FXUS63 KDTX 302113
AFDDTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
413 PM EST MON NOV 30 2009
.SHORT TERM...THIS AFTERNOON AND TONIGHT
A SMALL...YET VIGOROUS...CLIPPER SYSTEM IS SLIDING SOUTHWARD INTO
PORTIONS OF THE MINNESOTA ARROWHEAD AND IS EXPECTED TO CLIP THE
CENTRAL GREAT LAKES OVERNIGHT. GENERALLY...THE PROGGED SYSTEM
DYNAMICS ARE NOTEWORTHY...UPPER LEVEL DIV AND 285K ISENTROPIC LIFT
ALONG A WELL DEVELOPED THETA E RIDGE. UPSTREAM RADAR AND
OBSERVATIONS ACROSS PORTIONS OF NORTHERN MN/WI HAVE SUPPORTED A
SYSTEM THAT IS REALIZING POTENTIAL. THE PROBLEM IS...MODEL SOUNDINGS
AND THE STABILITY PROFILE IS PUTRID WITH AN ABUNDANCE OF DRY AIR AND
A DEVELOPING 800-600MB INVERSION. MODEL GUIDANCE ALSO SUPPORTS THE
MORE FAVORABLE DYNAMICS/MOISTURE TO PASS THROUGH LOWER MICHIGAN
(FROM BOTH THE PERSPECTIVE OF 1000-500MB HEIGHT FALLS...AND THE
CLEANER ISENTROPIC ASCENT).
THE BETTER COLLOCATION OF FORCING/MOISTURE IS EXPECTED TO OVERSPREAD
THE FORECAST AREA BETWEEN 3-6Z TONIGHT. THE EVENT IS EXPECTED TO BE
A HIGHER POP/LOW QPF EVENT...MAINTAINED LIKELY POPS WITH A COUPLE
HUNDREDTHS OF LIQUID OR LESS. WITH THE HOPES THAT ICE PROCESSES WILL
BE INTRODUCED...THE BULK OF THE PRECIPITATION IS EXPECTED TO FALL IN
FROZEN FORM WITH FAVORABLE ONSET TIMING OF AROUND MIDNIGHT AND
THERMAL PROFILES THAT ARE LARGELY BELOW 0C. WITH THE LACK OF ANY
STRONG PRECIPITATION RATES AND SURFACE TEMPERATURES IN THE UPPER
30S...MUCH OF THE AREA WILL NOT OBSERVE AN ACCUMULATION...ALTHOUGH A
DUSTING IS CERTAINLY POSSIBLE ACROSS THE FAR NORTH. LOWS ARE
EXPECTED TO DROP INTO THE LOWER 30S.
&&
.LONG TERM...
THE STRONG JET MAX WILL TAKE SNOW OUT OF THE AREA BY SUNRISE
TUESDAY MORNING. THIS WILL BE FOLLOWED BY RAPID SHORT WAVE RIDGE
DEVELOPMENT OVER THE GREAT LAKES AS THE NEXT LOW PRESSURE SYSTEM
DEVELOPS IN THE PLAINS. SOUTHWEST FLOW WARM ADVECTION WILL BE
ADEQUATE ENOUGH TO RAISE HIGH TEMPS BACK INTO THE LOWER TO MID 40S
DEPENDING ON CLOUD COVER. EXPECT SOME PATCHES OF LAKE CLOUDS TO
BECOME TRAPPED BELOW THE DEVELOPING INVERSION IN THE STYLE OF A
WARM FRONT, MUCH LIKE THE DEPICTION OFFERED BY THE GFS LOW LEVEL
RH PROFILES. IT WILL OTHERWISE BE A DRY WARM ADVECTION PATTERN BUT
THE EXTENT OF THE LOW CLOUDS SUGGESTS MAINTAINING A MODEST WARMING
TREND NO GREATER THAN THE NUMBERS OFFERED IN THE 12Z GUIDANCE. THE
SOUTHERLY GRADIENT FLOW WILL THEN LEAD INTO A MILD NIGHT FOR THIS
TIME OF YEAR LIKELY WITH EVENING LOWS AND RISING TEMPERATURES
AFTER MIDNIGHT.
MILD AIR WILL THEN BE FIRMLY IN PLACE OVER SE MICHIGAN AS THE GULF
SYSTEM MAKES ITS NORTHWARD MOVE DURING WEDNESDAY. THE TRACK OF THIS
SYSTEM HAS BEEN THE SUBJECT OF FORECAST CONCERN FOR LAST SEVERAL
DAYS AND REMAINS FRONT AND CENTER TODAY. DUE TO THE AMPLIFYING LONG
WAVE PATTERN OVER THE PACIFIC AND WEST COAST, A FARTHER WEST HEIGHT
FALL CENTER DOES SEEM TO HAVE DEVELOPED IN THE MODELS OVER THE LAST
FEW RUNS IN THE NORTHERN PLAINS AND CENTRAL ROCKIES. THIS HAS ALSO
LED TO A CORRESPONDINGLY LARGER RIDGE CENTERED OVER EASTERN CANADA
IN ADVANCE OF THE GULF LOW. DUE TO THIS STRONGER RIDGE, AND
JUST AS IMPORTANT AS THE RESULTING FARTHER WEST TRACK OF THE GULF
SYSTEM, IS THE SLOWER PROGRESSION OF THE COLD FRONT ASSOCIATED WITH
THE WAVE MOVING THROUGH NORTHERN ONTARIO. THIS OF COURSE BRINGS INTO
QUESTION THE AMOUNT OF COLD AIR THAT WILL BE IN PLACE OVER SE
MICHIGAN AS THE GULF LOW MOVES FROM THE TENNESSEE VALLEY INTO
EASTERN OHIO WEDNESDAY NIGHT. AS IT STANDS NOW, THERE IS GOOD MODEL
AGREEMENT ON ALL RAIN AT ONSET WEDNESDAY EVENING WITH PERHAPS THE
EXCEPTION BEING A MIX IN THE TRI CITIES. INSTEAD OF THE COLD AIR
ALREADY BEING IN PLACE IN ADVANCE OF THE GULF LOW, IT WILL HAVE TO
BE DRAWN INTO THE SYSTEM AS IT APPROACHES. THIS WILL RESULT IN A
GRADUAL CHANGE FROM RAIN TO SNOW ACROSS OUR AREA DURING THE NIGHT
WITH THE MOST LIKELY SNOW ACCUMULATION IN THE 2 TO 4 INCH RANGE IN
ABOUT AN 18 HOUR PERIOD BETWEEN SUNSET WEDNESDAY NIGHT IN THE TRI
CITIES THROUGH ABOUT NOON THURSDAY AT POINTS FARTHEST EAST TOWARD
PORT HURON. THESE NUMBERS REMAIN SUBJECT TO ADDITIONAL TRACK AND
STRENGTH ADJUSTMENTS ON THE SYSTEM AND ASSESSMENTS ON THE PACE OF
LOW LEVEL COLD AIR ADVANCING INTO THE REGION, ALL OF WHICH ARE FULLY
EXPECTED TO BE ADJUSTED OVER THE NEXT FEW FORECAST CYCLES. FOR NOW,
THE 12Z GFS LOOKS LIKE A PRETTY GOOD REPRESENTATION OF THE TRACK OF
THE SYSTEM AND THE PACE OF COOLING IN THE LOW LEVELS JUDGING BY
1000-850 MB THICKNESS. THE STRENGTH OF THE SYSTEM, AND PERHAPS THE
TRACK AS WELL, IS SUBJECT TO ADJUSTMENTS BASED ON INFLUENCE FROM
POTENTIAL MERGING HEIGHT FALL INTERACTIONS WITH THE UPSTREAM TROUGH.
THE 12Z GFS IS ON THE DEEPER SIDE OF THE 12Z MODEL SOLUTIONS IN THAT
REGARD. THE SNOW ACCUMULATIONS IN OUR FORECAST DO ALSO MAKE AN
ATTEMPT AT FACTORING IN THE POTENTIAL FOR HIGHER PRECIPITATION RATES
AND WET BULB COOLING DUE TO MESOSCALE FORCING IN THE TROWAL OF A WELL
DEVELOPED SYSTEM MOVING JUST TO OUR SOUTH AND EAST.
REGARDLESS OF HOW THINGS TURN OUT WITH THE TRACK OF THE MID WEEK
SYSTEM, THERE REMAINS REASONABLE CONFIDENCE THAT IT WILL MOVE TO OUR
EAST THURSDAY NIGHT. THE UPPER LEVEL TROUGH WILL THEN LINGER
OVERHEAD THROUGH FRIDAY AND SATURDAY. DEEP CYCLONIC FLOW WILL
COMBINE WITH THE COLD AIR MASS TAKING UP RESIDENCE OVER LOWER
MICHIGAN TO KEEP SNOW SHOWERS ACTIVE DURING THE PERIOD. HIGHS
LIMITED TO THE 30S ARE ACTUALLY IN THE NEIGHBORHOOD OF NORMAL FOR
THE FIRST WEEKEND IN DECEMBER.
GIVEN THE PERSISTENCE OF A HIGHLY AMPLIFIED LONG WAVE PATTERN FROM
THE PACIFIC THROUGH NORTH AMERICA, THE MOST REASONABLE GLOBAL MODEL
SOLUTIONS SHOW THE UPPER TROUGH MOVING TO OUR EAST BY SUNDAY AS A
NEW ROUND OF HEIGHT FALLS TAKE PLACE OVER THE ROCKIES AND PLAINS.
THIS WILL MAINTAIN THE LONG WAVE TROUGH OVER THE CENTRAL PORTION OF
NORTH AMERICA VIA THE PROGRESSION OF SHORT WAVE FEATURES. OTHERWISE,
PREDICTABILITY IS VERY LOW IN REGARD TO TIMING AND INTENSITY OF
THESE SHORT WAVES. PLAN TO LEAN THE FORECAST TOWARD DRY CONDITIONS
WITH A MODEST TEMPERATURE REBOUND BY NEXT MONDAY AS SOME SORT OF
SOUTHERLY FLOW SEEMS MOST LIKELY TO DEVELOP.
&&
.MARINE...
A RELATIVELY STRONG UPPER LEVEL DISTURBANCE WILL SWING QUICKLY
THROUGH THE GREAT LAKES OVERNIGHT. A DIFFICULT FORECAST TO MAKE IN
REGARDS TO THE STRENGTH OF THE 10M WINDSPEEDS ALONG AND
IMMEDIATELY BEHIND THE ATTENDANT COLD FRONT. MODEL GUIDANCE
ARRIVED MORE BULLISH ON WINDS THIS MORNING WITH PROGS SETTLING
NEAR GALE CRITERIA (34 KNOTS). THE MAIN QUESTION IS WHETHER A
MESOSCALE LOW PRESSURE CENTER CAN TAKE SHAPE TONIGHT ACROSS THE
NORTHERN WATERS OF LAKE HURON. THIS SURFACE LOW IS IMPORTANT AS IT
WILL MODULATE THE PRESSURE GRADIENT LOCALLY AND ALLOW FOR A BRIEF
PERIOD OF GALE FORCE WINDS ACROSS THE SOUTHERN WATERS OF LAKE
HURON. GIVEN THE LOWER STABILITY OVER THE WARM WATERS OF LAKE
HURON AND THE PROVIDED FORCING...FEEL THIS SURFACE REFLECTION WILL
EMERGE. HAVE ISSUED A GALE WARNING 6-12Z FOR THE OPEN WATERS OF
LAKE HURON FROM PRESQUE ISLE TO HARBOR BEACH. TO THE SOUTH...A
MIXED LAYER IS EXPECTED TO SPREAD ACROSS FAR SOUTHERN LOWER
MICHIGAN. HAVE ISSUED SMALL CRAFT ADVISORIES FOR INNER SAGINAW
BAY...LAKE ST CLAIR...AND THE MICHIGAN WATERS OF LAKE ERIE.
A BRIEF PERIOD OF QUIET WEATHER IS EXPECTED TUESDAY AND PART OF THE
DAY WEDNESDAY WITH SURFACE RIDGING. THAT WILL BE SHORT
LIVED...HOWEVER...AS A STRONG LOW PRESSURE IS EXPECTED TO LIFT FROM
THE GULF COAST THROUGH THE OHIO RIVER VALLEY WEDNESDAY NIGHT AND
THURSDAY. EXACT POSITIONING OF THIS STORM SYSTEM REMAINS IN
QUESTION...BUT THE POTENTIAL FOR GALE FORCE WINDS EXISTS LATE
WEDNESDAY NIGHT AND ON THURSDAY.
&&
.PREV DISCUSSION...ISSUED 103 PM EST MON NOV 30 2009
AVIATION...
CLEAR SECTIONS IN THE OVERCAST ARE BEGINNING TO FILL THIS
AFTERNOON UNDER INSOLATION. A SHORTWAVE TROUGH WILL DIG INTO THE
GREAT LAKES REGION OVERNIGHT. WHILE DYNAMICS WITH THIS SYSTEM ARE
FAIRLY ROBUST...QUALITY AND DEPTH OF MOISTURE IS LACKING. DID
MAINTAIN A DRY FORECAST MENTION BUT LOWERED THE FORECASTED CEILINGS
A BIT. THE ATMOSPHERE IS ANTICIPATED TO SATURATE A SHORT TIME
TOMORROW MORNING AT THE BASE OF A STRENGTHENING INVERSION
010-020KFT. SURFACE WINDS ARE EXPECTED TO BACK WITH TIME BUT
REMAINED MIXED BETWEEN 10-15KTS.
&&
.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...
GALE WARNING...LHZ362-LHZ363-LHZ462...FROM 1 AM TUESDAY TO 7 AM
TUESDAY.
SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT
HURON INCLUDING OUTER SAGINAW BAY...UNTIL 10 AM TUESDAY.
SMALL CRAFT ADVISORY...INNER SAGINAW BAY...UNTIL 10 AM TUESDAY.
LAKE ST CLAIR...
SMALL CRAFT ADVISORY...FROM 10 PM MONDAY TO 10 AM TUESDAY.
MI WATERS OF LAKE ERIE...
SMALL CRAFT ADVISORY...FROM 10 PM MONDAY TO 10 AM TUESDAY.
&&
$$
SHORT TERM...CB
LONG TERM....BT
MARINE.......CB
AVIATION.....CB
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