FXUS63 KDTX 150513
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1213 AM EST TUE DEC 15 2009
.AVIATION...
CEILINGS HAVE LARGELY IMPROVED INTO THE MVFR CATEGORY ACROSS MUCH OF
SOUTHEASTERN MICHIGAN. THIS IS NOT THE CASE FOR THE IRISH HILLS
HOWEVER...AS LIFR/IFR STRATUS HOLDS ON. INCREASED DRY AIR ADVECTION
IS EXPECTED TO OCCUR LATER TONIGHT WHICH SHOULD ALLOW CEILINGS TO
EVENTUALLY LIFT OVER THE 1 KFT MARK. RESIDUAL MOISTURE AND UNSTABLE
CONDITIONS OVER THE GREAT LAKES WILL KEEP A SOLID MVFR BLANKET OVER
SOUTHEASTERN MICHIGAN TOMORROW. WINDS WILL VEER WESTERLY LATE THIS
EVENING AND BECOME GUSTY LATE TOMORROW MORNING.
&&
.PREV DISCUSSION...ISSUED 357 PM EST MON DEC 14 2009
SHORT TERM...THROUGH TONIGHT
UPPER SHORTWAVE EVIDENT ON WATER VAPOR OVER IOWA WILL QUICKLY ZIP
ACROSS LOWER MICHIGAN AND INTO ONTARIO THIS EVENING AS IT RIDES A
150 KT JET STREAK ACROSS THE GREAT LAKES. SURFACE LOW PRESSURE OUT
AHEAD OF THIS FEATURE WILL LIFT FROM SOUTHWEST MICHIGAN TO FAR
SOUTHERN LAKE HURON BY 7 PM TONIGHT PER LATEST MODEL CONSENSUS.
WIDESPREAD DRIZZLE CONTINUES ACROSS THE AREA THIS AFTERNOON IN
ADVANCE OF THIS FEATURE...ESPECIALLY AS ADDITIONAL LOW-LEVEL
MOISTURE AND WARM AIR CONTINUES TO SEEP UP INTO FAR SOUTHERN
MICHIGAN...WHERE A WEAK LOW-LEVEL WARM FRONT LIFTED UP FROM OHIO
EARLIER TODAY. MORE ORGANIZED AREA OF RAIN/SNOW SHOWERS HAS BEGUN TO
DEVELOP TO THE NORTH OF THE SURFACE LOW AS THE AREA OF BETTER FGEN
HAS SLID OVERHEAD. RAIN/SNOW WILL BE MOST PRONOUNCED TO THE NORTH OF
THE LOW CENTER TRACK...MAINLY IMPACTING THE TRI-CITIES AND THUMB
AREAS. CONTINUE TO EXPECT A MIX OF RAIN THERE TONIGHT...BUT AS IR
SATELLITE ICE ENHANCEMENT SHOWS LIMITED POTENTIAL FOR ICE NUCLEI
IN THE CLOUDS BOTH CURRENTLY OVER THE AREA AND UPSTREAM...HAVE
REDUCED SNOW AMOUNTS TO LESS THAN AN INCH TOTAL FOR THE AFTERNOON
AND OVERNIGHT PERIOD COMBINED. COLD FRONT WILL DROP DOWN ACROSS
SOUTHEAST MICHIGAN THIS EVENING IN THE WAKE OF THE LOW PASSAGE.
MODELS CONTINUE TO INDICATE THE AIRMASS BEHIND THIS SYSTEM WILL BE
UNSATURATED THROUGH THE SNOW GROWTH REGION...AND FORECAST SOUNDINGS
INDICATE MORE UNIDIRECTIONAL WIND FIELDS AND SHALLOWER MOISTURE WILL
END DRIZZLE AS WELL.
LIGHT SHOWERS WILL LINGER INTO THE EVENING BEHIND THE FRONT...WITH
LOCATIONS SOUTH OF FLINT NOT EXPECTED TO SEE SNOW AS COLDER AIR AT
THE SURFACE IS NOT EXPECTED UNTIL AFTER DRIER MID-LEVEL AIR ARRIVES.
FURTHER NORTH...RAIN SHOWERS WILL CHANGE TO LIGHT SNOW
SHOWERS...LINGERING THROUGHOUT THE NIGHT ACROSS THE TRI-CITIES AND
THUMB AS WEST-EAST ORIENTATED SURFACE TROUGHING EXTENDING ACROSS
LAKE HURON MAINTAINS LOW-LEVEL CONVERGENCE. SNOW AMOUNTS OVERALL
WILL BE VERY LIGHT...RANGING FROM A DUSTING TO AN INCH AT MOST.
LONG TERM...TUESDAY THROUGH MONDAY
COLDER AIR WILL CONTINUE TO FUNNEL IN EARLY TUESDAY...BEFORE
STRENGTHENING LATE TUESDAY/TUESDAY NIGHT AS THE SOUTHERN END OF AN
UPPER LEVEL TROUGH SWINGS THROUGH. THIS WILL KEEP TEMPERATURES
STEADY THROUGH MUCH OF THE DAY WITH HIGHS RANGING FROM AROUND
FREEZING SOUTH TO MID 20S NORTH. THE DEGREE OF COLD AIR ADVECTION
WILL SEND READINGS DOWN INTO THE MID-UPPER TEENS BY WEDNESDAY
MORNING. SCATTERED/NUMEROUS SNOW SHOWERS WILL BE SUSTAINED EARLY BY
SOME ENHANCED CONVERGENCE ALONG A RESIDUAL SFC TROUGH PIVOTING
THROUGH...ESPECIALLY ACROSS THE THUMB REGION. THE COMBINATION OF
COLD AIR ADVECTION/STEEPENING LOW LEVEL LAPSE RATES AND SOME
UPSTREAM LAKE EFFECT ENHANCEMENT PROVIDED BY THE PASSAGE OF A
SHORTWAVE EMBEDDED WITHING THE MEAN TROUGH WILL MAINTAIN A CHANCE OF
SNOW SHOWERS THROUGH THE EARLY EVENING. ACCUMULATIONS WILL REMAIN
MINOR THROUGH THE DAY...WITH HURON COUNTY BEING THE MOST FAVORED
AREA FOR SEEING ANYTHING MORE THAN A QUARTER OF AN INCH. UPSTREAM
LAKE EFFECT PARAMETERS QUICKLY BECOME UNIMPRESSIVE TUESDAY NIGHT AS
A DEEP DRY LAYER EFFECTIVELY LOWERS INVERSION HEIGHTS. WITH LITTLE
ADDITIONAL SUPPORT...THIS WILL CONFINE LES ACTIVITY TO THE WEST WITH
JUST LINGERING FLURRIES FOR THE OVERNIGHT HOURS.
BROAD NORTHWEST FLOW WILL MAINTAIN A COOL BUT RELATIVELY QUIET
STRETCH OF WX FOR THE MID TO LATTER WEEK PERIOD. DEEPER DRYING OF
THE LOWER LAYERS WILL BRING AT LEAST PARTIAL SUNSHINE WEDNESDAY IN
THE PRESENCE OF LOW LEVEL ANTICYCLONIC FLOW AND STRONGER
SUBSIDENCE. GIVEN THE PROJECTED STRENGTH OF THE RESIDENT AIRMASS
/-11 TO -14C AT 925 MB/ WILL REMAIN ON THE COOLER END OF GUIDANCE
WITH HIGHS OF LOW-MID 20S. THE DRY MID LEVELS AND A WEAK WIND FIELD
WILL PROMOTE GOOD RADIATIONAL COOLING WEDNESDAY NIGHT...ALTHOUGH
SOME PESKY UPPER LEVEL CLOUDINESS MAY DETER THE AIRMASS FROM
REALIZING FULL COOLING POTENTIAL. REGARDLESS STILL LOOKING AT LOWS
WELL INTO THE TEENS. SIMILAR THERMAL FIELDS WILL EXIST FOR THURSDAY
AND FRIDAY. WEAK SHORTWAVE EMBEDDED WITHIN THE NORTHWEST FLOW WILL
SLIP ACROSS NORTHERN LOWER ON THURSDAY. AVAILABLE MOISTURE AND
OVERALL FORCING LOOKS PALTRY WITH THIS SYSTEM SO EXPECT LITTLE
MORE THAN SOME INCREASE IN MID LEVEL CLOUDS.
FEW CHANGES MADE INTO THE WEEKEND AS THE MODELS CONTINUE TO
CONVERGENCE ON A MORE AMPLIFIED/BLOCKED UPPER LEVEL PATTERN.
SYSTEM MOVING THROUGH THE GREAT LAKES TODAY/TONIGHT WILL EVENTUALLY
CLOSE OFF WHILE STALLING OVER THE CANADIAN MARITIMES BY MIDWEEK.
THIS SYSTEM WILL THEN UNDERGO SOME FORM OF RETROGRESSION WHILE ALSO
PULLING ADDITIONAL ENERGY SOUTH OUT OF THE MEAN CENTRAL CANADIAN
POLAR VORTEX. THIS ALL POINTS TO A DEEPENING LONGWAVE TROUGH
EVOLVING THROUGH THE WEEKEND AND REMAINING FIRMLY IN PLACE INTO
EARLY NEXT WEEK. WHILE THE SPECIFIC DETAILS ARE STILL VAGUE AT
THIS TIME SCALE...THIS PATTERN EVOLUTION WOULD CERTAINLY ENSURE
TEMPERATURES REMAIN SOLIDLY BELOW NORMAL DURING THIS TIME. THE
INCREASING COLD AIR ADVECTION/CYCLONIC FLOW AND LAKE EFFECT
CONTRIBUTIONS WILL ALSO BRING SNOW SHOWERS BACK INTO THE PICTURE.
MARINE...
LOW PRESSURE OVER SOUTHWEST MICHIGAN WILL QUICKLY TRACK ACROSS FAR
SOUTHERN LAKE HURON INTO ONTARIO THIS EVENING. A COLD FRONT WILL
PUSH ACROSS THE REGION THIS EVENING IN THE WAKE OF THIS
SYSTEM...FLIPPING WINDS TO THE WEST-NORTHWEST. WINDS BEHIND THE
FRONT TONIGHT ARE NOT EXPECTED TO BECOME TOO STRONG...WITH STRONGER
GUSTS BETWEEN 20 AND 25 KNOTS LIMITED TO THE OPEN WATERS OF CENTRAL
LAKE HURON. WINDS WILL INCREASE TOMORROW HOWEVER AS ADDITIONAL COLD
AIR ARRIVES AND STRONG SURFACE HIGH PRESSURE BUILDING WEST OF THE
GREAT LAKES TIGHTENS THE SURFACE PRESSURE GRADIENT. NORTHWESTERLY
WIND GUSTS UP TO 25 KNOTS ARE EXPECTED TO DEVELOP BY TUESDAY
EVENING...AND SMALL CRAFT ADVISORIES MAY BE NECESSARY.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...
SMALL CRAFT ADVISORY...OUTER SAGINAW BAY AND THE NEARSHORE WATERS
FROM PORT AUSTIN TO HARBOR BEACH...FROM 4 AM TUESDAY TO 10 AM
WEDNESDAY.
SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM HARBOR BEACH TO PORT
HURON...FROM 7 AM TUESDAY TO 4 AM WEDNESDAY.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
AVIATION.....CB
SHORT TERM...HLO
LONG TERM....MR
MARINE.......HLO
YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
