Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 191646 AAA
AFDMKX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
1146 AM CDT SUN APR 19 2015

.UPDATE...

WE CUT BACK ON POPS FOR THIS AFTERNOON A LITTLE MORE. THE SHORTWAVE
AND ASSOCIATED SURFACE LOW TRACKING NORTH FROM THE MIDWEST WILL GET
TO SOUTHERN LAKE MICHIGAN AROUND 7 PM THIS EVENING. THE RAIN WITH
THIS SYSTEM IS ON TRACK TO ARRIVE AT THE WI/IL BORDER RIGHT AROUND
THAT TIME.

LIGHT RETURNS ON RADAR FROM THE LIGHT RAIN SHOWERS ALONG THE SURFACE
TROUGH OVER WESTERN WI ARE TRACKING DUE NORTH AND ARE EXPECTED TO
REMAIN OUT OF THE MKX FORECAST AREA UNTIL AT LEAST LATE AFTERNOON.
MODELS CONTINUE TO DELAY ITS ARRIVAL.

TEMPS ARE ON TRACK TO REACH 70 FROM MADISON AND SOUTHWEST TODAY.

&&

.AVIATION/18Z TAFS/...

RAIN EXPECTED TO AFFECT MUCH OF THE AREA TONIGHT...SO WL CONTINUE
TREND TOWARD IFR CIGS THIS EVENING. INITIALLY DRIER AIR WL SLOW DOWN
LOWER CIGS AND VSBYS FROM AFFECT KMSN UNTIL TNGT.

THE HEAVIEST RAIN WILL OCCUR IN SOUTHEAST WI THIS EVENING. EXPECT
IFR AND LOWER CIGS WITH THE RAIN AND FOG DEVELOPING AFTER MIDNIGHT
AS THE RAIN TAPERS OFF.

&&

.PREV DISCUSSION... /ISSUED 341 AM CDT SUN APR 19 2015/

TODAY AND TONIGHT...FORECAST CONFIDENCE - MEDIUM.

INITIAL SURGE OF MOISTURE AND WARM AIR ADVECTION OCCURRING THIS
MORNING SETTING OFF A FEW HIGH BASED -SHRA AROUND THE AREA MOSTLY TO
THE WEST AND NORTHWEST IN VICINITY OF LOW LEVEL JET AXIS.  POSSIBLE
A BRIEF -SHRA COULD DEVELOP AND AFFECT A PART OF THE CWA NEXT
SEVERAL HOURS...BUT LOW THREAT SHOULD END AROUND 12Z AS LOW LEVEL
WINDS BEGIN TO WEAKEN.  DESPITE COLUMN PWAT VALUES INCREASING TO
AROUND 0.75 TO 1.0...LOW LEVELS REMAIN FAIRLY DRY THIS MRNG AS
WEAK SHORT WAVE RIDGING MOVES ACROSS REGION. WILL CONTINUE TREND
OF INCREASING POPS THIS AFTERNOON AND EARLY EVENING AS STRONG
LAYER Q- VECTOR CONVERGENCE SPREADS IN FROM THE SOUTHEAST AS
UPSTREAM SRN STREAM OF APPROACHING SHORT WAVE TROF UNDERGOES
CYCLOGENESIS AS IT TRACKS NORTHEAST TOWARD THE GTLAKES. MOISTURE
WILL ALREADY BE IN PLACE WITH PWAT VALUES IN THE 75TH TO 90TH
PERCENTILE FOR APRIL. ALL SHORT TERM GUIDANCE HAS ENHANCED
SYNOPTIC SCALE FORCING ASSOCD WITH RIGHT ENTRANCE REGION CLIPPING
SOUTHEAST WI...BUT SOME DISCREPANCY ASSOCD WITH LINGERING DRY AIR.
HENCE WL HOLD OFF ON MORE EXPANSIVE AREA OF HIGHER POPS IN EASTERN
CWA UNTIL EARLY EVENING BUT WL HOLD ONTO CATEGORICAL POPS IN FAR
SOUTHEAST IN LATE AFTN. NOT IMPRESSED WITH ELEVATED INSTABILITY
BUT STILL SOME WEAKLY ELEVATED INSTABILITY AWAY FROM LAKE ACROSS
SOUTH AND WEST...SO WL KEEP SCHC WORDING FOR AFTN T.

BEST CHANCES FOR MORE WIDESPREAD SHRA DURING THE EVENING AS
DEFORMATION ASSOCD WITH PASSING MID-LEVEL CIRCULATION AFFECTS SRN
WI. BEST CHANCE IN THE EAST...BUT NAM AND ECMWF SHOWING MID-LEVEL
CIRCULATION FARTHER WEST.  POSSIBLE THAT MORE WIDESPREAD SHRA COULD
BE FARTHER WEST SO WL NEED TO REEVALUATE TODAY WHETHER HIGHER
CATEGORICAL POPS COULD BE SPREAD FARTHER WEST.  ALSO...SHORT WAVE
TROF LOCATED JUST TO THE WEST TODAY WILL MOVE EWD TONIGHT SO WL KEEP
LIKELY POPS GOING IN THE WEST.

MONDAY - CONFIDENCE...MEDIUM
SHRA POTENTIAL WILL BE IN PLACE DURING THE MORNING HOURS DUE TO
PROXIMITY OF 850 TROUGH AXIS AND LEAD SHORTWAVE RIDING NORTHEAST
AHEAD OF RENEWED TROUGH AXIS APPCH FROM MN. WILL HAVE HIGHEST
POPS IN THE EAST IN THE MORNING. GFS SHOWS A DRY MORNING WHILE THE
ECMWF AND NAM SHOW SOME SHRA LINGERING. SO WILL KEY ON THE LATTER
AT THIS TIME AND PER COLLAB WITH SURROUNDING OFFICES. LOW LEVEL
COLD ADVECTION STARTS TO ARRIVE WITH NEXT DCVA FROM MN UPPER
TROUGH. THE GFS AND ECMWF SHOW 850 TEMPS DROPPING BELOW 0C BY 00Z.
HOWEVER 925 TEMPS STAY ABOVE 0C ALL DAY AND SUPPORT HIGHS INTO THE
MID 50S. MID LEVEL DRY SLOT TAKES HOLD. LOW LEVEL LAPSE RATES
BECOME STEEP UP TO AROUND 775MB WITH SOME MINIMAL CAPE. 850 CAA
OFFSETTING ANY DCVA WITH MOISTURE LOOKING OVERALL MEAGER. GUSTY
WNW WINDS EXPECTED WITH THE DECENT MIXING.

MONDAY NIGHT AND TUESDAY - CONFIDENCE...MEDIUM
UPPER LOW PLODS EASTWARD TOWARDS LAKE SUPERIOR WITH CHILLY
CYCLONIC FLOW BECOMING MORE ENTRENCHED ACROSS THE UPPER MIDWEST.
COLD ADVECTION INCREASES IN THE LOWER LEVELS. 850 TEMPS DROP TO
-3C TO -5C AT TIMES DURING THIS PERIOD. EVEN 925 TEMPS SUGGEST
SOME POTENTIAL FOR MIXY PRECIP IN THE FAR NW CWA LATER IN THE
NIGHT. MODELS SHOWING EMBEDDED WAVES WITHIN THIS STRONGLY CYCLONIC
FLOW. WILL HAVE POPS ESP ON TUE WITH BETTER CONSENSUS THOUGH QPF
LOOKS LIGHT WITH THE GFS SHOWING GREATER EMPHASIS NORTH OF THE
CWA. AGAIN RATHER STEEP LAPSE RATES AND DECENT PRESSURE GRADIENT
WILL SUPPORT MORE WINDY CONDITIONS.

WEDNESDAY - CONFIDENCE...MEDIUM
UPPER TROUGH CONTINUES TO PLOD EAST OF LAKE SUPERIOR THOUGH
INFLUENCE OF THIS LOW CONTINUES BACK ACROSS WI WITH CYCLONIC FLOW
LINGERING THOUGH NOT QUITE AS PRONOUNCED. GFS SHOWS A BIT MORE
GRADIENT/WIND THAN ECMWF. WILL LEAVE DRY FORECAST INTACT FOR NOW
PER SUPERBLEND. CORE OF COLDEST 925 TEMPS ACROSS THE CWA AT THE
OUTSET...AROUND -4C. PROBABLY THE COOLEST DAY OF THE STRETCH WITH
MANY AREAS COMING UP SHORT OF 50.

THURSDAY AND FRIDAY - CONFIDENCE...MEDIUM
GEM/ECMWF SHOW NVA FINALLY BUILDING IN AS UPPER LOW LIFTS FURTHER
AWAY AND LOSES INFLUENCE ACROSS THE WRN GRT LAKES. HOWEVER LOW
LEVEL COLD POOL IS STUBBORN SO NOT LOOKING FOR A BIG REBOUND IN
TEMPS AS 925 TEMPS STAY SUBZERO THURSDAY AND THEN MODIFY A BIT
FRIDAY. THOUGH WILL HAVE TO WATCH THE ECMWF SOLUTION AS IT IS
SHOWING A MORE PRONOUNCED EASTERLY FLOW THAN THE GFS.

SATURDAY - CONFIDENCE...MEDIUM
GFS AND ECMWF BOTH SHOW SURFACE HIGH IN PLACE THOUGH THE GFS
HINTING AT A MORE VIGOROUS WAVE RIDING IN FROM THE NORTHWEST FOR
SATURDAY NIGHT. WILL STICK WITH THE DRY SUPERBLEND POPS AT THIS
TIME.

AVIATION/12Z TAFS/...SHRA EXPECTED TO AFFECT MUCH OF THE AREA
TONIGHT...SO WL CONTINUE TREND TOWARD IFR CIGS THIS EVENING. INITIALLY
DRIER AIR WL SLOW DOWN LOWER CIGS AND VSBYS FROM AFFECT KMSN UNTIL
TNGT.

MARINE...MORE STABLE ONSHORE FLOW TO CONTINUE THRU TONIGHT. HENCE
EXPECT LOW LEVEL INVERSION TO CONTINUE TO KEEP STRONGER GUSTY WINDS
FROM REACHING LAKE SURFACE...HOWEVER LIKELY TO BE A FEW GUSTS
APPROACHING 20KTS. WINDS WL LIGHTEN UP FOR A TIME TONIGHT AS DEEPENING
LOW PRESSURE PASSES BY JUST TO THE EAST.

SFC DEWPTS WL LIKELY WARM INTO THE 40S.  WITH THE LAKE SFC TEMP IN
THE MID TO UPPER 30S...POSSIBLE SOME LIGHT FOG MAY DEVELOP TONIGHT...
WHICH MAY LINGER INTO MON MRNG...BEFORE DRIER AIR AND WEST WINDS
INCREASE. THESE WEST WINDS WL LIKELY REACH SMALL CRAFT ADVY LEVELS
ON MONDAY AS DEEPENING LOW MOVES ACROSS THE CENTRAL GTLAKES INTO
SRN CAN.

&&

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

$$

UPDATE...MRC
TODAY/TONIGHT AND AVIATION/MARINE...MBK
MONDAY THROUGH SATURDAY...COLLAR



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