Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 280757
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
357 AM EDT SAT MAR 28 2015

.SHORT TERM...TODAY AND TONIGHT

A COUPLE OF FACTORS HAVE COMBINED TO HELP THE SHORE PARALLEL BAND OF
LIGHT LAKE EFFECT SNOW TO PERSIST ALONG THE SHORELINE OF LAKE HURON
OVERNIGHT. THE FIRST HAS BEEN THE STREAMLINING OF NORTHERLY SURFACE
WIND TRAJECTORIES TO PRODUCE AN AREA OF LOCALIZED CONVERGENCE.
SURFACE OBSERVATIONS HAVE BEEN REPORTING A WESTERLY TRAJECTORY OVER
THE EASTERN HALF OF THE LOWER PENINSULA AND EASTERLY TRAJECTORIES AT
THE SHORELINE...PORT HOPE/SARNIA. STATIC NATURE OF THE BANDING
ON RADAR IN ADDITION TO NEGATIVE LOW LEVEL THETA E LAPSE RATES
AND NEAR SURFACE CONVERGENCE CONTINUING IN MODEL DATA THROUGH 9Z
SUGGESTS THE SNOW SHOWER POTENTIAL HAS ANOTHER 2 TO 4 HOURS. RAP
OUTPUT SUGGESTS THERE IS SOME ORGANIZED SIGNAL TO DEEPER MIDLEVEL
MOISTURE ROTATING CYCLONICALLY AROUND A CENTER POINT OVER THE
EASTERN END OF LAKE ERIE. THIS SUGGESTS THE
DEEPER MOISTURE WILL PIVOT AWAY FROM THE LOW LEVEL INSTABILITY
SOURCE IN THE NEXT FEW HOURS. THOUGHT IS AS THIS MOISTURE PUSHES
SOUTHWARD AWAY FROM SOUTHERN LAKE HURON WILL SEE LAKE EFFECT
ACTIVITY WANE AFTER 9Z. REGARDLESS...SNOW SHOWERS REMAIN LIKELY IN
THE NEAR TERM WITH MINOR ACCUMULATIONS POSSIBLE ALONG THE SHORELINE.

DIFFERENTIAL GEOPOTENTIAL HEIGHT REBOUND WILL CAUSE SURFACE HIGH
PRESSURE TO EXPAND AGGRESIVELY EASTWARD THROUGH THE CWA BY MIDDAY.
LOW TO MIDLEVEL FLOW TRAJECTORIES DEPICT STUBBORN CYCLONIC FLOW INTO
THE LATE AFTERNOON BEFORE EVENTUALLY RELINQUISHING BY LATE
AFTERNOON. THE ARRIVAL OF THE ANTICYCLONIC FLOW WILL PROBABLY END
ANY POTENTIAL FOR CONTINUED LAKE EFFECT CLOUD THAT MAY HANG ON
ACROSS THE EASTERN CWA TODAY. WITH NORTHERLY FLOW FIRMLY IN
CONTROL...WANTED TO HANG CLOSE TO GUIDANCE WITH TEMPERATURES AROUND
30 TO THE LOW 30S POSSIBLE.

QUIET WEATHER IS FORECASTED TONIGHT WITH HIGH PRESSURE AT THE
SURFACE AND SHORTWAVE RIDGING ALOFT. TEMEPRATURES WILL AGAIN BE COLD
WITH READINGS FALLING INTO THE TEENS ACROSS ALL OF THE AREA (10 TO
15 DEGREES BELOW AVERAGES).

&&

.LONG TERM...

SUNDAY WILL START AN ACTIVE PERIOD OF WEATHER CONSISTING OF A SERIES
OF SHORT WAVES MOVING THROUGH THE NORTHERN TIER OF STATES THROUGH
NEXT WEEK. WHILE IT WILL BE ACTIVE IN TERMS OF PRECIPITATION...THERE
WILL BE AN UNDERLYING WARMING TREND THROUGH THE PERIOD. THIS WILL BE
DRIVEN BY AN ENERGETIC PACIFIC UPPER LEVEL JET THAT WILL FORCE A
TRANSITION OUT OF THE LONG WAVE RIDGE OVER THE WEST/TROUGH OVER THE
EAST THAT HAS BEEN SO PERSISTENT AND RESISTANT TO THE ONSET OF
SPRING. THIS LARGE SCALE TRANSITION SUPPORTS GUIDANCE TEMPS OFFERING
HIGHS PUSHING 60 BY THURSDAY.

FIRST THING FIRST IS THE NEXT LOW PRESSURE SYSTEM MOVING THROUGH THE
CENTRAL ROCKIES TODAY ON SCHEDULE TO ARRIVE IN THE GREAT LAKES
SUNDAY. MODEL AGREEMENT REMAINS SOLID IN THE LATEST CYCLE WITH THE
DEPICTION OF MODEST SURFACE LEE CYCLOGENESIS OVER THE NORTHERN
PLAINS AND CANADIAN PRAIRIE...ENOUGH TO DRAW SOME GULF MODIFIED AIR
NORTHWARD TO AUGMENT MID LEVEL PACIFIC MOISTURE AND BRING
PRECIPITATION INTO SE MICHIGAN FROM MID SUNDAY AFTERNOON THROUGH
SUNDAY EVENING. THE DETERMINATION OF PRECIPITATION TYPE REMAINS
COMPLICATED BY STRONG WET BULB COOLING SHOWN IN MODEL SOUNDINGS
OPPOSED BY STRONG LOW LEVEL WARM ADVECTION. THE SAME MODEL SOUNDINGS
INDICATE THE BOUNDARY LAYER GROWING TO ABOUT 900 MB...GOOD ENOUGH
FOR SURFACE WIND GUSTS PUSHING 30 KNOTS...WHICH WILL EASILY CARRY
TEMPERATURES INTO THE LOWER 40S BEFORE THE MOISTURE ARRIVES. THE LOW
LEVEL JET CENTERED AROUND 850 MB WILL ALSO BE PUSHING 60 KNOTS WHICH
WILL BE CAPABLE OF DRIVING THE LOW LEVEL THERMAL RIDGE WELL INTO THE
SAGINAW VALLEY WITH THE ONSET OF PRECIPITATION. THE OVERALL STRENGTH
OF THE SOUTHWEST FLOW IS THEN EXPECTED TO SUPPORT AN ABOVE FREEZING
BOUNDARY LAYER TEMPERATURE PROFILE CLOSE TO 1500 FT DEEP INTO
SURFACE TEMPERATURES IN THE LOWER 40S...SUFFICIENT FOR MELTING TO
RAIN AS LONG AS PRECIPITATION RATE REMAINS AS LOW AS THAT IMPLIED BY
3 HR MODEL QPF AROUND 0.1 INCH.

A QUICK PASSAGE OF THE COLD FRONT ASSOCIATED WITH THIS SYSTEM WILL
OCCUR SUNDAY NIGHT AND BRING A TRANSITION BACK TO SNOW SHOWERS
DURING THE EVENING. SOME LINGERING WRAP-AROUND MOISTURE WITH THE
UPPER WAVE WILL COMBINE WITH THE FRONTAL FORCING TO SUPPORT THE BEST
COVERAGE IN THE SAGINAW VALLEY AND THUMB RESULTING IN A SLUSHY
COATING BEFORE ENDING. COLD ADVECTION TRAILING THE FRONT DURING
MONDAY WILL NOT RESULT IN AS COLD AN AIR MASS AS WE ARE EXPERIENCING
THIS WEEKEND...BUT IT WILL BE ADEQUATE ENOUGH TO SET THE STAGE FOR
PRECIPITATION TYPE QUESTIONS AS THE NEXT SYSTEM ARRIVES MONDAY NIGHT
INTO TUESDAY. THIS ONE WILL BE MERELY A RIPPLE WITHIN THE BAROCLINIC
ZONE LEFT NEARBY TO THE SOUTH AND WEST AND APPEARS FRAUGHT WITH LOW
PREDICTABILITY. THE WAVE WILL BE OPEN ALOFT BUT THE MODELS OFFER A
BROAD RANGE OF SOLUTIONS ON THE DEPTH...TRACK...AND TIMING OF THE
SURFACE LOW/TROUGH. THE 00Z RUNS ARE TRENDING TOWARD A DEEPER
SURFACE WAVE MOVING THROUGH THE SOUTH HALF OF LOWER MICHIGAN LATE
MONDAY NIGHT THROUGH TUESDAY MORNING.

THE TUESDAY WAVE WILL BE THE LAST ONE BEFORE THE NORTHERN STREAM
BEGINS TO LIFT NORTHWARD WEDNESDAY INTO THURSDAY. THIS WILL BE DUE
TO THE LONG WAVE PATTERN SHIFT BEING DRIVEN BY A LARGER PACIFIC LOW
PRESSURE SYSTEM EXPECTED TO MOVE THROUGH CENTRAL CANADA THURSDAY.
GLOBAL MODEL SOLUTIONS INDICATE QUITE A BIT OF SPREAD IN THE UPPER
AIR PATTERN TOWARD THE END OF THE WEEK BUT THE DECREASED LONG WAVE
AMPLIFICATION WILL RESULT IN A MODERATING TEMPERATURE TREND IN
BETWEEN POTENTIAL ROUNDS OF SHOWERS INTO NEXT WEEKEND.

&&

.MARINE...

A BROAD AREA OF HIGH PRESSURE WILL SLIDE ACROSS THE GREAT LAKES
TODAY AND BRING FAVORABLE MARINE CONDITIONS THROUGH TONIGHT.
SOUTHWEST WIND WILL THEN INCREASE CONSIDERABLY DURING SUNDAY AS THE
NEXT LOW PRESSURE SYSTEM APPROACHES. GUSTS THROUGH SAGINAW BAY AND
OVER THE OPEN WATERS OF LAKE HURON WILL REACH 30 KNOTS BUT LIKELY
STAY BELOW GALES BEFORE MID LAKE. WARMER AIR MOVING OVER THE COLD
WATER AND REMAINING ICE WILL BE A LIMITING FACTOR DUE TO INCREASED
STABILITY. THE ASSOCIATED COLD FRONT WILL THEN SWEEP THROUGH SUNDAY
NIGHT BUT WILL NOT BRING AS MUCH COLD AIR AS WE HAVE SEEN RECENTLY.
NORTHWEST GUSTS NEAR 30 KNOTS WILL BE CONFINED TO THE NORTH HALF OF
LAKE HURON BEFORE HIGH PRESSURE BUILDS OVER THE REGION MONDAY.

&&

.AVIATION...ISSUED 1150 PM EDT FRI MAR 27 2015

IT APPEARS ONE LAST SURGE OF LOW LEVEL CLOUDS WILL PIVOT DOWN INTO
THE TERMINALS FROM LAKE HURON WITHIN NORTHEAST FLOW OF 5 TO 10
KNOTS. THIS WILL BRING A PERIOD OF LOWER VFR CIGS FROM KFNT ON
SOUTH. EXPECT CLEARING ON SATURDAY AS HIGH PRESSURE BUILDS INTO THE
AREA WITH WINDS BACKING TO NORTHWEST AND THEN BECOMING LIGHT AND
VARIABLE BY SATURDAY EVENING AS THE CENTER OF THIS HIGH REACHES THE
AREA.

FOR DTW...GENERALLY EXPECT FEW-SCT VFR CONDITIONS...BUT THERE WILL
BE A CHANCE OF A SEVERAL HOUR PERIOD OF BKN CIGS AROUND 5KFT LATE
TONIGHT AS MOISTURE FUNNELS INTO AREA FROM THE THUMB.

//DTW THRESHOLD PROBABILITIES...

* LOW CONFIDENCE IN CEILINGS AROUND 5000 FT THROUGH LATE TONIGHT
  INTO EARLY SATURDAY MORNING.

&&

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

$$

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


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



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