Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 261956
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
356 PM EDT THU MAR 26 2015

.SHORT TERM...THROUGH TONIGHT

LOW/MID LEVEL COLD ADVECTION CONTINUES TO SUPPORT AN EXTENSIVE
STRATOCU DECK ACROSS THE WESTERN GREAT LAKES. THIS BEGAN AS THE
STRONG UPPER JET AND ASSOCIATED LOW LEVEL BAROCLINIC ZONE SHIFTED
EASTWARD THIS MORNING. UPSTREAM CLOUD COVERAGE APPEARS SOLID ON
VISIBLE SATELLITE THIS AFTERNOON DESPITE SLIGHTLY MORE CELLULAR
APPEARANCE OVER FAR SRN MI LATELY. AS SUCH...EXPECT CLOUDY/MOSTLY
CLOUDY CONDITIONS TO PERSIST INTO THE EVENING WITH TEMPS HOLDING
STEADY OR FALLING.

SECONDARY COLD FRONT AT 19Z ALIGNED FROM GEORGIAN BAY THROUGH THE
FAR NORTHEASTERN U.P. AND INTO LAKE SUPERIOR. THIS FRONT WILL
PROGRESS THROUGH NORTHERN MICHIGAN AND LAKE HURON
OVERNIGHT...APPROACHING THE THUMB/SAGINAW VALLEY REGIONS BY AROUND
09Z. NAM FORECAST SOUNDINGS FOR BAX PAINT A FAVORABLE PICTURE FOR
LAKE EFFECT SNOW OVER THE THUMB AFTER 06Z. LOW-LEVEL WIND
TRAJECTORIES BECOME NORTH/NORTHEASTERLY WITH LAPSE RATES INCREASING
AND SUPERSATURATION WRT ICE UP TO ABOUT 750 HPA. 0-1 KM THETA-E
LAPSE RATES INCREASE TO 1-3 K/KM BY 12Z AS 925/850 MB TEMPS FALL TO
-9/-14C. CHARACTER OF THE LAKE EFFECT SNOW IS STILL SOMEWHAT
UNCERTAIN. SOME HI-RES GUIDANCE DEPICTS MORE DISORGANIZED LIGHT SNOW
PUSHING INTO THE THUMB INITIALLY AFTER 06-09Z AS LAPSE RATES AND
MOISTURE INCREASE...POSSIBLY EVOLVING INTO MORE OF A DOMINANT BAND
09-12Z AS LOW-LEVEL WINDS BECOME MORE UNIDIRECTIONAL OUT OF THE
NORTH-NORTHEAST...AT LEAST BEFORE DAYTIME HEATING COMMENCES. THIS
SCENARIO SEEMS PLAUSIBLE...ESPECIALLY IF LOW-LEVEL CONVERGENCE CAN
OCCUR. SNOW ACCUMS THROUGH 12Z GENERALLY 0.5-1 INCH FOR HURON COUNTY
WITH A HALF INCH OR LESS ELSEWHERE IN THE THUMB...BUT THIS WILL NEED
TO BE REFINED IF IT LOOKS LIKE A MORE DOMINANT LOCALIZED BAND WILL
SET UP.

ELSEWHERE...MOSTLY CLOUDY SKIES WITH CONTINUED COLD ADVECTION
ALLOWING LOWS TO DROP TO THE LOW/MID 20S. BEST CHANCE OF CLOUD DECK
SCATTERING OUT FOR A TIME WILL BE ACROSS THE SOUTH...BUT CONFIDENCE
IS NOT HIGH.

&&

.LONG TERM...

NORTHERN STREAM TROUGH OVER ONTARIO WILL ROTATE THROUGH THE CENTRAL
GREAT LAKES TOMORROW. 12Z SOUNDINGS OUT OF INTERNATIONAL FALLS AND
PICKLE LAKE ONTARIO REVEALED 850 MB TEMPS OF -14 C AND -20 C
RESPECTIVELY...WITH AN ALMOST TRUE NORTH WIND. THIS COLD
AIRMASS...ALBEIT MODIFIED SLIGHTLY...IS EXPECTED TO LEAD TO SOME
LAKE EFFECT SNOW SHOWERS TOMORROW WITH THE NORTHEAST TO NORTH FLOW
DEVELOPING...AS EVEN 925 MB TEMPS ARE EXPECTED TO FALL TO AROUND -13
C OVER LAKE HURON.

12Z NAM SHOWING GOOD 925 MB POSITIVE OMEGA SIGNAL PUSHING THROUGH
THE NORTHERN THUMB REGION AND EXTENDING SOUTHWEST THROUGH THE REST
OF SOUTHEAST MICHIGAN DURING THE DAY. WITH THE COMMENCEMENT OF
DAYTIME/SURFACE HEATING...PROBABLY GOING TO BECOME DISORGANIZED
ACTIVITY...WITH STEEP LOW LEVEL LAPSE RATES AND RATHER DEEP LAYER OF
SUPERSATURATION WITH RESPECT TO ICE TO SUPPORT SCATTERED SNOW
SHOWERS ACROSS MUCH OF THE AREA. WITH THE TRANSIENT AND DISORGANIZED
NATURE EXPECTED...WILL KEEP ACCUMULATIONS BELOW 1 INCH.

NORTH-NORTHEAST FLOW GRADUALLY WEAKENING FRIDAY NIGHT AS SURFACE
HIGH ATTEMPTS TO BUILD EASTWARD...BUT WITH THE HEART OF THE LOW
LEVEL COLD AIRMASS IN PLACE (850 MB TEMPS AS COLD AS -18
C)...ADDITIONAL LIGHT LAKE EFFECT SNOW SHOWERS ARE EXPECTED ACROSS
THE THUMB REGION. EXTEND OF CLOUD COVER BEYOND THE THUMB REGION
BECOMES CHALLENGING AS MUCH DRIER AIR AND ANTICYLONIC FLOW BEGINS TO
PUSH IN. REGARDLESS...EXPECTING MINS IN THE LOW TO MID TEENS.

CENTER OF HIGH BUILDING AND GENERAL SUBSIDENCE OVER LOWER MICHIGAN
ON SATURDAY SHOULD LEAD TO MOSTLY SUNNY SKIES...BUT COLD AIRMASS
(850 MB TEMPS IN THE NEGATIVE MID TEENS TO START THE DAY...RISING TO
-10 TO -11 C BY DAY`S END)...POINTS TO LOW TO MID 30S EVEN WITH FULL
SUNSHINE.

BRIEF RIDGING ON SUNDAY QUICKLY GIVES WAY TO ANOTHER TROUGH AS A LOW
PRESSURE SYSTEM SLIDES ACROSS THE HUDSON BAY AREA SUNDAY NIGHT INTO
MONDAY.  A COLD FRONT ASSOCIATED WITH THE LOW WILL TRANSVERSE ACROSS
THE GREAT LAKES REGION LATER ON SUNDAY.  EXACT TIMING OF THE FRONTAL
PASSAGE ACROSS THE CWA HAS YET TO BE PINNED DOWN DUE TO DIFFERENCES
CURRENTLY LAID OUT IN THE LATEST MODEL RUNS.  THIS PUTS IN TO
QUESTION PRECIPITATION TYPE THAT WILL ACCOMPANY THE FRONT DEPENDING
ON WHEN IT DOES PUSH THROUGH THE AREA.  NEXT WEEK LOOKS TO STAY
SOMEWHAT ACTIVE AS MORE SHORTWAVES MOVE ACROSS THE GREAT LAKES
REGION.  WARMER AIR DOES FINALLY START TO MAKE INROADS INTO THE AREA
NEXT WEEK...AS TEMPERATURES GET BACK TO NEAR NORMAL READINGS.

&&

.MARINE...

A VERY COLD AIRMASS WILL BE USHERED INTO THE CENTRAL GREAT LAKES
TONIGHT INTO TOMORROW...AS NORTHERLY WINDS GUST UP TO 30 KNOTS OVER
LAKE HURON. AIRMASS WILL EVEN BE COLD ENOUGH TO GENERATE SNOW
SHOWERS...BUT MOSTLY OVER SOUTHEAST MICHIGAN. WINDS WILL GRADUALLY
DIMINISH FRIDAY NIGHT...AS HIGH PRESSURE SETTLES OVER THE
REGION...LEADING TO LIGHT WINDS ON SATURDAY. SOUTHWEST WIND WILL
RAMP UP SATURDAY NIGHT INTO SUNDAY AS WE GET INTO RETURN FLOW AROUND
THE HIGH AND A COLD FRONT APPROACHES. EXPECTING WINDS OF AT LEAST 25
KNOTS OVER MUCH OF LAKE HURON.

&&

.AVIATION...ISSUED 114 PM EDT THU MAR 26 2015

SOLID VFR STRATOCU DECK OVERHEAD WILL PERSIST THROUGH THE AFTERNOON
AS COLD AIR POURS INTO THE REGION...POSSIBLY BREIFLY MVFR OVER
DETROIT METRO TERMINALS EARLY THIS AFTERNOON WHERE LOW LEVEL
MOISTURE HAS BEEN SLOWER TO EXIT. HIGHEST POTENTIAL FOR CIGS TO
LOWER INTO MVFR RANGE AFTER SUNSET FROM PTK NORTHWARD...LESS
CERTAINTY FOR THE METRO DETROIT TERMINALS. LIGHT SNOW SHOWERS ARE
POSSIBLE ALONG/BEHIND A FRONTAL BOUNDARY TOMORROW
MORNING/AFTERNOON...REFRAINED FROM INCLUSION IN THE TAFS FOR THIS
PERIOD UNTIL CONFIDENCE INCREASES.

FOR DTW...SOME OPPORTUNITY FOR CIGS AOB 5KFT TO SCATTER OUT LATER
THIS AFTERNOON INTO THE EARLY OVERNIGHT HOURS. SOME LIGHT SNOW
SHOWERS ARE POSSIBLE TOMORROW ALONG/BEHIND A COLD FRONT AFTER AROUND
15Z TOMORROW.


//DTW THRESHOLD PROBABILITIES...

* MEDIUM IN CEILINGS BELOW 5000 FT THROUGH THE TAF PERIOD.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO MIDNIGHT EDT FRIDAY
     NIGHT FOR LHZ421-441-442.

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

$$

SHORT TERM...DT
LONG TERM....SF/SS
MARINE.......SF
AVIATION.....DT


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



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