Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 250809
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
309 AM CDT MON MAY 25 2015

FORECAST DISCUSSION FOR ROUTINE MORNING FORECAST ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND TUESDAY
ISSUED AT 309 AM CDT MON MAY 25 2015

LOW PRESSURE OVER THE IOWA/MINNESOTA BORDER WILL LIFT NORTHEAST
THROUGH NORTHERN WISCONSIN EARLY THIS AFTERNOON...CONTINUING
NORTHEAST JUST SOUTH OF JAMES BAY LATE TONIGHT. AS THE LOW LIFTS
NORTH A WARM FRONT WILL LIFT NORTH...PLACING NORTHEAST WISCONSIN
IN THE WARM SECTOR OF THIS SYSTEM. IN ADDITION A PRONOUNCED DRY
SLOT...EVIDENT ON WATER VAPOR IMAGERY...WILL LIFT NORTHEAST WITH
THE LOW OVER THE EASTERN PORTION OF THE CWA THIS AFTERNOON. THE
DRY SLOT SHOULD ALLOW SOME FILTERED SUNSHINE ACROSS THE EASTERN
CWA THIS AFTERNOON...ALLOWING HIGHS TO SOAR TO AROUND 80 DEGREES.
A TIGHT PRESSURE GRADIENT AND STRONG 40 KNOT LOW LEVEL JET WILL
CAUSE WIND GUSTS TO INCREASE THIS AFTERNOON AS THE AFOREMENTIONED
FILTERED SUNSHINE IN THE WARM SECTOR ALLOWS SOME OF THESE WINDS TO
MIX DOWN TO THE SURFACE...WITH WIND GUSTS AS HIGH AS 40 MPH
POSSIBLE AT TIMES.

SEVERE POTENTIAL THIS AFTERNOON AND EARLY THIS EVENING WILL BE
HIGHLY DEPENDENT ON THE AMOUNT OF INSTABILITY THAT CAN BUILD FROM
INCOMING SOLAR RADIATION AS WELL AS THE DEPTH OF THE INSTABILITY.
WHILE MODEL SOUNDINGS SHOW CLOSE TO 1000 J/KG OF CAPE ACROSS THE
EASTERN CWA THIS AFTERNOON...THERE IS A LAYER OF WARM AIR AROUND
650 MB WHICH COULD INHIBIT VERTICAL GROWTH OF CUMULONIMBUS CLOUDS.
THAT BEING SAID THERE ARE FAIRLY HIGH WINDS WITH THE
AFOREMENTIONED LOW LEVEL JET SO GETTING DAMAGING WINDS TO THE
SURFACE MAY NOT BE THAT DIFFICULT OF A TASK. GIVEN ALL OF THE
WHAT IFS DURING THIS PERIOD A MARGINAL RISK ACROSS THE SOUTHERN
CWA CONTINUES TO BE REASONABLE PER THE SPC DAY 1 OUTLOOK.

AS THE LOW LIFTS NORTH INTO CANADA THE COLD FRONT ASSOCIATED WITH
THIS SYSTEM WILL STALL OUT OVER THE WESTERN GREAT LAKES. WITHOUT
MUCH IN THE WAY OF MID LEVEL SUPPORT RAIN CHANCES WILL DROP OFF
LATER TONIGHT. BY TUESDAY THE MID LEVEL TROUGH...CURRENTLY SHOWN
ON WATER VAPOR OVER NORTHERN COLORADO...WILL TRACK NORTHEAST ALONG
THE FRONTAL BOUNDARY DRAPED ACROSS THE MIDWEST AND BRING ANOTHER
ROUND OF SHOWERS TO NORTHEAST WISCONSIN. DESPITE THE CURRENT
STRENGTH OF THIS TROUGH...IT IS EXPECTED TO WEAKEN AS IT EJECTS
OUT OF THE PLAINS AND HEADS NORTHEAST TOWARDS THE WESTERN GREAT
LAKES. THE WEAKENING SYSTEM...WHEN COMBINED WITH FAIRLY MODEST
INSTABILITY VALUES...MEANS THUNDER CHANCES ARE A BIT TENUOUS FOR
TUESDAY DESPITE DAYTIME HIGHS SOARING INTO THE 70S. GIVEN THE
MODEST INSTABILITY AND DYNAMICS WILL NOT COMPLETELY REMOVE
THUNDER...BUT WILL BACK OFF A BIT FROM THE PREVIOUS FORECAST AND
ONLY INCLUDE A CHANCE DURING THE AFTERNOON HOURS.

.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY
ISSUED AT 309 AM CDT MON MAY 25 2015

MODELS CONTINUED TO KEEP SOUTHWEST UPPER LEVEL FLOW ACROSS THE
AREA UNTIL A TROUGH AXIS PASSES THROUGH WISCONSIN ON WEDNESDAY.
SHORT WAVES IN THE SOUTHWEST FLOW WILL BRING CHANCES FOR SHOWERS
AND THUNDERSTORMS TO THE AREA TUESDAY NIGHT INTO WEDNESDAY. A
SURFACE RIDGE AND LOW AMPLITUDE UPPER RIDGE SHOULD KEEP THE AREA
DRY FOR WEDNESDAY NIGHT AND THURSDAY. CHANCES FOR SHOWERS AND
STORMS RETURN AHEAD OF AN APPROACHING SURFACE COLD FRONT AND THE
NEXT UPPER TROUGH. THE FRONT SHOULD PUSH THROUGH THE AREA ON
FRIDAY/FRIDAY NIGHT. DO NOT EXPECT THUNDERSTORMS ONCE THE FRONT
HAS PASSED...BUT THERE IS STILL A CHANCE FOR SHOWERS ON
SATURDAY...MAINLY IN CENTRAL AND EAST CENTRAL WISCONSIN. AFTER
THAT...IT LOOKS LIKE ONLY A SLIGHT CHANCE FOR SHOWERS AT MOST.

TEMPERATURES FOR THE REMAINDER OF THE WORK WEEK SHOULD BE WELL
ABOVE NORMAL AT MOST LOCATIONS...BUT COLDER AIR BEHIND THE
DEPARTING COLD FRONT WILL BRING BELOW NORMAL HIGHS BACK FOR THE
WEEKEND.
&&

.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 1135 PM CDT SUN MAY 24 2015

SHOWERS WILL CONTINUE TO LIFT NORTH ACROSS THE REGION
OVERNIGHT...WITH IFR CONDITIONS EXPECTED AT MOST LOCATIONS DUE TO
THE RAIN AND PERSISTENT EAST TO SOUTHEAST FLOW OFF LAKE MICHIGAN.
THERE MAY BE A BRIEF BREAK IN THE PCPN IN SOME AREAS LATE TONIGHT
INTO EARLY MONDAY BEFORE AN UPPER LEVEL DISTURBANCE AND WARM FRONT
BRING MORE SHOWERS AND ISOLD TSTMS TO THE REGION. A DRY SLOT IS
EXPECTED TO BRING AN END TO THE SHOWERS OVER THE SE HALF OF THE
FCST AREA IN THE AFTERNOON. CONDITIONS SHOULD IMPROVE TO
MVFR/LOCAL VFR WITHIN THE DRY SLOT...AND SW WINDS WILL GUST TO
AROUND 30 KTS AT THE GRB/ATW/MTW TAF SITES. SCT TSTMS MAY DEVELOP
NEAR A COLD FRONT IN CENTRAL WI BY LATE AFTERNOON OR EARLY EVG...
AND MAY TRACK INTO EC WI DURING THE EVG...BUT CONFIDENCE IS TOO
LOW TO MENTION AT THE SOUTHERN TAF SITES RIGHT NOW.

WILL KEEP LLWS IN THE FCST OVERNIGHT...AS WINDS ALOFT VEER FROM
SE TO SW AND INCREASE TO 35 TO 40 KTS. CONDITIONS SHOULD IMPROVE
BY 12Z/MON.
&&

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

$$

SHORT TERM.....KURIMSKI
LONG TERM......MG
AVIATION.......KIECKBUSCH


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