Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 251731
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1231 PM EST WED FEB 25 2015


.AVIATION...

CLEAR SKIES BELOW 10KFT AND VARIABLE WINDS WILL DOMINATE THROUGH THE
DAYTIME HOURS AS HIGH PRESSURE AND DRY AIR REMAIN IN PLACE. CIGS
WILL THEN LOWER THROUGH THE EVENING AS LIGHT SNOW MOVES IN FROM THE
WEST. BORDERLINE MVFR IS EXPECTED FROM KPTK SOUTH WITH THE POTENTIAL
FOR IFR WITHIN ANY HEAVIER SNOW. COINCIDENT WITH THE APPROACH OF
LIGHT SNOW WILL BE AN INCREASE IN NORTHEAST WIND AS THE CENTER OF
LOW PRESSURE PASSES WELL SOUTH.

FOR DTW...LIGHT NATURE OF THE SNOW AND ANTECEDANT DRY AIR MAKE
PREDICTION OF ONSET TIME LOW CONFIDENCE. ATTM...MOST LIKELY START
TIME WILL BE AROUND 10Z, GRADUALLY TAPERING OFF BETWEEN 16-18Z.
SMALL FLAKE SIZE MAY CONTRIBUTE TO A HIGHER LIKLIHOOD OF IFR
VSBY...ESPECIALLY 12-15Z.

//DTW THRESHOLD PROBABILITIES...

* LOW FOR CEILING BELOW 5000 FT TODAY. HIGH LATE TONIGHT THROUGH
  THURSDAY MORNING.

&&

.PREV DISCUSSION...ISSUED 355 AM EST WED FEB 25 2015

SHORT TERM... TODAY THROUGH LATE TONIGHT

THE ARCTIC FRONT CLEARED THE OHIO BORDER SHORTLY BEFORE 4 AM LEAVING
LIGHT NORTHWEST WIND BEHIND OVER SE MICHIGAN. A NEW ROUND OF ARCTIC
COLD WILL THEN SETTLE OVER THE REGION DURING THE REST OF THE
MORNING...BUT THIS TIME IT WILL BE MORE OF A GLANCING BLOW COMPARED
TO RECENT DAYS. THE DIFFERENCE THIS TIME AROUND WILL BE DUE TO THE
RIDGE OF SURFACE HIGH PRESSURE BUILDING DIRECTLY OVERHEAD AND THEN
TO OUR NORTH BY EVENING WHICH WILL NEUTRALIZE LOW LEVEL COLD
ADVECTION BY AFTERNOON. A FEW LOCATIONS IN THE TRI CITIES AND
NORTHERN THUMB WILL START THE DAY AROUND ZERO WITH SINGLE DIGITS
EVERYWHERE ELSE...BUT THE ABBREVIATED COLD ADVECTION PATTERN AND
LATE FEBRUARY SUN WILL THEN ALLOW READINGS TO RECOVER INTO THE TEENS
MOST LOCATIONS BY LATE AFTERNOON. AN INCREASE OF THIN CIRRUS IS
LIKELY DURING THE AFTERNOON AND SOME PATCHY STRATOCU IS POSSIBLE BUT
NEITHER SHOULD CUT MUCH INTO DAYTIME HEATING.

HIGH CLOUDS WILL BECOME MORE SUBSTANTIAL DURING THE EVENING AS THE
NEXT WAVE OF LOW PRESSURE APPROACHES FROM THE CENTRAL PLAINS. THIS
SYSTEM IS OBSERVED IN SATELLITE IMAGERY EXITING THE CENTRAL ROCKIES
DURING THE MORNING AND IS EXPECTED TO RIPPLE ALONG THE ARCTIC FRONT
AS IT SETTLES INTO THE OHIO VALLEY. THE UPPER WAVE WILL BRING A
THICK MID CLOUD DECK UP TO AT LEAST THE I-96 CORRIDOR BY SUNSET
WHICH WILL SPREAD TO THE NORTHEAST OVER THE REST OF SE MICHIGAN
ROUGHLY BY MIDNIGHT. EXPECT LOW TEMPERATURES THEN TO OCCUR AROUND
MIDNIGHT RANGING FROM ZERO TO 5 ABOVE SOUTH OF M-59 AND FROM ZERO TO
5 BELOW TOWARD THE TRI CITIES AND NORTHERN THUMB. READINGS WILL THEN
RESPOND UPWARD WITH THE CLOUD COVER AND BE IN THE SINGLE DIGITS
EVERYWHERE BY SUNRISE. THIS WILL PREVENT WIND CHILL FROM DROPPING
BELOW -15 FOR MORE THAN AN HOUR OR TWO AS NORTHEAST WIND INCREASES
INTO THE 5 TO 10 MPH RANGE LATE.

LONG TERM...LATE TONIGHT THROUGH TUESDAY

EAST-WEST ORIENTATED SHORTWAVE TROUGH AXIS SEEN ON WATER VAPOR OVER
NORTHERN ALBERTA AND SASKATCHEWAN WILL DROP INTO THE GREAT LAKES
TONIGHT AND THURSDAY AS IT ROTATES DOWN THE BACKSIDE OF THE UPPER
VORTEX OVER EASTERN CANADA. THE TROUGH WILL BECOME POSITIVELY TILTED
AS IT MOVES OUR WAY..STRETCHING FROM QUEBEC TO IOWA BY THURSDAY
EVENING. ELEVATED PORTION OF THE FRONTAL BOUNDARY THAT JUST DROPPED
THROUGH LOWER MICHIGAN WILL MEANWHILE STALL OVERHEAD AND REMAIN
THERE THROUGH THURSDAY BEFORE GETTING KICKED EAST. LIFT WILL
INCREASE LATE TONIGHT AND TOMORROW ALONG THIS BOUNDARY AS THE UPPER
TROUGH APPROACHES...PRIMARILY FROM THE M-59 CORRIDOR SOUTHWARD.
FORCING LOOKS TO MAINLY BE LOCATED IN THE MID-LEVELS...WITH MODELS
SHOWING THE NEED TO REACH THE 290-295K ISENTROPIC SURFACES FOR
ASCENT. CROSS-SECTIONS DO ALSO SHOW A VERY WEAK FGEN LAYER BETWEEN
700-600MB CLOSER TO THE OHIO BORDER. OVERALL...LIFT WILL NOT BE TOO
STRONG ALONG THIS BOUNDARY LATE TONIGHT AND TOMORROW...AND WITH
SPECIFIC HUMIDITIES ONLY REACHING AROUND 1 G/KG...EXPECTING SNOWFALL
TO BE LIGHT. LATEST FORECAST CARRIES UP TO ABOUT 0.5 INCHES OF
SNOW...WITH HIGHEST AMOUNTS NEAR THE OHIO BORDER. COLDER AIR WILL
CONTINUE TO SEEP INTO THE AREA TOMORROW WITH THE PASSAGE OF THE
UPPER TROUGH AXIS AND AS THE FRONT CONTINUES TO DROP SOUTH. ONLY
EXPECT MAX TEMPS TO REACH INTO THE LOW TEENS AT BEST THURSDAY.
OVERNIGHT LOWS WILL AGAIN BE VERY COLD...REACHING DOWN NEAR RECORDS
OF -5 TO -15 BELOW ZERO. WINDS WILL BE LIGHT AS HIGH PRESSURE BUILDS
IN BEHIND THE UPPER TROUGH. THIS SHOULD MINIMIZE EFFECT FROM WIND
CHILL...BUT AN ADVISORY COULD STILL BE NEEDED.

RECORDS LOW MAX TEMPS (LOWEST HIGHS) FOR FEB 26
DETROIT AREA:  9 (1900)
FLINT AREA:    9 (1963)
SAGINAW:      11 (1963)

RECORD LOWS FOR FEB 27
DETROIT AREA: -4  (1934)
FLINT AREA:   -14 (1994)
SAGINAW:      -8  (1934)

ONLY A SLOW MODERATION IN TEMPERATURES IS EXPECTED FOR FRIDAY AND
SATURDAY AS HIGH PRESSURE CENTERED OVER THE OHIO VALLEY ENCOMPASSES
THE AREA. THE INFLUENCE OF THE HIGH WILL ALSO KEEP WINDS LIGHT AND
THE WEATHER QUIET.

DEEPENING SOUTHERLY FLOW OVER THE CENTRAL AND EASTERN PART OF THE
CONUS WILL OCCUR BY SUNDAY AS UPPER TROUGHING DEVELOPS OVER THE WEST
COAST. THIS WILL LIFT THE MID-LEVEL BAROCLINIC ZONE UP INTO THE
GREAT LAKES. ENERGY EJECTING OUT OF THE UPPER TROUGH OVER THE WEST
AND NORTHERN STREAM TROUGHING WILL THEN RIDE OVER THE TOP OF THE
FRONTAL FEATURE...WRINGING OUT MOISTURE AND PERHAPS PROVIDING SOME
SNOW TO THE AREA SUNDAY AND SUNDAY NIGHT. RELEVANT UPPER FEATURES
HAVE YET TO BE SAMPLED BY THE UPPER AIR NETWORK...AND MODELS HAVE
BEEN JUMPING AROUND A BIT WITH THEIR SOLUTIONS. PREVIOUS RUNS OF THE
GFS/EURO/GEM ALL TOOK A JOG TO THE SOUTH WITH THE LOCATION OF THE
FRONT AND THE PRECIPITATION SHIELD...AS THEY SHOWED A STRONGER AND
MORE AMPLIFIED NORTHERN STREAM TROUGH PUSHING ACROSS THE GREAT
LAKES. 00Z RUNS OF THE GFS AND EURO DID JUMP BACK NORTHWARD A LITTLE
BIT...BUT ARE NOT SHOWING AS HIGH OF QPF AMOUNTS AS THEY DID 24
HOURS AGO. STILL PLENTY OF TIME TO WATCH THIS SYSTEM DEVELOP...BUT
IT COULD PROVIDE ACCUMULATING SNOWFALL TO AT LEAST THE SOUTHERN PART
OF THE FORECAST AREA. AMOUNTS DO NOT LOOK TERRIBLY HEAVY HOWEVER.

MARINE...

SURFACE HIGH PRESSURE WILL BUILD OVER THE GREAT LAKES TODAY AND
BRING A PERIOD OF FAVORABLE MARINE CONDITIONS...AT LEAST IN TERMS OF
WIND...THAT WILL LAST FOR THE REST OF THE WEEK. THE ONLY WEATHER
CONDITIONS OF NOTE WILL BE THE CONTINUATION OF ARCTIC AIR INFLUENCE
KEEPING TEMPERATURES ROUGHLY 30 DEGREES BELOW NORMAL UNTIL SOME
MODEST RECOVERY OCCURS DURING THE WEEKEND.

&&

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

$$

AVIATION.....JVC
SHORT TERM...BT
LONG TERM....HLO
MARINE.......BT


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



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