425
FXUS63 KGRR 012330
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
730 PM EDT WED JUL 1 2026
KEY MESSAGES
- SEVERAL ROUNDS OF SHOWERS AND STORMS THROUGH TOMORROW NIGHT
- HOT AND HUMID THROUGH THE WEEK; LESS HUMID THROUGH WEEKEND
DISCUSSION
ISSUED AT 151 PM EDT WED JUL 1 2026
- SEVERAL ROUNDS OF SHOWERS AND STORMS THROUGH TOMORROW NIGHT
AN ACTIVE STORM PATTERN CONTINUES THROUGH THURSDAY EVENING. A
ROUND OF SHOWERS AND STORMS HAS ALREADY MOVED THROUGH THE NORTHERN
HALF OF THE LOWER PENINSULA EARLY TODAY. SOME OF THESE STORMS WERE
SEVERE. MORE STORMS ARE MOVING THROUGH CENTRAL WI. THE QUESTION IS
IN WHICH DIRECTION WILL THEY GO. THE EARLY CONVECTION HAS COOLED
OFF TEMPERATURES WHICH HAS BROUGHT STABILITY TO NORTHERN LOWER.
THIS WILL STIFLE ANY INCOMING CONVECTION FROM THE WEST. THERE IS
ALSO A SIGNIFICANT CAP OVER THE AREA WHICH WILL WEAKEN ANY STORMS
MOVING INTO IT. THE LOW LEVEL JET HAS SHIFTED SO THERE IS A
WEAKER AMOUNT OF SHEAR.
THAT SAID, A BOUNDARY WILL ADVECT FROM THE WEST BRINGING ANOTHER
CHANCE FOR SHOWERS AND STORMS LATE TODAY INTO EARLY MORNING
TOMORROW. THERE IS SOME QUESTION IF THERE WILL BE ENOUGH
INSTABILITY FOR STORMS TO FORM. SEVERAL MORE WAVES OF INSTABILITY
SHOULD MOVE THROUGH THIS AFTERNOON AND EVENING WHICH COULD BRING
SHOWERS AND STORMS FURTHER SOUTH.
A STRONG 850 MB 35 TO 40 KT LLJ WILL MOVE OVER THE REGION
BETWEEN 06Z TO 10Z THURSDAY. THAT SHEAR ALOFT, COUPLED WITH ANY
WARM, MOIST AIR COULD BE ENOUGH TO AT THE VERY LEAST SPARK SOME
ELEVATED STORMS, IF NOT ALLOW FOR GUSTS TO MIX TO THE SURFACE.
HREF CONTINUES TO SHOW 1000 J/KG OF UNSTABLE CAPE OVERNIGHT. THAT
CAPE AND THE SHEAR PROVIDED COULD SUSTAIN CONVECTION INTO THURSDAY
MORNING, WITH DAMAGING WINDS POSSIBLE.
AFTER ANY SHOWERS AND STORMS THURSDAY MORNING THERE COULD BE A
SIGNIFICANT PAUSE FROM ANY SHOWERS AS ANOTHER CAP FORMS. ANOTHER
LLJ ALONG WITH SIGNIFICANT CAPE WILL MOVE OVER THE AREA LATE
THURSDAY. ONCE AGAIN, THE MAIN CONCERN IS WHETHER OR NOT THERE IS
ENOUGH FORCING TO BRING SEVERE WEATHER. THE BEST CHANCE WILL BE
LATER IN THE DAY. WHILE THE DIURNAL CONVECTION WEAKENS, THERE IS
ALSO SLIGHTLY BETTER FORCING AND A WEAKER LOW LEVEL INVERSION
WHICH COULD THEN ALLOW STORMS TO SPARK LATE IN THE DAY. IF ANY
STORMS SPARK THERE WILL BE AROUND 35KTS OF SHEAR AND POTENTIALLY
OVER 2K J/KG OF CAPE. THAT COULD FUEL SEVERE WEATHER TOMORROW
EVENING THAT HAS THE POTENTIAL TO PERSIST INTO EARLY FRIDAY.
- HOT AND HUMID THROUGH THE WEEK; LESS HUMID THROUGH WEEKEND
THE HOT AND HUMID WEATHER CONTINUES AS AN UPPER LEVEL HIGH
REMAINS OVER THE EASTERN US. IT WILL CONTINUE TO ADVECT THE HOT
AND HUMID AIR OVER THE REGION THROUGH THE END OF THE WEEK. HEAT
INDICES UPWARDS OF 105 REMAIN LIKELY THROUGH THURSDAY WITH HEAT
INDICES TOUCHING 100 ON FRIDAY. THE UPPER LEVEL RIDGE WILL
FLATTEN, WHICH WILL WEAKEN THE FLOW. SO WHILE HOT SUMMERTIME AIR
WILL REMAIN THROUGH THE WEEKEND, THE HUMIDITY AND THE INTENSITY OF
THE TEMPS WILL SLACKEN. SO WHILE TEMPERATURES WILL CONTINUE TO BE
IN THE UPPER 80S TO LOW 90S THROUGH THE WEEKEND AND INTO NEXT
WEEK, THE DEWPOINTS WILL BE INTO THE 60S. A SUMMERTIME PATTERN
WILL PERSIST THROUGH NEXT WEEK.
AVIATION /00Z TAFS THROUGH 00Z FRIDAY/
ISSUED AT 730 PM EDT WED JUL 1 2026
PROBABILITY OF VFR THROUGH 06Z:
GRR/AZO/BTL/LAN/JXN -- 95 PERCENT
MKG -- 80 PERCENT
MAIN CHANGE TO THIS UPDATE WAS TO REMOVE PROB30 FOR PRECIPITATION
AFTER 06Z AT SOME OF THE TERMINALS. THIS IS BASED ON RADAR, SATELLITE
AND MODEL TRENDS. THERE IS AN ESTIMATED 10 PERCENT CHANCE FOR A
SHOWER OR THUNDERSTORM FOR MKG TOWARDS 06Z, BUT THIS IS TOO LOW TO
MENTION EXPLICITLY IN THE TAFS.
WINDS ARE SUBSIDING QUICKLY WITH GUSTS EXPECTED TO BE GONE
AREAWIDE AROUND OR SHORTLY AFTER 00Z THIS EVENING. ALTHOUGH WE
INCLUDED A SCATTERED LAYER OF CUMULUS/STRATOCUMULUS FOR MUCH OF
TONIGHT, COMPLETELY CLEAR SKIES ARE ALSO HIGHLY PLAUSIBLE.
MARINE
ISSUED AT 250 PM EDT WED JUL 1 2026
AT THIS TIME HAVE DECIDED TO HOLD OFF ON A SMALL CRAFT ADVISORY
AND BEACH HAZARDS STATEMENT FOR MAINLY TONIGHT, BUT IT WILL BE
CLOSE TO CRITERIA NORTH OF GRAND HAVEN. EXPECT THAT IT WILL
INCREASE OVERNIGHT TOWARD SUNRISE. IT LOOKS TO BE TRENDING
TOWARDS A TYPICAL SUNRISE SURPRISE TYPE OF EVENT. IN THESE EVENTS,
THE OVERNIGHT LOW LEVEL JET AIDES IN DEVELOPING SURFACE WINDS
THAT IN TURN BUILDS A WAVE FIELD. THE WAVES LOOK TO BE LIKELY 2-4
FEET WITH CHANCES INCREASING FOR 3-5 FOOTERS. GIVEN THIS IS AN
INCREASE AND ITS BORDERLINE WILL HOLD OFF FOR NOW, BUT MARINERS
CAN EXPECT SOME CHOPPY CONDITIONS EARLY THURSDAY MORNING NORTH OF
GRAND HAVEN. CONDITIONS LOOK TO BE BELOW ADVISORY LEVELS LATER
THURSDAY AND INTO FRIDAY. THE OUTLOOK FOR THE HOLIDAY WEEKEND ON
THE BIG LAKE LOOKS GOOD AT THIS POINT WITH LIGHTER WINDS AND LOWER
WAVE CONDITIONS TYPICAL OF MID SUMMER.
GRR WATCHES/WARNINGS/ADVISORIES
MI...EXTREME HEAT WARNING UNTIL 8 PM EDT THURSDAY FOR MIZ037>040-
043>046-050>052-056>059-064>067-071>074.
MARINE...NONE.
DISCUSSION...CERU
AVIATION...TJT
MARINE...CERU
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