591
FXUS63 KAPX 040925
AFDAPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
525 AM EDT FRI SEP 4 2026
KEY MESSAGES
- RAIN/STORMS TODAY INTO SATURDAY MORNING, WITH IMPROVING
CONDITIONS FOR THE REST OF THE HOLIDAY WEEKEND. LOCALIZED
FLOODING POSSIBLE TODAY.
DISCUSSION
ISSUED AT 237 AM EDT FRI SEP 4 2026
PATTERN SYNOPSIS/FORECAST:
BROAD UPPER LOW OVER THE PACNW WITH PV MAX SWIRLING NORTHWARD
THROUGH ALBERTA...AND A FLAT BUT NEGATIVELY TILTED TROUGH AXIS
STRETCHING FROM HERE TO MN/WI AT 4Z...ALONG/AHEAD OF WHICH
CONVECTION CONTINUES TO FIRE. BULK OF THE MOISTURE ACROSS THE CONUS
REMAINS ACROSS THE EASTERN US, PARTICULARLY FROM THE GULF COAST UP
INTO THE UPPER MIDWEST AND GREAT LAKES (PWAT OF 1.56 IN ON OUR 0Z
SOUNDING). SOME WEAKER STABILITY JUST UPSTREAM FROM US OVER THE
UPPER MIDWEST, AIDING IN UPSTREAM CONVECTIVE ACTIVITY ON THE NOSE OF
A 30KT LLJ STRETCHING FROM THE PLAINS INTO MN/WI...INTERACTING WITH
THAT BAROCLINIC ZONE STILL STRETCHED OUT OVER THE REGION; CURRENTLY
HAVE A COUPLE LOW-LEVEL THETA-E GRADIENTS TO CONTEND WITH...ONE
STRETCHING FROM CENTRAL WI INTO SOUTHERN MI, WHERE CONVECTION IS
CURRENTLY BLOWING UP OVER SE WI WHERE TDS ARE IN THE LOW-MID 70S
(THIS ONE IS ASSOCIATED WITH THE SURFACE STATIONARY BOUNDARY
STRETCHING FROM MN TO MKE THROUGH CENTRAL MI AND TOWARD PORT HURON;
AND ANOTHER STRETCHING FROM THE TIP OF MN INTO THE M-72 CORRIDOR
HERE IN NORTHERN MI (TDS SOUTH IN THE 60S, NORTH OF THIS, IN THE
50S). NOTICE SOME NORTHWARD PROPAGATING LINES OF CONVECTION ATTM AND
SUSPECT THESE ARE LIKELY RELATED TO GRAVITY WAVES.
EXPECT ONGOING CONVECTION TO CONTINUE TO TRACK ACROSS THE AREA EARLY
THIS MORNING; THINK THE BULK OF THE ACTIVITY WILL TRACK ACROSS THE
AREA ESPECIALLY AFTER 12Z, WITH THE WORST CONDITIONS ACROSS THE
SOUTHERN HALF OF THE AREA, THOUGH THINK THE EUP WILL NOT GO
UNTOUCHED TODAY, ESPECIALLY THIS MORNING. BOUNDARY/DEFORMATION AXIS
TO REMAIN IN THE AREA THROUGH THE DAY INTO THE OVERNIGHT HOURS, WITH
POTENTIAL FOR RAIN/STORMS TO REMAIN IN THE REGION INTO SATURDAY
MORNING...WITH IMPROVEMENTS LIKELY THROUGH THE DAY AS WE START TO
TAP INTO SOME DRIER AIR AND INCREASING SUBSIDENCE. HIGH PRESSURE
SHOULD BE IN CONTROL OF OUR WEATHER FOR SUNDAY, WITH RETURN FLOW
STRENGTHENING ACROSS THE PLAINS/MS VALLEY MONDAY INTO MONDAY
NIGHT...AS NEXT SYSTEM MARCHES INTO CENTRAL CANADA. ATTM, THE
PRESSURE GRADIENT BETWEEN THIS AND HUDSON BAY HIGH LOOKS TO INCREASE
OVER THE CANADIAN PRAIRIES AND PERHAPS PARTS OF THE UPPER MIDWEST,
AND THINK WE COULD BE LOOKING AT SOME SLIGHTLY STRONGER FLOW GOING
INTO THE MIDDLE OF NEXT WEEK...ALONG WITH POTENTIAL FOR MORE
SHOWERS/STORMS, PERHAPS INTO THE LATTER HALF OF NEXT WEEK, THOUGH
THERE IS INCREASING UNCERTAINTY IN THE EVOLUTION OF THE SYSTEM
MARCHING ACROSS SOUTHERN CANADA.
FORECAST DETAILS...
HEAVY RAIN/STORM CONCERNS TODAY...STILL LOOKING AT PWATS AT OR ABOVE
1.5-2IN IN THE REGION TODAY WITH THAT BOUNDARY/DEFORMATION AXIS
PRESENT, AND WORRY THAT SOME AREA WILL GET A SWATH OF 1-3IN AGAIN,
PARTICULARLY IF ANY TRAINING DEVELOPS. HAVE CONCERNS THIS COULD
AGAIN IMPACT AREAS SOUTH OF M-72, WHICH SAW AT LEAST AN INCH OF RAIN
YESTERDAY (PARTS OF MANISTEE COUNTY, CLOSER TO 3-4IN), AND THIS
WOULD HEIGHTEN FLASH FLOODING CONCERNS. (APPEARS THE MANISTEE RIVER
BASIN IS RUNNING AT CLIMATOLOGICALLY HIGH FLOWS FOR THIS TIME OF
YEAR...AND ALL THE GAUGES ARE UPSTREAM OF THE HEAVIEST SWATH OF RAIN
FROM YESTERDAY.) DEEP LAYER SHEAR REMAINS IN PLAY TODAY, AND COULD
BE SOMEWHAT PERPENDICULAR TO THE BOUNDARY, SUGGESTING THERE IS A
CHANCE FOR SOME FEISTIER STORMS AT TIMES, PARTICULARLY TOWARD NW
LOWER MI (AGAIN) BUT ESPECIALLY POINTS SOUTH AND WEST, WHERE THERE
IS A BETTER CHANCE AT STAYING A LITTLE MORE UNSTABLE THAN UP HERE.
(NOT TO MENTION WE STILL EXPECT EASTERLY LOW-LEVEL FLOW TO ENHANCE
LOW-LEVEL SHEAR/SPIN.) STILL HAVE SOME CONCERNS FOR WATER LEVEL
FLUCTUATIONS IN THE ST. MARY'S RIVER SYSTEM, ALTHOUGH THE CURRENT
CONVECTIVE COMPLEXES AREN'T MOVING TERRIBLY FAST (AND PRESSURE
PERTURBATIONS SEEM TO BE MORE NOTABLE TOWARDS LAKE MI ATTM WITH THE
CONVECTION OVER WI)...BUT WILL KEEP AN EYE ON THIS, TOO.
STILL GOTTA WONDER ABOUT STORMS (OR AT LEAST RAIN) HANGING ON
TONIGHT INTO SATURDAY MORNING; DEFORMATION AXIS WITH SOME BROAD
LOW/MID-LEVEL FORCING AND PLUME OF LOW-LEVEL MOISTURE REMAIN IN
PLACE ACROSS THE REGION, WITH AT LEAST A FEW HUNDRED JOULES OF
INSTABILITY IN PLAY, ESPECIALLY DURING THE MORNING HOURS; COOLER AIR
SNEAKING IN IN THE LOWER LEVELS SHOULD SUPPORT A CAP DEVELOPING
ALOFT THROUGH THE DAY, WHICH SHOULD FURTHER LIMIT INSTABILITY (SAVE
FOR PERHAPS A BIT OF DIURNAL INSTABILITY TO THE INVERSION AND
PERHAPS STRATOCU). DEEP LAYER SHEAR DOES REMAIN AROUND 25-35KTS IN
THE REGION INTO SATURDAY MORNING, TOO, BUT MAY NOT BE COLLOCATED
WELL WITH THE BEST INSTABILITY. TEMPS ALOFT SATURDAY LOOK TO FALL
BACK BELOW 12C AND COULD THEREFORE SUPPORT A TINY BIT OF OVERLAKE
INSTABILITY/SHOWER ACTIVITY, THOUGH ON NE FLOW.
AVIATION /12Z TAFS THROUGH 12Z SATURDAY/
ISSUED AT 525 AM EDT FRI SEP 4 2026
PATCHY FOG WILL DISSIPATE THROUGH THE MORNING, WITH CHANCES FOR
SHOWERS/ THUNDERSTORMS CONTINUING THROUGH TODAY. HEAVY RAINFALL
MAY CAUSE REDUCED VISIBILITIES AND LOCALIZED FLOODING,
ESPECIALLY ACROSS MBL AND TVC. MAINLY VFR CONDITIONS EXPECTED BY
THE AFTERNOON (EXCEPT TVC AND MBL AT MVFR IMPROVING EARLY
TONIGHT TO VFR) WITH GENERALLY LIGHT WINDS THROUGH THE PERIOD.
CHANCES FOR FG/BR DEVELOPMENT APPEAR YET AGAIN (MAINLY THINKING
TVC AND ESPECIALLY MBL) LATER TONIGHT INTO SATURDAY MORNING,
POTENTIALLY DROPPING CONDITIONS TO MVFR/ IFR.
APX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...NONE.
DISCUSSION...FEF
AVIATION...NSC
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