214
FXUS63 KGRR 201753
AFDGRR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GRAND RAPIDS MI
153 PM EDT MON JUL 20 2026
KEY MESSAGES
- THUNDERSTORMS TONIGHT WITH DAMAGING WINDS POSSIBLE
- DRY AND COOLER MID TO LATE WEEK
DISCUSSION
ISSUED AT 237 AM EDT MON JUL 20 2026
- THUNDERSTORMS TONIGHT WITH DAMAGING WINDS POSSIBLE
PRIMARY CONCERN WITH THIS FORECAST PACKAGE IS FOR THE POTENTIAL OF
SEVERE THUNDERSTORMS TONIGHT. A COLD FRONT LOOKS TO TRIGGER STORMS
ACROSS THE UPPER MIDWEST THIS AFTERNOON WHICH PROGRESSES EASTWARD
MONDAY EVENING. QUESTIONS REMAIN AS TO THE STRENGTH OF ANY
CONVECTION, WITH TIMING FAVORED TO BE LATE THIS EVENING INTO THE
EARLY OVERNIGHT HOURS.
EVALUATION OF FORECAST PROFILES SUGGESTS THE POTENTIAL FOR AN MCS ON
THE NOSE OF A 40 KT LLJ, WITH STRONG LOW-LEVEL AND DEEP LAYER SHEAR.
THIS LENDS ITSELF TO A PRIMARY THREAT OF DAMAGING WINDS, WITH LARGE
HAIL IN ANY DISCRETE CONVECTION GIVEN STEEP MID-LEVEL LAPSE RATES.
INSTABILITY LOOKS TO BE SUFFICIENT AS WELL (ALBEIT WANING WITH
EASTWARD EXTENT), SO EVEN WITH UNCERTAINTIES AS TO CONVECTIVE
STRENGTH, THE ENVIRONMENT WARRANTS THE SLIGHT (LEVEL 2/5) RISK IN
PLACE ACROSS MOST OF THE CWA. THE THREAT ENDS TUESDAY MORNING AS THE
COLD FRONT EXITS THE CWA.
- DRY AND COOLER MID TO LATE WEEK
TUESDAY THROUGH LATE WEEK WILL FEATURE A RELATIVELY STABLE PATTERN
WITH PERSISTENT UPPER-LEVEL TROUGHING AND SURFACE RIDGING ACROSS THE
AREA. COMBINED WITH THE DRY AIRMASS, DRY CONDITONS ARE FAVORED AT
THIS POINT. LOOK FOR HIGHS IN THE 70S MID-WEEK CLIMBING BACK INTO
THE LOW 80S BY THE WEEKEND.
AVIATION /18Z TAFS THROUGH 18Z TUESDAY/
ISSUED AT 153 PM EDT MON JUL 20 2026
A FEW AREAS OF MVFR SMOKE VISIBILITY REMAIN BUT GRADUAL
IMPROVEMENT HAS BEEN OCCURRING. OTHERWISE, CLOUD BASES ARE
EXPECTED TO BE AT OR ABOVE 4,000 FEET THIS AFTERNOON WITH
SOUTHWEST WINDS. THUNDERSTORMS FROM WISCONSIN ARE EXPECTED TO
CROSS LAKE MICHIGAN INTO WESTERN LOWER MICHIGAN LATE THIS
EVENING. MODELS DIFFER ON HOW FAR EAST THE STORMS WILL EXTEND
INTO LOWER MICHIGAN TONIGHT. FOR NOW, WILL CONTINUE PROB30
THUNDERSTORMS ESPECIALLY BETWEEN 01 AND 08 Z. HEAVY RAIN WITH IFR
VISIBILITY, AND STRONGER WIND GUSTS OVER 35 KNOTS OR LLWS ARE
FAVORED TO BE ASSOCIATED WITH STORMS IF THEY DO OCCUR.
MARINE
ISSUED AT 237 AM EDT MON JUL 20 2026
WINDS AND WAVES INCREASE THIS MORNING AHEAD OF A COLD FRONT WITH 3-6
FOOT WAVES BUILDING BY THIS AFTERNOON. WINDS VEER NORTHWESTERLY
TUESDAY BEHIND A COLD FRONT WITH WAVES TO 5-8 FEET. WINDS OF 20-30
KNOTS ARE EXPECTED WITH A 40% CHANCE OF GALE FORCE GUSTS TUESDAY
EVENING. HAZARDOUS WINDS AND WAVES CONTINUE INTO WEDNESDAY EVENING.
WILL HOIST A SMALL CRAFT ADVISORY AND BEACH HAZARDS STATEMENT FOR
THIS MULTI DAY HAZARDOUS WIND AND WAVE EVENT. IN ADDITION,
THUNDERSTORMS, THE STRONGEST OF WHICH MAY HAVE WINDS IN EXCESS OF 34
KNOTS, ARE POSSIBLE THIS EVENING ACROSS THE NEARSHORE AND OPEN
WATERS.
GRR WATCHES/WARNINGS/ADVISORIES
MI...AIR QUALITY ALERT UNTIL MIDNIGHT EDT TONIGHT FOR MIZ037>040-
043>046-050>052-056>059-064>067-071>074.
BEACH HAZARDS STATEMENT THROUGH WEDNESDAY EVENING FOR MIZ037-043-
050-056-064-071.
MARINE...SMALL CRAFT ADVISORY UNTIL 11 PM EDT WEDNESDAY FOR LMZ844>849.
DISCUSSION...THOMAS
AVIATION...CAS
MARINE...THOMAS
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