000
FXUS63 KGRB 122336
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
636 PM CDT SUN MAY 12 2013

UPDATED AVIATION PORTION FOR 00Z TAF ISSUANCE

.SHORT TERM...TONIGHT AND MONDAY
ISSUED AT 232 PM CDT SUN MAY 12 2013

LATEST RUC ANALYSIS AND SATELLITE/RADAR IMAGERY SHOW SURFACE HIGH
PRESSURE STRETCHING FROM SOUTH-CENTRAL CANADA TO THE WESTERN GULF
COAST EARLY THIS AFTERNOON WHILE LOW PRESSURE PEELS AWAY OVER
QUEBEC.  AS CYCLONIC FLOW ABATES AND DRIER AIR BUILDS IN FROM THE
WEST...WIDESPREAD MORNING STRATO-CU HAS BEEN RETREATING TO THE
NORTHEAST...TURNING SKIES MOSTLY CLEAR TO PARTLY CLOUDY OVER MUCH OF
CENTRAL AND NORTHEAST WISCONSIN.  PLENTY OF CLEAR SKIES BENEATH THE
SURFACE HIGH OFF TO THE WEST...WHICH WILL MOVE INTO THE AREA
TONIGHT.  EVEN FARTHER WEST...A WARM FRONT OVER THE LEE OF THE
ROCKIES WILL ENTER THE REGION TOMORROW AFTERNOON.  FIRST CONCERN
IS TEMPS TONIGHT...FOLLOWED BY SMALL PRECIP CHANCES TOMORROW
AFTERNOON.

TONIGHT...HIGH PRESSURE OVER THE GREAT PLAINS WILL SHIFT ACROSS THE
WESTERN HALF OF WISCONSIN TONIGHT.  AS CLOUDS CONTINUE TO MIX OUT
THIS AFTERNOON...SKIES WILL BECOME CLEAR AND WINDS WILL BECOME LIGHT
AND VARIABLE BY EARLY TO MID-EVENING.  GOOD RADIATIONAL CONDITIONS
WILL THEN EXIST FOR THE REST OF THE NIGHT.  LOW TEMPS UPSTREAM OVER
WESTERN WISCONSIN AND MINNESOTA WERE MOSTLY AT OR BELOW 32 DEGREES
AND EXPECT SIMILAR READINGS LATE TONIGHT.  TEMPS WERE ALSO IN THE 34
TO 36 DEGREE RANGE OVER THE FOX VALLEY AND LAKESHORE LAST
NIGHT...WHEN THERE WAS CONSIDERABLY MORE WIND AND CLOUDS.  WILL NOT
HAVE THIS LUXURY TONIGHT...SO FIGURE TEMPS WILL FALL BELOW FREEZING
ACROSS MOST OF THE CWA.  WILL EXPAND THE FREEZE WARNING.

MONDAY...HIGH PRESSURE WILL SLIDE TO THE EAST ACROSS THE CENTRAL
GREAT LAKES.  WARM ADVECTION WILL RAMP UP ON THE BACKSIDE OF THE
HIGH AT THE SAME TIME AS MID AND HIGH CLOUDS SPILL OVER THE
MID-LEVEL RIDGE AXIS.  AS A RESULT...WILL SEE A SLOW INCREASE OF
CLOUDS OVER THE COURSE OF THE DAY.  AFTER 21Z...ENOUGH MOISTURE
ADVECTION LOOKS TO TAKE PLACE TO NEARLY SATURATE THE COLUMN OVER
CENTRAL AND NORTH-CENTRAL WISCONSIN.  MID-LEVEL LAPSE RATES ARE VERY
POOR...BUT MID-LEVEL FGEN APPEARS SUFFICIENT FOR THE POSSIBILITY OF
SCATTERED LIGHT SHOWERS DEVELOPING.  WILL INCREASE POPS INTO THE
40-50 PERCENT RANGE.  THERE IS A FAIRLY LARGE RANGE IN GUIDANCE FOR
TEMPS TOMORROW AFTERNOON...BETWEEN THE COLD ECMWF AND WARM NAM.
SPLITTING THE DIFFERENCE SHOULD GET TEMPS CLOSE AND WILL GO WITH
HIGHS IN THE UPPER 50S TO LOW 60S BUT COOLER LAKE SIDE.

.LONG TERM...MONDAY NIGHT THROUGH SUNDAY
ISSUED AT 232 PM CDT SUN MAY 12 2013

PCPN TRENDS MONDAY NIGHT INTO TUESDAY NIGHT...THE POTENTIAL FOR
SVR TSTMS TUESDAY NIGHT...GUSTY WINDS ON WEDNESDAY...PCPN TRENDS
NEXT WEEKEND...AND TEMPERATURES THROUGHOUT THE PERIOD ARE THE
MAIN FCST CONCERNS.

STRONG H8 WAA/MOISTURE CONVERGENCE WILL BRING A BAND OF SHOWERS THROUGH
THE AREA ON MONDAY NIGHT. ALTHOUGH THE RAIN WILL NOT LAST LONG AND QPF
AMOUNTS ARE EXPECTED TO BE LIGHT...FELT THAT POPS NEEDED TO BE RAISED
A LITTLE BIT. WAA/ISENT LIFT WILL CONTINUE ON TUESDAY AS A WARM FRONT
LIFTS INTO WISCONSIN. THIS FRONT IS EXPECTED TO MOVE INTO CENTRAL WI
LATE IN THE AFTERNOON. DESPITE SOME PERSISTENT FORCING...AN
INCREASINGLY CAPPED ATMOSPHERE AND LATE ARRIVAL OF THE INSTABILITY
AXIS PRECLUDES ADDING ANYTHING MORE THAN SLGT CHC/CHC POPS...MAINLY
OVER NORTHERN WI. TEMPERATURES WILL VARY GREATLY...WITH READINGS IN
THE MID 50S TO LOWER 60S NEAR THE LAKE...AND INLAND TEMPS RANGING
FROM THE UPPER 60S FAR NE WI TO THE LOWER TO MIDDLE 80S IN C WI.

THE WARM FRONT WILL LIFT NORTH TUESDAY...QUICKLY FOLLOWED BY THE COLD
FRONTAL PASSAGE DURING THE LATE EVENING AND OVERNIGHT HOURS. ELEVATED
CAPE OF 1500-2000 J/KG...VERY STEEP LAPSE RATES OF 7-8 C/KM...DEEP
LAYER SHEAR OF 40-50+ KTS AND 0-3 KM HELICITIES OF 400-500 WILL
PROVIDE PLENTY OF SUPPORT FOR SEVERE TSTMS...BUT CAPPING MAY BE
PROHIBITIVE FOR CONVECTIVE INITIATION. BEST CASE SCENARIO FROM THE
NAM AND A FEW OF THE SREF ENSEMBLE MEMBERS SHOW CINH OF 40-70
J/KG FOR A PARCEL LIFTED FROM THE 850-800 MB LEVEL OVER FAR
NORTHERN WI...BUT OTHER FCST SOUNDINGS SHOWED MUCH HIGHER CINH...
EVEN FROM ELEVATED PARCELS. WILL CONTINUE WITH CHC POPS TUESDAY
EVENING...AND A MENTION OF THE SVR TSTM POTENTIAL IN THE HAZARDOUS
WEATHER OUTLOOK...BUT HAVE TO ACKNOWLEDGE THE POTENTIAL FOR A MAINLY
DRY FCST. ANY PCPN THAT DOES DEVELOP WILL COME TO AN END OVERNIGHT
AS THE COLD FRONT SHIFTS EAST.

CAA...AN INCREASING NW PRESSURE GRADIENT AND DEEP MIXING WILL LEAD
TO A BREEZY/WINDY DAY ON WEDNESDAY. MIXING THROUGH 825-775 MB SUPPORTS
HIGH TEMPS IN THE LOWER TO MIDDLE 70S IN MOST LOCATIONS.

THE COLD FRONT WILL SETTLE SOUTH OF WISCONSIN FROM WEDNESDAY THROUGH
FRIDAY...AS ANOTHER COLD FRONT SAGS SOUTH OUT OF CANADA. WITH THE
REGION IN BETWEEN SYSTEMS...EXPECT A GENERALLY DRY PERIOD OVER THE
LATTER HALF OF THE WORK WEEK...WITH TEMPERATURES AT OR A LITTLE
ABOVE NORMAL.

LOW PRESSURE IS EXPECTED TO APPROACH FROM THE CENTRAL PLAINS THIS
WEEKEND...AND REACH THE IOWA VCNTY BY SUNDAY. AS THIS HAPPENS...
THE FRONT THAT STALLED TO OUR SOUTH WILL LIFT BACK INTO SOUTHERN
WISCONSIN...ALONG WITH ITS ASSOCIATED MOISTURE/ELEVATED INSTABILITY.
THIS SHOULD LEAD TO SHOWERS AND SCT TSTMS OVER THE REGION...ALONG
WITH COOLER TEMPERATURES DUE TO EAST WINDS AND ABUNDANT CLOUD COVER.
&&

.AVIATION...FOR 00Z TAF ISSUANCE
ISSUED AT 636 PM CDT SUN MAY 12 2013

WHILE SURFACE WINDS DIMINISH EARLY THIS EVENING...NORTHWEST
WINDS TO 20 KTS AT 2000 FEET WILL LINGER FOR THE REST OF THE EVENING
FOR A PERIOD OF NEAR LLWS CONDITIONS. OTHERWISE VFR CONDITIONS
EXPECTED TONIGHT INTO MONDAY. THERE IS A CHANCE FOR SHOWERS LATE
IN THE DAY MONDAY OVER CENTRAL AND NORTH CENTRAL WISCONSIN.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
FREEZE WARNING FROM 1 AM TO 7 AM CDT MONDAY FOR WIZ020-022-030-
031-035>040-045-048>050-073-074.
&&

$$

SHORT TERM.....MPC
LONG TERM......KIECKBUSCH
AVIATION.......TDH