Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 200803 CCA
AFDDTX

AREA FORECAST DISCUSSION...CORRECTED TYPO
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
300 AM EST SAT DEC 20 2014

.SHORT TERM...TODAY AND TONIGHT

IMPRESSIVE UPPER LEVEL RIDGE OVER QUEBEC WITH BIT MORE CHAOTIC
PATTERN OVER CENTRAL NORTH AMERICA...WITH AT LEAST THREE DISTINCT
UPPER WAVES SEEN ON THE LATEST WATER VAPOR IMAGERY. THESE
FEATURES HAVE LITTLE MOISTURE TO WORK WITH...AND ARE MOSTLY
RESULTING IN JUST MID/HIGH CLOUDS. MAJORITY OF UPPER LEVEL PV WILL
BE TRACKING SOUTH OF MICHIGAN BORDER TODAY/TONIGHT. MAIN IMPACT
WILL BE MODEST MOISTURE ADVECTION THROUGH TONIGHT...WITH THE VERY
LIGHT WIND FIELD SHIFTING TO THE SOUTHWEST. THIS IS EXPECTED TO
ALLOW THE LOW CLOUDS (2-3 KFT) CURRENTLY ALONG THE I-94 CORRIDOR
TO CREEP NORTH THROUGH THE DAY INTO TONIGHT. EVEN IF LOW CLOUDS
FAIL TO MAKE MUCH PROGRESS PAST THE M-59 CORRIDOR...HIGH CLOUDS
WILL BE PLENTIFUL...ASSURING MOSTLY CLOUD SKIES FOR MAJORITY OF
THE CWA. DUE TO THE INCREASING CLOUDS AND WITH THE CURRENT
TEMPERATURES IN THE MID TEENS TO AROUND 20 DEGREES ACROSS THE
NORTHERN TWO THIRDS OF THE CWA THIS MORNING...WOULD EXPECT MAX
TEMPS TO STRUGGLE TO REACH THE FREEZING MARK. CLOUDS AND MODEST
MOISTURE ADVECTION (SURFACE DEW PTS RISING INTO THE LOW/MID 20S)
TONIGHT SHOULD LEAD TO SMALL DIURNAL SWING...HOLDING TEMPS/MINS
IN THE MID 20S.

&&

.LONG TERM...SUNDAY THROUGH NEXT FRIDAY

THE QUIET WEATHER PATTERN CONTINUES INTO SUNDAY AS HIGH PRESSURE
BEGINS TO BUILD OFF TO THE EAST OF THE REGION. WITH THE BEGINNING OF
RETURN SOUTHERLY FLOW ON THE BACKSIDE OF THIS HIGH...TEMPERATURES
WILL REBOUND INTO THE MID 30S EVEN UNDER MOSTLY CLOUDY SKIES AS MID
TO UPPER LEVEL MOISTURE STREAMS INTO THE CENTRAL GREAT LAKES WITHIN
SOUTHWEST FLOW REGIME DEVELOPING IN ADVANCE OF DEVELOPING STORM
SYSTEM OVER THE NORTHERN/CENTRAL PLAINS.

THE STREAM OF MOISTURE IN ADVANCE OF THIS DEVELOPING UPPER
TROUGH/LOW WILL CONTINUE INTO EARLY NEXT WEEK WITH PRECIPITATION
CHANCES INCREASING STEADILY FROM MONDAY INTO TUESDAY. ALL OF THIS
PRECIPITATION SHOULD FALL AS RAIN SHOWERS AS THE STEADY STREAM OF
MILD AND MOIST AIR QUICKLY REPLACES ANY REMAINING COLD AIR THAT IS
POSITIONED OVER THE AREA EARLY MONDAY.

THE FORECAST REMAINS QUITE DIFFICULT HEADING INTO THE MIDDLE OF NEXT
WEEK AS MEDIUM RANGE MODEL RUNS VARY ON BOTH THE WEST/EAST POSITION
OF THIS AFOREMENTIONED UPPER TROUGH WITHIN THE NORTHERN STREAM AND
ALSO WITH THE DEGREE OF SHORTWAVE ENERGY THAT WILL WRAP INTO THIS
TROUGH FROM THE SOUTHERN STREAM. TRENDS SINCE 00Z YESTERDAY HAVE
MOST DEFINITELY SHIFTED WESTWARD WITH THE TRACK OF ANY STORM DURING
THIS TIME FRAME...WITH THE EVENTUAL LOW PRESSURE CENTER NOW TRACKING
NORTHWARD OVER OR WEST OF THE AREA. IN FACT...GFS/GEM TRACK A
RAPIDLY DEEPENING LOW PRESSURE SYSTEM STRAIGHT NORTH INTO LOWER
MICHIGAN WITH ECMWF TAKING A SIMILAR DEEP LOW PRESSURE ALONG THE
EASTERN EDGE OF THE CWA INTO LAKE HURON IN THE WEDNESDAY/WEDNESDAY
NIGHT TIME FRAME. IT SHOULD ALSO BE NOTED THAT A MAJORITY OF GFS
ENSEMBLE MEMBERS FOCUS PRIMARILY ON THE PIVOT POINT LOW PRESSURE
WELL TO THE NORTHWEST UNDER THE NORTHERN STREAM UPPER LOW PRESSURE
WITH ONLY MINOR/MODEST DEVELOPMENT OF THE SECONDARY LOW FROM THE
SOUTHERN STREAM SYSTEM.

ALL IN ALL...THIS STEADY TREND WESTWARD SUGGESTS A BETTER CHANCE AT
RAIN WELL INTO WEDNESDAY BEFORE THE SYSTEM LIFTS NORTH OF THE AREA
AND COLD AIR WRAPS INTO LOWER MICHIGAN FROM THE SOUTH/SOUTHWEST AND
CHANGES ANY WRAPAROUND DEFORMATION PRECIPITATION TO SNOW WITH TIME
WEDNESDAY EVENING/OVERNIGHT. WILL MAKE SHIFTS IN BOTH THE PRECIP
TYPE AND TEMPERATURE FORECASTS INTO WEDNESDAY WITH A TRANSITION TO
SNOW WEDNESDAY NIGHT. EVEN WITH THE UNCERTAINTY IN PRECIPITATION
TYPE/TRANSITION...IT IS BECOMING INCREASINGLY LIKELY THAT THE TRACK
AND STRENGTH OF THIS SYSTEM WILL BE CONDUCIVE TO RATHER STRONG WINDS
AS IT PASSES BY/THROUGH AND THEN NORTH OF THE REGION.

&&

.MARINE...

SURFACE HIGH PRESSURE WILL REMAIN OVER THE AREA THROUGH MUCH OF THE
WEEKEND...PROVIDING GENERALLY CALM CONDITIONS. THIS HIGH WILL THEN
TRACK INTO THE EASTERN GREAT LAKES BY SUNDAY NIGHT WITH SOUTHERLY
WINDS INCREASE SOMEWHAT SUNDAY NIGHT INTO MONDAY AS A WEAK MID-LEVEL
TROUGH THEN TRACKS THROUGH THE NORTHERN GREAT LAKES. IN ADDITION TO
INCREASED WINDS...THE TROUGH AS THE POTENTIAL TO BRING SOME LIGHT
SNOW SHOWERS TO NORTHERN LAKE HURON BY SUNDAY NIGHT. ACTIVE WEATHER
WILL RETURN TO THE GREAT LAKES FOR MOST OF NEXT WEEK AS A LARGE
STORM SYSTEM DEVELOPS TO THE WEST AND EVENTUALLY SHIFTS INTO THE
AREA. WHILE UNCERTAINTY IN THE DETAILS OF THIS STORM REMAIN RATHER
HIGH...EXPECT PRECIPITATION CHANCES TO INCREASE SUBSTANTIALLY FROM
EARLY TO MID WEEK WITH STRONG WINDS POSSIBLE BY MID WEEK AS LOW
PRESSURE LIFTS THROUGH THE REGION.

&&

.AVIATION...ISSUED 1159 PM EST FRI DEC 19 2014

//DISCUSSION...

VERY LIGHT NORTHWEST/NORTH WINDS HAVE ALLOWED LOW CLOUDS TO SLIP
JUST SOUTH OF THE SOUTHERN TAF SITES. HIGH CLOUDS STREAMING INTO THE
LOWER MICHIGAN THIS MORNING WILL COMPLICATE THE RETURN OF THE MVFR
CLOUDS...AND CONFIDENCE IN THE TIMING OF THE RETURN OF THE LOW
CLOUDS IS LOW...ESPECIALLY ACROSS NORTHERN TAF SITES...MBS/FNT/PTK.
VERY LIGHT DEVELOPING SOUTHWEST WINDS WILL SPREAD MODEST MOISTURE
BACK INTO SOUTHEAST MICHIGAN TODAY....WITH LOW CLOUDS CREEPING
NORTH DURING THE DAYTIME HOURS. THIS TREND SHOULD CONTINUE THIS
EVENING AND TONIGHT...BUT STILL NOT SURE IF THE LOW CLOUDS WILL
MAKE IT TO MBS.

FOR DTW...CONFIDENCE IN THE TIMING OF THE RETURN OF MVFR CEILINGS IS
LOW AS THEY REMAIN RIGHT AT THE DOORSTEP...BUT ONCE LOW CLOUDS DO
ARRIVE...THEY SHOULD REMAIN LOCKED IN THROUGH THE TAF PERIOD.

//DTW THRESHOLD THREATS...

* MEDIUM CONFIDENCE IN CEILINGS BELOW 5000 FEET THIS MORNING...HIGH
  CONFIDENCE THIS AFTERNOON THROUGH TONIGHT.

&&

.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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