Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000
FXUS63 KDTX 151548
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1148 AM EDT WED APR 15 2015

.UPDATE...
15Z TEMPS IN THE MID-UPPER 50S AND WINDS GUSTING TO AROUND 20 KT
SIGNIFIES SLIGHTLY BETTER MIXING THAN ORIGINALLY FORECAST. QUICK
UPDATE WAS SENT TO BUMP MAX TEMPS UP A COUPLE DEGREES AND INCREASE
WINDS A COUPLE KNOTS.

&&

.AVIATION...ISSUED 608 AM EDT WED APR 15 2015

HIGH PRESSURE WILL MAINTAIN DRY/VFR CONDITIONS THROUGH TONIGHT.
POCKETS OF THICKER CIRRUS WILL SHIFT THROUGH AT TIMES...BUT SKIES
WILL REMAIN CLEAR BELOW 20K FT THROUGH THIS TIME.  MODEST EAST-
NORTHEAST WINDS WILL EMERGE WITH DAYTIME HEATING DURING THE LATE
MORNING AND EARLY AFTERNOON PERIOD.

//DTW THRESHOLD PROBABILITIES...

* NONE.

&&

.PREV DISCUSSION...ISSUED 355 AM EDT WED APR 15 2015

SHORT TERM... TODAY AND TONIGHT

SE MICHIGAN WILL REMAIN FULLY ENTRENCHED WITHIN DEEP LAYER
SUBSIDENCE AND DRY AIR TODAY...THE EXISTING LOW LEVEL ANTICYCLONIC
FLOW HOLDING BENEATH A GRADUALLY BUILDING UPPER HEIGHT FIELD.  THIS
WILL AGAIN YIELD PLENTY OF SUNSHINE...FILTERED AT TIMES AGAIN TODAY
AS POCKETS OF THICKER CIRRUS TRANSLATE ACROSS.  THE THERMAL
ADVECTIVE PROCESS AND OVERALL ADJUSTMENT WITHIN THE THICKNESS FIELD
APPEARS NEGLIGIBLE TODAY UNDER A LIGHT EASTERLY FLOW.  THIS POINTS
TO A SIMILAR TEMPERATURES DISTRIBUTION AS NOTED YESTERDAY /UPPER 50S-
LOWER 60S/...PERHAPS A TOUCH COOLER CLOSER TO THE LAKESHORE GIVEN
THE ONSHORE FLOW.

CLOSED UPPER LOW NOW CENTERED OVER EASTERN OKLAHOMA WILL SHEAR APART
AS IT EJECTS NORTHEAST OVER THE NEXT 36 HOURS.  THIS PROCESS WILL
TRANSLATE INTO A PERIOD OF MODEST NORTHWARD MOISTURE ADVECTION
THROUGH THIS TIME.  A MOSTLY CLEAR SKY WILL LARGELY HOLD THROUGH THE
EVENING...BEFORE HIGH CLOUDS STEADILY INCREASE FROM SOUTH TO NORTH
OVERNIGHT.  POTENTIAL FOR A FEW SHOWERS /MAINLY HIGHWAY 23 CORRIDOR/
AFTER ROUGHLY 09Z AS FRAGMENTS OF THE AFOREMENTIOND LOW ACCOMPANY
THE MAIN THETA-E GRADIENT INTO THE REGION.  LOWER END CHANCE POPS
REMAIN APPROPRIATE FOR THIS TIME WINDOW.  LOWS TONIGHT WITHIN THE
UPPER 30S AND LOWER 40S RANGE.

LONG TERM...

UPPER LEVEL TROUGH EXITING THE GREAT BASIN IN THE PROCESS OF CUTTING
OFF OVER THE FOUR CORNERS REGION TODAY. MEANWHILE...UPPER WAVE
COMING OUT OF TEXAS EARLY THIS MORNING IS FORECASTED TO TRACK
NORTHEAST AND REACH NORTHERN INDIANA THURSDAY MORNING. THIS
WAVE/BROAD UPPER LEVEL TROUGH WILL ALLOW FOR GOOD SURGE OF MOISTURE
INTO SOUTHERN LOWER MICHIGAN...AS 00Z GFS/CANADIAN/NAM INDICATING
850 MB DEW PTS OF 8+ C...LEADING TO MODEST INSTABILITY...AS
SHOWALTER INDEX FALLS TO AROUND ZERO WITH K INDICES INTO THE LOWER
30S. THE EXACT ORIENTATION OF THE 850 MB THETA-E RIDGE/INSTABILITY
AXIS/LOW LEVEL COVERGENCE REMAINS SOMEWHAT IN QUESTION...AS NAM/GFS
SUGGEST AXIS/FORCING WILL BE FARTHER WEST...OVER WESTERN LOWER
MICHIGAN. REGARDLESS...EVEN IF ACTIVITY INITIATES ON THE WESTERN
SIDE OF THE STATE...WOULD EXPECT VEERING OF THE LOW LEVEL WINDS TO
ALLOW FOR EASTWARD PROPAGATION INTO SOUTHEAST MICHIGAN...AND WILL
CARRY NUMEROUS POPS FOR THURSDAY AFTERNOON WITH SLIGHT CHANCE OF
THUNDERSTORMS. SHOWER ACTIVITY WILL LIKELY PERSIST INTO THURSDAY
EVENING AS 850 MB THETA-E RIDGE AXIS SLOWLY PUSHES EAST AND CLEARS
SOUTHEAST MICHIGAN AROUND/AFTER MIDNIGHT.

STRONG UPPER WAVE TO TRACK THROUGH ONTARIO ON FRIDAY AND CLIPPING
THE NORTHERN GREAT LAKES FRIDAY NIGHT...WITH COLD FRONT DROPPING
SOUTH THROUGH THE GREAT LAKES FRIDAY NIGHT-SATURDAY MORNING.
HOWEVER...MID APRIL INSOLATION AND FAVORABLE WESTERLY MIXING AHEAD
OF THE FRONT DURING FRIDAY WILL LIKELY ALLOW HIGH TEMPERATURES TO
PEAK AT OR SLIGHTLY ABOVE 70 DEGREES...PER LATEST MAV GUIDANCE AND
SUPPORTED BY 850 MB TEMPS OF 8.5 C. STRENGTHENING NORTHERLY FLOW OFF
LAKE HURON ON SATURDAY WILL LIKELY KEEP THE THUMB REGION IN THE
50S...OTHERWISE LOW TO MID 60S ARE EXPECTED UNDER MOSTLY SUNNY SKIES.

THE LATEST EUROPEAN MODEL RUN SUGGESTING MERGING OF THE FOUR
CORNERS 500 MB LOW WITH A DIGGING NORTHERN STREAM TROUGH COMING OUT
OF WESTERN CANADA ON SATURDAY...LEADING TO LONGWAVE TROUGH PUSHING
INTO THE CENTRAL CONUS ON SUNDAY. THIS WILL SEND ANOTHER GOOD STREAM
OF MOISTURE INTO THE GREAT LAKES REGION SUPPORTING INCREASING
POPS...AS CYCLOGENESIS TAKES PLACE OVER THE MIDWEST.

MARINE...

SURFACE HIGH PRESSURE WILL MAINTAIN DRY AND CALM CONDITIONS ACROSS
THE MARINE AREAS TODAY.  A WEAK DISTURBANCE WILL MOVE UP FROM THE
SOUTH DURING THURSDAY...PRODUCING SHOWERS. MILDER AIR COMING OVER
THE COLD LAKES WILL PROMOTE STABLE LOW LEVEL CONDITIONS...AND THUS
EXPECTING LIGHT WINDS ON FRIDAY. A COLD FRONT WILL SWEEP THROUGH
LAKE HURON FRIDAY NIGHT...BUT AMOUNT OF COLD AIR FOLLOWING IN THE
FRONTS WAKE IS IN QUESTION. AT THIS TIME...THE WIND FORECAST WILL
REMAIN CONSERVATIVE WITH THE NORTHWEST TO NORTH WINDS ON
SATURDAY...UNDER 20 KNOTS.

&&

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

$$

UPDATE.......DT
AVIATION.....MR
SHORT TERM...MR
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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