Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 200156
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
956 PM EDT SAT JUL 19 2014

.UPDATE...

FORECAST LOOKS GOOD EXCEPT FOR THE PESKY CLOUDS THAT ARE BELOW THE
DEVELOPING INVERSION. ALL OF THE SHOWERS HAVE ENDED AS THE UPPER
WAVE HAS MOVED INTO THE EASTERN LAKES. THERE IS STILL A PATCH OF
THE REMNANT CU ACROSS MID MI...BUT THAT IS ABOVE THE INVERSION AND
SHOULD CONTINUE TO SHRINK. THE CLOUDS OVER THE THUMB ARE AT 1500
TO 2500 FEET. WITH THE EASTERLY FLOW OFF OF THE LAKES...THE
INVERSION DEVELOPING JUST ABOVE THIS LAYER AND LITTLE FLOW...EXPECT
THESE CLOUDS WILL BE DIFFICULT TO DISSIPATE. LATEST SATELLITE TRENDS
ARE SHOW THAT THE CLOUDS ARE NOT REALLY EXPANDING EITHER. WILL
UPDATE TO BE A LITTLE MORE PESSIMISTIC WITH THE CLOUDS FOR THE
THUMB AND AREAS ALONG AND EAST OF THE IRISH HILLS (TO THE HILLS IN
OAKLAND/LAPEER COUNTIES).

THIS IS THE SAME REGION THAT I ALREADY EXPANDED THE PATCHY FOG TOO
WITH THAT MOIST EAST FLOW. DO NOT THINK THE FOG WILL GET TOO BAD
GIVEN THE STRATOCU THAT WILL BE AROUND AND THE BATCH OF CI OVER WI THAT
MOVE OVER TONIGHT.

&&

.AVIATION...ISSUED 656 PM EDT SAT JUL 19 2014

//DISCUSSION...

SHOWERS HAVE DISSIPATED AND THE CUMULUS/STRATOCUMULUS ARE
DISSIPATING QUICKLY AS WELL. ONLY CLOUDS EXPECTED FOR THE BULK OF
THE NIGHT IS AN AREA OF BKN CIRRUS OVER THE UPPER MISSISSIPPI RIVER
VALLEY AND WESTERN GREAT LAKES THAT WILL THIN AS THEY OVERSPREAD
LOWER MICHIGAN. BIGGEST FORECAST CHALLENGE IS THE DEVELOPMENT OF FOG.
MODELS CONTINUE TO BE ROBUST WITH THE DEVELOPMENT OF FOG OVER
SOUTHEAST LOWER MICHIGAN. FOG DID DEVELOP LAST NIGHT JUST SOUTHWEST
OF THE UPPER LOW THAT AFFECTED US TODAY. HOWEVER...SURFACE
TRAJECTORIES ARE NOT EXACTLY COMING FROM THE OHIO AND MS RIVER
CONFLUENCE REGION. THE LIGHT EASTERLY FLOW OFF OF THE LAKES WOULD
LEAN TOWARD FOG...BUT THE BKN CI CANOPY DOES NOT.  WILL FORECAST
SOME LIGHT MVFR FOG AND ASSES THROUGH THE EVENING HOURS.

FOR DTW...MAY BE THE MOST LIKELY LOCATION TO HAVE THE LOWEST
VISIBILITIES GIVEN THE HIGHER DEW POINTS...SLIGHTLY MORE RURAL
LOCATION THAN DET AND ITS PROXIMITY LAKES ERIE AND ST. CLAIR. WILL
STILL KEEP IT MVFR.

//DTW THRESHOLD THREATS...

* MEDIUM CONFIDENCE IN MVFR VSBYS BETWEEN 08Z AND 13Z SUN.

&&

.PREV DISCUSSION...ISSUED 354 PM EDT SAT JUL 19 2014

SHORT TERM...THROUGH TONIGHT

WELL-DEFINED AREA OF UPPER LOW PRESSURE CAN BE SEEN ON WATER VAPOR
IMAGERY TRACKING NORTHWARD ACROSS LAKE HURON. WEAK MID-LEVEL
DEFORMATION ZONE DROPPING BACK DOWN AROUND THE WESTERN FLANK OF
THIS SYSTEM SHOULD STILL BE LINGERING DOWN FROM THE THUMB TO ABOUT
PTK PER 12Z GFS. THIS IS WHERE RADAR SHOWS A FEW LIGHT SHOWERS STILL
ONGOING. ACTIVITY GOT A BIT OF A BOOST FROM DAYTIME HEATING EARLIER
THIS AFTERNOON...BUT HAS REALLY DROPPED OFF IN THE LAST HOUR AS
FORCING WEAKENS AND STARTS TO LIFT NORTH. EXPECT LOW SHOWER COVERAGE
TO LINGER THROUGH THE EARLY EVENING BEFORE THE LOW MOVES TO THE
ONTARIO/QUEBEC BORDER AND HIGH PRESSURE NEAR THE NEW ENGLAND COAST
EXPANDS BACK INTO THE AREA.

HIGH PRESSURE AND DRIER ARRIVING IN THE LOW AND MID LEVELS SHOULD
ALLOW FOR LIGHT WINDS BY LATE THIS EVENING AND A CLEARING TREND TO
SKY COVER. NAM/RAP FORECAST SOUNDINGS HINT AT SOME SHALLOW FOG
FORMATION LATE TONIGHT AS A SHALLOW SURFACE-BASED INVERSION FORMS
AND SURFACE TEMPERATURES CRASH TO THE DEWPOINTS. THIS COULD BE
INFLUENCED BY OVERLY ZEALOUS MODEL QPF FOR TODAY...BUT DO SEE SOME
POTENTIAL FOR FOG TO DEVELOP AS THE SHALLOW INVERSION FORMS...WINDS
REMAIN LIGHT FROM OFF THE GREAT LAKES...AND SURFACE DEWPOINTS REMAIN
IN THE UPPER 50S TO NEAR 60. DID INCLUDE A PATCHY MENTION OF FOG FOR
THE FAR EASTERN PORTION OF THE AREA WHERE MORE SHOWERS OCCURRED
TODAY. OTHERWISE...WEATHER SHOULD BE QUIET TONIGHT WITH MINS IN THE
LOW/MID 50S TO NEAR 60.

LONG TERM... SUNDAY THROUGH NEXT SATURDAY

THE SHORT WAVE ALOFT OVER THE OHIO VALLEY TODAY CARVED OUT A
WEAKNESS WITHIN THE LARGER BACKGROUND OF BROAD SURFACE HIGH
PRESSURE. THE WEAKNESS IN THE PRESSURE FIELD WILL FILL IN BY SUNDAY
MORNING AS THE UPPER WAVE MOVES INTO THE NEW ENGLAND STATES AND
ALLOWS THE SURFACE HIGH TO REASSERT CONTROL OF THE WEATHER OVER SE
MICHIGAN. BASED ON THE UPSTREAM CUMULUS RESPONSE TODAY...THE CLOUD
FORECAST IS NUDGED TOWARD 50/50 COVERAGE IN OUR AREA DURING SUNDAY
AFTERNOON...BUT THAT IS ABOUT ALL THE FORECAST ADJUSTMENTS NEEDED AS
DRY CONDITIONS LOOK SOLID. DESPITE UPSTREAM CUMULUS DEVELOPMENT
WITHIN THE SURFACE RIDGE...CONCERN FOR SHOWERS OR STORMS IS EASED BY
12Z SOUNDINGS THAT INDICATE A RESPECTABLE CAPPING INVERSION THROUGH
THE MIDWEST OBSERVATION SITES. MODEL SOUNDINGS CAPTURE THIS WARMER
AIR ALOFT MOVING OVER LOWER MICHIGAN DURING PEAK HEATING SUNDAY
AFTERNOON ADDING CONFIDENCE TO THE EXPECTATION FOR DRY WEATHER. MORE
NOTABLE IS THE RETURN TO MORE TYPICAL JULY TEMPERATURES AND MODERATE
HUMIDITY. NO PROBLEM WITH GUIDANCE OFFERINGS IN THE LOWER 80S MOST
LOCATIONS AWAY FROM THE LAKE HURON SHORELINE.

UPPER LEVEL TROUGH DEVELOPMENT OFF THE PACIFIC COAST WILL LEAD TO AN
ARM OF THE SW U.S. UPPER RIDGE BUILDING INTO THE GREAT LAKES DURING
THE FIRST HALF OF NEXT WEEK. THIS WILL LEAD TO A TEXTBOOK BERMUDA
HIGH PATTERN AT THE SURFACE AND ASSOCIATED WARM TEMPERATURE/HIGH
HUMIDITY AIR MASS AFFECTING THE WEATHER IN SE MICHIGAN MONDAY AND
TUESDAY. THERE IS GOOD MODEL AGREEMENT ON THE LARGE SCALE UPPER AIR
FEATURES AND AREAL COVERAGE OF THE CUSTOMARY 10C 700 MB TEMPERATURE
EXPECTED TO CAP OFF CONVECTION. THIS ADDS SOME CONFIDENCE TO THE
TEMPERATURE FORECAST PUSHING 90 BY TUESDAY WITHOUT TOO MUCH WORRY
ABOUT THUNDERSTORM COMPLEXES GETTING IN THE WAY OF DAYTIME HEATING.
THIS LEVEL OF CONFIDENCE IS THEN ERODED ALONG WITH THE UPPER RIDGE
BY A SOUTHWARD INTRUSION OF THE WESTERLIES FROM CANADA BY TUESDAY
NIGHT. THE INCREASED WESTERLY FLOW ALOFT AND LOW LEVEL JET
DEVELOPMENT OVER THE PLAINS HAS THE LOOK OF AN MCS PATTERN BY THEN.

WEAK HIGH PRESSURE WILL BE IN PLACE FOR TUESDAY ALLOWING WARMER AND
MORE HUMID AIR TO FILTER INTO SOUTHEAST MICHIGAN. AT THIS TIME
TEMPERATURES ARE EXPECTED TO RISE INTO THE UPPER 80S BY TUESDAY
AFTERNOON ACROSS THE ENTIRE CWA. HOWEVER...A LOW PRESSURE SYSTEM
BUILDING OUT OF THE NORTHERN PLAINS WILL TRACK ACROSS THE NORTHERN
GREAT LAKES REGION ON TUESDAY NIGHT...DRAGGING A COLD FRONT ACROSS
SOUTHEAST MICHIGAN. THIS FRONT WILL BRING A CHANCE OF RAIN AND
THUNDERSTORMS ON TUESDAY NIGHT AND WEDNESDAY BEFORE HIGH PRESSURE
BUILDS OUT OF CANADA AND INTO THE GREAT LAKES RESULTING IN DRY
CONDITIONS THROUGH THE END OF THE WEEK. THIS HIGH NOT ONLY WILL
BRING DRIER WEATHER TO THE AREA...BUT ALSO COOLER TEMPERATURES
BEGINNING ON WEDNESDAY WITH HIGHS IN THE LOW TO MID 80S.
TEMPERATURES CONTINUE TO DROP THROUGH THE END OF THE EXTENDED PERIOD
WITH TEMPERATURES IN THE MID 70S ON THURSDAY AND FRIDAY.

MARINE...

WIND AND WAVE CONDITIONS WILL REMAIN FAVORABLE OVER THE NEXT FEW
DAYS THANKS TO SURFACE HIGH PRESSURE REBUILDING OVER THE GREAT LAKES
SUNDAY AND LINGERING NEARBY TO THE EAST MONDAY AND TUESDAY. LIGHT
SOUTH WIND WILL PROMOTE STEADILY INCREASING TEMPERATURES THROUGH THE
PERIOD WHICH WILL LEAD TO HIGH STABILITY OVER THE LAKES
CORRESPONDING TO LOW WAVE ACTION. UNSETTLED WEATHER IN THE FORM OF
INCREASED THUNDERSTORM ACTIVITY IS EXPECTED BY MID WEEK ALONG AND
AHEAD OF A COLD FRONT DUE TO MOVE THROUGH THE REGION WEDNESDAY.

&&

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

&&

$$

UPDATE.......RBP
AVIATION.....RBP
SHORT TERM...HLO
LONG TERM....BT/RK
MARINE.......BT


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