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000
FXUS63 KGRB 171144
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
644 AM CDT FRI MAY 17 2013

UPDATED AVIATION PORTION FOR 12Z TAF ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND SATURDAY
ISSUED AT 346 AM CDT FRI MAY 17 2013

FORECAST CONCERNS THIS PERIOD ON PCPN CHANCES THROUGH THE PERIOD.

WARM FRONT EXTENDS EAST OUT OF NE INTO NORTHERN IL. ONGOING PCPN
OVER IA/MN BORDER...NOW EDGING INTO WESTERN WI. CLOUDS HAVE KEPT
TEMPS UP OVERNIGHT OVER MUCH OF CWA...WITH ONLY THE FAR NORTH
FALLING INTO THE UPPER 30S. EASTERLY WINDS OVER WI...STILL
USHERING IN DRY AIR WITH DEW POINTS IN THE 30S. THIS HAS SLOWED
ADVANCE OF PCPN...THOUGH HIGH BASED...THE RETURNS ARE INCREASING
OVER THE STATE.

HAVE CONTINUED TREND OF EVENING FORECASTER TO SHIFT PCPN SOUTH
INTO CENTRAL AND EAST CENTRAL WI LATER THIS MORNING...THEN SHIFT
NORTH TONIGHT AND SAT AS WARM FRONT LIFTS NORTH/RIDGE BUILDS IN.
HAVE TRENDED TOWARDS MESO MODELS LIKE HRRR FOR DAY 1 PCPN TRENDS.
PCPN FOCUS ASSOCIATED WITH INCREASING ISENTROPIC LIFT/FGEN FORCING
WITH 850 BAROCLINIC ZONE OVER STATE.

HAVE STAYED WITH JUST SHOWER MENTION THROUGH TODAY AS INSTABILITY
MISSING OVER EASTERN WI...BRINGING IN SLIGHT CHANCE LATER TONIGHT
AND SATURDAY AS LOW LEVEL MOISTURE INCREASES AND STEEPER MID
LEVEL LAPSE RATES SHIFT EAST.

TEMPS TODAY TO BE HELD BACK BY CLOUDS AND EAST FLOW THUS STAYED
WITH UPPER 50S AND LOWER 60S THROUGHOUT CWA. MAX TEMPS BACK TO
NORMAL OR ABOVE ON SAT...EXCEPT EAST WITH CONTINUED EASTERLY COMPONENT.

.LONG TERM...SATURDAY NIGHT THROUGH THURSDAY
ISSUED AT 346 AM CDT FRI MAY 17 2013

THE MAIN CONCERN DURING THE LONG TERM IS TIMING PRECIPITATION INTO
THE AREA. A FRONTAL BOUNDARY IS FORECAST TO PUSH NORTHEAST THROUGH
WISCONSIN EARLY NEXT WEEK. SURFACE FLOW WILL BE OFF LAKE MICHIGAN
BETWEEN HIGH PRESSURE TO THE EAST AND THE FRONT...BUT
PRECIPITATION WILL MOVE IN AS THE FRONT PASSES AND THE SURFACE LOW
TO THE WEST GETS CLOSER TO WISCONSIN. HAVE A DRY FORECAST FOR
SATURDAY NIGHT BUT WENT WITH CHANCE POPS FOR CENTRAL AND NORTH
CENTRAL WISCONSIN SUNDAY.

HAVE AT LEAST A CHANCE OF SHOWERS AND THUNDERSTORMS GOING THROUGH
THE MIDDLE OF NEXT WEEK AS THE SURFACE LOW AND UPPER LEVEL CYCLONE
PASS TO THE EAST OF THE AREA.

TEMPERATURES SHOULD REMAIN ABOVE NORMAL THROUGH THE EARLY PART OF
NEXT WEEK BEFORE A SURFACE RIDGE MOVES INTO THE REGION BRINGING
COOLER THAN NORMAL TEMPERATURES FOR THE LATTER HALF OF THE WEEK.
&&

.AVIATION...FOR 12Z TAF ISSUANCE
ISSUED AT 637 AM CDT FRI MAY 17 2013

AREA OF PRECIPITATION HAS MOVE EAST OUT OF IOWA INTO CENTRAL WI AT
THIS TIME. SOME QUESTION ON HOW FAR NORTH PCPN WILL GET THIS
MORNING GIVEN DRY AIR LEFT OVER FROM DEPARTING HIGH PRESSURE.
FORECAST TREND IS FOR THIS AREA TO AFFECT SOUTHERN TAF SITES WITH
MORE SHOWER ACTIVITY FORMING WEST AND LIFTING NORTH AS WARM FRONT
OVER THE PLAINS MOVES NORTH. BEST INSTABILITY TO SAY WELL SOUTH OF
AREA SO WILL NOT MENTION THUNDER. DRY LOW LEVEL FLOW EXPECTED TO
KEEP CIGS IN VFR CAT OR HIGH MVFR IS SOMW SHOWERS.

&&

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

$$

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