Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 012028
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
328 PM CDT WED OCT 1 2014

FORECAST DISCUSSION FOR ROUTINE AFTERNOON FORECAST ISSUANCE

.SHORT TERM...TONIGHT AND THURSDAY
ISSUED AT 328 PM CDT WED OCT 1 2014

PRECIPITATION TIMING IS THE MAIN CONCERN DURING THIS PART OF THE
FORECAST.

RADAR TIME LAPSE INDICATED SHOWERS MOVING INTO CENTRAL WISCONSIN
THIS AFTERNOON AHEAD OF A MID LEVEL SHORT WAVE. THESE SHOWERS WERE
DECREASING IN COVERAGE AND INTENSITY AS THEY CONTINUED INTO NORTH
CENTRAL WISCONSIN. HRRR MODEL APPEARED TO DO A BETTER JOB OF
DEPICTING THIS THAN THE NAM/GFS/EC/SREF. STILL...HAVE LEFT SHOWERS
WITH A SLIGHT CHANCE OF THUNDER DUE TO THE APPROACHING COLD FRONT
AND SOME ELEVATED INSTABILITY THAT IS FORECAST FOR TONIGHT.
SURFACE FLOW BECOMES QUITE LIGHT TOWARD DAYBREAK...DUE TO A WEAK
SURFACE PRESSURE GRADIENT. HAVE AREAS OF FOG AROUND DAYBREAK DUE
TO THE COMBINATION OF MOISTURE...LIGHT OR CALM WINDS...AND 12Z MOS
GUIDANCE SHOWING LOW VISIBILITIES IN FOG.

THE BETTER CHANCE FOR SHOWERS AND THUNDERSTORMS ON THURSDAY SHOULD
BE IN THE AFTERNOON AS A LOW PRESSURE SYSTEM MOVES ALONG THE FRONT
TOWARD WISCONSIN. HAVE RAIN AND THUNDER CHANCES INCREASING DURING
THE AFTERNOON AS THE LOW APPROACHES.

THE WET CONDITIONS SHOULD KEEP LOW TEMPERATURES ABOVE NORMAL...AND
WARM ADVECTION AHEAD OF THE LOW PRESSURE SYSTEM WILL LEAD TO WARMER
THAN NORMAL CONDITIONS ON THURSDAY.

.LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY
ISSUED AT 328 PM CDT WED OCT 1 2014

PCPN TRENDS AND TEMPERATURES WILL BE THE MAIN FCST CONCERNS.

MODELS HAVE COME INTO GOOD AGREEMENT ON A SFC LOW LIFTING NNE ALONG
A STRONG COLD FRONT THURSDAY NIGHT...AND SPREADING WIDESPREAD SHOWERS
ACROSS THE FORECAST AREA. WILL CARRY CATEGORICAL POPS FOR THURSDAY
EVENING. A FEW TSTMS SHOULD BE EMBEDDED WITHIN THE SHOWER ACTIVITY
EAST OF THE FRONTAL BOUNDARY...OVER ROUGHLY THE SE HALF OF THE FCST
AREA. A DECREASE IN THE SHOWER ACTIVITY IS EXPECTED OVER CENTRAL AND
NORTH CENTRAL WI OVERNIGHT...AND THE REST OF THE AREA ON FRIDAY
MORNING...BUT SCT SHOWERS WILL CONTINUE INTO FRIDAY AFTERNOON AS
A DEEP UPPER TROF/UPPER LOW APPROACHES. IN THE WAKE OF THE COLD
FRONT...FRIDAY`S HIGH TEMPERATURES SHOULD BE 10-15 DEGREES COOLER
THAN ON THURSDAY.

THE UPPER TROF WILL SHIFT EAST ACROSS THE REGION ON FRIDAY NIGHT...
SO SCT SHOWERS WILL CONTINUE. SHOWERS WILL LIKELY BECOME LAKE-
ENHANCED OVER NC WI...WHERE COLD NW FLOW WILL MOVE ACROSS LAKE
SUPERIOR. WILL KEEP LIKELY POPS THERE. WILL CONTINUE THE MENTION
OF MIXED RAIN/SNOW SHOWERS OVER FAR NC WI LATE...AS H8 TEMPS DROP
TO -2 TO -4 C. A LIGHT MIX OF RAIN/SNOW SHOWERS SHOULD CONTINUE INTO
SATURDAY MORNING OVER NORTHERN WI...THEN TAPER OFF DURING THE
AFTERNOON AS WIND TRAJECTORIES BECOME WEST-NORTHWEST.

SATURDAY NIGHT THROUGH MONDAY NIGHT...THE WEATHER PATTERN WILL BE
DOMINATED BY AN UPPER LOW OVER ONTARIO..WITH SEVERAL S/W TROFS
ROTATING THROUGH WI. MOISTURE WILL BE LIMITED AND LLVL WINDS WILL
BE TOO WESTERLY FOR ANY SIGNIFICANT LAKE-EFFECT. WILL HAVE LOW
POPS (15-30 PERCENT) OVER MOST OF THE REGION DURING THIS PERIOD...
ALONG WITH CHILLY TEMPERATURES. IF PCPN OCCURS OVER NORTHERN WI...
A LIGHT MIX OF RAIN/SNOW WILL BE POSSIBLE DURING THE LATE
NIGHT/MORNING PERIODS.

EXPECT DRIER CONDITIONS TO PREVAIL INTO MIDWEEK...WITH A BIT OF
A WARMUP POSSIBLE. THIS IS A LOW CONFIDENCE FORECAST THOUGH...
AS MODELS SHOW A WIDE RANGE OF H8 TEMPS OVER THE WSTRN GREAT
LAKES. HAVE DISCOUNTED THE H8 TEMPS OF +16 TO +20 OFF THE
00Z ECMWF...AS THEY SEEM ANOMALOUS COMPARED TO THE ENSEMBLE
MEANS...AND UNLIKELY WITH A FAIRLY ZONAL FLOW PATTERN.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 115 PM CDT WED OCT 1 2014

CIGS WERE MAINLY MVFR ACROSS THE AREA WITH THE
EXCEPTION OF SOME CLEARING BETWEEN LOW CLOUDS OVER THE EASTERN
PART OF THE STATE AND THE CLOUDS APPROACHING FROM THE WEST. CIGS
MAY IMPROVE TO VFR AT TIMES THIS AFTERNOON...BUT PREVAILING SHOULD
BE MOSTLY MVFR. SHOWERS THAT MOVED INTO WESTERN WISCONSIN EARLIER
IN THE DAY WERE MAKING SLOW EASTWARD PROGRESS SO HAVE KEPT CENTRAL
AND NORTH CENTRAL WISCONSIN TAFS DRY UNTIL LATE AFTERNOON AND
LEFT THE EAST DRY UNTIL THIS EVENING. HRRR SUGGESTS A RELATIVELY
SHORT PERIOD OF RAIN WHILE THE NAM/GFS/SREF/EC ALL HANG ON TO
MEASURABLE PRECIPITATION FOR QUITE A BIT LONGER. RIGHT NOW THE
HRRR IS LOOKING BETTER BUT HAVE DECIDED TO ERR ON THE SIDE OF
CAUTION AND KEEP THE CHANCES FOR SHOWERS AROUND FOR LONGER. 12Z
MOS GUIDANCE FROM THE NAM AND GFS SHOWED LOW VSBYS IN FOG AROUND
12Z THURSDAY SO HAVE TEMPO GROUP WITH 1/2SM FG AT THE TAF SITES.
BASED ON WHAT I SAW FROM THIS MORNINGS OBSERVATIONS THERE DID NOT
APPEAR TO BE WIDESPREAD DENSE FOG...SO DID NOT USE IT AS THE
PREVAILING CONDITION. HAVE LEFT SHOWERS WITHOUT THUNDER TONIGHT
BUT WENT WITH A PROB30 FOR THUNDER ON THURSDAY AS THE ATMOSPHERE
BECOMES MORE UNSTABLE.
&&

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

$$

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





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