Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KMKX 121712 AAA
AFDMKX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
1212 PM CDT SAT JUL 12 2014

.UPDATE...

IT IS LOOKING MORE AND MORE LIKE HEAVY RAIN ACROSS SOUTHERN WI IS
OUR MAIN THREAT FOR LATE THIS AFTERNOON/EVENING. SPC STILL HAS
SOUTHERN WI IN A SLIGHT RISK FOR SEVERE...BUT THAT IS MAINLY FOR
WIND.

THE EXTENSIVE CLOUD COVER THIS MORNING IS HELPING TO KEEP THE
SURFACE FRONT WELL TO OUR SOUTH. THE 850MB FRONT IS EXPECTED TO
SNEAK INTO SOUTH CENTRAL WI LATE THIS AFTERNOON WITH A QUICK
STRENGTHENING OF THE LOW LEVEL JET /LLJ/ AND THEN DROP SOUTHEAST
INTO NORTHERN IL THIS EVENING AS THE LLJ VEERS. FORECAST SOUNDINGS
SHOW LIMITED INSTABILITY OVER SOUTHERN WI DUE TO THE MOIST
ATMOSPHERE AND WEAK MID LEVEL LAPSE RATES...THUS SEVERE HAIL IS NO
LONGER LIKELY. THE ONLY THING LEFT FOR SEVERE POTENTIAL IS STORM
ORGANIZATION DUE TO INCREASING BULK SHEAR AND STEEP LOW LEVEL LAPSE
RATES TO ALLOW FOR STRONG THUNDERSTORM WIND GUSTS.

THERE WILL LIKELY BE A 3 TO 4 HOUR PERIOD OF MODERATE RAIN WITH
EMBEDDED AREAS OF HEAVY RAIN/THUNDERSTORMS MOVING WEST TO EAST
THROUGH SOUTHERN WI BETWEEN 5 PM AND 11 PM. THE AREA WITH GREATEST
THREAT FOR HEAVY RAIN WILL BE THE I-94 CORRIDOR AND SOUTH. INCLUDING
DELLS...MADISON AND MILWAUKEE AREAS AND SOUTH. TWO TO THREE INCHES
COULD FALL WITHIN A SHORT AMOUNT OF TIME. URBAN AREAS AND
CONSTRUCTION AREAS WILL BE SUSCEPTIBLE TO FLOODING.

WE ARE WEIGHING THE SHORT TERM PRECIP FORECAST HEAVILY ON THE HRRR
GIVEN ITS GOOD PERFORMANCE SO FAR THIS MORNING. THE HRRR AND NEW 12Z
WRF MODELS HAVE A SLIGHTLY LATER TIMING OF THE MAIN BATCH OF
THUNDERSTORMS ARRIVING IN SOUTHERN WI THAN THE RAP. THE 12Z NAM DID
NOT CAPTURE THE MORNING PRECIP VERY WELL AND SEEMS LIKE A SOUTHERN
OUTLIER AND LIGHT ON THE QPF ACROSS SOUTHERN WI...SO WILL LEAN AWAY
FROM THIS MODEL GUIDANCE TODAY. THE GFS AND CANADIAN MODELS BOTH
BULLSEYE THE PRECIP MAX OVER SOUTHERN WI EARLY THIS EVENING.

GIVEN THE SHORT NATURE OF THIS EXPECTED EVENING HEAVY RAIN EVENT...
WE ARE STILL NOT PLANNING ON ISSUING A FLASH FLOOD WATCH. SOUTHERN
WI MISSED OUT ON THE EARLY MORNING RAIN THAT HIT THE CHICAGO AREA SO
WE ARE NOT PRE-CONDITIONED FOR FLASH FLOODING. THERE IS DEFINITELY
AN URBAN FLOODING AND PONDING CONCERN...AND WE PLAN TO HANDLE THE
RAIN WITH AN URBAN AND SMALL STREAM FLOOD ADVISORY HEADLINE AT THIS
TIME. OF COURSE...THAT IS SUBJECT TO CHANGE.

&&

.AVIATION/18Z TAFS/...

INCREASING LOW LEVEL MOISTURE IS LEADING TO PATCHY MVFR CEILINGS
OVER SOUTH CENTRAL WI EARLY THIS AFTERNOON...INCLUDING KDLL AND
KMSN. THERE WILL BE BREAKS IN THE LOW CLOUDS...BUT EXPECT THE
LOWERING TREND TO CONTINUE THROUGH THE AFTERNOON ALONG AND SOUTH OF
THE I-94 CORRIDOR. THIS WILL BE THE AREA PRIMED FOR HEAVY RAIN FROM
LATE AFTERNOON THROUGH EARLY EVENING. THERE IS LESS OF A THREAT FOR
SEVERE WEATHER...BUT WITH STRONG WINDS STILL POSSIBLE. LIKELY MVFR
CIGS AND VSBYS ASSOCIATED WITH CONVECTION AND POSSIBLY BRIEFLY
LOWER.

&&

.PREV DISCUSSION... /ISSUED 330 AM CDT SAT JUL 12 2014/

TODAY...FORECAST CONFIDENCE - LOW.

WEAK WARM AIR ADVECTION FOCUSED INTO EASTERN IOWA AND NORTHERN
ILLINOIS THIS MRNG MAY CAUSE A FEW SHOWERS AND TSTORMS TO AFFECT
SOUTHERN WI...HOWEVER BETTER CHANCE FARTHER SOUTH.  SEEING
CONSIDERABLE DIFFERENCES IN THE SHORT TERM GUIDANCE WITH REGARDS TO
APPROACHING SHORT WAVE AND FORCING.  HENCE FORCED TO LOWER
CONFIDENCE TO LOW FOR TODAY.  LEANING TOWARD MORE CONSISTENT ECMWF
IN THE SHORT TERM AS CANADIAN HAVING ISSUES WITH QPF VERIFICATION
OVERNIGHT.  DO NOT CARE FOR NAM HANDLING OF UPSTREAM VIGOROUS SHORT
WAVE SO WL USE MORE OF A BLEND OF GFS AND ECMWF.

BOUNDARY LAYER MIXING AND DEEPENING LOW LEVEL MOISTURE HAVE BEEN
PRODUCING SCT-BKN STRATUS OVERNIGHT ACROSS SRN WI...HOWEVER INCREASE
IN STRATUS NOTED ON 11-3.9 MICRON IMAGERY OVER WESTERN HALF OF CWA
SINCE 05Z.  INCREASE IN CLOUDS MAY ALSO BE AIDED BY WEAK LOW LEVEL
WARM AIR ADVECTION AS WELL.  HENCE EXPECT CONSIDERABLE CLOUDS FOR A
TIME THIS MRNG.  LOW CLOUDS WL LIKELY THIN LATER THIS MRNG AND
AFTN...BUT BY THEN MORE MID-HIGH LEVEL CLOUDS EXPECTED FROM
DEVELOPING UPSTREAM CONVECTION.

HERE ARE THE FACTORS WE ARE MORE CONFIDENT ON...PWAT VALUES LIKELY
TO INCREASE TO 1.5 TO 2 INCHES BY MID-LATE AFTN AS UPSTREAM DEWPTS
IN THE UPPER 60S TO AROUND 70 OVER SRN WI. THIS WILL REACH THE 75TH
PERCENTILE AT GRB WITH DVN HISTORICAL PWAT VALUES NEARING TWO
STANDARD DEVIATIONS FROM NORMAL.  HENCE MOISTURE EXPECTED TO BE IN
PLACE.  OTHER FACTOR IS THAT ALL SHORT TERM GUIDANCE IN REASONABLE
AGREEMENT ON RIGHT ENTRANCE REGION OF UPPER JET TO AFFECT SRN WI
FROM MID-AFTN INTO THE EARLY EVE.  DURING THIS TIME...VIGOROUS MID-
LEVEL SHORT WAVE OVER SD/NE BORDER SHOULD BE PASSING ACROSS SRN WI
REGION.  HENCE ENUF CONFIDENCE IN THESE FEATURES TO CONTINUE HIGH
MID-RANGE TO CATEGORICAL POPS LATE AFTN INTO THE EVE.  THINKING BEST
THREAT WILL BE ACROSS SRN HALF OF CWA. CONSIDERED FLASH FLOOD WATCH
AS THETA-E RIDGE SPREADS ACROSS SRN CWA AROUND 00Z AND 925-850MB
MOISTURE CONVERGENCE WILL BE ALIGNED WITH 850-300MB FLOW FOR A
PERIOD.  HOWEVER THESE FACTORS ONLY AFFECTING SRN WI FOR A 3-6 HOUR
PERIOD.  IN ADDITION...3 HOUR FLASH FLOOD GUIDANCE ABOVE 2 INCHES
MOST AREAS AND CORFIDI VECTORS REMAIN PROGRESSIVE AND MOSTLY ABOVE
15KTS.  HENCE HELD OFF ON WATCH AND WL MENTION IN HWO POTENTIAL FOR
HEAVY RAIN. WL NEED TO WATCH POTENTIAL TRAINING AFFECTING URBAN
AREAS.

TONIGHT...FORECAST CONFIDENCE - MEDIUM.

EXPECT NUMEROUS TO CATEGORICAL CONVECTION TO AFFECT SRN WI DURING
THE EVENING AS INCREASING LOW LEVEL JET BRUSHES THE AREA.  BULK
SHEAR INCREASES DURING THE DAY TO 35 TO 45 KNOTS. UNSURE HOW MUCH
INSTABILITY WILL BE AVAILABLE DUE TO EXPECTED CLOUD COVER BUT CAPE
SHOULD STILL BE ABLE TO REACH 1000-2000 J.  ABOUT HALF OF THE
MESOSCALE MODELS USED IN THE SPC SSEO PAINT OUT AREAS OF STRONG
UPDRAFT HELICITY AND UPDRAFT SPEED DURING THE LATE AFTN WHILE 10M
WIND SPEED NOT AS IMPRESSIVE. LOW LEVEL SHEAR APPEARS WEAK SO FOCUS
WOULD BE ON HAIL AND WINDS FROM LATE AFTN INTO THE EVENING...ALONG
WITH HEAVY RAINFALL.  AS MENTIONED EARLIER...CLOUD COVER WILL BE
BIGGEST FACTOR TO SEVERE POTENTIAL.

LOW LEVEL JET PIVOTS EAST OF THE AREA LATER IN THE EVENING AS UPPER
LEVEL SHORT WAVE TRACKS OFF TO THE EAST.  HENCE EXPECT CONVECTION TO
DIMINISH DURING THE EVENING IN THE WEST TO THE EAST AROUND MIDNIGHT.
WILL KEEP LINGERING SMALL POPS IN FOR AFTN MIDNIGHT IN THE EAST.

SUNDAY - CONFIDENCE...MEDIUM
WITH THE FRONT TO THE SOUTHEAST NW WINDS WILL USHER IN COOLER 850
TEMPS. THE NAM AND ECMWF ARE SHOWING A DRY SOLUTION WHILE THE GFS
HAS SHRA/ISOLD TSRA WITH A SECONDARY BOUNDARY. UPPER FLOW IS
BROADLY CYCLONIC WITH ANY VORT...MAINLY THE SHEAR/ELONGATED
VARIETY...ACROSS NORTHERN WI. WITH THE GFS BEING THE ONLY MODEL TO
GENERATE PRECIP WILL GO WI THE CONSENSUS OF MODELS AND GO WITH THE
DRY LOOK. 850 COLD ADVECTION WILL PICK UP A BIT DURING THE
AFTERNOON. HOWEVER 925 TEMPS STILL IN THE 18-20C RANGE SO HIGHS IN
THE UPPER 70S TO LOW 80S LOOK REASONABLE.

MONDAY - CONFIDENCE...MEDIUM
MORE PRONOUNCED INTRUSION OF VORTICITY AS AN UNSEASONABLY STRONG
UPPER LOW PRESSURE SYSTEM DIGS SOUTHWARD INTO THE GREAT LAKES.
DIFFERENTIAL CYCLONIC VORTICITY ADVECTION COMBINED WITH DECENT
LAPSE RATES AND SOME CAPE SHOULD RESULT IN BETTER POTENTIAL FOR
SHRA. 850 TEMPS CONTINUE TO TAKE A TUMBLE TO UNDER 10C. THE GFS
AND NAM ARE QUICKER THAN THE ECMWF ON THE COLD ADVECTION. 925
TEMPS DROP AS WELL AND SUPPORT COOL FOR JULY HIGHS IN THE MID 60S
TO LOW 70S.

TUESDAY - CONFIDENCE...MEDIUM
UPPER LOW SHIFTS EAST WITH THE GEM AND ECMWF SOLUTIONS SLOWER ON
THE PROGRESS AND THE NAM/GFS MUCH MORE PROGRESSIVE. THE ECMWF
SHOWS AN 850 TEMP JUST A SMIDGE UNDER 3C AT 12Z ACROSS SC WI. IN
EITHER CASE EXPECT A STRONGLY CYCLONIC FLOW TO KEEP SHRA CHANCES
GOING WITHIN THIS VERY COOL AIRMASS. 925 TEMPS ONLY MODIFY TO
10-13C IN THE AFTN HRS...WHICH TRANSLATES TO HIGHS FOR MOST NOT
GETTING OUT OF THE MID 60S. TAKING A COMPROMISE APPROACH WITH THE
925 TEMPS...WITH A NOD TO THE SOMEWHAT COOLER ECMWF SHOWS HIGHS
FOR MOST AREAS NOT GETTING OUT OF THE MID 60S.

WEDNESDAY - CONFIDENCE...MEDIUM
UPPER FLOW STILL SHOWING A CYCLONIC CURVATURE THOUGH SURFACE HIGH
DRAWS CLOSER AND AIRMASS DRIES OUT. MAY NEED A SMALL CHANCE OR
SPRINKLES ESP IN ERN AND NE CWA AS WE GET CLOSER BUT FOR NOW WILL
GO WITH THE DRY COLLAB WITH SURROUNDING OFFICES.

THURSDAY AND FRIDAY - CONFIDENCE...MEDIUM
FAIRLY BENIGN NW FLOW. CHILLY TEMPS SLOWLY MODIFY. NOT READY TO
BUY INTO THE LIGHT...SPOTTY AND RANDOM NATURE OF QPF BEING THROWN
AROUND BY THE MODELS WITH LOW LEVEL ANTICYCLONIC FLOW AND ANY
WAVES QUITE WEAK. SO WILL STICK WITH THE DRY POPS AT THIS POINT.

AVIATION/12Z TAFS/...STRATUS LOWERING TO MVFR WEST OF MADISON LAST
SEVERAL HOURS. EXPECT THIS TREND TO CONTINUE TO THE EAST SO FOR NOW
WL CONTINUE A PERIOD OF LOWER MVFR CIGS RISING TO VFR LATER THIS MRNG.
HIGH HUMIDITY AND DEWPTS RETURNING TODAY HELPING TO FUEL SCT TO NUMEROUS
CONVECTION FROM MID-AFTN THROUGH THE EVENING. LIKELY MVFR CIGS AND
VSBYS ASSOCD WITH CONVECTION AND POSSIBLY BRIEFLY LOWER. MOST FAVORABLE
TIMES FOR CONVECTION WL BE LISTED IN TAFS.

MARINE...PATCHY OVERNIGHT CLEARING HAS ALLOWED THE MODIS IMAGER TO
CATCH SOME SEA SURFACE TEMPERATURE MEASUREMENTS FROM THE NEARSHORE
WATERS OF LAKE MI.  TEMPERATURES IN THE 50S...WITH THE COOLEST
READINGS NORTH OF NORTH POINT LIGHT TO SHEBOYGAN.  WITH SFC
DEWPOINTS EXPECTED TO APPROACH 70 LATER TODAY AND TONIGHT...WOULD
EXPECT AT LEAST PATCHY FOG OVER THE NEARSHORE WATERS TO DEVELOP.
WILL HOLD OFF ON GOING MORE WIDESPREAD OR DENSE ATTM DUE TO SHOWERS
AND TSTORMS EXPECTED TO AFFECT THE NEAR SHORE WATERS TONIGHT.  WILL
MENTION THREAT IN HAZARDOUS WX OUTLOOK.

&&

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

$$

UPDATE...MRC
TODAY/TONIGHT AND AVIATION/MARINE...MBK
SUNDAY THROUGH FRIDAY...COLLAR


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.