Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 210744
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
344 AM EDT MON APR 21 2014

.SHORT TERM...TODAY AND TONIGHT

FORECAST REASONING HAS CHANGED LITTLE FOR THIS FORECAST PACKAGE.
EXPECT A VERY MILD DAY TODAY AS SOUTHWEST FLOW DEVELOPS IN ADVANCE
OF AN APPROACHING LOW PRESSURE SYSTEM AND COLD FRONT. FOR MOST OF
THE AREA...WILL MAINTAIN THE CURRENT MAXIMUM TEMPERATURE FORECAST IN
THE MIDDLE 70S...BUT WILL LOWER THE FAR NORTHERN SAGINAW VALLEY AND
THUMB CLOSER TO 70 AS CLOUD COVER WILL BE MORE PREVALENT AS SHOWER
ACTIVITY DEVELOPS EARLIER IN THE DAY IN THESE AREAS.

OTHERWISE...RELATIVELY WEAK SOUTHERN STREAM SHORTWAVE IS STILL
FORECAST TO BE PULLED NORTHEAST INTO THE AREA THIS AFTERNOON IN
ADVANCE OF A MUCH STRONGER POLAR SHORTWAVE DIGGING INTO THE GREAT
LAKES LATE TODAY INTO TONIGHT. TIMING OF THESE FEATURES STILL
SUGGEST THAT SCATTERED SHOWERS WILL BECOME INCREASINGLY LIKELY
THROUGH THE COURSE OF THE AFTERNOON...WITH THE BEST CHANCE OF
SHOWERS THEN COMING IN THE 00Z-06Z TIME FRAME AS A LOW PRESSURE
SYSTEM PASSES JUST NORTH OF THE CWA AND PULLS A COLD FRONT INTO THE
AREA DURING THE EVENING.

WILL MAINTAIN A MENTION OF THUNDER AS THE STRONG WARMING TODAY DOES
ALLOW FOR SOME MARGINAL INSTABILITY OVER THE AREA...DESPITE A
DECIDED LACK OF LOW LEVEL MOISTURE...SURFACE DEWPOINTS 45-50F. ANY
RESIDUAL INSTABILITY WILL BE FORCED FAIRLY DECENTLY BY THE COLD
FRONTAL BOUNDARY AS POLAR SHORTWAVE AMPLIFIES NOTABLY AS IT MOVES
INTO THE REGION LATE. THE PASSAGE OF THE COLD FRONT WILL LEAD TO AN
END TO SHOWER/THUNDERSTORM ACTIVITY OVERNIGHT...GENERALLY AFTER 08Z
OR SO. TEMPERATURES WILL BEGIN COOLING DOWN...BUT GIVEN THE LATE
ARRIVAL OF THE COLD AIR...MINIMUM TEMPERATURES WILL RANGE NEAR 40
OVER THE FAR NORTHWEST CWA TO 50 DETROIT SOUTH.

&&

.LONG TERM...TUESDAY THROUGH NEXT SUNDAY

ENERGETIC LOW AMPLITUDE LONGWAVE PATTERN WILL BECOME MORE AMPLIFIED
ON TUESDAY AS A DEEPENING TROUGH OVER THE WEST COAST HAS A RIPPLING
EFFECT DOWNSTREAM. THIS WILL DRAW THE JET STREAM AS A WHOLE
SOUTHWARD OVER THE GREAT LAKES WHICH WILL RESULT IN THE NEXT FEW MID
LATITUDE CYCLONES TARGETING SOUTHERN MI. THIS WILL ALSO BRING COOLER
AIR BACK TO THE STATE...ESPECIALLY IN THE WAKE OF THE
LOWS...BRINGING SLIGHTLY BELOW NORMAL TEMPERATURES BACK INTO THE
FORECAST.

THE FIRST LOW WILL BE EXITING THE AREA BY TUESDAY MORNING WITH THE
COLD FRONT WELL THROUGH THE AREA BY THEN. A TRAILING TROUGH WILL BE
DROPPING DOWN THROUGH THE EASTERN GREAT LAKES THOUGH AS COOLING HIGH
PRESSURE SYSTEM BEGINS TO BUILD INTO THE AREA. THIS WILL BRING A
SLIGHT CHANCE OF SOME RAIN SHOWERS TO OUR EASTERN COUNTIES AS
NORTHERLY FLOW INCREASES CAA WHICH STEEPENS LL LAPSE RATES WITH
UPPER LEVEL LIFT COINCIDENT TO IT. MODELS ALSO CONTINUE TO ADVERTISE
ELEVATED WIND SPEEDS/GUSTS IN THE AFTERNOON. DEPTH OF MIXING WILL
REACH AROUND 850-900 MB DURING PEAK HEATING WHICH WILL TRY TO BRING
SOME HIGHER GUSTS TO THE SFC. WINDS UP TO 850MB ARE FORECAST TO PEAK
AT AROUND 30 KNOTS WHICH WILL PUT A CAP ON WIND POTENTIAL. MODEL
SOUNDINGS SUGGEST IT WILL TAKE TIL CLOSE TO 18Z BEFORE WE MIX OUT SO
MAY SEE WINDS PICK UP AFTER 16Z FOR A FEW HOURS BEFORE DIURNAL
PROCESSES CEASE. LOOK FOR GUSTS TO REACH 25 TO 30 MPH. WITH COOL
HIGH PRESSURE SETTLING IN OVERNIGHT...TEMPS WILL DROP ONCE AGAIN TO
NEAR THE FREEZING MARK.

WE WILL SEE THE NEXT CHANCE OF PRECIP TOWARD THE END OF THE WORK
WEEK AS AN OCCLUDED SFC LOW TIED TO A MID LEVEL LOW OVER THE
NORTHERN PLAINS HAS NEW DEVELOPMENT ALONG THE SOUTHEASTWARD
EXTENDING COLD FRONT WHICH IS SURGING OUT WELL OUT AHEAD OF IT. THE
NEW SFC LOW IS UNDER A SHORTWAVE DROPPING THROUGH THE TROUGH WHICH
IS WORKING THROUGH THE PLAINS AT THAT TIME. THE PAIR OF SURFACE
FEATURES LOOK TO PHASE TOGETHER AS THE MID LEVEL TROUGH STALLS OVER
THE GREAT LAKES. WE WILL SEE SOME SHOWERS LATE THURSDAY INTO FRIDAY
AS THE NEW LOW LIFTS THROUGH SOUTHERN MI AND A SECOND BATCH OF
SHOWERS AS THE PRIMARY LOW DROPS INTO THE AREA FRIDAY NIGHT. THE
BAROCLINIC ZONE LOOKS TO RESIDE SOUTH OF THE AREA WITH NORTHEASTERLY
FLOW OVER THE REGION THROUGH THE END OF THE WEEKEND KEEPING THE AREA
SLIGHTLY BELOW NORMAL.

&&

.MARINE...

CONDITIONS WILL START OFF FAIRLY QUIET AS A FRONTAL BOUNDARY REMAINS
DRAPED ACROSS NORTHERN LAKE HURON. IN ADDITION THE WESTERN EXTENT OF
A HIGH PRESSURE SYSTEM WILL KEEP SOME INFLUENCE OVER THE EASTERN
LAKES AS WELL. THIS WILL KEEP A VERY STABLE AIRMASS IN PLACE THROUGH
THE DAY TODAY BEFORE A DEVELOPING LOW PRESSURE SYSTEM PASSES THROUGH
LAKE HURON LATE MONDAY EVENING PULLING A COLD FRONT THROUGH THE
REGION. WINDS WILL SWITCH TO NORTHWESTERLY BEHIND THE FRONT WHICH
WILL BRING COLDER AND MORE UNSTABLE AIR OVER THE LAKES BY TUESDAY
MORNING. WINDS WILL BECOME GUSTY BUT SHOULD BE LIMITED TO AROUND 25
KNOTS DUE TO REDUCED FLOW ALOFT. THIS SHOULD KEEP ANY GALES FROM
FORMING BUT MAY BE SUFFICIENT FOR SMALL CRAFTS...ESPECIALLY ALONG
THE LAKE HURON SHORELINE WHERE WAVES HEIGHTS WILL BE PILING UP. HIGH
PRESSURE WILL THEN BRING CALMING CONDITIONS THROUGH THE MIDDLE OF
THE WEEK BEFORE SOUTHWEST TO WEST WINDS INCREASE LATE IN THE WEEK
WITH THE APPROACH OF THE NEXT LOW PRESSURE SYSTEM.

&&

.AVIATION...ISSUED 1150 PM EDT SUN APR 20 2014

//DISCUSSION...

SKIES REMAIN CLEAR BELOW 10KFT TONIGHT AND MONDAY GIVEN THE
EXISTENCE OF A VERY DRY LOW LEVEL ENVIRONMENT.  A LIGHT SOUTH TO
SOUTHEAST WIND TONIGHT WILL VEER TO SOUTHWEST WHILE INCREASING INTO
THE 10 KNOT RANGE ON MONDAY.  THE ARRIVAL OF A FRONTAL BOUNDARY WILL
BRING AN INCREASING CHANCE FOR SHOWERS IN LOWER CEILINGS MONDAY
EVENING/NIGHT.  ISOLATED POTENTIAL FOR THUNDERSTORMS...PROBABILITY
TOO LOW TO INCLUDE A MENTION AT THIS TIME.

//DTW THRESHOLD THREATS...

* NONE

&&

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

&&

$$

SHORT TERM...DG
LONG TERM....DRK
MARINE.......DRK
AVIATION.....MR


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






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