744
FXUS63 KDTX 131850
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
250 PM EDT MON JUL 13 2026
KEY MESSAGES
- HEAT BUILDS DURING THE EARLY HALF OF THE WEEK WITH HIGHS IN THE
MID TO UPPER 90S THROUGH WEDNESDAY.
- PEAK HEAT EXPECTED TUESDAY WITH HIGHS IN THE UPPER 90S AND HEAT
INDICES NEAR OR ABOVE 100 DEGREES. A HEAT ADVISORY HAS BEEN
ISSUED FOR ALL OF SOUTHEAST MICHIGAN NOON TO 8PM TUESDAY.
- POTENTIAL FOR SHOWERS AND THUNDERSTORMS EXISTS LATE IN THE WEEK
INTO NEXT WEEKEND.
DISCUSSION
MID-UPPER RIDGING ACROSS THE NORTH-CENTRAL PLAINS HAS BEGUN THE
PROCESS OF FOLDING INTO THE CENTRAL GREAT LAKES TODAY SUPPORTING
WIDESPREAD HIGHS IN THE LOWER 90S. A NOTABLE UPTICK IN HUMIDITY
ACCOMPANIES THIS AIRMASS AS THE RESIDENT UPPER 50-LOWER 60 DEWPOINTS
ARE REPLACED BY UPPER 60S-LOWER 70S PUSHING HEAT INDEXES FIRMLY INTO
THE MID/UPPER 90S. THIS ALSO LEADS RESULTANT OVERNIGHT LOWS TO ONLY
FALL TO AROUND 70.
600DAM RIDGE AXIS IS FULLY FOLDED INTO SOUTHERN LOWER MI DRAWING THE
CORE OF THE UPPER PLAINS HEAT DOME OVERHEAD WITH LOCAL 850MB TEMPS
MAKING A RUN NEAR 25C BY LATE MORNING. ACTIVE SUBSIDENCE COMBINED
WITH ELEVATED WARM ADVECTION SETS UP A STRONG INVERSION BETWEEN 4-
6KFT FIRMLY CAPPING THE REGION FOR ANY POP-UP CONVECTION. MAIN
UPDATE WITH THIS FORECAST PACKAGE WAS TO FLIP THE CURRENT EXTREME
HEAT WATCH TO A HEAT ADVISORY FOR TUESDAY AFTERNOON-EVENING. WHILE
THE NBM CONTINUES TO REMAIN BULLISH ON HIGHS IN THE LOW 100S, LOCAL
PROBABILISTIC GUIDANCE HAS BEEN MORE MUTED INSTEAD FAVORING UPPER
90S WHICH SHIFTS PEAK HEAT INDICES FROM THE MID 100S TO CLOSER TO
100-105 RANGE. GIVEN THE PERFORMANCE FROM EARLIER HEAT WAVES THIS
SUMMER, AM SKEPTICAL OF THE MAGNITUDE OF THE NBM ACTUAL/APPARENT
TEMPERATURES ESPECIALLY AS DIVING INTO HISTORICAL CLIMO DATA FOR
DTW/FNT/MBS ONLY SHOWS THE SITES HITTING WARNING CRITERIA (105F HEAT
INDEX) 15-19 DAYS SINCE 2000. WHILE CAN'T RULE OUT A FEW LOCATIONS
WITHIN THE SAGINAW VALLEY OR METRO DETROIT TOUCHING 105F HEAT
INDICES, NOT EXPECTING THE 3 HOUR DURATION TO WARRANT A WARNING OVER
AN ADVISORY.
STILL HOT AGAIN WEDNESDAY THOUGH WITH THE MID-LEVEL RIDGE AXIS NOW
DIRECTED INTO THE OHIO VALLEY BY THIS POINT, THE CORE OF THE AIRMASS
IS LIKEWISE SHIFTED TOWARDS NORTHERN OH/FAR SOUTHERN SE MI. AREAS
SOUTH OF M-59 LIKELY STILL SEE HIGHS IN THE UPPER 90S WITH AREAS
NORTH FALLING CLOSER TO THE MID 90S AS A WEAK COLD FRONT SAGS SOUTH.
IN A SIMILAR VEIN TO TUESDAY, SOME OF THESE SOUTHERNMOST LOCALES
COULD SEE HEAT INDICES TOUCH 105, HOWEVER DURATION IS EXPECTED TO
FALL SHORT WITH 100-105 FORECAST TO BE PREDOMINANT. FOR AREAS, NORTH
HEAT INDICES LOOKING TO TOP OUT AROUND THE 95-100 DEGREE RANGE. AT
LEAST PORTIONS OF THE CWA WILL REQUIRE ANOTHER HEAT ADVISORY HOWEVER
WILL TAKE HEADLINES DAY BY DAY.
LATE WEEK IS MARKED BY CONTINUING SOUTHWARD COMPRESSION OF THE MID-
LEVEL RIDGE BY TROUGHING ACROSS THE HUDSON BAY/EASTERN CANADA. SE MI
LOOKING TO RESIDE ON THE NORTHEAST FRINGE WHICH OFFERS A CHANCE AT
NEAR ADVISORY HEAT INDICES, AT LEAST FOR URBAN AREAS, THOUGH ALSO
BEGINS TO OPEN THE DOOR FOR EMBEDDED SHORTWAVES TO CLIP THE REGION
PARTICULARLY FRIDAY INTO THE WEEKEND AS RIDGING BREAKS DOWN AND
CYCLONIC RETURN FLOW DEVELOPS. ANY POTENTIAL CONVECTION/MCS TRACKS
ARE HIGHLY DEPENDENT ON THE EXACT COMPRESSION OF THE RIDGE WHICH
CARRIES LOW CONFIDENCE THIS FAR OUT.
MARINE
HOT AIRMASS (850 MB TEMPS IN THE MID-TWENTIES) WILL TRACK INTO THE
CENTRAL GREAT LAKES FROM THE NORTHWEST THROUGH TOMORROW, LEADING TO
STABLE LOW LEVEL PROFILES. THIS SHOULD HOLD THE MAX WESTERLY WINDS
IN THE 20 TO 25 KNOT RANGE, WITH THE HIGHEST WINDS ACROSS NORTHERN
THIRD OF LAKE HURON DUE TO THE CHANNELING THROUGH THE STRAITS. A
MAINLY DRY BACKDOOR COLD FRONT DROPPING SOUTH TUESDAY NIGHT INTO
WEDNESDAY WILL ALLOW WINDS TO VEER TO THE NORTHWEST BEHIND THE
FRONT, BUT STILL ONLY TOPPING OUT AROUND 20 KNOTS WEDNESDAY EVENING
OVER THE NORTH HALF OF LAKE HURON. NORTHWEST WINDS AT OR BELOW 20
KNOTS HOLDS ON THURSDAY. THE FORECAST ON FRIDAY AND SATURDAY
UNRAVELS DUE TO CONFLICTING MODEL GUIDANCE REGARDING THE LOCATION
AND MAGNITUDE OF A SURFACE LOW MOVING THROUGH THE GREAT LAKES
REGION. THIS HAS SIGNIFICANT IMPACT NOT ONLY ON WIND SPEEDS, BUT
ALSO ON WIND DIRECTION, ALONG WITH BRINGING CHANCES OF SHOWERS AND
THUNDERSTORMS.
PREV DISCUSSION
ISSUED AT 101 PM EDT MON JUL 13 2026
AVIATION...
HIGH PRESSURE IS ENTRENCHED OVERHEAD WITH A RIDGE ALOFT ALLOWING DRY
WEATHER AND VFR TO PERSIST THROUGH THE TAF PERIOD. LIGHT WINDS
GENERALLY OUT OF THE SOUTHWEST HOLD THROUGH TUESDAY, WITH THE
EXCEPTION OF DET WHERE LAKE BREEZE DEVELOPMENT CAUSES WIND DIRECTION
TO BACK SE LATE AFTERNOON-EARLY EVENING.
D21/DTW CONVECTION...NO THUNDERSTORMS ARE FORECAST.
DTW THRESHOLD PROBABILITIES...
* NONE.
DTX WATCHES/WARNINGS/ADVISORIES
MI...HEAT ADVISORY FROM NOON TO 8 PM EDT TUESDAY FOR MIZ047>049-053>055-
060>063-068>070-075-076-082-083.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
DISCUSSION...KDK
MARINE.......SF
AVIATION.....MV
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page