Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 260357
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1157 PM EDT THU SEP 25 2014

.AVIATION...

//DISCUSSION...

THE INGREDIENTS FOR FOG HAVE PROGRESSED FARTHER ALONG TONIGHT
COMPARED TO THE LAST COUPLE. OBSERVATIONAL TRENDS SUPPORT A MORE
LENGTHY PERIOD OF MVFR WITH IFR LIKELY PREVAILING BY SUNRISE DUE TO
IMPROVED SURFACE DEWPOINT QUALITY IN THE MBS...FNT...AND PTK
AREAS...AND THE POTENTIAL FOR IT TO INCREASE IN THE DTW CORRIDOR
NEAR LAKE ERIE/ST CLAIR. MODEL SOUNDINGS HAVE PICKED UP ON THE
INCREASED SURFACE MOISTURE BUT STILL SHOW THE DEPTH TO BE SHALLOW
ENOUGH TO MIX OUT QUICKLY AFTER SUNRISE. SURFACE HIGH PRESSURE
EXTENDING FROM THE NEW ENGLAND COAST TO WISCONSIN WILL THEN SUPPORT
IDEAL AVIATION CONDITIONS DURING THE REST OF THE DAY THROUGH FRIDAY
NIGHT.

//DTW THRESHOLD THREATS...

* NONE.

&&

.PREV DISCUSSION...ISSUED 303 PM EDT THU SEP 25 2014

SHORT TERM...TODAY AND TONIGHT

WATER VAPOR IMAGERY SHOWS LOCAL AREA BETWEEN TWO UPPER WAVES
EMBEDDED IN THE LARGER-SCALE EXPANSIVE LONGWAVE RIDGE STRUCTURE.
WAVE OVER W PA WILL CONTINUE NEWD WITHOUT IMPACT LOCALLY. WAVE OVER
IA WILL CONTINUE TO DRIFT SWWD...ITS CIRCULATION ADVECTING MODEST
UPPER MOISTURE OVER OUR AREA...RESPONSIBLE FOR THE INCREASE IN
CIRRUS RELATIVE TO YESTERDAY. THE REST OF THE COLUMN REMAINS BONE
DRY AS DEPICTED BY LAST SEVERAL DTX RAOBS AND LACK OF ANY CUMULUS
DEVELOPMENT THIS AFTERNOON. ANY CIRRUS SHOULD REMAIN SCATTERED
OVERNIGHT AS MODEL RH FIELDS SHOW UPPER MOISTURE SHRIVELING. RESULT
WILL BE LOW TEMPS SIMILAR TO LAST NIGHT IN THE MID-40S TO AROUND 50
OUTSIDE THE DETROIT HEAT ISLAND. SOME DEGREE OF FOG FORMATION
EXPECTED AGAIN AFTER MIDNIGHT IN FAVORED AREAS WITH LOWS EXPECTED TO DROP
BELOW CROSSOVER TEMPS...BUT LACK OF MOISTURE WILL LIMIT EXTENT AND
DEPTH OF FOG.

LONG TERM...FRIDAY THROUGH NEXT THURSDAY

HIGH PRESSURE WILL REMAIN ANCHORED OVER THE AREA THROUGH THE WEEKEND
BEFORE IT IS GRADUALLY PINCHED OFF AS WEAK LOW PRESSURE...REMNANTS
OF A TROPICAL WAVE...LIFTS FROM THE GULF/MEXICO TOWARDS THE OHIO
VALLEY AND ANOTHER SHORTWAVE SHIFTS ACROSS SOUTHERN CANADA AND
DISSIPATES WITHIN CONFLUENT UPPER FLOW OVER THE NORTHERN GREAT LAKES
BY EARLY NEXT WEEK. WITH TIME...THE HIGH WILL SHIFT TO THE EAST AS
IT WEAKENS.

BY THIS TIME...AT THE END OF THIS FORECAST PERIOD...A MAJOR UPPER
LEVEL PATTERN CHANGE WILL BE UNDERWAY AS STRONG UPPER TROUGHING TO
THE WEST EXPANDS OVER MUCH OF THE CONUS WEST OF THE MISSISSIPPI
VALLEY. WHILE THE UPPER RIDGING DOWNSTREAM OF THIS DEVELOPING TROUGH
WILL MAINTAIN MILD WEATHER FOR THE DURATION OF THIS FORECAST...RAIN
CHANCES WILL BEGIN TO PICK UP...AND MAY IMPINGE ON DAY 7...DEPENDING
ON THE EASTWARD PROGRESSION OF THIS LARGE SCALE TROUGH.

MEANWHILE...TEMPERATURES ARE EXPECTED TO CLIMB INTO THE 70S DURING
EVERY DAY OF THIS FORECAST...WELL INTO THE 70S THROUGH THIS WEEKEND
AS MOSTLY SUNNY SKIES FRIDAY/SATURDAY SLOWLY GIVE WAY TO INCREASING
CLOUDS SUNDAY AS WEAK UPPER SHORTWAVE REPLACES THE UPPER RIDGE WHICH
ROLLS INTO AREA OVER THE NEXT 24-36 HOURS AS COMPACT UPPER LOW
RETROGRADES GRADUALLY WESTWARD ACROSS IOWA. WITH CALM CONDITIONS AND
LONGER NIGHTS...PATCHY FOG WILL REMAIN A POSSIBILITY...ESPECIALLY TO
THE LEE OF THE GREAT LAKES WHERE WEAK EAST/SOUTHEAST FLOW SHOULD
LEAD TO A SLIGHT ENHANCEMENT OF LOW LEVEL MOISTURE (AND SATURATION
POTENTIAL DURING THE COMING EARLY MORNINGS).

MARINE...

HIGH PRESSURE WILL MAINTAIN FAVORABLE MARINE CONDITIONS INTO EARLY
NEXT WEEK AS WINDS REMAIN LIGHT AND WAVE DEVELOPMENT NEGLIGIBLE. A
DISSIPATING SHORTWAVE WILL DROP INTO THE NORTHERN GREAT LAKES BY
EARLY NEXT WEEK...BRINGING A SLIGHT CHANCE OF SHOWERS OVER PORTIONS
OF LAKE HURON. OTHERWISE...DRY WEATHER CAN BE EXPECTED.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.

&&

$$

AVIATION.....BT
SHORT TERM...DT
LONG TERM....DG
MARINE.......DG


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









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