Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 270337
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1037 PM CDT TUE AUG 26 2014

UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE

.UPDATE...
ISSUED AT 858 PM CDT TUE AUG 26 2014

INCREASED RAIN CHANCES ACROSS THE NORTH TONIGHT AS POTENT SHORTWAVE
SWINGS EAST ACROSS THE UPPER GREAT LAKES. KMPX RADAR INDICATED
25 TO 35 DBZ AROUND 4500 FEET...TO SUPPORT RAIN REACHING THE
GROUND. A FEW LOCATIONS COULD UP TO A TENTH OF AN INCH OF RAIN...
ALTHOUGH MOST SPOTS SHOULD SEE FIVE HUNDREDTHS OF AN INCH OR LESS.
GRID/ZONE UPDATE JUST SENT. WILL MAKE ANOTHER GRID ADJUSTMENT TO
TEMPERATURES AFTER 9 PM OBSERVATIONS ARRIVE.
&&

.SHORT TERM...TONIGHT AND WEDNESDAY
ISSUED AT 309 PM CDT TUE AUG 26 2014

UPPER LEVEL FLOW STARTS OUT PRETTY MUCH ZONAL AT THE START OF THE
PERIOD AND THEN BEGINS TO AMPLIFY LATER TONIGHT. THE CONCERN FOR
TONIGHT IS A SHORT WAVE THAT WILL PASS ACROSS NORTHERN
WISCONSIN. MOISTURE IS LIMITED AND HIGH PRESSURE WILL BE THE MAIN
SURFACE FEATURE. HOWEVER...THE 12Z GFS AND 12Z NAM HAD QPF IN
NORTHERN WISCONSIN AND THE 12Z ECMWF HAD QPF THAT WAS EVEN MORE
WIDESPREAD. HAVE A SLIGHT CHANCE FOR SHOWERS AND A CHANCE FOR
SPRINKLES MENTIONED LATE TONIGHT IN THE NORTH TO ACCOUNT FOR THIS.

DEW POINTS IN THE 40S AND 50S...ALONG WITH MOSTLY CLEAR/PARTLY
CLOUDY SKIES DURING THE EVENING SHOULD ALLOW TEMPERATURES TO FALL
TO NEAR NORMAL LOWS FOR THIS TIME OF YEAR. LOOKS LIKE SLIGHTLY
BELOW NORMAL TEMPERATURES ON WEDNESDAY.

.LONG TERM...WEDNESDAY NIGHT THROUGH TUESDAY
ISSUED AT 309 PM CDT TUE AUG 26 2014

MEAN FLOW THRU THIS PERIOD TO BE PROGRESSIVE WITH WESTERLIES LYING ALONG
U.S./CANADIAN BORDER. A WEAK CUT-OFF UPPER TROF DRIFTING EAST OUT
OF THE ROCKIES WILL BE EVENTUALLY BROUGHT EAST BY SUCCESSIVE SHORT
WAVES MOVING THROUGH WESTERLIES. PCPN CHANCES MAIN ISSUE THIS
PERIOD WITH MODELS POINTING AT A RATHER WET PERIOD LATER THU INTO
SATURDAY. (SEE HYDROLOGY SECTION) A SHORT BREAK EXPECTED SUNDAY...BEFORE
STRONGER SYSTEM MOVES THROUGH ON MONDAY.

SURFACE HI SHIFTS EAST OF THE AREA WED NIGHT LEADING TO INCREASING MOISTURE
WITH FRONT SLOWLY RETURNING NORTH. PW VALUES TO AGAIN BE UP IN
THE 1.5-2.0" RANGE. HAVE TRENDED TOWARD EC`S MORE CONSISTENT...
SOUTHERLY TRENDS REGARDING PCPN COVERAGE. HIGHEST POPS OVER CENTRAL
AND EAST CENTRAL CWA. DIFFERENCES THIS PERIOD VERSUS EARLIER THIS
WEEK...LESS SURFACE BASED INSTABILITY BUT BETTER DYNAMICS WITH
FRONT/WAVE LIFTING NORTH INTO SOUTHERN CWA AND SUPPORT OF JET ALOFT.
TEMPERATURES TO BE TRICKY DEPENDENT ON CLOUDS AND PCPN...THUS MADE LITTLE
CHANGE TO PREVIOUS FORECAST PACKAGE.
&&

.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 1032 PM CDT TUE AUG 26 2014

POTENT SHORTWAVE MOVING ACROSS THE UPPER GREAT LAKES OVERNIGHT.
REGIONAL RADARS INDICATED SCATTERED SHOWERS ACROSS CENTRAL AND
NORTH CENTRAL MINNESOTA INTO NORTHWEST WISCONSIN. ADDED SHOWERS
TO THE 06Z KRHI TAF. MAY NEED TO THROW IN SOME SPRINKLES TO
KAUW/KCWA/KGRB TAF SITES. WILL MAKE A LAST MINUTE DECISION ON THE
SPRINKLES FOR THESE SITES. SHORTWAVE WILL MOVE AWAY FROM THE
AREA WEDNESDAY MORNING. WIND FORECAST STILL PROBLEMATIC ON
WEDNESDAY DUE TO THE LIGHT NATURE OF THE WIND SPEEDS AND
DIFFERENCES IN THE MET/MAV GUIDANCE. LIGHT AND VARIABLE WINDS
SHOULD TURN TO THE EAST/SOUTHEAST WEDNESDAY NIGHT.

&&

.HYDROLOGY...
ISSUED AT 309 PM CDT TUE AUG 26 2014

PWATS WILL BE ON THE INCREASE THURSDAY REACHING 1.5
TO 2.0 INCHES OVER WISCONSIN. SIG SOUTHERLY LOW LEVEL FLOW OVER
WARM FRONT LIFTING NORTH THURSDAY WILL BRING A POTENTIAL OF HEAVY
RAIN TO CENTRAL WI THU AFTERNOON. SURFACE WAVE AND WARM FRONT EXPECTED TO
LIFT NORTH INTO PARTS OF CENTRAL AND EAST CENTRAL WI LATER THU
NIGHT INTO FRI CONTINUING HEAVY RAIN POTENTIAL FOR CENTRAL AND
EAST CENTRAL WI. MODELS SUGGEST RRQ REGION OF THE UPPER JET MAY
ADD TO THE SUPPORT FOR HEAVY RAIN EVENT THIS PERIOD. RIVER LEVELS ARE
NEAR NORMAL AND CAN HANDLE A FEW INCHES OF RAIN...FLOODING
CONCERNS WOULD PRIMARILY BE SMALL STREAM AND URBAN AREAS AT THIS
TIME.
&&

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

$$

UPDATE.........ECKBERG
SHORT TERM.....MG
LONG TERM......TE
AVIATION.......ECKBERG
HYDROLOGY......TE





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