255
FXUS63 KDTX 131120
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
720 AM EDT THU AUG 13 2020
AVIATION
HIGH PRESSURE CENTERED OVER NORTHERN ONTARIO AND QUEBEC HOLDS
CONTROL OF CONDITIONS ACROSS SE MI TODAY AND TONIGHT. LIGHT EASTERLY
LOW LEVEL WIND SUPPLIES DRY AIR INTO THE REGION RESULTING IN JUST
SOME SCATTERED TO BROKEN CIRRUS AT TIMES. NO BIG CHANGES TONIGHT
INTO FRIDAY AS VFR IN THE FORM OF HIGH CLOUDS CONTINUES ALONG WITH
PERHAPS A STEADIER NE WIND COMPARED TO RECENT NIGHTS.
DTW THRESHOLD PROBABILITIES
* NONE
PREV DISCUSSION
ISSUED AT 349 AM EDT THU AUG 13 2020
DISCUSSION...
LITTLE CHANGE IN THE FORECAST AS MODELS ARE IN LOCK STEP ON THE
LARGE SCALE PATTERN HEADING INTO THE WEEKEND. THE ONCE ZONAL FLOW
ACROSS THE NORTHERN TIER OF THE US IS AMPLIFYING AS A SERIES OF WAVES
ENTER THE NW CONUS DEEPEN THE TROUGH OVER WESTERN CANADA. THE
STEEPENING RIDGE AXIS WILL NOT MAKE IT TO MI UNTIL FRIDAY KEEPING US
UNDER CONFLUENT FLOW AND SUBSIDENCE UNTIL THEN. MEANWHILE AT THE
SURFACE, HIGH PRESSURE WILL HOLD OVER THE REGION WHILE SHIFTING ITS
CENTER FROM THE CENTRAL GREAT LAKES WEDNESDAY UP TO HUDSON BAY THIS
AFTERNOON. THIS WILL KEEP A LIGHT EASTERN FLOW INTO THE AREA HELPING
TO KEEP THE CURRENT DRY AIRMASS IN PLACE. PWATS WILL STILL BE AROUND
0.75 INCHES AS SURFACE DEWPOINTS LINGER IN THE MID 50S TO NEAR 60
THIS AFTERNOON. THIS WILL KEEP HEAT INDICES DOWN ONCE AGAIN AS TEMPS
RISE INTO THE MID-UPPER 80S. RETURN OF SOUTHERLY FLOW ON FRIDAY WILL
START TO ALLOW A LITTLE BETTER MOISTURE INTO THE REGION BUT A CUTOFF
LOW MEANDERING AROUND THE MID MS VALLEY INTO TN/KY WILL BLOCK THE
DEEPER GULF MOISTURE SO EXPECTING DEWPOINTS INTO THE LOW TO MID 60S
THROUGH THE WEEKEND.
THERE IS ONE FEATURE IN THE NEAR TERM TO KEEP AN EYE ON FOR THE
FORECAST TODAY AND TONIGHT. A SHORTWAVE AND ASSOCIATED CLUSTER OF
CONVECTION IS CURRENTLY WORKING ACROSS NORTHERN WI AND WILL CONTINUE
ACROSS THE STRAITS TODAY. THOUGH THE UNFAVORABLE ATMOSPHERE WILL
LIKELY MINIMIZE RAIN CHANCES, CLOUDS WILL LIKELY PERSIST. THE MID
LEVEL FEATURE IS ADVERTISED TO GET CUT OFF FROM THE FLOW AND STALL
OVER NORTHERN LOWER TODAY. THIS COULD BRING SOME THICKER CLOUDS INTO
THE SAGINAW VALLEY. FOR NOW, I INCREASED CLOUDS OVER NORTHERN LAKE
HURON BUT HELD OFF OVER LAND AS WE SEE HOW MUCH IT CAN HOLD TOGETHER
IN THE INCREASINGLY LESS FAVORABLE ENVIRONMENT.
ATTENTION THEN TURNS TOWARD THE WEEKEND AND THE RETURN OF RAIN
CHANCES. NOT MUCH HAS CHANGED IN THE MODELS WHICH ISN'T NECESSARILY
A GOOD THING BECAUSE THEY STILL DIFFER ON HOW THEY MANAGE THE TWO
MAIN FEATURES, THE AFOREMENTIONED WEST COAST TROUGH THAT WILL
EVENTUALLY PUSH ACROSS THE GREAT LAKES SUNDAY AND THE CUTOFF LOW TO
OUR SOUTH. IF THE LOW DRIFTS FAR ENOUGH NORTH IT CAN THEN FEEL THE
HEIGHT FALLS OF THE TROUGH AND SHIFT FARTHER NORTH. THIS WOULD MAKE
FOR A RAINY SATURDAY WITH THE WEAK WAVE OVERHEAD ALL DAY. OTHERWISE
THE FEATURES WILL REMAIN DISCONNECTED AND THE SURFACE HIGH WILL HOLD
THROUGH SATURDAY KEEPING US DRY. THE TROUGH AND COLD FRONT WILL
THEN SWEEP ACROSS LOWER MI LATE SUNDAY INTO SUNDAY NIGHT OFFERING
THE CHANCE OF SHOWERS AND THUNDERSTORMS.
IN THE WAKE OF THE FRONT, MUCH COOLER AIR WILL OVERTAKE THE REGION
WITH 850MB TEMPS DROPPING FROM THE PERSISTENT MID TEENS THIS WEEK,
DOWN INTO THE UPPER SINGLE DIGITS BY TUESDAY. FORECAST HIGHS ARE IN
THE 70S WITH LOWS DROPPING INTO THE LOWER 50S.
MARINE...
DRY CONDITIONS PERSIST ACROSS THE CENTRAL GREAT LAKES AS HIGH
PRESSURE CONTINUES TO BUILD OVERHEAD. LIGHT AND VARIABLE WINDS WILL
GRADUALLY BACK TO THE NORTHEAST, WITH WINDS INCREASING TO 10 TO 15
KNOTS BY MIDDAY THURSDAY. GUSTS COULD REACH AROUND 20 KNOTS THURSDAY
AFTERNOON/EVENING, PARTICULARLY ACROSS SAGINAW BAY DUE TO ITS
NORTHEASTERLY FETCH. OVERALL BOATING CONDITIONS ARE EXPECTED TO
REMAIN FAVORABLE THROUGH THE END OF THE WEEK BEFORE ANOTHER
POTENTIAL SYSTEM APPROACHES THE CENTRAL GREAT LAKES THIS WEEKEND.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
AVIATION.....BT
DISCUSSION...DRK
MARINE.......SS
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