FXUS63 KDTX 252354
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
654 PM EST FRI DEC 25 2009
.AVIATION...
SUBSTANTIAL LOW LEVEL MOISTURE WILL REMAIN IN PLACE THROUGH THE TAF
PERIOD ENSURING MVFR CEILINGS HOLD DURING THIS TIME. ANY LINGERING
WILL END SHORTLY WITH THE PASSAGE OF A COLD FRONTAL BOUNDARY. DRIER
MID LEVEL AIR WORKING IN BEHIND THIS FRONT WILL KEEP PRECIPITATION
CHANCES MINIMAL THROUGH THE MORNING HOURS. MOISTURE WILL DEEPEN
AGAIN BY SATURDAY AFTERNOON LEADING TO SCATTERED SNOW SHOWER
DEVELOPMENT. THE DEVELOPING POST-FRONTAL SOUTHERLY WIND FIELD WILL
DIMINISH SLIGHTLY OVERNIGHT WITH THE GUSTINESS SUBSIDING.
&&
.PREV DISCUSSION...ISSUED 331 PM EST FRI DEC 25 2009
SHORT TERM...TONIGHT
HEAVY BAND OF RAINS SHOWERS HAS LIFTED NORTH OF THE CWA THIS
AFTERNOON. NEW SHOWERS HAVE BEEN DEVELOPING BEHIND THIS BOUNDARY
PRODUCING JUST LIGHT RAIN SHOWERS. THIS PATTERN LOOKS TO CONTINUE
INTO THE OVERNIGHT UNTIL A COLD FRONT ASSOCIATED WITH THE LARGE LOW
PRESSURE SYSTEM CENTERED OVER IOWA SWEEPS THROUGH SE MI BETWEEN
02-06Z. THERE IS AN ENHANCED LINE OF SHOWERS THAT WILL ACCOMPANY
THIS SURFACE FRONT THROUGH THE AREA TONIGHT...BUT SHOULD ONLY
PRODUCE AROUND A TENTH OF AN INCH OF PRECIPITATION. THIS VERTICALLY
STACKED LOW PRESSURE SYSTEM APPEARS TO HAVE REACHED ITS PEAK
INTENSITY AND SHOULD WEAKEN AS IT BEGINS ITS PUSH TO THE TONIGHT.
WE WILL BE UNDER A MUCH DIFFERENT AIRMASS ALOFT OVERNIGHT IN THE
WAKE OF THIS COLD FRONT. 850MB TEMPERATURES WILL DROP TO AROUND
-11C...DOWN FROM +6C LAST NIGHT...THOUGH IT WILL TAKE A WHILE FOR
THE SURFACE TO REALIZE THIS WITH THE ABUNDANCE OF CLOUD COVER AND
MOISTURE IN THE LOW LEVELS. OVERNIGHT TEMPS WILL DROP JUST BELOW
FREEZING HOVERING NEAR 30 AT MOST LOCATIONS.
PRECIPITATION WILL BE TRANSITION BACK TO SNOW OVERNIGHT. AS THE
COLUMN COOLS...WE WILL HAVE A FEW HOURS OF RAIN/SNOW MIX BEFORE
CHANGING TO ALL SNOW TOWARD MORNING. ANY ACCUMULATIONS WILL BE
MINIMAL...TOPPING OUT AROUND ONE TO TWO TENTHS OF AN INCH.
LONG TERM...SATURDAY THROUGH NEW YEARS DAY
DESPITE SOUTH WINDS...COLDER TEMPERATURES ARE EXPECTED ON SATURDAY
AS COLDER AIR MOVES INTO SOUTHEASTERN MICHIGAN WITH 850 MB
TEMPERATURES PLUMMETING TO -10 TO -12 CELSIUS. THE COLDER AIR WILL
MEAN PRECIPTIATION TYPE WILL BE ALL SNOW. HOWEVER WITH THE BEST
MOISTURE AND FORCING OFF TO THE EAST WITH THE COLD FRONT AND THE
SURFACE AND UPPER LEVEL FEATURES ACROSS THE WESTERN GREAT LAKES.
WITH LESS FORCING AND DRY AIR AT AND ABOVE 800 MB...POPS LOOK CHANCY
AT BEST ACROSS THE AREA ON SATURDAY.
THE LOW ITSELF WILL MOVE THROUGH THE CENTRAL GREAT LAKES SATURDAY
NIGHT AND SUNDAY...PROVIDING A DEEPER MOIST LAYER UP TO AT LEAST 700
MB AND FORCING ASSOCIATED WITH THE LOW AND UPPER LEVEL LOW PRESSURE
FEATURES. ALTHOUGH THIS SCENARIO DOES NOT LOOK TO YIELD A WIDESPREAD
SIGNIFICANT SNOWFALL GIVEN THE LIMITED AMOUNT OF AVAILABLE MOISTURE
WITH 285K MIXING RATIOS OF ONLY 0.75 TO 1.25 G/KG...IT STILL LOOKS
ON TRACK TO WARRANT HIGHER POPS AROUND 50 PERCENT FOR THESE PERIODS
WITH A FEW INCHES OF SNOW POSSIBLE. SNOW CHANCES WILL CONTINUE
MONDAY AS A TROUGH SINKS SOUTH ACROSS THE CENTRAL GREAT LAKES. THE
BEST CHANCES FOR SNOW WILL BE ACROSS THE EASTERN THUMB AS THE WIND
DIRECTION BECOMES FAVORABLE FOR ENHANCEMENT FROM LAKE HURON. FURTHER
INLAND CHANCES WILL BE LOWER AS THESE AREAS WILL BE FARTHER AWAY
FROM THE BEST MOISTURE AND FORCING.
HIGH PRESSURE WILL BUILD INTO THE WESTERN GREAT LAKES MONDAY
NIGHT...WHICH WILL DRY OUT THE SNOW ACROSS MUCH OF THE CWA. THE HIGH
WILL MOVE THROUGH THE CENTRAL GREAT LAKES TUESDAY...ON ITS WAY TO
THE EAST COAST ON TUESDAY NIGHT PROVIDING COOL AND DRY CONDITIONS
DURING THIS PERIOD.
THE PATTERN BECOMES COOL AND ACTIVE DURING THE MIDDLE TO LATE PART
OF NEXT WEEK WITH THE PHASING OF A FAST MOVING ALBERTA CLIPPER
SYSTEM AND AN EQUALLY FAST MOVING SYSTEM MOVING TOWARDS THE AREA
FROM THE SOUTHERN PLAINS. WHILE THESE SYSTEMS ARRIVE
QUICKLY...BRINGING SNOW TO THE AREA AS SOON AS WEDNESDAY...ONCE THEY
PHASE THEIR INFLUENCE WILL REMAIN ACROSS THE CENTRAL GREAT LAKES
THROUGH THE END OF THE WEEK AND INTO NEW YEARS DAY. DEPENDING ON THE
MODEL OF CHOICE THE GFS LINGERS A TROUGH ACROSS THE CENTRAL GREAT
LAKES WITH UNSTABLE CYCLONIC FLOW WHILE THE ECMWF OCCLUDES THE
SURFACE LOW AND CREATES A 500 MB CUT OFF LOW ACROSS THE AREA.
DESPITE THE DIFFERING SOLUTIONS BOTH MODELS AGREE ON A COOL SNOWY
PATTERN DURING THIS TIME PERIOD...THEREFORE WILL PLACE A BLANKET
CHANCE OF SNOW FROM THE MIDDLE PORTION OF THE WEEK THROUGH NEW YEARS
DAY. DESPITE THE SNOWY PATTERN...SIGNIFICANT SNOWFALL AMOUNTS ARE
NOT EXPECTED GIVEN THE LIMITED AMOUNT OF MOISTURE WITH 290K MIXING
RATIOS OF 1 G/KG OR LESS ONCE THE INITIAL SYSTEM MOVES THROUGH ON
WEDNESDAY NIGHT. THE COOL UNSTABLE AIR WITH A LINGERING LOW PRESSURE
SYSTEM LOOKS TO BE THE KIND OF SYSTEM THAT GRINDS OUT AN INCH OR TWO
OF SNOW EACH DAY. THE BEST CHANCE FOR SEVERAL INCHES WILL BE
WEDNESDAY AND WEDNESDAY NIGHT AS THE LOW ITSELF PASSES THROUGH THE
AREA WITH BETTER MIXING RATIOS AROUND 2 G/KG. EVEN THEN QPF AMOUNTS
SUGGEST ONLY 2-3 INCHES OF SNOW AT BEST DURING THIS 24 HOUR PERIOD
WITH LITTLE TO MODEST ISENTROPIC AND FRONTOGENETIC FORCING.
MARINE...
STRONG EASTERLY WINDS WILL CONTINUE ACROSS THE CENTRAL GREAT LAKES
AS A STRONG LOW PRESSURE SYSTEM TRACKS STALLS OVER IOWA THIS
EVENING. GALE FORCE WIND GUSTS ARE EXPECTED ACROSS THE NORTHERN HALF
OF LAKE HURON...WITH GUSTS TO 30 KNOTS EXPECTED ACROSS THE REMAINDER
OF THE LAKE. WINDS ARE EXPECTED TO DECREASE OVERNIGHT TONIGHT AS THE
LOW PRESSURE SYSTEM BEGINS TO WEAKEN AND TRACK EASTWARD.
IN ADDITION TO THE WINDS...PRECIPITATION WILL OCCUR ACROSS THE
CENTRAL GREAT LAKES AS THIS SYSTEM TRACKS TO OUR EAST. RAIN WILL
CHANGE OVER TO A WINTRY MIX AND THEN ALL SNOW BY SATURDAY MORNING.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...
GALE WARNING...LHZ361-LHZ362...UNTIL 4 AM SATURDAY.
SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT
HURON INCLUDING OUTER SAGINAW BAY...UNTIL 4 AM SATURDAY.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
AVIATION.....MR
SHORT TERM...DRK
LONG TERM....KURIMSKI
MARINE.......DRK
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