FXUS63 KDTX 031740
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1240 PM EST THU DEC 3 2009
.AVIATION...
PRECIP HAS TAPERED OFF EARLY THIS AFTERNOON AS LOW PRESSURE
EXISTS TO THE NORTHEAST LEAVING MAINLY MVFR CONDITIONS. TIGHT
PRESSURE GRADIENT BETWEEN THIS LOW AND HIGH PRESSURE TO THE WEST
WILL CONTINUE TO BRING SOMEWHAT GUSTY WINDS TO THE AREA. MAIN
FORECAST CONCERN WILL BE THE CHANCE FOR LAKE EFFECT SNOW LATE
TONIGHT AS COLD AIR MOVES OVER THE WARM WATERS OF LAKE MICHIGAN
AND INTO OUR REGION. BEST CHANCES FOR SNOW WILL BE ACROSS THE
NORTHERN TAF SITES. VISIBILITIES MAY BRIEFLY DROP BELOW IFR
DEPENDING ON WHERE EXACTLY THE BANDS SET UP.
&&
.PREV DISCUSSION...ISSUED 322 AM EST THU DEC 3 2009
SHORT TERM...TODAY
SURFACE LOW RAPIDLY LIFTING NORTHEAST EARLY THIS MORNING WITH THE
LATEST ANALYSIS PLACING IT OVER CENTRAL LAKE ERIE. WIDESPREAD AREA
OF PRECIPITATION CONTINUING TO SHIFT ACROSS SOUTHEAST LOWER MI
SUPPORTED BY GOOD MID LEVEL DEFORMATION. BOUNDARY LAYER REMAINING
WARM ENOUGH /SFC TEMPS UPPER 30S-LOWER 40S/ TO ENSURE THIS FALLS IN
ONLY THE LIQUID FORM...WITH THE RAIN/SNOW LINE STILL WELL WEST IN
THE VICINITY OF LAKE MICHIGAN.
STRONGEST FORCING AND PRIMARY MOISTURE AXIS WILL EXIT THE REGION
BETWEEN 11-14Z THIS MORNING...RESULTING IN A RAPID REDUCTION IN
PRECIPITATION COVERAGE/INTENSITY DURING THIS TIME. THERMAL PROFILE
WILL SEE ONLY MINOR COOLING THIS MORNING WITH THE BETTER COLD AIR
ADVECTION ARRIVING THROUGH THE AFTERNOON. THIS WILL CONTINUE TO
SUPPORT MAINLY RAIN GIVEN FREEZING LEVELS STILL ABOVE 2K FT...WITH
PERHAPS A FEW WET SNOWFLAKES MIXING IN ACROSS THE NORTH RIGHT AS ANY
LINGERING PRECIPITATION CONTAINED ALONG A WEAK CONVERGENCE ZONE ENDS
BY 18Z. LITTLE ADDITIONAL SUPPORT EXISTS TO MAINTAIN CHANCE POPS
FOR MID-LATE AFTERNOON WITH A BACKING LOW LEVEL WIND FIELD FROM
NORTH TO WEST BRIEFLY DISRUPTING ANY POTENTIAL ADDED MOISTURE FLUX
OFF THE LAKES.
TEMPERATURES TODAY WILL RECOVER LITTLE FROM THE MORNING LOWS GIVEN
THE DEGREE OF COOLING ANTICIPATED OVER THE COURSE OF THE DAY.
READINGS WILL GENERALLY HOVER IN 36-42F RANGE THIS MORNING...
FALLING INTO THE LOW-MID 30S BY LATE AFTERNOON AS THE ADVECTIVE
PROCESS STRENGTHENS.
LONG TERM...
ARCTIC AIR IS SPILLING INTO THE CENTRAL CONUS AS HIGHLY AMPLIFIED
LONGWAVE TROUGH EXTENDS TO MEXICO/WESTERN GULF OF MEXICO.
HAVE NOTED SEVERAL LOW MAXIMUM RECORDS ACROSS WYOMING/MONTANA
YESTERDAY...AS NORTHERLY FLOW ORIGINATES STRAIGHT FROM THE ARCTIC.
THIS VERY COLD AIR WILL SETTLE OVER LOWER MICHIGAN
FRIDAY-SATURDAY...SENDING THE STATE INTO A DEEP FREEZE.
POTENT UPPER WAVE/LOW TRACKING SOUTHEAST THROUGH EASTERN SOUTH
DAKOTA IS EXPECTED TO TRACK THROUGH SOUTHERN LAKE MICHIGAN TONIGHT
AND THROUGH NORTHERN LOWER MICHIGAN TOMORROW MORNING...SHEARING OUT
IN THE PROCESS HOWEVER. LOW STATIC STABILITY IN THE LOW LEVELS
(NEGATIVE EPV)...WITH MAX LIFT IN OR CLOSE TO THE DENDRITIC SNOW
GROWTH REGION TONIGHT SUPPORTS A GOOD BURST OF LAKE ENHANCED BAND(S)
OF SNOW SHOWERS TONIGHT....AS SATURATION EXTENDS TO 700 MB. THE ONE
SAVING GRACE IS THE LOW LEVEL CONVERGENCE LOOKS TO BE TRANSIENT
(ADVANCING NORTH THROUGH THE NIGHT)...STARTING OUT AROUND I-94 AND
THEN REACHING AND LIFTING NORTH OF I-69 CORRIDOR BY MORNING. FOR
THIS REASON...LOOKING FOR ACCUMULATIONS IN THE HALF AN INCH TO 2
INCH RANGE.
WITH A LITTLE MORE CONFIDENCE THERE WILL BE A BIT OF A SNOW COVER
FOR MANY LOCATIONS...LOOKING AT MAXES STRUGGLING TO REACH THE
FREEZING MARK FRIDAY-SATURDAY AS THE COLD AIRMASS (-12 TO -14 C 850
MB TEMPS) SWINGS THROUGH. NOTHING REALLY STANDS OUT FRIDAY
AFTERNOON-SATURDAY IN TERMS OF LAKE BANDS OR ORGANIZED LIFT WITHIN
THE WEST-SOUTHWEST FLOW...AS SURFACE HIGH OVER THE OHIO VALLEY TRIES
TO BUILD IN. NONE-THE-LESS...WITH SUCH A COLD AIRMASS (EXCELLENT
DELTA TS) WOULD EXPECTED AT LEAST FLURRIES OR SCATTERED LIGHT SNOW
SHOWERS TO MAKE INTO THIS SIDE OF THE STATE. WITH RIDGING BUILDING
IN AT ALL LEVELS SATURDAY NIGHT...INCREASED CONFIDENCE SKIES WILL
BECOME PARTLY CLOUDY/MOSTLY CLEAR...ALLOWING MINS TO DROP INTO THE
MID/UPPER TEENS WITH THE CALM WINDS.
DECENT LOW LEVEL WARM ADVECTION WILL BE PRESENT ON SUNDAY AHEAD OF A
MOISTURE STARVED AND WEAK COLD FRONT...WHICH WILL PROBABLY WASH OUT
WITH THE WESTERLY CONFLUENT UPPER LEVEL FLOW ADVERTISED BY THE EURO.
MAXES SHOULD REBOUND INTO THE MID TO POSSIBLY UPPER 30S.
MARINE...
NORTHEAST WINDS WILL BACK TOWARD THE NORTHWEST WHILE REMAINING GUSTY
TODAY AS A LOW PRESSURE SYSTEM LIFTS TOWARD NEW ENGLAND. STRONGEST
WINDS WILL OCCUR THIS MORNING WITH GUSTS REACHING 30 KNOTS AT
TIMES. THIS ALONG WITH THE ONSHORE WIND DIRECTION WILL CREATE WAVE
CONDITIONS BUILDING UP TO 10 FEET ON THE NEARSHORE WATERS OF LAKE
HURON. THE POTENTIAL EXISTS FOR GUSTS TO BRIEFLY REACH GALE FORCE ON
SOUTHERN LAKE HURON THIS MORNING BUT THE LIMITED DURATION WILL
PRECLUDE THE NEED FOR A GALE WARNING.
SLACKENING PRESSURE GRADIENT WILL ALLOW GUSTS TO BRIEFLY DIMINISH
TONIGHT WITH A CORRESPONDING DROP IN WAVE HEIGHT. SOUTHWEST WINDS
WILL THEN STRENGTHEN AGAIN ON FRIDAY. THIS COMBINED WITH COLD AIR
MOVING OVER THE WARMER WATERS WILL LEAD TO UNSTABLE CONDITIONS ONCE
AGAIN. ADDITIONAL SMALL CRAFT ADVISORIES WILL LIKELY BE NEEDED
DURING THIS TIME.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...
SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT
HURON INCLUDING OUTER SAGINAW BAY...UNTIL 10 PM THURSDAY.
SMALL CRAFT ADVISORY...INNER SAGINAW BAY...UNTIL 4 PM THURSDAY.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
AVIATION.....AGD
SHORT TERM...MR
LONG TERM....SF
MARINE.......MR
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AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
