Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 051553 AAA
AFDMKX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
1053 AM CDT TUE MAY 5 2015

.UPDATE...

AREA OF RAIN OVER SOUTHERN WISCONSIN BEING DRIVEN BY 925MB TO 850
MB MOISTURE CONVERGENCE/FRONTOGENESIS RESPONSE...AS WELL AS BY A
PASSING 500 MB VORTICITY MAXIMUM. MESOSCALE MODELS HAVE THIS AREA
OF RAIN GRADUALLY SHIFTING EAST OF THE AREA EARLY THIS
AFTERNOON...WITH SLIGHTLY DRIER AIR WORKING INTO THE AREA. WILL
CONTINUE THIS TREND WITH THE POPS INTO EARLY AFTERNOON.

ANOTHER WEAK 500 MB VORTICITY MAXIMUM SHIFTS NORTHEAST INTO THE
AREA LATER THIS AFTERNOON INTO THIS EVENING...WITH THE 925 MB TO
850 MB CONVERGENCE/FRONTOGENESIS RESPONSE LINGERING UNTIL LIFTING
NORTHWARD LATER TONIGHT. MESOSCALE MODELS INDICATE SCATTERED
SHOWERS MAY DEVELOP LATER THIS AFTERNOON INTO THIS EVENING WITH
THESE FEATURES. AREA FORECAST SOUNDINGS SHOWING NO
INSTABILITY...SO REMOVED THUNDER WORDING INTO EARLY THIS EVENING.

EAST WINDS...CLOUDS AND PRECIPITATION KEEPING TEMPERATURES IN THE
UPPER 40S TO AROUND 50 SO FAR TODAY. MAY SEE HIGHS RISE A FEW
DEGREES AFTER THE MAIN AREA OF RAIN MOVES OUT. THUS...MAY HAVE TO
LOWER HIGHS INTO THE LOWER TO MID 50S AT BEST IN WESTERN PORTIONS
OF THE AREA...WITH COLDER 40S ALONG THE LAKE.

&&

.AVIATION/18Z TAFS/...

LOOK FOR THE AREA OF RAIN TO GRADUALLY MOVE EAST OF THE TAF SITES
EARLY THIS AFTERNOON. SCATTERED SHOWERS MAY DEVELOP LATER THIS
AFTERNOON INTO THIS EVENING...LINGERING INTO LATER TONIGHT AND
WEDNESDAY. REMOVED THUNDER FROM TAFS AS AIRMASS REMAINS FAIRLY
STABLE INTO TONIGHT. GUSTY EAST NORTHEAST WINDS ARE EXPECTED THIS
AFTERNOON...WEAKENING TONIGHT INTO WEDNESDAY AS THEY BECOME
SOUTHEAST TO SOUTH.

MAY SEE SCATTERED THUNDERSTORMS ON WEDNESDAY...AS WARM FRONT
PUSHES NORTH THROUGH THE AREA. HOWEVER...TOO MUCH UNCERTAINTY WITH
AREAL COVERAGE TO INCLUDE VICINITY THUNDER IN TAFS.

CEILINGS AND VISIBILITIES SHOULD LOWER TO MVFR AND EVENTUALLY IFR
CATEGORY THIS AFTERNOON AND EARLY THIS EVENING...WITH CEILINGS AND
SOME VISIBILITIES BELOW ALTERNATE MINIMUMS POSSIBLE LATER TONIGHT
INTO WEDNESDAY MORNING. LOWEST VALUES WOULD BE AT MILWAUKEE AND
KENOSHA. VFR CONDITIONS SHOULD RETURN BY WEDNESDAY AFTERNOON.

&&

.MARINE...

NORTHEAST WINDS SHOULD GUST TO AROUND 20 KNOTS INTO THIS AFTERNOON
AROUND AND SOUTH OF NORTH POINT LIGHTHOUSE...WITH FAIRLY TIGHT
PRESSURE GRADIENT THERE. A FEW 22 KNOT GUSTS ARE POSSIBLE...BUT
DID NOT THINK THEY WOULD BE FREQUENT ENOUGH FOR A SMALL CRAFT
ADVISORY. WINDS WILL WEAKEN LATER THIS AFTERNOON INTO
TONIGHT...AS PRESSURE GRADIENT WEAKENS.

&&

.PREV DISCUSSION... /ISSUED 321 AM CDT TUE MAY 5 2015/

TODAY AND TONIGHT...FORECAST CONFIDENCE - HIGH TRENDING MEDIUM.

WILL SPREAD CATEGORICAL POPS ACROSS SOUTHERN HALF CWA THROUGH MID-
MORNING AS MID-LEVEL SHORT WAVE OVER CENTRAL IA MOVES E-NE ACROSS
SRN WI/IL BORDER AREA THIS MORNING.  SYNOPTIC SCALE FORCING WILL BE
OVERWHELMING SURGE OF DRIER AIR THAT ACCOMPANIED LAKE BREEZE AND
EASTERLY WINDS WHICH SWEPT ACROSS CWA MON EVE. BUMPED UP POPS TO
LIKELY ACROSS THE NORTH FOR NOW. EARTH NETWORKS LIGHTNING NETWORK
SHOWING OCCASIONAL IN CLOUD FLASHES ACROSS NORTHERN IL WITH A FEW
CLOUD TO GROUND STROKES.  ELEVATED INSTABILITY SPREADS INTO SRN CWA
THIS MRNG ACCOMPANYING SYNOPTIC SCALE FORCING SO WL CONTINUE
THUNDER MENTION. VERTICAL WIND PROFILER IS SHOWING LOW LEVEL JET
OF 30 TO 45 KNOTS ACROSS MO INTO NRN IL WHICH IS 5 TO 10 KTS
STRONGER THAN DEPICTED ON SHORT TERM GUIDANCE AT 06Z. THERE HAVE
BEEN SOME 3 HOUR RAINFALL TOTALS IN THE QUARTER TO HALF INCH RANGE
ACROSS NORTHWEST IL AND KDVN RADAR HAS ESTIMATED ONE HOUR RAINFALL
IN THE SAME RANGE. HENCE WL BEEF UP RAINFALL TOTALS IN THE SOUTH
THROUGH THIS MORNING INTO THE HALF INCH TO 1 INCH RANGE ACROSS THE
SOUTH.

SHORT WAVE SLIDES OFF TO THE EAST LATER THIS MORNING SO WL DECREASE
MID TO HIGH POPS FROM WEST TO EAST.  WL NEED TO HOLD ON TO CHANCE
POPS FOR THUNDER THIS AFTN INTO TONIGHT AS SECOND WEAKER MID-LEVEL
WAVE TAKES SIMILAR PATH ACROSS SRN WI.  IN ADDITION...ELEVATED WARM
FRONT BEGINS TO SHIFT NORTHWARD ACROSS SRN/CENTRAL WI OVERNIGHT IN
RESPONSE TO STRENGTHENING LOW LEVEL JET UPSTREAM OVER PLAINS.
PERSISTENT EAST WINDS AND MOIST LOW LEVELS WL ALSO INCREASE THE
THREAT FOR FOG...ESPECIALLY BY THE LAKE.

WEDNESDAY - CONFIDENCE...MEDIUM
MID LEVEL RIDGE AXIS BUILDS UP ACROSS WI WITH BEST PVA REMAINING
WELL WEST. ANY PRECIP WILL BE DRIVEN BY LOW LEVEL BAROCLINICITY.
MODELS ARE ALL SHOWING SOME PRECIP IN A NW/SE ORIENTATION ALIGNED
WITH THE LOWER LEVEL FORCING WITH THE BETTER THERMAL PACKING. 850
MILLIBAR FRONT LIFTS NORTHEAST LATER IN THE MORNING THOUGH 925 AND
SURFACE BOUNDARY STILL LINGERS SO SOME SHRA/TSRA POTENTIAL. BETTER
LOW LEVEL JET FORCING WILL BE SITUATED ACROSS IA/MN THOUGH SOME
MOISTURE ADVECTION NOTED INTO SRN WI...ESP SC WI. THE NAM SHOWS
LOW LEVEL INVERSION FOR MUCH OF THE DAY WITH LOW LEVEL SE FLOW.
SOME HINTS OF SURFACE BASED CAPE ACROSS SC WI. WILL KEEP THUNDER
MENTION IN PLACE.

THURSDAY - CONFIDENCE...MEDIUM
MID LEVEL RIDGE AXIS WILL BE WELL OFF INTO THE EASTERN LAKES WITH
SOUTHWEST FLOW SETTING UP. A STRONGER SURGE OF WARMTH AND MOISTURE
TAKES SHAPE. MODELS HINT AT WEAK WAVES IN THIS FLOW THOUGH BETTER
DYNAMICS ARE WELL TO THE NORTHWEST ACROSS MN AND NW WI. 925
SOUTHERLY FLOW SENDS TEMPS TO NEAR 20C...SO RATHER WARM DAY
TAKING SHAPE WITH SOME LOCALES CRACKING THE 80 DEGREE MARK. WILL
KEEP SMALL POPS IN PLACE...LOWEST IN EAST A BIT HIGHER IN THE
WEST.

FRIDAY AND FRIDAY NIGHT - CONFIDENCE...LOW
MID LEVEL TROUGH PASSING TO THE NORTH AND ASSOCIATED SURFACE LOW
DRAGS A COLD FRONT THROUGH THE AREA. THE BIG DIFFERENCES ARE WITH
FRONTAL TIMING. THE GFS IS MUCH QUICKER WITH THE FRONT WHILE THE
ECMWF AND GEM ARE SLOWER AND SUGGESTS SHRA/TSRA COULD LINGER WELL
INTO FRIDAY EVENING. WILL KEEP SOME POPS AROUND FRIDAY NIGHT TO
ACCOUNT FOR THE TRENDS IN THE ECMWF/GEM SOLUTIONS.

SATURDAY - CONFIDENCE...LOW
COOLER REGIME EXPECTED WITH FRONT HAVING SETTLED TO THE SOUTH.
SOME WEAK INVERTED TROUGHING NOTED WITH SRN CWA BEING ON NORTHERN
EDGE OF SOME QPF...SO WILL KEEP THE SUPERBLEND POPS FOR NOW.
HOWEVER THE 00Z ECMWF HAS COME IN SHOWING A BIT MORE RETURN WAA
PRECIP DEVELOPING...THIS WITH A LARGELY DRY GEM AND GFS.

SUNDAY AND MONDAY - CONFIDENCE...LOW
NEXT FOCUS WILL BE ON STRENGTH AND TIMING OF STRONGER SHORTWAVE
COMING OUT IN THE SOUTHWEST UPPER FLOW. THE ECMWF SHOWS A STRONGER
AND MORE NORTHWARD PLACED SURFACE LOW WHICH RESULTS IN A PERIOD OF
ELEVATED CONVECTION SUNDAY INTO SUNDAY NIGHT AND BRIEF WARM SECTOR
MONDAY. HOWEVER GFS KEEPS BULK OF CONVECTION OF THE ELEVATED
VARIETY WITH COOLER AIRMASS WITH FRONTAL BOUNDARY TO THE SOUTH.

AVIATION/12Z TAFS/...CIGS EXPECTED TO REACH MVFR AND LIKELY
LOWER FOR A TIME THIS MRNG AS SHOWERS AND A FEW STORMS MOVE ACROSS
SRN WI. BULK OF SHOWERS SHOULD END LATER THIS MRNG INTO THE EARLY
AFTN WITH AN IMPROVEMENT IN VSBY.

CIGS SHOULD RISE SOMEWHAT BUT MOIST LOW LEVEL FLOW AND DIMINISHING
BOUNDARY LAYER WINDS WL LIKELY KEEP CIGS AT MVFR OR LOWER TONIGHT
WITH AN INCREASING RISK OF VSBY RESTRICTIONS FROM FOG.

MARINE...SOME SHORT TERM AND MESOSCALE GUIDANCE SHOWING BURST OF
HIGHER WINDS AFFECTING PORTIONS OF NEARSHORE WATERS THIS MORNING
DUE TO TIGHTENING PRESSURE GRADIENT. HOWEVER HAVE SOME CONCERN DUE
TO WINDS BECOMING MORE ONSHORE THIS MORNING BRINGING DEEPENING LOW
LEVEL INVERSION INTO PLAY...WHICH WOULD PREVENT STRONGER WINDS
FROM REACHING LAKE SURFACE. FOR NOW...WL HAVE GUSTS TO AROUND 22
KNOTS DEVELOPING THIS MORNING AND KEEP EYE ON COASTAL CMAN SITES
AS WELL AS SHIP REPORTS. MAY NEED TO ISSUE QUICK SMALL CRAFT ADVY
THIS MRNG SHOULD GUSTS START TO REACH 25 KTS.

PERIODS OF SHOWERS AND A FEW STORMS THIS MORNING ACROSS MOST OF THE
NEARSHORE...DIMINISHING TO A CHANCE FOR THE AFTN AND TNGT.  DENSE
FOG TO BECOME A CONCERN AS WARMER DEWPOINTS LOCATED JUST TO THE
SOUTH OF LAKE MI BEGIN TO PUSH NWD TNGT THRU WED.

&&

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

$$

UPDATE...WOOD
TODAY/TONIGHT AND AVIATION/MARINE...MBK
WEDNESDAY THROUGH MONDAY...COLLAR


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