Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000 FXUS63 KDTX 271050 AFDDTX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 550 AM EST FRI FEB 27 2015 .AVIATION...
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SURFACE HIGH PRESSURE BUILDING EASTWARD INTO THE REGION WILL CONTINUE TO SUPPORT A VERY DRY AIR MASS. WIND DIRECTIONS ARE FORECASTED TO EMERGE SOUTHWESTERLY TODAY...BRINGING THE POTENTIAL FOR LAKE MICHIGAN MOISTURE TO WORK UNDER THE INVERSION BASE AT 4-5 KFT AGL. MODEL SOUNDINGS ALSO SUPPORT A DIURNAL COMPONTENT TO POTENTIAL CLOUD COVER. DOWNSTREAM TRAJECTORY CONTINUES TO SUPPORT THE BEST POTENTIAL FOR THE NORTHERN TAF SITES. //DTW THRESHOLD PROBABILITIES... * LOW CONFIDENCE IN CEILING BELOW 5000 FT FRIDAY AFTERNOON.
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&& .PREV DISCUSSION...
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ISSUED 358 AM EST FRI FEB 27 2015 SHORT TERM...TODAY AND TONIGHT RECORD LOWS FOR FEB 27 DETROIT AREA: -4 (1934) FLINT AREA: -14 (1994) SAGINAW: -8 (1934) ANOTHER COLD MORNING ACROSS SOUTHEASTERN MICHIGAN WITH AN ARCTIC SURFACE RIDGE LOCKED IN OVERHEAD. NIL WIND AND CLEAR SKIES HAS LED TO FAVORABLE RADIATIVE COOLING CONDITIONS. SURFACE TEMPERATURES CURRENTLY RANGE FROM 0 TO 10 DEGREES BELOW ZERO AS OF 3AM. WITH A LACK OF LOW CLOUD DISCERNIBLE IN IR IMAGERY...EXPECTATIONS ARE FOR SURFACE TEMPERATURES TO CONTINUE TO BOTTOM OUT BEFORE SUNRISE WITH MANY RURAL LOCATIONS REACHING 10 TO 20 DEGREES BELOW ZERO. WITH A DECOUPLED SURFACE LAYER...WILL HONOR THE DECISION OF PRIOR SHIFTS AND NOT ISSUE A WIND CHILL ADVISORY. COLDEST MIDLEVEL TEMPERATURES PUSHING OUT OF THE STATE TODAY IN COMBINATION WITH AN SURFACE ANTICYCLONE PUSHING INTO PORTIONS OF OHIO WILL ALLOW WIND DIRECTIONS OVER SOUTHEASTERN MICHIGAN TO MAKE A CONCERTED MOVE TO SOUTHWESTERLY. ENHANCED MOISTURE AND LAKE MICHIGAN CLOUD DEBRIS IS PROGGED TO STREAM EASTWARD WITH TIME...SHOWN TO SLIDE THROUGH PORTIONS OF THE CWA BY THIS AFTERNOON AND INTO THE EARLY EVENING. RAP SOUNDINGS SUGGEST THERE WILL BE A CONSIDERABLE DIURNAL COMPONENT TO ANY SKY COVER. WIND TRAJECTORIES POINT TO THE NORTHERN CWA/SAGAINAW VALLEY AS THE MORE FAVORABLE LOCATION FOR CLOUDS. WITH SUN...SHADED A DEGREE OR TWO HIGHER THAN MOS GUIDANCE FOR HIGHS. SURFACE HIGH PRESSURE PUSHING THROUGH INDIANA AND OHIO WILL SET ANOTHER NIGHT UP FOR CALM WINDS ACROSS THE SOUTHERN HALF OF THE CWA. LOWERED MINS FOR AREAS SOUTH OF DETROIT. OTHERWISE...A PRESSURE GRADIENT IN PLACE OVER THE TRI CITIES/NORTHERN THUMB AND SOME POTENTIAL FOR LINGERING CLOUDS LIMITS THE TEMPERATURE FALL POTENTIAL FOR TONIGHT. LONG TERM... COLD AIRMASS WILL REMAIN IN PLACE INTO EARLY THIS WEEKEND ALTHOUGH TEMPERATURES WILL MODERATE EVER SO SLIGHTLY AS THE LATEST ARCTIC HIGH PRESSURE SHIFTS TO THE EAST OF THE AREA SATURDAY NIGHT. HIGHS ON SATURDAY WILL CLIMB TO AROUND 20F WITH LOWS THAT NIGHT HOLDING INTO THE SINGLE DIGITS TO NEAR 10F AS BOTH THE COLDEST AIR SHIFTS EAST AND EXPANDING CLOUD COVER WORKS INTO THE AREA WITH THE APPROACH OF A LOW PRESSURE SYSTEM. 00Z MODEL RUNS...SAVE THE NAM12...BASICALLY SUPPORT THE PREVIOUS FORECAST AS ROUGHLY 1 TO 2 INCHES OF SNOW FALL FROM THE I-69 CORRIDOR NORTH LATE SATURDAY NIGHT INTO EARLY SUNDAY EVENING WITH 2 TO 3 INCHES SOUTH OF THAT INTO METRO DETROIT AS H7 SPECIFIC HUMIDITY CLIMBS TO AROUND 2 G/KG ALONG THE M-59 CORRIDOR. GIVEN THE RELATIVELY HIGH SNOW TO LIQUID RATIOS EXPECTED WITH THE COLD AIRMASS IN PLACE...15:1 OR A BIT MORE...WOULD NOT BE SURPRISED TO SEE UP TO 4 INCHES FROM THE I-94 CORRIDOR SOUTHWARD. TEMPERATURES WILL EDGE BACK DOWN EARLY NEXT WEEK...BUT TO MUCH MORE REASONABLE LEVELS THAN THE PAST SEVERAL WEEKS AS HIGHS MONDAY REACH THE MID/UPPER 20S AND LOWS HOLD IN THE TEENS SUNDAY AND MONDAY NIGHT. THE NEXT LOW PRESSURE SYSTEM APPEARS TO BE SHAPING UP TO BE A STRONGER SYSTEM THAN THE WEEKEND EVENT...WITH A TRACK THAT WOULD SUPPORT A WIDE VARIETY OF PRECIPITATION ACROSS THE CWA ON TUESDAY WITH PRIMARILY SNOW OVER THE NORTHERN CWA AND SNOW CHANGING TO A MIX AND THEN EVENTUALLY RAIN FURTHER SOUTH. WITH THE EVENTUAL TRACK AND STRENGTH OF THIS SYSTEM STILL IN DOUBT...WILL FORGO ANY SIGNIFICANT DETAILS AT THIS TIME...OTHER THAN TO INCLUDE SOME MENTION OF SLEET...FREEZING RAIN AND RAIN AS 00Z RUNS OF THE GFS...CMC AND ECMWF DO NOT SUPPORT AN ALL SNOW EVENT FOR THE ENTIRE CWA. MARINE... HIGH PRESSURE WILL BE BUILD FROM THE MID MISSISSIPPI VALLEY TODAY THROUGH THE OHIO VALLEY ON SATURDAY. MODEST SOUTHWEST RETURN FLOW WILL DEVELOP AROUND THIS HIGH OVER THE CENTRAL GREAT LAKES. CENTRAL SECTIONS OF LAKE HURON WILL MOST LIKELY SEE WINDS INCREASE INTO THE 15 TO 20 KNOT RANGE. OTHERWISE...WINDS WILL REMAIN ON THE LIGHT SIDE AS THIS SOUTHWEST PRESSURE GRADIENT WEAKENS LATE IN THE WEEKEND AS A WEAK LOW PRESSURE SYSTEM LIFTS INTO THE REGION. EVEN THE RETURN OF COLD NORTHWEST FLOW IN THE WAKE OF THE ATTENDING COLD FRONT WILL BE LIMITED TO 25 KNOT GUSTS OR LESS OVER MUCH OF LAKE HURON.
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&& .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON...NONE. LAKE ST CLAIR...NONE. MICHIGAN WATERS OF LAKE ERIE...NONE. && $$ AVIATION.....99 SHORT TERM...CB LONG TERM....DG MARINE.......DG YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).

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