Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 261736
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1236 PM CDT SUN OCT 26 2014

UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND MONDAY
ISSUED AT 315 AM CDT SUN OCT 26 2014

OVERALL NO SIGNIFICANT CHANGES TO PREVIOUS FORECAST THROUGH
MONDAY.

UPPER-LEVEL RIDGE WILL CONTINUE TO BUILD OVER THE FORECAST AREA
TODAY. SURFACE HIGH PRESSURE RIDGE AXIS CURRENTLY EXTENDING FROM
NORTHERN MINNESOTA TO NORTH CENTRAL ILLINOIS WILL STEADILY DRIFT
OFF TO THE SOUTHEAST. SHOULD SEE A NICE FALL DAY UNDER MOSTLY
SUNNY SKIES WITH LIGHT NORTHWEST WINDS. SURFACE RIDGE AXIS SHOULD
PAST TO OUR EAST LATE THIS AFTERNOON WITH WINDS TURNING LIGHT
SOUTHERLY...IN CONCERT WITH SOME HIGH CLOUDS SPREADING EASTWARD AHEAD
OF APPROACHING SHORTWAVE TROUGH. A MODEL BLEND LOOKED REASONABLE
FOR DAYTIME HIGHS TODAY WITH VALUES GENERALLY AROUND 60.

WAA THEN KICKS IN RAPIDLY OVERNIGHT AS 850 SOUTHWESTERLY WINDS
INCREASE TO ABOUT 40 KNOTS BY 06Z MONDAY. DESPITE A LACK OF AN
OBVIOUS MID-LEVEL IMPULSE RIDING UP THE WEST SIDE OF THE
RIDGE...WAA WILL BE ROBUST AND WILL BE THE PRIMARY FORCING TO
INITIATE ELEVATED SHOWER ACTIVITY OVER THE FORECAST AREA
OVERNIGHT. MODEL GUIDANCE SEEMS TO BE IN GOOD AGREEMENT ON
INITIATING THE ELEVATED ACTIVITY BETWEEN ABOUT 03Z AND 06Z OVER
THE WESTERN HALF OF THE STATE THEN QUICKLY EXPANDING IT EASTWARD
OVERNIGHT. PREVIOUS FORECAST HAD A GOOD HANDLE ON THIS SO FEW
CHANGES TO POP AND WEATHER GRIDS SUNDAY NIGHT. PLUME OF 7 TO 7.5
MID-LEVEL LAPSE RATES IN CONCERT WITH STRENGTHENING 850 WAA
APPEARS TO WARRANT CONTINUED MENTION OF ISOLATED THUNDER AS PER
PREVIOUS FORECAST.

SOME MODEL UNCERTAINTY ON MONDAY WITH RESPECT TO HOW QUICKLY
INITIAL ELEVATED ACTIVITY ASSOCIATED WITH WAA WILL MOVE OFF TO THE
EAST BEFORE ADDITIONAL SCATTERED SHOWER ACTIVITY ASSOCIATED WITH
APPROACHING COLD FRONT MOVES INTO THE AREA. LEANED TOWARD A BLEND
OF THE RECENTLY CONSISTENT ECMWF AND THE SREF WITH RESPECT TO
PRECIPITATION TRENDS. CURRENTLY ANTICIPATE A FAIRLY ORGANIZED BAND
OF ELEVATED SHOWER AND ISOLATED THUNDER TO SURGE NORTHEAST ACROSS
THE FORECAST AREA BETWEEN 09Z AND 15Z...FOLLOWED BY A LULL IN THE
PRECIPITATION CHARACTERIZED BY MORE ISOLATED SHOWER ACTIVITY AND
PERHAPS SOME PATCHY DRIZZLE AS MID-LEVEL MOISTURE GETS BRIEFLY
SCOURED OUT OF THE AREA. DOES NOT APPEAR THAT WARM FRONT WILL QUITE
MAKE IT INTO THE FORECAST AREA ON MONDAY THUS MAY SEE A FAIR
AMOUNT OF CLOUDS PERSISTING THROUGH MUCH OF THE DAY. TAPERED
DAYTIME HIGHS A FEW DEGREES ON MONDAY IN ANTICIPATION OF MORE
CLOUD COVER ESPECIALLY OVER THE NORTHERN HALF OF THE FORECAST
AREA.

.LONG TERM...MONDAY NIGHT THROUGH SATURDAY
ISSUED AT 315 AM CDT SUN OCT 26 2014

THE MEDIUM RANGE MODELS ARE IN GOOD AGREEMENT WITH THE TRACK OF THE
EXITING CYCLONE MONDAY NIGHT INTO TUESDAY.  THEN SPREAD INCREASES
SIGNIFICANTLY THURSDAY NIGHT INTO FRIDAY WITH THE DEPTH OF A
AMPLIFYING EASTERN CONUS TROUGH.  THE ECMWF IS SLIGHTLY FURTHER WEST
THAN THE GFS WITH THIS TROUGH BUT MUCH DEEPER...THEREBY PUSHING A
MUCH COLDER AIRMASS THAN THE GFS INTO THE REGION.  THE GFS ENSEMBLE
MEAN SPLITS THE DIFFERENCE IN SOME WAYS...AND WILL GO WITH ITS
SOLUTION LATE IN THE FORECAST.

MONDAY NIGHT THROUGH TUESDAY NIGHT...WITH A WARM FRONT INITIALLY
STALLED OVER SOUTHERN WISCONSIN...AN INCOMING SHORTWAVE TROUGH WILL
CREATE A SURFACE LOW ALONG THE TRAILING COLD FRONT...WHICH WILL
LIFT NE ACROSS SOUTHEAST WISCONSIN AND INTO LOWER MICHIGAN MONDAY
NIGHT.  STRENGTHENING MID-LEVEL FGEN AND UPPER DIVERGENCE WILL HELP
SPREAD ANOTHER ROUND OF PRECIP ACROSS THE FORECAST AREA MONDAY
EVENING.  PRECIP WILL LIKELY CONTINUE OVERNIGHT ACROSS THE NORTH AND
ALSO THE EAST.  AS THE SURFACE LOW EXITS ON TUESDAY...COMMA HEAD
MOISTURE WILL SWING THROUGH THE AREA DURING THE LATE MORNING AND
AFTERNOON HOURS.  ALTHOUGH THERE MAYBE BRIEF CLEARING WITHIN THE DRY
SLOT...SHOULD SEE A MOSTLY CLOUDY DAY WITH OCCASIONAL SHOWERS...MORE
WIDESPREAD ACROSS THE NORTH.  THEN COLDER AIR ARRIVES BEHIND THE
SYSTEM FOR TUESDAY NIGHT...WHICH WILL CHANGE PRECIP ACROSS THE NORTH
OVER TO SNOW.  COULD SEE MINOR ACCUMS ON GRASSY SURFACES.

REST OF THE FORECAST...SNOW SHOWERS LOOK TO END OVER NORTHERN
WISCONSIN WEDNESDAY MORNING...BUT ITS LOOKING RATHER DOUBTFUL THAT
ANY CLEARING WILL OCCUR.  WEAK SHORTWAVE ENERGY WILL PUSH MID AND
UPPER CLOUDS ACROSS THE REGION WEDNESDAY NIGHT.  POSITION OF THE
BAROCLINIC ZONE WOULD GIVE A BETTER CHANCE OF PRECIP OVER SOUTHERN
WISCONSIN.  THEN AN AMPLIFYING TROUGH AND COLD FRONT DROP THROUGH THE
REGION THURSDAY AND THURSDAY NIGHT.  RAIN AND SNOW CHANCES WILL
ACCOMPANY THE TROUGH AND COULD SEE MINOR ACCUMULATIONS...EVEN INTO
THE FOX VALLEY.  THEN CANADIAN HIGH PRESSURE WILL BRING THE COLDEST
AIRMASS SO FAR THIS FALL INTO THE REGION FOR FRIDAY BUT WITH SOME
MODERATION ON SATURDAY.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 1235 PM CDT SUN OCT 26 2014

SFC RDG AXIS OVER CNTRL WI WL CONT TO DRIFT EAST THIS AFTERNOON
AND ALLOW WINDS TO TURN S-SE BY SUNSET. VFR CONDITIONS TO PREVAIL
INTO THE EVENING HOURS...HOWEVER EXPECT THICKER MID/HI CLOUDS TO
BECOME MORE EVIDENT AS A WARM FRONT LIFTS NE TOWARD THE MIDWEST
TNGT. BY LATE EVENING...A SURGE OF WARMER AIR ALOFT INTO WI WL
TAKE PLACE AS A 40 KT LOW-LEVEL JET ALSO INCREASES THE MOISTURE
OVER THE REGION. EXPECT TO SEE A BAND OF SHWRS DEVELOP DURING THE
OVERNIGHT HOURS...ACCOMPANIED BY A CHC OF TSTMS AS INSTABILITY IN
THE MID-LEVELS OF THE ATMOSPHERE INCREASES. CIGS/VSBYS COULD DROP
INTO THE MVFR RANGE LATER TNGT UNDER HEAVIER BURSTS OF PCPN. IN
ADDITION TO THE PCPN...HAVE PLACED LLWS INTO THE ALL THE TAF SITES
FOR LATE TNGT INTO MON MORNING DUE TO THE STRENGTH OF THE LOW-
LEVEL JET. PCPN IS FCST TO BECOME MORE WIDELY SCATTERED OR EVEN
DIMINISH TO PATCHY DRIZZLE LATE MON MORNING/EARLY MON AFTERNOON AS
THE STRONGER LIFT SHIFTS AWAY FROM THE AREA. HOWEVER...A SFC TROF
AND COLD FRONT ARE EXPECTED TO APPROACH CENTRAL WI LATER MON
AFTERNOON WITH PCPN PICKING BACK UP. CIGS/VSBYS ARE FCST TO SETTLE
INTO THE IFR/MVFR RANGE MAINLY FROM 15Z MON THRU THE REST OF THE
DAY AS LOW-LEVEL MOISTURE CONTS TO GET PULLED INTO WI.
&&

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

$$

SHORT TERM.....ESB
LONG TERM......MPC
AVIATION.......KALLAS






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