Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000
FXUS63 KDTX 291731
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
131 PM EDT WED OCT 29 2014


.AVIATION...

//DISCUSSION...

EXPECTING BROKEN CEILINGS TO STICK AROUND THROUGH THE AFTERNOON
ACROSS ALL THE TAF SITES. WIND GUSTS ARE ALSO EXPECTED TO REACH UP
TO 20 TO 25 KNOTS THIS AFTERNOON. WEAK SURFACE RIDGING OVERNIGHT WILL
ALLOW WINDS TO DIMINISH AND CLOUDS TO THIN SLIGHTLY AS DRIER AIR
FILTERS OVER THE REGION. HOWEVER...EVEN WITH THE DRY AIR FILTERING
IN TONIGHT...WILL STILL EXPECT AT LEAST SCATTERED CLOUD DECK TO
REMAIN ACROSS SOUTHEAST MICHIGAN. CLOUDS BEGIN TO BUILD BACK OVER
THE AREA LATE TOMORROW MORNING AS THE NEXT DISTURBANCE ARRIVES.

//DTW THRESHOLD THREATS...

* MODERATE PROBABILITY THAT CEILINGS WILL REMAIN BELOW 5000 FT
  BETWEEN 18Z WEDNESDAY AND 00Z THURSDAY.

* LOW CONFIDENCE THAT CEILINGS WILL DROP BELOW 5000 FT THURSDAY
  AFTERNOON.

&&

.PREV DISCUSSION...ISSUED 352 AM EDT WED OCT 29 2014

SHORT TERM...TODAY AND TONIGHT

DESPITE THE PASSAGE OF A COLD FRONT YESTERDAY...COLD AIR ADVECTION
WILL CONTINUE TODAY AS A LOW LEVEL TROUGH TURNS 850 MB WINDS FROM A
WESTERLY TO A NORTHWESTERLY DIRECTION...FURTHER DROPPING 850 MB
TEMPERATURES INTO THE SINGLE DIGITS BELOW ZERO. SKIES THIS MORNING
WILL START OUT AS PARTLY TO MOSTLY CLOUDY...DEPENDING ON LOCATION AS
THERE ARE CURRENTLY SEVERAL BREAKS IN THE CLOUDS. SKIES SHOULD
QUICKLY BECOME BROKEN TO OVERCAST LATER THIS MORNING AS COLD AIR
ALOFT...LINGERING 850 MB MOISTURE AND CONTINUED CYCLONIC FLOW CREATE
CONDITIONS CONDUCIVE FOR A PRETTY SOLID DECK OF STRATOCUMULUS TO
FORM. THE CONTINUED COLD AIR ADVECTION AND ABUNDANT CLOUD COVER WILL
SEVERELY LIMIT THE DIURNAL RANGE IN TEMPERATURES AS HIGHS ONLY TOP
OUT AROUND 50 DEGREES THIS AFTERNOON.

WITH THE LOSS OF DAYTIME HEATING THE DIURNALLY DRIVEN CLOUDS WILL
DISSIPATE AS DRIER AIR AND SURFACE RIDGING BUILD IN FROM
THE WEST. HOWEVER A COMPLETE CLEARING IS NOT EXPECTED AS 850 MB
MOISTURE REMAINS OVER THE CENTRAL GREAT LAKES WITH NORTHWEST FLOW
ALOFT. THE AFOREMENTIONED RIDGING WILL CAUSE SURFACE WINDS TO
BECOME LIGHT...THIS COMBINED WITH SOME BREAKS IN THE CLOUDS WILL
CAUSE OVERNIGHT LOWS TO FALL INTO THE LOWER TO MIDDLE 30S ACROSS
SOUTHEAST MICHIGAN.

LONG TERM...

STRONG POLAR PV ANOMALY DESCENDING FROM THE NORTHWEST
TERRITORIES/NUNAVUT TODAY...AND DROPPING SOUTH THROUGH THE AREA ON
FRIDAY...DELIVERING THE FIRST SNOWFLAKES OF THE FALL SEASON TO
SOUTHEAST MICHIGAN. STILL NEED TO TO FINE TUNE EXACT TRACK OF
DEVELOPING 500 MB LOW CENTER WHICH WILL DICTATE SYNOPTIC SUPPORT OF
PRECIPITATION VS MESOSCALE LAKE EFFECT OFF LAKE HURON. A LOOKED AT
THE STANDARDIZED ANOMALIES OF 500 MB HEIGHTS AND 850 MB TEMPS DOES
NOT SHOW ANYTHING TERRIBLY UNUSUAL (-1.5)/NON-RECORD BREAKING...AND
THUS MAKING THIS A VERY DIFFICULT FORECAST IN DETERMINING WHAT IF
ANY SNOW ACCUMULATIONS WILL OCCUR. NEGATIVES FOR THE EVENT INCLUDE
THE UNFAVORABLE AFTERNOON TIMING...WARM MARINE LAYER/WATERS OF LAKE
HURON (LOWER 50S)...AND WARM GROUND (SOIL TEMPS 45-50). WILL BE
TRUSTING THE SURFACE/NEAR SURFACE PROFILES OF THE 00Z
NAM/EURO/CANADIAN...WHICH OBVIOUSLY ARE SUBJECT TO BE IN
ERROR/REVISED. THIS GUIDANCE SUGGEST SURFACE TEMPERATURES
REMAINING ABOVE FREEZING THROUGH 00Z SATURDAY...ALTHOUGH EURO HAS
THE BEST SUPPORT FOR SNOW AS SURFACE WET BULB TEMPS FALL BELOW
FREEZING ALONG AND WEST OF U.S. 23 BY 00Z SATURDAY. EVEN DURING THE
EVENING...THE LOW LEVEL NORTHEAST WINDS OF LAKE HURON LOOK TO KEEP
EASTERN HALF OF THE CWA ABOVE FREEZING. THROW IN THE FACT THE GFS IS
STRONGER/MILDER AND FARTHER WEST (ALTHOUGH PREFERENCE IS WITH
EURO/CANADIAN SOLUTIONS)...AND WILL SKEW THE FORECAST ON THE WET
SIDE FOR MOST OF FRIDAY...WITH STILL SOME SNOW MIXING IN/CHANGING
OVER TOWARD SUNSET...AS 850 MB TEMPS FALL INTO THE -8 TO -10 C
RANGE. BETTER CHANCE OF ACCUMULATING SNOW SHOWERS FRIDAY NIGHT AS
LAKE EFFECT LIKELY PERSISTS AND LOW LEVEL COLDER AIR CONTINUES TO
BLEED IN UNDER NIGHT-TIME SETTING. EXTENSION OF THE IRISH
HILLS/HIGHER TERRAIN THE FAVORED LOCATIONS FOR LIGHT SNOW
ACCUMULATIONS.

SATURDAY IS A TRICKY FORECAST AS WELL...AS WE WILL BE ON THE WESTERN
EDGE OF THE LARGE UPPER LEVEL CIRCULATION. WITH LOW LEVEL FLOW STILL
OUT OF THE NORTHEAST...AND COLD AIRMASS (NEGATIVE MID TO UPPER
SINGLES AT 850 MB)...LIKELY WILL SEE ADDITIONAL SCATTERED SNOW/RAIN
SHOWERS AROUND...ESPECIALLY DURING MORNING HOURS.

MARINE...

SOUTHWEST WINDS OF 15 TO 25 KNOTS TODAY WILL GRADUALLY EASE AND
SHIFT TO THE NORTHWEST TONIGHT...BECOMING LIGHT ON THURSDAY. THIS
LULL IN THE WINDS WILL BE SHORT LIVED...AS AN ARCTIC FRONT PASSES
THROUGH THE CENTRAL GREAT LAKES ON FRIDAY. NORTHERLY GUSTS TO GALES
APPEAR LIKELY FRIDAY AFTERNOON INTO FRIDAY NIGHT OVER THE SOUTHERN
TWO THIRDS OF LAKE HURON DURING THIS TIME WITH SIGNIFICANT WAVE
HEIGHTS OF 5 TO 10 FEET OVER SOUTHERN LAKE HURON. HAVE GONE AHEAD
AND ISSUED GALE WATCHES WITH THIS FORECAST PACKAGE. ALTHOUGH WINDS
WILL GRADUALLY DIMINISH ON SATURDAY...THE NORTHEAST WIND DIRECTION
WILL MAINTAIN HIGHER WAVES ALONG NEARSHORE WATERS. HIGH PRESSURE
BUILDING IN ON SUNDAY WILL ASSURE LIGHT WINDS.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...GALE WATCH FROM FRIDAY MORNING THROUGH SATURDAY MORNING FOR LHZ362-
     363-462.

     GALE WATCH FROM FRIDAY AFTERNOON THROUGH SATURDAY MORNING FOR
     LHZ463-464.

     SMALL CRAFT ADVISORY UNTIL 4 PM EDT THIS AFTERNOON FOR LHZ421-422-
     441.

LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
&&

$$

AVIATION.....RK
SHORT TERM...KURIMSKI
LONG TERM....SF
MARINE.......SF


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



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