531
FXUS63 KGRB 200719
AFDGRB
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
219 AM CDT MON APR 20 2026
FORECAST DISCUSSION FOR ROUTINE MORNING FORECAST ISSUANCE
KEY MESSAGES
-MINOR TO MODERATE FLOODING CONTINUES ON SEVERAL RIVERS, WITH
MAJOR FLOODING EXPECTED ON THE WOLF RIVER THROUGH TUESDAY. WATER
LEVELS HAVE CRESTED IN MOST AREAS, AND DUE TO AN EXTENDED PERIOD
OF DRY WEATHER, A GRADUALLY DROP IS ANTICIPATED THROUGH THE WEEK.
-SHOWERS AND THUNDERSTORMS ARE EXPECTED LATE THURSDAY AFTERNOON
INTO THURSDAY NIGHT. HEAVY RAINFALL MAY ACCOMPANY ANY
THUNDERSTORMS. THERE IS A 30-50% CHANCE OF RAINFALL IN EXCESS OF
1/2 INCH, BUT LOCALIZED AMOUNTS TO 1-2 INCHES COULD OCCUR.
-TEMPERATURES WILL BE BE BELOW NORMAL TODAY, WITH MUCH ABOVE
NORMAL TEMPERATURES IN THE 60S AND 70S EXPECTED AWAY FROM LAKE
MICHIGAN TUESDAY THROUGH FRIDAY.
DISCUSSION
ISSUED AT 219 AM CDT MON APR 20 2026
DRY AND COOL CONDITIONS CONTINUE TODAY AS UPPER RIDGING BUILDS OVER
THE REGION. A SHORT-WAVE, CURRENTLY OVER NORTHERN MANITOBA WILL WORK
EAST ACROSS CANADA TODAY DRAGGING A COLD FRONT ACROSS THE WESTERN
GREAT LAKES THIS EVENING. THIS WILL LEAD AN INCREASE IN CLOUD COVER
THIS AFTERNOON, HOWEVER, WITH SUCH A DRY AIR MASS IN PLACE THE
CHANCE FOR EVEN A SPRINKLE IS LESS THAN 10%. FORECAST SOUNDINGS THIS
AFTERNOON DO SHOW A DEEPLY MIXED PBL WHICH WILL LEAD TO LOW RELATIVE
HUMIDITY VALUES OF 20-30 PERCENT, LOWEST ACROSS NORTHERN WI. DEEP
MIXING IS EXPECTED AGAIN ON TUESDAY AND WEDNESDAY WITH RHS SIMILARLY
BOTTOMING OUT AROUND 20-30 PERCENT. WHILES FUELS ARE RATHER WET FROM
RECENT RAIN THESE LOWER RHS WILL HELP DRY THEM OUT AND MAY LEAD TO
AN UPTICK IN WILDFIRE ACTIVITY THROUGH MID-WEEK.
MAIN FOCUS OF THE EXTENDED FORECAST IS A ROUND OF SHOWERS AND
THUNDERSTORMS EXPECTED THURSDAY EVENING INTO FRIDAY. INCREASING
SOUTHERLY WINDS WEDNESDAY NIGHT AND THURSDAY WILL DRAW GULF MOISTURE
INTO THE AREA WITH PWATS REACHING 1.2 TO 1.5 INCHES, WHICH IS NEAR
THE CLIMATOLOGICAL MAX. WIDESPREAD ASCENT WILL OVERSPREAD THE REGION
AS A TROUGH EJECTS OUT OF THE NORTHER PLAINS THURSDAY REACHING THE
WESTERN GREAT LAKES THURSDAY NIGHT. THIS WILL LEAD TO SCATTERED TO
WIDESPREAD SHOWERS WITH EMBEDDED THUNDERSTORMS. ENSEMBLE MEAN MUCAPE
VALUES INCREASE TO 500-600 J/KG. THIS COULD SUPPORT ISOLATED
STRONGER STORMS, HOWEVER, DEEP LAYER SHEAR IS EXPECTED TO BE
MAXIMIZED WEST OF FORECAST AREA WHICH MAY KEEP THE SEVERE WEATHER
THREAT GENERALLY OVER MN AND WESTERN WI. PRECIPITATION AMOUNTS WILL
LIKELY VARY WIDESPREAD DUE TO LOCALIZED CONVECTION WITH THIS SYSTEM.
CURRENT NBM PROBS SHOW 30-50% CHANCE FOR GREATER THAN 0.5" ACROSS
MOST OF THE FORECAST AREA WITH HIGH END AMOUNTS (95TH PERCENTILE)
AROUND 1.2-2" WHICH WOULD IS REASONABLE TO EXPECT IN AREAS THAT SEE
THE STRONGEST STORMS.
ZONAL FLOW BECOMES MORE FAVORABLE BEHIND THE COLD FRONT FRIDAY INTO
NEXT WEEKEND WHICH MAY LEAD TO A PERIOD OF COOLER TEMPERATURES AND ON
AND OFF SHOWERS.
AVIATION
FOR 06Z TAF ISSUANCE
ISSUED AT 1156 PM CDT SUN APR 19 2026
VFR CONDITIONS WILL CONTINUE THROUGH MONDAY EVENING. MID AND
HIGH CLOUDS WILL MOVE INTO THE REGION MONDAY AFTERNOON AND
CONTINUE INTO MONDAY EVENING. LIGHT AND VARIABLE WINDS OVERNIGHT
WILL BECOME SOUTH 5 TO 10 KNOTS MONDAY MORNING, THEN INCREASE TO
10 TO 20 KNOTS WITH GUSTS OF 20-30 KNOTS MONDAY AFTERNOON
AND EVENING. EXPECT LOW LEVEL WIND SHEAR TO DEVELOP AROUND
02-03Z TUESDAY ACROSS THE ENTIRE AREA, FROM 230-240 DEGREES
AROUND 45 KNOTS.
HYDROLOGY
ISSUED AT 219 AM CDT MON APR 20 2026
MINOR TO MODERATE FLOODING CONTINUES ON MANY RIVERS, WITH MAJOR
FLOODING EXPECTED TO PERSIST ON PARTS OF THE WOLF RIVER THROUGH
TUESDAY. MOST OF THE RIVER LEVELS HAVE CRESTED, AND WITH A
PROLONGED STRETCH OF DRY WEATHER ANTICIPATED THROUGH THURSDAY,
WATER LEVELS SHOULD GRADUALLY SUBSIDE THROUGH THE WEEK.
THOSE LIVING NEAR RIVERS SHOULD CONTINUE TO MONITOR THE LATEST
FLOOD WARNINGS AND STATEMENTS FROM THE NATIONAL WEATHER SERVICE
IN GREEN BAY.
SEE THE DISCUSSION SECTION ABOVE FOR INFORMATION PERTAINING TO
PRECIPITATION FORECASTS FOR THE THURSDAY TO FRIDAY PERIOD.
GRB WATCHES/WARNINGS/ADVISORIES
NONE.
DISCUSSION.....GK
AVIATION.......ECKBERG
HYDROLOGY......GK
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