Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 231757
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1257 PM EST SUN NOV 23 2014

.AVIATION...

//DISCUSSION...

A BRIEF PERIOD OF LIGHT RAIN MAY HOLD TOGETHER AT MBS SHORTLY AFTER
18Z...BUT THE REST OF THE TERMINALS WILL BE DRY FOR THE BULK OF THE
AFTERNOON BEFORE A SURGE OF RAIN MOVES IN FROM THE OHIO VALLEY. THE
PATTERN OF RAIN...ALONG WITH THE SURFACE LOW AND WARM FRONT
DEVELOPING TOWARD THE SOUTH END OF LAKE MICHIGAN...WILL PRODUCE
IFR/LIFR CONDITIONS ACROSS ALL LOCATIONS DURING MID TO LATE EVENING.
SE WIND AVERAGING 15 KNOTS WILL MAKE IT DIFFICULT FOR LESS THAN IFR
VISIBILITY RESTRICTION BUT LIFR CEILING WILL BE A HIGH CONFIDENCE
FORECAST GIVEN THE MATURE WARM FRONT APPROACHING WITH THE PRIMARY
LOW PRESSURE CENTER. NORTHWEST TO SOUTHEAST POSITIONING OF THE FRONT
FAVORS SIMILAR ONSET TIMING THROUGH THE TERMINAL CORRIDOR FOLLOWED
BY A PROGRESSION OF THE WARM SECTOR MONDAY MORNING WITHIN A FEW
HOURS FROM SOUTH TO NORTH OVER THE REGION. THE EXCEPTION TO THIS MAY
BE WITH THE ONSET OF STRONG SOUTHWEST FLOW AT MBS WHERE THE SURFACE
FRONT/TROUGH WILL LINGER FOR A LONGER PERIOD THROUGH THE MORNING.
WARM SECTOR WIND GUSTS NEAR 30 KNOTS WILL LIKELY EXCEED 40 KNOTS
FROM THE SOUTHWEST UPON PASSAGE OF A STRONG COLD FRONT MONDAY
AFTERNOON.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CEILING BELOW 5000 FEET TONIGHT THROUGH
  MONDAY.

* HIGH CONFIDENCE IN RAIN AS PRECIPITATION TYPE

&&

.PREV DISCUSSION...ISSUED 1050 AM EST SUN NOV 23 2014

UPDATE...

A WEAK WING OF MID LEVEL ISENTROPIC ASCENT WILL RUN ITS COURSE
THROUGH THE LATE MORNING AND EARLY AFTERNOON IN FAVOR OF A BREAK
IN COVERAGE FOR A FEW HOURS DURING MID AFTERNOON. THE BREAK WILL
OCCUR WHILE THE NEXT MOISTURE SURGE QUICKLY RELOADS AND MOVES
NORTHWARD FROM THE TENNESSEE VALLEY. INCOMING MODEL DATA POINTS TO
THE BREAK FILLING IN RAPIDLY DURING LATE AFTERNOON INTO EARLY
EVENING AS THE CENTRAL GULF COAST UPPER LOW MOVES INTO WESTERN
KENTUCKY. THE LOW WILL BE PRECEDED BY A STRONG AND DEEP SURGE OF
GULF MOISTURE TRANSPORT SURFACE THROUGH 700 MB ENSURING RENEWED
WIDESPREAD COVERAGE OF RAIN SHOWERS TOWARD SUNSET THROUGH TONIGHT.
THE NEXT FORECAST UPDATE WILL REFLECT LESS COVERAGE OF SHOWERS
DURING THE FIRST HALF OF THE AFTERNOON BUT MAINTAIN A TREND TOWARD
CATEGORICAL PROBS LATE IN THE DAY.

PREV DISCUSSION...ISSUED 320 AM EST SUN NOV 23 2014

SHORT TERM... TODAY AND TONIGHT

COPIOUS AMOUNT OF UPPER LEVEL ENERGY/PV WORKING THROUGH THE ROCKIES
THIS MORNING. MOISTURE LADEN UPPER LEVEL WAVE OVER EASTERN TEXAS
ALREADY BECOMING ABSORBED/CAPTURED WITHIN THE STRENGTHENING
SOUTHWEST FLOW OVER THE CENTRAL CONUS. IMPRESSIVE 12 HR HEIGHT
FALL CENTER (-18 DAM) WILL MOVE OVER WESTERN OHIO VALLEY BY 12Z
MONDAY...SUPPORTING GOOD CYCLOGENESIS MOVING INTO THE CENTRAL
GREAT LAKES. THIS WILL ASSURE A SOAKING RAIN TONIGHT...WITH STRONG
LOW LEVEL JET/GOOD OVERRUNNING SET UP/LARGE SCALE ASCENT...AND 850
MB DEW PTS OF 7-8 C TO WORK WITH. RAINFALL TOTALS AROUND 1 INCH
WILL LIKELY BE COMMON. A QUICK LOOK AT 6 HR FLOOD GUIDANCE SHOWS 2
INCH THRESHOLDS...AND DO THINK THE GROUND WILL THAW OUT ENOUGH
TODAY TO BE ABLE TO HANDLE THIS RAINFALL...AND NOT PLANNING ON
ISSUING A FLOOD WATCH DESPITE THE 3+ STANDARD ANOMALY WITH RESPECT
TO PW VALES.

A MILD START TO THE DAY...AS TEMPERATURE ARE CURRENTLY IN THE MID
40S TO AROUND 50 DEGREES. HOWEVER...WITH THE SURFACE/NEAR SURFACE
WINDS BACKING OUT OF THE SOUTHEAST TODAY...WOULD NOT EXPECT MUCH
MORE OF A RISE (LOWER 50S)...WITH TEMPS HOVERING IN THE UPPER 40S
TO LOWER 50S TONIGHT WITH RENEWED SURGE OF WARM AIR ARRIVING.

LONG TERM... MONDAY THROUGH SATURDAY

DYNAMIC MID LEVEL WAVE LOCKED ONTO THE EXIT REGION OF AN ACTIVE
UPPER JET OF NORTH PACIFIC ORIGIN WILL QUICKLY LIFT INTO THE GREAT
LAKES ON MONDAY...IMMEDIATELY BEHIND THE LEAD SYSTEM WORKING THROUGH
TONIGHT.  SOME DEGREE OF INTERACTION BETWEEN THESE PV FEATURES AND
ATTENDANT UPPER JET COUPLING WILL RESULT IN A STEADY STRENGTHENING
OF THE ASSOCIATED SURFACE LOW TRACKING FROM SOUTHERN LAKE MICHIGAN
TO JUST NORTH OF THE STRAITS THROUGH MONDAY.  THERE REMAINS SOME
VARIABILITY YET WITHIN THE 00Z MODEL GUIDANCE IN TERMS OF BOTH THE
STRENGTH AND FORWARD MOMENTUM OF THE KEY LOW LEVEL FEATURES
HEADING INTO MONDAY. HOWEVER THE GUIDANCE ENVELOP CONTINUES TO
CONTRACT WITH EACH PROGRESSIVE MODEL CYCLE...LENDING INCREASING
CONFIDENCE IN THE DETAILS THROUGH THIS TIME.

BRIEF WINDOW OF DEEPER PRE-FRONTAL SOUTHWEST FLOW IN PLACE MONDAY
MORNING...TEMPERATURES LIKELY PEAKING IN THE LOWER 50S DURING THIS
TIME.  BRIEF SUBSIDENCE SUGGESTS A SMALL PAUSE IN SHOWER DEVELOPMENT
MID MORNING...BEFORE THE INBOUND MID LEVEL WAVE WORKS ACROSS LATE
MORNING/EARLY AFTERNOON.  STRONG SIGNAL OF FRONTAL CONVERGENCE
TUCKED BENEATH FAVORABLE UPPER JET DYNAMICS AND A PERIOD OF GOOD CVA
POINTS TO AN INCREASE IN SHOWER COVERAGE THROUGH THIS TIME.
DIMINISHING STABILITY THROUGH THE COLUMN COULD YIELD A FEW RUMBLES
OF THUNDER AS WELL.  MAIN FORECAST ELEMENT OF INTEREST REMAINS THE
WIND POTENTIAL AS STRONG COLD AIR ADVECTION ENSUES FROM MID
AFTERNOON INTO THE EVENING HOURS.  STRONG POST-FRONTAL SOUTHWEST
GRADIENT TAKES HOLD DURING THIS TIME...SUSTAINED SPEEDS INCREASING
INTO THE 25 MPH RANGE. GUST POTENTIAL WILL CAPITALIZE ON A PERIOD
OF STRONG 280-285K ISENTROPIC DESCENT AND AT LEAST WEAK MIXING
POTENTIAL AS LAPSE RATES STEEPEN WITH THE ADVECTIVE PROCESS.
RECENT GUIDANCE MAINTAINS WIND SPEEDS IN THE 40 KNOT RANGE AT 925
MB. THIS WOULD INDICATE GUSTS CLOSE TO OR AT A LOW END ADVISORY
/40 TO 45 MPH/...GREATEST GUSTS CENTERED 21Z-02Z.

AGGRESSIVE COLD AIR ADVECTION BRINGS TEMPERATURES BACK INTO THE 30S
BY EARLY EVENING...A PLUMMETING FREEZING LEVEL REINTRODUCING THE
POTENTIAL FOR SNOW SHOWERS TO MIX IN DURING THIS TIME.  MODEST LAKE
MICHIGAN RESPONSE INITIALLY /LAKE INDUCED EQUILIBRIUM LEVELS BELOW
5000 FT/ WITH THE STRENGTH OF THE WIND FIELD LIKELY CONTRIBUTING TO
A LACK OF BETTER DOWNSTREAM ORGANIZATION.  THE MAIN SHORTWAVE
ANCHORING THE PRIMARY HEIGHT FALL AXIS WILL SETTLE THROUGH
OVERNIGHT...WHICH MAY HELP AUGMENT THE MOISTURE FLUX IN GENERATING
SOME LIGHT SHOWERS WITH MINOR ACCUMULATION. LOW TEMPERATURES
BOTTOM OUT WITHIN THE 25 TO 30 DEGREE RANGE.

EXTENDED STRETCH OF BELOW NORMAL TEMPERATURES STARTING TUESDAY...
LINGERING LOW LEVEL THERMAL TROUGH /-12C AT 850 MB/ AND PLENTY OF
CLOUD COVER ENSURING HIGHS ARRIVE WITHIN A COUPLE DEGREE OF
FREEZING.  LOW LEVEL FLOW VEERS TO A WESTERLY COMPONENT DURING THE
DAY...A MORE FAVORABLE TRAJECTORY FOR GREATER DOWNSTREAM ADVANCEMENT
OF THE LAKE MICHIGAN MOISTURE PLUME AND SOME LOCALIZED CONVERGENCE.
THIS WILL MAINTAIN A CHANCE FOR SNOW SHOWERS THROUGH THE DIURNAL
HEATING CYCLE.

DRY AND COLD INTO WEDNESDAY UNDER LOWER AMPLITUDE RIDGING.  CLIPPER
SYSTEM ON TRACK TO LIFT ACROSS THE GREAT LAKES WEDNESDAY NIGHT AND
EARLY THURSDAY.  MODEST MOISTURE RECOVERY IMMEDIATELY IN ADVANCE OF
THIS SYSTEM WOULD SUPPORT A LIGHT ACCUMULATING SNOWFALL AS THE
COMPACT MID LEVEL DYNAMICS SWEEP ACROSS DURING THIS TIME. DAYTIME
HIGHS IN THE LOWER 30S BOTH WEDNESDAY AND THURSDAY.

MARINE...

MODERATE SOUTHERLY WINDS WILL REMAIN IN PLACE TODAY AND TONIGHT AS
STRENGTHENING LOW PRESSURE LIFTS INTO THE GREAT LAKES.  THE ARRIVAL
OF WARMER AIR IN ADVANCE OF THIS SYSTEM WILL CONTAIN THE GUST
POTENTIAL...WITH WINDS GENERALLY AT 15 TO 25 KNOTS THROUGH THIS
PERIOD.

THE LOW PRESSURE SYSTEM WILL LIFT ACROSS THE WESTERN AND NORTHERN
GREAT LAKES THROUGH MONDAY...SENDING A STRONG COLD FRONT ACROSS THE
AREA MONDAY AFTERNOON. GALE FORCE WINDS LOOK LIKELY BEHIND THE COLD
FRONT MONDAY AND MONDAY NIGHT AS A TIGHT PRESSURE GRADIENT DEVELOPS
AND MUCH COLDER AIR RUSHES INTO THE AREA...WITH GUSTS POTENTIAL IN
EXCESS OF 45 KNOTS.  THERE IS STILL SOME UNCERTAINTY WITH HOW MUCH
THIS SYSTEM WILL DEEPEN AND THE EXACT TRACK IT WILL TAKE ACROSS THE
GREAT LAKES. FURTHER ADJUSTMENT TO THE FORECAST IS POSSIBLE. IF THE
SYSTEM DEEPENS FURTHER THAN CURRENTLY ANTICIPATED...STORM FORCE WIND
GUSTS COULD DEVELOP OVER PORTIONS OF LAKE HURON. THOSE WITH
INTERESTS IN THE GREAT LAKES MONDAY AND MONDAY NIGHT SHOULD FOLLOW
CHANGES IN THE FORECAST CLOSELY. A STORM WATCH IS NOW IN EFFECT FOR
CENTRAL LAKE HURON...WHILE A GALE WATCH REMAINS IN EFFECT MONDAY AND
MONDAY NIGHT FOR ALL OTHER MARINE AREAS.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...NONE.

LAKE HURON...GALE WATCH FROM MONDAY MORNING THROUGH TUESDAY MORNING FOR LHZ361-
     421-422-441>443-462>464.

     STORM WATCH FROM MONDAY MORNING THROUGH TUESDAY MORNING FOR LHZ362-
     363.

LAKE ST CLAIR...GALE WATCH FROM MONDAY MORNING THROUGH TUESDAY MORNING FOR LCZ460.

MICHIGAN WATERS OF LAKE ERIE...GALE WATCH FROM MONDAY MORNING THROUGH TUESDAY MORNING FOR LEZ444.

&&

$$

AVIATION.....BT
UPDATE.......BT
SHORT TERM...SF
LONG TERM....MR
MARINE.......MR


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AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).


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