Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 241944
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
244 PM CDT SUN AUG 24 2014

FORECAST DISCUSSION FOR ROUTINE AFTERNOON FORECAST ISSUANCE

.SHORT TERM...TONIGHT AND MONDAY
ISSUED AT 243 PM CDT SUN AUG 24 2014

THE LATEST RAP ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW UPPER LEVEL
LOW PRESSURE OVER EASTERN MONTANA AND A DOUBLE BARRELED SURFACE LOW
OVER NORTH DAKOTA.  A WARM FRONT EXTENDS FROM THIS SURFACE LOW OVER
SOUTHWEST WISCONSIN...WHICH MARKS THE TRANSITION FROM MOSTLY CLOUDY
SKIES TO CLEAR CONDITIONS.  A COLD FRONT EXTENDS SOUTHWARD OVER THE
CENTRAL PLAINS AND IS LARGELY INACTIVE AT THIS HOUR THOUGH THAT
MIGHT BE CHANGING OVER CENTRAL MINNESOTA WHERE ML CAPES HAVE
EXCEEDED 2000 J/KG.  A FEW OTHER ELEVATED STORMS CONTINUE TO DEVELOP
OVER NORTHWEST WISCONSIN WITHIN THE TAIL END OF A VORT MAX.  WILL
ADD A CHANCE TO N-C WISCONSIN BETWEEN 21Z AND 00Z.  AS THE UPPER LOW
AND COLD FRONT MOVE EAST...THUNDERSTORM AND SEVERE WEATHER CHANCES
ARE THE MAIN FORECAST CONCERNS.

TONIGHT...THE LARGE UPPER LOW WILL MOVE ACROSS NORTH DAKOTA INTO THE
LAKE WINNIPEG REGION.  MID-LEVEL HEIGHT FALLS FROM THE SYSTEM WILL
MOVE INTO THE WESTERN GREAT LAKES...WHICH WILL HELP PUSH A WEAK COLD
FRONT INTO WESTERN WISCONSIN AFTER MIDNIGHT.  CONVERGENCE ALONG THE
FRONT IS RELATIVELY WEAK...BUT ELEVATED INSTABILITY APPROX 1000-1500
J/KG (ROUGH ESTIMATE) WILL MOVE INTO CENTRAL AND NORTH-CENTRAL
WISCONSIN AFTER MIDNIGHT.  BECAUSE OF THE WEAK FORCING...KEPT
CHANCES OF PRECIP IN THE SCATTERED RANGE.  THE MAGNITUDE OF CAPE AND
WIND SHEAR AROUND 30 KTS WOULD SUPPORT A CHANCE OF STRONG STORMS
THAT COULD PRODUCE NEAR SEVERE HAIL AND WIND GUSTS.  WILL LEAVE A
MENTION OF THIS POSSIBILITY IN THE HWO.  THE MESO MODELS CONTINUE TO
SHOW CONVECTION DEVELOPING OVER CENTRAL MINNESOTA LATER THIS
AFTERNOON BEFORE TRACKING THE STORMS INTO NORTH-CENTRAL WISCONSIN
AFTER 06Z.  THIS STILL SEEMS POSSIBLE BASED ON THE DESTABILIZATION
TAKING PLACE OVER CENTRAL MINNESOTA.  THE STORMS SHOULD WEAKEN AS
THEY MOVE EAST LATE TONIGHT DUE TO DIMINISHING INSTABILITY.
OTHERWISE...LOOK FOR A MUGGY EVENING WITH LOWS DROPPING INTO THE
MIDDLE AND UPPER 60S.

MONDAY...THE FRONT WILL MAKE LITTLE PROGRESS TO THE EAST AND INTO
NORTH-CENTRAL WISCONSIN DURING THE AFTERNOON.  SPOTTY SHOWERS AND
STORMS WILL BE POSSIBLE AHEAD OF THE FRONT DURING THE MORNING ACROSS
MUCH OF THE AREA.  ASSUMING COVERAGE IS NOT MORE THAN
ADVERTISED...LOW LEVEL SOUTHWEST WINDS WILL PUSH TEMPS INTO THE
UPPER 80S OR LOWER 90S OVER THE EASTERN FORECAST AREA.  COMBINED
WITH DEWPOINTS AROUND 70 DEGREES...ML CAPES ARE PROJECTED TO REACH
2K-3K J/KG WITH BULK SHEARS AROUND 30 KTS.  CONVERGENCE ALONG THE
FRONT WILL REMAIN WEAK BUT CANNOT RULE OUT ISOLATED OR SCATTERED
STRONG TO SEVERE STORMS OVER THE EAST DURING THE AFTERNOON WITH THAN
KIND OF INSTABILITY AND SHEAR.  DRIER MID-LEVEL AIR WILL WORK INTO
CENTRAL AND NORTH-CENTRAL WISCONSIN DURING THE AFTERNOON...WHICH
WILL MAKE IT HARDER FOR STORMS TO INITIATE.  THE COMBINATION OF HEAT
AND HUMIDITY WILL PUSH HEAT INDICES INTO THE MIDDLE 90S.

.LONG TERM...MONDAY NIGHT THROUGH SUNDAY
ISSUED AT 243 PM CDT SUN AUG 24 2014

MODELS CONTINUE TO INDICATE A RATHER AMPLIFIED MEAN FLOW PATTERN ACROSS
THE CONUS WITH AN UPPER TROF CURRENTLY OVER THE INTER MOUNTAIN
WEST AND SIG RIDGE OVER THE EASTERN LAKES. THE MOVEMENT OF UPPER
LOW OUT OF TROF INTO THE WESTERN LAKES EARLY IN THE PERIOD WILL BE
THE PRIMARY WEATHER FEATURE TO IMPACT OUR WEATHER. BY LATE THIS
WEEK...MODELS CONTINUE TO SHOW LINGERING PIECE OF TROF MEANDERING
INTO THE CENTRAL U.S. THE MOVEMENT OF THIS FEATURE CONTINUES TO
SLOW AS IT REMAINS CUT OFF FROM MAIN BAND OF WESTERLIES EXPECTED
TO LIE OVER SOUTHERN CANADA. FORECAST CONFIDENCE LOW THU NIGHT
ONWARD.

TREND IN SHORTER RANGE IS TO CONTINUE TO SLOW PASSAGE OF COLD
FRONT MONDAY WITH FRONT STILL BISECTING CWA AT 00Z TUE. HAVE
CONTINUE SCATTERED/CHANCE POPS MAINLY SOUTH AND EAST GIVEN
AVAILABLE INSTABILITY. LITTLE DYNAMICS BESIDES FRONT TO SUPPORT
GOING ANY HIGHER WITH POPS.

CONSISTENCY SEEN IN MODELS TO PUSH FRONT AND PCPN MAINLY SOUTH OF
CWA AS HIGH PRESSURE AND DRIER AIR MASS MOVES IN OVER NORTHERN WI
TUE INTO THU. CONCERN THIS PERIOD ON TEMPS. DRIER AIR...SUN AND
LOW LEVEL TEMPS AT OR SLIGHTLY BELOW NORMAL SHOULD SUPPORT TEMPS IN
THE LOWER TO MIDDLE 70S. WILL HAVE EAST FLOW OFF LAKE THOUGH LAKE
SURFACE TEMPS NOW IN MID TO UPPER 60S SO HAVE CONFINED COOLING TO
CLOSER TO THE COAST. HAVE BUMPED MAX TEMPS UP A BIT MID WEEK.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1148 AM CDT SUN AUG 24 2014

POCKET OF IFR CIGS AND VSBYS OVER NORTH-CENTRAL
WISCONSIN WILL RETURN TO MVFR THIS AFTERNOON AS DAYTIME HEATING
MIXES OUT SOME OF THE LOW LEVEL MOISTURE.  THIS WILL BE A SLOW
PROCESS MOST AREAS HAVE A CHANCE TO SEE VFR LATE THIS AFTERNOON INTO
EARLY THIS EVENING. THEN A WEAK FRONT WILL SLOW ITS FORWARD
PROGRESS AS IT MOVES INTO THE REGION TONIGHT AND HANGS AROUND ON
MONDAY.  THE FRONT IS EXPECTED TO BRING A BROKEN LINE OF SHOWERS AND
THUNDERSTORMS TO CENTRAL AND NORTH-CENTRAL WISCONSIN AFTER
MIDNIGHT...BUT THE LINE SHOULD BE WEAKENING AS IT MOVES EAST INTO
NORTHEAST WISCONSIN.  AS A RESULT...LEFT ANY MENTION OF
PRECIPITATION OUT OF THE FOX VALLEY AND LAKESHORE TAF SITES.  AREAS
OF LOW CLOUDS AND FOG WILL ALSO LIKELY REDEVELOP LATER TONIGHT.
BETTER FLYING CONDITIONS WILL RETURN ON MONDAY.
&&

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

$$

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






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