Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 270635
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
235 AM EDT THU AUG 27 2015

.SHORT TERM...TODAY AND TONIGHT

SURFACE HIGH PRESSURE WILL CONTINUE TO DRIFT SLOWLY EASTWARD THROUGH
THE AREA TODAY AND THEN CENTER OVER THE EASTERN GREAT LAKES TONIGHT.
STRATUS HAS BEEN EVER SO STEADILY ERODING AS DRIER AIR ASSOCIATED
WITH THIS HIGH FILTERS INTO THE AREA. GENERALLY EXPECT THIS SLUGGISH
TREND TO CONTINUE INTO THE EARLY MORNING HOURS...BUT LOW LEVEL
MOISTURE WILL LIKELY BE SUFFICIENT ENOUGH TO FORM A SCATTERED TO
BROKEN CUMULUS OR STRATO-CU DECK FROM MID MORNING INTO MID TO LATE
AFTERNOON BEFORE FINALLY CLEARING OUT FOR GOOD BETWEEN 21Z-01Z.

WILL MAINTAIN RELATIVELY COOL CONDITIONS TODAY AS BOUNDARY LAYER
MIXING WILL BE WEAK UNDER THE SURFACE RIDGE...AND SOLAR INSOLATION
WILL BE MODEST GIVEN PERIODS OF BROKEN DIURNAL CU/STRATO-CU. HIGHS
IN THE LOWER 70S STILL SEEMS ON TRACK FOR MOST OF AREA WITH PERHAPS
A POCKET OF UPPER 60S OVER THE THUMB WHERE CLOUDS WILL BE SLOWEST TO
BREAK UP. WITH GENERALLY CLEAR SKIES THEN PERSISTING FROM THIS
EVENING INTO THE OVERNIGHT HOURS...LOWS SHOULD FALL WELL INTO THE
50S IN MANY LOCATIONS...ONLY HOLDING IN THE UPPER 50S WITHIN THE
CORE URBAN HEAT ISLAND OF METRO DETROIT.

&&

.LONG TERM...FRIDAY THROUGH WEDNESDAY

SURFACE RIDGE OF HIGH PRESSURE WILL HAVE FRIDAY START MOSTLY SUNNY.
SHOULD BE SOME CU TO DEVELOP IN THE AFTERNOON AS A FAIRLY DENSE CI
SHIELD MOVES IN LATE ON FRIDAY AHEAD OF THE NEXT SYSTEM. STILL
ENOUGH SUN TO GO WITH THE WARMER MET GUIDANCE NUMBERS.

FOR FRIDAY NIGHT THROUGH THE WEEKEND...LITTLE CONFIDENCE IN THE
EVOLUTION OF THAT NEXT SYSTEM. THE SHORTWAVES WERE OVER THE ROCKY
MOUNTAINS EARLY THIS MORNING...GOING THROUGH ONE CONVECTIVE CYCLE AT
THIS TIME. THIS SYSTEM WILL HAVE TWO MORE CONVECTIVE CYCLES LATER
TODAY AND FRIDAY BEFORE MOVING INTO THE GREAT LAKES REGION FOR THE
WEEKEND. MODELS BARE THIS OUT AS SOLUTIONS RANGE FROM THE MORE
CONSOLIDATED UPPER FEATURES OF THE NAM AND ECMWF...THE WEAKENING
STRONGER WAVES OF THE GFS...TO THE MORE SEPARATE AND MUCH WEAKER
SHORTWAVES OF THE GEM. FOR THIS FORECAST WILL FOCUS ON LATER FRIDAY
NIGHT WITH THE FRONTAL FORCING...MOISTURE ADVECTION AND UPPER JET
SUPPORT SOMEWHERE BETWEEN THE BRIDGE AND MBS. THIS WILL HAVE THE
HIGHEST POPS IN THE NW CORNER OF THE FORECAST AREA WITH LESSER POPS
TO THE SOUTH AND EAST.

ON SATURDAY...THE SHORTWAVES WILL BE MOVING TO AT LEAST WESTERN
LOWER MICHIGAN. WITH MLCAPES FROM 500-1000 J/KG...SHOWERS AND
THUNDERSTORMS LOOK TO BE INCREASINGLY LIKELY ESPECIALLY FOR THE
AFTERNOON. WILL HAVE LIKELY POPS FOR AREAS NORTH AND WEST OF A
HARBOR BEACH TO CHELSEA LINE...AND THEN CHANCE POPS TO THE SOUTH AND
EAST.

SEVERE WEATHER NOT ANTICIPATED TO BE MUCH OF AN ISSUE AS 6KM BULK
SHEAR WILL BE AROUND 30KTS WITH THAT LIMITED INSTABILITY.
PRECIPITABLE WATERS DO INCREASE TO AT LEAST 1.5 INCHES...AND SOME
INDICATION WILL BE NORTH OF 1.75 INCHES. THE SLOWER MOVEMENT OF THE
SHORTWAVES WILL ALSO KEEP THE LOW LEVEL JET PINNED ON THE BOUNDARY
THAT WILL BE LYING FROM SOME SORT OF A WEST TO EAST LINE ACROSS
LOWER MICHIGAN.  COULD BE SOME LOCALLY HEAVY RAINFALL IN THIS
ENVIRONMENT.

THE MAIN SHORTWAVE WEAKENS AND SHEARS OUT FROM SATURDAY INTO
SUNDAY...LEAVING THE 500 MB TROF OVER THE REGION. LESS FORCING WILL
LEAD TO JUST SLIGHT CHANCE OR CHANCE POPS ON SUNDAY AND SUNDAY
EVENING WITH THE HIGHEST FOR THE SOUTHEAST HALF OF THE FORECAST
AREA.

BUILDING HEIGHTS AS THE 500 MB RIDGE SETS UP OVER THE GREAT LAKES ON
TAP FROM MONDAY THROUGH MUCH OF NEXT WEEK. FORECAST WILL GENERALLY
BE DRY AND WARM ALTHOUGH THE RIDGE CONTINUES TO BE NOT AS STRONG AS
SOME EARLIER MODEL FORECASTS. IN FACT...SOME WEAKNESS IN THE HEIGHT
FIELD TO OUR SOUTH THROUGH THE EXTENDED PERIOD MAY BE ENOUGH TO
BRING SOME AFTERNOON/EVENING THUNDERSTORMS...BUT CHANCES ARE TOO LOW
TO INCLUDE AT THIS TIME IN THE EXTENDED FORECAST.

&&

.MARINE...

LAST FEW HOURS OF INFLUENCE FROM THE HUDSON BAY LOW...WITH
CLOUDS...A FEW LIGHT SHOWERS AND A CHANCE OF WATERSPOUTS THROUGH 14Z
THIS MORNING. SURFACE HIGH PRESSURE CONTINUES TO BUILD INTO THE
CENTRAL LAKES TODAY BRINGING MORE TRANQUIL CONDITIONS. LIGHT WINDS
WILL CONTINUE AS THE SURFACE HIGH MAINTAINS CONTROL THROUGH FRIDAY
EVENING. THE NEXT LOW PRESSURE SYSTEM WILL START TO BRING STRONGER
SOUTHEASTERLY FLOW LATE FRIDAY NIGHT INTO SATURDAY.  THIS TIME FRAME
WILL ALSO BE THE NEXT CHANCE OF SHOWERS AND STORMS WITH THE
APPROACHING LOW PRESSURE SYSTEM.

&&

.AVIATION...ISSUED 1146 PM EDT WED AUG 26 2015

DEFINITIVE CLEARING TREND OVER CENTRAL AND WESTERN LOWER MICHIGAN
THIS EVENING WHILE STRATUS IS SLOWER TO ERODE FOR KMBS AND POINTS
NORTH WHERE CONDITIONS REMAIN MORE FAVORABLE FOR STRATUS MAINTENANCE
IN THE SHORT TERM. AS SUCH, THE PERIOD BEGINS WITH EXPECTATION FOR
SCATTERED COVERAGE AT KFNT/KPTK WITH EXTRAPOLATION SUGGESTING THE
DETROIT SITES TO SCATTER AROUND AN HOUR LATER...APPROX 07Z. SEVERAL
HOURS OF SKC-SCT COVERAGE WILL BE POSSIBLE BEFORE DEVELOPMENT OF
MVFR CIG WITH ONSET OF DIURNAL HEATING THIS MORNINGS. CEILINGS WILL
LIFT TO LOW VFR DURING THE DAY. LIGHT NW TO NNW WINDS THIS MORNING
WILL BECOME VARIABLE UNDER HIGH PRESSURE THIS AFTN.

FOR DTW...EXPECT CLEARING AT KDTW BY AROUND 07Z. ONCE CIGS SCATTER
EXPECT CLEAR OR NEARLY CLEAR SKIES TO DOMINATE UNTIL DIURNAL
STRATOCU DEVELOPMENT GETS UNDERWAY. BEST ESTIMATE FOR CIG
REDEVELOPMENT IS 14-15Z.

//DTW THRESHOLD PROBABILITIES...

* HIGH FOR CIGS AOB 5KFT THROUGH 7Z. LOW 07Z-14Z. MEDIUM AFTER 14Z.

&&

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

$$

SHORT TERM...DG
LONG TERM....RBP
MARINE.......RBP
AVIATION.....JVC


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


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