Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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000
FXUS63 KMKX 210227
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
927 PM CDT WED AUG 20 2014

.UPDATE...

BASED ON 00Z NAM. SOUTHERN WISCONSIN IS IN THE RIGHT ENTRANCE
REGION OF A 70 KNOT UPPER JET. UPPER LEVEL DIVERGENCE INCREASES
MORE TOWARD SUNRISE IN AREAS SOUTH AND WEST OF MADISON THEN
ACROSS SOUTHERN WISCONSIN THURSDAY. 700 MB UPWARD MOTION IS
RATHER WEAK TONIGHT. 700 MB SPEED MAX IS SOUTH AND EAST OF THE
FORECAST AREA. THIS IS SIMILAR AT 850 MB WITH LITTLE 850 MB
MOISTURE CONVERGENCE.

AS A RESULT THE 00Z NAM HAS CONTINUED THE 18Z NAM AND HAS BACKED
OFF ON THE PRECIPITATION TONIGHT...HOLING IT OFF TIL AROUND
SUNRISE IN AREAS SOUTH AND WEST OF MADISON...THEN ACROSS THE
FORECAST AREA THURSDAY.

HAVE TRENDED THE FORECAST TO REFLECT THIS. HOWEVER DUE TO THE
UPPER DIVERGENCE SOME SCATTERED SHOWERS/THUNDERSTORMS MAY DEVELOP
FARTHER NORTH.

&&

.AVIATION/06Z TAFS/...

SOME MVFR CIGS/VSBYS WITH EAST FLOW OFF LAKE MICHIGAN. SOME IFR
CONDITIONS POSSIBLE DURING THE EARLY MORNING HOURS. ELSEWHERE THE
MID/UPPER LEVEL CLOUDS WILL TEND TO KEEP ANY FOG MAINLY IN THE
MVFR CATEGORY.

SOME SCATTERED THUNDERSTORMS LATE TONIGHT AHEAD OF AN APPROACHING
WARM FRONT. THUNDERSTORMS WILL BE LIKELY AS THE WARM FRONT MOVES
INTO SOUTHERN WISCONSIN THURSDAY. IFR CONDITIONS IN
THUNDERSTORMS.

&&

.PREV DISCUSSION... /ISSUED 251 PM CDT WED AUG 20 2014/

REST OF THIS AFTERNOON THROUGH THURSDAY - CONFIDENCE...MEDIUM
INFLUENCE OF UPPER LOW CONTINUES ACROSS SRN WI WITH BROADLY CYCLONIC
FLOW AND MAINLY SHEARED VORT. CU HAS TRIED TO BUBBLE UP A BIT WITH A
FEW HEAVIER BOTTOMS WITH SOME AGITATED CU. AN ISOLATED SHRA CANNOT
BE RULED OUT INTO INTO EARLY THIS EVENING. ATTENTION THEN TURNS TO
EVOLVING WARM/MOIST ADVECTION REGIME AND GRADUALLY INCREASING H8
LLJ. LOW LEVEL RIDGE AXIS SHIFTS EAST AFTER 6Z...SO EXPECT SHRA/TSRA
TO DEVELOP AND MOVE INTO PORTIONS OF WESTERN CWA. MAIN CONCERN FOR
OUR AREA WILL BE HEAVY RAIN POTENTIAL. MBE/CORFIDI VECTORS ALONG
WITH PRECIPITABLE WATER VALUES BECOME FAVORABLE FOR THIS. CAPE
BECOMES TALL AND SKINNY. THE GFS CONFINES THE FOCUS FOR THIS TO THE
SOUTHWEST OF THE CWA TONIGHT BUT ALL MODELS NUDGE THE AXIS OF BETTER
FRONTOGENETICAL FORCING INTO MOST OF SRN WI ON THURSDAY. THIS
WILL RESULT IN A PERIOD OF SUSTAINED FORCING. PLACEMENT OF LOW
LEVEL FRONTAL BOUNDARY WILL BE KEY FOR TEMPS AS WELL AS LOCATION
OF ANY FOG/STRATUS. BUT BANKING ON PLENTY OF FOG EVOLVING AT LEAST
ACROSS LAKE MI. THE MODELS ALL KEEP A SE FLOW IN PLACE THROUGH THE
DAY WITH THE NAM HAVING A MORE SOUTHERN PLACEMENT OF THE
FRONT...PROBABLY A MORE LIKELY SCENARIO WITH POTENTIAL FOR
SUSTAINED CONVECTION. SOME INDICATORS SHOW THAT IF FRONT CAN SNEAK
INTO SRN WI WE MAY SET UP A NICE THERMAL CONTRAST WITH SOME HEFTY
CAPE NUMBERS. SURFACE BOUNDARY WILL BE KEY TO ANY DECENT SVR
THREAT. GIVEN THE UNCERTAINTY OF FRONTAL BOUNDARY LEANED TOWARDS A
CONSENSUS APPROACH TO HIGH TEMPS WHICH FAVORS A COOLER SOLUTION
DUE TO CLOUD COVER/PRECIP/FRONTAL POSITION UNCERTAINTIES.

THURSDAY NIGHT THROUGH FRIDAY...FORECAST CONFIDENCE IS MEDIUM.

THERE IS REASONABLE MODEL AGREEMENT WITH THE TRENDS OF THE WARM
FRONT OVER TIME. TYPICALLY...THESE FRONTS DON/T MAKE MUCH PROGRESS
NORTH...ESPECIALLY IF CONVECTION FIRES ALONG IT LIKE WE EXPECT.
THE CONVECTIVE COLD POOLS OFFER RESISTANCE TO A NORTHWARD ADVANCE.
ADDITIONALLY...THE EAST TO SOUTHEAST FLOW NORTH OF THE FRONT WILL
ALLOW COOLER LAKE MICHIGAN AIR TO INFILTRATE INLAND...AGAIN
RESISTING A NORTH ADVANCE OF THE FRONT. SO...THE FRONT SHOULD BE
CENTERED OVER THE FORECAST AREA THURSDAY NIGHT WITH ONGOING
CONVECTION TRAINING ALONG IT. THEN IT SHIFTS SOUTH...POSSIBLY SOUTH
OF THE STATE LINE BY FRIDAY EVENING.

THE AIR MASS WILL BE VERY WARM AND MOIST AND THE THREAT FOR VERY
HEAVY RAIN EXISTS WITH PRECIPITABLE WATER VALUES ON BOTH THE NAM
AND GFS CLIMBING TO AN INCREDIBLE 2-2.2 INCHES...ESPECIALLY
THURSDAY NIGHT. THERE IS CONCERN ABOUT FLOODING...BUT CONFIDENCE
ISN/T HIGH ENOUGH TO HOIST ANY KIND OF WATCH AT THIS POINT. WE/LL
MONITOR FOR TRENDS.

THE HIGH DEWPOINTS AND COLD LAKE MICHIGAN AIR SHOULD RESULT IN
AREAS OF FOG...POSSIBLY DENSE...NEAR THE LAKE. FRIDAY WILL FEEL
HOT. WITH DEWPOINTS IN THE LOWER TO MID 70S...APPARENT
TEMPERATURES WILL BE IN THE 95 TO 100 DEGREE RANGE. COOLEST
READINGS WILL BE ALONG THE LAKE...HOTTER SOUTH AND WEST OF
MADISON.

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

AGAIN...THE FRONT WILL BE LINGERING IN THE AREA...LIKELY STARTING
OUT SOUTH OF WISCONSIN FRIDAY NIGHT...THEN DRIFTING NORTH BY
SUNDAY. ALOFT...THERE IS STRONG RIDGING AND THIS MAY PREVENT ANY
MEANINGFUL CONVECTION...DESPITE THE PROXIMITY OF THE FRONTAL
BOUNDARY. FOR NOW...WE/LL JUST CARRY CHCY MENTIONS OF
THUNDERSTORMS...BUT THE ECMWF IS ACTUALLY LOOKING PRETTY QUIET
THIS PERIOD AND THAT DOESN/T SEEM UNREASONABLE.

STILL VERY WARM AND HUMID...ESPECIALLY AWAY FROM THE LAKE. NEAR
THE LAKE...FOG AND COOLER TEMPS ARE EXPECTED.

MONDAY THROUGH WEDNESDAY...FORECAST CONFIDENCE IS LOW.

WE SHOULD TURN MORE UNSETTLED FOR THE FIRST HALF OF NEXT WEEK. THE
UPPER RIDGE BREAKS DOWN AND WE START TO SEE A SERIES OF MID LEVEL
SHORT WAVES TRAVERSE THE WESTERN GREAT LAKES. THE FRONT AND OUR
STEAMY AIR MASS WILL REMAIN IN THE AREA...SO WE COULD SEE MORE
SHOWERS AND STORMS FROM TIME TO TIME. THE BEST CHANCE SHOULD COME
ON WEDNESDAY WITH THE PATTERN SHIFTING COLD FRONT AND STRONG MID
LEVEL TROF DROPPING IN. WE MIGHT SEE SOME SEVERE WEATHER WITH
THAT EVENT AS THE AGGREGATE SEVERE WEATHER PARAMETER IS BEST
DURING THIS TIME.

SO...LOOK FOR UNCOMFORTABLE TEMPERATURES FOR THE NEXT WEEK WITH
COOLER...DRIER WEATHER BY THE END OF NEXT WEEK.

AVIATION/00Z TAFS/...MAIN CONCERNS WILL BE ON OVERNIGHT CONVECTIVE
TRENDS WITH POTENTIAL FOR FOG/STRATUS AHEAD OF ADVANCING WARM FRONT.
SREF CIG/VSBY PROGS SHOW WORST CONDITIONS TO THE NORTH OF TAF SITES.
LOW LEVEL RH PROGGS TEND TO SUGGEST THIS AS WELL. CONVECTION MAY
HELP DISPERSE THINGS FURTHER SOUTH IN SRN WI. INCREASING WARM AIR
ADVECTION ALONG WITH MORE FAVORABLE UPPER JET DYNAMICS WILL LIKELY
HELP TO GENERATE SHRA/TSRA LATER TONIGHT THROUGH THURSDAY MORNING.
WHERE THE BOUNDARY ENDS UP WILL DICTATE SUBSEQUENT DEVELOPMENT FOR
THE AFTERNOON. MODELS SHOWING A MIXED MESSAGE ON THIS BUT OFTEN
TIMES MODELS TRY TO PUSH FRONT TOO FAR NORTH TOO FAST SO POTENTIAL
THERE FOR PRECIP/FOG/STRATUS TO LINGER A BIT LONGER IN SOME AREAS ON
THURSDAY.

&&

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

$$

UPDATE...HENTZ
TONIGHT/THURSDAY AND AVIATION/MARINE...COLLAR
THURSDAY NIGHT THROUGH WEDNESDAY...DAVIS



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