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000
FXUS63 KGRB 220348
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1048 PM CDT TUE MAY 21 2013

UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE

.SHORT TERM...TONIGHT AND WEDNESDAY
ISSUED AT 305 PM CDT TUE MAY 21 2013

MAIN FORECAST CONCERN WILL BE THE PRECIPITATION CHANCES ON
WEDNESDAY...INCLUDING THE POTENTIAL FOR SOME SOAKING RAIN EAST
CENTRAL WISCONSIN.

FOR TONIGHT...A WEAK SFC BOUNDARY WAS SITTING ACROSS NORTHERN
WISCONSIN LATE THIS AFTERNOON...IN THE VICINITY OF AN IRON MT TO
EAU CLAIRE LINE. THIS BOUNDARY HAS BEEN THE FOCUS FOR SHOWERS AND
A FEW THUNDERSTORMS FROM NEAR MARINETTE TO MERRILL. A FEW OF THESE
STORMS MAY CONTAIN PEA TO DIME HAIL AND BRIEF HEAVY DOWNPOURS INTO
THE EARLY EVENING. ACTIVITY SHOULD QUICKLY WEAKEN AFTER SUNSET AS
INSTABILITY WANES. DECREASED POPS IN CENTRAL AND EAST CENTRAL
WISCONSIN AFTER MIDNIGHT FROM PREVIOUS FORECAST AS FRONTAL
BOUNDARY MOVES NORTH...BUT KEPT CHANCE POPS IN NORTHERN WISCONSIN
OVERNIGHT WITH THE BOUNDARY HANGING AROUND THAT AREA. MOSTLY
CLOUDY CONDITIONS SHOULD PREVAIL TONIGHT KEEPING LOW TEMPERATURES
FAIRLY MILD.

FOR WEDNESDAY...UPPER LEVEL DISTURBANCE THAT HAS BEEN SITTING OVER
THE NORTHERN PLAINS THE PAST FEW DAYS WILL FINALLY SHIFT EAST.
MEANWHILE...SFC BOUNDARY THAT MOVED NORTH TUESDAY NIGHT IS THEN
EXPECTED TO COLLAPSE BACK SOUTH. IT LOOKS LIKE TOMORROW AFTERNOON
WILL BE OUR BEST CHANCE THIS WEEK FOR WIDESPREAD PRECIPITATION AS
THE UPPER LEVEL LOW AND SURFACE BOUNDARY SHIFT ACROSS THE STATE.
MODELS SHOWING AMPLE QG FORCING WITH WITH THE UPPER LEVEL TROUGH
WHICH WILL HELP TO INITIATE AN AREA OF RAIN SHOWERS IN THE
VICINITY OF THE SFC BOUNDARY IN CENTRAL WISCONSIN...STARTING
AROUND 12Z. EXPECT THE AREA OF SHOWERS TO EXPAND QUICKLY THROUGH
OUT ALL OF NORTHEAST WISCONSIN THROUGH THE MORNING. ATMOSPHERE
SHOULD REMAIN FAIRLY STABLE WITH WEAK CAPE AND VERY LITTLE
SHEAR...SO NOT EXPECTING ANY SEVERE STORMS WITH ONLY AN ISOLATED
RUMBLE OF THUNDER POSSIBLE. INCREASED POPS A BIT IN THE MORNING
GIVEN THE MODEL TRENDS AND THE AMOUNT OF FORCING THAT WILL BE
MOVING OVER THE AREA...OTHERWISE SEEMS PREVIOUS FORECAST IS ON
TRACK.

THE WRF ARW/NMM AND ECMWF ALSO SUGGEST AN AREA OF HEAVIER
PRECIPITATION ASSOCIATED WITH A SECONDARY SHORTWAVE DISTURBANCE MOVING
NORTHEAST OUT OF THE SOUTHERN PLAINS DURING THE AFTERNOON
WEDNESDAY. THE PRECIPITATION SHIELD WITH THIS SYSTEM MAY ALSO
AFFECT EAST CENTRAL WISCONSIN WEDNESDAY AFTERNOON. DEW POINTS WILL
REMAIN IN THE MIDDLE TO UPPER 50S IN NORTHEAST WISCONSIN WITH
PRECIPITABLE WATER VALUES OVER 1 INCH...THUS AMPLE MOISTURE WILL
BE AVAILABLE. COULD SEE SOME HEAVY RAIN IN EAST CENTRAL WISCONSIN
AS MODEL SOUNDINGS SUGGEST HIGH PRECIPITATION EFFICIENCY....WITH
LONG SKINNY CAPE AND WEAK WIND PROFILES. GIVEN THE MODEL TRENDS
AND MOISTURE ABUNDANCE...ADDED MENTION OF HEAVY RAIN TO THE
FORECAST FOR THE FOX VALLEY AND LAKESHORE.

TEMPERATURES WILL BE MUCH COOLER ON WEDNESDAY GIVEN THE RAIN AND
CLOUDS.

.LONG TERM...WEDNESDAY NIGHT THROUGH TUESDAY
ISSUED AT 305 PM CDT TUE MAY 21 2013

MODELS FORECAST UPPER LOW TO MOVE EAST WEDNESDAY
NIGHT AND THURSDAY WITH NORTHWEST UPPER FLOW RETURNING AS UPPER
RIDGE SLOWLY APPROACHES FROM THE PLAINS. MUCH COOLER AIR WILL
ARRIVE THURSDAY AND THURSDAY NIGHT AS 850MB TEMPERATURES FALL
BELOW FREEZING ACROSS THE NORTH. A FROST OR FREEZE IS LIKELY
THURSDAY NIGHT EXCEPT NEAR THE LAKE AND BAY AS WINDS DIMINISH.
ANOTHER FROST OR FREEZE MIGHT BE POSSIBLE FRIDAY NIGHT BUT THE
MODELS HAVE A SHORT WAVE TROUGH MOVING QUICKLY SOUTH ACROSS THE
WESTERN GREAT LAKES IN THE NORTHWEST UPPER FLOW. THIS WOULD
PROBABLY PRODUCE ENOUGH CLOUDS AND WIND TO KEEP A FROST OR FREEZE
FROM OCCURRING FRIDAY NIGHT. THE UPPER RIDGE GETS CLOSER SUNDAY AND
MONDAY BUT THE UPPER FLOW STAYS NORTHWEST AND THERE IS A BIG
SURFACE HIGH TO OUR EAST. THAT WILL PROBABLY BE SUFFICIENT TO KEEP
ANY PRECIPITATION TO OUR WEST. TEMPERATURES WILL SLOWLY WARM AS
HEIGHTS RISE.
&&

.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 1042 PM CDT TUE MAY 21 2013

ISOLD/SCT SHOWERS WILL CONTINUE ACROSS FAR NORTHERN WI OVERNIGHT.
A SOLID AREA OF STRATOCUMULUS (BASES 5-7K FT) WILL COVER MOST OF
THE REGION OVERNIGHT. THIS MAY PREVENT WIDESPREAD LOW CIGS/FOG
FROM DEVELOPING...BUT SOME LOW CLOUDS/FOG WILL STILL DEVELOP WHERE
SIGNIFICANT RAIN OCCURRED DURING THE AFTERNOON AND EVENING (MAINLY
NC/NE WI)...AND NEAR THE LAKE/BAY (MARINE FOG). THE MARINE FOG
WILL BE LOCALLY DENSE ALONG THE SHORELINE. SHOWERS WILL INCREASE
AGAIN ON WEDNESDAY...WITH THE MOST SIGNIFICANT RAINFALL EXPECTED
OVER NORTHEAST AND EAST CENTRAL WI DURING THE LATE AFTERNOON AND
EVENING. WIDESPREAD MVFR/IFR CONDITIONS CAN BE EXPECTED IN
ASSOCIATION WITH THE RAIN.
&&

.MARINE...
ISSUED AT 651 PM CDT TUE MAY 21 2013

DENSE FOG ON LAKE MICHIGAN IS EXPECTED TO CONTINUE TONIGHT INTO
WEDNESDAY...SO HAVE EXTENDED THE DENSE FOG ADVISORY THROUGH 21Z/WEDS.
HAVE ALSO ADDED THE NORTHERN BAY ZONE TO THE ADVISORY. A COLD
FRONT WILL MOVE THROUGH WEDNESDAY AFTERNOON OR EVENING AND PRODUCE
STRONG NORTHEAST WINDS AND LARGE WAVES HAZARDOUS TO SMALL CRAFT
WEDNESDAY NIGHT THROUGH THURSDAY. IT WILL ALSO BRING DRIER AIR...
WHICH WILL QUICKLY IMPROVE VISIBILITIES ON THE LAKE/BAY.
&&

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

$$

SHORT TERM.....WOLF
LONG TERM......RDM
AVIATION.......KIECKBUSCH
MARINE.........KIECKBUSCH