554
FXUS63 KDTX 192321
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
721 PM EDT FRI AUG 19 2022
AVIATION
LINGERING POCKETS OF HIGH BASED DIURNAL CU WILL FADE WITH THE LOSS
OF DAYTIME HEATING, LEAVING PLENTY OF CLEAR SKY FOR THE OVERNIGHT
PERIOD. PROSPECTS FOR A MINOR VISIBILITY RESTRICTION IN SHALLOW FOG
NEAR DAYBREAK LIMITED BY CONTINUED WEAK SOUTHERLY FLOW, PRECLUDING A
DEFINED MENTION ATTM. A GRADUAL INCREASE IN MOISTURE MAY INTRODUCE A
FEW WIDELY SCATTERED SHOWERS BY EARLY SATURDAY. GREATER POTENTIAL
FOR SHOWERS AND THUNDERSTORMS WILL EXIST DURING THE AFTERNOON AND
EVENING HOURS AS A LOW PRESSURE SYSTEM GRADUALLY APPROACHES THE
REGION.
DTW THRESHOLD PROBABILITIES...
* LOW FOR CEILINGS AT OR BELOW 5000 FT SATURDAY AFTERNOON.
* LOW FOR THUNDERSTORM SATURDAY AFTERNOON AND EVENING.
PREV DISCUSSION
ISSUED AT 355 PM EDT FRI AUG 19 2022
DISCUSSION...
UPPER LOW CURRENTLY CIRCULATING OVER SOUTHERN MINNESOTA/SOUTH
DAKOTA, EVIDENT PER WV IMAGERY, LARGELY GOVERNS THE FORECAST OVER
THE NEXT SEVERAL DAYS, SUPPORTIVE OF WIDESPREAD SHOWER AND
THUNDERSTORM ACTIVITY THROUGHOUT THE WEEKEND. FOR THE REST OF THIS
EVENING, SOUTHEAST MI RESIDES WELL AHEAD OF THE LOW, KEEPING SKIES
GENERALLY CLEAR ASIDE FROM DIURNAL CU. TEMPERATURES HOVERING IN THE
MID 80S AND DEWPOINTS IN THE LOW 60S CONTRIBUTE TO AN OVERALL
COMFORTABLE AND DRY EVENING, WITH LOWS DIPPING INTO THE LOW TO MID
60S OVERNIGHT.
MAIN FOCUS FOR THIS UPDATE IS ON SHOWER AND THUNDERSTORM ACTIVITY
TOMORROW. INITIAL RIBBON OF VORTICITY EMANATING OFF THE PARENT LOW
PUSHES INTO SE MI EARLY TOMORROW MORNING, INCREASING HIGH CLOUD
COVERAGE AND KICKSTARTING A PERIOD OF MOISTURE ADVECTION INTO THE
CWA. GENERALLY DRY START TO THE DAY GIVEN LACKLUSTER LOW LEVEL
MOISTURE, ALTHOUGH COULD SEE A FEW ELEVATED SHOWERS WHERE LAKE
MOISTURE AUGMENTS THE PROFILE. THUNDERSTORM CHANCES THEN INCREASE
AFTER NOON AS DIURNAL HEATING AND ASSOCIATED INSTABILITY RAMP UP,
ALTHOUGH THE DEGREE TO WHICH THE ATMOSPHERE DESTABILIZES WILL BE
HIGHLY DEPENDENT ON BOTH CLOUD COVER AND EXTENT OF LOW LEVEL
MOISTURE ADVECTION (12Z GUIDANCE SUGGESTS MLCAPE BUILDING TO 500-
1000 J/KG BY 18Z). ALTHOUGH SOME CELLS MAY DEVELOP EARLY AFTERNOON
IN THE WAKE OF BOUNDARY LAYER HEATING, A MORE FOCUSED REGION OF
MULTICELLULAR CONVECTION DEVELOPS UPSTREAM (ACROSS NORTHERN IL/IN)
ALONG RESIDUAL OUTFLOW AND PUSHES NORTHEAST INTO THE CWA MID
AFTERNOON TO EARLY EVENING (BETWEEN ABOUT 2 TO 8 PM LOCAL TIME).
ORGANIZED CONVECTION WILL BE LIMITED GIVEN WEAK DEEP LAYER SHEAR
(~20 KNOTS IN THE 0-6 KM LAYER), ALTHOUGH A FEW STRONG TO ISOLATED
SEVERE DOWNBURST WINDS ARE PLAUSIBLE GIVEN FAVORABLE MOISTURE
PROFILES AND STEEP LOW LEVEL LAPSE RATES. THUS, SPC DAY 2 MARGINAL
RISK LOOKS REASONABLE, KEEPING THE HIGHLIGHTED AREA SOUTH OF I-69
WITH INCREASING FAVORABILITY FOR STRONG TO ISOLATED SEVERE STORMS
TOWARD THE OHIO BORDER.
THUNDERSTORM INTENSITY WANES AFTER SUNSET TOMORROW, ALTHOUGH
ELEVATED THUNDERSTORMS DO REMAIN POSSIBLE OVERNIGHT INTO SUNDAY
MORNING AS MUCAPE HOVERS AROUND 500-1000 J/KG. VORT MAX AND
ASSOCIATED SYNOPTIC ASCENT TRANSITION OVERHEAD DAYTIME SUNDAY,
TAPPING INTO A DEEPLY SATURATED PROFILE WITH PWATS IN EXCESS OF 1.5"
(NEAR 90TH PERCENTILE FOR MID AUGUST). DEEP LAYER SHEAR REMAINS
MEAGER IN THE OVERALL WEAK AMBIENT FLOW PATTERN, ONCE AGAIN
INHIBITING ORGANIZED CONVECTION. STILL LOW CONFIDENCE IN COVERAGE OF
SHOWERS AND STORMS ON SUNDAY, ALTHOUGH ABUNDANCE OF MOISTURE AND AT
LEAST SOME RESIDUAL INSTABILITY LIKELY KEEP ON AND OFF SHOWERS GOING
THROUGH MUCH OF THE DAY IN THE WAKE OF BACKGROUND SYNOPTIC FORCING.
STUBBORN UPPER LEVEL PATTERN THEN EJECTS EASTWARD LATE SUNDAY INTO
MONDAY, SHIFTING FLOW TO THE NORTHWEST AND USHERING IN COOLER AND
DRIER CONDITIONS. SOME LINGERING SHOWER ACTIVITY WILL BE POSSIBLE
MONDAY MORNING AS RESIDUAL MOISTURE CLEARS OUT, FOLLOWED BY A
CLEARING TREND FOR THE AFTERNOON. OVERALL SEASONABLE CONDITIONS
EXPECTED THROUGH MID-WEEK WITH TEMPERATURES IN THE LOW 80S ON MONDAY
REBOUNDING SLIGHTLY INTO THE MID 80S BY MID WEEK AS HIGH PRESSURE
BUILDS IN.
MARINE...
A RIDGE OF HIGH PRESSURE WILL CONTINUE TO BRING DRY WEATHER AND
LIGHT WINDS OVER THE WATERS THROUGH THE FIRST HALF OF SATURDAY. A
SLOW MOVING LOW PRESSURE SYSTEM WILL THEN BRING ACTIVE WEATHER LATER
IN THE DAY ON SATURDAY AND AGAIN ON SUNDAY, AS WIDELY SCATTERED TO
NUMEROUS SHOWERS AND SOME THUNDERSTORMS ARE EXPECTED TO DEVELOP.
THERE WILL BE AN ISOLATED RISK FOR SEVERE WEATHER, WITH THE MAIN
THREAT COMING AS HIGHLY LOCALIZED DOWNDRAFTS TO 34 KNOTS. THIS
SEVERE THREAT IS EXPECTED TO REMAIN CONFINED ACROSS THE SAGINAW BAY
INTO SOUTHERN LAKE HURON, AND LOCATIONS SOUTH. OUTSIDE OF ANY
THUNDERSTORM ACTIVITY, WINDS WILL REMAIN LIGHT GIVEN THE WEAK
PRESSURE GRADIENT AND STABLE LAKE CONDITIONS. SOME RESIDUAL RAIN
SHOWERS WILL AGAIN BE POSSIBLE ON MONDAY, WITH HIGH PRESSURE THEN
BUILDING IN THROUGH THE MIDWEEK PERIOD, BRINGING CONTINUED LIGHT
WINDS AND THE RETURN OF DRY WEATHER.
HYDROLOGY...
WIDESPREAD SHOWERS AND THUNDERSTORMS DEVELOP TOMORROW AFTERNOON AS A
MID LEVEL CLOSED LOW AND ATTENDANT FRONTAL FEATURES MOVES INTO
SOUTHEAST MI. PWATS INCREASE TO 1.50 INCHES OR GREATER BY SATURDAY
EVENING, PROVIDING AMPLE MOISTURE FOR HEAVY RAINFALL. OVERALL
PRECIPITATION RESULTS IN BASIN TOTALS AVERAGING BETWEEN A HALF TO
THREE QUARTERS OF AN INCH, ALTHOUGH EMBEDDED THUNDERSTORMS WILL BE
CAPABLE OF PRODUCING LOCALIZED TOTALS IN EXCESS OF 1 INCH. WHILE
WIDESPREAD FLOODING IS NOT A CONCERN, MINOR FLOODING MAY OCCUR IN
LOW LYING AND FLOOD PRONE AREAS WITH ANY HEAVIER DOWNPOURS OR IF
CELLS REPEATEDLY IMPACT ANY SINGLE LOCATION.
DTX WATCHES/WARNINGS/ADVISORIES
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
AVIATION.....MR
DISCUSSION...MV
MARINE.......AM
HYDROLOGY....MV
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page