Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 192051
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
351 PM EST WED NOV 19 2014

.SHORT TERM...TONIGHT

THIS MORNING`S SNOW WHICH WAS FOCUSED PRIMARILY ALONG THE SYSTEM
WARM FRONT HAS DEPARTED TO THE NORTHEAST. AFTER A BRIEF LULL IN
ACTIVITY, ONGOING WARM ADVECTION AND ISENTROPIC ASCENT IN ADVANCE OF
THE APPROACHING COLD FRONT HAS ALLOWED WIDESPREAD LIGHT SNOW TO
REDEVELOP ACROSS MUCH OF THE LOWER PENINSULA DURING THE MID-
AFTERNOON HOURS WITH SOME LAKE ENHANCEMENT FURTHER UPSTREAM. FORCING
IS NOT GOING ANYWHERE, SO EXPECT THIS ACTIVITY TO HOLD TOGETHER AS
THE COLD FRONT WORKS THROUGH AROUND 00Z THIS EVENING. AN ADDITIONAL
DUSTING TO A HALF INCH WILL POSSIBLE DURING THIS TIME.

IN ADDITION, REGIONAL RADAR MOSAIC STRONGLY SUGGESTS THAT THE THE
12Z SUITE HAS BEEN TOO AGGRESSIVE WITH DEPICTIONS OF COLD ADVECTION
THIS AFTERNOON. WIDESPREAD SNOW SHOWERS ARE ONGOING OVER WISCONSIN
AND ARE OVERSPREADING LAKE MICHIGAN AT 19Z THIS AFTERNOON. AS IT
TURNS OUT, BOUNDARY LAYER MOISTURE IS MORE THAN SUFFICIENT TO
SUSTAIN A SUPERSATURATED DGZ AT THE TOP OF THE BOUNDARY LAYER.
CERTAINLY THERE IS NO EXPECTATION FOR THIS TO CHANGE AS COLD
ADVECTION RAMPS UP OVER SOUTHEAST MICHIGAN THIS EVENING. H85
TEMPERATURES ARE PROGGED TO FALL FROM -9C THIS AFTN TO -16C THURSDAY
MORNING. THE MIXED CONDITIONS WILL NOT ONLY SUPPORT CONTINUED WIND
GUSTS TO 20-25 KTS THROUGH THE NIGHT BUT ALSO WIDESPREAD
FLURRIES/SNOW SHOWERS THROUGH AT LEAST THE FIRST HALF THE NIGHT
BEFORE MOISTURE QUALITY BEGINS TO DEGRADE. THOUGH THERE IS SOME
CONCERN THAT SUBSIDENCE IN THE WAKE OF TODAY`S WAVE MAY ACT AS A
COUNTER TO THE EASTWARD PROGRESSION OF SNOW SHOWERS, 0-1KM THETA-E
LAPSE RATES OVER LAKE MICHIGAN OF -7C IS SUFFICIENT TO EXPECT A
SUBSTANTIAL COMPONENT OF LAKE ENHANCEMENT. NOT OUT OF THE QUESTION
AT ALL TO SEE ANOTHER DUSTING TO HALF INCH AS THIS ACTIVITY MOVES
THROUGH AS WELL. RAISED POPS ACROSS THE BOARD, AND THOUGH DID NOT
RAMP ALL LOCATIONS UP TO LIKELY POPS, DID ELECT TO USE
SCATTERED/NUMEROUS WORDING IN LIEU OF PROBABILISTIC.

THUS, TAKING INTO ACCOUNT ADDITIONAL WARM SECTOR SNOW THIS AFTN,
ADDITIONAL EVENING/OVERNIGHT ACCUMULATION SHOULD RANGE FROM A
DUSTING TO AN INCH AREAWIDE. THE RELATIVELY STRONG PRESSURE GRADIENT
MAY INHIBIT MUCH IN THE WAY OF ORGANIZATION OF LAKE EFFECT BANDS
INTO THE FAVORED I-69/I-94 CORRIDOR, AN IDEA THAT IS SUPPORTED BY
NAM12 DEPICTIONS OF POOR BOUNDARY LAYER CONVERGENCE IN THIS ZONE.
HOWEVER, COULD STILL SEE A COUPLE OF LOCALLY HIGHER AMOUNTS NEAR 2"
HERE. THE LAKE-MODIFIED AIRMASS AND MIXED CONDITIONS WILL CONTAIN
LOWS TO AROUND 20 DEGREES.

&&

.LONG TERM...THURSDAY THROUGH NEXT WEDNESDAY

A REINFORCING SHOT OF ARCTIC AIR WILL INFILTRATE LOWER MI ON
THURSDAY AS AN UPPER TROUGH AND ASSOCIATED SURFACE LOW ADVANCE FROM
THE NORTHERN GREAT LAKES INTO SRN QUEBEC. THE CORE OF COLDEST AIR
WITH THIS SYSTEM WILL TRACK INTO THE NRN GREAT LAKES THURS AND THURS
NIGHT. EVEN WITH SOME MODIFICATION OFF LAKE MI...850MB TEMPS ARE
EXPECTED TO DROP TOWARD -17C THURS AFTERNOON.

RESIDUAL LAKE EFFECT SNOW SHOWERS WILL ADVANCE INTO SE MI UNDER GOOD
WESTERLY FLOW...LIMITED AT LEAST IN THE EARLY PORTION OF THE DAY BY
A DRY AMBIENT AIRMASS OVER SE MI. A CORE OF COLDER MID LEVEL TEMPS
WILL TRACK ACROSS LOWER MI THURS AFTERNOON...ASSOCIATED WITH THE MID
LEVEL TROUGH. THIS WILL DEEPEN LAKE INDUCED INVERSION HEIGHTS. THE
UPPER TROUGH IS ALSO EXPECTED TO DRIVE A LITTLE BETTER MID LEVEL
MOISTURE TOWARD THE SOUTHERN SECTIONS OF LAKE MI. THE RESULT WILL BE
AN INCREASE IN THE LAKE RESPONSE. HI RES MODEL SOLUTIONS SUGGEST AN
ENHANCED RIBBON OF LOW LEVEL CONVERGENCE WILL SET UP BETWEEN THE
I-94 AND M-59 CORRIDORS...TARGETING THESE REGIONS FOR THE BETTER
CHANCES OF HIGHER INTENSITY SNOW SHOWERS. A WEAKENING WIND FIELD
DURING THE EVENING MAY LEAD TO THE ESTABLISHMENT OF SOME STRONGER
BANED CONVECTION EXTENDING INTO SE MI. THE LOW LEVEL FLOW WILL
HOWEVER GRADUALLY VEER FROM W TO NW DURING THE NIGHT...SHUNTING THE
BETTER CONVERGENCE TOWARD THE OHIO BORDER LATE THURS NIGHT. SO AT
THIS POINT...ANY ACCUMULATIONS SHOULD BE MINOR. THE COLD AIR
ADVECTION UNDER THE WESTERLY GRADIENT WILL SUPPRESS THURS HIGHS TO
THE LOW-MID 20S...WHILE WIND CHILLS REMAIN IN THE SINGLE DIGITS. A
MORE NW WIND TRAJECTORY THURS NIGHT WILL OFFER SOME CLEARING
POTENTIAL...SUGGESTING SOME LOCALS MAY SEE ACTUAL AIR TEMPS DROP
INTO THE SINGLE DIGITS.

THE CORE OF ARCTIC AIR WILL BEGIN EXITING THE GREAT LAKES FRIDAY
INTO SATURDAY AS THE UPPER LOW ROTATES INTO NE CANADA. THE POOL OF
SHALLOW ARCTIC WILL LINGER INTO FRI NIGHT...SO TEMPS WILL REMAIN
WELL BELOW MID NOV NORMS. LOW LEVEL WARM AIR ADVECTION UNDER
STRENGTHENING SW FLOW FRI NIGHT WILL BOOST THE LOW LEVEL WARMING
ALOFT /WITH 925MB TEMPS FORECAST TO RISE ABOVE FREEZING BY 12Z SAT/.
ALL MODEL SOLUTIONS SUGGEST THE ISENTROPIC ASCENT WILL BE ENOUGH TO
MOISTEN THE COLUMN...SUPPORTING SOME LIGHT PRECIP EARLY SAT MORNING
INTO SAT AFTERNOON. THERE IS CERTAINLY SOME CONCERN THAT MODEL
SOLUTIONS ARE MOISTENING THE LOW LEVEL TOO QUICKLY WITHIN THE
RETREATING ARCTIC AIRMASS. NONETHELESS...MODEL SOLUTIONS SUGGEST
SOME SEMBLANCE OF AN EMBEDDED MID LEVEL SHORT WAVE IMPULSE LIFTING
ACROSS THE REGION FROM THE SW. THIS REMAINS SUPPORTIVE OF A CHANCE
OF LIGHT PRECIP SAT. SFC TEMPS HOWEVER WILL NOT RISE ABOVE FREEZING
UNTIL SAT AFTERNOON...THUS THERE REMAINS A CHANCE FOR SOME LIGHT
FREEZING RAIN SAT MORNING.

SUNDAY WILL BE FAIRLY MILD AS COMPARED TO PREVIOUS DAYS WITH 850 MB
TEMPERATURES IN THE +5 TO +7 DEGREE RANGE. THIS WILL RESULT IN
SURFACE HIGH TEMPERATURES RANGING FROM THE MID TO UPPER 40S. WARM
AIR ADVECTION WILL CONTINUE INTO MONDAY WITH HIGHS ONCE AGAIN IN THE
MID TO UPPER 40S. IN ADDITION TO THE WARM AIR...A LOW PRESSURE
SYSTEM WILL TRACK FROM THE CENTRAL PLAINS INTO THE WESTERN GREAT
LAKES ON SUNDAY NIGHT AND MONDAY. THE PERIOD OF WARM AIR FILTERING
INTO THE REGION WILL RESULT IN PRECIPITATION BEING ENTIRELY IN
LIQUID FORM /RAIN/ THROUGH MONDAY. AS COLDER AIR FILTERS IN ON
MONDAY NIGHT...PRECIPITATION WILL CHANGE OVER TO A RAIN SNOW MIX FOR
THE OVERNIGHT HOURS AND EVENTUALLY ALL SNOW BY TUESDAY MORNING. WEAK
MID LEVEL RIDGING WILL ALLOW SOUTHEAST MICHIGAN TO DRY OUT FOR
WEDNESDAY AND THURSDAY...HOWEVER WITH COLD AIR STILL STREAMING IN
EXPECT TEMPERATURES TO BE BELOW AVERAGE THROUGH THURSDAY.

&&

.MARINE...

A NEW ROUND OF GALE FORCE WINDS WILL COMMENCE THIS EVENING AND
PERSIST THROUGH MUCH OF FRIDAY ON LAKE HURON. LOW PRESSURE WILL
DEEPEN AS IT TRACKS TO THE EAST OF LAKE HURON TONIGHT. THE
STRENGTHENING GRADIENT WILL FORCE ANOTHER ROUND OF ARCTIC AIR ACROSS
THE GREAT LAKES. WHILE WINDS ARE NOT EXPECTED TO BE AS STRONG AS
EARLIER IN THE WEEK...WESTERLY GALE FORCE GUSTS UP TO 40 KNOTS STILL
LOOK PROBABLE OVER THE OPEN WATERS OF LAKE HURON. WINDS WILL BACK
TOWARD THE SOUTHWEST FRI INTO FRI NIGHT AS HIGH PRESSURE DRIFTS TO
THE EAST COAST. ALTHOUGH CONDITIONS WILL REMAIN HIGHLY UNSTABLE OVER
LAKE HURON INTO SAT MORNING...THE GRADIENT AND WINDS IN THE MIXED
LAYER SUGGEST WINDS WILL REMAIN BELOW GALE FORCE.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...GALE WARNING UNTIL 3 AM EST FRIDAY FOR LHZ362-363-421-441-462>464.

     SMALL CRAFT ADVISORY UNTIL 11 PM EST THURSDAY FOR LHZ442-443.

     GALE WARNING FROM 10 PM THIS EVENING TO 7 PM EST THURSDAY FOR
     LHZ361.

     GALE WARNING UNTIL 1 PM EST THURSDAY FOR LHZ422.

LAKE ST CLAIR...SMALL CRAFT ADVISORY UNTIL 11 PM EST THURSDAY FOR LCZ460.

MICHIGAN WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY UNTIL 11 PM EST THURSDAY FOR LEZ444.

&&

$$

SHORT TERM...JVC
LONG TERM....SC/RK
MARINE.......SC
AVIATION.....JVC


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