Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 280204 AAA
AFDMKX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
904 PM CDT WED APR 27 2016

.UPDATE...

DIMINISHING BAND OF STEADY LIGHT SHOWERS ALONG STRIP OF FRONTOGENETIC
RESPONSE TO 850 MB WARM ADVECTION...WITH LIFT AIDED BY 700-400 MB
DIFFERENTIAL VORTICITY ADVECTION...WEAKENING AS OCCLUSION IS
PINCHING OFF MOISTURE TRANSPORT INTO THE BAND. CUT BACK ON POPS AS
HI-RES MODELS SHOW ONLY ISOLATED SHOWERS/SPRINKLES BEHIND THIS
BAND UNTIL AFTER MIDNIGHT WHEN SCATTERED TO NUMEROUS SHOWERS MOVE
IN WITH FORCING ASSOCIATED WITH APPROACHING WAVE AND SURFACE WARM
FRONT INCHING SLOWLY TOWARD NORTHERN ILLINOIS AHEAD OF THE SURFACE
LOW. COVERAGE AND AMOUNTS OF RAIN WILL BE DEPENDENT ON MOISTURE
RETURN. HI-RES MODELS INDICATE HEAVIER RAIN POTENTIAL WILL BE
SOUTH AND SOUTHEAST OF CWA. WILL LEAVE LIKELY POPS IN THE
SOUTHEAST OVERNIGHT TO ACCOUNT FOR THE HEAVIER POCKETS OF RAIN
BRUSHING THE SE CWA SHOWN ON NAMNEST AND HRRR.

&&

.AVIATION/06Z TAFS/...

BAND OF LIGHT SHOWERS WITH SPOTTY MVFR VSBYS WILL CONTINUE TO
DIMINISH AS IT LIFTS NORTHEAST AND SHOULD EXIT THE FAR SOUTHEAST
BETWEEN 945 PM AND 10 PM...AND THE FAR NORTHEAST CORNER OF
SHEBOYGAN COUNTY AROUND 1130 PM. VFR CONDITIONS WITH PATCHY
DRIZZLE OR ISOLATED SHOWERS EXPECTED UNTIL AFTER MIDNIGHT. MVFR
CIGS AND SCATTERED SHOWERS SLOWLY MOVE IN FROM SOUTHWEST TO
NORTHEAST WITH APPROACHING WARM FRONT AND FORCING WITH MID LEVEL
WAVE...WITH THE SREF CIG PROBABILITY FORECAST KEEPING LOCATIONS
ALONG THE I-94 CORRIDOR AND SOUTH IN THE HIGHER PROBABILITIES FOR
CIGS BELOW 3K FT INCLUDING ALL THE TAF SITES.

WINDS ALOFT APPROACH LOW-LEVEL WIND SHEAR CRITERIA BUT EXPECT
SURFACE GRADIENT WINDS AND WIND GUSTS TO REMAIN STRONG ENOUGH TO
KEEP THE DIFFERENTIAL BELOW CRITERIA. AREAS AROUND KMSN HAVE THE
HIGHER POTENTIAL FOR WIND SHEAR OVER THE NEXT FEW HOURS.

&&

.MARINE...

NO CHANGE TO ONGOING SMALL CRAFT ADVISORY HEADLINES. STRONG NORTHEAST
WINDS ASSURES HIGH WAVE HEIGHTS THROUGH THURSDAY MORNING...AND
INTO THE EARLY AFTERNOON AFTER WINDS LOWER.

&&

.PREV DISCUSSION... /ISSUED 331 PM CDT WED APR 27 2016/

TONIGHT AND THURSDAY...FORECAST CONFIDENCE IS MEDIUM.

BAND OF RAIN SHOWERS CONTINUES TO MOVE NORTHWARD INTO THE AREA. THIS
IS ASSOCIATED WITH FOCUSED 850 MB WARM AIR ADVECTION AND
FRONTOGENESIS RESPONSE. GUSTY EAST NORTHEAST WINDS WITH DRY LOW
LEVEL AIR ACROSS THE AREA ARE NOT DOING MUCH TO INHIBIT THE ADVANCE
OF THE RAIN SHOWERS. MESOSCALE MODELS ARE SHOWING THE AREA OF RAIN
SHOWERS MOVING FURTHER NORTH INTO THE AREA AND WEAKENING OR
DISSIPATING BY EARLY THIS EVENING. THIS IS LIKELY IN RESPONSE TO THE
DRY LOW LEVEL FEED OF AIR HELPING BREAK UP THE RAIN SHOWERS.

SOME UNCERTAINTY WITH THIS ACTIVITY BREAKING UP...AS THE ADVANCE OF
THESE SHOWERS HAS BEEN FAIRLY ROBUST. WILL TREND HIGH POPS TO
SCATTERED/NUMEROUS INTO THE EARLY EVENING FOR NOW. IT IS POSSIBLE
THE REST OF THE AREA WILL SEE THESE SHOWERS BEFORE THEY BREAK UP OR
MOVE THROUGH.

THE MESOSCALE AND SYNOPTIC MODELS ARE THEN IN DISAGREEMENT WITH
TRENDS FOR LATER TONIGHT INTO THURSDAY. THE SYNOPTIC MODELS SHOW A
FAIR AMOUNT OF QPF ACROSS THE AREA DURING THIS PERIOD...WITH THE
MESOSCALE MODELS SHOWING A DECENT LULL IN THE PRECIPITATION UNTIL
LATER TONIGHT OR THURSDAY MORNING. LOOKING UPSTREAM...IT SEEMS THAT
THERE COULD BE A LULL IN THE PRECIPITATION LATER THIS EVENING INTO
THURSDAY MORNING...UNTIL THE 500 MB LOW MOVES EAST ACROSS NORTHERN
ILLINOIS AND BRINGS IN MORE SHOWERS. MORE UNCERTAINTY EXISTS HERE AS
WELL.

WILL CONTINUE TO HAVE SCATTERED TO NUMEROUS POPS GOING FOR TONIGHT
INTO THURSDAY...WITH A LULL IN THE SHOWER ACTIVITY POSSIBLE FOR A
TIME LATER THIS EVENING INTO THURSDAY MORNING.

BRISK EAST NORTHEAST WINDS WILL LINGER TONIGHT INTO THURSDAY
MORNING...THEN WEAKEN SOMEWHAT IN THE AFTERNOON. CLOUDY SKIES AND
THE SHOWER ACTIVITY SHOULD KEEP LOWS IN THE UPPER 30S TONIGHT...WITH
HIGHS IN THE 40S ACROSS THE AREA THURSDAY.

FRIDAY - CONFIDENCE...MEDIUM
PRIMARY 500 MILLIBAR SHORTWAVE WILL TREK INTO THE OH VLY AND
LEAVE BEHIND A SHEAR AXIS THAT WILL EXTEND ACROSS NRN WI. 500
MILLIBAR RIDGING BUMPS UP ACRS SRN WI. IN THE LOWER LEVELS THE
COOL NE REGIME PREVAILS BETWEEN CANADIAN HIGH PRESSURE AND NEXT
WX MAKER IN THE SRN PLAINS. THE NAM AND ECWMF LLVL RH PROGS KEEP
CLOUDS ACROSS THE AREA AS DOES THE NAM MOS. MEANWHILE THE GFS MOS
SHOWS MORE OF A CLOUD/SUN MIX.

SATURDAY THROUGH SUNDAY NIGHT - CONFIDENCE...LOW TO MEDIUM
MID LEVEL RIDGE AXIS SHIFTS EAST OF WI WITH ENERGY FROM NEXT 500
MILLIBAR LOW APPROACHING. A LEAD SHORTWAVE WILL INTERACT WITH AT
LEAST SOME MOISTURE ADVECTION TO GENERATE INCREASING RAIN CHANCES.
THERE ARE DIFFERENCES THOUGH WITH HOW FAR NORTH THE RAIN WILL
ADVANCE INTO THE DRIER EASTERLY FLOW THAT WILL BE SET UP AHEAD OF
THIS SYSTEM. THE 12Z NAM AND 12Z ECMWF ARE SHOWING A QUARTER INCH
PLUS MOVING ACROSS ALL OF SRN WI WHILE THE 12Z GFS KEEPS THE RAIN
ACRS NW IL INTO IA. WILL GO THE MIDDLE GROUND FOR NOW TRYING TO HIT
POPS HARDER IN THE SOUTH/SOUTHWEST CWA WITH LOWEST POPS IN THE
NORTHEAST. A COOL PATTERN WILL PERSIST WITH THE NORTHEAST WINDS
HANGING TOUGH WITH YET ANOTHER LOW PASSING TO OUR SOUTH. THE 500
MILLIBAR IS PROGGD TO SHIFT TO OUR SOUTH AS WELL AND THE 12Z ECMWF
BRINGS MORE DEF ZONE PRECIP ACROSS SUNDAY INTO SUNDAY EVENING SO
HAVE LEFT THE SUPERBLEND POPS IN PLACE TO ACCOUNT FOR THIS. AGAIN
THE GFS IS SHOWING A RATHER DRY LOOK WITH THIS SYSTEM WITH MUCH OF
THE QPF PASSING BY TO OUR SOUTH.

MONDAY AND MONDAY NIGHT - CONFIDENCE...MEDIUM
DECENT CONSENSUS FOR A DRY PERIOD HOWEVER THE ECMWF AND GEM SHOW A
500 MILLIBAR VORT MAX RIDING SOUTHEAST FROM CANADA INTO NRN WI/UP
REGION BY END OF PERIOD. THE GFS SHOWS MUCH MORE RIDGING. WITH MORE
LOW LEVEL RIDGING COMING INTO PLAY THE STEADY ONSHORE COMPONENT
SHOULD EASE WITH 925 TEMPS MODIFYING AS WELL.

TUESDAY AND WEDNESDAY - CONFIDENCE...LOW
THE ECMWF AND TRENDS IN THE GEM SUGGEST A POTENT 500 MILLIBAR VORT
MAX WILL BE DROPPING INTO THE AREA FROM NORTHERN WI. THIS HAS AN
ACCOMPANYING SURFACE LOW/COLD FRONT AND A FAIR AMOUNT OF QPF WITH
IT AND A PRONOUNCED LOW LEVEL THERMAL TROUGH INTO WEDNESDAY WITH 500
CYCLONIC FLOW. MEANWHILE THE GFS KEEPS THE DRY LOOK FOR THE MOST
PART...BUT DOES GENERATE A SMIDGE OF PRECIP ACRS SW WI FROM A WAVE
THAT MOVES EAST FROM THE CNTRL PLAINS. WILL BE USING SUPERBLEND
GUIDANCE TO HANDLE THE LACK OF AGREEMENT IN THE MODELS.

AVIATION/12Z TAFS/...GUSTY EAST NORTHEAST WINDS ARE EXPECTED AT TAF
SITES TONIGHT INTO THURSDAY...AS LOW PRESSURE PASSES SOUTH OF THE AREA.
THERE WILL BE EAST NORTHEAST WINDS IN THE 30 TO 35 KNOT RANGE AT 2000
FEET ABOVE GROUND LEVEL AT ALL SITES TONIGHT. NOT STRONG ENOUGH TO
MENTION LOW LEVEL WIND SHEAR AT THIS TIME.

AREA OF RAIN SHOWERS WILL CONTINUE TO AFFECT MADISON AND SHOULD AFFECT
THE EASTERN SITES INTO EARLY THIS EVENING. CEILINGS AND VISIBILITIES
WILL REMAIN VFR CATEGORY.

THERE IS UNCERTAINTY WITH HOW WIDESPREAD ANY ADDITIONAL SHOWERS WILL
BE LATER THIS EVENING INTO THURSDAY...AS LOW PRESSURE PASSES BY TO
THE SOUTH. WILL MENTION AT LEAST VICINITY SHOWERS TONIGHT INTO THURSDAY
AT TAF SITES...WITH SOME PREVAILING PERIODS.

CEILINGS SHOULD REMAIN VFR CATEGORY UNTIL LATER THURSDAY MORNING...
FALLING BELOW 2000 FEET ABOVE GROUND LEVEL SOON AFTER AND LINGERING
INTO THE AFTERNOON. VISIBILITIES MAY DROP TO 3 TO 5 MILES IN THE
SHOWERS THURSDAY AFTERNOON.

MARINE...SMALL CRAFT ADVISORY IS IN EFFECT INTO MID AFTERNOON THURSDAY.
PERSISTENT EAST NORTHEAST WINDS AND HIGH WAVES ARE EXPECTED INTO THURSDAY
..AS LOW PRESSURE MOVES SOUTH OF THE AREA. GUSTS TO 25 KNOTS ARE
EXPECTED TONIGHT INTO EARLY THURSDAY...BEFORE SLOWLY WEAKENING. WAVES
OF 4 TO 6 FEET ARE EXPECTED TONIGHT INTO EARLY THURSDAY...BEFORE SUBSIDING
IN THE AFTERNOON.

&&

.MKX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 3 PM CDT THURSDAY FOR LMZ643>646.

&&

$$

UPDATE...REM
TONIGHT/THURSDAY AND AVIATION/MARINE...WOOD
THURSDAY NIGHT THROUGH WEDNESDAY...COLLAR



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