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000
FXUS63 KGRB 141730
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1230 PM CDT TUE MAY 14 2013

UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND WEDNESDAY
ISSUED AT 436 AM CDT TUE MAY 14 2013

FORECAST CONCERNS ON TEMPERATURES TODAY AND CHANCE FOR
THUNDERSTORMS LATER THIS AFTERNOON AND THIS EVENING. HAVE TRENDED
TOWARDS GEM/NAM FOR GUIDANCE ON THIS PACKAGE. ECMWF NOW TRENDING
TOWARDS NAM WITH BETTER CHANCE FOR PCPN A BIT FURTHER SOUTH INTO
CENTRAL WI CLOSER TO WARM FRONT POSITION.

LAST EVENING SOUNDINGS SHOWS WHAT THE ISSUE WITH THIS
FORECAST...THAT BEING TOO DRY. AREA OF HIGH BASED SHOWERS WENT
THROUGH LAST NIGHT AROUND MIDNIGHT ASSOCIATED WITH STRONG WAA/850
WARM FRONT. NOTHING MORE THAN SPRINKLES SEEN. MID CLOUDINESS NOW
EXITING EASTERN WI.

FOCUS ON FAST MOVING SHORT WAVE ALONG CANADIAN BORDER AND FRONTAL
SYSTEM NOW MOVING THROUGH NORTHERN PLAINS. BY MID AFTERNOON...WARM FRONT
TO LIFT NORTH INTO SOUTHWEST WI. RATHER WARM AIR MASS TO PUSH INTO
STATE TODAY WITH 850 TEMPS INTO THE 20S OVER CENTRAL WI. WITH STEEP
MID-LEVEL LAPSE RATES BETWEEN 8 AND 9 C/KM....AND WARM
FRONT...WILL CONTINUE TO CARRY SMALL/ISOLD CHANCE FOR
THUNDERSTORMS. MODEL SOUNDINGS SUGGEST STRONG CIN THROUGH THE DAY
GIVEN DRY AIRMASS BELOW 600MB. SOUNDINGS ALSO SHOW CAPE HIGH
BASED...MAINLY ABOVE 600MB. THIS TO LEAD TO HIGH BASED
THUNDERSTORM THREAT...WHICH IF STORMS DO DEVELOP WOULD LIKELY LEAD TO
GUSTY WINDS...POSSIBLY HAIL. COLD FRONT TO PUSH THROUGH STATE BY
MIDNIGHT LEADING TO DRY FORECAST FOR REST OF NIGHT AND WEDNESDAY.

ON WEDNESDAY...GUSTY NORTHWEST WINDS BEHIND FRONT AND LOW
HUMIDITIES WITH MIXING TO 5K FEET OR HIGHER MAY LEAD TO INCREASED
FIRE DANGER.

TEMPERATURES TO BE WELL ABOVE NORM TODAY...DROPPING CLOSER TO
NORMS ON WEDNESDAY. FEW MODELS...INCLUDING HRRR SUGGEST 90 INTO
SOUTHWEST WI. HAVE BUMPED TEMPS UP SLIGHTLY THROUGHOUT CWA.

.LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY
ISSUED AT 436 AM CDT TUE MAY 14 2013

SURFACE HIGH PRESSURE MOVING ACROSS THE REGION AHEAD OF AN UPPER
LEVEL RIDGE SHOULD KEEP THE EARLY PART OF THE LONG TERM FORECAST
DRY. THE 00Z NAM AND 00Z GFS GENERATED SOME QPF DURING THE DAY ON
THURSDAY...BUT SINCE THE 00Z ECMWF...PREVIOUS FORECAST AND
SURROUNDING GRIDS WERE DRY...A DRY FORECAST APPEARED TO BE THE WAY
TO GO.

A SHORT WAVE AND WARM ADVECTION AHEAD OF A SURFACE TROUGH
APPROACHING FROM THE PLAINS WILL BRING A CHANCE OF SHOWERS AND
THUNDERSTORMS TO THE AREA STARTING ON FRIDAY. VARIOUS SHORT WAVES
AHEAD OF THE MAIN UPPER TROUGH AND A SURFACE FRONTAL
BOUNDARY...COMBINED WITH A FEED OF GULF MOISTURE AHEAD OF A
DEVELOPING SURFACE LOW WILL KEEP AT LEAST A CHANCE OF SHOWERS AND
THUNDERSTORMS THROUGH THE END OF THE FORECAST PERIOD.

CLOUDS AND PRECIPITATION WILL KEEP TEMPERATURES FROM WARMING TOO
MUCH ABOVE NORMAL DURING THE DAYTIME...BUT THE SAME FACTORS SHOULD
KEEP TEMPERATURES WELL ABOVE NORMAL AT NIGHT.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1230 PM CDT TUE MAY 14 2013

WEAKENING MID-LEVEL DISTURBANCE WILL GENERATE SCT VERY
LIGHT SHOWERS OVER NORTH-CENTRAL AND CENTRAL WISCONSIN THROUGH
MID-AFTERNOON...BUT CONDITIONS TO REMAIN VFR.  THEN LOW PRESSURE
WILL MOVE ACROSS CENTRAL MINNESOTA AND THE UPPER PENINSULA TONIGHT.
ISOLATED STORMS ARE POSSIBLE AHEAD OF THIS LOW...MAINLY ACROSS THE
UPPER PENINSULA...BUT THINK THE AIRMASS WILL BE TOO DRY FOR
THUNDERSTORM DEVELOPMENT OVER CENTRAL AND NORTHERN WISCONSIN.  LLWS
TO DEVELOPMENT THIS EVENING AHEAD OF THE LOW...AND THEN BEHIND THE
LOW AS WELL.  VFR CONDITIONS EXPECTED TOMORROW WITH GUSTY NORTHWEST
WINDS.
&&

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

$$

SHORT TERM.....TE
LONG TERM......MG
AVIATION.......MPC