Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 100717
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
317 AM EDT THU APR 10 2014

.SHORT TERM...TODAY AND TONIGHT

A SURFACE COLD FRONT EXTENDING FROM WESTERN LAKE SUPERIOR INTO THE
CENTRAL PLAINS AS OF 07Z WILL MOVE ACROSS SE MI THIS AFTERNOON. THE
FRONT IS TRAILING A DEEP SFC LOW TRACKING ACROSS NRN ONTARIO
ASSOCIATED WITH A MID LEVEL WAVE NOW ROTATING INTO NW ONTARIO.
UPSTREAM RADAR IMAGERY SHOWS SOME POST SFC FRONTAL SHOWERS WITHIN
THE LOW-MID TROPOSPHERIC PORTIONS OF THE FRONT. THESE FRONTAL
DYNAMICS WILL ENTER THE SAGINAW VALLEY AND THUMB REGION EARLY THIS
AFTERNOON. DRY AIR IN THE LOW LEVELS AND A SHALLOW STABLE LAYER IN
THE MID LEVELS WILL BE LIMITING FACTORS FOR WIDESPREAD SHOWERS AS
THE FRONTAL BOUNDARY ADVANCES INTO THE FORECAST AREA. MODEL CROSS
SECTIONS DUE HOWEVER SHOW THE FRONTAL CIRCULATION DEEPENING OVER SE
MI LATE IN THE AFTERNOON WITHIN THE ENTRANCE REGION OF A
STRENGTHENING UPPER JET STREAK. A MID LEVEL SHORT WAVE IS ALSO
FORECAST TO TRAVERSE SRN MI THIS AFTERNOON. THESE FACTORS AND
CONSIDERING WEAK BUT PERSISTENT LOW-MID LEVEL MOISTURE ADVECTION
ALONG THE FRONT SUGGESTS THAT SHOWERS WILL INCREASE IN COVERAGE AS
THE MID LEVEL FRONTAL CIRCULATION SLIDES FROM FLINT TO TOLEDO IN THE
21Z TO 02Z TIME FRAME. MUCH DRIER AIR WILL THEN RAPIDLY FILTER IN
FROM THE NORTH TONIGHT IN THE WAKE OF THIS FRONTAL SYSTEM.

AREA VAD WIND PROFILES SHOW LOW LEVEL WINDS ATOP THE SHALLOW
NOCTURNAL STABLE LAYER OF 40-55 KNOTS. THIS FLOW IS ADVECTING A VERY
MILD PRE FRONTAL AIRMASS INTO SRN MI. OVER THE LAST COUPLE
HOURS...TEMPS OVER MUCH OF SE MI HAVE RISEN INTO THE UPPER 40S AND
LOW 50S. THE ONSET OF DAYTIME HEATING AND STRENGTH OF THE SW FLOW
WILL OPTIMIZE MIXING AND LEAD TO VERY MILD TEMPS IN ADVANCE OF THE
FRONT. RECENT SATELLITE IMAGERY IS SUGGESTIVE OF SOME EARLY DAY SUN.
TAKING INTO CONSIDERATION THE 00Z NAM12 AND RUC SOUNDINGS ALONG WITH
YESTERDAY MAX TEMPS UPSTREAM...A GOOD PORTION OF SE MI MAY BE ABLE
TO ACHIEVE HIGH TEMPS AROUND 70 TODAY. SLIGHTLY COOLER CONDITIONS
ARE EXPECTED ACROSS THE TRI CITIES AND THUMB DUE TO THE EARLIER
FROPA. THE ONSET OF MIXING WILL LEAD TO RATHER GUSTY SW WINDS TODAY.
THE MIXING WILL NOT ALLOW THE 40-50 KNOT WINDS NOW RESIDING ABOVE
THE STABLE LAYER TO BE REALIZED AT THE SFC. SOME GUSTS OVER 30 MPH
BY LATE MORNING/EARLY AFTERNOON DO HOWEVER SEEM PLAUSIBLE AS THE
BOUNDARY LAYER GROWS.

&&

.LONG TERM...

THE STRONG CENTRAL PACIFIC JET ALIGNED ALONG THE 35TH PARALLEL IS
POISED TO SET IN MOTION A DOWNSTREAM RIPPLE EFFECT THAT WILL BE THE
DOMINATING PLAYER IN THE SENSIBLE WX FOR THE NEXT SEVERAL DAYS.
THERMAL FIELD WILL UNDERGO SUBTLE MODIFICATION IN THE WAKE OF
TODAY`S DEPARTING TROUGH AXIS ON FRIDAY WHILE THE BEGINNINGS OF A
LONGWAVE TROUGH TAKING SHAPE OVER THE WESTERN UNITED STATES WILL
KEEP LARGE SCALE FLOW ACROSS THE CENTRAL UNITED STATES ORIENTED IN A
QUASI-ZONAL/WSW FASHION. THIS WILL ENSURE ONGOING WARM ADVECTION
THROUGH THE WEEKEND. THIS WILL SPELL H85 TEMPERATURES REACHING +4C
BY DAY`S END FRIDAY, 8-10C BY LATE SATURDAY AND POTENTIALLY HIGHER
ON SUNDAY DEPENDING ON HOW QUICKLY THE LARGE SCALE TROUGH AXIS
PROGRESSES EASTWARD. HIGHS ON FRIDAY AND SATURDAY WILL THEREFORE BE
MODULATED BY CLOUD COVER AND MIXING DEPTHS.

FORECAST SOUNDINGS FOR FRIDAY INDICATE DEEP MIXING TO AROUND 800MB
WHICH SHOULD EASILY ALLOW EVERYONE TO TOP 60 DEGREES. A PASSING
SHORTWAVE WILL BRING SOME MID/HIGH CLOUDS ACROSS NORTHERN AREAS AND
WILL MOST LIKELY HELP ENHANCE DIURNAL CU COVERAGE AS WELL,
PARTICULARLY ACROSS THE NORTHERN HALF OF THE AREA. SEE NO ISSUES
WITH FORECAST HIGHS OF 62-65. A PASSING SHOWER IS NOT OUT OF THE
QUESTION LATE FRIDAY OR FRIDAY NIGHT IN ASSOCIATION WITH THE
AFOREMENTIONED WAVE, WITH THE BEST CHANCE BEING NORTH OF I-69, BUT
THE BETTER MOISTURE AND FORCING IS STILL FORECAST TO REMAINED
CONFINED WELL NORTH OF THE AREA. LIGHT WARM ADVECTION WILL KEEP
OVERNIGHT LOWS JUST SLIGHTLY ABOVE CLIMATOLOGICAL NORMALS ON FRIDAY
NIGHT...LOW 40S.

CONTINUED WARM ADVECTION WILL WARM THE COLUMN CONSIDERABLY ON
SATURDAY WHILE LOW-LEVEL FLOW RESPONDS TO THE AMPLIFYING PATTERN BY
BACKING TO A MORE SOUTHEASTERLY DIRECTION. DESPITE THE UNFAVORABLE
FETCH ACROSS LAKE ERIE, DEEP MIXING SHOULD BE THE PRIMARY
CONTRIBUTOR TO MAX TEMPS AT MOST LOCATIONS. ENVISION A SCENARIO IN
WHICH MOST LOCATIONS APPROACH OR EXCEED 70 DEGREES WHILE LAKE
SHADOWED SPOTS ARE ABOUT 10 DEGREES COOLER.

ONGOING WAVE AMPLIFICATION WILL ALLOW A JET STREAK TO ORGANIZE OVER
THE NORTHERN GREAT LAKES LATE SATURDAY WITH RIGHT ENTRANCE FORCING
PROGGED TO INTENSIFY BUT REMAIN RELATIVELY STATIONARY. THIS WILL
FACILITATE ONGOING ORGANIZATION OF A LOW-LEVEL BAROCLINIC ZONE WHICH
WILL SERVE AS THE FOCUS FOR SEVERAL ROUNDS OF SHOWERS BEGINNING WITH
AN INITIAL WAVE OF ISENTROPIC ASCENT ON SATURDAY EVENING AND
CONTINUING THROUGH SUNDAY. ACTUAL POSITIONING OF THE BAROCLINIC ZONE
WILL BE KEY AND REMAINS A POINT OF UNCERTAINTY AT THIS TIME, BUT
TAKEN AT FACE VALUE THERE IS A GENERAL CONSENSUS AMONG THE GUIDANCE
THAT THE HIGHEST PROBABILITY FOR APPRECIABLE RAINFALL THROUGH THE
WEEKEND WILL BE ACROSS THE NORTHWESTERN HALF OF THE CWA.

&&

.MARINE...

FRESH SOUTHWEST FLOW WILL DEVELOP THIS MORNING IN ASSOCIATION WITH A
STRENGTHENING LOW PRESSURE SYSTEM OVER CANADA. AN OCCASIONAL GUST TO
NEAR GALES IS NOT OUT OF THE QUESTION BUT WARM STABLE FLOW WILL
TEMPER EXPECTATIONS FOR WIND GUSTS. WINDS AND WAVES WILL SUBSIDE
TONIGHT AND REMAIN LIGHT THROUGH THE FIRST HALF OF THE WEEKEND.
MODERATE SOUTHERLY FLOW WILL DEVELOP BY SUNDAY WITH GUSTY NORTHERLY
WINDS TAKING SHAPE BY EARLY NEXT WEEK.

&&

.AVIATION...ISSUED 1157 PM EDT WED APR 9 2014

//DISCUSSION...

VFR CONDITIONS WILL PERSIST WITH SCT TO OCCASIONAL BKN DECK ABOVE
10KFT. THESE CONDITIONS WILL PERSIST THROUGH THURSDAY MORNING BEFORE
CLOUDS THICKEN/LOWER AS SHOWERS DEVELOP IN ADVANCE OF APPROACHING
COLD FRONT. THIS SHOWER ACTIVITY WILL BRING MVFR CIGS FOR SEVERAL
HOURS DURING FROPA...WHICH 00Z NAM12 RUN HAS DELAYED A FEW HOURS.
CLEARING IS THEN EXPECTED INTO THE EVENING. SOUTHWEST WINDS WILL
BECOME RATHER GUSTY...25+ KNOTS...AS PRESSURE GRADIENT TIGHTENS
DURING THE DAY. SO...LLWS TONIGHT WILL END AS THE BOUNDARY LAYER
MIXED OUT BY 13Z-15Z.

FOR DTW...WIND SHEAR WILL DEVELOP OVERNIGHT AND PERSIST INTO MORNING
BEFORE THE BOUNDARY LAYER MIXES OUT AND GUSTY SOUTHWEST WINDS (25-3O
KNOTS) REACH THE SURFACE. THIS WILL BE ESPECIALLY TRUE BY AFTERNOON
AS COLD FRONT/SHOWERS ENCROACH ON THE AREA.

//DTW THRESHOLD THREATS...

* MEDIUM CONFIDENCE IN CEILINGS AOB 5000 FEET THURSDAY AFTERNOON.

&&

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

&&

$$

SHORT TERM...SC
LONG TERM....JVC
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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