Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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000
FXUS63 KDTX 201723
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
123 PM EDT SUN JUL 20 2014


.AVIATION...

//DISCUSSION...

MOISTURE TRAPPED UNDER AN INVERSION WILL CONTINUE TO GENERATE A CU
FIELD AS DAYTIME HEATING PEAKS. THERE IS SOME UNCERTAINTY TO HOW
WIDESPREAD THIS CLOUD FIELD BETWEEN 4000-6000 FEET WILL BECOME
HOWEVER AS DRIER AIR TRIES TO MIX INTO THE LAYER OF MOISTURE SETTLED
UNDER THE INVERSION. BEST POTENTIAL FOR BKN CEILINGS WILL INITIALLY
BE OVER THE MOST INLAND PORTIONS OF THE LOWER PENINSULA EARLY THIS
AFTERNOON...WHERE SOME LOW-LEVEL WIND CONVERGENCE EXISTS. THIS AREA
OF CONVERGENCE WILL SHIFT SLOWLY EAST THROUGH THE LATE
AFTERNOON...INCREASING POTENTIAL FOR BKN CEILINGS AT MBS AND FNT. BY
THE TIME THIS CONVERGENCE AXIS SHIFTS TOWARDS THE DETROIT
AREA...DAYTIME HEATING WILL BE WANING AND THE CU FIELD WILL START TO
DISSIPATE. OTHERWISE...ONLY EXPECTING PATCHY CIRRUS AND A LITTLE BIT
OF SMOKE FROM THE WESTERN WILDFIRES...BOTH OF WHICH WILL LAST INTO
THE OVERNIGHT HORUS. SKIES SHOULD BECOME CLEAR ENOUGH HOWEVER FOR
FOG/BR TO FORM AGAIN AS WINDS GO LIGHT. FOG/BR LOOKS TO BE A LITTLE
LESS DENSE THAN LAST NIGHT HOWEVER AS LIGHT FLOW OVER THE GREAT
LAKES TURNS WEST AS OPPOSED TO EAST OFF THE NEARBY LAKES LIKE LAST
NIGHT.

FOR DTW...FOG/BR TRENDS WILL BE THE MAIN CONCERN FOR THE 18Z TAF
PERIOD. THE BEST POTENTIAL FOR MVFR BR IS BETWEEN 07Z AND 13Z...WITH
SOME IFR CONDITIONS POSSIBLY SETTLING IN AROUND 09Z.


//DTW THRESHOLD THREATS...

* LOW CONFIDENCE WITH CEILINGS BELOW 5000 FEET THROUGH 01Z TODAY.

* LOW CONFIDENCE IN FOG BELOW 1/2 MILE OR CEILINGS AT OR BELOW 200
FEET FROM 09-13Z MON.

&&

.PREV DISCUSSION...ISSUED 347 AM EDT SUN JUL 20 2014

SHORT TERM...TODAY AND TONIGHT

A PERSISTENT WEAK SURFACE TROUGH STRUCTURE IN PLACE OVERHEAD HAS LED
TO STAGNANT CONDITIONS AND THE DEVELOPMENT OF FOG THIS MORNING.
SURFACE OBSERVATIONS SUPPORTS THE THICKEST OF THE FOG IS OCCURRING
IN RURAL AREAS OUTSIDE OF URBAN HEAT ISLAND INFLUENCE. WITH NO
ADVECTIONS TO SPEAK OF...LOOK FOR THE REDUCED VISIBILITIES TO
PERSIST OVER THE NEXT FEW HOURS WITH SOME LOCALLY DENSE FOG
POSSIBLE. HIGH CLOUD ASSOCIATED WITH A MATURE CONVECTIVE VORTICITY
FEATURE IS SLIDING EASTWARD ACROSS SOUTHWESTERN LOWER MICHIGAN. THIS
HIGH CLOUD WILL TRACK OVER THE FORECAST AREA WITHIN THE NEXT COUPLE
OF HOURS AND LIMIT ANY ADDITIONAL COOLING. THE CLOUD WILL ALSO
PROVIDE A DOWNWARD RADIATIVE FLUX. THE ONE EXCEPTION MAY BE ACROSS
THE THUMB AS THE TRANSPARENCY OF THE HIGH CLOUD HAS BEEN INCREASING
ALONG THE NORTHERN EDGE OF THE CLOUD DECK. WILL BE MONITORING THIS
OVER THE NEXT COUPLE OF HOURS.

A CONTINUED WEAKNESS IN THE MSLP PATTERN IS EXPECTED TO PERSIST FROM
THE NORTHEASTERN UNITED STATES BACK SOUTHWESTWARD THROUGH THE
CENTRAL GREAT LAKES TODAY. THIS WILL ESSENTIALLY KEEP THE
SOUTHWESTERLIES AND WARM AIR ADVECTION AT BAY. WITH HEIGHT RISES
ONLY BEGINNING IN EARNEST LATE THIS AFTERNOON AND TONIGHT...THE
SUGGESTION IS TO REMAIN RELATIVELY TEMPERED ON MAX TEMPS TODAY.
EXPECTED READINGS SHOULD PUSH UP AGAINST 80 DEGREES. THE COMBINATION
OF PERSISTENCE WITH THE FORECASTED LAPSE RATES BETWEEN 4700 AND 6700
AS LED TO A MORE PESSIMISTIC CLOUD FORECAST CARRYING OFF OF THE HIGH
CLOUD THIS MORNING INTO THE LATE MORNING/EARLY AFTERNOON.

LONG TERM... MONDAY THROUGH SATURDAY

THERE REMAINS SOLID AGREEMENT AMONG THE 00Z MODEL SUITE THAT A
BUILDING MID LEVEL RIDGE AXIS /AN EXTENSION OF THE SUBTROPICAL RIDGE
OVER THE SRN PLAINS/ WILL EXPAND ACROSS THE OHIO VALLEY AND SRN
GREAT LAKES MONDAY INTO TUESDAY. THE INCREASING MID LEVEL HEIGHTS
AND LOW LEVEL WARM AIR ADVECTION UNDER S-SW FLOW WILL LEAD TO RISING
TEMPS MON INTO TUES. MODEL SOUNDINGS ALSO CONTINUE TO SHOW A STOUT
MID LEVEL CAP OVER SE MI AS A RESULT OF THE WARMING MID LEVELS...
WHICH SUPPORTS THE CURRENT DRY FORECAST BOTH MON AND TUES. MOS
GUIDANCE ALONG WITH RECENT MODEL SOUNDINGS SUGGEST DAYTIME HIGHS MON
WILL EASILY RISE INTO THE MID/UPPER 80S. DESPITE SOME POTENTIAL
CIRRUS DEBRIS FROM UPSTREAM CONVECTION TUES...THE S-SW FLOW WILL
STRENGTHEN AND THEREFORE LEAD TO BETTER LOW LEVEL WARM AIR ADVECTION
/850MB TEMPS RISING TO +19 TO +20C/. THIS WILL BOOST TUES HIGHS TO
THE 90 DEGREE MARK. THE SOUTHERLY GRADIENT AND RISING SFC DEWPOINTS
WILL ALSO KEEP NIGHTTIME MINS ON THE MILD SIDE DURING THE FIRST HALF
OF THE WORK WEEK.

AMPLIFICATION OF THE LONG WAVE PATTERN OVER CANADA CONTINUES TO BE
SHOWN BY THE 00Z MEDIUM RANGE MODEL SUITE. THIS WILL FEATURE
DEEPENING OF A TROUGH OVER ERN CANADIAN AND THE ERN US WED INTO
THURS...DRIVING A COLD FRONT ACROSS LOWER MI IN THE TUES NIGHT/EARLY
WED TIME FRAME. THE FORECAST FOR CONVECTION ACROSS SE MI MAY HOWEVER
RELY MORE ON THE POTENTIAL DEVELOPMENT OF AN UPSTREAM MCS TUES OR
TUES EVENING. INSTABILITY ACROSS MN/WI IS FORECAST TO BE QUITE HIGH
ON TUESDAY...WHERE UPSCALE CONVECTIVE GROWTH IS EXPECTED. THE
CHANCES FOR SHOWERS/THUNDERSTORMS OVER SE MI WILL BE HEAVILY
DEPENDENT UPON THE DEGREE OF FORWARD PROPAGATION OF THESE
THUNDERSTORM COMPLEXES...WHICH IN TURN WILL BE INFLUENCED BY THE
DEGREE OF INSTABILITY OVER SE MI. GIVEN THE UNCERTAINTY THIS FAR OUT
INTO THE FORECAST PERIOD...GENERAL CHANCE TYPE POPS TUES NIGHT INTO
WED WILL REMAIN SUFFICIENT. COOLER AND MUCH DRIER AIR WILL FUNNEL
INTO SE MI IN THE WAKE OF THE COLD FRONT. THE LATEST GFS AND ECMWF
SUGGEST THE RIDGE OVER CENTRAL CANADA QUICKLY BREAKING DOWN BY THE
END OF THE WORK WEEK. THIS WILL SUPPORT MODEST MID LEVEL HEIGHT
RISES OVER MICHIGAN AND THUS A SLIGHT WARMING TREND HEADING INTO
NEXT WEEKEND.

MARINE...

A BROAD REGION OF HIGH PRESSURE EXTENDING ACROSS LOWER MI AND LAKE
HURON WILL MAINTAIN LIGHT WINDS AND FAVORABLE WAVE CONDITIONS ON THE
GREAT LAKES TODAY. LIGHT S-SW WINDS WILL DEVELOP ON MONDAY AND
STRENGTHEN A LITTLE ON TUESDAY IN ADVANCE OF A SLOW MOVING FRONTAL
BOUNDARY OVER THE NORTHERN PLAINS. WARM AIR ADVECTION WILL LEAD TO
STRONG STABILITY OVER THE LAKES DURING THIS TIME FRAME. THIS WILL
KEEP WINDS GENERALLY AT OR BELOW 15 KNOTS. A COLD FRONT WILL PASS
THROUGH THE REGION TUESDAY NIGHT OR EARLY WEDNESDAY...PROVIDING A
CHANCE FOR THUNDERSTORMS. THERE IS LIKELY TO BE A NOTABLE WIND SHIFT
TO THE N-NW WITH THE PASSAGE OF THE FRONT.

&&

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

&&

$$

AVIATION.....HLO
SHORT TERM...CB
LONG TERM....SC
MARINE.......SC


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



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