Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 241928
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
328 PM EDT THU JUL 24 2014

.SHORT TERM...THROUGH TONIGHT

QUIET NIGHT AHEAD AS AN AREA OF SURFACE HIGH PRESSURE DRIFT ACROSS
SOUTHERN MI. THE CENTER OF THE HIGH LOOKS TO POSITION ITSELF RIGHT
OVER SOUTHERN LOWER MI FROM ABOUT 00Z-06Z FRIDAY. THE DRY AIR
ADVECTING IN ALONG WITH INCREASING SUBSIDENCE WILL HELP SCOUR OUT
THE THIN LAYER OF MOISTURE/CU THIS EVENING BRINGING CLEAR SKIES
THROUGH THE OVERNIGHT. WINDS WILL ALSO DECREASE AS THE VEER FROM
NORTHERLY TO SOUTHWESTERLY BY MORNING. WE WILL START SEEING SOME
HIGH CLOUD DEBRIS MOVING INTO THE AREA LATE TONIGHT FROM CONVECTION
CURRENTLY OVER MN BUT ANY LOW CLOUD DEVELOPMENT WILL HOLD OFF TIL
VERY CLOSE TO SUNRISE AS SW FLOW BEGINS TO KICK IN ALLOWING MOISTURE
TO START ADVECTING BACK INTO THE LOW LEVELS. THE ADDITIONAL DRY AIR
AND FAVORABLE RADIATIONAL COOLING CONDITIONS WILL ALLOW TEMPERATURES
TO ONCE AGAIN DROP TO AROUND 50F...WITH SOME UPPER 40S IN THE
TYPICAL COOLER LOCATIONS. SURFACE DEWPOINTS MIXED OUT INTO THE UPPER
40S THIS AFTERNOON WHICH ALSO SUPPORT THESE COOL MIN TEMPS...NEAR 10
DEGREES BELOW NORMAL FOR LATE JULY.

&&

.LONG TERM...

SHOWERS AND THUNDERSTORMS HAVE DEVELOPED WITHIN THE DEEP MOISTURE
PLUME PRESENT OVER THE GREAT PLAINS THIS AFTERNOON. THIS ACTIVITY
WAS INITIATED ALONG THE LEAD EDGE OF HEIGHT FALLS EMANATING FROM THE
PAC NW LOW AND A MERIDIONALLY ORIENTED 40KT LLJ. THE UPPER FLOW OVER
THE CENTRAL U.S. AND GREAT LAKES WILL WILL RAPIDLY ACQUIRE A
STRONGLY CONFLUENT CHARACTER AS EASTWARD PROGRESS OF SAID LOW
DAMPENS THE UPSTREAM RIDGE. THE RESULTANT TRANSITION TOWARD DEEP
LAYER WESTERLY FLOW WILL FORCE THE HIGH THETA-E PLUME TO FOLD ACROSS
THE AREA LATE FRIDAY INTO FRIDAY NIGHT. LINGERING SURFACE HIGH
MAINTAINED BY MID-LEVEL CONFLUENCE AND PLENTY OF DRY AIR WILL ENSURE
THAT UPSTREAM ACTIVITY DRIES UP BEFORE IT HAS A CHANCE TO AFFECT THE
CWA TOMORROW AFTERNOON, GUARANTEEING ANOTHER DRY DAY FRIDAY. AIRMASS
MODIFICATION WILL ADD A COUPLE DEGREES TO HIGHS COMPARED TO TODAY,
SUGGESTING MOST PLACES TOPPING OUT IN THE UPPER 70S.

MOISTURE RETURN GETTING UNDERWAY IN EARNEST FRIDAY NIGHT THROUGH
SATURDAY AS THE LOW MIGRATES INTO NORTHERN MN AND COMES UNDER
INCREASING INFLUENCE OF THE LARGE NORTHEAST CANADA VORTEX. HEIGHT
FALLS WILL BE ONGOING THROUGH THE WEEKEND, HELPING TO GRADUALLY
WEAKENING AMBIENT CAPPING WITH TIME. THE FIRST CHANCE FOR SHOWERS
AND TSTORMS WILL BE LATE FRIDAY NIGHT AS THE PREVIOUSLY DISCUSSED
THETA-E AXIS WASHES ACROSS THE STATE AND THE LOW-LEVEL JET RAMPS UP.
NOTHING WORTH MORE THAN A LOW CHC POP ATTM AS FORCING WILL NOT BE
TERRIBLY IMPRESSIVE AND THERE WILL BE A LOT OF DRY AIR TO OVERCOME.

SEVERE POTENTIAL WILL EXIST BOTH SATURDAY AFTERNOON AND ALL DAY
SUNDAY. ON SATURDAY, THE THREAT WILL DEPEND STRONGLY ON PRIOR
CONVECTIVE TRENDS AND POSITIONING OF STATIONARY FRONT, WHICH IS MOST
LIKELY TO SET UP NEAR OR JUST SOUTH OF THE CWA PER 00Z/12Z PROGS.
UPSTREAM CONVECTION, ENERGETIC WESTERLY FLOW, AND THE POTENTIAL FOR
MORNING CONVECTION ALL POINT TO AN ABUNDANCE OF CLOUDS, POTENTIALLY
STRONG CAPPING, AND A GRUNGY/MUGGY DAY IN GENERAL. DESTABILIZATION
POTENTIAL DOES NOT LOOK GREAT, BUT WILL REQUIRE MONITORING GIVEN THE
40-50KTS OF 0-6KM BULK SHEAR THAT WILL BE PRESENT.

BY SUNDAY, MID-LEVELS ARE FORECAST COOL SIGNIFICANTLY. MEANWHILE,
INCREASING INTERACTION BETWEEN THE NORTHEAST CANADA VORTEX AND THE
APPROACHING UPPER LOW WILL HELP TO WHIP A CORRIDOR OF SIGNIFICANT
HEIGHT FALLS ACROSS THE GREAT LAKES DURING MID/LATE DAY. THE
STATIONARY FRONT WILL BE FORCED NORTH WHILE THE STRONGEST WESTERLIES
WILL BE SHUNTED SOUTHWARD ALONG THE SOUTHERN PERIPHERY OF THE LOW
CENTER - ALTHOUGH BULK SHEAR VALUES ARE STILL PROGGED TO REMAIN
ADEQUATE - AT OR ABOVE 30KTS FOR MOST OF THE CWA. COOL MID-LEVELS
AND INFLUX OF WARMER SURFACE AIR/DEWPOINTS POINT TO POTENTIALLY HIGH
CAPE DENSITY AND THE POSSIBILITY FOR A POTENT SEVERE WX SCENARIO.

LOW PRESSURE WILL CONTINUE TO BE SITUATED OVER THE CENTRAL GREAT
LAKES ON SUNDAY NIGHT RESULTING IN RAINS SHOWERS AND POTENTIALLY
THUNDERSTORMS ACROSS THE CWA. STRONG HIGH PRESSURE WILL BUILD
QUICKLY INTO THE WESTERN GREAT LAKES BY MONDAY MORNING AND REMAIN
OVER THE GREAT LAKES THROUGH MOST OF THE WEEK. THIS HIGH WILL BRING
MOSTLY DRY CONDITIONS TO SOUTHEAST MICHIGAN...HOWEVER...CURRENT
MODEL RUNS SUPPORT SOME SCATTERED SHOWERS IN THE AFTERNOON HOURS AS
DIURNAL INSTABILITY DEVELOPS THROUGHOUT THE DAYTIME HOURS NEXT WEEK.
HIGH TEMPERATURES WILL REMAIN FAIRLY MILD /MID-70S/ THROUGH NEXT
THURSDAY WITH OVERNIGHT LOW TEMPERATURES IN THE MID TO UPPER 50S.

&&

.MARINE...

EPISODES OF THUNDERSTORMS WILL AFFECT THE WATERS SATURDAY THROUGH
SUNDAY AS A WARM AND MOIST AIRMASS LIFTS INTO THE GREAT LAKES
REGION. SEVERE WEATHER WILL BE A POSSIBILITY BOTH SATURDAY AFTERNOON
AND AGAIN DURING THE DAY ON SUNDAY. WINDS...ON THE OTHER HAND...WILL
REMAIN ON THE LIGHT SIDE THROUGH THE WEEKEND BEFORE RAMPING UP AGAIN
EARLY NEXT WEEK AS ANOTHER ROUND OF COOL AIR SPREADS ACROSS AREA
WATERS. MODERATE TO FRESH NORTH WINDS WITH GUSTS TO 25 KNOTS OR
SLIGHTLY HIGHER WILL BE COMMON BY MONDAY.

&&

.AVIATION...ISSUED 120 PM EDT THU JUL 24 2014

//DISCUSSION...

HIGH PRESSURE WILL SLIDE ACROSS THE REGION OVERNIGHT WHICH WILL
RESULT IN VFR CONDITIONS THROUGH THE FORECAST PERIOD. THE DIURNAL CU
FIELD HAS PEAKED IN COVERAGE AND WILL BEGIN TO SCATTER OUT THROUGH
THE REST OF THE AFTERNOON BEFORE CLEARING OUT THIS EVENING. LIGHT
WINDS OUT OF THE NORTH/NORTHEAST WILL RELAX THIS EVENING AS THE HIGH
GET CLOSER. HAVE GONE WITH VARIABLE WINDS FOR THE OVERNIGHT AS THE
LIGHT WINDS WILL VEER FROM NORTHEAST THROUGH EAST TONIGHT...BECOMING
SOUTHWEST BY FRIDAY MORNING. ANOTHER DIURNAL CU FIELD WILL DEVELOP
FRIDAY MORNING WHILE HIGH CLOUDS BEGIN STREAMING IN FROM THE
WEST/SOUTHWEST.

//DTW THRESHOLD THREATS...

* NONE.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.

&&

$$

SHORT TERM...DRK
LONG TERM....JVC/RK
MARINE.......JVC
AVIATION.....DRK


YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).





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