Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 161940
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
340 PM EDT THU APR 16 2015

.SHORT TERM...THIS AFTERNOON AND TONIGHT

WEAK VORTICITY CENTER WILL CROSS THE AREA LATE TODAY AND PROVIDE
GENERALLY CLOUDY SKIES WITH SCATTERED LIGHT SHOWERS OR SPRINKLES.
ACTIVITY WILL REMAIN RATHER LIMITED AS LITTLE TO NO INSTABILITY WILL
BE AVAILABLE TO ENHANCE THE SHOWER ACTIVITY ASSOCIATED WITH THE
CONVERGENCE/LIFT FROM THE SHORTWAVE ITSELF. SLIGHTLY MORE ORGANIZED
CONVECTION WILL SHIFT NORTHEAST THROUGH PARTS OF THE EASTERN OHIO
VALLEY AS THE TRAILING TROUGH AXIS SHIFTS THROUGH THE AREA AS THE
MAIN CENTER EXITS INTO ONTARIO THIS EVENING. THIS WILL FOCUS ANY
MARGINAL INSTABILITY WELL EAST AND SOUTHEAST OF THE AREA.

WITH PLENTY OF CLOUD COVER ALREADY EARLY THIS AFTERNOON...EXPECTED
TEMPERATURES TO ONLY EDGE UP ANOTHER COUPLE OF DEGREES...RANGING IN
THE UPPER 50S TO MID 60S FOR MOST LOCATIONS.

SKIES WILL CLEAR OVERNIGHT AS THIS SYSTEM PROGRESSES NORTHEAST AND
TROUGH AXIS CLEARS LOWER MICHIGAN AROUND MIDNIGHT. A WEAK RIDGE OF
SURFACE HIGH PRESSURE WILL BUILD INTO THE AREA IN ITS WAKE OF ALLOW
TEMPERATURES TO FALL OFF INTO THE 40S...SOME 5+ DEGREES ABOVE
AVERAGE FOR THE MIDDLE OF APRIL.

&&

.LONG TERM...

MUTED RIDGING WITH DRY NORTHWESTERLY FLOW OVER NORTH AMERICA WILL
ADVECT A DRY COLUMN INTO THE GREAT LAKES REGION ON FRIDAY. REMAINING
LOWER TROPOSPHERIC MOISTURE IS EXPECTED TO PUSH OUT OF FAR
SOUTHEASTERN MICHIGAN LEADING INTO/SHORTLY AFTER 12Z. UNCERTAINTY
REMAINS WITH EXTENT/AMOUNT OF MIDLEVEL CLOUDS IN/AROUND SOUTHERN
LAKE HURON AND SAGINAW BAY...AS MOISTURE IS FORECASTED TO ADVECT OUT
OF THE ARROWHEAD OF MINNESOTA AND THROUGH THE STATE. CONFIDENCE IS
MEDIUM TO LOW...WITH MODEL SOUNDINGS SHOWING BOTH A LACK OF
SATURATION DEPTH AND A LACK OF AN INVERSION STRUCTURE. KEPT WITH THE
INHERTIED GRIDS WHICH IS COLLABORATED WELL WITH NEIGHBOR OFFICES OF
LOW SKY FRACTION FRIDAY. INSOLATION SHOULD ALLOW FOR ABOVE AVERAGE
TEMPERATURES WITH HIGHS IN MANY AREAS PUSHING INTO THE LOWER 70S. A
COMPOSITE LAKE BOUNDARY WILL LIKELY FORM OVER THE THUMB...KEEPING
THE THUMB COUNTIES IN THE UPPER 60S.

FAIRLY STOUT SHORTWAVE FEATURE IS EXPECTED TO PUSH RAPIDLY ACROSS
ONTARIO FRIDAY NIGHT. SUBSIDENCE AND NORTHTERLY MEAN FLOW IN THE
WAKE OF THE SHORTWAVE PASSAGE WILL PUSH A DRY COLD FRONT FEATURE
SOUTHWARD THROUGH LOWER MICHIGAN. TIMING OF THIS COLD FRONT THROUGH
THE CWA WILL LIKELY COINCIDE WITH A LATE AFTERNOON/EARLY EVENING
RELEASE OF THE MARINE LAYER/LAKE BREEZE. THUS...FEELING THERE IS A
GOOD POTENTIAL FOR OVERACHIEVING TEMPERATURES SOUTH OF INTERSTATE
69. CURRENT FORECAST HAS HIGHS IN THE 70S. IT WILL AGAIN BE COOLER
NEAR THE LAKES.

SOUTHERN STREAM WAVE WILL CONTINUE ITS EASTWARD PROGRESS
SUNDAY AS A HEALTHY LOW LEVEL JET IS PROGGED TO STRENGTHEN OVER THE
OHIO VALLEY AND LOWER GREAT LAKES. MOISTURE ADVECTION WITH THIS
FEATURE NECESSITATES CONTINUING LIKELY POPS FOR SUN/SUN NIGHT WITH A
CHANCE OF THUNDER ACROSS THE SOUTH AS SHOWALTER INDICES GO NEGATIVE.
THE SOUTHERN STREAM WAVE IS FORECAST TO PHASE WITH A NORTHERN STREAM
WAVE AS A STRONG SURFACE LOW DEVELOPS NORTH OF LAKE SUPERIOR MONDAY.
12Z GUIDANCE SHOWING THIS PROCESS RESULTING IN A STRONG COLD FRONT
BEING DRIVEN THROUGH THE AREA MONDAY. RESULTING UPPER LEVEL FLOW
PATTERN BECOMES CUT OFF IN THE VICINITY OF THE GREAT LAKES OR
SOUTHERN CANADA...LEADING TO A COOLING TREND NEXT WEEK.

&&

.MARINE...

A MODEST WIND FIELD OF LESS THAN 20 KNOTS WILL PERSIST ON
FRIDAY...AHEAD OF A COLD FRONT WHICH WILL SWING THROUGH THE CENTRAL
GREAT LAKES FRIDAY NIGHT. THE COLD PUSH BEHIND THE FRONT LOOKS VERY
WEAK...AND THUS WINDS ARE EXPECTED TO REMAIN GENERALLY UNDER 20
KNOTS. THE STRONGEST WINDS MAY ACTUALLY OCCURS SATURDAY AFTERNOON
OVER SAGINAW BAY AS THE LAND/LAKE DIFFERENTIAL HEATING/TEMPERATURE
GRADIENT RAMPS UP...AND MARINE LAYER LIKELY SURGES INLAND LATE IN
THE DAY. LOSS OF DAYTIME HEATING AND SURFACE RIDGE IN PLACE WILL
QUICKLY ALLOW FOR RETURN TO THE LIGHT WINDS SATURDAY EVENING/NIGHT.

&&

.AVIATION...ISSUED 159 PM EDT THU APR 16 2015

LIGHT SHOWERS OR SPRINKLES WILL DOT THE AREA INTO EARLY THIS EVENING
AS A SHORTWAVE CROSSES THE AREA. WITH THIS ACTIVITY...CIGS WILL
RANGE FROM MVFR TO LOWER VFR. LOWER CIGS...IFR TO MVFR...WILL FUNNEL
INTO AREA...PARTICULARLY PTK SOUTH ONCE THIS SYSTEM PASSES AND A
TRAILING SURFACE TROUGH SLOWLY DRAGS ACROSS THE AREA AND FOCUSES LOW
LEVEL MOISTURE. VFR CONDITIONS WILL THEN SET UP LATER TONIGHT INTO
FRIDAY AS A RIDGE OF HIGH PRESSURE BUILDS INTO THE AREA IN THE WAKE
OF THIS TROUGH.

FOR DTW...STILL EXPECT CIGS TO LOWER GRADUALLY INTO THIS EVENING
WITH VSBYS. SCATTERED LIGHT SHOWERS WILL BE POSSIBLE INTO EARLY
EVENING WITH SOME VSBY RESTRICTIONS DEVELOPING THIS EVENING INTO
PART OF THE OVERNIGHT.

//DTW THRESHOLD PROBABILITIES...

* HIGH IN CEILINGS AT OR BELOW 5000 FT THROUGH TONIGHT.

&&

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

$$

SHORT TERM...DG
LONG TERM....CB/DT
MARINE.......CB
AVIATION.....DG


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


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