Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 241118
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
718 AM EDT SUN MAY 24 2015


.AVIATION...

AN UPPER LEVEL RIDGE AXIS OVER SOUTHEASTERN MICHIGAN WILL KEEP
AVIATION WEATHER QUIET THROUGH MUCH OF THE TODAY PERIOD. SSW WINDS
ARE EXPECTED TO INCREASE AS THE ATMOSPHERE MIXES OUT DUE TO DAYTIME
HEATING. WILL WATCH RAIN ACTIVITY OVER ILLINOIS ADVANCE NORTHWARD
THIS MORNING AND AFTERNOON. EXPECTATIONS ARE FOR THE RAIN TO
INCREASE IN COVERAGE...EVENTUALLY SPREADING ACROSS THE SAGINAW
VALLEY BY THIS EVENING. THE POTENTIAL DOES EXIST FOR THUNDERSTORM
ACTIVITY OVER THE SAGINAW BAY REGION...ALTHOUGH THE POTENTIAL
REMAINS TO LOW TO INCLUDE IN THE TAF FORECAST. DEEP DRY AIR NEAR THE
SURFACE WILL LIMIT THE ELEVATED RAIN SHOWERS FROM REACHING THE
GROUND FOR AREAS SOUTH OF KMBS. DRY CONDITIONS ARE EXPECTED TO
PERSIST FOR KFNT SOUTHWARD.


//DTW THRESHOLD PROBABILITIES...

* NONE.

&&

.PREV DISCUSSION...ISSUED 410 AM EDT SUN MAY 24 2015

SHORT TERM...TODAY AND TONIGHT

THE CONTROL OF THE WEATHER PATTERN LOCALLY CONTINUES TO BE THE SE US
UPPER LEVEL RIDGE. SOUTHEASTERN MICHIGAN WILL BE POSITIONED WITHIN
THE FORWARD FLANK OF THIS FEATURE WITH H3-H5 AXIS REMAINING
SOUTHWEST OF THE CWA THROUGH 6Z TONIGHT. AS A RESULT...LOOKING AT
PERSISTENCE THROUGH THE FIRST 12 HOURS OF THE FORECAST PERIOD WITH
EVOLUTION IN THE PATTERN ONLY BEGINNING AS 850MB-500MB WINDS
EVENTUALLY TURNS SOUTHWESTERLY BETWEEN 00-06Z TONIGHT.

MILDER TEMPERATURES THIS MORNING WILL YIELD A QUICK WARMUP TODAY
WITH THE HOURLY TRACE SUGGESTING READINGS WILL PUSH THE UPPER 70S TO
NEAR 80 DEGREES BY NOON. THE GENERAL IDEA IS FOR A FAIR AMOUNT OF
SUNSHINE THIS MORNING BEFORE VEIL OF HIGH CLOUDS LIFT NORTHWARD AND
THICKEN FOR THE AFTERNOON. TEMPERATURES WILL THEN HOLD FAIRLY STEADY
FOR A GOOD PART OF THE DAY AT/AROUND 80 DEGREES.

THE ARRIVAL OF LOW LEVEL JET KINEMATICS INTO THE FACE OF THE WELL
DEFINED RIDGE AXIS WILL STRENGTHEN THE LEAD WING OF 850-500MB
DEFORMATION ACROSS PORTIONS OF WISCONSIN AND LOWER MICHIGAN BY THE
LATE MORNING. PREXISTING SHOWER ACTIVITY...NOW DEVELOPING OVER NORTH
CENTRAL ILLINOIS...IS EXPECTED TO UNDERGO UPSCALE GROWTH THEN TODAY
WHILE STRINGING OUT ALONG THE INCREASING DEFORMATION FORCING. THE
QUESTIONS ARE TO WHAT EXTENT THIS PRECIPITATION WILL SPILL EASTWARD
INTO THE NORTHERN CWA AND TIMING. WILL RELY ON THE DEEP DRY AIR
IN THE LOWEST 7 KFT AGL TO KEEP COVERAGE MINIMAL AFTER 21Z. DID
INCREASE POPS TO A HIGH CHANCE FOR THE SAGINAW VALLEY. WILL
MAINTAIN THE CHANCE OF THUNDER FOR TONIGHT DESPITE POOR
THERMODYNAMIC SUPPORT. THE POOR THERMODYNAMIC SUPPORT RESULTS
FROM LACKLUSTER MIDLEVEL LAPSE RATES AND THE DEPTH OF NEAR
SURFACE DRY AIR PUSHING LCL HEIGHTS AS HIGH AS 8-9 KFT. NO STRONG
OR SEVERE WEATHER IS EXPECTED LATE THIS AFTERNOON OR TONIGHT.

TONIGHT...SYNOPTIC SCALE DEFORMATION FORCING WILL ADVANCE NORTHWARD
INTO NORTHERN LOWER MICHIGAN...LEAVING SEMICH UNDER CONTINUED
RIDGING ALOFT WITH NO NEAR SURFACE FORCING MECHANISM. AS A
RESULT...KEPT POPS OUT OF THOSE AREAS SOUTH OF I 69.

LONG TERM...MONDAY THROUGH SATURDAY

LITTLE CHANGE IN GUIDANCE WITH THE OVERALL LONGWAVE PATTERN THAT
WILL GUIDE THE FORECAST FOR THE UPCOMING WEEK. STRONG RIDGE WILL
HOLD OVER THE EASTERN SEABOARD WITH A DEEP UPPER LOW STALLING OVER
HUDSON BAY. IN ADDITION...A ONCE CLOSED LOW OVER THE DESERT SW
WITHIN A BROAD MID/UPPER TROUGH...WILL SLOWLY WEAKEN AND BECOME AN
OPENED WAVE WHILE IT TRACKS INTO THE PLAINS BY MID WEEK. IT WILL
THEN LIFT NE INTO ONTARIO THROUGH THE WESTERN GREAT LAKES LATER IN
THE WEEK. THE CHALLENGE FOR THE LONGTERM FORECAST WILL BE TO
CONTINUE TO PINPOINT THE TIMING OF THE MANY SHORTWAVES EJECTING OUT
OF THE WESTERN CONUS TROUGH THAT WILL LIFT THROUGH THE AREA.

THE NW EXTENSION OF THE RIDGE OVER THE SE CONUS WILL HOLD ACROSS THE
GREAT LAKES AS THE UPPER LEVEL JET AHEAD OF THE APPROACHING TROUGH
IS ORIENTED N/S. THIS WILL CONTINUE TO MAKE IT DIFFICULT FOR THE
ELEVATED SYNOPTIC FEATURES TO AMOUNT TO MUCH PRECIP AT THE SFC. THE
FIRST OPPORTUNITY FOR SHOWERS AND THUNDERSTORMS WILL COME LATER IN
THE AFTERNOON ON MEMORIAL DAY. A FAIRLY DECENT SHORTWAVE WILL EJECT
OUT OF THE BASE OF THE TROUGH OVER TEXAS TRAVELING NNE ALONG THE
MISSISSIPPI VALLEY. A STRENGTHENING JET WILL SURGE NE ACROSS LAKE MI
BETWEEN 18-00Z MONDAY AFTERNOON/EVENING. A SFC LOW WILL TRAVEL UP
THROUGH WI/MN LIFTING A WARM FRONT THROUGH SOUTHERN MI DURING THIS
TIME. DRY LL CONDITIONS WILL MAKE IT DIFFICULT FOR ANY PREFRONTAL
PRECIP BUT A SURGE OF DEEP MOISTURE BEING USHERED IN BEHIND THE
FRONT WILL ALLOW FOR A PERIOD OF CHANCE POPS. NAM BUFKIT SOUNDINGS
ADVERTISE PWATS TO JUST FROM 1.3 INCHES BEFORE THE FRONT TO OVER 1.7
INCHES IN THE WARM SECTOR. MODEL DO ADVERTISE THE EASTERN FLANK OF
THE FRONT TO STRUGGLE AS IT TRIES TO COMPETE AGAINST THE WESTERN
EDGE OF THE RIDGE. MODELS SOUNDINGS DO ADVERTISE A FEW HUNDRED J/KG
OF ELEVATED CAPE WITH THE NARROW FGEN BAND BUT MIDLEVEL LAPSE RATES
CONTINUE TO STRUGGLE WHICH DO NOT HELP THUNDERSTORM POTENTIAL. SPC
ONLY HAS MI IN GENERAL THUNDER FOR THE DAY. SHOULD DRY OUT
CONSIDERABLE OVERNIGHT WITH DRY SLOT SURGING UP INTO THE AREA BUT
TEMPERATURES WILL STAY ELEVATED OVERNIGHT WITH THE GOOD SW
FLOW...EVEN WITH SKIES TRYING TO CLEAR OUT.

NEXT CHANCE AT PRECIP COMES TUESDAY AFTERNOON THROUGH THE OVERNIGHT
AS THE NEXT SHORTWAVE LIFTS THROUGH THE WESTERN GREAT LAKES FOLLOWED
CLOSELY BY THE OPEN UPPER LEVEL LOW ITSELF. THIS WILL LEAD TO A
LENGTH PERIOD OF CHANCE POPS COMING TUESDAY EVENING WITH THE
SHORTWAVE. THEN THE COOL POOL ASSOCIATED WITH THE UPPER LOW SLIDES
OVER THE AREA. THIS WILL IMPROVE MID LEVEL LAPSE RATES BUT BY THEN
THE DEEP MOISTURE AXIS WILL BE EXITING TO THE EAST. THE UPPER LEVEL
TROUGH TRIES TO REDEVELOP FOR THE END OF THE WEEK KEEPING MI IN
WEST/SW FLOW THROUGH THE PERIOD.

TEMPERATURES WILL HOLD IN THE UPPER 70S TO LOW 80S THROUGH THE
WEEK AS THE AIRMASS REMAINS FAIRLY CONSISTENT AHEAD OF THE UPPER
TROUGH.

MARINE...

NORTHERN EDGE OF AN AREA OF HIGH PRESSURE WILL HOLD OVER THE REGION
TODAY KEEPING FAIRLY LIGHT WINDS AND LOW WAVES THROUGH TONIGHT.
SOUTHWEST FLOW INCREASES ON MONDAY WITH GUSTS POSSIBLY APPROACHING
25 KNOTS IN THE AFTERNOON ACROSS THE NEARSHORE ZONES. WAVES SHOULD
NOT BE AN ISSUE AS FLOW WILL BE OFFSHORE BUT WINDS WILL NEED TO BE
WATCHED FOR POSSIBLE SMALL CRAFT ADVISORY CONDITIONS. THUNDERSTORMS
WILL BE POSSIBLE OVER NORTHERN LAKE HURON TONIGHT NIGHT THROUGH
MONDAY. THE BEST THUNDERSTORM CHANCES FOR AREAS FURTHER SOUTH WILL
BE MONDAY EVENING.

&&

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

$$

AVIATION.....CB
SHORT TERM...CB
LONG TERM....DRK
MARINE.......DRK


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


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