074
FXUS63 KDTX 150806
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
406 AM EDT FRI AUG 15 2025
KEY MESSAGES
- WARMER AND DRY TODAY WITH HIGHS IN THE UPPER 80S.
- HEAT AND HUMIDITY RETURN THIS WEEKEND AS HEAT INDICES PEAK IN THE
UPPER 90S SATURDAY AFTERNOON.
- CHANCE OF THUNDERSTORMS SATURDAY THROUGH SUNDAY MORNING WITH AN
ISOLATED SEVERE STORM POSSIBLE SATURDAY AFTERNOON-EVENING.
- COOLER AND LESS HUMID EARLY NEXT WEEK.
DISCUSSION
PATCHY FOG IS OBSERVED THIS MORNING ACROSS THE SAGINAW VALLEY AND
THUMB REGIONS WHERE EASTERLY FLOW OFF OF LAKE HURON HAS LOCALLY
ENHANCED BOUNDARY LAYER MOISTURE. SHOULD HAVE NO PROBLEM MIXING THIS
OUT ONCE SOLAR HEATING RAMPS UP. LOW AMPLITUDE SHORTWAVE IS NOTED
OVER WISCONSIN AT ISSUANCE, AND WILL SLOWLY SHIFT EAST THROUGHOUT
THE DAY BRINGING AN INCREASE IN MID CLOUD ACROSS CENTRAL LOWER
MICHIGAN THROUGHOUT THE DAY. AIRMASS MODIFICATION AND EMERGING
SOUTHERLY FLOW PUSH HIGHS INTO THE UPPER 80S TODAY.
LOW PREDICTABILITY HEADING INTO THE SATURDAY FORECAST, WITH SEVERAL
WINDOWS OF OPPORTUNITY FOR CONVECTION, BUT LOW CONFIDENCE IN EACH.
THE FIRST OF THESE BEGINS LATE TONIGHT AS A NOCTURNAL MCS DEVELOPS
ALONG A COLD FRONT THAT IS SET TO DROP THROUGH THE GREAT LAKES LATER
THIS WEEKEND. FAMILIAR SETUP EXISTS WHERE THE MCS WILL RIDE THE
INSTABILITY GRADIENT AND EITHER CLIP SE MICHIGAN SATURDAY MORNING,
OR GENERATES SUBSIDENCE AND EATS INTO THE INSTABILITY THAT WE RELY
ON FOR LATER DAY CONVECTION. SHOULD INSTABILITY BE ABLE TO REBOUND
SUFFICIENTLY BY THE AFTERNOON-EVENING TIMEFRAME, A COUPLE OF DEFINED
PERTURBATIONS ALOFT COMBINE WITH DIFFERENTIAL HEATING AT THE SURFACE
TO SUPPORT A SECOND WINDOW OF THUNDERSTORM POTENTIAL. SWODY2 KEEPS
THE MARGINAL RISK WEST OF OUR FORECAST AREA, BUT THERE ARE SOME
ENVIRONMENTAL SIGNATURES FOR STRONG DOWNDRAFT POTENTIAL. FOR
EXAMPLE, HRRR/RAP SOUNDINGS SHOW INVERTED-V SOUNDINGS WITH SFC-3KM
AGL LAPSE RATES OF 8.5-9.0 C/KM WHILE INCREASING MID-LEVEL WINDS
LATE IN THE DAY COULD SUPPORT ORGANIZED CELLS.
THE OTHER FORECAST POINT FOR SATURDAY IS THE RETURN OF WARM AND
MUGGY CONDITIONS. FORECAST HIGHS ON SATURDAY AROUND 90 DEGREES BRING
HEAT INDICES INTO THE MID-90S, ALTHOUGH CONVECTIVE CLOUD DEBRIS
AND/OR DISRUPTION TO MOISTURE TRANSPORT COULD SUPPRESS WARMING
SIGNIFICANTLY.
BY SATURDAY EVENING, THE COLD FRONT WILL BEGIN SETTLING ACROSS LOWER
MICHIGAN. THE DETERMINISTIC RUNS ARE FAIRLY LEAN ON PRECIPITATION
COVERAGE OVERNIGHT-SUNDAY MORNING, BUT GIVEN THE DEFINED FORCING AND
PLENTIFUL MOISTURE (PWATS NEAR 1.8"), THOUGHTS ARE MUCH MORE IN LINE
WITH THE BULK OF ENSEMBLE MEMBERS FROM THE EPS/GEFS/CMCE WHICH KEEPS
SHOWER/THUNDERSTORM CHANCES GOING THROUGH AT LEAST SUNDAY MORNING.
MODELS DISAGREE ON THE PACE OF THE FRONT, WITH SOME STALLING THE
BOUNDARY OVERHEAD ON SUNDAY TO KEEP RAIN CHANCES AROUND FOR THE
DAYTIME HOURS AS WELL. THE FORECAST FROM SUNDAY THROUGH EARLY NEXT
WEEK WILL BE HIGHLY SENSITIVE TO THE POSITIONING OF THIS FRONTAL
BOUNDARY, AND WILL LIKELY SEE A GRADIENT IN BOTH TEMPERATURE AND
PRECIPITATION CHANCES ACROSS THE CWA. PRECIPITATION IS LIKELY TO
FLARE UP AT TIMES ALONG THE FRONTAL ZONE, LEADING TO UNSETTLED
CONDITIONS AND POTENTIAL FOR HEAVY RAINFALL TO START THE WORK WEEK.
THE WPC EXCESSIVE RAINFALL OUTLOOK HIGHLIGHTS ALL OF SE MICHIGAN IN A
BROAD MARGINAL RISK FOR MONDAY-TUESDAY. OTHERWISE, COOLER CONDITIONS
ARE EXPECTED NEXT WEEK.
MARINE
HIGH PRESSURE OVER EASTERN QUEBEC THIS MORNING, LEADING TO LIGHT
SOUTHERLY FLOW (MOSTLY UNDER 20 KNOTS) TODAY. CONTINUED LOW LEVEL
WARMING INTO SATURDAY AHEAD OF A COLD FRONT SHOULD CAP WIND SPEEDS
IN THE 15 TO 20 KNOT RANGE. INCREASING CHANCE OF SHOWERS AND
THUNDERSTORMS SATURDAY EVENING AS COLD FRONT ENTERS THE REGION.
SCATTERED-NUMEROUS SHOWERS AND THUNDERSTORMS SHOULD BE AROUND
SATURDAY NIGHT INTO SUNDAY AS THE FRONT DRIVES SOUTH. SOLID COLD
ADVECTION (850 MB TEMPS LOWERING INTO LOWER TEENS/AROUND 10 C) OVER
LAKE HURON ON SUNDAY WILL ALLOW NORTHEAST WINDS TO REACH 20-25
KNOTS, WITH THE POTENTIAL FOR WINDS TO BRIEFLY GUST TO AROUND 30
KNOTS. EVEN IF WINDS COME UP A BIT SHORT, THE PROLONG NORTHEAST
WINDS WILL LIKELY ALLOW WAVES TO BUILD AROUND 4 FEET ACROSS THE
NEARSHORE WATERS, AS EASTERLY WINDS PERSIST INTO EARLY NEXT WEEK
WITH ANOTHER STRONG HIGH PRESSURE SYSTEM DEVELOPING OVER EASTERN
CANADA.
PREV DISCUSSION
ISSUED AT 1109 PM EDT THU AUG 14 2025
AVIATION...
VFR SKIES EXPECTED THROUGH THE TAF PERIOD AS HIGH PRESSURE SLIDES
THROUGH THE CENTRAL GREAT LAKES INTO THE EASTERN GREAT LAKES/NEW
ENGLAND REGION. THIS LEADS TO A LIGHT WIND BECOMING MORE SOUTHERLY
THIS THE MORNING TO AROUND 5 KNOTS. MOSTLY CLEAR SKIES ASIDE FROM A
FEW TO SCATTERED MID CLOUDS EARLY THIS MORNING WITH THE STANDARD VFR
DIURNAL CUMULUS DURING THE AFTERNOON SUPPORTED BY SOME LINGERING MID
LEVEL MOISTURE.
FOR DTW/D21 CONVECTION...NO THUNDERSTORMS EXPECTED THROUGH THIS TAF
PERIOD.
THRESHOLD PROBABILITIES...
* LOW FOR CEILINGS AT OR BELOW 5 KFT DURING THE AFTERNOON.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
DISCUSSION...MV
MARINE.......SF
AVIATION.....AA
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