889
FXUS63 KAPX 172320
AFDAPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
720 PM EDT THU SEP 17 2026
KEY MESSAGES
- RAIN CHANCES RETURN FOR THE WEEKEND...BUT PROBABILITIES/
EVOLUTION ARE IN QUESTION (SOME AREAS MAY NOT SEE
PRECIPITATION AT ALL).
- SEASONABLY COOL MONDAY THROUGH MIDWEEK.
DISCUSSION
ISSUED AT 245 PM EDT THU SEP 17 2026
PATTERN SYNOPSIS: NORTH AMERICAN PATTERN ANCHORED BY IMPRESSIVE
600DAM 500MB HIGH (+3 SIGMA HEIGHT ANOMALY) ENCOMPASSING MUCH OF THE
SOUTHERN U.S. SPLIT FLOW ACROSS THE WESTERN U.S. BETWEEN STRONG
ZONAL FLOW ACROSS WESTERN CANADA AND A STALLING UPPER LOW OVER
CALIFORNIA; GREAT LAKES UNDER THE INFLUENCE OF THE SOUTHERN BRANCH
OF THIS SPLIT WITH A STRONG JEST STREAK ACROSS NORTHERN ONTARIO/
QUEBEC. LOW AMPLITUDE SHORT WAVE CROSSING THE UPPER LAKES
TODAY...PART OF A LONG (LATENT) PV FILAMENT THAT STRETCHES FROM
QUEBEC ALL THE WAY BACK TO THE CALIFORNIA UPPER LOW. WEST-EAST AXIS
OF DEEPER MOISTURE ROTATING AROUND THE NORTHERN PERIPHERY OF THE
SOUTHERN U.S. ANTICYCLONE...FROM THE MID MISSISSIPPI VALLEY EAST
ACROSS THE OHIO VALLEY AND INTO THE MID ATLANTIC/SOUTHERN NEW
ENGLAND. ALSO ALONG THE NORTHERN PERIPHERY THE UPPER HIGH STRETCHES
A SURFACE FRONT FROM NEW ENGLAND BACK INTO THE CENTRAL PLAINS...
SERVING AS AN UNRELENTING CORRIDOR OF RAINFALL SOUTH AND WEST OF
MICHIGAN FOR THE MOST PART. BROAD HIGH PRESSURE EXTENDS FROM
CENTRAL CANADA ACROSS THE UPPER LAKES AND INTO QUEBEC.
PRIMARY FORECAST CONCERNS:
RAIN CHANCES RETURN FOR THE WEEKEND...BUT PROBABILITIES/EVOLUTION
ARE IN QUESTION (SOME AREAS MAY NOT SEE PRECIPITATION AT ALL):
LOOKS LIKE WE WILL BE ABLE TO SQUEEZE OUT A DRY DAY FRIDAY; HIGH
PRESSURE OVER MANITOBA AND RIDGING INTO THE UPPER MIDWEST/GREAT
LAKES THIS AFTERNOON WILL PROPAGATE INTO NORTHERN ONTARIO
FRIDAY...INCREASING NORTHEAST BOUNDARY LAYER FLOW INTO NORTHERN
MICHIGAN. MID/HIGH CLOUDS WILL THICKEN DURING THE AFTERNOON...
PRECIPITATION SHIELD ACROSS MINNESOTA/WISCONSIN DRIVEN BY
ISENTROPIC ASCENT AND ENTRANCE REGION JET FORCING WILL SPREAD
ACROSS LAKE MICHIGAN BY EARLY FRIDAY EVENING. BUT WITH
CONVECTION LIKELY DEVELOPING ACROSS IOWA FRIDAY AFTERNOON/
EVENING WHERE THE LOW LEVEL JET INTERSECTS THE WARM FRONTAL
BOUNDARY...THIS MAY TEND TO ALLOW THE PRECIP SHIELD TO PROPAGATE
MORE SOUTHEAST WITH TIME. THE IMPLICATION IS THAT PRECIPITATION
MAY BE CONFINED TO ABOUT THE SOUTHWEST HALF OF THE FORECAST
AREA FRIDAY NIGHT/SATURDAY. THIS IS DEFINITELY A TREND TO THE
SOUTH WITH THIS FORECAST...PROBABILITIES OF EXCEEDING 1 INCH/24
HOURS THROUGH 0000Z SUNDAY AROUND 40% ACROSS MANISTEE COUNTY AND
DROPS BELOW 10% NORTH OF M-32. IN FACT CURRENT FORECAST WILL
NOT CARRY POPS NORTH OF A CHARLEVOIX-HARRISVILLE LINE THROUGH
THE WEEKEND. RAIN CHANCES WILL LINGER SOUTH OF M-32 INTO SUNDAY
THOUGH ANTICIPATING A DECREASING TREND FROM NORTH TO SOUTH.
OVERALL HIGHEST RAINFALL AMOUNTS FRIDAY NIGHT THROUGH SUNDAY
AFTERNOON 0.50- 1.00 INCH POSSIBLE ALONG-SOUTH OF M-55.
SEASONABLY COOL MONDAY THROUGH MIDWEEK: HIGH PRESSURE TO THE NORTH
OF THE GREAT LAKES THROUGH MIDWEEK SHOULD RESULT IN A PREPONDERANCE
OF EAST/NORTHEAST BOUNDARY LAYER FLOW INTO MICHIGAN THROUGH
WEDNESDAY. THIS WILL KEEP TEMPERATURES GENERALLY IN THE 60S FROM
MONDAY THROUGH THE MIDDLE OF THE WEEK...WHICH WILL BE A FEW
DEGREES BELOW NORMAL THOUGH WE ARE BEGINNING OUR FORAY INTO
NORMAL DAYTIME HIGHS IN THE 60S. REMNANTS OF THE UPPER LOW OVER
CALIFORNIA COULD BRING SOME RAIN CHANCES BACK TO THE REGION BY
MIDWEEK.
AVIATION /00Z TAFS THROUGH 00Z SATURDAY/
ISSUED AT 720 PM EDT THU SEP 17 2026
MAINLY VFR CONDITIONS ARE EXPECTED ACROSS NORTHERN MICHIGAN TAF
SITES THROUGH THE ISSUANCE PERIOD. PATCHY FG/BR DEVELOPMENT IS
POSSIBLE LATE TONIGHT/EARLY FRIDAY MORNING, ESPECIALLY ACROSS
INTERIOR LOW-LYING AREAS -- ALTHOUGH FG/BR MAY RESULT IN VSBY
RESTRICTIONS FOR A BRIEF TIME. ANY FG/BR WILL QUICKLY BURN OFF AFTER
SUNRISE, BRINGING VFR CONDITIONS BACK TO ALL AREAS. WEAK/CALM WINDS
TONIGHT WILL INCREASE TO AROUND 5-10 KTS OUT OF THE NORTHEAST ON
FRIDAY.
APX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...NONE.
DISCUSSION...JPB
AVIATION...DJC
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