FXUS63 KDTX 261611
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1110 AM EST SAT DEC 26 2009
.AVIATION...
UPPER LEVEL CLOSED LOW OVER WISCONSIN WILL SLOWLY MOVE EAST TO OVER
SOUTHEAST LOWER MICHIGAN BY 00Z MON. ASSOCIATED SURFACE LOW WILL
TRACK NORTHEAST. MOST LIGHT SNOW SHOWER ACTIVITY WILL STAY TO THE
WEST OF THE TAF SITES THIS AFTERNOON CLOSER TO THE UPPER SUPPORT. A
BAND OF SNOW SHOWERS WITH MVFR CIGS AND VISIBILITIES ASSOCIATED WITH
A SURFACE TROUGH WILL ROLL THROUGH BETWEEN 03Z AND 09Z. ANOTHER
BAND OF SNOW SHOWERS WILL AFFECT DTW AFTER 21Z SUNDAY ASSOCIATED
WITH THE UPPER LOW. THERE IS A CHANCE OF FLURRIES AT ANY TIME AT
ALL TAF SITES BUT JUST MENTION THE BEST CHANCE FOR ANY SIGNIFICANT
SNOW IN TAFS.
&&
.PREV DISCUSSION...ISSUED 317 AM EST SAT DEC 26 2009
SHORT TERM...TODAY
OCCLUDED FRONT HAS LIFTED NORTH OF THE AREA AND TAKEN THE STEADIER
RAINFALL WITH IT. WITH CAA...PRECIPITATION TYPE WILL CHANGE QUICKLY
OVER TO SNOW EARLY THIS MORNING...AND EXPECT SCATTERED LIGHT SNOW
SHOWERS AS ONE OF THE MAJOR VORTICITY CENTERS EMBEDDED WITHIN THE
LARGE UPPER LOW TO WEST PIVOTS INTO THE WESTERN AND CENTRAL GREAT
LAKES. THIS ACTIVITY WILL BE RATHER LIGHT WITH LESS THAN AN INCH OF
ACCUMULATION EXPECTED. ONCE THIS VORT LOBE SHIFTS NORTH THROUGH LAKE
MICHIGAN...SNOW SHOWERS WILL TAPER OFF BY MIDDAY AS THE UPPER LOW
REMAINS TO THE WEST THROUGH THE DAY. TEMPERATURES WILL BE COOLER
TODAY WITH HIGHS NEAR 30. WITH THE COLD AIR JUST NOW OVERSPREADING
THE REGION...THIS ESSENTIALLY MEANS RELATIVELY STEADY TEMPERATURES
INTO THE AFTERNOON.
LONG TERM...
SEASONABLY COLD WEATHER WITH A FEW SNOW SHOWERS CAN BE EXPECTED
DURING THE NEXT COUPLE OF DAYS.
700-500 MB LOWS/MID LEVEL CIRCULATION REMAINS ON TRACK TO SWING
THROUGH SOUTHERN LOWER MICHIGAN ON SUNDAY...LEADING TO STEEP LOW
LEVEL LAPSE RATES/INSTABILITY...WORTHY OF GENERATING AT LEAST
SCATTERED SNOW SHOWERS. LOW LEVEL WINDS VEERING AROUND TO A MORE
WESTERLY DIRECTION OFF LAKE MICHIGAN SHOULD ALSO PROVIDE AN ADDED
BONUS.
MEANWHILE...POLAR VORTEX WILL SINK SOUTHEAST AND BECOME ENTRENCHED
NEAR SOUTHAMPTON ISLAND IN CANADA ON SUNDAY...WITH AN UPPER
WAVE/TROUGH EXTENSION SWINGING THROUGH THE EASTERN GREAT LAKES LATE
MONDAY. LOW LEVEL CONVERGENCE/LOW STATIC STABILITY WITH AN ARCTIC
FRONT SWINGING SOUTH THROUGH LOWER MICHIGAN DURING MONDAY APPEARS
FAVORABLE TO GENERATE ANOTHER ROUND OF AT LEAST SCATTERED SNOW
SHOWERS. LIGHT SNOW ACCUMULATIONS ARE POSSIBLE BOTH DAYS. 925 MB
TEMPS PROGGED TO FALL TO -12 C OR SLIGHTLY COLDER BY TUESDAY
MORNING...SETTING UP A COLD NIGHT MONDAY NIGHT (LOW/MID TEENS) WITH
THE POTENTIAL FOR MINS TO FALL INTO THE SINGLE NUMBERS IF WINDS ARE
ABLE TO DECOUPLE BY MORNING. THE AIRMASS WILL HAVE A HARD TIME
RECOVERING ON TUESDAY WITH SURFACE HIGH/RIDGE IN PLACE (MAXES MOSTLY
IN THE MIDDLE 20S). GENERAL SUBSIDENCE/NORTHWEST CONFLUENT FLOW
SHOULD ASSURE A DRY DAY...BUT A FLURRY IS ALWAYS A CONCERN WITH
NORTHWEST FLOW AND POSSIBLY JUST ENOUGH 925 MB MOISTURE.
UPPER LEVEL RIDGE AXIS IS THEN FORECASTED TO SWING THROUGH THE
CENTRAL GREAT LAKES TUESDAY NIGHT/WEDNESDAY MORNING...WITH
PREDOMINATELY SPLIT FLOW ADVERTISED OVER THE CONUS...TRENDING TOWARD
MORE AMPLIFIED/PHASED SCENARIO TOWARD THE END OF THE WORK WEEK. AT
THIS POINT...IT APPEARS THE NORTHERN STREAM WILL DOMINATE OUR
WEATHER...WITH MERGING/PHASING OCCURRING JUST A BIT TOO LATE FOR US
TO EXPECT A BIG SNOWSTORM...BUT A LIGHT ROUND OF SNOW WEDNESDAY
NIGHT-THURSDAY APPEARS POSSIBLE AHEAD OF A SHORTWAVE TROUGH/SURFACE
COLD FRONT.
MARINE...
OCCLUDED FRONT WILL SHIFT THROUGH THE REMAINDER OF LAKE HURON DURING
THE MORNING...BRINGING AS GRADUAL END TO THE STRONG EASTERLY FLOW AS
WINDS TURN TO THE SOUTH/SOUTHWEST AND DECREASE SOMEWHAT. WILL EXPIRE
THE CURRENT HEADLINES ON TIME AS GUSTS OVER NORTHERN LAKE HURON ARE
ONLY AROUND 30 KNOTS ATTM ANYWAY...AND NEARSHORE CONDITIONS WILL BE
IMPROVING STEADILY WITH OFFSHORE FLOW OF 10-20 KNOTS. ANY REMAINING
MIX OF RAIN/SNOW WILL BECOME LIGHT SNOW SHOWERS DURING THE DAY AS
CAA CONTINUES.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
AVIATION.....DRC
SHORT TERM...DG
LONG TERM....SF
MARINE.......DG
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AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
