109
FXUS63 KAPX 061909
AFDAPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
309 PM EDT THU AUG 6 2026
KEY MESSAGES
- WEAKLY FORCED CONVECTION OVERNIGHT/FRIDAY?
- PRECIPITATION CHANCES ALONG PASSING COLD FRONT FRIDAY NIGHT/
SATURDAY MORNING...AND MORE SHOWERS SUNDAY.
- RAIN CONTINUES MONDAY (HEAVY RAIN POSSIBILITY LOWER MICHIGAN).
DISCUSSION
ISSUED AT 308 PM EDT THU AUG 6 2026
PATTERN SYNOPSIS/FORECAST: HIGH LATITUDE REX BLOCK ACROSS MUCH OF
CANADA IMPACTING THE PATTERN ACROSS THE NORTHERN TIER OF STATES: LOW
PRESSURE PORTION OF THE BLOCK CENTERED OVER HUDSON BAY EXTENDS SOUTH
INTO THE NORTHERN PLAINS/UPPER MIDWEST/GREAT LAKES. UPPER LEVEL
HIGHS CENTERED OVER THE SOUTHWEST U.S. AND OFF THE MID ATLANTIC
COAST...WITH THE REMNANTS OF AN OLD LOW STILL MEANDERING NEAR THE
FLORIDA PANHANDLE. SEVERAL SHORT WAVE TROUGHS ROTATING THROUGH THE
NORTHER TIER CYCLONIC FLOW; ONE CROSSING THE UPPER LAKES THIS
AFTERNOON...A SECOND DIGGING SOUTHEAST ACROSS THE DAKOTAS...AND A
COUPLE OF EMBEDDED CIRCULATIONS OVER NORTHERN SASKATCHEWAN AND
NORTHWEST ONTARIO. NORTHWEST-SOUTHEAST ORIENTED MOISTURE GRADIENT
ACROSS THE UPPER LAKES: PRECIPITABLE WATER VALUES AT OR BELOW 0.75
INCH ACROSS UPPER MICHIGAN...AND NEAR 1.50 INCHES ACROSS SOUTHEAST
LOWER. AT THE SURFACE...LINGERING BOUNDARY IS DRAPED ACROSS
SOUTHERN LOWER MICHIGAN...EXTENDING SOUTHWEST ACROSS ILLINOIS/
NORTHERN MISSOURI TO A 1014MB FRONTAL WAVE OVER EASTERN KANSAS.
BROAD SUBTROPICAL HIGH OVER THE WESTERN ATLANTIC KEEPING THE
HUMIDITY UP INTO SOUTHERN LOWER MICHIGAN BUT AS MENTIONED EARLIER
LOW LEVELS DRY OUT A BIT TO THE WEST AND NORTH.
GREAT LAKES WILL REMAIN ON THE SOUTHERN PERIPHERY OF THE UPPER LOW
IN THE VICINITY OF HUDSON BAY THROUGH THE WEEKEND...WITH HEIGHT
FALLS/SHORT WAVE TROUGH AND COLD FRONTAL PASSAGE EXPECTED FRIDAY
NIGHT/SATURDAY. A LITTLE MORE INFLUENCE FROM ZONAL PACIFIC-ORIGIN
FLOW SUNDAY...THOUGH THERE WILL STILL BE SHORT WAVES ZIPPING BY
ALONG THE JET AXIS. GIVEN THIS ZONAL FLOW SET UP THERE SHOULD BE A
PERSISTENT EAST-WEST FRONTAL BOUNDARY THAT SETS UP LIKELY SOUTH OF
THE GREAT LAKES FOR MOST OF THE EXTENDED FORECAST PERIOD. FORECAST
TRENDS SUGGEST THE UPPER LOW MAY MAKE A MORE CONCERTED PUSH
SOUTHWARD AROUND THIS TIME NEXT WEEK.
PRIMARY FORECAST CONCERNS:
WEAKLY FORCED CONVECTION OVERNIGHT/FRIDAY?: BEYOND ANYTHING THAT
POPS ALONG THE LAKE HURON BREEZE THIS AFTERNOON...SOME SUBTLE THINGS
TO WATCH TONIGHT ACROSS THE SOUTHEAST THIRD OF THE FORECAST AREA OR
SO. LOW LEVEL THETA-E ADVECTION/CONVERGENCE AND ELEVATED CAPE
(>500J/KG MUCAPE) MAY BE JUST ENOUGH FOR SOME SCATTERED CONVECTION
TO POP. PROBABILITIES MAY BE BOOSTED BY WEAK MID LEVEL SHORT WAVE
TROUGH/PV ANOMALY OVERNIGHT INTO FRIDAY MORNING. LOW PROBABILITY
EVENT BUT PROBABLY NOT LOW ENOUGH TO LEAVE OUT OF THE FORECAST.
DIURNAL HEATING DURING THE DAY FRIDAY AND INCREASING LOW LEVEL
MOISTURE WILL RESULT IN MLCAPE VALUES AT OR ABOVE 1500J/KG
DEVELOPING. FORCING IS PRETTY MINIMAL OUTSIDE OF LOCALIZED
CONVERGENCE AND LAKE HURON LAKE BREEZE. ANY STORMS THAT DO DEVELOP
WILL HAVE A PULSEY-DOWNBURST WIND THREAT WITH THEM.
PRECIPITATION CHANCES ALONG PASSING COLD FRONT FRIDAY NIGHT/
SATURDAY MORNING...AND MORE SHOWERS SUNDAY: A BETTER ORGANIZED/MORE
STRONGLY FORCED BAND OF SHOWERS/THUNDERSTORMS EXPECTED TO CROSS
NORTHERN MICHIGAN LATER FRIDAY NIGHT/SATURDAY MORNING BEFORE THE
FORECAST TRENDS DRIER FOR SATURDAY AFTERNOON. RESPITE FROM
PRECIPITATION CHANCES LOOK TO BE SHORT...COMBINATION OF AN
APPROACHING JET STREAK AND INCREASING LOW LEVEL THETA-E ADVECTION
WILL BRING A RENEWED THREAT FOR SHOWERS/THUNDERSTORMS LATE SATURDAY
NIGHT THROUGH SUNDAY.
RAIN CONTINUES MONDAY (HEAVY RAIN POSSIBILITY LOWER MICHIGAN):
FRONTAL BOUNDARY TO THE SOUTH OF THE GREAT LAKES WITH A LOW
LEVEL DEFORMATION AXIS ACROSS THE UPPER LAKES AND A FEW RIPPLES
IN THE UPPER LEVEL FLOW WILL INCREASE THE CHANCES FOR MORE
WIDESPREAD RAIN MONDAY. LOTS OF MESOSCALE DETAILS TO WORK
OUT...BUT QPF PROBABILITIES ACROSS NORTHERN LOWER SHOWING SOME
POTENTIAL (20-40%) OF EXCEEDING 1 INCH WITH SOME LOW
PROBABILITIES EXCEEDING 2 INCHES MONDAY THROUGH TUESDAY MORNING.
AVIATION /18Z TAFS THROUGH 18Z FRIDAY/
ISSUED AT 133 PM EDT THU AUG 6 2026
LINGERING LOW LEVEL CU WILL DISSIPATE THIS AFTERNOON FOLLOWED BY
MOSTLY SKC TONIGHT COMBINED WITH LIGHT AND VRB WINDS. BR WILL
DEVELOP AT KMBL, DROPPING VSBYS TO MVFR AND PERIODICALLY IFR
BETWEEN 0600Z AND 1300Z TONIGHT/FRIDAY MORNING. LIGHT WINDS VEER
TO THE WEST THIS FRIDAY WITH SCT LOW LEVEL CU RE-DEVELOPMENT
DURING THE DAY.
APX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
MARINE...NONE.
DISCUSSION...JPB
AVIATION...SJC
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