Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 180926
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
326 AM CST THU DEC 18 2014

FORECAST DISCUSSION FOR ROUTINE MORNING FORECAST ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND FRIDAY
ISSUED AT 325 AM CST THU DEC 18 2014

CLOUD TRENDS AND TEMPERATURES ARE THE MAIN FCST CONCERNS.

A WEAKENING SFC TROF WAS SITUATED OVER THE NORTHERN HALF OF WI
EARLY THIS MORNING. CONVERGENCE ASSOCIATED WITH THIS TROF WAS
COMBINING WITH A SHALLOW LAYER OF MOISTURE TO PRODUCE WIDESPREAD
STRATUS OVER THE ENTIRE FORECAST AREA. SATELLITE SHOWED THAT
CLEARING WAS PROGRESSING SWWD ACROSS THE UPPER PENINSULA.

CONCENSUS OF 925 MB RELATIVE HUMIDITY FCSTS SUGGEST THAT DRIER
AIR WILL GRADUALLY PUSH SWWD INTO THE FCST AREA TODAY AND
TONIGHT...BUT MAY NOT QUITE MAKE IT INTO CENTRAL WI. IN
ADDITION...MODELS SHOW THE SFC TROF WEAKENING DURING THE DAY...
WITH A SFC HIGH GRADUALLY EDGING INTO THE REGION FROM THE
NW LATER TODAY AND TONIGHT. THE LOSS OF SFC CONVERGENCE...
DRY AIR ADVECTION AND SOME DAYTIME MIXING SHOULD BRING AT LEAST
PARTIAL CLEARING TO ABOUT THE NE TWO-THIRDS OF THE FCST AREA
BY EVENING. MOSTLY CLOUDY SKIES MAY REMAIN OVER CENTRAL WI
TODAY AND TONIGHT...THEN START EDGING BACK TO THE EAST LATE
TONIGHT INTO FRIDAY.

USED A BLEND OF THE PREVIOUS FCST AND THE BETTER PERFORMING
GUIDANCE SETS FOR TEMPERATURES THE NEXT COUPLE DAYS. HIGH
TEMPERATURES SHOULD BE MAINLY IN THE MIDDLE 20S TO LOWER 30S.
LOWS TONIGHT SHOULD BE IN THE TEENS...EXCEPT SINGLE DIGITS
OVER FAR NORTHERN WI...WHERE A FRESH SNOW COVER RESIDES.

.LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY
ISSUED AT 325 AM CST THU DEC 18 2014

THE LATEST GFS AND ECMWF ENSEMBLE MEANS CONTINUE TO INDICATE A
PATTERN CHANGE EARLY NEXT WEEK AS SHORTWAVE ENERGY AMPLIFIES OVER
THE CENTER OF THE COUNTRY DURING THE MONDAY THROUGH WEDNESDAY TIME PERIOD.
THIS BUCKLING OF THE UPPER FLOW THEN RESULTS IN A STRONG CYCLONE
LIFTING NORTH ACROSS THE GREAT LAKES DURING THE MIDDLE OF NEXT
WEEK.  THOUGH THE DETAILS ARE FAR FROM CERTAIN...ANYONE WITH TRAVEL
PLANS NEXT WEEK SHOULD STAY TUNED TO THE LATEST FORECASTS.  IN ANY
EVENT...WILL RELY ON THE ENSEMBLE MEANS LATE IN THE PERIOD...BUT A
BLEND OF THE GFS AND ECMWF WILL WORK THROUGH 00Z TUE.

FRIDAY NIGHT THROUGH SATURDAY NIGHT...AS PIECES OF WEAK SHORTWAVE
ENERGY MOVES ACROSS THE NORTHERN MISSISSIPPI VALLEY FRIDAY
NIGHT...HIGH PRESSURE WILL EXIT INTO EASTERN CANADA.  WILL SEE
CLOUDS INCREASE FROM WEST TO EAST THROUGH THE NIGHT THOUGH A DRY
WEDGE IN THE MID-LEVELS SHOULD PREVENT PRECIP.  THE SHORTWAVES WILL
MOVE ACROSS WISCONSIN ON SATURDAY WHICH SHOULD KEEP SKIES ON THE
MOSTLY CLOUDY SIDE...BUT SOUNDINGS DO NOT LOOK QUITE AS SATURATED AS
LAST NIGHT. WILL MAINTAIN A DRY FORECAST.  CONTINUED CLOUDY ON
SATURDAY NIGHT WITH AMPLE LOW LEVEL MOISTURE AROUND FROM SOUTHERLY
FLOW.  WILL RAISE LOW TEMPS A DEGREE OR TWO...BUT LITTLE CHANGES
WERE MADE ELSEWHERE.

REST OF THE FORECAST...SOUTHERLY FLOW AHEAD OF AN AMPLIFYING TROUGH
WILL KEEP CLOUDS AROUND ON SUNDAY...AND PROGGED SOUNDINGS LOOK
SATURATED...ESPECIALLY OVER THE NORTHWEST HALF OF THE FORECAST
AREA.  WILL EXPAND THE SMALL CHANCES OF SNOW.  WEAK LIFT WILL
CONTINUE SUNDAY NIGHT INTO MONDAY WITH LOW PRESSURE TAKING SHAPE TO
THE WEST.  ENOUGH WARM AIR COULD BE PRESENT FOR A MIX OF RAIN AND
SNOW OVER CENTRAL AND NORTHEAST WISCONSIN.  ANY PRECIP SHOULD BE
LIGHT OVER THIS PERIOD...BUT SHOULD BECOME MORE WIDESPREAD MONDAY
NIGHT INTO TUESDAY NIGHT AS THE DEEPENING TROUGH MOVES OVERHEAD.
THEN AS INTENSIFYING LOW PRESSURE MOVES NORTHWARD ON
WEDNESDAY...COLDER AIR WILL BE WRAPPING AROUND THE LOW WHICH COULD
MAKE FOR WINTRY TRAVEL ACROSS THE REGION DEPENDING ON THE TRACK OF
THE LOW.  GUSTY WINDS WILL ALSO CAUSE ISSUES WITH ANY WINTRY
PRECIP.
&&

.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 1145 PM CST WED DEC 17 2014

MODELS WERE SHOWING DRIER AIR MOVING INTO THE AREA FROM THE NORTH
TONIGHT AND THURSDAY...BUT CIGS WERE MVFR AND IFR ACROSS THE
FORECAST AREA AT 0530Z. VSBYS WERE VFR. HAVE OPTED FOR A MORE
PESSIMISTIC APPROACH TO CIGS IN THE TAFS THROUGH AT LEAST THE
FIRST PART OF THURSDAY MORNING. HAVE MAINLY KEPT MVFR
CIGS...EXCEPT PREVAILING IFR AT RHI EARLY. THE NORTH SHOULD BE THE
FIRST PART OF THE AREA TO SCATTER OUT BUT WOULD NOT EXPECT THAT
TO BE UNTIL THE DAYLIGHT HOURS...WITH THE REST OF THE AREA
STARTING TO SCATTER OUT AROUND MIDDAY. THINK SKIES SHOULD FINALLY
CLEAR BY 00Z FRIDAY. CONFIDENCE LEVEL IN CIG FORECAST IS NOT VERY
HIGH WITH MODEL TIME/HEIGHT SECTIONS SHOWING HIGH RH VALUES NEAR
THE SURFACE THROUGHOUT THE TAF VALID PERIOD.
&&

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

$$

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





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