Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 270828
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
328 AM EST THU NOV 27 2014

.SHORT TERM... TODAY AND TONIGHT

BROAD NORTHERN STREAM SHORTWAVE WORKING THROUGH THE HIGHER AMPLITUDE
TROUGHING ENTRENCHED ACROSS THE GREAT LAKES WILL TRANSLATE ACROSS
SOUTHEAST MICHIGAN THIS AFTERNOON.  MODEST RESPONSE NOTED EARLY THIS
MORNING ACROSS EASTERN WISCONSIN WITH THIS FEATURE AND THE ATTENDANT
ARCTIC COLD FRONT...SEVERAL HOURS OF LIGHT SNOW SHOWERS WITH SOME
MINOR DISRUPTIONS TO VISIBILITY /2SM OR GREATER/.  DOWNSTREAM
ENVIRONMENT NOT ALL THAT DIFFERENT...A LAKE MODIFIED RESIDUAL
MOISTURE PLUME LIKELY CONTRIBUTING TO SLIGHTLY GREATER MOISTURE
DEPTH.  THIS WILL EFFECTIVELY SUSTAIN A CORRIDOR OF LIGHT SNOW
SHOWERS FROM NORTHWEST TO SOUTHEAST THROUGH THE REGION 15Z TO 21Z.
WHILE THIS MAY YIELD A PERIOD OF GREATER COVERAGE /SCATTERED TO
NUMEROUS/...ACCUMULATION POTENTIAL WILL BE LIMITED BY A LACK OF
GREATER FORCING...MOISTURE QUALITY /1 G/KG OF SPECIFIC HUMIDITY/ AND
OVERALL DURATION.  MINOR ACCUMULATION AT HALF INCH OR LESS.  A WELL
DEFINED THERMALLY INDUCED LAKE HURON AGGREGATE TROUGH AXIS EXTENDING
NORTHWEST TO SOUTHEAST WILL RESIDE JUST OFF THE NORTHEAST HURON
COUNTY SHORELINE. THERE WILL REMAIN A LOW POTENTIAL FOR THE WESTERN
PERIPHERY OF THE ASSOCIATED STRONG CONVERGENCE ZONE TO CLIP THE
SHORELINE LOCATIONS.  LATEST HI RES MODEL GUIDANCE RETAINS THE
SUBSEQUENT ORGANIZED BANDS JUST OFF SHORE...BUT A TREND WORTH
MONITORING GOING FORWARD TODAY.

THE EXISTING THERMAL PROFILE WILL VARY LITTLE FROM THAT NOTED OVER
THE PAST TWO DAYS.  THIS WILL AGAIN BRINGS HIGHS INTO THE LOWER 30S
UNDER 10 TO 15 MPH NORTHWEST WINDS.  COLD AIR ADVECTION RAMPS UP
POST-FRONTAL STARTING THIS EVENING.  850 MB TEMPERATURES BOTTOM OUT
IN THE -12C RANGE BY FRIDAY MORNING.  STRENGTHENING MID LEVEL
SUBSIDENCE AND A DRYING NORTHWEST FLOW WILL INCREASE THE POTENTIAL
FOR GREATER EROSION OF THE RESIDUAL SUB-INVERSION MOIST LAYER.  THIS
WILL FAVOR A PROGRESSION TO AT LEAST PARTLY CLOUDY...A PERIOD OF
MORE AGGRESSIVE CLEARING CERTAINLY PLAUSIBLE.  LOWS TONIGHT IN THE
UPPER TEENS.

&&

.LONG TERM...

UPPER WAVE JUST MOVED ONSHORE OF THE PACIFIC NORTHWEST...AND 12Z
MODEL SUITE SHOULD BE ABLE TO ZERO IN ON THIS SYSTEM WITH THE BETTER
SAMPLING. WITH THAT IN MIND...THE 00Z NAM HAS COME IN CONSIDERABLY
FARTHER NORTH WITH THIS WAVE FOR LATE FRIDAY/FRIDAY EVENING...WITH
NO PRECIPITATION FORECASTED SOUTH OF M-59...ALONG WITH THE BULK OF
QPF NORTH OF SAGINAW BAY. IT CERTAINLY WILL BE A CHALLENGE TO GET
PRECIPITATION GOING OVER SOUTHEAST MICHIGAN...AS A DEEP DRY LAYER IS
IN PLACE TO START THE DAY ON FRIDAY...AS 850-700 MB DEW PT
DEPRESSIONS ARE IN THE 30 TO 35 C RANGE. THE MOISTURE TRANSPORT (850-
700 MB THETA-E) INTO THE CENTRAL GREAT LAKES IS RATHER STEADY FRIDAY-
FRIDAY NIGHT...AND NOT A VERY WELL DEFINED SURGE EVIDENT (BEST
SEMBLANCE 0-4Z SATURDAY)...DRAWING CONCERN IN THE LIFT AND PROSPECTS
FOR SNOW. HOWEVER...THE 00Z CANADIAN IS MUCH FARTHER SOUTH WITH THE
250 MB JET OF 100+ KNOTS THAN THE NAM. THE 00Z EURO SEEMS TO OFFER
UP A NICE COMPROMISE...AND A PERIOD OF LIGHT SNOW SEEMS LIKE A GOOD
BET WITH THE QUICK SHOT OF FGEN/ISENTROPIC ASCENT. WILL RAISE
POPS...LIFTING AREAS ALONG AND NORTH OF I-69 TO LIKELY EARLY FRIDAY
EVENING...WHERE AROUND AN INCH IS EXPECTED BEFORE TAPERING OFF EARLY
SATURDAY MORNING. UP TO 2 INCHES POSSIBLE NEAR SAGINAW BAY/EXTREME
NORTHERN PORTION OF THE CWA.

BIG WARM-UP ON TAP FOR THE WEEKEND...WITH STRONG AND DEEP SOUTHWEST
FLOW DEVELOPING...AS 925 MB TEMPS PROGGED TO SURGE TO 10 C ON SUNDAY
AHEAD OF COLD FRONT...MAKING A RUN SOLIDLY INTO THE 50S LIKELY. DEW
PTS ARE NOT TOO FAR BEHIND...AND WITH THIS MOISTURE STREAMING NORTH
OVER THE COLD GROUND OF LOWER MICHIGAN...WILL BE CARRYING LOW CLOUDS
AND POSSIBLE DRIZZLE/VERY LIGHT RAIN SATURDAY NIGHT INTO
SUNDAY...EVEN THOUGH THE MID LEVELS (700 MB) WILL BE EXTREMELY DRY.

&&

.MARINE...

AN ARCTIC COLD FRONT WILL DROP THROUGH THE GREAT LAKES TODAY...
USHERING IN A COLDER AND MORE UNSTABLE AIRMASS. THIS WILL RESULT IN
WINDS INCREASING AS THEY BECOME NORTHWESTERLY DURING THE DAY. WITH
ENHANCED LAKE HURON TROUGHING...A SHORT PERIOD OF MARGINAL GALES
APPEARS LIKELY...AND HAVE ISSUED GALE WARNING FOR THE OPEN WATERS OF
LAKE HURON FROM PRESQUE ISLE LIGHT TO STURGEON POINT THIS AFTERNOON
INTO EARLY THIS EVENING. FARTHER SOUTH...WINDS WILL GUST BETWEEN 25
TO 30 KNOTS...CLIPPING THE NEARSHORE WATERS AND LEADING TO HIGH
WAVES OVER SOUTHERN LAKE HURON TONIGHT INTO TOMORROW MORNING.
CONSEQUENTLY...HAVE ISSUED SMALL CRAFT ADVISORIES FOR ALL NEARSHORE
WATERS WITH THE EXCEPTION OF SAGINAW BAY.  A WARM FRONT LIFTING INTO
THE REGION FRIDAY WILL FLIP THE WINDS TO THE SOUTHWEST/SOUTH BY
FRIDAY EVENING...WITH GUSTS OF 25 TO 30 KNOTS EXPECTED OVER MUCH OF
LAKE HURON BEFORE MILDER AIR AND GREATER STABILITY ARRIVES OVER THE
WEEKEND.

&&

.AVIATION...ISSUED 1153 PM EST WED NOV 26 2014

//DISCUSSION...

A DEEP INVERSION BASED AROUND 4K FT AGL IS EXPECTED TO PERSIST
THROUGH THE NIGHT AND INTO EARLY THURS AFTERNOON. THIS WILL SUSTAIN
A 3500-4500 FT STRATUS DECK ACROSS SE MI. THERE HAS ALSO BEEN A
SECOND CLOUD DECK BASED BETWEEN 2500 FT AND 3000 FT WITH SOME
FLURRIES. IN TERMS OF SE MI...THESE LOWER CLOUDS AND FLURRIES HAVE
BEEN MORE PREVALENT IN AND AROUND METRO DETROIT WHERE SOME BETTER
LOW LEVEL MOISTENING FROM THE EAST HAS OCCURRED THIS AFTERNOON. THE
LOW LEVEL FLOW WILL BACK FROM NORTHEAST THIS EVENING TO NORTHWEST
OVERNIGHT. SOME ADDED HEAT FLUX OFF LAKE HURON OVERNIGHT MAY BOOST
THE INVERSION A LITTLE BIT. THE TREND TOWARD NORTHWEST FLOW MAY ALSO
ADD JUST A LITTLE DRYING TO THE LOW LEVELS. THESE FACTORS SUGGEST A
TREND TOWARD PREVAILING LOW END MVFR CLOUD BASES /3500-4500 FT/
OVERNIGHT...ALTHOUGH FLUCTUATING CEILINGS COULD STILL BE POSSIBLY
THROUGH DAYBREAK THURS.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CEILINGS BELOW 5000 FT THROUGH TONIGHT AND
  THURSDAY MORNING.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...GALE WARNING FROM 2 PM THIS AFTERNOON TO 10 PM EST THIS EVENING FOR
     LHZ362.

     SMALL CRAFT ADVISORY FROM NOON TODAY TO 7 AM EST FRIDAY FOR LHZ421-
     441>443.

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

$$

SHORT TERM...MR
LONG TERM....SF
MARINE.......SF
AVIATION.....SC


YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE
AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).



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