Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000 FXUS63 KDTX 252301 AFDDTX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 701 PM EDT SAT OCT 25 2014 .AVIATION...
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//DISCUSSION... COOLING IN THE BOUNDARY LAYER AS A RESULT OF THE LOSS OF DAYTIME HEATING WILL LEAD TO DROP IN THE GUSTINESS OF THE WINDS AROUND 00Z. SUBTLE LOW LEVEL COLD AIR ADVECTION AMIDST A STRONG W-NW GRADIENT SHOULD HOWEVER SUSTAIN WIND SPEEDS IN THE 12 TO 15 KNOT RANGE THROUGH THE EVENING. ADDITIONAL NIGHTTIME COOLING AND A GRADUAL WEAKENING OF THE SURFACE GRADIENT WILL SUPPORT WIND SPEEDS DROPPING BELOW 10 KNOTS OVERNIGHT. //DTW THRESHOLD THREATS... * NONE.
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&& .PREV DISCUSSION...
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ISSUED 348 PM EDT SAT OCT 25 2014 SHORT TERM...THIS AFTERNOON AND TONIGHT SUBSIDENCE IN THE WAKE OF PASSING COLD FRONT WILL LEAD TO MAINLY CLEAR SKIES THROUGH TONIGHT. GUSTY WEST/NORTHWEST WINDS WILL ALSO RELAX WITH BOUNDARY LAYER DECOUPING THIS EVENING. THESE DECENT RADIATIONAL COOLING CONDITIONS...ALONG WITH MODEST COLD AIR ADVECTION...WILL ALLOW THE TEMPERATURES TO DROP INTO THE UPPER 30S/LOWER 40S...DESPITE THE FACT THAT MANY AREAS HAVE REACHED THE MIDDLE 60S LATE THIS AFTERNOON. WINDS WILL GUST TO 20 MPH OR BETTER INTO EARLY THIS EVENING BEFORE EASING BEGINS BY SUNSET OR SO. LONG TERM...SUNDAY THROUGH FRIDAY RIDGING WILL BRING DRY WEATHER AND ABUNDANT SUNSHINE TO SOUTHEAST MICHIGAN ON SUNDAY. HOWEVER COLD AIR WILL BE IN PLACE BEHIND THE DEPARTING COLD FRONT AS 850 MB TEMPERATURES FALL TO 3 TO 5 CELSIUS. DESPITE SUNNY SKIES THE COOLER AIRMASS WILL MEAN HIGHS WILL GENERALLY BE LIMITED TO THE MIDDLE TO UPPER 50S SUNDAY AFTERNOON. THE RIDGE WILL TRACK EAST SUNDAY NIGHT...ALLOWING FOR WARM AIR ADVECTION TO COMMENCE IN EARNEST ACROSS THE CENTRAL GREAT LAKES ON MONDAY AS 850 MB TEMPERATURES RISE TO 12 TO 14 CELSIUS. A WARM FRONT WILL LIFT NORTH THROUGH THE SOUTHERN GREAT LAKES ON MONDAY...ACTING AS A TRIGGER FOR SHOWERS AND A FEW THUNDERSTORMS...MAINLY ACROSS THE NORTH WHERE THE FRONT WILL SETTLE DURING THE AFTERNOON HOURS. A SHORTWAVE TRACKING THROUGH THE SOUTHERN GREAT LAKES WILL ASSIST IN PRECIPITATION DEVELOPMENT ON MONDAY...WITH WARM MOIST AIR AND INCREASED INSTABILITY BRINGING THE CHANCE FOR THUNDERSTORMS EMBEDDED WITHIN THE SHOWER ACTIVITY. DESPITE THE PASSAGE OF THE WARM FRONT...HIGHS WILL VARY GREATLY ON MONDAY...WITH HIGHS AROUND 60 ACROSS THE THUMB GIVEN A SOUTHEASTERLY SURFACE WIND OFF LAKE HURON...WITH HIGHS AROUND 70 NEAR THE OHIO BORDER AWAY FROM THE MAIN PRECIPITATION AND DEEPER INTO THE WARM SECTOR. THE PARENT LOW ASSOCIATED WITH THE AFOREMENTIONED WARM FRONT WILL DEVELOP OVER THE WESTERN GREAT LAKES MONDAY NIGHT...THEN TRACK EAST THROUGH THE NORTHERN GREAT LAKES TUESDAY...DRAGGING A COLD FRONT THROUGH THE CENTRAL GREAT LAKES ON TUESDAY. MODELS HAVE COME IN BETTER AGREEMENT THIS RUN...MAINLY THE ECMWF WHICH HAS COME IN FASTER THIS RUN...MORE IN LINE WITH THE GFS IN CLEARING THE FRONT THROUGH BY TUESDAY. ALTHOUGH IT IS NOT LOCK STEP WITH THE FASTER GFS SOLUTION...IT IS IN THE SAME BALL PARK TO ALLOW FOR LIKELY POPS ON TUESDAY GIVEN THE HIGHER DEGREE OF CONFIDENCE IN FROPA SOMETIME ON TUESDAY RATHER THAN A POSSIBLE FROPA SOLUTION THAT IS A WHOLE 12 HOURS APART PER THE PREVIOUS RUNS. CONTINUED INSTABILITY WILL KEEP THUNDERSTORMS IN THE FORECAST DURING THIS TIME PERIOD UNTIL THE COLD FRONT CLEARS THE AREA. WITH THE BETTER MODEL AGREEMENT...IT APPEARS RAIN CHANCES WILL BE OFF TO THE WEST BY TUESDAY NIGHT GIVEN THE SUBSIDENCE BEHIND THE DEPARTING FRONT. THEREFORE WILL DRY OUT THE FORECAST ON TUESDAY NIGHT...WITH RIDGING EXPECTED TO KEEP THE WEATHER DRY INTO WEDNESDAY AS A SHOT OF COOL DRY AIR SENDS AFTERNOON HIGHS BACK DOWN INTO THE LOWER TO MIDDLE 50S ON WEDNESDAY. A WEAK LOW PRESSURE SYSTEM IS THEN ON TRACK TO AFFECT THE CENTRAL GREAT LAKES DURING THE LATER PART OF THE WORK WEEK. GIVEN THE WEAK NATURE OF THIS LOW PRESSURE SYSTEM IT IS NOT SURPRISING THAT THE MODELS ARE HAVING A HARD TIME RESOLVING THE TIMING AND IMPACT OF THIS LOW PRESSURE SYSTEM. THERE ARE HINTS THAT THIS SYSTEM COULD BRING THE FIRST TASTE OF WINTER TO SOUTHEAST MICHIGAN LATE IN THE WEEK...WITH SOME SNOW FLAKES POSSIBLE ACROSS THE AREA. HOWEVER THE AFOREMENTIONED ISSUES WITH THE EXACT TIMING AND STRENGTH OF THIS SYSTEM DOES NOT LEND ITSELF TO A GREAT DEGREE OF CONFIDENCE THIS FAR OUT...BUT IT DOES BEAR WATCHING WITH THE UPCOMING HALLOWEEN HOLIDAY AT THE VERY END OF THE EXTENDED FORECAST. THE MAIN FEATURE IN THE EXTENDED FORECAST IS A DEVELOPING MID LATITUDE CYCLONE ACROSS THE UPPER MISSISSIPPI VALLEY. THIS SYSTEM WILL DEEPEN FROM 1002 TO 994 MB AS THE LOW AND ATTENDANT COLD FRONT CROSS MICHIGAN ON TUESDAY. COOL TEMPERATURES AND DRY CONDITIONS WILL THEN SETTLE IN FOR THE MIDDLE OF THE WEEK UNTIL THE NEXT MID LEVEL WAVE BRINGS ADDITIONAL RAIN CHANCES THURSDAY AND FRIDAY. CONFIDENCE IS LOW OUTSIDE OF THE TUESDAY RAIN EVENT. MARINE... A STRONG LOW NEAR JAMES BAY WILL CAUSE NORTHWEST WINDS TO RAMP UP OVER AREA WATERS THIS EVENING. THE STRONGEST WINDS WILL BE OVER THE NORTHERN HALF OF LAKE HURON WHERE A COLDER AIRMASS WILL SUPPORT WINDS GUSTING TO LOW-END GALES. IN ADDITION...SMALL CRAFT ADVISORIES ARE IN EFFECT FOR THE EXPOSED NEARSHORE WATERS OF THE THUMB WHERE SIGNIFICANT WAVES HEIGHTS ARE EXPECTED TO BUILD TO SEVERAL FEET.
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&& .DTX WATCHES/WARNINGS/ADVISORIES...
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MI...NONE. LAKE HURON... SMALL CRAFT ADVISORY...OUTER SAGINAW BAY AND THE NEARSHORE WATERS FROM PORT AUSTIN TO PORT SANILAC...FROM 10 PM SATURDAY TO 4 PM SUNDAY. LAKE ST CLAIR...NONE. MI WATERS OF LAKE ERIE...NONE.
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&& $$ AVIATION.....SC SHORT TERM...DG LONG TERM....JVC/MM MARINE.......JVC YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).

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