010
FXUS63 KGRB 131956
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
256 PM CDT MON JUL 13 2020
FORECAST DISCUSSION FOR ROUTINE AFTERNOON FORECAST ISSUANCE
SHORT TERM
TONIGHT AND TUESDAY
ISSUED AT 256 PM CDT MON JUL 13 2020
HIGH PRESSURE THAT KEPT US DRY THE PAST COUPLE DAYS IS ON ITS WAY
OUT THIS EVENING. AS RETURN FLOW SETS UP ON THE LEE SIDE OF THE
HIGH TONIGHT, SOUTHERLY FLOW WILL DEVELOP A 30-40 KNOT LOW LEVEL
JET ACROSS CENTRAL WISCONSIN. RISING DEWPOINTS OVERNIGHT COMBINED
WITH THE LLJ WITH BRING THE DEVELOPMENT OF SOME UPPER LEVEL
SHOWERS LATE TONIGHT. DEEP LAYER SHEAR AROUND 30 TO 35 KNOTS
COULD ORGANIZE A FEW OF THE ELEVATED STORMS LONG ENOUGH TO PRODUCE
A FEW AREAS OF SMALL HAIL, MAINLY ACROSS CENTRAL TO NORTH-CENTRAL
WI. ONCE THE LLJ BEGINS TO WEAKEN TUESDAY MORNING HOWEVER, MOST
OF THE CONVECTIVE STORMS ARE EXPECTED TO DIMINISH INTO SHOWERS BY
LATE MORNING, LEADING TO A BREAK BEFORE STORMS REDEVELOP LATER ON
TUESDAY. LOW TEMPERATURES TONIGHT WILL FALL INTO THE LOWER TO
MIDDLE 60S.
TUESDAY...A FEW SHOWERS MAY STILL BE IN PLACE ACROSS THE REGION,
ALONG WITH A FEW AREAS OF UPPER LEVEL CLOUD COVER. THE MAIN EVENT
WILL BE IN THE AFTERNOON AS A COLD FRONT MOVES INTO NORTH-CENTRAL
AND CENTRAL WI. PRECIPITATION WILL BE MAINLY FOCUSED AWAY FROM THE
FOX VALLEY THROUGH THE EVENING, BEFORE THE FRONT FINALLY MAKES ITS
WAY EASTWARDS TUESDAY NIGHT. PWATS WILL PUSH UPWARDS OF 1.5-2
INCHES, MAKING HEAVY RAINFALL A GOOD POSSIBILITY FOR MUCH OF THE
AREA. THE STRENGTH OF SEVERE WEATHER REMAINS SOMEWHAT UNCERTAIN
FOR THE REGION HOWEVER. DEEP LAYER SHEAR REMAINS 35 TO 50 KNOTS
THROUGH THE LATE AFTERNOON, WHICH WILL PROVIDE SOME ORGANIZATION
TO DEVELOPING STORMS. LOW LEVEL HELICITY AROUND 200-300 WILL
SUPPORT DEVELOPING MESOCYCLONES AND ALSO SUGGESTS THE POTENTIAL
FOR A BRIEF SPIN UP OR ISOLATED TORNADO IN ANY STRONGER STORMS
THAT DEVELOP, AS LOW LEVEL VORTICITY WILL BE FAIRLY AVAILABLE TO
DEVELOPING UPDRAFTS AS WELL. THE MAIN UNCERTAINTY REMAINS THE
AVAILABILITY OF INSTABILITY, AS MODELS CONTINUE TO DIVERGE ON HOW
THE MORNING SHOWERS AND CLOUD COVER WILL IMPACT THE REGION AHEAD
OF THE FRONT. OVERALL, EXPECT HEAVY RAINFALL TO BE VERY LIKELY,
WITH THE POTENTIAL FOR SEVERE HAIL AND WIND TO DEVELOP IN STRONGER
CELLS. THE TORNADO THREAT IS ALSO PRESENT, BUT WILL BE MORE
ISOLATED. SPC KEEPS US IN THE MARGINAL RISK FOR MOST OF THE
REGION, WITH THE SLIGHT RISK EXTENDING INTO CENTRAL WI FROM THE
SOUTHWEST, WHERE THE BEST CAPE IS, WHICH SEEMS VERY REASONABLE.
THE SEVERE THREAT SHOULD BEGIN TO DIMINISH IN THE LATE EVENING TO
EARLY OVERNIGHT HOURS, AS THE FRONT CROSSES THE REGION AND DIURNAL
INSTABILITY BEGINS TO DISSIPATE. HIGH TEMPERATURES FOR TUESDAY
ARE EXPECTED TO BE IN THE LOWER 70S UP NORTH TO THE LOWER 80S NEAR
THE FOX VALLEY.
LONG TERM
TUESDAY NIGHT THROUGH MONDAY
ISSUED AT 256 PM CDT MON JUL 13 2020
THE THREAT FOR STRONG TO SEVERE STORMS WILL CONTINUE INTO TUESDAY
EVENING AHEAD OF AN APPROACHING COLD FRONT, WITH THE MAIN THREAT
TRANSITIONING TO HEAVY RAINFALL DURING THE OVERNIGHT HOURS WITH
THE LOSS OF DAYTIME HEATING AND THE BULK OF THE INSTABILITY.
THE FRONT WILL STALL OUT OVER THE AREA ON WEDNESDAY, PROVIDING A
FOCUS FOR ADDITIONAL SHOWERS AND THUNDERSTORMS THROUGH WEDNESDAY
EVENING AS A MID LEVEL SHORTWAVE RIDES ALONG THE FRONTAL BOUNDARY.
UNLIKE TUESDAY, THESE STORMS ARE NOT EXPECTED TO BE SEVERE AS
ABUNDANT CLOUD COVER ALONG THE FRONT IS EXPECTED TO PUT A LIMIT ON
THE AMOUNT OF INSTABILITY THAT IS AVAILABLE DURING THE AFTERNOON
AND EVENING HOURS.
HIGH PRESSURE WILL THEN BRING A PERIOD OF DRY WEATHER TO THE
WESTERN GREAT LAKES LATE WEDNESDAY NIGHT, LASTING THROUGH FRIDAY
MORNING. A LOW PRESSURE SYSTEM APPROACHING THE REGION FROM THE
WEST WILL BRING THE CHANCE OF SHOWERS AND THUNDERSTORMS BACK TO
THE AREA LATE IN THE WEEK AND INTO EARLY NEXT WEEK. TEMPERATURES
DURING THIS PERIOD WILL ONCE AGAIN RISE WELL INTO THE 80S, WITH
HIGHS THIS WEEKEND APPROACHING OR EXCEEDING 90 DEGREES ACROSS MUCH
OF CENTRAL, EAST-CENTRAL AND NORTHEAST WISCONSIN. DEPENDING ON
HOW MUCH CLOUD COVER LINGERS ACROSS THE AREA WITH THE
AFOREMENTIONED SHOWERS AND THUNDERSTORMS, HEAT INDICES ARE
EXPECTED TO RISE WELL INTO THE 90S WITH A FEW 100 DEGREE READINGS
POSSIBLE THIS NEXT WEEKEND. WHILE THE HOT TEMPERATURES WILL BRING
AN INCREASE IN INSTABILITY, IT IS TOO EARLY TO DETERMINE IF THESE
STORMS ARE EXPECTED TO BE SEVERE.
AVIATION
FOR 18Z TAF ISSUANCE
ISSUED AT 1255 PM CDT MON JUL 13 2020
VFR CONDITIONS WILL CONTINUE THROUGH THE BEGINNING OF THE TAF
PERIOD AND INTO THE EARLY OVERNIGHT HOURS. THE MAIN AVIATION
CONCERN FOR THE TAF PERIOD WILL BE RAIN AND THUNDERSTORMS
DEVELOPING ACROSS CENTRAL AND NORTHERN WISCONSIN TONIGHT AS A LOW
LEVEL JET DEVELOPS. THE RAIN AND STORMS WILL BRING MVFR AND
POSSIBLY IFR CONDITIONS TO CENTRAL WISCONSIN AFTER 06Z, AS CLOUD
DECKS AND VISIBILITY DROP. THIS WILL MAINLY IMPACT RHI, BUT IS
EXPECTED TO SPREAD TO AUW AND CWA BY THE MID MORNING HOURS. THE
LOW LEVEL JET WILL ALSO BUILD LOW LEVEL WIND SHEAR INTO THE REGION
OVERNIGHT. THUNDERSTORMS WILL THEN DIMINISH TOWARDS THE END OF THE
TAF PERIOD, LEAVING RAIN IN CENTRAL TO NORTHERN WISCONSIN.
ANOTHER ROUND OF STRONGER STORMS IS POSSIBLE AFTER THE CURRENT
TAF PERIOD, TUESDAY EVENING.
GRB WATCHES/WARNINGS/ADVISORIES
NONE.
SHORT TERM.....UHLMANN
LONG TERM......KURIMSKI
AVIATION.......UHLMANN
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