Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 122300
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
700 PM EDT FRI SEP 12 2014


.AVIATION...

//DISCUSSION...

MVFR/LOW VFR CEILINGS WILL PERSIST THROUGH THE TAF PERIOD. HEAVIER
AND WIDESPREAD RAIN SHOWERS WILL BE OVERSPREADING SOUTHEAST MICHIGAN
TONIGHT FROM WEST TO EAST. FURTHER REDUCTION IN CEILINGS IS LIKELY
OVERNIGHT WITH MODERATE RAIN SHOWERS...INTO IFR
CATEGORY...ESPECIALLY ACROSS THE NORTHERN TAF
SITES...MBS/FNT/PTK. LOW LEVEL WINDS WILL FLIP AROUND TO THE
NORTHWEST SATURDAY MORNING...BUT DRYING WILL PROBABLY BE
SLOW WITH CEILINGS JUST GRADUALLY IMPROVING...ALONG WITH FEW
LINGERING POSSIBLE.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CEILINGS BELOW 5000 FEET THROUGH SATURDAY AFTERNOON.

&&

.PREV DISCUSSION...ISSUED 303 PM EDT FRI SEP 12 2014

SHORT TERM...TONIGHT

IMPRESSIVE UPPER WAVE/COLD POOL FOR EARLY SEPTEMBER STANDARDS...AS
500 MB COLD CORE WAS AT LEAST -27 C COMING OUT OF EASTERN SOUTH
DAKOTA. 12Z NAM/REGIONAL GEM IN PRETTY GOOD AGREEMENT WITH THE
POSITION/TRACK OF THE 500 MB MAX 6 HR HEIGHT FALL CENTER TRACKING
THROUGH THE NORTHERN HALF OF THE CWA LATE TONIGHT. RAIN IS ALL BUT
CERTAIN TONIGHT...WITH THE EXCELLENT HEIGHT FALLS/700 MB FGEN AND
SUFFICIENT MOISTURE (PW VALUES AROUND 1 INCH) AS THE SYSTEM/TROUGH
AXIS QUICKLY BECOMES NEUTRAL TILTED IF NOT SLIGHTLY NEGATIVELY
TILTED BY 12Z SATURDAY (SEE 12Z UKMET). THE RELATIVELY WARM
WATERS/MOISTURE FLUX OFF LAKE MICHIGAN/SAGINAW BAY WILL ALSO
CONTRIBUTE...AND THERE APPEARS THERE IS A CHANCE OF
THUNDERSTORMS/RUMBLE OF THUNDER VERY LATE TONIGHT NORTH OF I-69 WITH
THE INTENSE LIFT AND STEEP MID LEVEL LAPSE (700-500 MB) SLIGHTLY
EXCEEDING 7 C/KM...PER 12Z REGIONAL GEM AND NAM. OUTSIDE OF
SCATTERED RAIN SHOWERS THIS AFTERNOON/EVENING...BULK OF MODERATE
RAINFALL SHOULD HOLD OFF UNTIL AFTER MIDNIGHT. WITH SOLID HALF
INCH + TOTALS EXPECTED FOR MUCH OF THE AREA. WITH SATURATED 850 MB
TEMPS AROUND 3 C BY 12Z SATURDAY...FOLLOWING MOIST ADIABATIC
TOWARD THE SURFACE SHOULD YIELD MINS IN THE 45 TO 50 DEGREE RANGE.

LONG TERM...SATURDAY THROUGH NEXT FRIDAY

A PUSH OF STRONG MID LEVEL SUBSIDENCE /ESPECIALLY WHEN VIEWED ALONG
A SYSTEM RELATIVE FRAMEWORK/ WILL OVERSPREAD SE MI IN THE 12-15Z
TIME FRAME SAT IN THE WAKE OF TONIGHTS POTENT MID LEVEL WAVE. THIS
WILL BRING AN ABRUBT END TO THE RAIN FROM SW TO NE DURING THE MID TO
LATE MORNING. THE SLIGHTLY STRONGER SURFACE REFLECTION SHOWN ON THE
NAM AND GEM OVER LAKE ERIE APPEARS REASONABLE CONSIDERING THE
INFLUENCE OF THE WARM WATERS. THIS WILL RESULT IN A GOOD ISSALOBARIC
COUPLET TRAVERSING SE MI SHORTLY AFTER 12Z. THIS ALONG WITH A BRIEF
INTERVAL OF LOW LEVEL COLD AIR ADVECTION AND GOOD LARGE SCALE
SUBSIDENCE SUGGESTS A SHORT PERIOD OF GUSTY WINDS BY LATE SAT
MORNING /POSSIBLY PUSHING 30 MPH/.

WHILE THE MORNING SUBSIDENCE MAY LEAD TO SOME BREAKS IN THE
CLOUDS...DIURNAL INFLUENCES SHOULD CAUSE SKIES TO CLOUD OVER BY
EARLY SAT AFTERNOON. THE LOW LEVEL FLOW WILL THEN BECOME STRONGLY
ANTICYCLONIC BY LATE SAT AFTERNOON/EVENING. THERE IS INDICATION IN
MODEL SOUNDINGS AND RH PLAN VIEWS THAT THIS WILL LEAD TO A CLEARING
TREND AND REMAINS SUPPORTIVE OF THE CURRENT CLEAR FORECAST SAT
NIGHT. EVEN WITH THE PROSPECTS FOR SOME INTERVALS OF SUN ON
SATURDAY...THE COOL AIRMASS ACROSS THE REGION WILL ONLY SUPPORT
HIGHS IN THE UPPER 50S/LOW 60S. THE SFC HIGH OVERHEAD SAT NIGHT WILL
SUPPORT OPTIMAL RADIATION COOLING /ASSUMING SKIES FULLY CLEAR/...
SUGGESTING LOCALS OUTSIDE OF THE DETROIT URBAN AREA COULD SEE MIN
TEMPS DIP DOWN INTO THE 30S.

THE MEAN FLOW WILL REMAIN PROGRESSIVE DURING THE LATER HALF OF THE
WEEKEND INTO EARLY NEXT WEEK. RETURN FLOW WITHIN THE DEPARTING SFC
HIGH WILL SUPPORT A SLIGHT UPTICK IN TEMPS SUNDAY INTO MONDAY.
INCREASING UPPER JET DYNAMICS WILL OCCUR IN ADVANCE OF A SHORT WAVE
IMPULSE FORECAST TO DEEPEN AS IT TRACKS FROM THE UPPER MIDWEST
ACROSS THE GREAT LAKES MON/MON NIGHT. THIS UPPER JET SUPPORT WILL
INCREASE THE FORCING ALONG THE MID TROPOSPHERIC FRONT AND WARRANT A
CHANCE OF SHOWERS MON AND MON NIGHT. THE REMAINDER OF THE WORKWEEK
SHOWS HIGH PRESSURE TO BE THE DOMINANT WEATHER FEATURE. TEMPERATURES
ARE EXPECTED TO STAY BELOW AVERAGE THROUGH THE PERIOD.

MARINE...

A STRONG UPPER LEVEL LOW WILL TRAVERSE LAKE HURON EARLY SAT MORNING.
ALONG WITH WIDESPREAD RAIN...SOME EMBEDDED THUNDER AND A CHANCE OF
WATER SPOUTS WILL BE TRIGGERED BY THIS SYSTEM. THE ASSOCIATED
SURFACE LOW WILL TRACK ACROSS LAKE ERIE SAT MORNING AND WILL CAUSE
GUSTY N-NE WINDS IN ITS WAKE. THIS WILL LEAD TO ROUGH BOATING
CONDITIONS SUPPORTIVE OF SMALL CRAFT ADVISORIES TONIGHT INTO SAT
AFTERNOON. STRONG HIGH PRESSURE WILL THEN BUILD IN FROM THE WEST AND
WILL RAPIDLY REDUCE WINDS AND WAVES ON THE LAKES LATE SATURDAY. THE
HIGH WILL MAINTAIN LIGHT WINDS THROUGH SUNDAY. A WEAK COLD FRONT
WILL TRACK ACROSS THE REGION ON MONDAY...WITH HIGH PRESSURE BUILDING
BACK IN ITS WAKE.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.

LAKE HURON...
     SMALL CRAFT ADVISORY...INNER SAGINAW BAY...UNTIL NOON SATURDAY.

     SMALL CRAFT ADVISORY...OUTER SAGINAW BAY...UNTIL 4 PM SATURDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT
     HURON...FROM 6 AM SATURDAY TO 4 PM SATURDAY.

LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...
     SMALL CRAFT ADVISORY...FROM 8 AM SATURDAY TO 4 PM SATURDAY.

&&

$$

AVIATION.....KURIMSKI
SHORT TERM...SF
LONG TERM....SC/DE
MARINE.......SC


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






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