Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000 FXUS63 KDTX 201010 AFDDTX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 610 AM EDT MON OCT 20 2014 .AVIATION... //DISCUSSION... A STEADY INCREASE IN LOWER LEVEL MOISTURE WILL RESULT IN A LOWERING CEILING THROUGH THE DAYLIGHT PERIOD. RECENT OBSERVATIONS UPSTREAM SUGGEST CONDITIONS WILL REMAIN IN VFR AS AN INITIAL ROUND OF LIGHT SHOWERS EXITS THE REGION. MVFR CONDITIONS MOST LIKELY ARRIVE IMMEDIATELY IN ADVANCE OF AND ALONG A COLD FRONTAL PASSAGE MID- LATE AFTERNOON. POTENTIAL FOR CEILINGS TO DIP BELOW 2000 FT OVERNIGHT AS A PERIOD OF DEEPER SATURATION COMMENCES. PRE-FRONTAL SOUTHWEST WINDS WILL SHIFT TO NORTHWESTERLY WITH THE FRONTAL PASSAGE. //DTW THRESHOLD THREATS... * LOW CONFIDENCE IN CEILINGS BELOW 5000 FEET THIS MORNING...HIGH CONFIDENCE THIS AFTERNOON. && .PREV DISCUSSION...ISSUED 353 AM EDT MON OCT 20 2014 SHORT TERM...TODAY AND TONIGHT THE 00Z KDTX RAOB SOUNDING SHOWED A CONTINUED DRY AIRMASS...HOWEVER IT WAS SLOWLY MOISTENING FROM THE TOP DOWN. THIS MOISTENING WILL CONTINUE DURING THE EARLY MORNING HOURS AS 295K ISENTROPIC ASCENT MOISTENS UP THE REMAINING LOW LEVELS OF THE ATMOSPHERE. ONCE THIS OCCURS SHOWERS ARE EXPECTED TO DEVELOP LATE THIS MORNING INTO THE EARLY AFTERNOON AS A COLD FRONT PUSHES THROUGH WITH A DECENT MID LEVEL SHORTWAVE EMBEDDED IN A MID LEVEL TROUGH TRACKING THROUGH THE CENTRAL GREAT LAKES. THERE APPEARS TO BE A FAIRLY DECENT RESPONSE UPSTREAM WITH THE ACTIVITY CURRENTLY OFF TO THE NORTH AND WEST. WITH CAPES OF A FEW HUNDRED J/KG A FEW RUMBLES OF THUNDER ARE NOT OUT OF THE QUESTION. GIVEN THE UPSTREAM RESPONSE AND DECENT DYNAMICS WILL CONTINUE WITH THE INHERITED HIGH LIKELY POPS ACROSS MUCH OF THE AREA TODAY. TEMPERATURES AHEAD OF THE COLD FRONT WILL GET INTO THE MIDDLE TO UPPER 50S TODAY. BEHIND THE COLD FRONT LIGHT SHOWERS AND DRIZZLE WILL PERSIST DURING MUCH OF THE OVERNIGHT HOURS AS ABUNDANT LOW LEVEL MOISTURE MAINTAINS A LOW STRATUS DECK BEHIND THE COLD FRONT. LOWS TONIGHT WILL REMAIN IN THE MIDDLE 40S UNDERNEATH THE FAIRLY SOLID OVERCAST DECK. LONG TERM... TUESDAY THROUGH SUNDAY EXITING UPPER WAVE ANCHORING THE BROADER MID LEVEL TROUGH AMPLIFICATION WILL CLOSE OFF AS IT SETTLES INTO THE MID ATLANTIC REGION THROUGH THE MID WEEK PERIOD. THE EXTENSIVE TRAILING MOIST CYCLONIC FLOW WILL WASH ACROSS SE MICHIGAN ON TUESDAY. THIS REALIGNMENT IN THE PRESSURE GRADIENT WILL ESTABLISH A FIRM NORTH-NORTHEAST FLOW...EFFECTIVELY PLACING THE EXISTING LOW LEVEL THERMAL TROUGH /-2C AT 850 MB/ OVER THE REGION THROUGHOUT THE DAY. THIS ENVIRONMENT WILL SUSTAIN AN EXTENSIVE STRATOCU FIELD...AND LIKELY SUPPORT SOME DEGREE OF LIGHT SHOWER PRODUCTION /PARTICULARLY EARLY/. TEMPERATURES WILL STRUGGLE TO RESPOND...HIGH TEMPERATURE READINGS CAPPED AT AROUND 50 DEGREES. EXISTING 925 MB THERMAL TROUGHING WILL BE SLOW TO RELEASE EASTWARD...SUGGESTING A VERY SLOW CLEARING PROCESS /IF AT ALL/ TUESDAY NIGHT AS A FAVORABLE MEAN FLOW OFF LAKE HURON REINFORCES THE A MOIST SUB-INVERSION LAYER. THIS WILL PUT A LID ON THE DEGREE OF NOCTURNAL COOLING...ESPECIALLY ACROSS EASTERN SECTIONS. GREATEST POTENTIAL FOR CLEARING WILL BE OVER THE TRI-CITIES. THIS WILL TRANSLATE INTO A BROADER SPECTRUM OF LOW TEMPERATURES...MID 30S WEST TO UPPER 30S/LOWER 40S EAST. DEEPER NORTHERLY FLOW WILL REMAIN IN PLACE THROUGH WEDNESDAY...THE REGION STILL WITHIN THE EXTENSIVE OUTER PERIPHERY OF EAST COAST MID LEVEL CIRCULATION. MID LEVEL SUBSIDENCE WILL BE ON THE INCREASE... WHILE A STEADY DRYING OF THE BOUNDARY LAYER COMMENCES UNDER EXPANDING LOW LEVEL ANTICYCLONIC FLOW. THIS SHOULD YIELD AT LEAST PARTIAL SUNSHINE...BUT OTHERWISE LEAVE THE EXISTING AIRMASS WITH LITTLE REASON TO MODERATE MORE THAN SEVERAL DEGREES RELATIVE TO HIGHS ON TUESDAY /LOWER 50S/. DRY/STABLE ENVIRONMENT WITH THE OVERALL AIRMASS MAKING A MORE NOTEWORTHY UPWARD JUMP IN TEMPERATURES STARTING THURSDAY AS LOW AND MID LEVEL RIDGING TAKE HOLD. WEAKENING SHORTWAVE WORKING THROUGH THE ELEVATED HEIGHT FIELD WILL SHEAR THROUGH THURSDAY NIGHT...PROVIDING THE ONLY POSSIBLE WRINKLE FOR THE END OF THE WORK WEEK. LITTLE FORCING BEHIND THIS AXIS TO SUGGEST ANYTHING MORE THAN PERHAPS SOME INCREASE IN MID CLOUD AND A FEW SPRINKLES THURSDAY NIGHT/FRIDAY MORNING. A PERIOD OF STRONGER WARM AIR ADVECTION CURRENTLY APPEARS TO CENTER ON THE FRIDAY AND FRIDAY NIGHT PERIOD /IN THE WAKE OF THIS WAVE/...850 MB TEMPERATURES MAKING A RUN TOWARD THE LOWER TEENS. THIS POINTS TO A BRIEF WARMUP INTO THE FIRST HALF OF THE WEEKEND. MARINE... MODEST SOUTHWEST WINDS WILL EXIST TODAY IN ADVANCE OF A COLD FRONT. THIS FRONT WILL RESULT IN SOME SHOWER DEVELOPMENT THROUGH TONIGHT. WINDS WILL VEER TO NORTHEAST AS LOW PRESSURE CONTINUES TO MOVE TOWARD THE ATLANTIC COAST AND AS HIGH PRESSURE BUILDS ACROSS NORTHERN ONTARIO. THE COMBINATION OF A STRONGER GRADIENT AND ONSHORE FLOW WILL BRING A PERIOD OF GUSTY WIND AND BUILDING WAVES THROUGHOUT CENTRAL AND SOUTHERN LAKE HURON THROUGH TUESDAY. THE POTENTIAL FOR GUSTS AROUND 30 KNOTS LOOKS SOLID WITH A LOWER PROBABILITY FOR BRIEF GUSTS TO GALES EARLY TUESDAY. THE COLDER AIR OVER THE WARM LAKE WATER WILL YIELD STRONG INSTABILITY BUT MAY ALSO LIMIT THE POTENTIAL FOR GALE FORCE GUSTS BY ALTERING THE PRESSURE FIELD AND LIMITING THE GRADIENT FLOW. NO GALE HEADLINES ARE PLANNED AT THIS TIME... SMALL CRAFT ADVISORIES WILL BE ISSUED FOR ALL NEARSHORE WATERS OF LAKE HURON INCLUDING SAGINAW BAY. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON... SMALL CRAFT ADVISORY...OUTER SAGINAW BAY AND THE NEARSHORE WATERS FROM PORT AUSTIN TO HARBOR BEACH...FROM 5 AM TUESDAY TO 6 AM WEDNESDAY. SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM HARBOR BEACH TO PORT HURON...FROM 8 AM TUESDAY TO 6 AM WEDNESDAY. SMALL CRAFT ADVISORY...INNER SAGINAW BAY...FROM 8 AM TUESDAY TO 10 PM TUESDAY. LAKE ST CLAIR...NONE. MI WATERS OF LAKE ERIE...NONE. && $$ AVIATION.....99 SHORT TERM...KURIMSKI LONG TERM....MR MARINE.......MR YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).

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