Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 280444
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1144 PM EST THU NOV 27 2014


.AVIATION...

//DISCUSSION...

THE COVERAGE OF CLOUDS AND SNOW SHOWERS/FLURRIES HAS BEEN
DIMINISHING ACROSS SE MI OVER THE LAST SEVERAL HOURS. CONTINUED DRY
AIR ADVECTION WILL FURTHER DECREASE THE CLOUD COVERAGE. WHILE SOME
CLOUDS BASED BELOW 5K FT WILL LINGER INTO DAYBREAK...THE OVERALL
PREVAILING CONDITIONS ARE EXPECTED TO FEATURE SCATTERED CLOUDS AND
INTERVALS OF CLEAR SKIES. THE LOW LEVEL FLOW WILL BACK TOWARD THE
SOUTHWEST LATER FRI MORNING. THE EXPECTATION IS THAT THE AMBIENT DRY
AIR WILL ERODE ANY RESIDUAL LOW STRATUS NEAR LAKE MI PRIOR TO
ARRIVING IN SE MI. AN APPROACHING WARM FRONT WILL PRODUCE A REGION
OF LIGHT SNOW...EXPECTED TO ARRIVE INTO THE TERMINALS LATE FRI
AFTERNOON /20Z TO 23Z TIME FRAME/. SOME MINOR ACCUMULATIONS IS
EXPECTED WITH THIS SNOW.

//DTW THRESHOLD THREATS...

* MEDIUM CONFIDENCE IN CEILINGS BELOW 5000 FEET FRIDAY AFTERNOON AND
  EVENING.

* HIGH CONFIDENCE PRECIP TYPE WILL BE ALL SNOW FRIDAY AFTERNOON AND
  EVENING.

&&

.PREV DISCUSSION...ISSUED 350 PM EST THU NOV 27 2014

SHORT TERM...THIS AFTERNOON AND TONIGHT

TROUGH OF LOW PRESSURE WILL PROGRESS THROUGH THE AREA LATE THIS
AFTERNOON AND EARLY THIS EVENING...BRINGING A GENERAL AREA OF LIGHT
SNOW SHOWERS AND FLURRIES...WHICH WILL END FROM NORTHWEST TO
SOUTHEAST ACROSS THE AREA. ALONG THIS TROUGH...TWO LAKE ENHANCED
VORTICITY CENTERS HAVE LED TO A CONCENTRATED OF MORE MEANINGFUL SNOW
SHOWERS.

OVER LAKE HURON...ONE SUCH FEATURE BRUSHED THE TIP OF THE THUMB
TODAY AND IS NOW PIVOTING EASTWARD ONTO THE CANADIAN SHORELINE THIS
AFTERNOON. WHILE SNOW SHOWER ACTIVITY REMAINS RELATIVELY WELL
ORGANIZED OVER THE FAR EASTERN THUMB...ANY HEAVIER LAKE EFFECT SNOW
SHOWERS HAVE NOW SHIFTED WELL OFFSHORE...AND THIS TREND WILL PERSIST
AS THE OVERALL PROGRESS OF THE TROUGH CONTINUES SOUTHEASTWARD.

EAST OF LAKE MICHIGAN...ANOTHER WELL DEFINED VORTICITY CENTER IS
WELL DEPICTED ON REGIONAL RADAR AND VISIBLE SATELLITE IMAGERY WITH
POCKETS OF MODERATE TO HEAVY SNOW SHOWERS CONTINUING. IT APPEARS THE
CENTER OF THIS FEATURE WILL CROSS THE FAR SOUTHERN CWA LATE THIS
AFTERNOON AND WILL UP SNOW CHANCES THROUGH 00Z AND INCREASE SNOW
ACCUMULATIONS TO ONE HALF TO ONE INCH OR SO AS SOME OF THESE HEAVIER
SNOW SHOWERS CROSS LENAWEE AND POSSIBLY MONROE COUNTIES.

OTHERWISE...ALL OF THIS ACTIVITY SHOULD DIMINISH QUICKLY DURING THE
EVENING HOURS AS THE TROUGH MOVES SOUTHEAST OF THE CWA. SKIES WILL
THEN BEGIN TO CLEAR TONIGHT AS A RIDGE OF HIGH PRESSURE BUILDS
THROUGH THE AREA AS HIGH PRESSURE SETTLES SOUTHEAST FROM THE MID
MISSISSIPPI VALLEY TO TENNESSEE VALLEY. THIS RIDGE WILL ALSO RESULT
IN DIMINISHING WINDS...SO CONDITIONS WILL IMPROVE DRAMATICALLY FOR
RADIATIONAL COOLING AFTER MIDNIGHT. WILL LOWER MINIMUM TEMPERATURES
SEVERAL DEGREES BASED ON THESE EXPECTED TRENDS WITH MOST LOCATIONS
FALLING WELL INTO THE TEENS AND PERHAPS SPORADIC SINGLE DIGITS OVER
THE SAGINAW VALLEY.

LONG TERM...FRIDAY THROUGH WEDNESDAY

THE TROUGH THAT HAS HUNG OVER THE GREAT LAKES THE LAST FEW DAYS WILL
BE WELL TO THE EAST BY FRIDAY MORNING. WITH THIS A MUCH LOWER
AMPLITUDE LONGWAVE PATTERN...NEARLY ZONAL...WILL SET UP ACROSS THE
CONUS THROUGH MUCH OF THE WEEKEND. THIS PATTERN WILL YIELD WEAKER
FLOW OVER THE CONUS WITH STRONGER WAVES TRACKING TO THE NORTH
THROUGH CANADA WHICH WILL ALSO PREVENT ANY NOTABLE STORMS FROM
DEVELOPING AND TRACKING THROUGH THE AREA. WE WILL HOWEVER HAVE
SEVERAL OPPORTUNITIES FOR LIGHT PRECIPITATION AS SOME WEAKER
SYSTEMS/FRONTS ROLL THROUGH. TEMPERATURES WILL BE QUITE VARIABLE
FROM DAY TO DAY AS THE MAIN BAROCLINIC ZONE LIFTS INTO THE AREA AND
HOVERS FOR A WHILE.

FRIDAY CONTINUES TO FEATURE THE BEST CHANCE AT ACCUMULATING
SNOW...ALBEIT ONLY AN INCH OR 2...AS AN ELEVATED WARM FRONT LIFTS
THROUGH LOWER MI. NOT MUCH HAS CHANGED IN THE MODELS IN THE LAST 24
HOURS OUTSIDE OF A SLIGHT JOG NORTH AND A BIT LOWER QPF. OVERALL
MODELS CONTINUE TO INDICATE A WEAK BAND OF FGEN SWEEPING THROUGH
AROUND 00Z SAT. THE FRONT DOES FEATURE A LITTLE BETTER ISENTROPIC
ASCENT THOUGH ALONG THE 290-295K SURFACES. A LAYER OF DRY AIR IN THE
BL CONTINUES TO PLAGUE THE SYSTEM AND THE MEAGER 0.4-0.5 INCH PWATS
WILL STRUGGLE AT FIRST TO SATURATE IT. REGARDLESS THOUGH...MODELS
ARE STILL IN THE BALL PARK OF 0.05-0.1 INCHES OF QPF ACROSS THE
SAGINAW VALLEY AND THUMB...DECREASING TOWARD THE OHIO BORDER. THIS
KEEPS US GENERALLY AROUND AN INCH OF SNOW NORTH OF THE M59
CORRIDOR...WITH THE CHANCE OF UP TO 2 INCHES NORTH OF I69.

A GOOD DEAL OF WAA WILL OCCUR THROUGH THE DAY SATURDAY AND INTO
SUNDAY AS THE SFC WARM FRONT LIFTS THROUGH THE AREA AND STRONG SW
FLOW COMMENCES. LOOKING AT MODEL SOUNDINGS...THE ENTIRE COLUMN UP TO
700MB SHOULD RISE ABOVE 0C BY 00Z SUNDAY...WITH 850MB TEMPS COMING
IN AROUND 10C. THE COLUMN LOSES ALOT OF MID/UPPER LEVEL WHILE
KEEPING THE BL SATURATED ALMOST UP TO ABOUT 850MB TRAPPED UNDER THE
INVERSION. THIS MAY LIKELY RESULT IN AN EXTENDED PERIOD SAT-SUN OF
LIGHT RAIN OR DRIZZLE UNTIL THE COLD FRONT ARRIVES SUNDAY NIGHT.
TEMPERATURES WILL BE THE BIGGER STORY THIS WEEKEND AS SFC TEMPS
APPROACH 50 FOR MOST LOCATIONS ON SUNDAY AND UP TO THE MID 50S
ACROSS THE FAR SOUTH AS 925MB TEMPS CLIMB TO AROUND 7C.

A STRONG SFC HIGH WILL THEN BUILD INTO THE AREA FOR NEXT WEEK. BOTH
ECMWF AND GFS ADVERTISE THE HIGH TO BE AT 1044MB AS IS DRIFTS FROM
THE MIDWEST INTO THE GREAT LAKES. THE BAROCLINIC ZONE WILL SET UP
ACROSS THE NORTHERN OHIO VALLEY THUS ANY FLUCTUATIONS WILL LEAD TO
NOTABLE TEMPERATURE SWINGS.

MARINE...

NORTHWEST FLOW BEHIND AN ARCTIC COLD FRONT IS USHER A COLDER AND
MORE UNSTABLE AIRMASS INTO THE AREA. WINDS ACROSS THE REGION WILL
RAMP UP FOR A FEW HOURS WITH THE ONSET OF THE COLD AIR PUSH BUT WILL
NOT STAY ELEVATED TOO LONG. THIS HAS LEAD TO A MARGINAL GALE EVENT
ACROSS CENTRAL LAKE HURON AS TIGHT PRESSURE GRADIENT AND COLD AIR
ALOFT HAS RESULTED IN WINDS GUSTING TO LOW END GALE FORCE. A GALE
WARNING CONTINUES FOR THE OPEN WATERS OF LAKE HURON FROM PRESQUE
ISLE LIGHT TO STURGEON POINT INTO EARLY THIS EVENING. WE CANNOT RULE
OUT A RANDOM GUST TO 35 KNOTS OUTSIDE OF THE WARNING...BUT THIS
WOULD ONLY OCCUR OVER SHORT TIMEFRAME THUS THE WARNING WILL NOT BE
EXPANDED. THE NORTHWEST FLOW GUSTING TO 25 TO 30 KNOTS HAS LEAD TO
ELEVATED WAVE HEIGHTS ACROSS SOUTHERN LAKE HURON CLIPPING THE
NEARSHORE ZONES AROUND THE THUMB THUS THE SMALL CRAFT ADVISORIES
WILL CONTINUE THROUGH FRIDAY MORNING. A WARM FRONT WILL THEN LIFT
INTO THE REGION FRIDAY WHICH WILL FLIP THE WINDS TO THE
SOUTHWEST/SOUTH BY FRIDAY EVENING. WIND GUSTS OF 25 TO 30 KNOTS
EXPECTED OVER MUCH OF LAKE HURON BEFORE WARMER AND MORE STABLE AIR
WORKS INTO THE REGION.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...SMALL CRAFT ADVISORY UNTIL 7 AM EST FRIDAY FOR LHZ421-441.

LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
&&

$$

AVIATION.....SC
SHORT TERM...DG
LONG TERM....DRK
MARINE.......DRK


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