Area Forecast Discussion
Issued by NWS Green Bay, WI

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000
FXUS63 KGRB 192336
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
636 PM CDT SUN OCT 19 2014

UPDATED AVIATION PORTION FOR 00Z TAF ISSUANCE

.SHORT TERM...TONIGHT AND MONDAY
ISSUED AT 319 PM CDT SUN OCT 19 2014

SHOWERS/SPRINKLES DEVELOPED AHEAD OF A SURFACE BOUNDARY ASSOCIATED
WITH A LOW PRESSURE SYSTEM...IN NORTHWEST FLOW ALOFT...THAT SHOULD
PASS NORTHEAST OF WISCONSIN. THE 12Z GRB SOUNDING INDICATED PLENTY
OF DRY AIR BELOW 400MB AND PRECIPITABLE WATER OF ONLY 0.24
INCH...THOUGH KMPX..KINL AND CWPL SOUNDINGS LOOKED PRETTY
SATURATED WITH PW VALUES OF 0.7 TO 0.8 INCH. THE GRB RADAR SHOWED
AN AREA OF 20+ DBZ ECHOES MOVING THROUGH THE AREA BUT SURFACE
PLOTS INDICATED UNRESTRICTED VISIBILITIES WITH LIGHT RAIN.

THERE WAS ALREADY SOME CLEARING IN NORTHWEST WISCONSIN LATE THIS
AFTERNOON THOUGH BUFKIT TIME/HEIGHT PLOTS FROM NAM/SREF/GFS
APPEARED TO INDICATE CLOUDS HANGING AROUND THROUGH MONDAY...WITH
LOW LEVEL MOISTURE INCREASING SIGNIFICANTLY LATE THIS
AFTERNOON/EVENING.

A PRETTY STRONG SHORT WAVE WAS FORECAST TO PASS THROUGH WISCONSIN
BETWEEN 06Z AND 12Z BUT QPF WAS SHOWN WELL AHEAD OF THE TROUGH.
SOME OF THE MODELS HAD SCATTERED QPF BEHIND THE MAIN AREA OF
PRECIPITATION ON MONDAY. THERE IS SOME UPPER DIVERGENCE WITH THE
LEFT EXIT REGION OF AN UPPER LEVEL JET MAX. COLDER AIR MOVES IN
BEHIND THE DEPARTING SYSTEM BUT WATER TEMPERATURES...ACCORDING TO
GLERL...ON LAKE SUPERIOR WERE MAINLY IN THE 8C TO 10C RANGE.
TEMPERATURES AT 850MB WERE FORECAST TO BE NO COLDER THAN ABOUT -2C
DURING THE DAY ON MONDAY. DELTA-T VALUES OF 10 TO 12 WOULD NOT
APPEAR TO SUPPORT ANY LAKE EFFECT PRECIPITATION.

DUE TO ALL THE UNCERTAINTY IN THIS FORECAST...HAVE TRIED TO STICK
CLOSE TO THE PREVIOUS FORECAST AND ALSO MESH GRIDS WITH THOSE OF
SURROUNDING OFFICES.

.LONG TERM...MONDAY NIGHT THROUGH SUNDAY
ISSUED AT 319 PM CDT SUN OCT 19 2014

MAINLY DRY AND MILD CONDITIONS ARE EXPECTED THROUGH THE PERIOD.

A SHEARED VORT MAX AND JET STREAK WILL AFFECT FAR EASTERN WI AND
LAKE MICHIGAN ON MONDAY NIGHT...WITH MOST OF THE DYNAMICS
REMAINING TO OUR EAST. ASIDE FROM A FEW SPRINKLES NORTH AND EAST...
DRY CONDITIONS SHOULD PREVAIL. WITH A THERMAL TROF STILL IN PLACE
OVER THE REGION...AND ABUNDANT LLVL MOISTURE...EXPECT MOSTLY
CLOUDY SKIES TO PREVAIL THROUGH THE NIGHT. THE LOW CLOUDS ARE
EXPECTED TO LINGER AT LEAST INTO TUESDAY MORNING BEFORE MIXING
OUT...AS MODELS ONLY SHOW A GRADUAL DECREASE IN LLVL RH. CLOUD
COVER WILL KEEP MIN TEMPS FROM TANKING ON MONDAY NIGHT...WITH
30S AND LOWER 40S ANTICIPATED. NEAR NORMAL READINGS IN THE
UPPER 40S TO MIDDLE 50S SHOULD OCCUR ON TUESDAY.

ANTICIPATING MORE WIDESPREAD CLEARING TUESDAY NIGHT AS VERY
DRY CANADIAN AIR (H8 DEW POINT DEPRESSIONS OF 30-40 C) ADVECTS
INTO THE REGION. HAVE LOWERED MIN TEMPS SEVERAL DEGREES ON
TUESDAY NIGHT. BRIGHT SUNSHINE AND MIXING THROUGH 900-875 MB
SUPPORTS HIGHS IN THE MIDDLE TO UPPER 50S ON WEDNESDAY.

AN APPROACHING WEAK UPPER TROF AND FRONTAL BOUNDARY MAY BRING
A SMALL CHANCE OF SHOWERS TO FAR NC WI LATE WED NGT...AND TO
THE NW HALF OF THE FCST AREA ON THURSDAY. ULTIMATELY... IT
APPEARS THAT THE FRONT WILL WASH OUT BEFORE PCPN HAS A CHANCE TO
REACH EASTERN WI.

MODELS ARE NOT IN VERY GOOD AGREEMENT ON THE UPPER FLOW PATTERN
AND TEMPERATURE TRENDS LATE IN THE WEEK...WITH THE ECMWF MORE
AMPLIFIED ALOFT AND MORE AGGRESSIVE WITH A COLD FRONTAL PASSAGE
ON SATURDAY. GIVEN THE DIFFERENCES...STAYED FAIRLY CLOSE TO THE
MODEL BLEND DURING THAT PERIOD. DID OPT TO RAISE MAX TEMPS A FEW
DEGREES ON FRIDAY...AND WE MAY NEED TO MAKE EVEN BIGGER UPWARD
ADJUSTMENTS ON SATURDAY IF THE FRONT IS WEAKER OR SLOWER THAN
EXPECTED.
&&

.AVIATION...FOR 00Z TAF ISSUANCE
ISSUED AT 635 PM CDT SUN OCT 19 2014

ISOLATED SHOWERS OR SPRINKLES WILL END EARLY THIS
EVENING AS A WARM FRONT LIFTS NORTHEAST OF THE AREA. A TROUGH OF
LOW PRESSURE WILL THEN SLIDE OVER THE AREA TONIGHT SHIFTING WINDS
FROM SOUTHWEST TO WEST. SINCE THE AIR MASS IS DRY...VFR CONDITIONS
ARE EXPECTED TO PERSIST. AN UPPER DISTURBANCE JUST NORTH OF
MINNESOTA LATE SUNDAY AFTERNOON WILL DROP INTO THE GREAT LAKES
REGION LATE TONIGHT INTO MONDAY. MVFR CIGS WILL BEGIN TO SPREAD
INTO NORTHERN WISCONSIN OVERNIGHT AS COLDER AIR POURS OVER LAKE
SUPERIOR ON NORTHWEST WINDS. THESE MVFR CIGS MAY BRIEFLY SPREAD INTO
PARTS OF CENTRAL AND EAST CENTRAL WISCONSIN ON MONDAY AS THE UPPER
DISTURBANCE TRACKS OVER THE AREA.
&&

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

$$

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





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