Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 020336
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
1036 PM CDT SAT AUG 1 2015

.UPDATE...A LARGE AREA OF INCREASING WARM ADVECTION IS OCCURRING
ACROSS MN AND WI AS THE LLJ INCREASES. SOME MOISTURE TRANSPORT
WITH THAT AS WELL BUT THE ELEVATED MIXED LAYER IS VERY WARM
RESULTING HIGH VALUES OF CIN. MESOSCALE MODELS DO PRODUCE SOME
CONVECTION OVER NORTHERN AND CENTRAL WI LATE TNT INTO SUN AM. THUS LOWERED
POPS OVER SRN WI WITH BEST CHANCES TOWARD CENTRAL WI FOR THE
REMAINDER OF THE NIGHT AND INTO SUN AM.

FOR LATE SUN AFTERNOON AND EVENING LOW PRESSURE MOVES ACROSS
CENTRAL OR NORTHERN WI AND INTO NRN LOWER MI WITH A FAIRLY STRONG
COLD FRONT TO FOLLOW. THE WIND FIELD WILL INCREASE AHEAD OF THE
FRONT WITH WIND GUSTS UP TO 35 TO 40 MPH BY THE MIDDLE TO LATE
AFTERNOON. THE WELL MIXED AND VERY WARM AIRMASS WILL LIKELY DROP
THE DEWPOINTS INTO THE LOWER 60S BY LATE AFTERNOON BUT MLCAPES
MAY STILL BE 2000 J/KG. DEEP LAYER SHEAR OF 35-40 KTS AND 0-1KM
HELICITIES OVER 200 M2/S2 WILL SUPPORT A SVR TSTORM THREAT DURING
THIS TIME. AN APPROACHING UPPER TROUGH WILL RESULT IN 50 METER 500
MB HEIGHT FALLS FROM 18Z TO 06Z PROVIDING UPPER SUPPORT TO FAIRLY
STRONG LOW LEVEL FRONTOGENESIS. THUS EXPECTED STRONG TO SVR
TSTORMS FOR THIS PERIOD.

&&

.AVIATION/06Z TAFS/...ONLY SMALL CHANCES OF TSTORMS FOR THE EARLY
SUN MORNING HOURS FROM SOUTH CENTRAL WI TO SE WI AS WARM...MOIST
ADVECTION INCREASES. THE CHANCES OF STORMS WILL CONTINUE ON SUNDAY
BUT WILL BECOME MORE LIKELY FOR SE WI SUN EVE WHEN A STRONG COLD
FRONT PASSES. VFR CONDITIONS ARE EXPECTED OUTSIDE THE TSTORMS.

&&

.PREV DISCUSSION... /ISSUED 323 PM CDT SAT AUG 1 2015/

SHORT TERM...

TONIGHT - CONFIDENCE...LOW
MAIN FOCUS WILL BE PINNING DOWN CONVECTIVE TRENDS AS THE NIGHT WEARS
ALONG. 850 LLJ BECOMES MORE FAVORABLE AIMING INTO CWA WITH INCREASING
WAA AND MOISTURE ADVECTION. MODELS ARE SHOWING VARYING SOLUTIONS FOR
MCS TRACK. 1000-500 MILLIBAR THICKNESS LINES/MCS MAINTENANCE
COMPOSITE INDEX FROM SPC MESO PAGE FAVOR MORE OF A 00Z ECMWF SOLUTION.
THE 12Z NAM IS THE FURTHEST NORTH WITH PRECIP INTO CNTRL/SRN WI. THE 12Z
ECMWF HAS COME MORE IN LINE WITH OTHER MODELS SHOWING CONVECTION
ARRIVING AFTER 6Z ACROSS THE CWA. GIVEN THE PROGGD ELEVATED
CAPE/CONSENSUS OF LLJ FORCING AND MID LEVEL SHORTWAVE WILL STILL
CARRY HIGH END CHANCE POPS FOR WHOLE CWA BUT WATCHING FOR A
POTENTIAL SE CURVE TO ANY MCS THAT MIGHT TAKE SHAPE THAT COULD LEAVE
PARTS OF SRN WI MORE ON THE NORTHERN FRINGE OF A SEWD DIVING MCS TRACK
FAVORING NE IA INTO NRN IL. WATCHING AFTERNOON VSBL ANIMATION THINKING
MORE LIKELY SCENARIO IS WE WILL BE SEEING OUR ACTIVITY ORIGINATE FROM
WRN MN INTO ERN ND WHICH WOULD FAVOR SRN WI A BIT MORE. OVERALL MODEL
SOLUTIONS INCLUDING LATEST HRRR FAVOR SOME CONVECTION A BIT LATER
IN THE NIGHT ACRS SRN WI HOWEVER THERE IS SOME LOSS TO THE
ORGANIZATION AND COVERAGE IN THE LATEST HRRR RUN. AND THIS REFLECTED IN
THE LATEST SWODY1 WITH THE REMOVAL OF THE SLIGHT RISK FROM SRN WI.

SUNDAY - CONFIDENCE...MEDIUM
COULD STILL BE DEALING WITH LINGERING MORNING CONVECTION
ASSOCIATED WITH THE LLJ/500 MILLIBAR SHORTWAVE. THEN WILL HAVE TO
SEE HOW THE MESOSCALE DETAILS PLAY OUT. EVEN THE GFS SOUNDING IS
GENERATED CAPES OVER 2K SUNDAY AFTERNOON. 850 JET IS PROGGD TO
FOCUS MORE TO OUR EAST AND SOUTHEAST AS THE DAY WEARS ON. HOWEVER
SURFACE/850 FRONT WILL STILL BE HANGING BACK TO THE NORTH AND A
WSW LOW LEVEL FLOW WILL REINFORCE MOISTURE INSTABILITY AS THE DAY
WEARS ON. CWASP SHOWING SOLID MID 70S PLUS ON ALL PROGS WITH THE
GFS SHOWING 80 PLUS BY 00Z. SO GIVEN PRONOUNCED LOW LEVEL FORCING
APPROACHING WITH SURFACE/850 FRONT SWODY2 SLIGHT IS WARRANTED WITH
THE GREATEST THREAT LATER IN THE AFTERNOON.

SUNDAY NIGHT... FORECAST CONFIDENCE MEDIUM.

SYNOPTIC AND MESOSCALE MODELS ARE IN FAIR AGREEMENT WITH
THUNDERSTORMS DEVELOPING ALONG THE COLD FRONT AS IT TRACKS FROM
CENTRAL WI DOWN THROUGH SOUTHEAST WI AND NORTHERN IL LATE SUNDAY
AFTERNOON THROUGH SUNDAY EVENING. I WENT WITH LIKELY POPS IN
SOUTHEAST WI SUNDAY EVENING... BUT IT MAY JUST BE A BROKEN LINE.
SHOWERS AND STORMS SHOULD WIND DOWN QUICKLY AFTER MIDNIGHT AS DRY
AIR SETTLES IN BEHIND THE FRONT.

EXPECTING HIGH CAPE AND SHEAR JUST AHEAD OF THE FRONT... ENOUGH TO
PRODUCE LARGE HAIL AND DAMAGING WINDS WITH ANY STRONG THUNDERSTORMS.
A TORNADO IS A REMOTE POSSIBILITY GIVEN THE LIMITED LOW LEVEL SHEAR.

LONG TERM...

MONDAY THROUGH WEDNESDAY... FORECAST CONFIDENCE HIGH.

NORTHWEST FLOW WILL DOMINATE THE GREAT LAKES REGION FOR THE FIRST
PART OF THE WORK WEEK AS AN UPPER LOW REMAINS STATIONED OVER QUEBEC.
HIGH PRESSURE AT THE SURFACE WILL ALLOW FOR FAIRLY LIGHT WINDS.
TEMPS WILL BE AROUND SEASONAL NORMAL MONDAY AND TUESDAY... THEN
SLIGHTLY COOLER IN THE MID 70S WEDNESDAY DUE TO NORTHEAST BREEZE OFF
THE LAKE.

THURSDAY THROUGH SUNDAY... FORECAST CONFIDENCE MEDIUM.

MODELS TRY TO GENERATE AN MCS OVER THE NORTHERN PLAINS THAT TRACKS
SOUTHEAST THROUGH THE MIDWEST THURSDAY AND POSSIBLY ANOTHER ONE INTO
FRIDAY. THE GFS IS MAINTAINING PRECIP CHANCES IN SOUTHERN WI WITH
THIS SYSTEM AND APPEARS TO HAVE SOME CONVECTIVE FEEDBACK ISSUES...
WHILE THE 12Z ECMWF SHIFTED THE MAIN CHANCES FARTHER SOUTH.

EXPECT DRY HIGH PRESSURE TO SETTLE BACK INTO THE GREAT LAKES REGION
BY FRIDAY NIGHT AND KEEP PRECIP CHANCES MINIMAL THROUGH THE WEEKEND.
TEMPERATURES SHOULD BE IN THE 70S.

AVIATION/00Z TAFS/...VFR CONDITIONS AT LEAST INTO THIS EVENING.
MAIN FOCUS FOR CONVECTIVE DEVELOPMENT ARRIVES LATER TONIGHT INTO
SUNDAY MORNING AS MORE PRONOUNCED LLJ AIMS INTO SRN WI. STILL SOME
TRACK UNCERTAINTY ON MCS BUT OVERALL MOIST ADVECTION WITH 850 LLJ
AND SHORTWAVE ACTIVITY WARRANTS THE CHANCE OF STORMS LATER TONIGHT
INTO SUNDAY MORNING. POCKETS OF MVFR CIGS/VSBYS WITH ANY STRONGER
STORMS. MESOSCALE DETAILS AFTER OVERNIGHT/EARLY MORNING STORMS WILL
DICTATE STORM EVOLUTION/SEVERITY ON SUNDAY AFTERNOON/EVENING AS
SURFACE LOW AND COLD FRONT INTERACT WITH POTENTIALLY VERY UNSTABLE
AIRMASS. IN ADDITION WITH LOW LEVEL JET STRENGTHENING OVERNIGHT SOME
LOW LEVEL WIND SHEAR IS POSSIBLE.

MARINE...SMALL CRAFT ADVISORY HOISTED FOR SUNDAY AS PRESSURE
GRADIENT TIGHTENS UP AHEAD OF APPROACHING SURFACE LOW PRESSURE
SYSTEM. SW WINDS SHOULD RAMP UP PRETTY QUICK IN THE MORNING AND GET
RATHER GUSTY. COLD FRONT MAY SPAWN SOME STRONG TSTORMS LATE
AFTN/ERLY EVE.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...SMALL CRAFT ADVISORY FROM 9 AM TO 6 PM CDT SUNDAY FOR LMZ643>646.

&&

$$

UPDATE...GEHRING
TONIGHT/SUNDAY AND AVIATION/MARINE...COLLAR
SUNDAY NIGHT THROUGH SATURDAY...MRC



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