Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 231911
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
311 PM EDT SAT MAY 23 2015

.SHORT TERM...THIS AFTERNOON AND TONIGHT

VERY QUIET WEATHER WILL PERSIST THROUGH TONIGHT AS A RIDGE OF
SURFACE HIGH PRESSURE EXTENDS BACK NORTHWEST ACROSS THE ENTIRE
REGION. LATE DAY TEMPERATURES WILL RANGE IN THE LOW TO MID 70S UNDER
PLENTY OF SUNSHINE AND SOUTH TO SOUTHWEST WINDS OF 10 MPH OR LESS IN
MOST CASES. THESE WINDS WILL BACK TO SOUTHEAST EARLY THIS EVENING IN
SOME LOCATIONS DUE TO LAKE BREEZE BOUNDARIES...BUT REMAIN 10 MPH OR
LESS.

WITH THE CENTER OF THIS HIGH PRESSURE POSITIONED FURTHER SOUTHEAST
OF THE AREA...SOUTH TO SOUTHWEST WINDS WILL REMAIN CLOSE TO 5 MPH
TONIGHT. THIS...COMBINED WITH A GENERAL MODERATION IN THE AIRMASS
OVER THE AREA...WILL RESULT IN MILDER TEMPERATURES TONIGHT WITH LOWS
GENERALLY IN THE 50 TO 55 DEGREE RANGE WITH UPPER 40S LIMITED TO
PARTS OF THE THUMB AND SPOTTY RURAL LOCATIONS ACROSS THE SAGINAW
VALLEY AND IRISH HILLS WEST AND SOUTHWEST OF METRO DETROIT.

&&

.LONG TERM...

TSTORMS ARE ONGOING IN THE GREAT PLAINS IN ADVANCE OF THE LARGE
CLOSED LOW SPINNING OVER THE GREAT BASIN. THIS THUNDERSTORM COMPLEX
WILL ULTIMATELY DIE WITH THE LOSS OF DIURNAL HEATING. REMNANTS WILL
BE DRAWN NORTHEAST AS THE GREAT BASIN LOW EJECTS INTO THE CENTRAL
PLAINS DURING THE DAY SUNDAY. SOUTHWESTERLY GRADIENT FLOW INTO SEMI
WILL PERSIST AROUND THE LARGE ANTICYCLONE ANCHORED OFF THE WEST
COAST. HIGHS IN THE UPPER 70S WILL BE THE RULE ALONG WITH DEWPOINTS
INCREASING INTO THE MID 50S BY SUNSET. ABUNDANT DRY AIR IN THE
LOWEST 6KFT IS EXPECTED TO SIGNIFICANTLY LIMIT THE POTENTIAL FOR
REMNANTS OF THE AFOREMENTIONED CONVECTION TO SURVIVE THEIR TRIP INTO
SE MICHIGAN, EVEN WITH THE HELP OF MARGINAL ISENTROPIC ASCENT
INCREASING BY SUNDAY NIGHT. CONVECTION-RESOLVING WRF-ARW/NMM SUPPORT
THIS EXPECTATION.

NEBULOUS SCENARIO THEN EXISTS FOR MONDAY. DEEP LAYER SOUTHWEST FLOW
WILL PERSIST, SENDING HIGHS INTO THE UPPER 70S/LOW 80S AND DEWPOINTS
INTO THE 60S. UPPER LOW WILL CONTINUE ITS TRANSITION TO A LOWER
AMPLITUDE OPEN WAVE AS IT LIFTS FROM OMAHA TO THE ARROWHEAD OF
MINNESOTA DURING THE DAY MONDAY. EXTENDED PERIOD OF MOISTURE
TRANSPORT WITHIN GUSTY SOUTHWEST FLOW WILL ALLOW PWATS TO RISE TO
1.7 INCHES, WHICH WOULD BE A RECORD FOR THE DATE PER LOCAL UPPER AIR
DATABASE. LAPSE RATES WILL BE QUITE POOR AND FLOW WILL BE
ANTICYCLONIC THROUGH THE LAYER, EVEN IF ONLY WEAKLY SO AT THE
SURFACE. CLOUDS WILL LIMIT INSTABILITY POTENTIAL, THOUGH THERE IS
SOME POTENTIAL FOR AN MCV ORIGINATING OUT OF ARKLATEX AREA
CONVECTION TO LIFT TOWARD THE AREA LATE MONDAY. THIS REPRESENTS THE
ONLY DISCERNIBLE TRIGGER MECHANISM. BLANKET POPS REMAIN WARRANTED
FOR MONDAY, BUT DECIDEDLY PULLED BACK FROM LIKLIES. THE ECMWF
APPEARS TO BE THE ONLY MEMBER OF THE 12Z SUITE WITH A QPF OUTPUT
THAT CLOSELY MATCHES ITS OWN FORCING FIELDS. THE ONLY CERTAINTY FOR
MONDAY IS THAT IT WILL BE WARM AND MUGGY.

SOUTHWEST FLOW WILL PERSIST INTO MONDAY NIGHT LEADING TO ANOTHER
HUMID NIGHT WITH LOWS RUNNING 10 TO 15 DEGREES ABOVE NORMAL.

A FAIRLY ACTIVE PATTERN REMAINS FOR THE EXTENDED PERIOD AS A
SERIES OF LOW PRESSURE SYSTEMS ARE FORECASTED TO IMPACT SOUTHEAST
MICHIGAN. RAIN AND THUNDERSTORM CHANCES WILL REMAIN IN PLACE FROM
TUESDAY THROUGH THE END OF THE WEEK. HAVE ONLY INCLUDED CHANCE POPS
INTO THE FORECAST FOR NOW TO ACCOUNT FOR UNCERTAINTY IN THE TIMING
OF THESE SYSTEMS. OTHER THAN RAIN...HIGH TEMPERATURES WILL REMAIN
STEADY IN THE MID 70S TO LOW 80S THROUGH FRIDAY WHICH WILL BE ABOVE
NORMAL FOR THIS TIME OF YEAR /NORMAL IS LOW 70 DEGREES/.

&&

.MARINE...

WINDS WILL DIMINISH THIS EVENING AS THE PRESSURE GRADIENT RELAXES
AND WILL REMAIN LIGHT THROUGH THE WEEKEND. A MODERATE SOUTHERLY
BREEZE WILL DEVELOP DURING THE DAY MONDAY WITH GUSTS IN EXCESS OF 25
KNOTS POSSIBLE. SMALL CRAFT ADVISORIES FOR WIND WILL BE POSSIBLE FOR
ALL NEARSHORE ZONES. WAVE IMPACTS WILL BE MINIMIZED DUE TO LACK OF
ONSHORE FLOW. THUNDERSTORMS WILL BE POSSIBLE OVER NORTHERN LAKE
HURON SUNDAY NIGHT THROUGH MONDAY. THE BEST THUNDERSTORM CHANCES FOR
AREAS FURTHER SOUTH WILL BE MONDAY EVENING.

&&

.AVIATION...ISSUED 1252 PM EDT SAT MAY 23 2015

SSW FLOW AROUND 10 KTS WILL PREVAIL ON THE WEST SIDE OF LARGE HIGH
PRESSURE POSITIONED TO THE EAST OF THE AREA. WINDS WILL BACK TO SSE
FOR A TIME LATE TODAY WITH LAKE BREEZE(S) AND REMAIN LIGHT SOUTHERLY
OVERNIGHT BEFORE MIXING TO SSW AGAIN LATE SUNDAY MORNING. SKIES WILL
REMAIN MAINLY CLEAR TODAY WITH JUST INCREASING MID/UPPER LEVEL
MOISTURE LATER TONIGHT INTO SUNDAY. BKN-OVC CIGS OF 20KFT WILL BE
POSSIBLE BY 14Z-16Z SUNDAY WITH PERHAPS 10KFT CIGS AFTER 18-20Z AS
AN ISOLATED SHRA POPS UP IN DAYTIME HEATING.

//DTW THRESHOLD PROBABILITIES...

* NONE.

&&

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

$$

SHORT TERM...DG
LONG TERM....JVC/RK
MARINE.......JVC
AVIATION.....DG


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


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