Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 192017
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
317 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...

THE ACTIVE MARINE WEATHER PATTERN CONTINUES TONIGHT INTO THURSDAY AS
A LOW PRESSURE SYSTEM DEVELOPING OVERHEAD TODAY USHERS IN THE NEXT
ARCTIC SURGE TONIGHT INTO THURSDAY. THIS WILL AGAIN BRING GUSTY
WESTERLY WINDS TO THE EASTERN LAKES. THE SETUP DOES NOT LOOK QUIET
AS POTENT AS THIS PAST EVENT BUT WIDESPREAD GALE FORCE WINDS APPEAR
LIKELY ACROSS MUCH OF THE LAKE HURON BASIN. BEING ALMOST A FULL 24
HOURS OUT YET...CHOSE TO ISSUE A GALE WATCH AT THIS POINT. HAVE ALSO
ALLOWED CURRENT SMALL CRAFT ADVISORIES AND LOW WATER ADVISORY TO
END...AND CANCELLED THE SMALL CRAFT FOR THE OUTER SAGINAW BAY AREA
AS WAVES HAVE FALLEN BELOW CRITERIA.

&&

.AVIATION...ISSUED 1203 PM EST WED NOV 19 2014

//DISCUSSION...

BRIEF PERIOD OF IFR WILL ACCOMPANY THE BAND OF MODERATE SNOW LIFTING
ACROSS THE AREA AT FORECAST ISSUANCE TIME. VSBYS HAVE GENERALLY BEEN
IN THE 3/4SM TO 1SM RANGE WITH THIS BAND. UPON ITS DEPARTURE TO THE
NORTHEAST, CONDITIONS WILL IMPROVE AND CEILINGS WILL MAY EVEN LIFT
TO VFR FOR A BRIEF TIME BEFORE DEVELOPING WESTERLY FLOW POST-00Z
ALLOWS DEEPER/LAKE ENHANCED MOISTURE TO FILL BACK INTO THE AREA
OVERNIGHT. LAKE EFFECT SNOW SHOWERS WILL POTENTIALLY IMPACT
KPTK/KFNT OVERNIGHT WITH NOTHING MORE THAN MINOR ACCUMULATION.
FLURRIES ELSEWHERE. SSW WINDS GUSTING TO 18 TO 25 KTS TODAY WILL
VEER TO WESTERLY WITH THE PASSAGE OF THE COLD FRONT THIS EVENING.
COLD ADVECTION WILL ENSURE THE BOUNDARY LAYER REMAINS WELL-MIXED AND
GUSTS OF 25 KTS CONTINUE THROUGH THE NIGHT.

FOR DTW...THE PRIMARY BAND OF ACCUMULATING SNOW HAS LIFTED NORTH OF
THE AIRPORT AT THIS TIME. CONDITIONS WILL NOW GRADUALLY IMPROVE
THROUGH THE EARLY AFTERNOON. THE TRANSITION FROM SW TO W WINDS WILL
TAKE PLACE AROUND 00Z.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CEILINGS BELOW 5KFT/

* HIGH CONFIDENCE IN PTYPE OF SNOW.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...GALE WARNING FROM 7 PM THIS EVENING TO 11 PM EST THURSDAY FOR
     LHZ362-363-421-441-462>464.

     SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 11 PM EST THURSDAY
     FOR LHZ442-443.

     GALE WARNING FROM 10 PM THIS EVENING TO 1 PM EST THURSDAY FOR
     LHZ361.

     SMALL CRAFT ADVISORY UNTIL 7 PM EST THIS EVENING FOR LHZ421-422.

     GALE WARNING FROM 7 PM THIS EVENING TO 1 PM EST THURSDAY FOR LHZ422.

LAKE ST CLAIR...SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 4 PM EST THURSDAY
     FOR LCZ460.

MICHIGAN WATERS OF LAKE ERIE...SMALL CRAFT ADVISORY FROM 7 PM THIS EVENING TO 4 PM EST THURSDAY
     FOR LEZ444.

&&

$$

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


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



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