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000
FXUS63 KDTX 030809
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
309 AM EST TUE DEC 3 2013

.SHORT TERM...TODAY AND TONIGHT

WARM FRONT WILL SLOWLY LIFT INTO THE AREA TODAY AND PROGRESS NORTH
OF THE AREA WITH TIME TONIGHT. INITIAL BAND OF PRECIPITATION...WHICH
COINCIDES WITH THE FAR SOUTHEAST EXTENSION OF A DECENT AREA OF FGEN
FORCING...WITH MOVE INTO THE SOUTHERN CWA EARLY THIS MORNING. DTX
00Z SOUNDING SUPPORTS MODEL FORECAST OF THIS PRECIPITATION BEGINNING
AS LIGHT SNOW/FLURRIES AS IT WORKS THROUGH THE AREA THIS MORNING.
GIVEN THE INITIAL FIGHT WITH A POCKET OF DRY AIR FROM H85 TO THE SFC
AND A RATHER RAPID WARMING OF THE BOUNDARY LAYER AFTER 12Z...SNOW
AMOUNTS WILL BE INSIGNIFICANT...GENERALLY A TRACE TO NEAR ONE HALF
AN INCH. THE NORTHERN SAGINAW VALLEY WILL MOST LIKELY RECEIVE THE
HIGHEST SNOW ACCUMULATIONS...PERHAPS APPROACHING AN INCH...AS THE
AREA WILL REMAIN COLDEST LONGER INTO THE MORNING AND ALSO BENEFIT
FROM THE BEST FGEN FORCING FOR OUR IMMEDIATE AREA. AS THE WARM FRONT
CONTINUES NORTH TONIGHT...LINGERING SHOWERS...MAINLY OVER NORTHERN
CWA...WILL SHIFT INTO NORTH LOWER MICHIGAN/NORTHERN GREAT LAKES WITH
JUST A SLIGHT CHANCE OF RAIN SHOWERS OR DRIZZLE EXPECTED AFTER
MIDNIGHT AS DEEPER MOISTURE SHIFTS NORTH OF THE AREA.

TEMPERATURES WILL WARM INTO THE UPPER 30S NORTH TO MIDDLE 40S SOUTH
TODAY AND REMAIN MILD TONIGHT AS WARMER AIR CONTINUES TO EDGE NORTH
THROUGH THE AREA. IN GENERAL...TEMPERATURES WILL ONLY DROP SEVERAL
DEGREES FROM AFTERNOON HIGHS...RANGING IN THE MID 30S TO LOWER 40S.

&&

.LONG TERM...

CYCLOGENESIS WILL GET UNDERWAY TODAY & TONIGHT AS THE PV ANOMALY
ASSOCIATED WITH THE PACIFIC NORTHWEST LOW DIGS SOUTH AND EJECTS
NORTHEAST IN THE WEDNESDAY-THURSDAY PERIOD. THE RESULTANT SURFACE
LOW IS STILL FORECAST TO LIFT FROM THE TEXAS PANHANDLE LATE TONIGHT
TO JAMES BAY BY THURSDAY AFTERNOON THEREBY ENSURING THAT SOUTHEAST
MICHIGAN REMAINS ENTRENCHED IN THE CYCLONE`S WARM SECTOR.

OVERALL, THERE HAS BEEN LITTLE CHANGE IN THINKING FROM PRIOR
FORECASTS. WITH THE PASSAGE OF THE INITIAL WARM FRONT DURING THE
SHORT TERM PERIOD, THE FIRST HALF OF WEDNESDAY IS STILL FORECAST TO
BE DRY. THE 00Z SUITE OF GUIDANCE IS THEN IN SOLID AGREEMENT THAT
THE LOW-LEVEL RESPONSE TO THE DEEPENING LOW WILL INCLUDE A RAMPING
UP OF THE LOW-LEVEL JET AFTER ABOUT 21Z WEDNESDAY. THE ACCOMPANYING
THETA-E SURGE WILL TAKE PLACE PREDOMINANTLY IN THE SFC-925MB LAYER
AND WILL FOSTER ANOTHER ROUND OF RAIN SHOWERS WEDNESDAY AFTERNOON
THROUGH EARLY WEDNESDAY NIGHT. IT IS WORTH NOTING THAT SIGNIFICANT
ENTRAINMENT OF MID-LEVEL DRY AIR ORIGINATING OVER THE SOUTHWEST U.S.
AS WELL AS THE SUBSIDENCE ZONE OF THE EAST PACIFIC RIDGE MAY RESULT
IN AN EVENTUAL TRANSITION TO DRIZZLE DURING WEDNESDAY EVENING THAT
COULD FEASIBLY LAST UNTIL COLD FRONTAL PASSAGE. FROPA SHOULD BE
LARGELY UNEVENTFUL WITH NOTHING MORE THAN DISORGANIZED SHOWER
ACTIVITY GIVEN THE COMPLETE VOID OF A FRONTAL CIRCULATION OF ANY
RESPECTABLE DEPTH, ONLY MODEST BACKGROUND HEIGHT FALLS IN OUR
NEIGHBORHOOD, AND A NON-DESCRIPT/NEUTRAL PATTERN OF FORCING AT JET
LEVEL. JUDGING FROM PLANVIEWS OF CROSS-STREAM/AGEOSTROPHIC FLOW,
UPPER DIVERGENCE WILL BE FOCUSED WELL NORTH OF THE AREA AND
CONCENTRATED IN THE LEFT EXIT REGION OF THE MORE DOMINANT JET TO OUR
NORTHWEST.

AFTER HIGHS IN THE 50S & LOWS IN THE 40S WED & WED NIGHT IN ADVANCE
OF THE FRONT, COLDER AIR WILL BUILD BACK INTO SE MICHIGAN DURING THE
REMAINDER OF THE WEEK. COLD ADVECTION WILL BE ON THE WEAK SIDE,
HOWEVER, AS THE LONGWAVE TROUGH IS PROGGED TO UNDERGO SIGNIFICANT
SHEARING RESULTING IN A NEAR HALTING OF THE PROGRESS OF THE
LOW-LEVEL BAROCLINIC ZONE. AS A RESULT, H85 TEMPERATURES WILL FALL
ALL OF 10 DEGREES C DURING THE 48 HOURS FOLLOWING THE PASSAGE OF THE
FRONT AT 850MB. HIGH TEMPERATURES IN THE LOW-MID 40S ON THURSDAY
WILL EVENTUALLY GIVE WAY TO HIGHS IN THE LOW-MID 20S BY SATURDAY.

IN THE MEANTIME, A COUPLE OF LOW AMPLITUDE WAVES EMBEDDED IN THE
DEVELOPING DEEP LAYER SW FLOW WILL RIPPLE ALONG THE NEARLY STALLED
FRONTAL ZONE BRINGING A COUPLE ROUNDS OF SNOW TO OUR SOUTHEAST. THE
AREA MAY BE GRAZED BY THE NORTHERN FRINGE OF THE ASSOCIATED MOISTURE
SHIELD ON THURSDAY NIGHT, BUT NOTHING MORE THAN A FEW TENTHS IS
EXPECTED...MAINLY SOUTH OF THE METRO AREA.

&&

.MARINE...

STRENGTHENING LOW PRESSURE WILL LIFT INTO THE NORTHERN GREAT LAKES
WEDNESDAY INTO WEDNESDAY NIGHT. THIS WILL SUPPORT THE DEVELOPMENT OF
A FRESH SOUTHEAST BREEZE TONIGHT THROUGH WEDNESDAY NIGHT...WHEN
WINDS ARE EXPECTED TO TURN MORE SOUTHERLY. STABLE CONDITIONS ACROSS
THE WATERS WILL PREVENT MUCH IN THE WAY OF GUSTS. WESTERLY GUSTS TO
NEAR GALES ARE THEN EXPECTED ACROSS THE NORTHERN HALF OF LAKE HURON
ON THURSDAY AFTERNOON AS COLDER AIR SPREADS ACROSS THE LAKES. GUSTS
WILL REMAIN AROUND 25 KNOTS FURTHER SOUTH.

&&

.AVIATION...ISSUED 1202 AM EST TUE DEC 3 2013

//DISCUSSION...

AREA OF LIGHT PRECIPITATION ANCHORED ON A WARM FRONTAL BOUNDARY WILL
CONTINUE TO EASTWARD AND INTO SOUTHEAST MICHIGAN DURING THE MID AND
LATE MORNING HOURS.  INCREASING CONFIDENCE BACKED BY RECENT
OBSERVATIONS AND RADAR TRENDS UPSTREAM WILL SUPPORT A MORE
DEFINITIVE MENTION OF A PERIOD OF LIGHT SNOW IN MVFR AT ALL
TERMINALS...FILLING IN FROM SOUTHWEST TO NORTHEAST WITHIN THE 10-13Z
TIME WINDOW.  LIMITED DURATION AND GENERALLY LIGHT INTENSITY WILL
CONFINE ACCUMULATION POTENTIAL AT LESS THAN HALF AN INCH.  A WARMING
LOW LEVEL ENVIRONMENT WILL TEND TO CHANGE ANY LINGERING POCKETS OF
LIGHT PRECIPITATION TO RAIN ACROSS THE NORTHERN TAF SITES BY EARLY
AFTERNOON.  A MOIST EAST-SOUTHEAST FLOW WILL SUSTAIN AN EXTENSIVE
LOW STRATUS DECK THROUGH THE REMAINDER OF THE PERIOD.

FOR DTW...EASTWARD EXTRAPOLATION OF THE INBOUND AREA OF LIGHT
PRECIPITATION ALLOWS LIGHT SNOW TO DEVELOP AS EARLY AS 10Z.
GREATEST WINDOW FOR LIGHT SNOWFALL WILL BE 11Z-14Z...A DUSTING TO
LESS THAN HALF AN INCH POSSIBLE.  BRIEF TRANSITION TO LIGHT RAIN
BEFORE ENDING AS THE WARM LAYER ARRIVES 15-16Z...THEN LINGERING MVFR
STRATUS/BR FOR THE REMAINDER OF THE DAY.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CIGS AOB 5000 FEET AFTER 09Z THIS MORNING.

* HIGH CONFIDENCE IN SNOW AS PRECIPITATION TYPE 10-14Z THIS MORNING.

&&

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

&&

$$

SHORT TERM...DG
LONG TERM....JVC
MARINE.......JVC
AVIATION.....DG


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