Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 142247
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
647 PM EDT SUN SEP 14 2014


.AVIATION...

//DISCUSSION...

VFR CONDITIONS WILL PERSIST INTO MONDAY MORNING WITH NOTHING MORE
THAN LIGHT SOUTH-SOUTHWEST WIND AND MID/HIGH CLOUDS TO CONTEND WITH.
LIGHT SHOWERS WILL APPROACH KMBS DURING MID-MORNING AND SPREAD
ACROSS THE REMAINDER OF THE AREA DURING THE AFTERNOON. VFR
CONDITIONS WILL PREVAIL DURING THE EARLY STAGES OF PRECIPITATION DUE
TO DRY AIR IN THE LOWER LEVELS, BUT INCREASING RAINFALL INTENSITY
WITH THE PASSAGE OF THE PRIMARY UPPER WAVE WILL BRING A RISK OF MVFR
CEILING BY 21Z OR SO. LIGHT COLD ADVECTION IN THE WAKE OF THE
PASSING SYSTEM WILL RESULT IN STEEPER LOW-LEVEL LAPSE RATES CAPABLE
OF SUPPORTING A LOW MVFR OR PERHAPS EVEN HIGH IFR CEILING FOR A FEW
HOURS MONDAY NIGHT.

//DTW THRESHOLD THREATS...

* MEDIUM CONFIDENCE IN CEILING BELOW 5KFT MONDAY AFTERNOON

&&

.PREV DISCUSSION...ISSUED 353 PM EDT SUN SEP 14 2014

SHORT TERM... AFTERNOON THROUGH TONIGHT

SE MICHIGAN WILL BE IN A BENIGN PATTERN BETWEEN SYSTEMS FOR THE
REMAINING PART OF TODAY AND MOST OF TONIGHT. WEAKENING LOW PRESSURE
AND A TRAILING COLD FRONT OVER NORTHWEST ONTARIO AND THE MIDWEST
WILL MAKE JUST SLOW EASTWARD PROGRESS AGAINST A BROAD AND STURDY
AREA OF HIGH PRESSURE CENTERED OVER THE NEW ENGLAND STATES.
SOUTHWEST GRADIENT FLOW WILL INCREASE JUST ENOUGH OVER LOWER
MICHIGAN TO DISPLACE THE COOL AND MOIST LOW LEVEL AIR MASS THAT HAS
BEEN PRONE TO SUPPORTING CLOUD COVER DURING THE DAY. THE RESULTING
CLEARING TREND DURING THE EVENING WILL SET UP ANOTHER ROUND OF COOL
TEMPERATURES BUT NOT AS COOL AS LAST NIGHT. A LIGHT SOUTHWEST
SURFACE WIND AND INCREASING CLOUDS AHEAD OF THE CENTRAL PLAINS WAVE
WILL LIMIT FULL RADIATIONAL COOLING DURING THE OVERNIGHT PERIOD. THE
FIRST SIGN OF THE PLAINS SYSTEM IS INDICATED IN THE UPPER LEVELS ON
AFTERNOON WV SATELLITE IMAGERY MOVING OUT OF THE CANADIAN ROCKIES.
THIS WAVE WILL FEED OFF THE ENTRANCE REGION AND SOUTH FLANK OF THE
UPPER JET AXIS AVERAGING 100 KTS OVER THE MIDWEST. LEE SIDE SURFACE
PRESSURE FALLS OVER THE CENTRAL PLAINS WILL CONTRIBUTE TO
MAINTENANCE OF SOUTHWEST LOW LEVEL GRADIENT FLOW OVER THE GREAT
LAKES...AND MID LEVEL FRONTOGENESIS WILL GENERATE THE MID AND HIGH
CLOUDS THAT WILL DRIFT OVER LOWER MICHIGAN AFTER MIDNIGHT. BOTH THE
LIGHT SOUTHWEST WIND AND INCREASING CLOUDS WILL STUNT RADIATIONAL
COOLING FOR MIN TEMPS IN THE MID TO UPPER 40S. THE EXCEPTION WILL BE
THE TYPICALLY COOLER LOCATIONS IN THE THUMB...ESPECIALLY TOWARD PORT
HURON...WHERE CLOUDS WILL BE LATER TO ARRIVE BY SUNRISE MONDAY.

LONG TERM...MONDAY THROUGH SATURDAY

THE NEW WEEK WILL START OFF WITH A COLD FRONT AND RAIN ON MONDAY
BEFORE DRYING OUT FOR THE REMAINDER OF THE WEEK. THE OVERALL PATTERN
LOOKS TO CHANGE VERY LITTLE THROUGH MID WEEK WITH DOMINATE UPPER LOW
OVER EASTERN CANADA HOLDING THE UPPER LEVEL TROUGH OVER THE GREAT
LAKES. MODELS WERE TRYING TO RELEASE THE WEST COAST RIDGE AND PUSH
THE TROUGH TO THE EAST BUT THE LAST TWO RUNS HAVE SLOWED THAT
SCENARIO. STILL LOOKS LIKE WE COULD SEE A WARMUP BACK INTO THE 70S
BUT NOT TIL THE WEEKEND.

A SHORTWAVE LIFTING FROM THE HEADWATERS OF THE MISSISSIPPI INTO
NORTHERN QUEBEC TONIGHT WILL LAY OUT A COLD FRONT WHICH WILL THEN
DROP SOUTHWARD THOUGH LOWER MI ON MONDAY. A SECOND SHORTWAVE WILL
DIVE THROUGH THE EASTWARD DRIFTING RESIDENT LONGWAVE TROUGH WHICH
WILL TRACK ALONG THE MI/OH BORDER LATE MONDAY. THE COMBINATION OF
THE COLD FRONT AND THE SHORT WAVE WILL LEAD TO THE NEXT CHANCE OF
PRECIPITATION MONDAY AFTERNOON INTO MONDAY NIGHT. MODELS ARE IN
GOOD AGREEMENT WITH FRONTAL STRUCTURE AND TIMING OF THE SYSTEM
THIS GO AROUND...BUT HAVE NOT HAD GOOD RUN TO RUN CONSISTENCY WITH
THE LOCATION OF THE STRONGEST FORCING AND THUS QPF. THE COLD FRONT
WILL BE RUNNING INTO THE RIDGE THAT IS IN PLACE CURRENTLY OVER THE
LAKE WHICH WILL SLOW ITS PROGRESS INTO SE MI. THE DEEP DRY LAYER
WILL ALSO HELP EVAPORATE THE AVAILABLE MOISTURE AND LEAD MOIST
GRADIENT. BEST FORCING NOW LOOKS TO FALL ACROSS FAR SOUTHERN MI IN
RESPONSE TO THE COMPACT VORT MAX AND LEAD DIFFLUENT REGION WITH
UPPER JET MAX OVERHEAD. ALSO...THE NOSE OF THE THETA E RIDGE LOOKS
TO REACH INTO SOUTHERN MI UP TO AROUND M59. NOT AN OVERLY
IMPRESSIVE AMOUNT OF MOISTURE WITH THE SETUP AS PWATS HOVER AROUND
1 INCH. DECIDED TO INCREASE POPS TO LIKELY ACROSS THE FAR SOUTH TO
ACCOUNT FOR THE MOST FAVORABLE AREA RAIN SHOWERS. INHERITED TIMING
STILL LOOKS GOOD WITH BEST CHANCE COMING FROM ABOUT 21Z-03Z.

HIGH PRESSURE IN THE WAKE OF THE FRONT WILL BUILD BACK ACROSS THE
SOUTHERN GREAT LAKES MONDAY NIGHT AND WILL LAST THROUGH MID WEEK.
WITH LITTLE PROGRESSION WITH THE LONGWAVE TROUGH WE CAN EXPECT TEMPS
TO HOLD STEADY...HIGHS IN THE MID 60S AND LOWS IN THE MID
40S...MONDAY AND TUESDAY. CLOUDS ASSOCIATED WITH THE FRONT...AND CAA
BEHIND IT...WILL TRY TO HOLD THROUGH MONDAY NIGHT BEFORE DRIER AIR
SCATTERS THEM OUT FOR TUESDAY.

WEDNESDAY THROUGH SUNDAY:
MODELS STILL SHOWING HIGH PRESSURE PREVAILING FOR THE SECOND HALF
OF THE WEEK...KEEPING DRY CONDITIONS AND BELOW NORMAL TEMPERATURES
IN THE FORECAST THROUGH FRIDAY. BY FRIDAY NIGHT...THE CENTER OF
THAT RIDGE WILL HAVE SHIFTED WELL TO THE EAST ALLOWING THE NEXT
WEATHER SYSTEM TO BEGIN INFLUENCING CONDITIONS OVER SOUTHEAST
MICHIGAN. LOW PRESSURE OVER THE CENTRAL PLAINS WILL PUSH
EAST...AND MOISTURE FROM THIS LOW WILL BE FUNNELED INTO THE
REGION...RIDING UP THE BACKSIDE OF THE HIGH PRESSURE RIDGE THAT
WAS FORMERLY OVER OUR AREA. CHANCES OF RAIN WILL BE POSSIBLE FOR
THE WEEKEND.

MARINE...

HIGH PRESSURE ACROSS THE EASTERN GREAT LAKES WILL CONTINUE TO LIMIT
GUST POTENTIAL AND WAVE HEIGHTS ACROSS THE REGION. SOUTHWESTERLY
FLOW WILL CONTINUE INTO MONDAY AS THE GRADIENT TIGHTENS AHEAD OF A
COLD FRONT. THIS COLD FRONT WILL PHASE WITH A SYSTEM TO BRING THE
CHANCE OF SHOWERS MONDAY AFTERNOON AND EVENING. WINDS WILL VEER TO
THE NORTHWEST BEHIND THE FRONT FOR MONDAY NIGHT. HIGH PRESSURE WILL
THEN SETTLE IN FOR THE BETTER PART OF THE WEEK.

&&

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

&&

$$

AVIATION.....JVC
SHORT TERM...BT
LONG TERM....DRK/DE
MARINE.......DRK


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





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