Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 290149
AFDMKX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
849 PM CDT TUE APR 28 2015

.UPDATE...
THE COMPACT MID LEVEL SHORT WAVE OVER NORTH CENTRAL IOWA WILL
CONTINUE TO TRACK SOUTH OVERNIGHT...HAVING NO REAL IMPACT ON OUR
AREA. WE MIGHT SEE SOME MID AND HIGH LEVEL CLOUDS DRIFT
THROUGH...OTHERWISE ANOTHER QUIET NIGHT IN STORE. THE NEXT STRONG
SHORT NORTH OF LAKE SUPERIOR WILL WORK SOUTH LATER TONIGHT INTO
WEDNESDAY AND MAY BRING THE AREA SOME SHOWERS DURING THE AFTERNOON
AND EVENING. A RUMBLE OF THUNDER IS POSSIBLE GIVEN THE INSTABILITY
FROM THE COLD TEMPS ALOFT WITH THE CLOSED H5 LOW MOVING OVERHEAD.

&&

.AVIATION/06Z TAFS/...
VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD WITH WINDS
GENERALLY AT OR BELOW 10KTS. SOME SHOWERS OR EVEN A THUNDERSTORM
ARE POSSIBLE AWAY FROM THE LAKE WEDNESDAY AFTERNOON AND EVENING
AS A STRONG MID LEVEL LOW PRESSURE SYSTEM MOVES OVERHEAD.

&&

.PREV DISCUSSION... /ISSUED 330 PM CDT TUE APR 28 2015/

TONIGHT AND WEDNESDAY...FORECAST CONFIDENCE - HIGH.

A MID LEVEL TROUGH WILL SLIDE DOWN THROUGH WI OVERNIGHT. THIS TROUGH
IS PRODUCING LIGHT RAIN ACROSS MN TODAY. THERE WILL BE TOO MUCH LOW
LEVEL DRY AIR FOR ANY PRECIP ACROSS SOUTHERN WI TONIGHT... SO JUST
SOME MID LEVEL CLOUDS ARE IN THE FORECAST WITH THIS FEATURE.

SURFACE WINDS WILL BE OUT OF THE NORTH-NORTHEAST IN THE WAKE OF THE
TROUGH WEDNESDAY MORNING... EARLIEST NEAR THE LAKE AS THE COOLER AIR
RACES DOWN THE LAKE FASTER THAN INLAND... CALLED A BACK DOOR COLD
FRONT. WINDS WILL BECOME EAST NEAR THE LAKE BY THE AFTERNOON WITH
THE LAKE BREEZE COMPONENT.

A CLOSED 500MB LOW WILL SLIDE DOWN INTO THE WESTERN GREAT LAKES
WEDNESDAY AFTERNOON. THIS WILL CREATE STEEP LOW LEVEL LAPSE RATES
WITH ENOUGH INSTABILITY FOR AT LEAST SCATTERED SHOWERS AND A FEW
RUMBLES OF THUNDER. THE SHOWERS WILL BE MAINLY DIURNALLY DRIVEN...
AND MOST CONCENTRATED ALONG THE LAKE BREEZE CONVERGENCE ZONE. A FEW
STRAY SHOWERS ARE POSSIBLE OVER THE LAKE DUE TO JUST ENOUGH MID
LEVEL MOISTURE AND FORCING.

TEMPERATURES ON WEDNESDAY WILL BE SIMILAR TO WHAT THEY WERE TODAY.

WEDNESDAY NIGHT THROUGH FRIDAY...FORECAST CONFIDENCE - MEDIUM.

MAIN CONCERN THIS PERIOD COMES UP LATER WEDNESDAY NIGHT INTO
THURSDAY. SHORT TERM GUIDANCE IN AGREEMENT ON CARRYING VIGOROUS MID-
LEVEL SHORT WAVE TROF SOUTHWARD ACROSS LAKE MICHIGAN AREA LATER WED
NGT INTO THU IN RESPONSE TO DEEPENING MID-LEVEL LOW PRESSURE OVER
CENTRAL GTLAKES. PWAT VALUES OF ABOUT 0.5 INCH BELOW 10K FEET AS
THIS WAVES SLIDES SOUTHWARD AFFECTING ERN CWA.  DESPITE STRENGTH OF
WAVE AND VORTICITY ADVECTION...LAYER Q-VECTOR CONVERGENCE FAIRLY
WEAK.  LEFT EXIT REGION OF UPPER JET GRAZES FAR ERN WI HOWEVER
STRONGEST SYNOPTIC SCALE FORCING FARTHER EAST.  DUE TO LIMITED
MOISTURE...LATE NIGHT TIMING AND QUESTIONABLE FORCING...WL HOLD OFF
ON INTRODUCING ANY POPS AT THIS POINT.

AFTER VIGOROUS UPPER LOW SWINGS SOUTHEAST OF THE REGION LATER
THURSDAY...HIGH PRESSURE AND INCREASING SUBSIDENCE SETTLE INTO THE
REGION LATER THU INTO FRI.  A SURGE OF COOLER AIR WILL ACCOMPANY LOW
PRESSURE SO DAYTIME TEMPS ON THU LOOK A FEW DEGREES COOLER THAN WED.
ALSO LIKELY TO BE A BIT MORE CLOUDINESS IN THE EAST DURING THE DAY.
DAYTIME TEMPS WILL REBOUND ON FRIDAY WITH LIGHT SOUTHERLY FLOW AHEAD
OF APPROACHING TROF IN MINNESOTA AND IOWA.  FEW WESTERN AREAS MAY
REACH 70 ON FRI.

FRIDAY NIGHT THROUGH TUESDAY...FORECAST CONFIDENCE - MEDIUM.

LOW PRESSURE OVER EASTERN CONUS WILL GET NUDGED EASTWARD ACROSS
WESTERN ATLANTIC EARLY IN THE PERIOD BY INCREASINGLY ZONAL MID-LEVEL
STEERING FLOW ACROSS WESTERN TWO THIRDS OF CONUS. ZONAL FLOW WL
ENSURE TEMPS STAY NEAR OR ABOVE NORMAL FOR THE BULK OF THE EXTENDED
PERIOD.  EVEN AREAS NEAR LAKE MICHIGAN SHOULD ENJOY MORE BOUTS OF
WARMER TEMPS DUE TO A GREATER LIKLIHOOD OF SOUTH TO SOUTHWEST WINDS
AT TIMES.

MEDIUM RANGE GUIDANCE SHOWING A BIT MORE AMPLITUDE TO SHORT WAVE
TROF MOVING ACROSS WI LATER FRI/FRI NIGHT.  COLUMN PRECIPITABLE
WATER JUST UNDER THREE QUARTERS INCH BUT UNCERTAIN WHETHER FORCING
WILL BE STRONG ENOUGH TO UTILIZE AVAILABLE MOISTURE.  DUE TO
UNCERTAINTY...WL HOLD OFF ON INTRODUCING ANY POPS TO FRI NGT. SHORT
WAVE ALSO WEAKENS AS IT PROGRESSES EWD OVER GTLAKES AS IT RUNS INTO
WEAKENING HIGH PRESSURE RIDGE.

SOME DESCREPANCIES CREEP INTO MEDIUM RANGE GUIDANCE LATER IN THE
WEEKEND REGARDING UPPER LEVEL STEERING FLOW...BUT DIFFERENCES SMALL.
00Z ECMWF WAS SHOWING MORE BROADSCALE TROFFING ACROSS CANADA INTO
NORTHERN CONUS WHILE GFS MAINTAINS FASTER ZONAL FLOW SCENARIO.  12Z
GUIDANCE COMING INTO BETTER AGREEMENT BUT ECMWF AND GEM STILL SHOW
SLIGHTLY WARMER...SOUTHWEST FLOW ALOFT. ECMWF SOLUTION WOULD RESULT
IN DEEPER GULF MOISTURE AND WARMER TEMPS BY AROUND MONDAY.  DESPITE
QUESTIONABLE MOISTURE SOURCE...ALL MEDIUM RANGE GUIDANCE IN
AGREEMENT ON LOW PRESSURE DEVELOPING ALONG FRONTAL BOUNDARY DRAPED
ACROSS UPPER MIDWEST LATER SUNDAY AND MOVING NORTHEAST ACROSS WI ON
MONDAY.  WILL MAINTAIN HIGH CHANCE TO LOW LIKELY POPS FOR THUNDER IN
THE MONDAY TIME FRAME. WL CARRY LOWER POPS INTO MON NGT/TUE DUE TO
SLOWER EWD PROGRESSION OF MID-LEVEL SHORT WAVE TROF DEPICTED BY
ECMWF.  ECMWF CARRIES NOSE OF LOW LEVEL JET INTO SRN WI SUN NGT
WHILE GFS FOCUS FARTHER SOUTH.  AT THIS POINT...SEVERE WEATHER
PARAMETERS LOOK MINIMAL WHEN EXAMINING ECMWF FORECAST
SOUNDINGS FOR SUN NGT.

NCEP CLIMATE FORECAST SYSTEM LONG RANGE PLUME DEPICTS TEMPERATURES
HOVERING AROUND SEASONAL NORMAL THROUGH MAY.

AVIATION/00Z TAFS/...

VFR CONDITIONS THROUGH THE FORECAST PERIOD. AN UPPER LEVEL TROUGH OF
LOW PRESSURE WILL CROSS WISCONSIN TONIGHT. LOW LEVELS ARE TOO DRY
FOR ANY PRECIP TO REACH THE GROUND... SO ONLY SOME MID-LEVEL CLOUDS
TO MARK PASSAGE OF TROUGH. WEDNESDAY AFTERNOON WILL BRING SCATTERED
SHOWERS WITH A SMALL CHANCE FOR THUNDER AS AN UPPER LEVEL LOW TRACKS
OVERHEAD.

FIRE WEATHER...

RELATIVE HUMIDITY VALUES OF 30 TO 40 PERCENT WILL BE ON THE LOW SIDE
THROUGH THE WEEKEND INLAND FROM THE LAKE. SCATTERED SHOWERS AND A
FEW THUNDERSTORMS ARE EXPECTED WEDNESDAY AFTERNOON. OTHERWISE IT IS
A DRY FORECAST UNTIL SATURDAY NIGHT.

MARINE...

TREND TOWARD STRONGER SURGE OF LOW LEVEL COLD AIR ACROSS LAKE MI
AREA WED NIGHT INTO THU.  SURGE OF COLD AIR WILL CONTRIBUTE TO
DEEPENING SFC LOW PRESSURE OVER ERN OH VALLEY REGION ON THU. LOW
LEVEL INVERSION WILL BE SHALLOW DURING THIS PERIOD DUE TO COLD LAKE
SURFACE TEMPS.  HENCE EXPECTING SOME GUSTY WINDS TO REACH LAKE
SURFACE.  WIND GUSTS WILL APPROACH 25 KTS SO A SMALL CRAFT ADVISORY
MAY NEED TO BE ISSUED IN LATER FORECAST PERIODS.


&&

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

$$

UPDATE...DAVIS
TONIGHT/WEDNESDAY AND AVIATION/MARINE...MRC
WEDNESDAY NIGHT THROUGH TUESDAY...MBK


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