Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 260320
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1020 PM EST TUE NOV 25 2014

.UPDATE...

EVENING SURFACE ANALYSIS HAS A RIDGE OF HIGH PRESSURE RUNNING FROM
THE WESTERN GREAT LAKES INTO THE LOWER OHIO VALLEY AND POINTS
SOUTH. SATELLITE IMAGERY SHOWS A SOLID DECK OF STRATUS TRAPPED
ALONG AND EAST OF THE RIDGE AXIS OVER ALL OF LOWER MICHIGAN
AUGMENTED BY LIGHT BUT COLD WESTERLY FLOW OVER LAKE MICHIGAN. THE
DTX 00Z SOUNDING IS REPRESENTATIVE OF OTHERS AROUND THE REGION
THAT DEPICT A SHARP INVERSION DUCTING BOUNDARY LAYER MOISTURE WITH
ENOUGH DEPTH TO ENSURE PERSISTENCE WITH THE LOSS OF SURFACE
HEATING. SATELLITE TRENDS AND MODEL DEPICTIONS OF A SLOW EASTWARD
PACE ON THE SURFACE HIGH SUGGEST COVERAGE WILL LINGER THROUGH MUCH
OF WEDNESDAY MORNING. THE EVENING UPDATE REFLECTS THIS TREND ALONG
WITH AN UPWARD NUDGE ON MIN TEMPS THAT SHOULD SETTLE INTO THE MID
20S BY SUNRISE.

&&

.AVIATION...ISSUED 653 PM EST TUE NOV 25 2014

//DISCUSSION...

SURFACE OBSERVATIONS FROM LATE AFTERNOON INTO EARLY EVENING INDICATE
MVFR STRATUS LOCKED WITHIN THE RIDGE OF SURFACE HIGH PRESSURE FROM
THE WESTERN GREAT LAKES INTO THE OHIO VALLEY. CONSIDERING THE LACK
OF DIURNAL DISSIPATION OF THESE CLOUDS UPSTREAM OF THE LAKES...
EXPECT A SLOWER CLEARING TREND OVER LOWER MICHIGAN DURING THE NIGHT.
IT MAY TAKE UNTIL THE SURFACE RIDGE MOVES NORTH OF THE REGION TO
SCOUR OUT THE LOW CLOUDS THROUGH THE TERMINAL CORRIDOR. INCREASED
EASTERLY LOW LEVEL WIND DURING WEDNESDAY MORNING WILL MARK THE
TRANSITION WITH A SHORT FETCH OVER LAKES HURON AND ERIE PRODUCING
MINIMAL ADDITIONAL CLOUD MOISTURE. THE SURFACE PRESSURE PATTERN WILL
THE REMAIN FLAT DURING WEDNESDAY...BETWEEN DEPARTING HIGH PRESSURE
AND THE NEXT WEAK LOW PRESSURE SYSTEM ENTERING THE MIDWEST. EXPECT
VFR CONDITIONS AND LIGHT WIND TO PERSIST INTO WEDNESDAY NIGHT.

//DTW THRESHOLD THREATS...

* HIGH PROBABILITY THAT CEILINGS WILL REMAIN BELOW 5000 FT THROUGH
  TONIGHT.

&&

.PREV DISCUSSION...ISSUED 344 PM EST TUE NOV 25 2014

SHORT TERM...TONIGHT

SNOW SHOWERS THAT HAVE BEEN PRESENT ACROSS MUCH OF THE NORTHERN CWA
WILL SLOWLY DIMINISH TOWARDS NIGHTFALL. STRONG SOUTHWESTERLY WINDS
HAVE ALLOWED LAKE EFFECT BANDS OFF OF LAKE MICHIGAN TO MAKE THEIR
WAY INTO THE SAGINAW VALLEY AND I-69 CORRIDOR FOR MUCH OF THE
AFTERNOON. CURRENT MODEL TRENDS SHOW WEAK MID LEVEL RIDGING TO TAKE
PLACE AFTER 00Z RESULTING IN SURFACE HIGH PRESSURE TO BUILD ACROSS
THE GREAT LAKES REGION TONIGHT. THIS HIGH WILL ALLOW WINDS TO
DIMINISH AND BECOME LIGHT AND VARIABLE OVERNIGHT CAUSING LAKE EFFECT
SNOW SHOWERS TO COME TO AN END. IN ADDITION...THE SOLID STRATUS DECK
OVER SOUTHEAST MICHIGAN WILL BECOME MORE BROKEN OVERNIGHT AS MID
LEVEL DRY AIR FILTERS IN TO THE REGION. LIGHT WINDS AND SOME
CLEARING WILL ALLOW TEMPERATURES TO DROP INTO THE LOW TO MID 20S
ACROSS SOUTHEAST MICHIGAN.

LONG TERM...

UPPER TROUGH WILL ROTATE THROUGH THE GREAT LAKES ON WEDNESDAY
THROUGH THURSDAY WITH A FAST-MOVING EDGEWAVE DIGGING INTO THE OHIO
VALLEY EARLY ON WEDNESDAY. WITH THE BULK OF FORCING IN THE REGION
TIED TO THIS WAVE AND THE NORTHERN BRANCH TROUGH AXIS STILL WELL
UPSTREAM, SE MICHIGAN WILL BE LEFT IN A RATHER BENIGN ZONE ON
WEDNESDAY CHARACTERIZED BY A NONDESCRIPT SURFACE PRESSURE PATTERN.
LITTLE AIRMASS MODIFICATION FROM TODAY WILL PRODUCE SIMILAR HIGH
TEMPERATURES UNDER CLOUDY CONDITIONS, THOUGH SURFACE WINDS WILL BE 5
KNOTS OR LESS. 12Z NAM SOUNDINGS SUGGEST A SUFFICIENTLY DEEP LAYER
OF BOUNDARY LAYER MOISTURE TO MOVE FORWARD WITH THE INHERITED MOSTLY
CLOUDY FORECAST. A FEW FLURRIES MAY BE POSSIBLE DURING PEAK HEATING
GIVEN MARGINALLY FAVORABLE THERMODYNAMIC PROFILE.

NORTHERN TROUGH WILL APPROACH WED NIGHT INTO THURSDAY WITH CLOUD
COVER AND DECENTLY MIXED CONDITIONS EXPECTED TO LIMIT THURSDAY
MORNING`S LOWS TO THE MID 20S. CROSS-SECTIONS ON THURSDAY REVEAL
VERY HIGH STATIC STABILITY ABOVE 700MB. THIS WILL SIGNIFICANTLY
DAMPEN OR ALTOGETHER ELIMINATE THE VERTICAL RESPONSE TO THE WAVE IN
THE MID-LEVELS. HOWEVER, CONVERGENCE ALONG THE COLD FRONT DOES LOOK
PRETTY SOLID. COMBINED WITH A QUICK HITTING SHOT OF SR ISENTROPIC
ASCENT ON THE 275K SURFACE AND MODEST AUGMENTATION OF THE MOISTURE
FIELD FROM THE LAKE AGGREGATE, COULD SEE A LINE OF SNOW SHOWERS WORK
THROUGH DURING THE HOLIDAY BRINGING A DUSTING TO PERHAPS A HALF INCH
OF ACCUMS. STRONG DEPENDENCE ON SUB-700MB FORCING/DYNAMICS AND SHORT-
LIVED NATURE OF FORCING REALLY SUGGEST NOTHING MORE THAN A CHANCE
POP. ANTICYCLONIC FLOW WILL BUILD IN FOR THURSDAY NIGHT AS COLD HIGH
PRESSURE WORKS INTO THE AREA BEHIND THE FRONT. H85 TEMPERATURES WILL
FALL TO -13C SUPPORTING CURRENT FORECAST LOWS IN THE UPPER TEENS BY
FRIDAY MORNING.

ON FRIDAY...SPRAWLING LOW PRESSURE OVER THE UPPER MIDWEST WILL
BATTLE RETREATING HIGH PRESSURE OVER THE EASTERN SEABOARD. LOW
PRESSURE WILL WIN-OUT AS IT IS ACCOMPANIED BY A LATITUDINAL FLOW 115
KT JET. WITH THE ZONAL FLOW IN PLACE...A RECOVERY TO NEAR NORMAL
TEMPERATURES WILL ENSUE FOR THE WEEKEND. NEXT SURFACE FEATURE /HIGH
PRESSURE OVER NORTHERN CANADA/ WILL GET LITTLE UPPER AIR
SUPPORT...BUT NONETHELESS LOOKS TO BRING COLD TEMPS BACK TO THE
REGION EARLY NEXT WEEK. HAVE TRENDED THOSE GRIDS COOLER WITH
LITTLE CONFIDENCE IN SNOW CHANCES PAST DAY 4.

MARINE...

WINDS AND WAVES ARE EASING THIS AFTERNOON ALLOWING ALL GALE WARNINGS
TO EXPIRE. SMALL CRAFT ADVISORIES ALONG THE TIP OF THE THUMB HAVE
BEEN EXTENDED THROUGH EARLY THIS EVENING UNTIL SIGNIFICANT WAVE
HEIGHTS FALL BELOW THE 3 TO 5 FOOT THRESHOLD. A WEAK PRESSURE
GRADIENT WILL RESULT IN LIGHT WINDS TONIGHT THROUGH WEDNESDAY NIGHT.
A FAST MOVING LOW PRESSURE WILL THEN BRING A QUICK SHOT OF
NORTHWESTERLY GALES OR NEAR-GALES ON THURSDAY AFTERNOON WHICH SHOULD
BE NO MORE THAN 6 HOURS IN DURATION.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
&&

$$

UPDATE.......BT
AVIATION.....BT
SHORT TERM...RK
LONG TERM....JVC/MM
MARINE.......JVC


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



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