 500 MB VORTICITY MAXIMA MOVE THROUGH THE AREA DURING THIS
TIME. ENOUGH MOISTURE LINGERS TO CARRY LOWER END POPS FOR MOST OF
THIS PERIOD. CONTINUED POPS THROUGH THURSDAY USING CONSENSUS
POPS...AS OVERALL PATTERN LINGERS. TEMPERATURES SHOULD BE PLEASANT
FOR THIS TIME OF YEAR.

AVIATION/12Z TAFS/...

AGAIN WATCHING CURRENT ACCAS SHOWER/THUNDERSTORM DEVELOPMENT FOR
ADJUSTMENTS TO TIMING INTO TAF SITES. STILL LOOKS LIKE KMSN AND
POINTS WEST HAVE THE BEST CHANCE TO SEE ISOLATED TO SCATTERED THUNDERSTORMS
WITH VERY BRIEF MVFR VSBYS THIS MORNING...WITH ONLY AN ISOLATED
LIGHT VFR SHOWER/SPRINKLES AT EASTERN TAF SITES. BETTER CHANCE
FOR THUNDER COMES LATE THIS AFTERNOON/EVENING TO ALL SITES. WILL
TRY TO HONE IN ON MOST LIKELY TIMES AT EACH SITE...BUT EVEN VARIED
SHORT-TERM MODEL DIFFERENCES HANDLING CURRENT PCPN...AS WELL AS
TIMING/AMOUNTS LATER TODAY AND TONIGHT. WILL CARRY PREVAILING VFR
WITH MVFR CIGS/VSBYS WITH THUNDER.

MARINE...

SOUTH TO SOUTHWEST WINDS REMAIN LOW ENOUGH TO NOT CAUSE ANY
WIND/WAVE ISSUES INTO SUNDAY EVENING. LOOKING AT THUNDERSTORM
CHANCES INCREASING LATE THIS AFTERNOON INTO TONIGHT...AND AGAIN ON
SUNDAY.

NORTH WINDS TO INCREASE SUNDAY NIGHT INTO MONDAY BRINGING
WINDS/WAVES TOWARD SMALL CRAFT ADVISORY LEVELS...AS WELL AS A
BEACH HAZARD POTENTIAL ON MONDAY.

&&

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

$$

UPDATE...REM
TODAY/TONIGHT AND AVIATION/MARINE...REM
SATURDAY THROUGH THURSDAY...WOOD



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