Area Forecast Discussion
Issued by NWS Milwaukee/Sullivan, WI

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FXUS63 KMKX 241647 AAA
AFDMKX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MILWAUKEE/SULLIVAN WI
1147 AM CDT FRI APR 24 2015

.UPDATE...

AREA OF RAIN SHOWERS CONTINUE TO DEVELOP ACROSS SOUTHERN MINNESOTA
INTO NORTH CENTRAL AND NORTHEAST IOWA. THIS IS IN RESPONSE TO 700
MB WARM AIR ADVECTION AND FRONTOGENESIS RESPONSE...AS WELL AS FROM
AN ADVANCING 500 MB VORTICITY MAXIMUM. THESE FEATURES SHOULD
CONTINUE TO SLIDE EAST NORTHEAST ACROSS THE AREA THIS AFTERNOON
AND EARLY THIS EVENING...BRINGING SOME LIGHT RAIN SHOWERS TO THE
AREA.

THE BEST SHOT WILL BE ACROSS THE SOUTHERN HALF OF THE AREA...WHERE
BETTER DEEP MOISTURE SHOULD RESIDE. DRY LOW LEVELS BELOW 5000 FEET
ABOVE GROUND LEVEL MAY LIMIT AREAL COVERAGE OF SHOWERS. WILL HAVE
TO ADJUST POPS AFTER WATCHING TRENDS WITH THESE SHOWERS OVER THE
NEXT HOUR OR SO. RAP SOUNDINGS SHOWING WEAK ELEVATED CAPE...LOWER
ON OTHER MODELS...SO WILL NOT INCLUDE THUNDER MENTION AT THIS
TIME.

EAST SOUTHEAST WINDS WILL GRADUALLY INCREASE THIS AFTERNOON...AS
WELL AS THE CLOUD COVER. HIGHS SHOULD REACH THE MIDDLE TO UPPER
50S WELL INLAND...WITH 40S NEAR LAKE MICHIGAN.

WOOD

&&

.AVIATION/18Z TAFS/...

MIDDLE LEVEL CLOUDS WILL CONTINUE TO SPREAD EAST ACROSS TAF SITES
THIS AFTERNOON...AS EAST SOUTHEAST WINDS GRADUALLY INCREASE. ON
AND OFF LIGHT RAIN SHOWERS SHOULD MOVE EAST NORTHEAST THROUGH THE
AREA LATER THIS AFTERNOON AND EARLY THIS EVENING. VFR CONDITIONS
SHOULD REMAIN DURING THIS TIME.

A LULL IN THE SHOWER ACTIVITY SHOULD OCCUR LATER THIS EVENING AND
OVERNIGHT...UNTIL MAIN TROUGH OF LOW PRESSURE SLIDES EAST
SOUTHEAST FROM IOWA INTO CENTRAL ILLINOIS LATER TONIGHT INTO
SATURDAY. AREA OF LIGHT TO MODERATE RAIN SHOULD SPREAD ACROSS TAF
SITES BY MID MORNING ON SATURDAY...LINGERING THROUGH THE DAY. EAST
TO EAST NORTHEAST WINDS WILL REMAIN MODERATE IN STRENGTH LATER
TONIGHT INTO SATURDAY. EXPECT MVFR TO SOMETIMES IFR CEILINGS AND
VISIBILITIES WITH THE RAIN...REMAINING ABOVE ALTERNATE MINIMUMS.

WOOD

&&

.MARINE...

EASTERLY WINDS CONTINUE FOR THE NEARSHORE WATERS THROUGH EARLY
SATURDAY...BEFORE BACKING NORTHEASTERLY AND INCREASING DURING THE
DAY WITH THE STRONG PRESSURE GRADIENT BETWEEN ADVANCING CENTRAL
PLAINS LOW PRESSURE SYSTEM AND SOUTHERN CANADIAN RIDGING.

ONSHORE FLOW WILL BUILD WAVE HEIGHTS INTO THE 3 TO 6 FOOT RANGE
FOR THE NEARSHORE WATERS...AND WIND GUSTS INCREASE TO 20 KNOTS OR
GREATER FROM ROUGHLY 12Z TO 23Z SATURDAY. STILL APPEARS THAT A
SMALL CRAFT ADVISORY WILL BE NEEDED FOR SATURDAY AND SATURDAY
NIGHT.

SPM

&&

.PREV DISCUSSION... /ISSUED 415 AM CDT FRI APR 24 2015/

SHORT TERM...

TODAY AND TONIGHT...FORECAST CONFIDENCE HIGH.

A VORT MAX OVER NE AND THE ASSOCIATED PVA...THETAE ADVECTION...AND
FRONTOGENESIS WILL MOVE INTO SRN WI THIS AFTERNOON. PWS WILL
INCREASE TO 0.60-0.80 INCHES BY LATE AFTERNOON AND MESO MODELS ARE
SHOWING ORGANIZED AREAS OF RAIN. THE WRF MODELS ARE CONCENTRATING IN
THE SRN CWA WHILE THE HRRR IS BRINGING THE RAIN INTO THE NW CWA. THE
DIFFERENCES ARE POSSIBLY RELATED TO WHERE THE 850-700 MB
FRONTOGENESIS WILL SET UP. A CONSENSUS OF MODEL POPS DOES FOCUS MORE
IN THE SOUTH SO WENT WITH 50 POPS BY LATE AFTERNOON THERE WITH
SLIGHT CHANCES IN THE FAR NE CWA. THE TEMPS SHOULD BE ABLE TO WARM
WELL INTO THE 50S AWAY FROM THE LAKE BEFORE THE THICKER CLOUD COVER
ARRIVES BY EARLY AFTERNOON.

KEPT THE POPS SIMILAR THROUGH THE EVENING INTO THE EARLY OVERNIGHT
PERIOD BEFORE BRINGING LIKELY AND CATEGORICAL POPS TO THE SW CWA.
THIS OCCURS AS A STRONGER SHORTWAVE TROUGH CURRENTLY OVER THE DESERT
SW MOVES TO THE MID MO RIVER VALLEY BY 12Z SAT. PVA AND 850 MB
FRONTOGENESIS INCREASES OVER ERN IA AND NRN IL LATE TNT THEN MOVES
INTO FAR SRN WI. EXPECT ALL RAIN WITH SFC TEMPS COOLING INTO THE MID
30S OVER CENTRAL WI TO UPPER 30S FARTHER SOUTH.

SATURDAY... FORECAST CONFIDENCE HIGH.

THE CLOSED UPPER LOW AND ASSOCIATED SURFACE LOW WILL WEAKEN AS THEY
TRACK FROM THE IA/MO BORDER TO SOUTHERN IL ON SATURDAY. IT WILL BE A
RAW DAY IN SOUTHERN WI WITH A DRIVING RAIN FROM THE EAST...
ESPECIALLY IN THE MORNING. SOUTHERN WI WILL BE IN THE REGION OF
VORTICITY ADVECTION... UPPER DIVERGENCE AND Q-VECTOR CONVERGENCE
DUE TO THE RIGHT ENTRANCE REGION OF AN UPPER JET... AND 700MB
FRONTOGENESIS AND STRONG UPWARD MOTION. IT LOOKS LIKE THERE WILL
BE A TIGHT GRADIENT IN THE QPF AMOUNTS. HIGHEST AMOUNTS SHOULD BE
CONCENTRATED WITHIN THE SOUTHERN ONE OR TWO TIERS OF COUNTIES IN
SOUTHERN WI AND THEN SOUTH OF THE WI/IL BORDER CLOSEST TO THE LOW.
THE GFS IS FARTHEST NORTH WITH THE HIGHER QPF THAN THE
CANADIAN...ECMWF AND 06Z NAM.

THE THERMAL TROUGH WILL MOVE ACROSS WI DURING THE DAY SATURDAY. THE
THERMAL PROFILE LOOKS LIKE RAIN FOR THE WHOLE MKX AREA... BUT IT
WILL BE CLOSE WITH A DEEP ISOTHERMAL LAYER RIGHT AROUND ZERO.

PRECIP WILL TAPER OFF DURING THE AFTERNOON AND EXPECT DRY WEATHER
WITH A BRISK NNE WIND SATURDAY NIGHT. DRY AIR SPREADING INTO THE
REGION QUICKLY SHOULD ALLOW FOR CLEARING SKIES EARLY SUNDAY MORNING.
EXPECT LOWS TO BE RIGHT AROUND FREEZING.

LONG TERM...

SUNDAY THROUGH TUESDAY... FORECAST CONFIDENCE HIGH.

RIDGING WILL TAKE HOLD OF THE UPPER MIDWEST EARLY NEXT WEEK. DRY
WEATHER UNTIL AT LEAST TUESDAY AFTERNOON. TEMPERATURES WILL BE ON
THE RISE FOR INLAND AREAS... BUT A PERSISTENT EASTERLY BREEZE OFF OF
LAKE MICHIGAN WILL KEEP LAKESHORE TEMPERATURES IN THE 50S.

TUESDAY NIGHT THROUGH FRIDAY... FORECAST CONFIDENCE MEDIUM.

A 500MB TROUGH WILL CROSS WI TUESDAY EVENING WHICH COULD BRING SOME
LIGHT RAIN OR SPRINKLES. THE GFS IS INITIALLY MORE PROGRESSIVE WITH
THIS TROUGH THAN THE ECMWF... BUT THEN STALLS THE TROUGH OVER THE
NORTHEAST STATES LONGER THAN THE ECMWF LATER NEXT WEEK. OVERALL
SOUTHERN WI SHOULD BE DRY... BUT THERE IS PLENTY OF UNCERTAINTY IN
TEMPERATURES.

AVIATION/12Z TAFS/...MIDDLE LEVEL CLOUDS WILL INCREASE ACROSS SRN
WI THIS AFTERNOON AND EVENING ALONG WITH SCT SHOWERS AS A SHORTWAVE
TROUGH MOVES INTO THE AREA. THE LOW LEVELS WILL REMAIN FAIRLY DRY SO
VFR CONDITIONS WILL STILL PREVAIL WITH PERHAPS MVFR VSBYS WITH ANY
HEAVIER SHOWERS THAT MAY OCCUR. THE RAIN WILL BECOME MORE WIDESPREAD
FOR SAT AM AS A STRONGER SHORTWAVE TROUGH AND LOW PRESSURE AREA
MOVES FROM THE CENTRAL GREAT PLAINS TO THE OHIO RIVER VALLEY. SAT AM
IS WHEN THE CIGS WILL DROP TO 1-3.0 KFT AND VSBYS TO 3-5SM WITH THE
WIDESPREAD MDT RAINFALL.

MARINE...A SMALL CRAFT ADVISORY WILL LIKELY BE NEEDED FOR SAT AND
SAT NT. BRISK ELY WINDS WILL DEVELOP ON SAT AS THE PRESSURE GRADIENT
TIGHTENS BETWEEN POLAR HIGH PRESSURE OVER SRN CANADA AND LOW
PRESSURE MOVING FROM THE CENTRAL GREAT PLAINS INTO THE MIDDLE MS
RIVER VALLEY. THE WINDS WILL TURN NELY FOR SAT AFT AND NIGHT AS THE
LOW TRACKS ACROSS THE OHIO RIVER VALLEY. WAVE HEIGHTS WILL BUILD TO
3 TO 5 FEET DURING THIS TIME.

&&

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

$$

UPDATE...WOOD/SPM
TODAY/TONIGHT AND AVIATION/MARINE...GEHRING
SATURDAY THROUGH THURSDAY...MRC



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