Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 250726
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
326 AM EDT TUE AUG 25 2015

.SHORT TERM...TODAY AND TONIGHT

COOL WEATHER PATTERN TO HOLD TODAY AS UNSETTLED NORTHWEST CYCLONIC
FLOW AROUND UPPER LOW PRESSURE SOUTH OF JAMES BAY MAINTAINS MOSTLY
CLOUDY SKIES AND A PERSISTENT FLOW OF AUTUMN LIKE AIR THROUGH THE
REGION. EXPECT MAXIMUM TEMPERATURES TO STALL IN THE MID TO UPPER 60S
MOST LOCATIONS TODAY WITH JUST A SMATTERING OF 70 DEGREE READINGS
POSSIBLE DETROIT SOUTH. WHILE A FEW SHOWERS WILL AGAIN BE POSSIBLE
DURING DIURNAL INSTABILITY MAX THIS AFTERNOON...ACTIVITY SHOULD
REMAIN ISOLATED/WIDELY SCATTERED SOUTH OF I-69 AND PERHAPS SCATTERED
WITH 30 PERCENT COVERAGE AT ITS PEAK OVER THE NORTHERN CWA. NOT MUCH
CHANGE INTO TONIGHT AS MOSTLY CLOUDY SKIES ONLY THIN EVER SO
SLIGHTLY AFTER SUNSET. MINIMUM TEMPERATURES WILL FALL INTO THE LOWER
50S AREAWIDE.

&&

.LONG TERM...WEDNESDAY THROUGH MONDAY

UPPER LOW SPINNING NORTHEAST OF LAKE SUPERIOR WILL SLOWLY LIFT
THROUGH WESTERN QUEBEC ON WEDNESDAY...KEEPING LOWER MICHIGAN UNDER
NORTHWESTERLY FLOW BETWEEN THE BACKSIDE OF THE SYSTEM AND AN
AMPLIFIED UPPER RIDGE BUILDING OVER THE CENTRAL CONUS. MOISTURE WILL
ONLY SLOWLY EXIT THE AREA BEHIND THE DEPARTING SYSTEM...KEEPING
PLENTY OF CLOUDS AND A CHANCE FOR SHOWERS AROUND. LOW-LEVEL LAPSE
RATES WILL STEEPEN ONCE AGAIN DURING THE DAY...ADDING A DIURNAL
COMPONENT TO SHALLOW CONVECTION. THE INFLUENCE OF THE RIDGE TO OUR
WEST AND EXIT OF THE COLD POOL ASSOCIATED WITH THE UPPER LOW WILL
BRING WARMER TEMPS IN THE MID-LEVELS. THIS AND LIGHTER FLOW ACROSS
LAKE MICHIGAN WILL MAKE CONDITIONS LESS FAVORABLE FOR LAKE EFFECT.
EXPECTING ONLY ISOLATED SHOWERS AND SPRINKLES FOR SOUTHEAST
MICHIGAN...WITH POSSIBLY A MORE OF A LOW-END SCATTERED COVERAGE INTO
THE THUMB WHERE MOISTURE AND COOLER AIR ALOFT WILL BE SLOWER TO
EXIT. SURFACE HIGH PRESSURE WILL EXPAND IN FROM THE WEST WEDNESDAY
NIGHT AND BECOME CENTERED OVERHEAD INTO THURSDAY. SUBSIDENCE FROM
THE RIDGE AND DRIER AIR ARE EXPECTED TO PROVIDE DRIER
WEATHER...ALTHOUGH NORTH FLOW OFF LAKE HURON WILL KEEP SOME CLOUDS
AND PERHAPS A FEW LIGHT SHOWERS OVER THE THUMB WEDNESDAY NIGHT.
TEMPERATURES WILL REMAIN COOL THROUGH MID-WEEK...GENERALLY IN THE
UPPER 60S TO LOW 70S FOR HIGHS. EXPECTING A CHILLY NIGHT WEDNESDAY
AS AREAS OUTSIDE OF THE THUMB SEE CLEARING...WITH MINS DROPPING INTO
THE UPPER 40S...WARMER ACROSS THE THUMB AND DETROIT AREA...IN THE
50S.

MODELS THEN CONTINUE TO SHOW A WEAK UPPER WAVE MOVING ACROSS THE
GREAT LAKES OR OHIO VALLEY LATE FRIDAY INTO SATURDAY...ALTHOUGH THEY
STILL DIFFER WITH EXACT TIMING AND PLACEMENT. WILL HAVE TO CONTINUE
TO WATCH THIS SCENARIO AS IT COULD BRING SOME SHOWERS AND
THUNDERSTORMS TO THE AREA FOR THE WEEKEND...PARTICULARLY SATURDAY.
MODELS APPEAR TO ACKNOWLEDGE THE CURRENT MCS OVER SONORA MEXICO
(WHICH THEY WERE DOING YESTERDAY AS WELL)...AND RIDE A REMNANT MCV
FROM THIS SYSTEM UP AROUND THE MONSOONAL HIGH BEFORE AMPLIFYING THE
WAVE OVER WYOMING WEDNESDAY AS IT ENCOUNTERS MORE FAVORABLE JET
DYNAMICS. WITH THIS SCENARIO STILL BEING FAIRLY LOW-
CONFIDENCE...PARTICULARLY REGARDING SHORTWAVE AMPLIFICATION...WILL
MAINTAIN LOW-END POPS PROVIDED BY SUPER-BLEND. TEMPERATURES WILL
WARM THROUGH THE WEEKEND AND INTO NEXT WEEK BEHIND THE LOW AND AS
FLOW TURNS MORE SOUTHERLY. MAX TEMPS SHOULD PUSH BACK UP NEAR THE 80
DEGREE MARK BY SUNDAY.

&&

.MARINE...LOW PRESSURE WILL BE SLOW TO EXIT THE AREA OVER THE NEXT
FEW DAYS...ONLY PROGRESSING FROM NORTHEAST OF LAKE SUPERIOR TO
EASTERN QUEBEC ON WEDNESDAY. THIS WILL KEEP WINDS ELEVATED TODAY
FROM THE WEST...BUT SPEEDS ARE EXPECTED TO BE LOWER THAN YESTERDAY
AND GENERALLY IN THE 15 TO 25 KNOT RANGE. SURFACE HIGH PRESSURE WILL
GRADUALLY BUILD IN FROM THE WEST WEDNESDAY INTO THURSDAY...ALLOWING
WINDS TO BECOME LIGHT FOR WEDNESDAY NIGHT AND THURSDAY.

A COLD DOME OF AIR WILL REMAIN OVER THE CENTRAL GREAT LAKES UNTIL
THE UPPER LOW DEPARTS TO OUR NORTHEAST ON THURSDAY. THE COLD AIR
SITTING OVER THE WARMER LAKE WATERS WILL CREATE UNSTABLE CONDITIONS
AND BRING THE POTENTIAL FOR WATERSPOUTS THROUGH EARLY THURSDAY
MORNING.

&&

.AVIATION...ISSUED 1146 PM EDT MON AUG 24 2015

BROAD AREA OF LOW PRESSURE WILL INFLUENCE THE ENTIRE TAF FORECAST
TIME PERIOD. LOWER STRATOCU BELLOW 5000 FT WAS STRUGGLING TO TAKE
HOLD ACROSS SOUTHEAST MI...BUT ENOUGH LOCATIONS AROUND TO SUGGEST
THAT THE LOWER VFR CEILINGS WILL MATERIALIZE...JUST WILL TAKE A
LITTLE LONGER TO GET THERE. EXPECT RENEWED DIURNAL SURGE TO THE
CLOUDS DURING TUESDAY WHICH WILL ONLY RE-ENFORCE THE GENERALLY VFR
CEILINGS BELOW 5000 FEET INTO TUESDAY EVENING.

FOR DTW...CEILINGS REMAIN ABOVE 5000 FEET THROUGH THE EARLY PART OF
THE NIGHT...BUT THOSE ARE STILL EXPECT TO DROP BELOW 5000 FT EARLY
IN THE TAF FORECAST AND THEN HOLD THROUGH TUESDAY.

//DTW THRESHOLD PROBABILITIES...

* MEDIUM FOR CEILING 5000 FT OR LESS FROM AFTER 08Z THROUGH TUESDAY
  EVENING.

&&

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

$$

SHORT TERM...DG
LONG TERM....HLO
MARINE.......HLO
AVIATION.....99


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