Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 060722
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
322 AM EDT MON JUL 6 2015

.SHORT TERM...TODAY AND TONIGHT

SOUTHEAST MI WILL LIE BETWEEN A WEAK UPPER LOW MEANDERING ACROSS THE
UPPER OHIO VALLEY/CNTL APPALACHIANS AND AN AMPLIFYING NRN STREAM
TROUGH/FRONTAL SYSTEM SLIDING FROM THE UPPER MIDWEST INTO THE WRN
GREAT LAKES TODAY THROUGH THIS EVENING. ENHANCED LARGE SCALE
SUBSIDENCE TO THE NORTHWEST OF THE UPPER OHIO VALLEY LOW HAS LED TO
AN ARC OF WARM MID LEVEL TEMPS ACROSS SE MI. THIS CAP IS SHOWN
NICELY ON THE 00Z DTX SOUNDING. THESE WARM MID LEVEL TEMPS WILL HOLD
ACROSS SE MI TODAY THROUGH THIS EVENING...SUPPORTING A DRY FORECAST
AND LIKELY SUPPRESSING DIURNAL CU DEVELOPMENT. SO OUTSIDE OF A FEW
CIRRUS...AMPLE SUNSHINE CAN BE EXPECTED TODAY. THE SPEED OF THE
UPSTREAM FRONTAL SYSTEM HAS SLOWED SOMEWHAT COMPARED TO PREVIOUS
MODEL SOLUTIONS. THIS WILL RESULT IN A SLOWER DEPARTURE OF THE
SURFACE RIDGE EXTENDING ACROSS THE ERN GREAT LAKES TODAY AND
SLOWER ARRIVAL OF THE BETTER SW FLOW/LOW LEVEL WARM AIR ADVECTION.
THIS WARRANTS LOWERING FCST AFTERNOON HIGHS DOWN A COUPLE
DEGREES...WITH LOW TO MID 80S ACROSS MUCH OF SE MI /UPPER 80S
STILL POSSIBLE ACROSS THE SAGINAW VALLEY WHERE LOW LEVEL SW FLOW
STRENGTHENS LATE IN THE AFTERNOON/.

THE APPROACH OF THE FRONTAL SYSTEM WILL INCREASE THE LOW LEVEL S/SW
FLOW TONIGHT /925MB WIND FCST TO INCREASE TO 30-40 KNOTS OVERNIGHT/.
THIS WILL INHIBIT THE DEGREE OF DECOUPLING IN THE BOUNDARY LAYER.
THIS COMBINED WITH LOW LEVEL WARM AIR ADVECTION AND RISING SFC
DEWPOINTS OVERNIGHT WILL SUPPORT MILD MIN TEMPS /AROUND 70 IN MOST
PLACES/. ALTHOUGH THE SFC COLD FRONT IS NOT FORECAST TO MOVE INTO
CNTL LOWER MI UNTIL 12Z TUES...THE LEAD EDGE OF THE DEEP LAYER MOIST
AXIS WILL MOVE INTO SE MI LATE TONIGHT. THIS WILL SUPPORT A CHANCE
OF SOME SHOWERS /POSSIBLE THUNDERSTORMS/ PRIOR TO DAYBREAK.
RELATIVELY SHALLOW MID LEVEL LAPSE RATES AND LINGERING WARM MID
LEVEL TEMPS WILL HOWEVER BE BIG LIMITING FACTORS TO CONVECTION
TONIGHT...ESPECIALLY ACROSS THE ERN HALF OF THE FORECAST AREA.

&&

.LONG TERM...

STRONG UPPER WAVE TRACKING THROUGH FAR NORTHERN MONTANA EARLY THIS
MORNING...SLIPPING THROUGH LAKE SUPERIOR AND INTO ONTARIO DURING
TUESDAY. BULK OF UPPER LEVEL SUPPORT WILL BE NORTH OF SOUTHEAST
MICHIGAN...BUT STRONG MID/UPPER LEVEL WESTERLIES TO KEEP THE FRONT
PROGRESSING EAST THROUGH THE CENTRAL GREAT LAKES DURING
TUESDAY. MOISTURE AXIS/850-700 MB THETA-E AXIS PROGGED TO BE
ALONG OR EAST OF US-23 BY 18Z TUESDAY...WITH VERY IMPRESSIVE
DRYING THEN OCCURING TOWARD 00Z...AS PW VALUES FALL FROM 2 INCHES TO
AROUND 0.5 INCH. THE 00Z NAM LOOKS WAY OVERDONE WITH THE
INSTABILITY. THE SURFACE COLD FRONT IS DISPLACED FROM THE MID LEVEL
COLD AIR...AS 500 MB TEMPS LOOK TO BE RUNNING AROUND -5 C.
THUS...MID LEVEL LAPSE RATES (700-500 MB) WILL BE WEAK...AROUND 5
C/KM. NAM IS SURGING SURFACE DEW PTS INTO THE MID 70S...WHICH IS
PROBABLY A GOOD 5 DEGREES TOO HIGH...ALONG WITH THE SURFACE TEMPS
WHICH ARE BEING ADVERTISED TO TOP OUT AROUND 90 DEGREES. AT THE
OTHER EXTREME...THE 00Z GFS IS SHOWING BARELY ANY INSTABILITY...WITH
SBCAPES ONLY RISING TO AROUND 500 J/KG. THIS DOES NOT GIVE A LOT OF
CONFIDENCE IN SHOWERS/THUNDERSTORMS...BUT LOW LEVEL CONVERGENCE
LOOKS GOOD AND DUE TO THE HIGH AMOUNT OF MOISTURE AND FAVORABLE
TIMING (THOUGH NOT IDEAL)...HIGH LIKELY POPS WILL BE
FORECASTED...WITH A NORTHWEST-SOUTHEAST HIGH TEMPERATURE GRADIENT
OF MID 70S TO MID 80S.

HIGH PRESSURE WILL PASS THROUGH THE CENTRAL GREAT LAKES ON
WEDNESDAY...WITH 850 MB TEMPS IN THE HIGH SINGLE NUMBERS (PER 00Z
EURO) POINTING TO HIGHS IN THE LOW TO MID 70S.

UPPER WAVE IN FOUR CORNERS REGION AND ASSOCIATED MOISTURE WILL
QUICKLY BE RACING OFF TO THE NORTHEAST...WITH ASSOCIATED SURFACE
LOW/REFLECTION FORECASTED TO SKIRT ALONG THE SOUTHERN MICHIGAN
BORDER ON THURSDAY...WITH THE 00Z CANADIAN EVEN FASTER...SUPPORTING
WARM FRONTAL PRECIPITATION LATE WEDNESDAY. AS TOUGH AS IT IS TO
BELIEVE WITH THE AMOUNT OF DRY AIR WHICH MOVES INTO LOWER MICHIGAN
TUESDAY NIGHT/WEDNESDAY...AN INCREASING CHANCE OF SHOWERS SEEMS
WARRANTED WEDNESDAY NIGHT INTO THURSDAY WITH THE BIG INCREASE IN
MOISTURE TRANSPORT.

&&

.MARINE...

WARM SOUTHERLY FLOW TODAY BETWEEN 10 AND 20 KNOTS AHEAD OF A COLD
FRONT...WHICH WILL MOVE THROUGH TOMORROW...TRIGGERING SHOWERS AND
THUNDERSTORMS. NORTHWEST TO NORTH WINDS BEHIND THE FRONT LOOK TO TOP
OUT AROUND 20 KNOTS TUESDAY EVENING...BUT THEN DIMINISHING TUESDAY
NIGHT INTO WEDNESDAY AS HIGH PRESSURE RETURNS. LOW PRESSURE WILL
LIFT UP FROM THE SOUTH AS WE HEAD TOWARD THURSDAY...BUT THE STRENGTH
OF THIS LOW IS IN QUESTION.

&&

.AVIATION...ISSUED 1158 PM EDT SUN JUL 5 2015

EXPANSIVE HIGH PRESSURE SURFACE AND ALOFT OVER THE EASTERN GREAT
LAKES WILL PROMOTE CALM WIND FROM PTK SOUTHWARD AND ONLY ALLOW A FEW
STREAMERS OF CIRRUS COVERAGE TONIGHT OVER ALL AREAS. THE LACK OF
WIND AND CLEARING SKY CONTINUES TO SUPPORT MVFR HAZE/FOG LATE IN THE
NIGHT TOWARD MID MORNING. A LATE AND LIGHT INCREASE IN GRADIENT WIND
IN THE MBS AREA DOWN TOWARD FNT WILL MAKE MVFR MORE DIFFICULT TO
MAINTAIN. THE WIND WILL THEN INCREASE SLIGHTLY FROM THE SOUTHWEST
OVER ALL AREAS DURING THE AFTERNOON AS THE NEXT FRONTAL SYSTEM MOVES
INTO THE WESTERN GREAT LAKES AND MIDWEST. THIS WILL RESULT IN A MIX
OF SHALLOW CUMULUS AND INCREASING HIGH CLOUDS INTO MONDAY EVENING
BUT NO PRECIPITATION BEFORE MIDNIGHT.

FOR DTW... INCOMING MODEL SOUNDINGS APPEAR MORE FAVORABLE FOR
FOG/HAZE COMPARED TO THE LAST FEW NIGHTS. THIS COMBINED WITH RECENT
OBSERVATIONAL TRENDS SUPPORTS A PREVAILING MVFR RESTRICTION FROM
LATER IN THE NIGHT TOWARD MID MORNING.

//DTW THRESHOLD PROBABILITIES...

* NONE.

&&

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

$$

SHORT TERM...SC
LONG TERM....SF
MARINE.......SF
AVIATION.....BT


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


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