Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000 FXUS63 KDTX 210805 AFDDTX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI 305 AM EST SUN DEC 21 2014 .SHORT TERM...TODAY AND TONIGHT A WEDGE OF DRY AIR/CLEARING WORKED THROUGH SOUTHEAST MICHIGAN DURING THE LATE EVENING/EARLY MORNING HOURS...ALLOWING TEMPERATURES TO DIP INTO THE MID TEENS TO LOWER 20S ACROSS MOST LOCATIONS. ANOTHER BATCH OF LOW LEVEL MOISTURE AND CLOUDS ARE WORKING INTO THE CWA AT PRESS TIME...AND TEMPERATURES HAVE QUICKLY WARMED/REBOUNDED INTO THE MID TO UPPER 20S UNDERNEATH THESE CLOUDS. THIS MOISTURE/CLOUDS IS DOWNSTREAM OF THE WARM FRONT OVER THE MIDWEST...WHICH WILL BE LIFTING NORTH THROUGH THE WESTERN GREAT LAKES TODAY AND TONIGHT...AS 500 MB HEIGHT/SHORTWAVE RIDGING BUILDS OVER THE CENTRAL GREAT LAKES. THE LOW LEVEL FLOW OVER SOUTHEAST MICHIGAN WILL BE BACKING TO THE SOUTHEAST BY THE END OF THE DAY IN RESPONSE OF THE WARM FRONT LIFTING NORTH...AND THIS WILL ALLOW DRIER AIR TO STREAM IN FROM SOUTH TO NORTH TODAY INTO EARLY THIS EVENING...SCOURING OUT THE LOW CLOUDS. EVEN SO...PLENTY OF MID/HIGH CLOUDS WILL BE STREAMING BY...SUPPORTING CONSIDERABLE CLOUDS INTO TONIGHT. THESE HIGHER CLOUDS AND JUST ENOUGH OF THE SURFACE WINDS STAYING UP TONIGHT IS EXPECTED TO LIMIT FOG POTENTIAL. GUIDANCE TEMPS SEEM REASONABLE TODAY/TONIGHT...MAXES IN THE MID 30S...WITH MINS IN THE 20S TONIGHT. && .LONG TERM...MONDAY THROUGH SATURDAY MODERATING TEMPERATURES CAN BE EXPECTED EARLY IN THE EXTENDED FORECAST AS A WARM FRONT LIFTS NORTH THROUGH THE AREA IN RESPONSE TO DEVELOPING LOW PRESSURE OVER THE CENTRAL PLAINS/MID MISSISSIPPI VALLEY. TEMPERATURES WILL CLIMB TO AROUND 40 MONDAY AND WELL INTO THE 40S TO AROUND 50 TUESDAY AND WEDNESDAY. WITH THIS PUSH OF MILD/INCREASINGLY MOIST AIR INTO THE AREA...THE CHANCE OF PRECIPITATION...ALL RAIN...WILL ALSO INCREASE STEADILY FROM MONDAY EVENING INTO TUESDAY/TUESDAY NIGHT AS AN INITIAL LOW PRESSURE SHIFTS FROM THE THE PLAINS INTO THE MISSISSIPPI VALLEY AND EVENTUALLY THE WESTERN/NORTHERN GREAT LAKES. MUCH UNCERTAINTY REMAINS IN THE DEVELOPMENT OF A SECOND LOW PRESSURE SYSTEM AS JET ENERGY DIGS AROUND AMPLIFYING UPPER THROUGH AND LOW PRESSURE LIFTS NORTHWARD INTO THE GENERAL AREA. GUIDANCE HAS BEEN ALL OVER THE PLACE THE PAST FEW DAYS...AND THE 00Z RUNS ARE NO EXCEPTION. WHILE A NUMBER OF SOLUTIONS STILL BRING A RATHER STRONG LOW PRESSURE SYSTEM THROUGH THE AREA ON WEDNESDAY...TRENDS HAVE BEEN TOWARDS A WEAKER LOW PRESSURE WITHIN THE CONUS WITH BETTER PHASING ONCE THIS SOUTHERN ENERGY REACHES EASTERN CANADA. CONFIDENCE IS PRETTY HIGH THAT THIS ENERGY WILL REMAIN WEST OF THE APPALACHIANS SO HIGH PRECIPITATION CHANCES LOOK GOOD IN THE FORECAST AS THIS SYSTEM LIFTS INTO THE NORTHEAST CONUS/GREAT LAKES WEDNESDAY. THERE IS ALSO A DECIDED LACK OF COLD AIR IN PLACE WITH THE NORTHERN UPPER TROUGH...SO ANY CHANGEOVER FROM RAIN TO SNOW SHOULD BE SOMEWHAT SLOW AND HOLD OFF UNTIL COLD AIR IS ABLE TO WRAP INTO LOWER MICHIGAN AROUND THE LOW...MOST LIKELY IN THE WEDNESDAY NIGHT TIME FRAME. THIS IS ACTUALLY PRETTY WELL IN LINE WITH THE GOING FORECAST IN TIMING THE TRANSITION TO SNOW. WILL JUST DELAY THIS 6-12 HOURS TO THE OVERNIGHT HOURS WEDNESDAY NIGHT. WITH THE LOW PRESSURE BEING WEAKER...ON AVERAGE...WIND SPEED FORECASTS HAVE COME DOWN NOTABLY AS WELL. COLDER AIR DOES FILTER INTO THE AREA FOR THE REMAINDER OF THE FORECAST...BUT GIVEN A LIMITED CONNECTION TO THE POLAR/ARCTIC AIRMASS WELL NORTHWEST OF THE AREA...TEMPERATURES WILL REMAIN AOA AVERAGE IN THE 30S. A SHORTWAVE TROUGH...AND ASSOCIATED LOW PRESSURE...RACE THROUGH THE GREAT LAKES IN THE FRIDAY TIME FRAME AND ONLY AFTER THIS SYSTEM PASSES DOES ANY NOTABLE COLD AIR GET DRAWN INTO THE REGION. && .MARINE... LIGHT WINDS WILL GIVE TO GRADUALLY INCREASING SOUTH TO SOUTHEAST FLOW LATER TODAY INTO MONDAY WITH A MORE PRONOUNCED INCREASE LATE MONDAY NIGHT INTO EARLY TUESDAY AS THE PRESSURE GRADIENT TIGHTENS IN RESPONSE TO LOW PRESSURE LIFTS INTO THE WESTERN AND NORTHERN GREAT LAKES. WITH THE APPROACH OF THIS LOW MUCH CLOSER THAN PREVIOUS FORECASTS...HAD TO INCREASE WINDS SLIGHTLY. WHILE HEADLINES ARE NOT OUT OF THE QUESTION DURING THIS TIME FRAME...LATE MONDAY NIGHT INTO MIDDAY TUESDAY...THE WARM AIR BEING PULLED NORTH WITHIN THIS FLOW WILL LIMIT WIND GUSTS TO THE SURFACE AS A STABLE LAYER DEVELOPS OVER THE RELATIVELY COLD GREAT LAKES WATER/BOUNDARY LAYER. SECONDARY SURFACE LOW DEVELOPMENT IS STILL FORECAST BY WEDNESDAY AS LOW PRESSURE DEVELOPS OVER THE LOWER MISSISSIPPI VALLEY AND TRACKS NORTH TO NORTHEAST INTO THE OHIO VALLEY AND CENTRAL TO EASTERN GREAT LAKES. WHILE TRENDS SUGGEST THIS SYSTEM MAY NOT A QUITE AS STRONG A PREVIOUSLY ANTICIPATED...IT STILL HAS THE POTENTIAL TO PRODUCE GALES WEDNESDAY NIGHT INTO THURSDAY...DEPENDING...OF COURSE...ON THE TRACK AND EVENTUAL STRENGTH OF THE SYSTEM. && .AVIATION...ISSUED 1148 PM EST SAT DEC 20 2014 //DISCUSSION... A WEDGE OF DRIER AIR HAS MOVED INTO THE MAJORITY OF SOUTHEAST MICHIGAN LATE THIS EVENING...BUT ANOTHER BATCH OF LOW LEVEL MOISTURE AND CLOUDS (2000-5000 FEET) OVER SOUTHWEST LOWER MICHIGAN MOVING INTO THE AREA EARLY THIS MORNING...PERSISTING OVER THE NORTHERN TAF SITES FOR MOST OF THE DAY. THE OVERALL TREND OF THE FORECAST PERIOD WILL BE FOR DRIER AIR IN THE LOW LEVELS TO TAKE HOLD AS SURFACE WINDS BACK AROUND TO THE SOUTHEAST BY EARLY THIS EVENING...ALLOWING SKIES TO SCT-CLEAR OUT FROM SOUTH TO NORTH. FOR DTW...LATEST TRENDS SHOW THE CEILING NEAR 3KFT STRUGGLING TO CLEAR DETROIT METRO...WITH NEXT BATCH OF MOISTURE ARRIVING IN NEXT COUPLE HOURS...ASSURING CEILINGS BELOW 5000 FEET DURING THE MORNING HOURS. DRIER AIR IN THE LOW LEVELS SHOULD EVENTUALLY SCATTER OUT OR CLEAR THE SKIES OUT BY EARLY EVENING...AS WINDS SHIFT TO THE SOUTHEAST. COULD BE A TOUCH OF LIGHT FOG TONIGHT...BUT IT IS POSSIBLE WINDS STAY UP ENOUGH TO PREVENT THIS FROM HAPPENING. //DTW THRESHOLD THREATS... * HIGH CONFIDENCE IN CEILINGS BELOW 5000 FEET THIS MORNING...LOWER CONFIDENCE THIS AFTERNOON. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON...NONE. LAKE ST CLAIR...NONE. MICHIGAN WATERS OF LAKE ERIE...NONE. && $$ SHORT TERM...SF LONG TERM....DG MARINE.......DG AVIATION.....SF YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).

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