Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 202014
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
314 PM CDT MON OCT 20 2014

FORECAST DISCUSSION FOR ROUTINE AFTERNOON FORECAST ISSUANCE

.SHORT TERM...TONIGHT AND TUESDAY
ISSUED AT 314 PM CDT MON OCT 20 2014

CLOUD TRENDS AND THEIR IMPACT ON TEMPERATURES ARE THE PRIMARY
CONCERNS THROUGH TUESDAY.

CYCLONIC FLOW OF COLDER AIR BROUGHT PLENTY OF CLOUDS INTO THE
FORECAST AREA TODAY...AND THERE WAS SOME LIGHT RAIN AND DRIZZLE
ACROSS PARTS OF NORTH CENTRAL WISCONSIN. THE PRECIPITATION IS IN
THE AREA WHERE SOME OF THE 12Z MODELS FROM SUNDAY WERE SHOWING QPF.
A LOOK AT THE 925MB TEMPERATURES FROM 12Z SOUNDINGS AT
KINL...4C...AND CWPL...-2C...AND SURFACE TEMPERATURES OF LAKE
SUPERIOR...AROUND 9C...SHOWED LAKE SURFACE TO 925MB DELTA T VALUES
OF 5 TO 11C. SO LAPSE RATES WERE STEEP ENOUGH FOR LAKE EFFECT
PRECIPITATION...BUT INVERSION HEIGHTS WERE TOO LOW FOR ANYTHING
SIGNIFICANT. 12Z MODEL RUNS HAD QPF NEAR THE UPPER MICHIGAN
BORDER TODAY...BUT NOTHING AFTER 00Z TUESDAY SO NO POPS IN THE
FORECAST TONIGHT.

BUFKIT TIME/HEIGHT PLOTS FROM THE 12Z NAM/12Z GFS/09Z SREF HAD
PLENTY OF MOISTURE BELOW ABOUT 5000FT FOR MUCH THE PERIOD. IT
APPEARS THAT CLOUDS SHOULD CLEAR OUT TUESDAY AFTERNOON IN MOST
LOCATIONS AS THE SURFACE HIGH AND AN APPROACHING MID LEVEL RIDGE
BECOME THE MAIN INFLUENCE ON OUR WEATHER. THE CANADIAN CLOUD FORECAST
FROM THE GEM-REG HAD CLOUDS STARTING TO CLEAR OUT OF MOST OF THE
FORECAST AREA...STARTING IN CENTRAL WISCONSIN THIS EVENING. WINDS
AT 925MB ARE FORECAST TO BECOME MORE NORTHEAST OVERNIGHT INTO
TUESDAY...SO THE CLOUDS THAT THE CANADIAN HAS MOVING IN FROM THE
EAST MAKE SENSE.

HAVE THE CLEARING MAINLY AFTER 06Z TUESDAY BUT THINK THERE WILL
BE ENOUGH WIND TO KEEP TEMPERATURES FROM TANKING. CLOUDS EXPECTED
TO BE MAINLY IN THE EAST ON TUESDAY DURING THE MORNING OTHERWISE
THERE SHOULD BE PLENTY OF SUNSHINE. AM A LITTLE CONCERNED THAT
THERE COULD BE SOME LAKE EFFECT RAIN OR DRIZZLE IN THE EAST ALONG
WITH THE CLOUDS BUT HAVE LEFT THAT OUT FOR NOW. THE COLDER AIR
MASS WILL RESULT IN LOWER HIGH TEMPERATURES THAN TODAY.

.LONG TERM...TUESDAY NIGHT THROUGH MONDAY
ISSUED AT 314 PM CDT MON OCT 20 2014

PCPN CHANCES FROM LATE WEDS NGT THROUGH THU EVG...AND WARMER
TEMPERATURES FOR THE REST OF THE EXTENDED PERIOD...ARE THE MAIN
FCST CONCERNS.

HIGH PRESSURE...LIGHT WINDS...CLEAR SKIES AND A VERY DRY AIR
MASS (PWATS AT OR BLO 0.25 INCH) WILL LEAD TO COOL CONDITIONS
ON TUESDAY NIGHT. HAVE LOWERED MIN TEMPS SEVERAL DEGREES...WITH
MOST PLACES EXPECTED TO DROP INTO THE 20S AND LOWER 30S. 1000-850
MB AVERAGE MIXING RATIOS OF 2-2.5 G/KG SUGGEST THAT A FEW OF THE
TYPICAL COLD SPOTS COULD GET INTO THE UPPER TEENS...BUT DIDN`T
GO QUITE THAT COLD. ON WEDNESDAY...SUNNY CONDITIONS SHOULD
ALLOW AFTERNOON HIGHS TO REACH NORMAL READINGS IN THE LOWER TO
MIDDLE 50S.

AS THE SFC HIGH SHIFTS EAST ON WEDS NGT AND THURSDAY...SOUTHERLY
WINDS WILL GRADUALLY BRING A MORE MOIST AIR MASS INTO WI...WITH
PWATS RISING TO 0.75 TO 1.00 INCH ON THU/THU NGT. AN UPPER LEVEL
TROF WILL MOVE INTO WSTRN MN LATE WED NGT...THEN ACROSS GRB CWA
LATE THURSDAY AFTERNOON AND EVG. WILL KEEP MOST OF THE PCPN WEST
OF THE FORECAST WED NGT...THEN SPREAD CHC POPS FROM WEST TO EAST
THURSDAY AND THURSDAY EVG. SUSPECT THAT MOST LOCATIONS WILL
RECEIVE LESS THAN A TENTH OF AN INCH OF RAIN FROM THIS SYSTEM.

ZONAL FLOW ALOFT IS EXPECT FROM FRIDAY THROUGH SUNDAY...WITH
DRY AND MILD CONDITIONS ANTICIPATED THROUGH THE PERIOD. ABOVE
TO MUCH ABOVE NORMAL TEMPERATURES LOOK LIKE A GOOD BET...SO
HAVE RAISED MAX TEMPS 2-3 DEGREES ABOVE THE PREVIOUS FCST AND
THE EXTENDED MODEL BLEND. ADDITIONAL UPWARD ADJUSTMENTS MAY
BE NEEDED...WITH POTENTIAL FOR OUR WARM SPOTS IN C WI GETTING
TO AROUND 70 DEGREES ON SUN/MON.

AN UPPER TROF WILL MOVE INTO THE PLAINS SUNDAY NIGHT AND
MONDAY...CAUSING A SFC LOW TO DEVELOP AND TRACK NE TOWARD
LAKE SUPERIOR. THIS SYSTEM MAY BRING A CHANCE OF SHOWERS AND
ISOLD TSTMS TO OUR NW COUNTIES SUNDAY NIGHT...AND TO THE ENTIRE
FORECAST AREA ON MONDAY/MONDAY NIGHT. CONTINUED MILD CONDITIONS
ARE EXPECTED AHEAD OF THE APPROACHING COLD FRONT.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1259 PM CDT MON OCT 20 2014

CLOUDS CONTINUED TO SPREAD ACROSS THE AREA DURING THE
MORNING...LEAVING MOST LOCATIONS WITH BKN TO OVC CONDITIONS BY
MIDDAY. CIGS WERE MOSTLY MVFR IN CENTRAL AND NORTH CENTRAL
WISCONSIN. THERE WERE ISOLATED IFR CIGS IN FAR NORTH CENTRAL
WISCONSIN AND THERE HAS BEEN SOME LIGHT RAIN AND/OR DRIZZLE
THERE...WHICH SHOULD END BY SUNSET. VFR CIGS PREVAILED IN THE
EAST WHERE DOWN SLOPE KEPT CLOUD BASES ABOVE 3000FT. CIGS OVER
DOOR COUNTY WERE MVFR DUE TO BAY EFFECTS.

THE CLOUD FORECAST WILL BE TRICKY DURING THIS TAF VALID PERIOD.
SURFACE HIGH PRESSURE WILL BE MAKING ITS WAY INTO THE REGION AS A
MID LEVEL RIDGE APPROACHES FROM THE WEST. AS LOW LEVEL WINDS
BECOME MORE NORTH THAN NORTHWEST ANY RAIN OR DRIZZLE WILL COME TO
AN END. CLOUDS BASES SHOULD BEGIN TO RISE BEFORE CONDITIONS BECOME
SCT LATE TONIGHT/EARLY TUESDAY. CANADIAN CLOUD FORECAST OFF THE
GEM-REG HAD CLOUDS STARTING TO BREAK UP IN CENTRAL...AND PARTS OF
EAST CENTRAL...WISCONSIN THIS EVENING. CLOUDS OVER LAKE MICHIGAN
THEN MOVE INLAND EARLY IN THE MORNING AS CLOUDS ACROSS THE REST OF
THE AREA DISSIPATE...WHICH MAKES SENSE BASED ON 925MB WIND
FORECASTS. EXPECT THESE CLOUDS TO BRING MVFR CIGS. TIME HEIGHT
PLOTS FORM 12Z NAM/09Z SREF/12Z GFS ALL INDICATED DRYING AT LOW
LEVELS...SO LOOKS LIKE CLOUDS SHOULD BE BREAKING UP ACROSS MOST OF
THE AREA AROUND MIDDAY.
&&

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

$$

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





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