Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 242341
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
641 PM EST SAT JAN 24 2015

.AVIATION...

MOIST PRE-FRONTAL WEST-SOUTHWEST FLOW WILL SUSTAIN A BLANKET OF
STRATUS THROUGHOUT SE MICHIGAN THIS EVENING.  EARLIER EROSION OF
MOISTURE IN THE LOWEST LEVELS WILL PROVIDE MORE VARIABILITY IN
CEILINGS HEADING INTO THE EARLY PORTION OF THE NIGHT.  OBSERVATIONS
SUGGEST BASES WILL RESIDE WITHIN THE 2500 TO 4000 FT LEVEL.  PASSAGE
OF A FRONTAL BOUNDARY WILL FLIP WINDS TO NORTHEASTERLY DURING THE
EARLY MORNING PERIOD.  THIS PROCESS MAY ALLOW FOR SOME RENEWED
EXPANSION IN COVERAGE OF LOWER MVFR STRATUS THROUGH THIS TIME.
LIMITED POTENTIAL FOR LIGHT SNOW SHOWERS TO EMERGE WITH THIS FRONT
ACROSS THE DETROIT CORRIDOR SUNDAY MORNING BEFORE IT SETTLES
SOUTHWARD.  SE MICHIGAN WILL REMAIN NORTH OF THE MAIN SWATH OF
SNOWFALL ATTENDANT TO LOW PRESSURE TRACKING ACROSS THE OHIO VALLEY
ON SUNDAY.  DRIER AIR WORKING IN FROM THE NORTH WILL FAVOR A GRADUAL
CLEARING OF ANY LINGERING LOWER STRATUS FROM NORTH TO SOUTH THROUGH
THE DAY.

//DTW THRESHOLD PROBABILITIES...

* HIGH IN CEILINGS BELOW 5000 FEET THROUGH SUNDAY MORNING.

&&

.PREV DISCUSSION...ISSUED 402 PM EST SAT JAN 24 2015

SHORT TERM...TONIGHT

WEAK LOW LEVEL PREFRONTAL/AGGREGATE TROUGH HAS SEEMINGLY ERODED DUE
TO DIABATIC EFFECTS OF DIURNAL HEATING. SOLID WESTERLY FLOW
TRAJECTORIES ARE IN PLACE OVER THE ENTIRE CWA WITH AFTERNOON
TEMPERATURES RANGING IN THE LOWER TO UPPER 30S. THE INCREASED MIXING
HAS LIFTED CEILING HEIGHTS SLIGHTLY AND FOR THIS REASON REMOVED THE
CHANCE OF MEASURABLE PRECIPATION.

A WEAKNESS OR COL IN THE MSLP EXISTS OVER THE GREAT LAKES
SANDWHICHED BETWEEN THE NORTHEASTERN UNITED STATES CYCLONE AND A
DEEPENING CLIPPER SYSTEM THAT IS ADVANCING THROUGH THE DAKOTAS. THIS
FEATURE WILL SERVE AS A FOCUS FOR ONGOING AND RAPID STRENGTHENING OF
A NEAR SURFACE COLD FRONT THROUGH TONIGHT.

A RATHER INNOUCOUS UPPER LEVEL JETLET AND REMNANT MOMENTUM FROM AN
EARLIER ROSSBY WAVE BREAK WILL PUSH ACROSS WISCONSIN AND INTO LOWER
MICHIGAN DURING THE LATE AFTERNOON HOURS. A MIDLEVEL EXTENSION OF
THIS SAME MOMENTUM WILL HELP ALLOW SOME H7 MOISTURE ADVECTION AHEAD
OF THE ORGANZING COLD FRONT. THE ADDITION OF THIS MOISTURE MAY ALLOW
SOME SEEDING TO OCCUR FOR THE UNDERLYING MOIST AMBIENT MOISTURE.
DECIDED TO MENTION A CHANCE OF FLURRIES OR DRIZZLE THROUGH EARLY
THIS EVENING.

THE EARLY PORTION OF THE NIGHT WILL BE FAIRLY QUIET AND ACTUALLY
BALMY. TEMPERATURES ARE EXPECTED TO REMAIN IN THE LOW TO MID 30S FOR
MUCH OF THE NIGHT. A BACKDOOR COLD FRONT IS FORECASTED TO
AGGRESSIVELY PUSH SOUTHWARD THROUGH THE GREAT LAKES TONIGHT. TIMING
OF THIS SHALLOW ARCTIC FRONT IS EXPECTED TO BE BETWEEN 07-09Z

LONG TERM...SUNDAY THROUGH FRIDAY

THE LONGWAVE PATTERN WILL BE COMPLETING THE TRANSITION FROM SPLIT
FLOW TO DEEP EASTERN CONUS TROUGH EARLY SUNDAY. AIDING THIS PROCESS
WILL BE A STRONG NORTHERN STREAM JET STREAK DIGGING SOUTHWARD ALONG
THE FRONT RANGE OF THE ROCKIES SUNDAY MORNING. CYCLOGENESIS ON THE
NOSE OF THE JET WILL PRODUCE A SFC LOW OVER THE CENTRAL PLAINS WHICH
WILL TRACK EASTWARD SUNDAY ALONG A COLD FRONT DRAPED ACROSS SOUTHERN
LOWER MI. MODELS HAVE TRENDED SOUTHWARD WITH EACH OF THE LAST FEW
RUNS WHICH SEEMS WELL WARRANTED WHEN ANALYZING MID/UPPER LEVEL
FORCINGS. THE JET DIVING NEARLY DUE SOUTHWARD DEEPENING THE TROUGH
TAKES THE MID LEVEL DIVERGENT ZONE WELL SOUTH OF THE AREA ALONG WITH
PRESSURE FALLS BEING LOCATED TO THE SE OF THE CLIPPER WHICH WILL
GUIDE IT SOUTHWARD. WITH THE CLIPPER TAKING A MORE SOUTHWARD
SHIFT...HAVE THUS ADJUSTED THE POPS/QPF AS WELL BUT SE MI IS NOT
TOTALLY OUT OF THE WOODS. SUNDAY MORNING THE COLD FRONT WILL STILL
BE DRAPED THROUGH THE AREA PROVIDING SOME WEAK FORCING IN THE SFC -
850MB LAYER. LOOKING ALOFT...THERE IS A SHEARING RIBBON OF VORTICITY
AND OMEGA WHILE ISENTROPIC ASCENT FLARES UP SOUTH OF ABOUT M59.
THIS MAY BE ENOUGH COMBINED FORCING TO PROMOTE SOME LIGHT MORNING
SNOW SHOWERS BUT MOISTURE CONTENT WILL BE TOO LOW TO AMOUNT TO MUCH.
BETTER MOISTURE...SPECIFIC HUMIDITY 3 G/KG...WITH STRONGER FRONTAL
FORCING TAKING PLACE SOUTH OF THE MI BORDER. WITH SOME OF THE
MOISTURE AND FORCING HOLDING OVER THE EXTREME SOUTH...WILL LEAVE
ABOUT AN INCH OF SNOW ACCUMULATIONS FOR LENAWEE AND MONROE
COUNTIES...TAPERING OFF QUICKLY TO THE NORTH. LOOKS LIKE THE DETROIT
METRO SHOULD SEE UP TO A HALF INCH OR SO...BUT ANY FURTHER SHIFT
SOUTHWARD COULD WARRANT DROPPING POPS COMPLETELY AS VERY DRY ARCTIC
AIR FILLS IN BEHIND THE COLD FRONT THROUGH THE AFTERNOON.

AFTER THE CLIPPER PASSES TO THE EAST SUNDAY NIGHT...THE STORY FOR
MONDAY WILL BE COOLER TEMPS AS ARCTIC AIR CONTINUES TO HOLD OVER THE
AREA. 850MB TEMPS WILL FALL TO BELOW -10C WITH NORTHERLY FLOW DURING
THE DAY. THIS COLUMN OF DRY AIR WILL EXTEND DOWN TO ABOUT 950MB SO
IF WE CAN SCOUR OUT THE LOW CLOUDS WE WILL SEE A FEW HOURS OF SUN
BEFORE THE CIRRUS DEBRIS AHEAD OF THE NET WAVE STARTS MOVING LATER
THAT EVENING. HIGH TEMPS WILL STRUGGLE TO REACH 20F ACROSS THE AREA
WITH LOWS DROPPING TO AROUND 10F.

THE REMAINDER OF THE EXTENDED FORECAST FEATURES A POSSIBLE SYSTEM ON
THURSDAY FOLLOWED BY COLDER AIR TAKING HOLD OVER THE REGION.  BY
TUESDAY...A LONGWAVE TROUGH WILL BE PUSHING OFF TOWARDS THE EAST
COAST AS RIDGING BUILDS IN AND HOLDS THROUGH WEDNESDAY.  THIS WILL
BRING QUIET CONDITIONS BEFORE A PERIOD OF MORE ACTIVE WEATHER
POTENTIALLY ARRIVES ON THURSDAY

MARINE...

A COLD FRONT DROPPING THOUGH LAKE HURON THIS AFTERNOON WILL TURN
WINDS FROM WESTERLY TO NORTHWESTERLY TONIGHT. WINDS WILL INCREASE
WITH COLDER UNSTABLE AIR...BUT WILL REMAIN BELOW 30 KNOTS. AS THE
FRONT CONTINUES TO DROP SOUTH ON SUNDAY...WINDS WILL CONTINUE TO
VEER AROUND TO THE NORTHEAST. WIND SPEEDS WILL DECREASE THROUGH THE
DAY SUNDAY AND OVERNIGHT AS HIGH PRESSURE BUILDS IN FROM THE NORTH.
THOUGH WINDS WILL GUST TO NEAR 25 KNOTS SUNDAY...EXTENSIVE ICE COVER
ON THE NEARSHORE WATERS WILL PREVENT ANY OF THE TYPICAL NORTHEAST
FLOW WAVE ISSUES ALONG THE SHORELINE. EARLY NEXT WEEK...CONDITIONS
WILL REMAIN RELATIVELY CALM WITH WIND GUSTS REMAIN AOB 20 KNOTS OVER
THE LAKE HURON OPEN WATERS AS SEVERAL HIGH PRESSURE CENTER BUILD
ACROSS THE AREA.

&&

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

$$

AVIATION.....MR
SHORT TERM...CB
LONG TERM....DRK/SS
MARINE.......DRK

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



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