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000
FXUS63 KDTX 072019
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
319 PM EST SAT DEC 7 2013

.SHORT TERM...THROUGH TONIGHT

MAIN FORECAST CONCERN FOR THE OVERNIGHT PERIOD WILL BE LOW
TEMPERATURES. THE CENTER OF THE EXPANSIVE ARCTIC HIGH OVER THE UPPER
MISSISSIPPI VALLEY WILL DRIFT ACROSS LOWER MI TONIGHT WHILE FORECAST
TO WEAKEN SLIGHTLY. MORNING SOUNDINGS FROM MN/WI SHOW THE AIRMASS IS
VERY DRY WITH PWATS LESS THAN 0.1 INCHES OF WATER. IN ADDITION
DEWPOINTS OVER SE MI ARE ALREADY IN THE SINGLE DIGITS WHICH WILL DIP
SOME AS EVEN DRIER AIR WORKS INTO THE AREA. SKIES CLEARED OUT EARLY
THIS AFTERNOON AS THE LAKE EFFECT CLOUDS COULD NOT STAND UP TO THE
DRY BOUNDARY LAYER THIS FAR AWAY FROM LAKE MI. CONDITIONS WILL BE
FAVORABLE FOR RADIATIONAL COOLING AS SKIES ARE ALREADY
CLEAR...DEWPOINTS ARE IN THE SINGLE DIGITS...AND WINDS WILL GO
NEARLY CALM. MOST MODEL GUIDANCE IS COMING IN A BIT WARM TONIGHT
WITH MINS SIMILAR TO THOSE WHICH WERE ACHIEVED LAST NIGHT. SHAVED
ABOUT 5 DEGREES OFF THOSE VALUES FOR TONIGHT WITH SINGLE DIGITS
GENERALLY NORTH OF I69 WITH VALUES INCREASING SLIGHTLY TOWARD THE
OHIO BORDER. THERE ARE SOME HIGH CLOUDS OVER IOWA WHICH MAY REACH SE
MI OVERNIGHT...SAYS THE NAM...BUT CURRENTLY APPEARS PRETTY THIN AND
RAGGED THUS IT SHOULD NOT AFFECT THE LOWS MUCH AT ALL.

&&

.LONG TERM...SUNDAY THROUGH NEXT SATURDAY

THE UPPER LOW NOW RESIDING OVER THE NRN GREAT BASIN IS FORECAST TO
ROUND THE SRN ROCKIES SUN MORNING THEN RAPIDLY LIFT ACROSS THE GREAT
LAKES SUN NIGHT AS ITS AMPLITUDE DAMPENS. THIS WAVE WILL BE
PROPELLED TO THE NORTHEAST AS ANOTHER POLAR VORTEX DROPS DOWN INTO
CENTRAL CANADA. DESPITE THE SHEARING OUT OF THE UPPER WAVE...SFC
CYCLOGENESIS IS FORECAST ACROSS THE NRN GREAT LAKES SUN NIGHT AS
SOME INTENSIFICATION OF AN UPPER JET STREAK LEADS TO INCREASINGLY
DIVERGENT UPPER FLOW OVER NORTHERN MI. THE EXPECTED LOW TRACK ACROSS
LAKE HURON IS LENDING SOME SUPPORT TO THE STRONGER NAM SOLUTION IN
TERMS OF THE SURFACE PRESSURE FIELDS.

A BROAD REGION OF ISENTROPIC ASCENT ASSOCIATED WITH THIS SYSTEM IS
FORECAST TO OVERSPREAD LOWER MI LATE SUN AFTERNOON THROUGH SUN
NIGHT. WHILE THE DURATION OF FORCING MAY BE FAIRLY PROLONGED FROM
EARLY EVENING INTO LATE SUN NIGHT...ASCENT /ESPECIALLY FROM A
SYSTEM RELATIVE STANDPOINT/ IS FORECAST TO BE RATHER WEAK. THE
BETTER LIFT ALSO LOOKS TO REMAIN OVER NORTHERN LOWER MI. A STABLE
PROFILE IN THE MID LEVELS WILL ALSO TEMPER THE DEGREE OF VERTICAL
LIFT. PERHAPS THE BIGGEST LIMITING FACTOR IS POOR MOISTURE QUALITY.
THE DEEP MOISTURE PLUME NOW EXTENDING ACROSS ERN TX IS FORECAST TO
SHIFT WELL EAST OF THE AREA ON SUNDAY. WHILE THE VEERING OF THE LOW
LEVEL FLOW SUN NIGHT WILL ADVECT A LITTLE BETTER LOW LEVEL MOISTURE
INTO SE MI...THE DEGREE OF DRY AIR NOW BLANKETING THE ERN GREAT
LAKES AND UPPER OH VALLEY RAISES CONCERNS THAT MODEL SOLUTIONS MAY
BE TOO AGRESSIVE IN MOISTENING THE LOW LEVELS SUN NIGHT. GIVEN THE
00Z GUIDANCE...THE FORCING SHOULD SUSTAIN ENOUGH MID LEVEL MOISTURE
TO GENERATE SOME LIGHT SNOW ACCUMS /AN INCH OR LESS/ NORTH OF THE
I-69 CORRIDOR SUN NIGHT. FARTHER SOUTH...MUCH LESS IF ANY SNOW IS
EXPECTED AT THIS TIME.

AFTER A SLIGHT WARMING TREND SUN NIGHT INTO MONDAY...COLDER AIR WILL
FUNNEL BACK INTO THE REGION LATE MON INTO TUESDAY. THE MEDIUM RANGE
MODEL SUITE ARE IN STRONG AGREEMENT IN HOLDING THE POLAR VORTEX OVER
HUDSON BAY THROUGH LATE IN THE WORK WEEK BEFORE IT SHIFTS OFF TO ERN
CANADA. THIS WILL SUSTAIN AN ARCTIC AIRMASS OVER THE REGION. THE
MAIN FORECAST CONCERN THROUGH THE UPCOMING WEEK WILL BE TIMING OF
SHORT WAVES ROUNDING THE BASE OF THE POLAR VORTEX. THESE WAVES WILL
CROSS THE GREAT LAKES AND HAVE THE POTENTIAL TO ENHANCE LAKE EFFECT
SNOW SHOWERS...POSSIBLY LEADING TO SOME MINOR SNOW ACCUMS OVER
PORTIONS OF SE MI. THE LATEST MODEL SUITE SUGGEST A WAVE FORECAST TO
TRAVERSE SRN MI TUES NIGHT/WED WILL HAVE A LITTLE MORE BAROCLINICITY
WHICH WILL MAKE SOME MINOR SNOW ACCUMS MORE PROBABLE.

&&

.MARINE...

GUSTY WESTERLY WINDS WILL PERSIST OVER NORTHERN LAKE HURON THROUGH
THE EVENING DUE TO THE A SURFACE TROUGH OVER LAKE SUPERIOR AND
STRONG HIGH PRESSURE OVER THE UPPER MIDWEST. THIS HIGH WILL EXPAND
INTO THE REGION LATER TONIGHT INTO SUNDAY ALLOWING WINDS AND WAVES
TO DIMINISH. DEVELOPING LOW PRESSURE OVER THE PLAINS ON SUNDAY IS
FORECAST TO LIFT ACROSS NORTHERN LAKE HURON EARLY MONDAY MORNING.
ALTHOUGH THIS LOW WILL BE WEAK...GOOD OVER LAKE INSTABILITY WILL
CONTRIBUTE TO A MODEST INCREASE IN SE WINDS SUN NIGHT. THE PASSAGE
OF THE LOW TO THE NE ON MONDAY WILL CAUSE THE WINDS TO VEER TO THE
SOUTHWEST. PERIODIC WAVES OF LOW PRESSURE WILL TRAVERSE THE NORTHERN
GREAT LAKES NEXT WEEK. THIS COMBINED WITH A SECOND SURGE OF ARCTIC
AIR WILL KEEP RATHER GUSTY WINDS OVER THE LAKES FOR SEVERAL DAYS.

&&

.AVIATION...ISSUED 1228 PM EST SAT DEC 7 2013

//DISCUSSION...

VFR CONDITIONS EXPECTED THROUGH THE TAF CYCLE AS DRY ARCTIC AIRMASS
DRIFTS ACROSS THE REGION. MBS/FNT HAVE A CHANCE OF MVFR CIGS FOR THE
NEXT HOUR OR TWO AS CURRENT SATELLITE TRENDS SHOW THE LAKE EFFECT
CLOUDS STILL HOLDING ON...BUT SCATTERING OUT. SKIES WILL CLEAR
TONIGHT BUT WILL GRADUALLY FILL BACK IN ON SUNDAY AS THE NEXT SYSTEM
APPROACHES. NON VFR CONDITIONS AND POTENTIAL PRECIP LOOK TO HOLD OFF
TIL AFTER THIS TAF CYCLE. CURRENTLY THERE ARE A FEW GUSTS AROUND 15
KNOTS BUT VERY SPORADIC/ISOLATED AND WILL LEAVE OUT OF THE TAFS.

//DTW THRESHOLD THREATS...

* NONE.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.

&&

$$

SHORT TERM...DRK
LONG TERM....SC
MARINE.......SC
AVIATION.....DRK


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