FXUS63 KDTX 141802
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
102 PM EST MON DEC 14 2009
.AVIATION...
LIFR CONDITIONS WILL PREVAIL ACROSS THE AREA EARLY IN THE 18Z TAF
PERIOD...WITH FURTHER DECORATION IN SKIES/VISIBILITIES AS WE
PROGRESS INTO THE AFTERNOON. A WEAK SURFACE FRONT CURRENTLY JUST
SOUTH OF DTW WILL SLOWLY LIFT NORTH THIS AFTERNOON AS A WEAK AREA
OF LOW PRESSURE QUICKLY APPROACHES THEN TRACKS ACROSS FNT.
ADDITIONAL LOW- LEVEL MOISTURE WILL FILL IN ALONG AND BEHIND THIS
BOUNDARY...DROPPING CEILINGS AND VISIBILITIES TO VLIFR AT TIMES
FROM FNT SOUTHWARD AND ALLOWING DRIZZLE TO CONTINUE. MBS WILL
REMAIN JUST TO NORTH OF THE LOW TRACK...WITH LIFR CONDITIONS
LIKELY HOLDING UNTIL EVENING. MBS WILL ALSO SEE THE BEST CHANCE OF
RAIN AND SNOW DEVELOPING. A COLD FRONT WILL PUSH SOUTHEAST ACROSS
LOWER MICHIGAN THIS EVENING...ALLOWING DRIER AIR TO FILTER INTO
THE REGION. DRIZZLE WILL END BEHIND THE FRONTAL PASSAGE...WITH
RAIN/SNOW SHOWERS TAPERING OFF A FEW HOURS LATER (MOST BY 04Z). A
GRADUAL IMPROVEMENT IN CEILINGS IS EXPECTED THROUGH THE NIGHT AS
THE LOW DEPARTS EAST.
&&
.PREV DISCUSSION...ISSUED 414 AM EST MON DEC 14 2009
SHORT TERM...TODAY
REGIONAL RADAR SHOW SOME LIGHT RETURNS ACROSS PORTIONS OF SOUTHERN
MICHIGAN...FOCUSED MAINLY ALONG A WEAK STATIONARY FRONT ALIGNED
FROM MUSKEGON TO PORT HURON. THESE RETURNS REPRESENT AREAS OF
DRIZZLE. THE 00Z DTX SOUNDING SHOWS ABUNDANT LOW LEVEL MOISTURE
CAPPED BY A STRONG 850MB INVERSION WITH VERY DRY AIR ATOP THE MOIST
LAYER /AND TEMPS IN THE MOIST LAYER NO COLDER THAN -5C/. MODEL
SOUNDINGS MAINTAIN THIS PROFILE THROUGH THE MORNING AND ACTUALLY
SHOW SOME ADDITIONAL LOW LEVEL MOISTURE ADVECTION FROM THE
SOUTH...INDICATING AREAS OF DRIZZLE WILL PERSIST. WITH DEWPOINTS
HOVERING IN THE LOWER 30S AND WITH THE LACK OF LOW LEVEL COLD AIR
ADVECTION THIS MORNING...TEMPS SHOULD HOLD STEADY BETWEEN 32 AND
35 DEG. THIS WILL INHIBIT MUCH IF ANY FREEZING DRIZZLE.
THE 08Z SURFACE ANALYSIS SHOWS A 1003MB LOW OVER KANSAS...ASSOCIATED
WITH AN UPPER WAVE OVER THE CO/KS BORDER. THIS UPPER WAVE IS
FORECAST TO LIFT INTO THE SOUTHERN GREAT LAKES THIS AFTERNOON AND
WEAKEN AS IT ENCOUNTERS MORE CONFLUENT FLOW ALOFT OVER THE REGION.
BASED ON THE WATER VAPOR REPRESENTATION OF THIS WAVE AND THE
PLACEMENT OF THE LOWER TROPOSPHERIC BAROCLINIC ZONE...PREFER THE
MORE NORTHWESTERLY SURFACE LOW TRACK OFFERED BY THE GFS. THIS
SOLUTION WOULD BRING THE LOW INTO WESTERN LOWER MI BY EARLY
AFTERNOON AND ACROSS SOUTHERN LAKE HURON BY EVENING. THE LOWER TO
MID TROPOSPHERIC FRONTAL CIRCULATION WILL STRENGTHEN TO THE NORTH OF
THE SURFACE LOW TRACK IN RESPONSE TO UPPER JET DYNAMICS. THIS WILL
CONTINUE TO PLACE THE BEST FORCING FROM THE NORTHERN SAGINAW VALLEY
INTO NORTHERN LOWER MI. MODEL CROSS SECTIONS INDICATE MIXING RATIOS
UP TO 3 G/KG ADVECTING INTO THE REGION OF ASCENT. THE SPEED OF THIS
SYSTEM WILL HOWEVER PROVIDE ONLY A SHORT WINDOW OF SUFFICIENT LIFT
AND MOISTURE DEPTH TO SUPPORT MEASURABLE PRECIPITATION /FOCUSED
MAINLY DURING THE EARLY AFTERNOON/. MID LEVEL DRYING BY EVENING
SHOULD THEN TRANSITION PRECIPITATION BACK OVER TO DRIZZLE.
MODEL SOUNDINGS CONTINUE TO SUPPORT MAINLY SNOW ACROSS MIDLAND...BAY
AND NORTHERN HURON COUNTIES. GIVEN THE SHORT DURATION OF
LIFT...FORECAST ACCUMULATIONS OF 1 TO 2 INCHES IN THIS REGION LOOKS
REASONABLE. WARMER BOUNDARY LAYER TEMPS FARTHER SOUTH WILL MEAN A
MIX WITH RAIN...WITH THE THERMAL PROFILE SUGGESTING ALL RAIN FOR THE
METRO DETROIT AREA. THE CHANCES OF PRECIPITATION WILL ALSO DROP OFF
DRAMATICALLY FARTHER SOUTH DUE TO A WEAKER AND SHORTER DURATION OF
DYNAMIC FORCING.
LONG TERM...MONDAY NIGHT THROUGH SUNDAY
COLD AIR ADVECTION OVERNIGHT INTO TUESDAY WILL USHER A CHILLY
AIRMASS BACK INTO THE REGION...KEEPING TEMPERATURES BELOW NORMAL
THROUGH MUCH OF THE LONG TERM FORECAST. THE POLAR VORTEX OVER
CENTRAL CANADA IS EXPECTED TO SHIFT TOWARDS ONTARIO AND QUEBEC BY
WEDNESDAY BEFORE RETROGRADING SOUTHWARD AND HELPING TO RE-ESTABLISH
THE LONGWAVE TROUGH OVER THE EASTERN UNITED STATES FOR THE END OF
THE WEEK.
THE LOW PRESSURE SYSTEM THAT WILL TRACK ACROSS LOWER MICHIGAN TODAY
WILL CONTINUE THROUGH THE EASTERN GREAT LAKES OVERNIGHT LEAVING A
SURFACE TROUGH LINGERING ACROSS CENTRAL LOWER MICHIGAN AND LAKE
HURON. DRY MID-LEVEL AIR WILL LIMIT THE POTENTIAL FOR SNOW
OVERNIGHT AS CLOUDS LACK ICE-NUCLEI WITH EVEN THE LOW LEVELS
STARTING TO DRY OUT AS COOLER AIR FILTERS IN. HAVE LEFT A CHANCE
OF SNOW SHOWERS OR LIGHT DRIZZLE IN THE FORECAST GENERALLY ALONG
AND NORTH OF I-69 IN THE VICINITY OF THE SURFACE TROUGH. WE WILL
KEEP AN EYE ON FREEZING DRIZZLE POTENTIAL FOR TONIGHT BUT WILL
GENERALLY EXPECT DRIZZLE TO END AS THE NIGHT PROGRESSES AND
TEMPERATURES COOL BELOW THE FREEZING MARK. THIS TROUGH APPEARS TO
PIVOT SOUTH ACROSS THE TIP OF THE THUMB ON TUESDAY AND MAY BE ABLE
TO BRING A RELATIVELY UNORGANIZED BAND OF LAKE EFFECT SNOW SHOWERS
INTO HURON COUNTY. ACCUMULATIONS ARE EXPECTED TO BE MINOR AS THE
FLOW QUICKLY SHIFTS AROUND TO THE NORTHWEST AND PUSHES ANY
ADDITIONAL SNOW SHOWERS OFF SHORE. OTHERWISE CHANCES OF SNOW
DECREASE AS YOU MOVE SOUTH TOWARDS DETROIT ON TUESDAY WITH THE
CONVECTIVE DEPTH OVER SOUTHERN LAKE MICHIGAN LIMITING THE INLAND
EXTENT OF SNOW SHOWERS.
UPPER LEVEL TROUGH AXIS PULLS AWAY TOWARDS NEWFOUNDLAND BY WEDNESDAY
ALLOWING A LARGE AREA OF HIGH PRESSURE TO BUILD INTO THE OHIO
VALLEY. THE PREVAILING FLOW WILL REMAIN OUT OF THE NORTHWEST THROUGH
THE REMAINDER OF THE WORK WEEK WITH HIGH TEMPERATURES LARGELY
CONFINED TO THE MID 20S. A FEW WEAK SHORTWAVES ARE ADVERTISED TO
MOVE THROUGH THE FLOW ALOFT BUT THE ABSENCE OF MOISTURE ASSOCIATED
WITH THESE SYSTEMS WILL RESULT IN JUST A MIX OF SUN AND CLOUDS FROM
WEDNESDAY THROUGH FRIDAY. HAVE LOWERED TEMPERATURES A COUPLE DEGREES
THROUGH THIS TIME FRAME AS LOWER MICHIGAN REMAINS ON THE NORTH
SIDE OF THE LOW LEVEL BAROCLINIC ZONE WITH A CONTINUED COOL AND
DRY LOW LEVEL FLOW OUT OF CANADA.
FORECAST UNCERTAINTY INCREASES INTO NEXT WEEKEND AS MODELS HAVE MADE
SOME LARGE ADJUSTMENTS OVER THE LAST 24 HOURS. AM NOT IMPRESSED WITH
THESE CHANGES AS MODELS APPEAR TO LOSE TRACK OF THE STRONG UPPER JET
WORKING ACROSS THE PACIFIC OCEAN TOWARDS THE UNITED STATES. FOR
NOW WILL KEEP THE COOL AIRMASS OVER THE REGION THROUGH NEXT
WEEKEND BUT WILL BE MONITORING THE LONGWAVE PATTERN AS WE GET
CLOSER IN TIME FOR ADJUSTMENTS TO THE STORM TRACK.
MARINE...
LOW PRESSURE IS FORECAST TO TRACK ACROSS FAR SOUTHERN LAKE HURON
THIS EVENING. WINDS WILL TURN MORE EAST-NORTHEASTERLY AS THIS LOW
PASSES. THE WINDS WILL THEN BACK MORE NORTHWESTERLY AND BECOME QUITE
GUSTY ON TUESDAY AS ARCTIC AIR INFILTRATES THE REGION. ARCTIC HIGH
PRESSURE WILL THEN TAKE UP RESIDENCE ACROSS THE REGION THROUGH THE
REMAINDER OF THE WEEK.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
AVIATION.....HLO
SHORT TERM...SC
LONG TERM....KEC
MARINE.......SC
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
