Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 260337
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1037 PM CDT FRI JUL 25 2014

UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE

.SHORT TERM...TONIGHT AND SATURDAY
ISSUED AT 227 PM CDT FRI JUL 25 2014

LATEST RAP ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW HIGH PRESSURE
LOCATED OVER THE EASTERN U.S. AND A TROUGH OF LOW PRESSURE OVER THE
NORTHERN PLAINS.  BETWEEN THESE FEATURES...WARM AIR AND MOISTURE
ADVECTION IS ONGOING IN THE LOW AND MID-LEVELS.  THIS WEAK FORCING
COMBINED WITH ONE SHORTWAVE OVER EASTERN WISCONSIN AND ANOTHER OVER
NORTH-CENTRAL WISCONSIN HAS CONTRIBUTED TO SPOTTY SHOWER ACTIVITY
OVER THE COURSE OF THE DAY.  SHOWERS ARE MAINLY CONFINED TO N-C
WISCONSIN CURRENTLY AS SHOWERS WITH THE EASTERN WISCONSIN SHORTWAVE
HAVE PUSHED SOUTH OF THE AREA.  LOOKING UPSTREAM...SCT TO BKN STRATO
CU EXISTS ALL THE WAY INTO THE EASTERN DAKOTAS WHERE DEWPOINTS ARE
PUSHING INTO THE MIDDLE AND UPPER 60S.  AS THIS MOISTURE RICH AIR
SPREADS EAST...SMALL SHOWER CHANCES AND CLOUDS ARE THE MAIN FORECAST
CONCERNS.

TONIGHT...AS ONE SHORTWAVE EXITS SOUTHEAST WISCONSIN EARLY THIS
EVENING...ANOTHER WAVE WILL BE DIVING SOUTHEAST OVER NORTHEAST
WISCONSIN.  UNTIL THIS WAVE EXITS...WILL LEAVE AT LEAST AN ISOLATED
MENTION OF SHOWERS OVER N-C AND NORTHEAST WISCONSIN UNTIL LATE IN
THE EVENING.  THEREAFTER...THOUGH WEAK THETAE ADVECTION WILL STILL
BE OCCURRING IN THE LOW LEVELS...MODELS SHOW MID-LEVEL MOISTURE
DEPARTING BEHIND THE SHORTWAVE AND A DECENT CAP DEVELOPING AROUND
700MB.  SO THINK SMALL PRECIP CHANCES WILL END BY LATE IN THE
EVENING...AND THEN GO DRY THE REST OF THE NIGHT.  SURFACE DEWPOINTS
WILL BE INCREASING HOWEVER...AND WITH NOCTURNAL COOLING...LOW
STRATUS SHOULD REMAIN RELATIVELY WIDESPREAD AND LOWER THROUGH THE
NIGHT.  THIS WILL MAKE FOR A WARMER AND MUGGIER NIGHT THAN THE PAST
FEW WITH LOWS IN THE LOW TO MID 60S.

SATURDAY...AREAS OF STRATUS WILL LINGER INTO THE MORNING HOURS.
WITH DAYTIME HEATING...MIXING SHOULD BE ABLE TO TAP INTO THE DRY AIR
ABOVE THE INVERSION AND HELP TO DIMINISH THE CLOUDS FROM WEST TO
EAST OVER THE COURSE OF THE DAY.  LOW LEVEL TEMPS ARE PROJECTED TO
BE QUIET TOASTY TOMORROW AND HAVE RAISED HIGHS A DEGREE OR TWO IN
MOST AREAS.  HIGHS IN THE LOW TO MID 80S.

.LONG TERM...SATURDAY NIGHT THROUGH FRIDAY
ISSUED AT 227 PM CDT FRI JUL 25 2014

PCPN TRENDS FOR THE LATTER HALF OF THE WEEKEND...AND THE
POTENTIAL FOR SEVERE TSTMS ON SUNDAY AFTERNOON...WILL BE THE
MAIN FCST CHALLENGES.

MODELS ARE STILL TRYING TO FIND CONCENSUS ON THE TIMING OF THE
STRONG UPPER LEVEL TROF AND CANADIAN COLD FRONT ON SATURDAY NIGHT
AND SUNDAY. SLOWER IS USUALLY THE WAY TO GO WHEN DEALING WITH AN
UPPER LOW...SO HAVE LEANED TOWARD THE SLOWER ECMWF FOR THIS
SYSTEM. THIS WOULD SUGGEST A CHANCE OF TSTMS OVER THE NORTHWEST
THIRD OF GRB CWA AFTER MIDNIGHT SATURDAY NIGHT...THEN LIKELY POPS
SPREADING SE ACROSS THE FORECAST AREA ON SUNDAY. IF THE ECMWF
VERIFIES...ITS SLOWER MOVMT WOULD ALLOW FOR A LITTLE MORE HEATING
AND INSTABILITY IN ADVANCE OF THE SYSTEM...AND POTENTIALLY A
LITTLE GREATER THREAT OF SVR TSTMS OVER THE SE HALF OF THE
FORECAST AREA. MODIFIED FCST SOUNDINGS SUGGEST CAPE AROUND
1000-1500 J/KG...LI`S -3 TO -5...AND FAVORABLE WET BULB ZERO HGTS
OF 9.5-10K FT. DEEP LAYER SHEAR IS EXPECTED TO BE 25 TO 35 KTS
IN ADVANCE OF THE COLD FRONT AROUND MIDDAY...BUT SHOULD QUICKLY
WEAKEN AS THE UPPER TROF ARRIVES LATE IN THE DAY. ALTHOUGH A
SIGNIFICANT SVR WX EVENT IS NOT LIKELY DUE TO WIDESPREAD
CLOUDS/SHOWERS...WE CANNOT RULE OUT A FEW SVR TSTMS WITH LARGE
HAIL OVER PARTS OF NE/C/EC WI DURING THE AFTERNOON...SO WILL
CONTINUE TO MENTION THIS THREAT IN THE HWO.

THE EXTENDED FCST FOR THE UPCOMING WORK WEEK IS EXPECTED TO BE
AT OR A LITTLE COOLER THAN COOLER THAN NORMAL...WITH SCATTERED
SHOWERS AND TSTMS...MAINLY DURING THE AFTERNOONS AND EARLY
EVENINGS. A STRONG UPPER LEVEL RIDGE WILL BE SITUATED OVER THE
ROCKIES...WITH A LARGE UPPER TROF OVER THE EASTERN U.S. AND
EASTERN CANADA. ALTHOUGH S/W TROFS IN THE NW FLOW MAY GENERATE
SOME PCPN AT TIMES...IT APPEARS THAT MOST OF THE RAIN WILL BE
DIURNALLY-DRIVEN DUE TO DAYTIME HEATING/INSTABILITY.
&&

.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 1033 PM CDT FRI JUL 25 2014

SOME HOLES DEVELOPING IN THE OVERCAST OVER STATE. EXPECT WILL FILL
IN THROUGH THE NIGHT...THOUGH MAY LEAD TO BIT MORE FOG THAN
THOUGHT PREVIOUSLY. WILL STAY WITH MVFR VSBY GIVEN WIND AT THIS
TIME. LIGHT SHOWER ACTIVITY PASSING THROUGH FAR NORTH...THOUGH
EXPECT DRY CONDITIONS TO CONTINUE AT TAF SITES. RELATIVELY QUICK
IMPROVEMENT TO THE CIGS/VSBYS SHOULD OCCUR TOMORROW MORNING WITH
DAYTIME HEATING AND MIXING. &&

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

$$

SHORT TERM.....MPC
LONG TERM......KIECKBUSCH
AVIATION.......TE





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