Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 011947
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
247 PM CDT FRI MAY 1 2015

FORECAST DISCUSSION FOR ROUTINE AFTERNOON FORECAST ISSUANCE

.SHORT TERM...TONIGHT AND SATURDAY
ISSUED AT 247 PM CDT FRI MAY 1 2015

THIS AFTERNOON THROUGH SATURDAY

MID AND HIGH CLOUDS CONTINUE TO STREAM IN AHEAD OF AN APPROACHING
TROUGH CURRENTLY MAKING ITS WAY THROUGH WESTERN WISCONSIN. THIS
TROUGH HAS PRODUCED LITTLE IN THE WAY OF RAIN AS IT HAS TRACKED
THROUGH NORTHWESTERN WISCONSIN...WITH CLOUD BASES AROUND 10K FT
WITH THIS FEATURE. UPSTREAM OBSERVATIONS SEEM TO INDICATE THIS
FEATURE WILL MAINLY PASS THROUGH AS VIRGA AND LITTLE ELSE.
THEREFORE WILL SCALE BACK POPS A BIT THIS AFTERNOON AS THE CHANCE
OF MEASURING SEEM SLIM TO NONE GIVEN THE EXTREMELY DRY AIRMASS IN
PLACE AS EVIDENCED BY SURFACE RELATIVE HUMIDITIES IN THE 20S.

DESPITE THE WAA IN EFFECT TONIGHT...MODELS HAVE BACKED OFF A BIT
ON THE SPRINKLES ACROSS THE NORTH DURING THE OVERNIGHT HOURS.
GIVEN THE HIGH BASES THIS INITIAL TROUGH IS ADVECTING IN DO NOT
THINK BASES WILL BE SUFFICIENTLY LOW ENOUGH FOR ANY MID LEVEL
ACTIVITY TO BRING RAIN TO THE SURFACE. WITH THIS IN MIND WILL GET
RID OF THE SPRINKLES ACROSS THE NORTH OVERNIGHT. THE
AFOREMENTIONED WAA AND CLOUD COVER SHOULD KEEP OVERNIGHT LOWS A
BIT WARMER IN THE 40S.

HIGH PRESSURE WILL SETTLE OVER THE OHIO VALLEY ON
SATURDAY...ALLOWING FOR RETURN FLOW ON THE BACKSIDE. THE HIGH WILL
KEEP CONDITIONS DRY...HOWEVER WARMING 850 MB TEMPERATURES TO
AROUND +10 CELSIUS WILL ALLOW DAYTIME HIGHS TO GET INTO THE 70S
AWAY FROM THE GREAT LAKES SATURDAY AFTERNOON.

.LONG TERM...SATURDAY NIGHT THROUGH FRIDAY
ISSUED AT 247 PM CDT FRI MAY 1 2015

PCPN TRENDS WITH SEVERAL FRONTAL SYSTEMS...SEVERE TSTM POTENTIAL
SUNDAY AFTERNOON AND EVENING...AND TEMPERATURES...WILL BE THE
MAIN FCST CONCERNS.

A FEW MODELS STILL SHOW SPOTTY SHOWER ACTIVITY SATURDAY NIGHT...
DUE TO WEAK WAA AND THE PRESENCE OF A MOISTURE AND INSTABILITY
GRADIENT OVER THE REGION. RATHER THAN THROW IN SLIGHT CHC POPS
OVER THE ENTIRE CWA...HAVE DECIDED TO KEEP A DRY FCST INTACT.

PCPN CHANCES WILL INCREASE SUBSTANTIALLY SUNDAY AFTERNOON AND
NIGHT...AS A COLD FRONT AND STRONG MOISTURE CONVERGENCE MOVES
THROUGH THE REGION. AHEAD OF THE FRONT...GUSTY SW WINDS WILL PULL
A WARMER AND MORE MOIST AIR MASS INTO THE REGION...WITH TEMPS
REACHING THE MIDDLE 70S TO LOWER 80S...AND DEW POINTS RISING INTO
THE LOWER TO MIDDLE 50S. CAPE IS EXPECTED TO INCREASE TO 1000-1500
J/KG OVER NC/C WI DURING THE AFTERNOON...AND WHEN COUPLED WITH
DEEP LAYER SHEAR OF 25 TO 35 KTS...SUPPORTS AT LEAST AN ISOLD SVR
TSTM THREAT DURING THE AFTERNOON AND EARLY EVENING HOURS. HAVE
BOOSTED QPF AMOUNTS CONSIDERABLY DURING THIS PERIOD.

THE FRONT IS EXPECTED TO DROP SOUTH OF THE REGION MONDAY INTO
TUESDAY...RESULTING IN A DRY PERIOD FOR THE START OF THE NEXT
WORK WEEK. THE FRONT IS EXPECTED TO LIFT BACK NORTH AS A WARM
FRONT TUESDAY NIGHT INTO WEDNESDAY...AS LOW PRESSURE DEVELOPS
OVER THE PLAINS. THIS WILL BRING A CHANCE OF SHOWERS AND ISOLD
TSTMS BACK INTO THE REGION.

PCPN CHANCES WILL RAMP UP AGAIN TOWARD THE END OF THE WORK WEEK
AS THE PLAINS LOW AND ASSOCIATED COLD FRONT EDGE TOWARD WI. MODELS
ARE IN POOR AGREEMENT DURING THIS PERIOD...AS THE ECMWF IS MORE
PROGRESSIVE WITH THE FRONT...WHILE THE GFS STALLS THE LOW TO
OUR WEST. THE GEFS IS SOMEWHERE IN BETWEEN AND SUGGESTS A WEAKER
AND SLOWER FRONTAL PASSAGE THAN THE ECMWF. DESPITE THE
DIFFERENCES...THERE IS STILL A GOOD SIGNAL FOR PCPN CENTERED
AROUND THE THURSDAY NIGHT PERIOD...SO WILL HAVE HIGH CHC/LIKELY
POPS FOR THAT PERIOD.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1221 PM CDT FRI MAY 1 2015

VFR CONDITIONS TO PREVAIL THIS AFTERNOON THROUGH
SATURDAY. A WEAK TROUGH OF LOW PRESSURE PASSING THROUGH THIS
AFTERNOON AND EVENING MAY PRODUCE A PERIOD OF MID LEVEL
CLOUDS...AND ISOLATED LIGHT SHOWERS OR SPRINKLES OVER PARTS OF
CENTRAL AND NORTH CENTRAL WISCONSIN. HOWEVER UPSTREAM RADAR AND
METAR OBSERVATIONS SHOW THE LIKELIHOOD OF ANY LIQUID REACHING THE
GROUND WILL BE RATHER LOW.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM.....KURIMSKI
LONG TERM......KIECKBUSCH
AVIATION.......KURIMSKI





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