Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 251821
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
121 PM EST SUN JAN 25 2015


.AVIATION...

MVFR STRATUS HELD THIS MORNING IN THE FACE OF INCREASING DRY AIR
ADVECTION. COVERAGE OF MVFR CIG OBS AT 17Z AND SOME SHALLOW LAKE
HURON MOISTURE MAKES IT DIFFICULT TO TOTALLY MOVE AWAY FROM BKN MVFR
CIGS BUT THE TREND IS DEFINITELY DRIER. WILL AMEND THIS AFTERNOON
AS NEEDED. CLIPPER SYSTEM IS NOW PUSHING INTO INDIANA. WILL
CONTINUE TO MONITOR THE NORTHERN EDGE OF THE PRECIPITATION
SHIELD...BUT ALL INDICATIONS ARE THE LIGHT SNOW WILL REMAIN SOUTH
OF THE DTW TERMINAL. THE TIME PERIOD OF PARTICULAR INTEREST FOR
PASSING SYNOPTIC SCALE FORCING WILL BE BETWEEN 21-02Z

//DTW THRESHOLD PROBABILITIES...

* HIGH IN CEILINGS BELOW 5000 FEET THROUGH THIS AFTERNOON.

* HIGH CONFIDENCE IN PRECIPITATION TYPE SNOW. LOW PROBABILITY
  THIS WILL AFFECT DTW.

&&

.PREV DISCUSSION...ISSUED 1108 AM EST SUN JAN 25 2015

UPDATE...

UPDATED THE GRIDDED FORECAST TO ACCOUNT FOR LIGHT SNOW THAT IS
BREAKING OUT OVER FAR SOUTHERN LOWER MICHIGAN.

AVAILABLE DATA SUGGESTS AN ELEVATED FRONTAL FEATURE IS SITUATED
BETWEEN 800-700MB OR THE 290K ISENTROPIC SURFACE SOUTH OF ANN
ARBOR AND DETROIT. WITH THIS THE CASE...REMNANT ANTICYCLONIC FLOW
TRAJECTORIES IN THE MIDLEVELS ARE LEADING TO SOME SYSTEM RELATIVE
ISENTROPIC ASCENT. MODELS SUGGEST FLOW TRAJECTORIES DEEPENING AND
OVERWHELMINGLY TRENDING CYCLONIC OR EASTERLY OVER THE NEXT COUPLE
OF HOURS...PRIOR TO 18Z. THIS WILL VANQUISH THE ASCENT AND ALLOW
DEEP DRY ARCTIC AIR TO BUILD SOUTH CLOSER TO THE MICHIGAN BORDER.
EXPECTING A RAZOR SHARP GRADIENT TO THE NORTHERN EDGE OF THE
SYNOPTIC CLIPPER SNOW THAT WILL SLIDE THROUGH LATER THIS
AFTERNOON. WITH CURRENT VSBYS BOUNCING AROUND IN THE LIGHT
SNOW...A HALF INCH TO AN INCH IS POSSIBLE PRIOR TO 18-19Z FOR
PORTIONS OF LENAWEE AND MONROE COUNTIES AHEAD OF THE CLIPPER
SYSTEM. SNOWFALL ACCUMULATIONS WITH THE CLIPPER LATER THIS
AFTERNOON...IS A LOWER CONFIDENCE FORECAST BECAUSE OF THE TIGHT
MOISTURE GRADIENT. WILL MONITOR THIS AFTERNOON...BUT AN ADDITIONAL
ONE HALF TO ONE INCH IS PROBABLE FOR
MORENCI...LAMBERTVILLE...TEMPERANCE BY 02Z.

PREV DISCUSSION...ISSUED 314 AM EST SUN JAN 25 2015

SHORT TERM...TODAY THROUGH TONIGHT

THE SHORT TERM PERIOD WILL BE DOMINATED BY THE INFLUENCE OF HIGH
PRESSURE CURRENTLY CENTERED BENEATH AN AREA OF CONFLUENT FLOW
ALOFT AND CENTERED OVER FAR NORTHWEST ONTARIO. NORTHEAST WINDS
AROUND THE PERIPHERY OF THIS HIGH HAVE BEGUN TO FILL INTO
SOUTHEAST MICHIGAN BEHIND THE COLD FRONT THAT IS MAKING ITS WAY
THROUGH THE CWA. AT 07Z, TEMPERATURES WERE IN THE MID 20S NORTH OF
I-69 WITH MID 30S TO THE SOUTH. THE FRONT WILL REACH THE OHIO
BORDER AROUND SUNRISE. ONGOING COLD ADVECTION IS FORECAST TO DROP
925MB TEMPERATURES FROM AROUND -2C AHEAD OF THE FRONT TO -12C
BEHIND THE FRONT BY THIS EVENING. AS A RESULT, HIGH TEMPERATURES
WILL OCCUR IN THE MORNING AT ALL LOCATIONS. INSOLATION WILL HELP
FALLING TEMPERATURES LEVEL OFF AROUND 20 DEGREES THIS AFTERNOON.

LOW-LEVEL DRY ADVECTION WILL INCREASE MARKEDLY THIS AFTERNOON INTO
THIS EVENING AS HIGH PRESSURE BUILDS INTO ONTARIO. THIS IS EXPECTED
TO FAVOR AN AN EROSION OF LOW CLOUDS FROM EAST TO WEST DURING THE
DAY. LIGHT SNOW SHOWERS ARE LIKELY NEAR THE OHIO BORDER AS THE H85
FRONT SAGS TO THE SOUTH AND CONTRACTS A BIT IN ADVANCE OF A SYSTEM
TRAVERSING THE OHIO VALLEY TODAY, BUT PROSPECTS FOR MEASURABLE
PRECIP ARE RATHER LOW. AT THIS TIME, LEFT LIKELY POPS CONFINED TO
ONLY THE FAR SOUTH WHERE A COUPLE TENTHS OF ACCUMULATION WILL BE
POSSIBLE. CLEARING TONIGHT AND AN EASING OF THE GRADIENT WITHIN THE
FRESH CANADIAN AIRMASS WILL ALLOW TEMPERATURES TO FALL INTO THE
SINGLE DIGITS BY MONDAY MORNING.

LONG TERM...MONDAY THROUGH SATURDAY

COLDER WEATHER WILL PERSIST INTO EARLY NEXT WEEK AS PASSING CLIPPER
PHASES INTO MAJOR EAST COAST STORM AND UPPER TROUGH OVER THE EASTERN
CONUS DEEPENS IN THE PROCESS. HIGHS ON MONDAY STILL LOOK TO HOLD AT
20F OF BELOW WITH LOWS IN THE SINGLE DIGITS TO LOWER TEENS. HEIGHTS
DO BEGIN TO RISE BY TUESDAY AS UPPER TROUGH SHIFTS EAST AS STRONG
LOW PRESSURE SYSTEM WRAPS UP ALONG THE EASTERN SEABOARD. THIS WILL
ALLOW FOR TEMPERATURES IN THE MID/UPPER 20S. DURING THIS TIME FRAME
ONLY A FEW PASSING FLURRIES AS EXPECTED AS SHORTWAVE ENERGY DIGS
INTO THE DEVELOPING UPPER TROUGH...NAMELY IN THE MONDAY NIGHT TIME
FRAME.

TEMPERATURES GRADUALLY MODERATE INTO THE WEDNESDAY AND TUESDAY
PERIOD AS MAIN UPPER TROUGH AXIS SHIFTS OFF THE EAST COAST AND
HEIGHTS OVER THE AREA RISE RATHER AS SHORTWAVE RIDGE BUILDS INTO THE
AREA IN ADVANCE OF NEXT NOTABLE CLIPPER SYSTEM. THIS WILL BRING BACK
INTO THE 30S DURING THE MIDDLE OF THE WEEK. THIS CLIPPER WILL ALSO
BRING THE NEXT CHANCE OF PRECIPITATION...MAINLY SNOW...BY THURSDAY.

ONCE THIS SYSTEM PASSES...COLDER WEATHER WILL AGAIN SETTLE IN OVER
THE GREAT LAKES FROM LATE WEEK INTO NEXT WEEKEND AS SOUTHERN EDGE OF
A MORE SIGNIFICANT ARCTIC AIRMASS BUILDS INTO THE NORTHEAST CONUS.
ADDITIONAL SNOW SHOWER CHANCES CAN ALSO BE EXPECTED AS A NUMBER OF
SHORTWAVES RACE THROUGH THE AREA ALONG THIS BOUNDARY BY THE END OF
THIS FORECAST PERIOD. HIGHS WILL ONCE AGAIN FALL BACK CLOSER TO 20F
WITH LOWS BACK INTO THE SINGLE DIGITS.

MARINE...

NORTH FLOW OVER LAKE HURON...BEHIND A PASSING COLD FRONT...WILL VEER
TO THE NORTHEAST TODAY AND TONIGHT AS HIGH PRESSURE SHIFTS ACROSS
ONTARIO. WINDS WILL INCREASE WITH THE COLDER UNSTABLE AIR...BUT WILL
REMAIN BELOW 30 KNOTS TODAY AND THEN DECREASE THIS EVENING INTO
TONIGHT.

WHILE NORTHEAST WINDS WILL GUST TO NEAR 25 KNOTS TODAY OVER THE NEAR
SHORE WATERS...EXTENSIVE ICE COVER WILL PREVENT ANY OF THE TYPICAL
WAVE ISSUES ASSOCIATED WITH MODERATE ONSHORE FLOW.HENCE...SMALL
CRAFT ADVISORIES WILL NOT BE NEEDED. EARLY NEXT WEEK...CONDITIONS
WILL REMAIN RELATIVELY CALM WITH WIND GUSTS REMAINING AOB 20 KNOTS
OVER THE LAKE HURON OPEN WATERS AS SEVERAL HIGH PRESSURE CENTERS
BUILD ACROSS THE AREA.

&&

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

$$

AVIATION.....CB
UPDATE.......CB
SHORT TERM...JVC
LONG TERM....DG
MARINE.......DG


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



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