Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 190758
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
358 AM EDT SUN OCT 19 2014

.SHORT TERM...TODAY AND TONIGHT

LOW STRATUS CLOUDS CONTINUE TO SCOUR OUT EARLY THIS MORNING AS
RIDGING BRINGS DRIER AIR IN FROM THE WEST. SOME RESIDUAL MOISTURE IS
PRESENT AS MOISTURE FROM THE GREAT LAKES IS FILTERED IN OVER THE
THUMB REGION AND SAGINAW VALLEY. THESE CLOUDS SHOULD EVENTUALLY
CLEAR UP LATER THIS MORNING AS THE RIDGE CONTINUES TO TRACK EAST AND
TURNS THE LOW LEVEL FLOW FROM A NORTHERLY TO A WESTERLY DIRECTION.
ALTHOUGH SKIES WILL BE MOSTLY SUNNY TODAY A COOL AIRMASS WILL REMAIN
IN PLACE AS TEMPERATURES ONLY MODERATE SLIGHTLY FROM YESTERDAY. WITH
SHALLOW MIXING HEIGHTS TO 900 MB HIGHS ARE EXPECTED TO GENERALLY BE
AROUND 50 DEGREES ACROSS SOUTHEAST MICHIGAN.

THE RIDGE WILL SLIDE EAST THIS AFTERNOON...SETTING THE STAGE FOR THE
NEXT LOW PRESSURE SYSTEM TO TRACK THROUGH THE NORTHERN GREAT LAKES
TONIGHT...ENDING UP OVER THE SOO BY LATE TONIGHT INTO EARLY MONDAY
MORNING. MOISTURE WITH THIS SYSTEM WILL BE AT A PREMIUM...WITH LOW
LEVEL DRY AIR INHIBITING HYDROMETEORS FROM REACHING THE GROUND. IN
ADDITION LIFT WITH THIS SYSTEM WILL NOT BE ALL THAT GREAT
TONIGHT...WITH THE BULK OF THE LIFT FURTHER NORTH CLOSER TO THE
SURFACE LOW AND OUT TO THE WEST THE THE ATTENDANT MID LEVEL TROUGH
AND SHORTWAVE. WITH THIS IN MIND WILL MAINTAIN THE CHANCY POPS
DURING THE OVERNIGHT HOURS...WITH HIGHER POPS ACROSS THE NORTH AND
LOWER POPS FURTHER SOUTH. WITH ABUNDANT CLOUD COVER AND MODELS WARM
AIR ADVECTION AHEAD OF THE APPROACHING LOW...OVERNIGHT LOWS ARE
EXPECTED TO REMAIN IN THE LOWER TO MIDDLE 40S.

&&

.LONG TERM... MONDAY THROUGH SATURDAY

ACTIVE NORTHERN PACIFIC JET CORE WILL PROMPT THE SOUTHEASTWARD
EJECTION AND DEEPENING OF SHORTWAVE ENERGY CURRENTLY NOTED ACROSS
NORTHERN ALBERTA OVER THE NEXT 48 HOURS.  THIS WILL PLACE THE CENTER
OF THE MAIN PV ANOMALY OVER LAKE MICHIGAN BY MID MORNING ON MONDAY.
LEAD WING OF MODEST MID LEVEL WARM AIR AND THETA-E ADVECTION WILL BE
ONGOING POST-DAYBREAK.  MODELS CONTINUE TO PRESENT A RATHER
DISORGANIZED PERIOD OF ASCENT WITH THIS PROCESS...BUT ENOUGH
EVIDENCE TO SUGGEST SOME POCKETS OF LIGHT SHOWERS WILL BE ONGOING
ACROSS SOUTHEAST MICHIGAN DURING THE MORNING PERIOD /PARTICULARLY
NORTH/.  RENEWED FORCING WILL EMERGE WITH THE PASSAGE OF THE MAIN
VORTICITY LOBE DURING THE AFTERNOON PERIOD...ASSOCIATED 500 MB
TEMPERATURES BOTTOMING OUT IN THE -23C RANGE DURING THIS TIME.
SUFFICIENT MOISTURE IN THE PROFILE BY THIS TIME TO SUPPORT
ADDITIONAL SHOWER DEVELOPMENT GIVEN SOME INCREASE IN LAPSE RATES AND
A PERIOD OF SOLID CVA.  THE ATTENDANT COLD FRONTAL PASSAGE COMES
MID-LATE AFTERNOON FROM NORTHWEST TO SOUTHEAST.  THIS FRONTAL TIMING
WILL YIELD ENOUGH RESIDENCE TIME OF A PRE-FRONTAL SOUTHWEST FLOW TO
ALLOW TEMPERATURES TO CLIMB INTO THE MIDDLE AND UPPER 50S.

ADDITIONAL SHORTWAVE ENERGY SHEARING INTO THE BACKSIDE OF THE
BURGEONING LONGWAVE TROUGH EXPECTED TO BUILD TOWARD THE EAST
COAST WILL SUSTAIN AN UNSETTLED/CYCLONIC MID LEVEL FLOW ACROSS SE
MICHIGAN THROUGH TUESDAY.  THIS WILL MAINTAIN A HIGH DEGREE OF CLOUD
COVER AND PROVIDE AT LEAST A CHANCE FOR SHOWER DEVELOPMENT.  WINDS
SHIFT TO NORTHEASTERLY WITH THE EXIT OF THIS SYSTEM AND IN RESPONSE
TO HIGH PRESSURE BUILDING ACROSS SOUTHERN ONTARIO.  TROUGH AXIS
DEFINING THIS WIND SHIFT MAY PROVIDE AN ADDITIONAL FOCUS FOR SHOWER
DEVELOPMENT DURING THIS TIME...PARTICULARLY ACROSS THE THUMB GIVEN
THE ADDED MOISTURE FLUX CONTRIBUTION OFF LAKE HURON.

EXITING LONG WAVE TROUGH EVOLVES INTO AN EXPANSIVE CLOSED LOW OFF
THE MID ATLANTIC COAST BY MIDWEEK.  NARROW HIGH AMPLITUDE RIDGING
WILL SLOWLY CREEP INTO THE GREAT LAKES DURING THIS TIME.  THIS LARGE
SCALE PATTERN WILL POSITION SE MICHIGAN FAVORABLY FOR SEEING AN
EXTENDED STRETCH OF CONDITIONS DICTATED BY LOW LEVEL HIGH PRESSURE.
THE INCREASING THICKNESS FIELD WILL RESULT IN A STEADY WARMING TREND
THROUGH THE END OF THE WEEK...DAYTIME HIGHS BACK UP AROUND 60
DEGREES BY FRI/SAT. STABLE ENVIRONMENT WITH A HIGH DEGREE OF MID
LEVEL SUBSIDENCE WILL SUPPORT DRY WEATHER THROUGH THIS TIME.

&&

.MARINE...

WINDS WILL EASE WHILE SHIFTING TO THE SOUTHWEST AS A RIDGE OF HIGH
PRESSURE PASSES THROUGH THE REGION.  A PERIOD OF STRONGER SOUTHWEST
WINDS OF 15 TO 20 KNOTS WILL DEVELOP TONIGHT AND EARLY MONDAY IN
ADVANCE OF A COLD FRONT.  THIS FRONT WILL BRING SCATTERED TO
NUMEROUS SHOWERS DURING THIS TIME.  POST-FRONTAL NORTHWEST WINDS
WILL INCREASE MONDAY EVENING.  WINDS WILL THEN VEER TO NORTHEASTERLY
MONDAY NIGHT AND TUESDAY AS HIGH PRESSURE BUILDS ACROSS ONTARIO.
THE COMBINATION OF THE STRONGER GRADIENT AND ONSHORE FLOW WILL BRING
A PERIOD OF GUSTY WINDS AND BUILDING WAVES THROUGHOUT CENTRAL AND
SOUTHERN LAKE HURON.  POTENTIAL FOR GUSTS INTO THE 30 KNOT
RANGE...WITH AT LEAST A LOWER PROBABILITY FOR A BRIEF PERIOD OF
MARGINAL GUSTS TO GALES OVER THE OPEN WATERS.  CONFIDENCE IN GALES
REMAINS TOO LOW TO ISSUE A GALE WATCH AT THIS TIME...BUT SMALL CRAFT
CONDITIONS APPEAR LIKELY FOR THIS PERIOD.

&&

.AVIATION...ISSUED 109 AM EDT SUN OCT 19 2014

//DISCUSSION...

DRY AIR HAS TAKEN A BIT LONGER TO MAKE ITS WAY OVER THE TAF SITES
THAN PREVIOUSLY EXPECTED...HOWEVER IT LOOKS TO HAVE FINALLY TAKEN
HOLD FROM FNT SOUTH TO THE METRO AIRPORTS. THE MAIN EXCEPTION IS MBS
WHERE LAKE CLOUDS CONTINUE TO BRING A SCT-BKN DECK AROUND 2500 TO
3000 FT. EVEN THESE CLOUDS ARE EXPECTED TO SCATTER OUT IN A FEW
HOURS AS THE FLOW TURNS WESTERLY...ENDING THE ADVECTION OF CLOUDS
FROM NORTHERN LOWER MICHIGAN. SUNDAY WILL BE A RATHER TRANQUIL DAY
AS RIDGING PASSES THROUGH THE CENTRAL GREAT LAKES. CLOUDS WILL
THICKEN SUNDAY EVENING AHEAD OF THE NEXT LOW PRESSURE SYSTEM
TRACKING THROUGH THE NORTHERN GREAT LAKES. ANY RAIN WITH THIS SYSTEM
IS EXPECTED TO HOLD OFF UNTIL VERY LATE IN THE TAF PERIOD OR INTO
THE NEXT ISSUANCE.

//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...KURIMSKI
LONG TERM....MR
MARINE.......MR
AVIATION.....KURIMSKI

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