FXUS63 KDTX 261109
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
609 AM EST THU NOV 26 2009
.AVIATION...
ANY REMAINING IFR CEILINGS WILL BECOME MVFR AND QUITE POSSIBLY LOWER
VFR AROUND 3500-4000 FEET BY MIDDAY AS DRY SLOT CONTINUES TO LIFT ON
THROUGH THE REGION. SHORTWAVE TROUGH AXIS WILL THEN PIVOT INTO LOWER
MICHIGAN MID/LATE AFTERNOON AND BRING LOWER CEILINGS...BACK TO IFR
AND SHOWERS...SOME IN THE FORM OF SNOW FLAKES FOR PTK/FNT/MBS. THIS
MOISTURE WILL BE SWEPT EAST BY 04Z-06Z AS TROUGH AXIS AND ASSOCIATED
COLD FRONT EXIT. SOUTHWEST WINDS WILL BECOME NORTHWEST IN THE WAKE
OF THIS FRONT...WITH GUSTS TO AROUND 25 KNOTS. CEILINGS WILL EDGE UP
INTO THE MVFR RANGE AGAIN WITH THIS SLIGHTLY DRIER LOW LEVEL FLOW.
&&
.PREV DISCUSSION...ISSUED 352 AM EST THU NOV 26 2009
SHORT TERM...TODAY
DRY SLOT WILL BE WORKING NORTH THROUGH THE REGION EARLY THIS MORNING
WITH STEADY LIGHT RAIN PIVOTING TO AREAS FROM THE SAGINAW VALLEY TO
THE FAR NORTHERN THUMB DURING THE MORNING. FURTHER SOUTH...SCATTERED
SHOWERS OR PATCHY DRIZZLE WILL STILL BE POSSIBLE...BUT COVERAGE WILL
BE MUCH LESS. NORTHERN STREAM VORTICITY CENTER WILL THEN PIVOT INTO
THE AREA LATER TODAY...BRINGING A MUCH BETTER CHANCE OF SHOWERS BY
MID/LATE AFTERNOON.
TEMPERATURES WILL BE COOLER TODAY...WITH MORNING HIGHS IN THE LOW TO
MID 40S. TEMPERATURES WILL BE STEADY INTO EARLY AFTERNOON...AND THEN
FALL AS THIS NORTHERN STREAM SHORTWAVE PULLS COLDER AIR INTO LOWER
MICHIGAN DURING THE AFTERNOON.
LONG TERM...TONIGHT THROUGH NEXT WEDNESDAY
THE UPPER LEVEL LOW TRAVERSING IN VICINITY OF THE SOUTHERN LAKE
MICHIGAN RIM...WILL DRIFT NORTHEASTWARD PLACING OVER NORTHERN LAKE
HURON TONIGHT. NEUTRAL TO WARM AIR ADVECTION WITHIN THE NORTHERN
DEFORMATION FLANK/THERMAL TROUGH WILL QUICKLY BE DISRUPTED AT THE
START OF THE PERIOD WITH THE LOW PASSING THROUGH/MODEST
NORTHWESTERLIES BUILDING IN THE WAKE. SECONDARY COLD AIR ADVECTION
WILL STEEPEN LAPSE RATES TRANSITIONING PRECIPITATION ACTIVITY TO
THAT OF A SHOWER VARIETY. THE NWP SUITE ISN/T IMPRESSIVE WITH
NEITHER THE COLUMN MOISTURE WITHIN THE ATMOSPHERIC SLAB OF LOWER
STATIC STABILITY...NOR THE MAGNITUDE OF THE FORCING FOR ASCENT
(PRIMARILY WEAK U/L DIV...FOCUSED CVA). THE BEST CHANCE OF
PRECIPITATION APPEARS DURING THE EVENING HOURS ALONG THE ORPHANED
THERMAL TROUGH AXIS AS THE STEEPENED MIDLEVEL LAPSE RATES (-7 TO -8C
850MB TEMPS) ARRIVE FROM THE NORTHWEST (BEST COLLOCATION APPEARS
ACROSS THE THUMB). WHILE THERE WILL BE THE POTENTIAL FOR A MIX OF
FROZEN/LIQUID PHASES...MOST METRICS SUGGEST THE WINDOW OF
OPPORTUNITY/DEPTH OF SATURATION THROUGH -10C WILL BE FLEETING. WITH
THAT SAID...A DUSTING OR A MINOR ACCUMULATION IS POSSIBLE FOR THE
THUMB REGION WITH HEALTHIER PRECIPITATION RATES AND TEMPERATURES
DIPPING INTO THE LOWER 30S.
RAPID WARM AIR ADVECTION WITH A LOWERING SUBSIDENCE INVERSION WILL
TAKE FOOTING EARLY ON FRIDAY. THIS WILL EFFECTIVELY SHUT DOWN THE
REMAINING ORGANIZED PRECIPITATION. DEEP COLUMN RIDGING WILL THEN
INFLUENCE THE WEATHER INTO SUNDAY...PROVIDING QUIET CONDITIONS.
MODEL SOUNDINGS SUGGEST STRATUS WILL BE STUBBORN AND FAVOR A
SOLUTION WITH COOLER TEMPERATURES/REDUCED MIXING HEIGHTS. EXPECT
HIGHS TO REACH NEAR 40 ON FRIDAY AND INTO THE LOWER TO MID 40S ON
SATURDAY.
A MAJOR BUCKLE IN THE U/L WESTERLIES WILL ARRIVE ACROSS THE UPPER
MIDWEST ON SUNDAY. THE SOUTHERN EXTENSION OF THE CYCLONIC VORTICITY
ENERGY IS EXPECTED TO CLOSE OFF ACROSS THE SOUTHWESTERN US. THE
NORTHERN ENERGY...HOWEVER...WILL REMAIN FAIRLY PROGRESSIVE AND SWEEP
ACROSS SOUTHEASTERN MICHIGAN ON MONDAY. THE MODELS HAVE TRENDED
FARTHER SOUTH WITH REGARDS TO THE BAROCLINICITY...WHICH PLACES LOWER
MICHIGAN ON THE COLDER SIDE OF THE QUASI STATIONARY FRONT. THE
AGEOSTROPHIC RESPONSE OF THE RAPIDLY DEVELOPING UPPER LEVEL JET AXIS
IS PROGGED TO PRODUCE DECENT QPF (.1-.3 INCHES)ON SUNDAY. ALL OF THE
THERMAL PROGS SUGGEST THE BULK WILL REMAIN LIQUID ON SUNDAY WITH THE
AID OF DIURNAL HEATING. THE OUTSTANDING QUESTION IS WHETHER OR NOT
DEFORMATION FORCING WILL SLIDE FAR ENOUGH NORTH TO BRING SOME LIGHT
SNOW ACROSS THE FAR SOUTH (SOME DISAGREEMENT EXISTS BETWEEN
GFS/ECMWF AS TO WHICH LAYER WILL BECOME ACTIVE). GIVEN THE LACK OF
RECENT MODEL AGREEMENT/CONTINUITY FELT PRUDENT TO CARRY MUCH OF THE
INHERITED FORECAST FOR ANOTHER CYCLE (DID TREND COOLER WITH PRECIP
TYPE/TEMPS). CONSIDERABLE UNCERTAINTY REMAINS AS TO EXACTLY WHEN THE
DESERT SOUTHWEST ENERGY WILL FINALLY EJECT NORTHEASTWARD.
MARINE...
LOW PRESSURE NEAR THE STRAITS WILL MAINTAIN SOUTHWEST WINDS 20 KNOTS
OR LESS OVER THE MARINE AREAS MUCH OF TODAY. A COLD FRONT WILL THEN
MOVE THROUGH LAKE HURON AND LOWER MICHIGAN TONIGHT AND BRING A ROUND
OF STRONGER NORTHWEST WINDS BY FRIDAY. THE COLDER AIR AND STRONGER
WINDS WILL BUILD THE WAVES ENOUGH OVER SOUTHERN PORTIONS OF LAKE
HURON TO LIKELY REQUIRE A SMALL CRAFT ADVISORY BY THAT TIME. SURFACE
HIGH PRESSURE WILL THEN BUILD QUICKLY THROUGH THE REGION ON SATURDAY
AND ENSURE DRY CONDITIONS. MILDER SOUTHWEST WINDS WILL THEN LAST
THROUGH THE REST OF THE WEEKEND.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.
&&
$$
AVIATION.....DG
SHORT TERM...DG
LONG TERM....CB
MARINE.......DG
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