Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 141711
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1211 PM EST SUN DEC 14 2014


.AVIATION...

//DISCUSSION...

A SATURATED NEAR SURFACE LAYER CONTINUES TO PLAGUE THE TAF SITES
TODAY AS AN UPPER LEVEL RIDGE KEEPS AN INVERSION AND THIS LOW LEVEL
MOISTURE IN PLACE. CIGS THIS AFTERNOON RANGE FROM IFR ACROSS THE
NORTH...TO MVFR ACROSS THE SOUTH WITH PERIODS OF LIGHT DRIZZLE
REDUCING VSBYS TO IFR AT TIMES WITH A PREDOMINENT MVFR. THE
DEVELOPMENT OF A MODEST WARM FRONT THIS AFTERNOON WILL EVENTUALLY
LEAD TO A GREATER POTENTIAL FOR DRIZZLE PRIOR TO AND JUST AFTER
SUNSET. LOSS OF SURFACE WINDS TONIGHT WITH INCREASED NEAR SURFACE
MOISTURE BRINGS A HIGH POTENTIAL FOR FOG. SLIGHTLY LESS CONFIDENT
THAT WIDESPREAD DENSE FOG WILL DEVELOP...BUT
NEVERTHELESS...CONFIDENCE IS INCREASING. CURRENT INDICATIONS ARE FOG
MONDAY MORNING COULD LINGER INTO THE MID MORNING
HOURS...APPROXIMATELY 15Z.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CEILINGS BELOW 5000 FEET THROUGH THE TAF PERIOD.

* MEDIUM TO HIGH CONFIDENCE CIGS AT 200 FEET AND/OR VSBYS AOB 1/2SM
  BY 02Z THIS EVENING.

&&

.PREV DISCUSSION...ISSUED 358 AM EST SUN DEC 14 2014

SHORT TERM...TODAY AND TONIGHT

A FEW FACTORS WILL WORK IN TANDEM TODAY TO ALLOW THE MASSIVE NORTH
AMERICAN OMEGA BLOCK TO BEGIN AN EASTWARD MIGRATION. WHILE A
BREAKDOWN OF THE PATTERN WILL BE SLOW TO EVOLVE...THE UPPER LEVEL
RIDGE AXIS IS FORECASTED TO PUSH INTO LOWER MICHIGAN BY THE
AFTERNOON HOURS. THIS WILL NOT HAVE A HUGE IMPACT ON THE WEATHER
TODAY...RATHER...THE AREA IS LARGELY LOOKING AT ANOTHER DAY OF
PERSISTENCE. THE MOST NOTABLE CONSEQUENCE OF THIS FEATURE
TRACKING CLOSER...IS AN ORGANIZATION AND FOCUS OF LEAD WING LOW
LEVEL DEFORMATION OVER THE CWA BY LATE THIS AFTERNOON AND EARLY
EVENING.

THE SUBTLE FORCING ALONG WITH MOISTURE POOLING ALONG THE DEVELOPING
WARM FRONT IS EXPECTED TO LEAD TO INCREASED MOISTURE
DEPTHS...PROGGED TO DOUBLE TO APPROXIMATELY 4000 FT DEEP BY THE
EARLY EVENING HOURS. HAVE INCLUDED A LOW CHANCE POP BEGINNING LATE
THIS AFTERNOON...WORKING NORTHWARD TO THE NORTHERN CWA BY LATE
TONIGHT. OVERALL STRENGTH OF THE STABILITY IN THIS SETUP SUPPORTS
MORE DRIZZLE THAN RAIN SHOWERS...WITH THE HIGH END OF LIQUID AMOUNTS
AT .01 TO .02 INCHES. NOTHING TO REALLY HIGHLIGHT.

WITH THE WARM FRONT DEVELOPING AND LIFTING NORTHWARD
TONIGHT...PRESSURE GRADIENT OVER THE REGION WILL SLACKEN AND
GRADIENT FLOW WILL FALL OFF. NOT EXPECTING SURFACE WINDS TONIGHT
ANYTHING CLOSE TO THE 10 TO 20 KNOTS SEEN THIS MORNING. INCREASING
NEAR SURFACE THETA E WITH A BENIGN WIND FIELD WILL BRING FOG BACK
INTO PLAY. MOS IS EXTREMELY BULLISH ALONG WITH THE FORECASTED NEAR
SURFACE TEMPERATURE/MOISTURE PROFILE. WITH SURFACE OBSERVATIONS
UPSTREAM REPORTING DENSE FOG THIS MORNING...THE FORECAST CONCERN FOR
TONIGHT WILL BE THE POSSIBILITY FOR A HEADLINE.

LONG TERM...

CONTINUED MILD TEMPERATURES WILL BE THE MAIN STORY TO START THE
WEEK. MONDAY AFTERNOON HIGH TEMPS WILL MAKE A RUN AT 50 OVER ALL OF
SE MICHIGAN AND EVEN INTO THE LOWER 50S TOWARD THE OHIO BORDER.
AFTER LINGERING FOG AND DRIZZLE DURING THE MORNING...LOW LEVEL MODEL
RH FIELDS AND FORECAST SOUNDINGS SHOW A TREND TOWARD LESS BOUNDARY
LAYER SATURATION IN SOUTHERLY FLOW DURING THE AFTERNOON. THIS
SUGGESTS DRIZZLE WILL BECOME LESS OF A FACTOR IN FIGHTING BACK
DAYTIME WARMING WITH A FEW BREAKS IN THE CLOUDS ALSO POSSIBLE. GIVEN
UPSTREAM OBSERVATIONS...MAX TEMPS MONDAY ARE NUDGED UPWARD TO FAVOR
THE WARMEST GUIDANCE...AND MIN TEMPS MONDAY NIGHT WILL REMAIN IN THE
40S ACROSS THE REGION.

THE SYSTEM OVER THE SOUTHERN PLAINS TODAY IS ON TRACK TO LIFT TOWARD
THE GREAT LAKES DURING MONDAY TO A LOCATION NEAR THE SOUTH END OF
LAKE MICHIGAN BY SUNRISE TUESDAY. THIS TIMING IS SIMILAR TO THE LAST
FEW MODEL CYCLES OR PERHAPS JUST SLIGHTLY SLOWER. THE SYSTEM REMAINS
SUBJECT TO AN EASTWARD KICK BY THE NORTHERN STREAM UPPER TROUGH OVER
CENTRAL CANADA RATHER THAN PHASING AS 500 MB HEIGHT FALL CENTERS OF
THE TWO FEATURES REMAIN ADEQUATELY SEPARATED. THE DOWNSTREAM LONG
WAVE RIDGE WILL ALSO PRESENT LESS INTERFERENCE FOR AN EASTWARD TRACK
AS IT DRIFTS FARTHER OFF THE ATLANTIC COAST DURING THIS TIME. THE
00Z GFS IS THE LONE HOLDOUT ON A MORE EASTWARD TRACK OF THE SURFACE
LOW DURING TUESDAY. THE GOOD NEWS HERE IS THAT EVEN THE EASTWARD
TRACK STILL PRESENTS AN ALL RAIN SCENARIO FOR SE MICHIGAN UNTIL
COLDER AIR CHASES THE TRAILING EDGE OF THE PRECIPITATION SHIELD OUT
OF THE AREA TUESDAY NIGHT. MILD AIR CAPABLE OF ANOTHER ROUND OF MAX
TEMPS IN THE LOWER 50S WILL BE IN PLACE FOR THE START OF THE
PRECIPITATION EPISODE WHICH WILL BEGIN WITH A LEADING SURGE OF MID
LEVEL THETA-E ADVECTION BY TUESDAY EVENING. CURRENT SATELLITE
PRESENTATION SUPPORTS MODEL DEPICTIONS OF A STRONGLY DYNAMIC UPPER
LEVEL CIRCULATION THEN SPREADING OVER LOWER MICHIGAN TO WRING
MOISTURE OUT OF THE LOW TO MID LEVEL TROWAL AXIS AND PROVIDE SOME
COLD POOL INSTABILITY ALOFT. THESE INGREDIENTS ARE WORTHY OF HIGH
END LIKELY POPS FOR GENEROUS COVERAGE OF SHOWERS IN A RICH MOISTURE
ENVIRONMENT FOR THIS TIME OF YEAR.

COLDER AIR WILL ARRIVE CLOSE ON THE HEELS OF THE MOISTURE PATTERN
THAT WILL SHEAR QUICKLY OFF TO THE EAST WITH THE UPPER WAVE BY
WEDNESDAY MORNING. A BRIEF MIX OR CHANGE OVER TO SNOW HAS THE BEST
CHANCE IN THE SAGINAW VALLEY AND NORTHERN THUMB BEFORE THE MID LEVEL
DRY SLOT PLUNGES OVER SOUTHERN LOWER MICHIGAN DURING THE REST OF
WEDNESDAY. THE ASSOCIATED SUBSIDENCE COMBINED WITH 850 MB TEMPS ONLY
IN THE NEGATIVE SINGLE DIGITS POINTS TO A MINIMAL RESPONSE FROM LAKE
MICHIGAN AS THE CENTRAL CANADIAN UPPER WAVE TRAVERSES THE GREAT
LAKES THROUGH WEDNESDAY NIGHT.

REDEVELOPMENT OF A HIGH AMPLITUDE UPPER LEVEL RIDGE OVER THE CENTRAL
STATES DURING THE END OF THE WEEK REMAINS A FAVORED SOLUTION AMONG
THE GLOBAL MODEL OFFERINGS. THIS IS BASED ON THE RECENT HISTORY OF
BLOCKING CHARACTER IN THE NORTHERN STREAM COMBINED WITH A HIGH
ENERGY SOUTHERN STREAM PATTERN THAT COULD BRING THE NEXT LOW
PRESSURE SYSTEM INTO THE GREAT LAKES BY NEXT WEEKEND.

MARINE...

MILD AND MOIST AIR WILL CONTINUE TO STREAM INTO THE CENTRAL GREAT
LAKES TODAY THROUGH TUESDAY. THE LIGHT WIND AND INCREASED STABILITY
OVER THE WATER WILL RESULT IN FAVORABLE WAVE CONDITIONS UNTIL THE
NEXT LOW PRESSURE SYSTEM SLIDES THROUGH THE SOUTHERN GREAT LAKES
TUESDAY. THIS SYSTEM WILL BRING RAIN TO THE AREA FOLLOWED BY COLDER
AIR AND STRONGER NORTHWEST WINDS GUSTING NEAR 30 KNOTS OVER THE OPEN
WATERS OF LAKE HURON TUESDAY NIGHT INTO WEDNESDAY.

&&

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

$$

AVIATION.....KURIMSKI
SHORT TERM...CB
LONG TERM....BT
MARINE.......BT


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



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