Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 212028
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
328 PM CDT MON APR 21 2014

FORECAST DISCUSSION FOR ROUTINE AFTERNOON FORECAST ISSUANCE

.SHORT TERM...TONIGHT AND TUESDAY
ISSUED AT 328 PM CDT MON APR 21 2014

THE FIRST CONCERN DURING THIS PART OF THE FORECAST IS POTENTIAL
FOR SHOWERS AND SOME THUNDER...MAINLY IN EAST CENTRAL WISCONSIN.
19Z SURFACE ANALYSIS SHOWED SOME CONVERGENCE ASSOCIATED WITH A
LAKE/BAY BREEZE IN THE EAST. LOOKED LIKE THERE WAS ALSO A TROUGH
AHEAD OF A COLD FRONT THAT WAS JUST ENTERING THE FORECAST AREA
EARLY THIS AFTERNOON. DEW POINTS WERE MOSTLY IN THE 50S AHEAD OF
THE FRONT...EXCEPT NEAR THE LAKE AND BAY. LOCAL MESO GRAPHICS
SHOWED LAPSE RATES IN EXCESS OF 7 C/KM OVER ALL BUT THE FAR
NORTHEAST CORNER OF THE STATE...AND EVEN SOME 10.5 TO 11 C/KM IN
WESTERN WISCONSIN. MUCAPE VALUES INCREASED INTO THE 200-400 J/KG
RANGE IN CENTRAL WISCONSIN DURING THE AFTERNOON. LIGHTNING DETECTION
WAS NOT INDICATING ANY GROUND STRIKES IN OR NEAR THE AREA THROUGH
1930Z. MODELS ALSO HAD SOME SHORT WAVE ENERGY FORECAST TO PASS
THROUGH THE AREA THIS AFTERNOON AND EVENING. HAVE KEPT RAIN
CHANCES IN THE EAST CENTRAL WISCONSIN THROUGH 00Z WITH A SLIGHT
CHANCE FOR THUNDER IN THE FAR EAST.

MODEL TIME SECTIONS HAD CLOUDS DEVELOPING LATE TONIGHT AND SHOWED
A BIT OF SNOW IN NORTH CENTRAL WISCONSIN. THIS APPEARS TO BE DUE
TO THE COLD CYCLONIC FLOW ON THE BACK SIDE OF THE DEPARTING
SURFACE SYSTEM. DID NOT SEE WHERE ICE CRYSTAL DEVELOPMENT WOULD
OCCUR BASED ON THE LATEST NAM/SREF/GFS BUFKIT TIME SECTIONS...SO
HAVE A CHANCE OF FLURRIES AND SLIGHT CHANCE OF FREEZING DRIZZLE
THERE. NOT GREAT CONFIDENCE IN THIS BUT THOUGHT THERE WAS ENOUGH
OF A POSSIBILITY TO PUT IT IN THE GRIDS.

CLEARING DURING THE NIGHT SHOULD BE AT LEAST PARTIALLY OFFSET BY
MIXING DUE TO WINDS...KEEPING TEMPERATURES FROM TANKING DURING THE
NIGHT AND KEEPING FOG POTENTIAL LOW.

SURFACE HIGH PRESSURE MOVING INTO WISCONSIN WITH AN APPROACHING
UPPER LEVEL RIDGE WILL RESULT IN PLENTY OF SUNSHINE FOR THE
AFTERNOON. TEMPERATURES ARE EXPECTED TO BE COLDER ON TUESDAY DUE
TO THE COLDER AIR MASS IN PLACE AND NORTHERLY SURFACE FLOW.

.LONG TERM...TUESDAY NIGHT THROUGH MONDAY
ISSUED AT 328 PM CDT MON APR 21 2014

RIDGE OF HIGH PRESSURE WILL DRIFT OVER THE REGION TUESDAY NIGHT
INTO WEDNESDAY. ANTICIPATE CLEAR SKIES...DRY AIR AND LIGHT WINDS
WILL PRODUCE A CHILLY NIGHT.

FORECAST CHALLENGE THEN TURNS TO THE DEEPENING UPPER LOW SYSTEM
WITH FRONTAL SYSTEM TO BEGIN IMPACTING THE AREA STARTING LATER
WEDNESDAY. PCPN ASSOCIATED WITH A WARM FRONT BEGINS TO WORKS
NORTHWARD OVER IOWA/MN AND AT LEAST WESTERN WISCONSIN WEDNESDAY
AFTERNOON AND EVENING. DRY AIR OVER EASTERN SECTIONS WILL LIKELY
KEEP PCPN IN CHECK UNTIL LATE WEDNESDAY NIGHT. SHOWERS AND STORMS
WILL BECOME MORE WIDESPREAD TOWARD THURSDAY DUE TO UPPER HEIGHT
FALLS ALONG WITH INCREASED CONVERGENCE ASSOCIATED WITH THE FRONTAL
SYSTEM AND H850 TROUGH PASSAGE. WILL CONFINE THE HIGHER POPS ON
THURSDAY NIGHT OVER FAR NORTHEAST WISCONSIN UNTIL THIS TROUGH
DEPARTS TO THE EAST. BEST CHANCE FOR THUNDERSTORMS WILL BE WITH
THE WARM FRONT PASSAGE OVER MAINLY WESTERN WISCONSIN WEDNESDAY
NIGHT...AND THEN ALONG OR NEAR THE COLD FRONT OR OCCLUDED FRONT
ON THURSDAY FOLLOWED WITH TRAILING DRY SLOT. AS FAR AS SEVERE
POTENTIAL...MAIN SEVERE INDICES STILL NOT SUPPORTIVE OF A SVR
MENTION IN THE HWO AT THIS TIME.

BLEND OF THE PROGS SUGGESTS THE NEARLY STACKED UPPER LOW THEN
SHIFTS INTO EASTERN UPPER MICHIGAN THROUGH MID DAY FRIDAY BEFORE
SLOWLY LIFTING NORTHEAST OF THE GREAT LAKES REGION LATER FRIDAY
FOR FRIDAY NIGHT. HIGHER RH LEVELS ACROSS THE NORTHERN GREAT LAKES
REGION ALONG WITH COLD H850 TEMPS SUPPORT A MIX TYPE WITH THE WRAP
AROUND PRECIPITATION.

MEDIUM RANGE MODELS FROM SATURDAY INTO NEXT MONDAY HAVE BEEN
DIVERTING ON SOLUTIONS THE LAST FEW RUNS WITH LOCATION OF A
FRONTAL BOUNDARY AND THE SOUTHWARD EXTENT OF THE COOL DRY CANADIAN
HIGH PRESSURE SYSTEM OR HUDSON BAY HIGH. LATEST ECMWF AND GFS HAVE
SHIFTED THIS BOUNDARY WELL SOUTH WITH THE GREAT LAKES REGION NOW
BEING DOMINATED BY THE HIGH PRESSURE SYSTEM. A SHORT WAVE TROUGH
IS PROGGED TO SLIDE OVER THE NORTHEAST HALF OF THE STATE SATURDAY
AFTERNOON AND EVENING BUT MOISTURE UNDER THIS HIGH IS EXPECTED TO
BE DRY SO WILL LEAVE DRY.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 108 PM CDT MON APR 21 2014

DENSE FOG ACROSS CENTRAL AND NORTH CENTRAL WISCONSIN THIS MORNING
WAS GONE BY 17Z. THERE WERE SOME IFR CIGS ACROSS NORTH CENTRAL
WISCONSIN AT MIDDAY WITH MVFR CIGS FROM NORTHEAST IN CENTRAL
WISCONSIN AND MOSTLY VFR IN THE EAST CENTRAL PART OF THE STATE.

SHOWERS AND SPRINKLES WERE ACROSS SOUTHERN AND EAST CENTRAL
WISCONSIN...AHEAD OF A COLD FRONT APPROACHING FROM THE WEST
PRODUCED ISOLATED IFR VSBYS IN RAIN.

LIGHTNING CHART WAS ONLY SHOWING A FEW GROUND STRIKES IN SOUTHERN
WISCONSIN THIS MORNING. CONDITIONS SEEM MARGINAL FOR THUNDER THIS
AFTERNOON SO HAVE REMOVED MENTION OF IT FROM TAFS. HAVE ALSO
DOWNPLAYED SHOWERS IN EAST CENTRAL WISCONSIN TAFS BASED ON CURRENT
RADAR TRENDS. A COLD FRONT PASSING THROUGH WILL BRING DRIER
AIR...WITH DEW POINTS MAINLY IN THE 30S...SO DO NOT EXPECT A
REPEAT OF THE FOG FROM THIS MORNING. MODEL TIME HEIGHT SECTIONS
INDICATED SOME HIGH RH VALUES AROUND 2000-3000FT AGL LATE TONIGHT
INTO TUESDAY MORNING. NORTHERLY FLOW OF COLD AIR PASSING ACROSS
LAKE SUPERIOR MAY RESULT IN SOME LAKE EFFECT SNOW SHOWERS IN NORTH
CENTRAL WISCONSIN LATE TONIGHT/EARLY TUESDAY.
&&

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

$$

SHORT TERM.....MG
LONG TERM......TDH
AVIATION.......MG






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