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000
FXUS63 KGRB 200411
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1111 PM CDT SUN MAY 19 2013

UPDATED AVIATION PORTION FOR 06Z TAF ISSUANCE

.SHORT TERM...TONIGHT AND MONDAY
ISSUED AT 242 PM CDT SUN MAY 19 2013

MAIN FCST FOCUS OVER THE NEXT 24 HOURS TO BE ON TSTM TRENDS AS NE
WI TO SUCCUMB TO THE LARGE UPR TROF CURRENTLY AFFECTING THE PLAINS/
MIDWEST.

THE 19Z MSAS SFC ANALYSIS SHOWED SEVERAL AREAS OF LOW PRES (NRN SD...
CNTRL IA AND NW OK) WITH A COUPLE OF WEAK BOUNDARIES EXTENDED WEST
TO EAST FROM SRN MN TO SRN WI AND NRN MO TO SRN IL. VSBL SATL
IMAGERY/RADAR MOSAIC INDICATED SEVERAL CLUSTERS OF TSTMS ASSOCIATED
WITH MAINLY SHORTWAVE ENERGY ROTATING AROUND THE PLAINS UPR LOW
AND AN UNSTABLE ATMOSPHERE. SEVERAL WATCH BOXES ARE LOCATED TO TO
OUR SW.

THE BROAD UPR TROF TO RESIDE OVER THE PLAINS TNGT WITH SEVERAL
EMBEDDED SHORTWAVES ROTATING NEWD TOWARD THE WRN GREAT LAKES. ONE
SUCH SHORTWAVE IS FCST TO ALREADY BE AFFECTING OUR VCNTY LATE THIS
AFTERNOON WITH A SMALL AREA OF STORMS HEADED TOWARD ERN WI. AS
EACH OF THESE SHORTWAVES ROTATES TOWARD WI...EXPECT TO SEE A
ROUND OF SHWRS/TSTMS TO ACCOMPANY EACH ONE. DO NOT PLAN ON TRYING
TO GET TOO SPECIFIC WITH TIMES IN THE FCST...BUT THE BOTTOM LINE
IS THAT NE WI WL SEE AT LEAST ONE SHWR/TSTM COMPLEX AFFECT THE
AREA TNGT...THUS HAVE GONE WITH LIKELY OR CATEGORICAL POPS. PLENTY
OF LOW-LEVEL MOISTURE IN PLACE WITH PW VALUES HOVERING AROUND 1.5
INCHES AND DEW PTS IN THE 55-60 DEG RANGE. THEREFORE...ANY TSTMS
COULD DROP LOCALLY HEAVY RAINFALL AT ANY ONE POINT. A MILD NGT IN
STORE WITH A PERSISTENT SW WIND ALOFT WITH MIN TEMPS RANGING FROM
THE MID 50S LAKESIDE TO AROUND 60 ELSEWHERE.

THE UPR TROF CONTS TO SIT ACROSS THE PLAINS ON MON WITH AN AREA OF
LOW PRES SITUATED ROUGHLY OVER ERN SD. AS A PREVAILING SOUTH WIND
CONTS TO PUMP WARM/MOIST/UNSTABLE AIR INTO WI...THESE WINDS WL
ALSO HELP TO LIFT A WRMFNT NWD INTO WI BY MON AFTERNOON. THIS
FNT...COMBINED WITH INCREASING INSTABILITY...SHEAR AND ADDITIONAL
SHORTWAVE ENERGY WL SET THE STAGE FOR MORE SHWRS/TSTMS OVER NE WI.
DEPENDING ON HOW THE CONVECTION PLAYS OUT IN THE MORNING WL
DETERMINE THE THREAT OF SEVERE WEATHER MON AFTERNOON. IF CLOUDS
CAN THIN AT ALL AND ALLOW INSTABILITY TO TAKE OFF (CAPES UP TO 2K
J/G)...THERE IS A POSSIBILITY OF SEEING LARGE HAIL AND DAMAGING
WINDS. SPC HAS PLACED ALL OF NE WI IN A SLIGHT RISK ON MON WHICH
APPEARS VALID RIGHT NOW. MAX TEMPS WL BE TRICKY DEPENDING ON PCPN
TRENDS/TIMING. ANY BRIEF BREAK IN THE PCPN COULD SEE READINGS
SURGE AGAIN TOWARD 80 DEGS.

.LONG TERM...MONDAY NIGHT THROUGH SUNDAY
ISSUED AT 242 PM CDT SUN MAY 19 2013

DURING THE UPCOMING WORK WEEK...LARGE SCALE PATTERN WILL GRADUALLY EVOLVE
FROM A BROAD TROUGH AND CLOSED UPPER-LOW OVER THE CENTRAL CONUS TO
A BUILDING RIDGE OVER THE CENTRAL CONUS WITH TROUGHS OVER MID-ATLANTIC
STATES AND WEST COAST. TEMPERATURES WILL START ABOUT 10 DEGREES
ABOVE NORMAL EARLY IN THE WEEK...THEN FALL BACK TO NEAR OR A LITTLE
BELOW NORMAL THERAFTER. EXPECT A FAIRLY ACTIVE AND WET PERIOD FOR
AT LEAST THE THE FIRST HALF OF THE WEEK AS THE UPPER LOW OVER THE
CENTRAL CONUS FILLS AND DRIFTS EAST ACROSS THE WESTERN GREAT LAKES
REGION.

FORECAST CHALLENGES THROUGH MIDWEEK WILL REVOLVE AROUND TIMING OF
PRECIPITATION EPISODES ASSOCIATED WITH INDIVIDUAL EMBEDDED SHORTWAVE
DISTURBANCES ROTATING AROUND THE UPPER-LOW...POTENTIAL FOR NOTABLE RAINFALL
AND MARGINAL SEVERE WEATHER.

FORECAST FOR MONDAY NIGHT SOMEWHAT AT THE MERCY OF HOW CONVECTION
EVOLVES DURING THE DAY ON MONDAY ASSOCIATED WITH UPPER-LVEL
DISTURBANCE AND WARM FRONT LIFTING NORTHWARD INTO NORTHERN
WISCONSIN. LATEST MODEL GUIDANCE WOULD SUGGEST THAT AREA OF
SHOWERS AND THUNDERSTORMS ASSOCIATED WITH WARM FRONT WILL LIFT
INTO NORTHERN WISCONSIN BY 00Z TUESDAY. GUIDANCE ALSO SUGGESTS
THAT IN THE WAKE OF THE UPPER-LEVEL DISTURABCE...SHOWER AND
THUNDERSTORM ACTIVITY MAY WANE IN AREA COVERAGE FOR A TIME MONDAY NIGHT.
HOWEVER...GIVEN AS THERE IS STILL MUCH UNCERTAINTY ON TIMING OF
THE SHORTWAVE AND EXACTLY HOW FAR NORTH THE WARM FRONT WILL BE
ABLE TO LIFT NORTWARD...DIFFICULT TO ADD MUCH DETAIL THUS WILL
MAINTAIN LIKELY POPS ACROSS THE ENTIRE FORECAST AREA FOR MONDAY
NIGHT. DESPITE INCREASING FAVORABLE DEEP LAYER SHEAR THINK ANY
MARGINAL SEVERE WEATHER POTENTIAL WILL LIKELY BE CONFINED TO THE
LATE AFTERNOON TO EARLY EVENING ON MONDAY WHEN ATMOSPHERE EXPECTED
TO BE MOST UNSTABLE.

DURING THE DAY ON TUESDAY LOW-LEVEL JET STARTS TO VEER MORE
SOUTHWESTERLY WITH COLD AIR ADVECTION DEVLOPING ON THE SOUTHERN
AND SOUTHEAST QUADRANT OF THE UPPER-LOW. WITH SURFACE LOW STILL
SITUATED NEAR MSP TUESDAY AFTERNOON AND SURFACE BOUNDARY AND
ASSOCIATED CONVERGENCE EXTENDING EAST ACOSS THE FORECAST
AREA...ADDITIONAL SCATTERED SHOWER AND THUNDERSTORM ACTIVITY
TUESDAY AFTERNOON STILL APPEARS LIKELY...ESPECIALLY IF SUFFICIENT
INSOLATION CAN HELP TO FURTHER DESTABLIZE THE ATMOSPHERE. STILL
CANNNOT RULE OUR MARGINAL SEVERE TUESDAY AFTERNOON ESPECIALLY OVER
THE SOUTHERN HALF OF THE FORECAST AREA.

WEAKENING SURFACE LOW WILL CONTINUE TO DRIFT EAST ACROSS THE
FORECAST AREA ON WEDNESDAY WITH CONTINUED BOUNDARY LAYER
CONVERGENCE ALONG EAST-WEST FRONTAL BOUNDARY....CONTINUING MORE
SCATTERED SHOWER AND ISOLATED THUNDERSTORM ACTIVITY.  THIS
BOUNDARY WILL CONTINUE TO SAG SOUTHWARD INTO SOUTHERN WISCONSIN BY
WEDNESDAY EVENING...BRINGING AN END TO THE PRECIPIATION.

SURFACE HIGH PRESSURE SHOULD START TO BUILD SOUTHWARD ACROSS THE
FORECAST AREA DURING THE DAY ON THURSDAY WITH SURFACE RIDGE IN
PLACE OVER THE AREA ON FRIDAY. FRIDAY LOOKS TO BE A PLEASANT DAY
WITH TEMPERATURES GENERALLY IN THE 60S...EXCEPT ALONG THE
LAKESHORE WHERE READINGS WILL BE MAINLY IN THE 50S WITH A GRADIENT
NORTHEAST WIND. HIGH PRESSURE RIDGE SHOULD CONTINUE TO INFLUENCE
SENSIBLE WEATHER ON SATURDAY WITH TEMPERATURES CONTINUING TO
REBOUND CLOSER TO SEASONAL NORMALS...NEAR 70 DEGREES.

BY NEXT SUNDAY...ECMWF APPEARS TO BE AN OUTLIER IN THAT IT SEEMS
TOO AGRESSIVE BREAKING DOWN THE SHORTAWVE RIDGE OVER THE NORTHERN
PLAINS AND EJECTING A SHORTWAVE DISTURBANCE EASTWARD INTO THE
WESTERN GREAT LAKES. FOR NOW...PREFER THE SREF ENSEMBLE MEAN WHICH
MAINTAINS MORE STOUT RIDGING ACROSS THE NORTHERN PLAINS WITH DRY
CONDITIONS PERSISTING.
&&

.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 1110 PM CDT SUN MAY 19 2013

MVFR AND LOCAL IFR CONDITIONS ASSOCIATED WITH SCATTERED SHWRS AND
TSTMS AS THEY MOVE INTO THE REGION ASSOCIATED WITH A WEATHER
DISTURBANCE LIFTING NORTHEAST AROUND THE LARGE UPPER TROF OVER THE
PLAINS. POTENTIAL FOR GUSTY WINDS IN CENTRAL AND NORTH-CENTRAL
AIRPORTS. A MIX OF MVFR AND VFR CIGS/VSBYS EXPECTED ON MON AS A
WRMFNT LIFTS NORTH INTO WI. SOME OF THE MONDAY STORMS MAY BECOME
SEVERE WITH LARGE HAIL AND DAMAGING WIND GUSTS.

&&

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

$$

SHORT TERM.....KALLAS
LONG TERM......ESB
AVIATION.......JKL