Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 271943
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
343 PM EDT THU AUG 27 2015

.SHORT TERM...TODAY AND TONIGHT

A PERSISTENT UPPER LEVEL TROUGH WITH A RESPECTABLE EQUATORWARD REACH
REMAINS IN PLACE OVER THE CENTRAL GREAT LAKES. UPPER LEVEL CHARTS
AND SATELLITE IMAGERY SUPPORTS LOWERED GEOPOTENTIAL HEIGHTS CLEAR
DOWN INTO THE GULF OF MEXICO. IT IS WITHIN THE LOWERED HEIGHTS THAT
ORPHANED LOWER TROPOSPHERIC MOISTURE REMAINS MIRED OVER SOUTHEASTERN
MICHIGAN THIS AFTERNOON. WITH AN OPTICALLY THICK DECK OF STRATUS AND
STRATOCUMULUS...THE THINKING IS IT WILL TAKE A COMBINATION OF A
CHANGE IN 925-850 MB FLOW TRAJECTORIES TO THE SOUTHWEST AND A LOSS
OF DAYTIME HEATING TO FACILITATE A DEFINITIVE CLEARING TREND THIS
EVENING. THE OUTGOING FORECAST WILL CALL FOR SKC DEVELOPING DURING
THE MID TO LATE EVENING HOURS.

THE CENTER OF THE STABLE SURFACE ANTICYCLONE WILL MIGRATE ACROSS
SOUTHEASTERN MICHIGAN BY THIS EVENING...CENTERING OVER MUCH OF PA BY
FRIDAY 12Z. LOSS OF SKY FRACTION AND LONGWAVE RADIATIONAL COOLING
SHOULD ALLOW TEMPERATURES TO DROP INTO THE LOWER 50S BY MORNING.
CURRENT SFC DEWPOINTS AND MODELED THERMODYNAMICS SUPPORT AT LEAST A
LOW END POTENTIAL FOR SOME SHALLOW GROUND BR RIGHT AT DAYBREAK.

&&

.LONG TERM...FRIDAY THROUGH NEXT THURSDAY

UPPER WAVES OVER WY/NE/SD ARE FORECAST TO CONSOLIDATE INTO A SHARPER
SHORTWAVE TROUGH AS THEY MOVE THROUGH THE PLAINS FRIDAY. MODELS THEN
DIVERGE WITH WHETHER THIS SHORTWAVE AMPLIFIES AS NORTHERN STREAM
ENERGY DROPS INTO IT FROM CANADA...OR WHETHER IT SHEARS OUT OVER THE
CENTRAL GREAT LAKES ON SATURDAY WITH THE NORTHERN STREAM ENERGY THEN
LAGGING BEHIND THE FIRST WAVE SATURDAY NIGHT. AS A RESULT OF MODELS
STRUGGLING WITH THE DEVELOPMENT AND INTERACTION OF THESE TWO
WAVES...THERE ARE MAJOR DIFFERENCES WITH THE TIMING/TRACK OF SURFACE
LOW PRESSURE ACROSS THE AREA AND TIMING/PLACEMENT OF FRONTAL
FEATURES AND POSSIBLE DEFORMATION AREA THAT COULD DEVELOP.

FORECAST FOR FRIDAY NIGHT IS FOR SHOWERS/TSTORMS TO SPREAD INTO
MICHIGAN ALONG A WARM FRONT...WITH BEST POTENTIAL ALONG/NORTH OF M-
59. LARGE DIFFERENCES WITH MODEL EVOLUTION OF THE UPPER WAVE AND
TRACKS FOR SURFACE LOW PRESSURE THEN MAKE DETAILS VERY HARD BY
SATURDAY OTHER THAN TO SAY THERE IS A GOOD CHANCE FOR
SHOWERS/TSTORMS. GIVEN DEGREE OF CURRENT COOL AIR IN PLACE AND AN
EXPECTED INCREASE IN CLOUDS/PRECIPITATION FROM PREVIOUS
CYCLES...FELT COMFORTABLE LOWERING MAX TEMPERATURES A FEW DEGREES
BOTH FRIDAY AND SATURDAY. THIS PLACES HIGHS BOTH DAYS IN THE 70S.

.EXTENDED...THE LOW PRESSURE THAT WILL BE AFFECTING THE AREA THIS
UPCOMING WEEKEND WILL BE IN THE PROCESS OF EXITING THE AREA ON
MONDAY.  AS THIS HAPPENS...UPPER LEVEL RIDGING WILL WORK IN FROM THE
WEST BEHIND THE TROUGH GOING INTO TUESDAY...WITH MODELS ADVERTISING
THIS RIDGE HOLDING THROUGH THE REMAINDER OF THE EXTENDED.  COOLER
TEMPS THAT HAVE HAD A HOLD ON SE MI WILL BE MUCH WARMER NEXT WEEK
WITH HIGHS GETTING BACK INTO THE MIDDLE AND UPPER 80S.

&&

.MARINE...

SURFACE HIGH PRESSURE WILL CONTINUE TO PROVIDE RELATIVELY LIGHT
WINDS OVER THE CENTRAL GREAT LAKES THROUGH FRIDAY. THE APPROACH OF A
LOW PRESSURE SYSTEM WILL THEN BRING AN INCREASE IN SOUTHEAST WINDS
FOR SATURDAY...WITH SPEEDS NOT EXPECTED TO EXCEED 15 TO 20 KNOTS.
THIS SYSTEM WILL ALSO PROVIDE A CHANCE FOR SHOWERS AND THUNDERSTORMS
FROM FRIDAY NIGHT THROUGH THE WEEKEND.

&&

.AVIATION...ISSUED 157 PM EDT THU AUG 27 2015

ORPHANED LOWER TROPOSPHERIC MOISTURE CONTINUES TO SUPPORT AN
OPTICALLY THICK STRATUS-STRATOCUMULUS DECK ACROSS SOUTHEASTERN
MICHIGAN THIS AFTERNOON. RECENT SATELLITE TRENDS SHOW LITTLE
POTENTIAL FOR CLEARING DURING THE NEXT 2 TO 4 HOURS. BELIEF IS IT
WILL NOW TAKE A SETTING SUN AND LOSS OF DIURNAL HEATING TO ALLOW
CLOUD DECK TO RAPIDLY DISSIPATE THIS EVENING. SURFACE HIGH
PRESSURE WILL THEN SUPPORT CALM WINDS AND SKC OVERNIGHT.
INTRODUCED A BR MENTION RIGHT FOR DAYBREAK FRI MORNING WITH MVFR
VSBY RESTRICTIONS. LOOKING AT MORE OF A SPARSE...FLAT CUMULUS
FIELD DEVELOPING LATE FRIDAY MORNING.

//DTW THRESHOLD PROBABILITIES...

* HIGH WITH CIGS BELOW 5000 FT THROUGH LATE AFTERNOON.

&&

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

$$

SHORT TERM...CB
LONG TERM....HLO/SS
MARINE.......HLO
AVIATION.....CB


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


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