Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 211655
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1255 PM EDT THU MAY 21 2015

.AVIATION...

AN UPPER LEVEL WAVE SLIDING THROUGH OHIO WILL SUSTAIN MID AND HIGH
CLOUDS OVER THE TERMINAL CORRIDOR THROUGH THE AFTERNOON. VFR CEILING
WILL BE WELL ABOVE 5000 FT UNTIL THE NEXT COLD FRONT APPROACHES
TONIGHT. THE FRONT WILL SLIDE THROUGH NORTHERN LOWER MICHIGAN TODAY
AND REACH MBS EARLY IN THE EVENING. THERE IS INCREASING EVIDENCE
THAT SOME LIGHT VFR RAIN SHOWERS WILL ACCOMPANY THE WIND SHIFT
ACROSS SE MICHIGAN...PASSING THROUGH DTW SHORTLY AFTER MIDNIGHT. A
CLEARING TREND IS THEN EXPECTED POST FRONT BUT LOW END VFR CEILING
WILL BE LIKELY AGAIN BY LATE FRIDAY MORNING INTO THE AFTERNOON.

//DTW THRESHOLD PROBABILITIES...

* MODERATE FOR CEILING BELOW 5000 FT TONIGHT AND FRIDAY MORNING.

&&

.PREV DISCUSSION...ISSUED 348 AM EDT THU MAY 21 2015

SHORT TERM...TODAY AND TONIGHT

DEEP CLOSED LOW CURRENTLY DIGGING SOUTHEAST ACROSS HUDSON BAY WILL
STEADILY LIFT INTO WESTERN QUEBEC OVER THE NEXT 24 HOURS.  A
BROADENING LOWER HEIGHT FIELD TIED TO THIS SYSTEM WILL BUILD INTO
LOWER MICHIGAN THROUGH THIS TIME...SENDING A COLD FRONT ACROSS
SOUTHEAST MICHIGAN BY TONIGHT.  RELATIVELY BENIGN PRE-FRONTAL
CONDITIONS FOR TODAY...A LEAD WAVE EJECTING THROUGH RESULTING IN
LITTLE MORE THAN SOME INCREASE IN MID CLOUD FOR THE DAYLIGHT PERIOD.
LOW LEVEL GRADIENT WILL BACK TO WESTERLY...PROVIDING A BRIEF WINDOW
FOR WARM AIR ADVECTION TO TAKE HOLD DURING THE AFTERNOON. THIS WILL
RESULT IN A NOTEWORTHY INCREASE IN TEMPERATURES THROUGH THE 850 MB
LAYER.  THIS UPWARD TREND WILL LEAD TO HIGHS LARGELY WITHIN THE
MIDDLE AND UPPER 60S RANGE.

FIRM COLD FRONTAL BOUNDARY SET TO DROP SOUTHEAST ACROSS THE REGION
THROUGH THE OVERNIGHT HOURS.  A SOLID BUT BRIEF PERIOD OF FRONTAL
CONVERGENCE WITH PROVIDE THE MAIN SUPPORT FOR AT LEAST A LOW CHANCE
FOR SHOWER DEVELOPMENT.  THE OVERALL MOISTURE QUALITY REMAINS A
CONCERN...BUT A NARROW SLIVER OF THETA-E ADVECTION WILL ARRIVE
COINCIDENT WITH THE FRONTAL PASSAGE.  THIS WILL HELP REDUCE
STABILITY ABOVE THE FRONTAL SLOPE...PROVIDING SOME INCREASING IN MID
LEVEL LAPSE RATES.  THIS CONTINUES TO WARRANT A LOWER END POP
MENTION.  A PERIOD OF POST-FRONTAL COLD AIR ADVECTION LATE TONIGHT
WILL HELP BRING LOWS INTO THE LOWER AND MIDDLE 40S FOR MOST
LOCATIONS...THE COLDEST LOCALES ACROSS THE TRI-CITIES/THUMB
POTENTIALLY DIPPING INTO THE UPPER 30S.

LONG TERM...FRIDAY THROUGH WEDNESDAY

SURFACE HIGH PRESSURE WILL BECOME CENTERED OVER MICHIGAN BY FRIDAY
EVENING BEFORE MIGRATING TO THE MID-ATLANTIC COAST SATURDAY. THIS
WILL PROVIDE DRY AND QUIET WEATHER FOR THE END OF THE WEEK. FORECAST
MODEL SOUNDINGS SHOW ONLY A THIN LAYER OF MOISTURE TRAPPED UNDER THE
SUBSIDENCE INVERSION BOTH DAYS...AND WILL MAINTAIN A MOSTLY SUNNY
FORECAST AS HIGH CLOUDS AHEAD OF AN APPROACHING LOW PRESSURE SYSTEM
LOOK TO REMAIN TO OUR WEST UNTIL AT LEAST SATURDAY NIGHT.
TEMPERATURES WILL REMAIN BELOW NORMAL FRIDAY BEHIND A COLD
FRONT...ESPECIALLY OVER THE THUMB WITH NORTHERLY FLOW OFF LAKE
HURON. THIS SHOULD LIMIT HIGHS TO THE 50S IN THE THUMB AND LOW/MID
60S FURTHER INLAND. EXCELLENT RADIATIONAL COOLING CONDITIONS LOOK TO
SET UP FRIDAY NIGHT AS THE HIGH BECOMES CENTERED OVERHEAD...SKIES
CLEAR...AND WINDS GO LIGHT. LOWERED FORECAST MINS TO THE 30S FOR
MOST LOCATIONS...WITH WARMER TEMPS NEAR 40 IN THE DETROIT HEAT
ISLAND. GIVEN THESE VALUES AND CONDITIONS...THERE IS POTENTIAL FOR
FROST DEVELOPMENT ACROSS SOUTHEAST MICHIGAN...PARTICULARLY FROM THE I-
69 CORRIDOR NORTHWARD. HEADLINES MAY BE NEEDED. SOME MODERATION IN
TEMPERATURE IS EXPECTED SATURDAY AS WINDS TURN SOUTHWESTERLY. THIS
SHOULD BUMP TEMPS UP CLOSER TO NORMAL IN THE UPPER 60S TO NEAR 70
DURING THE AFTERNOON.

A WARMER AND MORE ACTIVE PATTERN THEN LOOKS TO SET UP LATE SUNDAY
THROUGH THE MIDDLE OF NEXT WEEK AS SEVERAL SHORTWAVES EJECT OUT OF
THE LONGWAVE TROUGH OVER THE WESTERN U.S. AND LIFT NORTHEAST. MAIN
AREA OF SURFACE LOW PRESSURE SHOULD ALSO LIFT THROUGH THE UPPER
MIDWEST OR WESTERN GREAT LAKES EARLY NEXT WEEK AS WHAT REMAINS OF
THE MAIN UPPER TROUGH MOVES EAST. TRACK AND TIMING OF THE SMALLER
FEATURES STILL VARY WITHIN MEDIUM RANGE MODELS...LEADING TO SOME
UNCERTAINTY WITH TIMING FRONTAL FEATURES AND ESPECIALLY ROUNDS OF
CONVECTION THAT WILL DEVELOP ALONG THEM. SUNDAY LOOKS FAIRLY QUIET
NOW WITH JUST INCREASING SOUTHWEST WINDS AND CLOUDS AHEAD OF THE
FIRST SHORTWAVE/LOW PRESSURE SYSTEM. UPPER RIDGING SHOULD HELP
PROVIDE STABILITY...AND FEEL GOOD WITH DRY CONDITIONS THROUGH
AFTERNOON AND EVEN INTO THE EARLY EVENING. EURO/GEM STILL IN GOOD
CONSENSUS WITH LIFTING THE WARM FRONT UP THROUGH LOWER MICHIGAN
SUNDAY NIGHT INTO MONDAY...AND THIS IS WHERE HIGHEST CONFIDENCE IN
CONVECTION (AND POPS) REMAINS DURING THE FORECAST PERIOD. CONFIDENCE
WITH ADDITIONAL ROUNDS SHOWERS/STORMS BEYOND THAT IS VERY LOW WITH
MODELS DIFFERING GREATLY WITH ANY SHORTWAVES...THE LOW TRACK...AND
WITH THE PASSAGE OF A COLD FRONT.

MARINE...

QUIET CONDITIONS WILL START THE DAY BEFORE HIGH PRESSURE GETS PUSHED
SOUTH OF THE AREA. A SURFACE TROUGH AND COLD FRONT WILL THEN DROP
THROUGH LAKE HURON STARTING LATE THIS AFTERNOON...AND CONTINUE
SOUTHWARD THROUGH THE REMAINDER OF THE CENTRAL GREAT LAKES TONIGHT.
THIS WILL BRING AN INCREASE IN NORTHWEST WINDS. THE STRONGEST GUSTS
ARE EXPECTED OVER THE OPEN WATERS OF NORTHERN AND CENTRAL LAKE
HURON...WHERE SPEEDS WILL REACH AROUND 25 KNOTS. WINDS WILL DIMINISH
QUICKLY ON FRIDAY AS HIGH PRESSURE AGGRESSIVELY BUILDS BACK INTO
MICHIGAN BY EVENING. WINDS WILL THEN REMAIN LIGHT INTO SATURDAY AS
HIGH PRESSURE REMAINS IN CONTROL.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.

&&

$$

AVIATION.....BT
SHORT TERM...MR
LONG TERM....HLO
MARINE.......HLO


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