Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 232302
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
702 PM EDT THU APR 23 2015


.AVIATION...

VFR CONDITIONS WILL PREVAIL WITH SCT-BKN 4000-5000 FOOT DECK ERODING
EARLY IN THE FORECAST...LEAVING MAINLY CLEAR SKIES UNTIL LATE IN THE
FORECAST PERIOD WHEN MID/UPPER LEVEL CLOUDS AOA 12KFT BEGIN TO
THICKEN. NORTHWEST WINDS WILL SWING TO THE NORTHEAST AT THE END OF
THE FORECAST AS WELL AS A FRONTAL BOUNDARY SOUTH OF THE TERMINALS
BECOMES BETTER DEFINED AS LOW PRESSURE LIFTS INTO THE MIDWEST.

//DTW THRESHOLD PROBABILITIES...

* MEDIUM CONFIDENCE IN CEILINGS AT OR BELOW 5000 FT THROUGH 01Z-
  02Z.

&&

.PREV DISCUSSION...ISSUED 331 PM EDT THU APR 23 2015

SHORT TERM...THROUGH TONIGHT

UPPER LOW WILL CONTINUE TO TRACK EAST THROUGH EASTERN CANADA AND NEW
ENGLAND TONIGHT. THIS WILL ALLOW DEEPER MOISTURE CIRCULATING AROUND
THIS SYSTEM TO GRADUALLY PULL EAST AND OUT OF THE CENTRAL GREAT
LAKES TONIGHT AS WELL. UNTIL THEN...STRATUS DECK WILL REMAIN LOCKED
INTO PLACE BENEATH AN INVERSION SHOWN ON 12Z DTX/APX RAOBS BETWEEN
4500-5500 FEET.

RIDGING AT THE SURFACE AND ALOFT WILL USHER IN DRIER AIR
OVERNIGHT...WHILE ALSO DECREASING FLOW OVER LAKE MICHIGAN AND
WEAKENING THE EXISTING INVERSION. EXPECTING SKIES TO CLEAR FROM WEST
TO EAST...A TREND WHICH CAN ALREADY BE SEEN OVER THE WESTERN GREAT
LAKES ON SATELLITE IMAGERY. GOOD RADIATIONAL COOLING CONDITIONS WILL
THEN SET UP OVERNIGHT AS THE SURFACE RIDGE AXIS BECOMES CENTERED
OVERHEAD. COLD POOL OF AIR WILL REMAIN ENTRENCHED OVER THE REGION
TONIGHT EVEN AS THE LOW PULLS AWAY (H925 TEMPS OF -1 TO -8C).
CONSIDERING UNDERACHIEVING HIGH TEMPERATURES THIS AFTERNOON...HEDGED
OVERNIGHT MINS BELOW GUIDANCE...WITH FORECAST MINS GENERALLY IN THE
20S. THIS FORECAST IS AT OR NEAR RECORDS FOR MOST LOCATIONS.

RECORD LOWS FOR APRIL 24TH:

FLINT...25 (1996) SAGINAW...25 (1918) DETROIT...27 (1892)

LONG TERM...

THE LATE APRIL INSOLATION TOMORROW WILL MAKE A BIG DIFFERENCE IN
TEMPERATURE RECOVERY TOMORROW (FROM RECORD/NEAR RECORD
COLD VALUES TO START THE DAY) AS 500 MB HEIGHTS RECOVER NICELY
TONIGHT INTO TOMORROW. FAVORABLE LOW LEVEL WESTERLY FLOW SHOULD
TRANSLATE TO HIGHS IN THE LOW TO MID 50S BASED ON 850 MB TEMPS
FORECASTED TO RISE BETWEEN -2 C TO ZERO BY DAY`S END...WITH NAM
SOUNDINGS INDICATING TOP OF THE MIXED LAYER REACHING RIGHT AT 850 MB.
NAM CU RULE VALUES ARE SOLIDLY POSITIVE TOMORROW...EXCEPT ACROSS
THE NORTHERN THUMB REGION...THUS NEAR FULL SUNSHINE EXPECTED WITH
JUST SOME WARM ADVECTION HIGH CLOUDS LATE IN THE DAY.

IT CONTINUES TO LOOK LIKE A CLOSE CALL ON POTENTIAL SHOWERS ARRIVING
DURING THE FIRST HALF OF THE WEEKEND...AS STRONG UPPER WAVE
CURRENTLY OVER BAJA CALIFORNIA LIFTS NORTHEAST...SENDING PACIFIC AND
GULF MOISTURE NORTHEAST...BUT EVENTUALLY REACHING THE BRICK WALL
OVER THE GREAT LAKES REGION IN THE FORM OF THE CONFLUENT FLOW AND
EXTREMELY DRY AIR (850 MB DEW PT DEPRESSIONS OF 20-40 C) IN
PLACE...SHUNTING THE UPPER WAVE THROUGH THE OHIO VALLEY.
JUST THE NORTHERN FRINGE OF THE VERY TIGHT 850 MB THETA-E RIDGE
FORECASTED TO CLIP SOUTHERN LOWER MICHIGAN SATURDAY AFTERNOON INTO
EARLY SATURDAY EVENING. BOTH THE 12Z CANADIAN AND GFS ARE AGRESSIVE
WITH THE RAIN OVERSPREADING SOUTHEAST MICHIGAN...WITH THE NAM BEING
ONE OF THE DRIER SOLUTIONS. PREFERENCE WILL BE WITH THE 12Z EURO
WHICH IS MORE OF MIDDLE GROUND. WILL BE FEATURING CHANCE POPS TO
THE I-69 CORRIDOR...WITH HIGH CHANCE/BORDERLINE LIKELY POPS AT THE
OHIO BORDER...AS THE SUBTROPICAL PACIFIC MOISTURE CONNECTION IS THE
OVER RIGHTING FACTOR IN SKEWING THE POPS HIGHER FROM MY PERSPECTIVE.
ALSO...THERE IS SUSTAINED LARGE SCALE ASCENT WITH THE UPPER LEVEL
PV ADVECTION THROUGH MUCH OF SATURDAY.

THIS UPCOMING WEEKEND INTO THE BEGINNING OF NEXT WEEK WILL REMAIN
RATHER QUIET AS FAR AS ANY PRECIPITATION IS CONCERNED.  UPPER LEVEL
TROUGHING WILL STILL BE OF INFLUENCE OVER THE AREA ON SUNDAY BEFORE
RIDGING STARTS BUILDING IN OVER THE REGION MONDAY INTO TUESDAY.  A
WARMING TREND WILL FINALLY COME BACK INTO THE PICTURE DURING THE
EXTENDED PERIOD.  THIS WILL BE A NICE WELCOME CONSIDERING THE COLD
TEMPS THAT THE AREA HAS BEEN DEALING WITH THIS WEEK.

MARINE...

THE NORTHWEST GRADIENT AND COLD ADVECTION IN PLACE OVER THE CENTRAL
GREAT LAKES TODAY IS WEAKENING...AS SURFACE HIGH/RIDGE AXIS SLIDES
EAST INTO THE REGION TONIGHT INTO TOMORROW...ALLOWING FOR DECREASING
WINDS AND SUBSIDING WAVES...AND WILL ALLOW SMALL CRAFT ADVISORIES TO
EXPIRE. HIGH PRESSURE BUILDING INTO ONTARIO OVER THE WEEKEND...WHILE
LOW PRESSURE TRACKS ALONG THE OHIO RIVER...LEADING TO LIGHT TO
MODERATE NORTHEAST WINDS DEVELOPING. WITH THE LONG FETCH AND
FUNNELING...STRONGEST WINDS LOOK TO BE WITHIN SAGINAW BAY...WHERE
WINDS COULD REACH OR SLIGHTLY EXCEED 20 KNOTS...POSSIBLY SUPPORTING
WAVES AROUND 4 FEET.

&&

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

$$

AVIATION.....DG
SHORT TERM...HLO
LONG TERM....SF/SS
MARINE.......SF


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



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