000
FXUS63 KGRB 191807
AFDGRB

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

UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND MONDAY
ISSUED AT 410 AM CDT SUN MAY 19 2013

PCPN TRENDS TO BE THE PRIMARY PROBLEM OVER THE NEXT 24 HOURS AS
ACTIVE WEATHER OVER THE PLAINS MOVES INTO THE STATE.

UPPER RIDGE TO CONTINUE TO MOVE EAST OF THE AREA TODAY AS UPPER
TROF CUTS OFF OVER THE NORTHERN PLAINS. RATHER ILL-DEFINED FRONT
OVER SOUTHWEST WI...MN SUPPOSE TO LIFT NORTH THROUGH THE AREA
TODAY. ISOLATED LIGHT SHOWERS DRIFTING EAST ALONG THE WI/MI
BORDER. THUNDER SEEN EARLIER OVER VILAS IN AREA OF ELEVATED CAPE
THAT HAS SINCE LIFTED NORTH. TRENDED FORECAST TOWARDS GFS/EC FOR
THIS PERIOD GIVEN CURRENT PCPN TRENDS AND HANDLING OF SURFACE LOW.
POPS FORECAST CERTAINTY ON THE LOW SIDE GIVEN TIMING OF STORMS WITH
EXPECTED NUMBER OF BOUNDARIES THAT CONVECTION CAN DEVELOP ON AND
EFFECTS OF STABLE MARINE AIR OFF LAKE WITH CONTINUED EASTERLY
TRAJECTORY OF WINDS.

INCREASING INSTABILITY AND DIFFLUENT FLOW TO LEAD INCREASING POPS
FROM WEST TO EAST THROUGH THE DAY TODAY. MODELS SUGGEST CWA WILL
REMAIN DRY...BUT WITH CURRENT TRENDS ON RADAR HAVE ONLY STAYED
DRY OVER THE EAST. WILL GO WITH WIDESPREAD LIKELY POPS FOR TONIGHT
AND MONDAY WITH FALLING HEIGHTS AND JET MAX MOVING INTO IA/SW WI
BY MON MORNING.

GIVEN INCREASED SHEAR WITH JET AND ABUNDANT INSTABLILITY WITH
MOISTURE INFLUX ON MONDAY HAVE POTENTIAL FOR SOME OF THE STORMS
TO BE STRONG TO SEVERE ESPECIALLY IN THE WEST AND SOUTHERN PORTION
OF CWA.

TEMPERATURES TODAY VERY DEPENDENT ON CLOUDS WITH CONVECTION TO THE
WEST. HAVE BUMPED TEMPS UP A BIT ALONG THE LAKE BASED ON TRENDS
YESTERDAY...THOUGH STAYED CLOSE TO PREVIOUS FORECAST ELSEWHERE.

.LONG TERM...MONDAY NIGHT THROUGH SATURDAY
ISSUED AT 410 AM CDT SUN MAY 19 2013

MODELS WERE SHOWING A CLOSED 500MB CYCLONE SLOWLY MOVING FROM THE
PLAINS TO THE WESTERN GREAT LAKES REGION...THEN BECOMING AN OPEN
WAVE TROUGH DURING THE LATTER HALF OF THE WEEK.

THE PRESENCE OF THE 500MB CIRCULATION...WITH SHORT WAVE ENERGY
ROTATING AROUND IT...ALONG WITH AN APPROACHING SURFACE LOW AND A
NEARLY STATION FRONT ACROSS WISCONSIN WILL BE ENOUGH TO KEEP
SHOWERS AND THUNDERSTORMS IN THE FORECAST THROUGH THE FIRST HALF
OF THE WEEK. THERE IS A SLIGHT RISK OF SEVERE STORMS THROUGH
TUESDAY NIGHT...MAINLY ACROSS THE SOUTHERN PART OF THE AREA. SPC
EXPRESSED UNCERTAINTY REGARDING THE SEVERE POTENTIAL DUE TO
MULTIPLE ROUNDS OF STORMS AND THEIR IMPACT ON THE DEVELOPMENT OF
SUBSEQUENT CONVECTION. STAY TUNED FOR LATER DETAILS ON THIS EVENT.
HEAVY RAINFALL IS POSSIBLE WITH THE STORMS...EVEN IF THERE IS NO
SEVERE WEATHER...SO THERE IS SOME POTENTIAL FOR FLOODING BUT
RIVERS AND STREAMS HAVE BEEN RECEDING OVER THE PAST WEEK OR
SO...RESULTING IN LESS OF A FLOODING THREAT.

AS THE UPPER SYSTEM FINALLY DEPARTS LATE IN THE WEEK...THE CHANCE
FOR SHOWERS SHOULD COME TO AN END...BUT NORTHWEST UPPER FLOW WILL
KEEP TEMPERATURES BELOW NORMAL FOR THE END OF THE WORK WEEK AND
THROUGH THE WEEKEND.
&&

.AVIATION...FOR 18Z TAF ISSUANCE
ISSUED AT 106 PM CDT SUN MAY 19 2013

VFR CONDITIONS TO HOLD THRU MOST OF THIS AFTERNOON...
HOWEVER A SMALL CLUSTER OF TSTMS MOVING N-NE ALONG THE IA/IL
BORDER MAY REACH PARTS OF NE WI AFTER 22Z IF THEY HOLD TOGETHER.
EXPECT TO SEE MVFR CIGS POP UP DURING THE EVENING DUE TO THE
DEVELOPMENT OF FOG. ANOTHER ROUND OF SHWRS AND/OR TSTMS MAY MOVE
INTO THE REGION LATER TONIGHT AS A PIECE OF SHORTWAVE ENERGY LIFTS
NE AROUND THE PLAINS LARGE UPR TROF. POTENTIAL OF SEVERE LOOKS TO
BE SMALL...BUT SMALL HAIL AND GUSTY WINDS ARE POSSIBLE. A MIX OF
MVFR AND VFR CIGS/VSBYS EXPECTED ON MON AS A WRMFNT LIFTS NORTH
INTO WI AND MORE SHORTWAVES ARRIVE. IF WE CAN DESTABILIZE ENUF...
SOME OF THE NEW STORMS MAY BECOME SVR WITH LARGE HAIL AND DAMAGING
WIND GUSTS.
&&

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

$$

SHORT TERM.....TE
LONG TERM......MG
AVIATION.......AK