Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 252248
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
648 PM EDT WED MAR 25 2015


.AVIATION...

WEST TO SOUTHWEST FLOW AROUND EXITING LOW PRESSURE WILL FUNNEL MVFR
CIGS INTO FNT/MBS THIS EVENING INTO THE OVERNIGHT WITH PTK ON SOUTH
REMAINING ON THE SOUTHEAST EDGE OF THIS LOWER DECK OF CLOUDS. THESE
SOUTHERNMOST LOCATIONS...HOWEVER...WILL HAVE TO DEAL WITH A QUICK
SHOT OF RAIN OR A RAIN/SNOW MIX AS A SOUTHERN STREAM WAVE RIDES INTO
THE AREA AND PRODUCES A 4 OR 5 HOUR PERIOD OF FGEN FORCING IN THE
10Z-15Z TIME FRAME. THIS PRECIPITATION WILL BE ACCOMPANIED BY MVFR
TO OCCASIONAL IFR CONDITIONS. ONCE THIS SYSTEM EXITS TO THE EAST OF
THE AREA...LOWER VFR CIGS IN THE 4-8KFT RANGE WILL BE THE RULE FOR
THE REMAINDER OF THURSDAY.

FOR DTW...VFR CONDITIONS LOOK TO HOLD UNTIL FGEN KICKS IN WITH THE
SOUTHERN STREAM WAVE LATE TONIGHT. THIS SYSTEM WILL BRING -RASN WITH
MVFR TO IFR CIGS...GENERALLY IN THE 11Z-15Z PERIOD. CONDITIONS WILL
THEN GRADUALLY IMPROVE THEREAFTER.

//DTW THRESHOLD PROBABILITIES...

* HIGH IN CEILINGS AOB 5000 FT 10Z-12Z THROUGH 18Z-20Z.

* LOW IN PRECIPITATION TYPE AS -RASN EARLY THURSDAY MORNING.

&&

.PREV DISCUSSION...ISSUED 349 PM EDT WED MAR 25 2015

SHORT TERM... THROUGH THURSDAY MORNING

FRONTAL OCCLUSION LIFTING TO THE NORTHEAST LATE THIS AFTERNOON.  A
MODEST UPTICK IN THE POST-FRONTAL SOUTHWEST GRADIENT AND DIURNAL
MIXING AS SLIGHTLY COOLER AIR DRAINS IN BEHIND THIS LEAD FRONTAL
ZONE SUSTAINING A GUSTINESS TO THE WIND FIELD...AS WELL AS
INITIATING SOME EROSION TO THE EXISTING STRATUS.  THIS PROCESS WILL
CONTINUE THROUGH THE FIRST HALF OF TONIGHT...ALTHOUGH RECENT MODEL
RH FIELDS AND UPSTREAM SATELLITE WOULD SUGGEST ANY EVENING CLEARING
WILL BE SHORT LIVED AS CONTINUED WEAK COLD AIR ADVECTION AUGMENTS
ADDITIONAL SATURATION WITHIN THE LOWER LAYERS.  THIS WILL ENSURE THE
NOCTURNAL COOLING RESPONSE WILL BE MORE GRADUAL...UNFAVORABLE
RADIATIONAL COOLING ENVIRONMENT GIVEN BOTH THE CLOUD COVERAGE AND
EXISTING GRADIENT FLOW.  LOWS TONIGHT RANGING FROM LOWER 30S NORTH
TO UPPER 30S IN THE DETROIT AREA.

UPPER JET STRUCTURE ANCHORING THE INBOUND LONGER WAVELENGTH NORTHERN
STREAM INTO THE UPPER GREAT LAKES TONIGHT WILL STRENGTHEN AS A
SECONDARY WAVE NOW OVER THE SOUTHERN PLAINS EJECTS NORTHEAST.  THIS
WILL ILLICIT A SOLID LOWER LEVEL FGEN RESPONSE ALONG THE SLOWLY
EXITING BAROCLINIC ZONE ACROSS THE NORTHERN OHIO VALLEY.  SOUTHEAST
MICHIGAN REMAINS MORE PRECARIOUSLY POSITIONED ALONG THE NORTHERN
FLANK AND AT A HIGHER LEVEL /600 MB/ WITH THIS FORCING...A PLACEMENT
THAT WILL LIKELY LEAVE A DEFINED NORTHERN GRADIENT TO THE EMERGING
PRECIPIATION SHIELD.  VIRTUALLY ALL MODEL SOLUTIONS ASIDE FROM THE
NAM ALLOW THIS MOISTURE TO WORK AS FAR NORTH AS THE M-59 CORRIDOR
WITHIN THE 09Z-15Z WINDOW.   GIVEN THE UNDERLYING SENSITIVITY OF THE
POSITION OF THIS FORCING...WILL LEAN TOWARD A CONSENSUS APPROACH
WHICH FAVORS AN UPWARD ADJUSTMENT IN POPS ACROSS SOUTHERN SECTIONS
OF THE FORECAST AREA THROUGH MID-LATE MORNING PERIOD.   MARGINAL
DEPTH TO THE MELTING LAYER SUGGESTS A FEW WET SNOWFLAKES MAY MIX
IN...PARTICULARLY ALONG/NORTH OF THE RIDGE LINE.

LONG TERM...THURSDAY AFTERNOON THROUGH NEXT WEDNESDAY

DEEPER MOISTURE WILL EXIT LATE THURSDAY MORNING BRINGING AN END TO
THE PRECIP BY AROUND 15Z. COLD ADVECTION ENSUES BUT WILL BE OFFSET
BY A DEEPENING BOUNDARY LAYER AND POSSIBLY SOME BREAKS IN THE CLOUD
COVER. THIS SHOULD ALLOW HIGHS TO REACH THE LOW/MID 40S WITH BREEZY
CONDITIONS DEVELOPING BY AFTERNOON.

A SECONDARY FRONT WILL BE PUSHING SOUTHWARD THROUGH NORTHERN
MICHIGAN AND LAKE HURON THURSDAY NIGHT AND THROUGH SOUTHEAST
MICHIGAN ON FRIDAY. ALOFT...THE TROUGH AXIS AND COLD POOL
CHARACTERIZED BY H85 TEMPS DOWN TO NEAR -14C WILL BE OVERHEAD. LAPSE
RATES WILL STEEPEN BEHIND THIS FRONT AS LOW-LEVEL WINDS TURN
NORTHERLY. SOME SUPERSATURATION WITH RESPECT TO ICE WITHIN THE DGZ
IS SHOWN ON AREA SOUNDINGS...WORTHY OF A LOW-CHANCE POP FOR SNOW
SHOWERS FOR THE NORTHERN HALF OF THE FA THURSDAY NIGHT AND THE
ENTIRE AREA FRIDAY. THE NORTHERLY FETCH OFF LAKE HURON MAY PROVIDE
SOME LAKE ENHANCEMENT FOR THE THUMB...BUT GIVEN LACK OF DEEPER
MOISTURE WILL KEEP ACCUMULATIONS TO A HALF INCH WITH LITTLE OR NO
ACCUMULATION ELSEWHERE. FUTURE SHIFTS CAN ASSESS POTENTIAL FOR A
MORE LOCALIZED ENHANCED BAND TO DEVELOP IF SOME LOW-LEVEL
CONVERGENCE CAN SET UP. WITH COLD POOL OVERHEAD AND HEALTHY CLOUD
FRACTION EXPECTED...HIGHS WILL STRUGGLE TO THE FREEZING MARK IN
METRO DETROIT WITH ONLY MID-20S ACROSS COLDEST SPOTS OF THE THUMB.

TROUGH AXIS TRANSLATES EASTWARD FRIDAY NIGHT WITH HIGH PRESSURE
BUILDING IN OVER THE WESTERN GREAT LAKES. UNCERTAINTY REMAINS WITH
HOW QUICKLY WE CAN DECOUPLE /IF AT ALL/ FRIDAY NIGHT AS WELL AS HOW
QUICKLY CLEARING TAKES PLACE AS THE CENTER OF THE HIGH IS STILL OFF
TO OUR WEST. POTENTIAL IS THERE FOR LOWS TO BE QUITE COLD...MAINLY
TEENS IN THIS FORECAST PACKAGE.

THIS WEEKEND WILL START OF DRY BEFORE PRECIPITATION ONCE AGAIN
ENTERS BACK INTO THE PICTURE BY THE END OF THE WEEKEND.  LONGWAVE
TROUGH WILL BE IN THE PROCESS OF EXITING OFF TO THE EAST AS RIDGING
BRIEFLY BUILDS IN OVER LOWER MICHIGAN SATURDAY INTO SUNDAY.  ANOTHER
TROUGH AND ASSOCIATED WAVE DROPS DOWN ACROSS THE NORTHERN GREAT
LAKES ON SUNDAY BRINGING WITH IT THE NEXT CHANCE FOR PRECIPITATION.
BY NEXT WEEK MONDAY...NORTHWESTERLY FLOW TAKES OVER BEHIND THE
FRONTAL BOUNDARY AS THE SURFACE LOW PUSHES TOWARDS THE EAST COAST.
THE REMAINDER OF THE EXTENDED FORECAST PERIOD REMAINS MUDDLED AS
MODELS DEPICT DIFFERENT WAVES TRANSVERSING ACROSS THE GREAT LAKES
REGION.  AS FAR AS TEMPERATURES ARE CONCERNED...THEY LOOK TO START
TO MODERATE TO MORE NORMAL READINGS INTO NEXT WEEK.

MARINE...

SOUTHWESTERLY WINDS GUSTING TO NEAR 20 KNOTS THIS AFTERNOON WILL
EASE OVERNIGHT INTO THURSDAY AS LOW PRESSURE PULLS AWAY AND THE
GRADIENT DECREASES. A SECONDARY COLD FRONT WILL DROP SOUTHWARD
THROUGH LAKE HURON THURSDAY NIGHT WITH UNSTABLE CONDITIONS
DEVELOPING BEHIND IT. WINDS WILL TURN NORTHERLY BEHIND THIS FRONT
WITH GUSTS OF 25 TO NEAR 30 KNOTS POSSIBLE OVER LAKE HURON. THIS
FRONT WILL BE ACCOMPANIED BY SNOW SHOWERS. THE FRONT WILL CLEAR THE
REMAINDER OF THE WATERS DURING THE DAY ON FRIDAY. WINDS WILL
DIMINISH LATE FRIDAY NIGHT INTO SATURDAY AS HIGH PRESSURE BUILDS
INTO THE REGION.

&&

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

$$

AVIATION.....DG
SHORT TERM...MR
LONG TERM....DT/SS
MARINE.......DT


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



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