FXUS63 KDTX 051052
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
552 AM EST SAT DEC 5 2009
.AVIATION...
MOSTLY CLEAR SKIES HAVE CONTINUED SOUTH OF KFNT...WITH NO MORE THAN
A SCT DECK EXPECTED THE REST OF TODAY AS HIGH PRESSURE BRINGS DRY
AIR INTO SOUTHEAST MICHIGAN. AT KFNT/KMBS A VFR BKN DECK OF CLOUDS
SHOULD CONTINUE MUCH OF TODAY AS DIURNAL DRIVEN CU AND LAKE EFFECT
CLOUDS CONTINUE AS THESE SITES WILL BE FURTHER FROM THE DRY AIR
ASSOCIATED WITH THE HIGH PRESSURE RIDGE.
VFR CONDITIONS WILL CONTINUE TONIGHT AS A WEAK TROUGH APPROACHES THE
NORTHERN GREAT LAKES. KFNT/KMBS WILL BE CLOSE ENOUGH TO THE LOW FOR
A CONTINUED BKN DECK WHILE THE SOUTHERN AIRPORTS WILL SEE A SCT DECK.
&&
.PREV DISCUSSION...ISSUED 427 AM EST SAT DEC 5 2009
SHORT TERM...TODAY
A RIDGE OF HIGH PRESSURE NOSING INTO EXTREME SOUTHEASTERN MICHIGAN
HAS BROUGHT MUCH DRIER AIR AND MOSTLY CLEAR SKIES ALONG AND SOUTH OF
M-59. BUFKIT SOUNDINGS SHOW THIS DRY AIR TO STAY IN PLACE THROUGHOUT
TODAY...WITH MORE MOISTURE ALONG AND NORTH OF INTERSTATE 69 WHICH
WILL ALSO BENEFIT FROM MOISTURE OFF THE GREAT LAKES. DESPITE MORE
SUNSHINE ACROSS THE SOUTH...TEMPERATURES WILL STRUGGLE TO GET MUCH
ABOVE 30 AS 850 MB TEMPS BOTTOM OUT TO AROUND -12 CELSIUS. THE RIDGE
BUILDING IN ACROSS THE AREA WILL MEAN LESS OF A PRESSURE GRADIENT
AND LIGHTER WINDS ACROSS THE AREA TODAY. THE RIDGE WILL ALSO PUSH
THE LAKE EFFECT SNOW BANDS FURTHER NORTH AS THE DAY WEARS ON AS IT
BUILDS INTO THE REGION. DESPITE THE CONTINUED LAKE EFFECT ACROSS THE
NORTHERN PORTION OF THE CWA...AMOUNTS WILL BE VERY LIGHT.
LONG TERM...TONIGHT THROUGH FRIDAY
FOCUS IN THE EXTENDED FORECAST CENTERS AROUND TWO IMPENDING STORM
SYSTEMS. THE FIRST STORM WILL IMPACT THE REGION LATE SUNDAY NIGHT
AND MONDAY...AND THE SECOND AND MUCH LARGER SYSTEM IS EXPECTED ON
TUESDAY NIGHT AND WEDNESDAY.
SHORTWAVE ENERGY STRETCHING FROM THE WESTERN GREAT LAKES TO THE
UPPER MIDWEST WILL SLIDE ACROSS THE NORTHERN GREAT LAKES TONIGHT AND
SUNDAY AS THE MAIN UPPER LOW LIFTS NORTHEAST THROUGH ONTARIO. THIS
WILL PUSH A WEAK TROUGH AND ASSOCIATED COLD FRONT DOWN INTO NORTHERN
MICHIGAN AND LAKE HURON LATE TONIGHT AND SUNDAY. THIS BOUNDARY IS
THEN EXPECTED TO STALL THERE INTO SUNDAY NIGHT...WHILE SMALL WAVES
RIDE OVER THE TOP OF IT. UPWARD FORCING FROM THESE WAVES WILL CLIP
THE TRI-CITIES AND THUMB DURING THIS TIMEFRAME...HOWEVER GIVEN WEAK
MOISTURE AND LIFT SHOWN BY THE GFS AND NAM...THINK PRECIPITATION
WILL BE LIMITED TO FLURRIES.
THIS BOUNDARY WILL CONTINUE TO LIE DRAPED OVER CENTRAL LAKE HURON ON
SUNDAY NIGHT...AS LEAD ENERGY EJECTING OUT OF THE PACIFIC NORTHWEST
TROUGH BEGINS TO RACE TOWARDS THE GREAT LAKES. MODELS CONTINUE TO
DIFFER WITH HOW FAR NORTH INTO THE GREAT LAKES THIS ENERGY WILL
LIFT...AND NOW HAVE SOME TIMING DIFFERENCES CENTERING AROUND HOW
QUICKLY THIS WAVE EXITS ON MONDAY. THIS LEADS TO SOME UNCERTAINTY
REGARDING THE TRACK AND STRENGTH OF THE SURFACE LOW CENTER...WHICH
IS PROBLEMATIC SINCE THE MOST INTENSE PRECIPITATION IS EXPECTED TO
FALL WITHIN A FAIRLY NARROW BAND ON THE NORTH SIDE OF THE LOW.
CONSENSUS IMPLIES THE HEAVIEST SWATH OF SNOW WILL FALL ACROSS
CENTRAL MICHIGAN...MAINLY IMPACTING THE TRI-CITIES AND THUMB FOR THE
MONDAY MORNING COMMUTE. SNOW IS EXPECTED TO BEGIN LATE SUNDAY NIGHT
AND CONTINUE INTO MONDAY AFTERNOON AS MOISTURE INCREASES...AND AS
THE APPROACH AND PASSAGE OF THE SURFACE LOW ALLOWS CONVERGENCE ALONG
THE STALLED FRONTAL BOUNDARY TO INCREASE. FORECAST SNOW AMOUNTS
DURING THIS PERIOD CURRENTLY RANGE FROM 2 TO 3 INCHES NORTH OF
SAGINAW AND UP TO ONE INCH SOUTH OF THERE. GIVEN MODEL DIFFERENCES
WITH FORECAST TRACK AND TIMING..AS WELL AS THE NARROW SWATCH OF SNOW
THAT IS EXPECTED...OVERALL CONFIDENCE IN SNOW AMOUNTS IS NOT VERY
HIGH. QUICK SPEED OF THE SYSTEM ACROSS THE AREA WILL LIMIT POTENTIAL
AMOUNTS HOWEVER...WITH 4 INCHES LOOKING LIKE THE WORSE-CASE SCENARIO.
THE TROUGH OVER THE PACIFIC NORTHWEST IS EXPECTED TO DIVE DOWN INTO
THE CENTRAL PLAINS BEFORE LIFTING UP TOWARDS THE GREAT LAKES BY MID
WEEK. 00Z GFS/EURO/HEMI REMAIN IN SOLID AGREEMENT WITH THE CENTER OF
THE SURFACE LOW LIFTING ACROSS FAR SOUTHEAST MICHIGAN (A HAIR
FURTHER NORTH THAN 12Z MODEL CONSENSUS)...WHILE THE 00Z GEM REMAINS
FURTHER NORTH ACROSS THE THUMB AND THE 00Z UKMET HAS REVERTED BACK
TO THE IDEA OF AN EAST COAST SYSTEM. WILL CONTINUE TO FOLLOW THE
TIGHTER CONSENSUS OF THE GFS/EURO/HEMI/PREVIOUS FORECAST. THIS
SYSTEM WILL BE MUCH LARGER IN SCALE THAN THE PRECEDING
ONE...SPREADING A WIDE SWATCH OF PRECIPITATION ACROSS THE GREAT
LAKES TUESDAY NIGHT THROUGH WEDNESDAY EVENING. CURRENTLY EXPECT THE
DEFORMATION ZONE TO LIFT INTO SOUTHEAST MICHIGAN ON TUESDAY
NIGHT...WITH PRECIP CONTINUING THROUGH WEDNESDAY...THEN TAPERING OFF
TO SHOWERS AS THE TROWAL EXITS AND LAKE EFFECT PROCESSES BECOME MORE
DOMINANT. GFS/EURO SHOW STRONG SUPPORT FOR SNOW ONLY AS THE SYSTEM
APPROACHES ON TUESDAY NIGHT...BUT TRY TO SNEAK SOME WARMER AIR AS
FAR NORTH AS PONTIAC ON WEDNESDAY AS THE LOW CROSSES OVERHEAD.
FORECAST SOUNDINGS SUPPORT NEARLY ALL SNOW HOWEVER AT BOTH DETROIT
AND TOLEDO...AND WILL MENTION LIKELY SNOW AND CHANCE RAIN FOR
WEDNESDAY...WITH A CHANGEOVER BACK TO ALL SNOW ON THE BACKSIDE OF
THE SYSTEM BY WEDNESDAY EVENING. THIS SYSTEM NEEDS TO MONITORED VERY
CLOSELY AS IT IS LOOKING MORE LIKELY THAT IT WILL BE THE FIRST BIG
SNOW STORM OF THE 2009-2010 WINTER SEASON. ACCUMULATIONS EXCEEDING 6
INCHES ARE A DEFINITE POSSIBILITY IF CURRENT TRACK PANS OUT...WITH
PRECIP ALMOST ENTIRELY SNOW. ONE OTHER CONCERN WILL BE CONTRIBUTIONS
FROM BOTH LAKES ERIE AND HURON AS STRONG EASTERLY FLOW SETS UP AHEAD
OF THE SYSTEM TUESDAY NIGHT AND EARLY WEDNESDAY. ASIDE FROM LAKE
ENHANCED SNOW...STRONG WINDS OFF THE LAKES COULD LEAD TO AREAS OF
BLOWING AND DRIFTING SNOW NEAR THE SHORELINES. POPS HAVE BEEN BUMPED
UP TO LIKELY AS WE ANTICIPATE THE ARRIVAL OF THIS SYSTEM.
MARINE...
HIGH PRESSURE BUILDING INTO SOUTHEASTERN MICHIGAN WILL LEAD TO
LIGHTER WINDS TODAY WITH A MORE RELAXED PRESSURE GRADIENT. WITH
LIGHTER WINDS AND WAVES SUBSIDING...WILL ALLOW SMALL CRAFT
ADVISORIES TO EXPIRE AT 4 AM. WINDS WILL INCREASE AGAIN LATE TONIGHT
AND INTO SUNDAY MORNING AS A WEAK SURFACE TROUGH PASSES TO THE
NORTH. THE INCREASED WINDS AND LONG FETCH WILL PROBABLY BRING WAVES
BACK UP TO SMALL CRAFT ADVISORY CRITERIA ACROSS THE TIP OF THE
THUMB. DESPITE THE LIKELIHOOD OF SMALL CRAFT ADVISORY
CRITERIA...WILL HOLD OFF ON ISSUING ANY HEADLINES AT THIS POINT.
SEVERAL LOW PRESSURE SYSTEMS MOVING THROUGH THE GREAT LAKES WILL
BRING UNFAVORABLE BOATING CONDITIONS TO THE CENTRAL GREAT LAKES FOR
MUCH OF THE WEEK. IN PARTICULAR A SYSTEM HEADED FOR THE AREA IN THE
MIDDLE OF THE WEEK HAS THE POTENTIAL TO BRING GALE FORCE WINDS TO
THE OPEN AND NEARSHORE WATERS AS IT MOVES THROUGH THE REGION.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
AVIATION.....KURIMSKI
SHORT TERM...KURIMSKI
LONG TERM....HLO
MARINE.......KURIMSKI
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
