547
FXUS63 KGRB 301757
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
1257 PM CDT MON JUN 30 2025
UPDATED AVIATION PORTION FOR 18Z TAF ISSUANCE
KEY MESSAGES
- PATCHY AREAS OF DENSE FOG ARE POSSIBLE THIS MORNING, MAINLY
ACROSS CENTRAL AND NORTHERN WI.
- SCATTERED THUNDERSTORMS POSSIBLE THIS AFTERNOON. GUSTY WINDS
AND LARGE HAIL ARE MAIN HAZARDS.
- TEMPERATURES WILL BE NEAR TO ABOVE AVERAGE THIS WEEK.
- ROUND OF SHOWERS AND STORMS POSSIBLE FRIDAY INTO SATURDAY MAY
IMPACT 4TH OF JULY CELEBRATIONS.
DISCUSSION
ISSUED AT 303 AM CDT MON JUN 30 2025
FOG/SHOWERS THIS MORNING...
RAP ANALYSIS SHOWS A WEAK SHORT-WAVE OVER CENTRAL WI EARLY THIS
MORNING. THIS WAVE IS CAUSING SOME ISOLATED LIGHT SHOWERS ACROSS THE
REGION. AS THIS WAVE PUSHES EAST EXPECT THE SHOWER ACTIVITY TO
DECREASE AFTER SUNRISE.
BEHIND THE SHOWERS WERE SKIES HAVE BECOME CLEAR AN AREA OF DENSE FOG
CAN BE SEEN BY SATELLITE OVER MUCH OF WOOD AND WESTERN MARATHON
COUNTIES. WILL CONTINUE TO MONITOR WEB-CAMS AND SURFACE OBS TO SEE IF
THE FOG BECOMES MORE WIDESPREAD OVER THE NEXT FEW HOURS. IF THAT IS
THE CASE A DENSE FOG ADVISORY MAY BE NEEDED FOR A FEW HOURS THIS
MORNING.
AFTERNOON/EVENING THUNDERSTORM POTENTIAL...
RAP ANALYSIS AND WV IMAGERY SHOW A SHORT-WAVE DIGGING ACROSS
MINNESOTA EARLY THIS MORNING. THIS WAVE WILL MOVE EAST ACROSS
WISCONSIN DURING THE DAY ALONG WIND AN INCREASING 500MB JET. CAMS
SHOW AN INITIAL ROUND OF STORMS DEVELOPING OVER EAST-CENTRAL WI EARLY
THIS AFTERNOON JUST AHEAD OF THE SHORT-WAVE ALONG A SURFACE COLD
FRONT. RAP SOUNDINGS SHOW MLCAPE VALUES AROUND 1000 J/KG DURING THIS
TIME ALONG WITH 40-45 KTS OF 0-6KM SHEAR. THESE PARAMETERS COULD
SUPPORT A FEW ISOLATED STRONGER STORMS CAPABLE OF PRODUCING UP TO
QUARTERED SIZED HAIL AND 40-60 MPH WINDS. THE WIND THREAT WILL BE
PRIMARILY RELATED TO ANY DOWNBURSTS AS UPDRAFTS BECOME RAIN COOLED AS
MID-LEVEL WINDS ARE FAIRLY WEAK (15-20KTS). IT IS WORTH NOTING THAT
THE BETTER RISK FOR SEVERE WEATHER HAS SHIFTED SOUTH WHERE BETTER
MOISTURE AND INSTABILITY WILL RESIDE. CAMS ALSO NOW SHOW A RIGHT REAR
JET QUAD FURTHER SOUTH OVER MILWAUKEE AND CHICAGO.
A SECOND ROUND OF SHOWERS AND STORMS MAY ALSO BE POSSIBLE THIS
EVENING ACROSS NORTH-CENTRAL AND NORTHEAST WI BEHIND THE INITIAL
FRONT AS COOLER MID-LEVEL AIR OVERSPREADS WARMER LOW-LEVELS. HAIL
APPEARS TO BE THE MAIN THREAT AS WET BULB ZERO HEIGHTS AND THE
FREEZING LEAVE LOWER IN THE COOLER AIR MASS. ELONGATED HODOGRAPHS
DUE TO THE STRONG UPPER LEVEL WINDS ALSO SUPPORT A HAIL THREAT WITH
ANY ANY TALLER UPDRAFTS THAT CAN ACCESS THE STRONG SHEAR.
REST OF THIS WEEK...
PERSISTENT NORTHWESTERLY FLOW ALOFT IN RESPONSE TO A BUILDING RIDGE
OVER THE NORTHERN ROCKIES IS EXPECTED THROUGH THE MIDDLE PORTION OF
THE WEEK. THIS SHOULD LEAD TO MOSTLY DRY CONDITIONS TUESDAY THROUGH
THURSDAY, HOWEVER, ANY SUBTLE SHORT-WAVES MOVING THROUGH THE FLOW
COULD SPARK A ROUND OF SHOWERS OR STORMS. AT THIS POINT CONFIDENCE
IN TIMING OUT ANY OF THESE SHORT-WAVES IS VERY LOW SO KEPT THE NBM
10-20% POPS FOR THIS PERIOD.
NEXT PERIOD OF POTENTIALLY MORE IMPACTFUL WEATHER LOOKS TO ARRIVE
FRIDAY INTO SATURDAY. GLOBAL ENSEMBLES INDICATE GULF MOISTURE
RETURNS AS LOW-LEVEL WINDS BECOME SOUTHERLY AND DEW POINTS INCREASE
INTO THE MIDDLE 60S TO LOW 70S. INCREASING INSTABILITY ~ FRIDAY 1000-
1500 J/KG AND WEAK ISENTROPIC ASCENT COULD INITIATE A FEW ISOLATED
STORMS DURING THE AFTERNOON, HOWEVER, DEEP LAYER SHEAR IS EXPECTED
TO BE WEAK, LESS THAN 25KTS, DURING THE PERIOD. ENSEMBLES THEN BRING
A COLD FRONT ACROSS THE REGION LATE FRIDAY NIGHT INTO SATURDAY
MORNING WHICH COULD SET OFF ANOTHER ROUND OF SHOWERS AND STORMS.
CONFIDENCE IN THE TIMING OF THIS FEATURE IS STILL VERY LOW, BUT WILL
BE WATCHING TRENDS VERY CLOSELY GIVEN THAT FRIDAY IS INDEPENDENCE
DAY.
TEMPERATURES THROUGH THE WEEK AND INTO NEXT WEEKEND SHOULD HOLD
STEADILY NEAR TO ABOVE NORMAL WITH HIGHS IN THE 80S MOST DAYS.
FRIDAY LOOKS LIKE THE HOTTEST DAY OF THE WEEK WITH A FEW LOCATIONS
IN CENTRAL WI AND THE FOX VALLEY POSSIBLY GETTING TO THE 90S.
AVIATION
FOR 18Z TAF ISSUANCE
ISSUED AT 1244 PM CDT MON JUN 30 2025
SCATTERED THUNDERSTORMS WILL IMPACT NORTH-CENTRAL AND NORTHEAST
WISCONSIN THIS AFTERNOON INTO THIS EVENING. SOME OF THE STRONGER
STORMS COULD PRODUCE WIND GUSTS TO 35 KNOTS AND SMALL HAIL.
CONFIDENCE IS LOW IN THE AXACT TIMING ACROSS EASTERN WISCONSIN
AS TEMPERATURES IN THIS REGION HAVE REACHED THE CONVECTIVE
TEMPERATURES AND OUTFLOW BOUNDARIES ARE SINKING SOUTH. THE MAIN
FEATURE THAT WILL TRIGGER ADDITIONAL THUNDERSTORMS WILL BE ACROSS
NORTHERN WISCONSIN THIS AFTERNOON. THE STORMS SHOULD DIMINISH AND
THEN END AFTER SUNSET.
FOR THIS AFTERNOON, AREAS OF MVFR CIGS WILL RISE INTO THE
VFR CATEGORY OUTSIDE THUNDERSTORM ACTIVITY. LATER TONIGHT,
SOME PATCHY FOG IS EXPECTED TO FORM AS SKIES CLEAR AND WINDS
DIMINISH. CUMULUS FIELD BETWEEN 2,500 AND 3,500 EXPECTED TO
REDEVELOP LATE TUESDAY MORNING.
GRB WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION.....GK
AVIATION.......ECKBERG
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