Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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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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