Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 060753
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
353 AM EDT WED MAY 6 2015

.SHORT TERM... TODAY AND TONIGHT

CONDITIONS TODAY WILL BE DICTATED BY A SLOW NORTHWARD PROGRESSION OF
THE FRONT THAT HAS BEEN STALLED OVER INDIANA AND OHIO SINCE
YESTERDAY. THE FRONT WILL WEAKEN AS IT MOVES NORTHWARD THROUGH LOWER
MICHIGAN DURING THE DAY BUT WILL REMAIN ABLE TO SUPPORT A LINGERING
CHANCE OF SHOWERS MAINLY DURING THE MORNING. A STRAY THUNDERSTORM
WILL ALSO BE POSSIBLE DURING THE AFTERNOON AND EVENING OVER INTERIOR
SECTIONS AS WARMER AND MORE HUMID AIR MOVES BACK INTO THE REGION.
GRADUALLY DIMINISHING LOW CLOUDS WILL ALLOW ENOUGH SURFACE HEATING
FOR MAX TEMPS TO MAKE IT INTO THE LOWER HALF OF THE 70S EXCEPT NEAR
SHORELINE AREAS THAT WILL BE SUBJECT TO LAKE BREEZE COOLING.

SATELLITE IMAGERY AND MODEL FIELDS INDICATE STEADY PROGRESSION OF
THE LARGER SCALE UPPER AIR FEATURES UNDERWAY DURING THE MORNING. THE
UPPER LEVEL RIDGE IS SHOWN MOVING NORTHWARD TOWARD LOWER MICHIGAN
TAKING THE PLACE OF THE UPPER JET AXIS THAT IS DEPARTING TOWARD THE
ATLANTIC COAST. THE RIDGE PROGRESSION WILL PULL THE FRONTAL ZONE
NORTHWARD AS A WARM FRONT THROUGH THE DAY WHICH WILL CONTINUE TO
SUPPORT A CHANCE OF SHOWERS DURING THE MORNING. A BAND OF SHOWERS
STRETCHING FROM CENTRAL WISCONSIN INTO WEST-CENTRAL LOWER AT PRESS
TIME IS EVIDENCE THAT THE STRUCTURE OF THE FRONT WILL BE MAINTAINED
INITIALLY...ESPECIALLY IN THE 850-700 MB LAYER...BUT THE
CONSIDERABLY WEAKER WIND FIELD WITHIN THE UPPER RIDGE AXIS WILL
RESULT IN WEAKER FRONTAL FORCING AND EVENTUALLY FRONTOLYSIS AS THE
DAY PROGRESSES. THE FRONTAL ZONE WILL BE MOVING NORTHWARD BUT THE
WIND WILL BE SO WEAK THAT FEATURE RELATIVE THETA-E ADVECTION AND
AGEOSTROPHIC CIRCULATION WILL STRUGGLE TO BE MAINTAINED IN SUPPORT
SHOWERS...ESPECIALLY ONCE NOCTURNAL ELEVATED INSTABILITY BEGINS TO
WANE BY AFTERNOON. PLAN TO MONITOR EARLY MORNING RADAR TRENDS FOR
INCREASING COVERAGE IN THE TRI CITIES REGION BEFORE SUNRISE.
OTHERWISE...MID RANGE CHANCE POPS DURING THE MORNING AND DECREASING
DURING THE AFTERNOON ARE EXPECTED TO COVER THE SHOWER POTENTIAL
WITHIN THE ELEVATED PORTION OF THE FRONTAL ZONE.

STEADY EROSION OF THE LOW CLOUDS THROUGH THE DAY WILL BE A SIGN OF
THE WEAKENING SURFACE WARM FRONT WHICH WILL EVENTUALLY WASH OUT
DURING THE AFTERNOON IN FAVOR OF WARMER AND MORE HUMID AIR. MODEL
DEPICTIONS OF LOW LEVEL CONVERGENCE IN THE LEE OF LAKE MICHIGAN SEEM
REASONABLE IN TOUCHING OFF MID TO LATE AFTERNOON CONVECTION ON THE
UPSTREAM SIDE OF THE UPPER RIDGE AXIS. SOME OF THIS ACTIVITY COULD
DRIFT INTO OUR AREA GENERALLY WEST OF THE U.S. 23 CORRIDOR AND LAST
THROUGH ABOUT MID EVENING BEFORE DIMINISHING WITH THE LOSS OF
DAYTIME HEATING. A GENERAL CLEARING TREND WILL THEN CONTINUE THROUGH
THE OVERNIGHT HOURS OVER WEAK GRADIENT FLOW AT THE SURFACE. THIS
WILL SET UP A FAVORABLE FOG SCENARIO AS TEMPERATURES DROP BACK INTO
THE UPPER 40S TO LOWER 50S LATE TONIGHT THROUGH SUNRISE THURSDAY.

&&

.LONG TERM...THURSDAY THROUGH TUESDAY

WARM FRONTAL STRUCTURE EXITS TO THE NORTHEAST AS UPPER RIDGING PULLS
EAST EARLY THURSDAY...THE ENSUING INCREASE IN DEPTH OF SOUTHWEST
FLOW FIRMLY SHIFTING SE MICHIGAN INTO THE WARM SECTOR FOR THE END OF
THE WORK WEEK.  A WELL MIXED PROFILE CARRYING 850 MB TEMPERATURES
APPROACHING 20C COMBINED WITH A HIGH DEGREE OF INSOLATION WILL
TRANSLATE INTO HIGHS AT OR JUST ABOVE THE 80 DEGREE MARK BOTH
THURSDAY AND FRIDAY.   THIS AIR MASS CHARACTERIZED EARLY ON BY
DEWPOINTS IN THE LOWER AND MIDDLE 50S...INSUFFICIENT TO SUPPORT A
CONVECTIVE OPPORTUNITY ON THURSDAY ABSENT OF ANY FORCING.  IMPROVING
LOW LEVEL MOISTURE QUALITY INTO FRIDAY...DEWPOINTS NUDGING CLOSER TO
THE 60 DEGREE MARK ACCOMPANIED BY A MORE NOTABLE INCREASE IN MID
LEVEL THETA-E BY MID-LATE AFTERNOON.  THIS PROCESS MAY BE AUGMENTED
BY THE EAST/NORTHEAST TRANSLATION OF SOME FORM OF PRE-FRONTAL TROUGH
AND/OR SHORTWAVE ENERGY FUNNELING WELL DOWNSTREAM OF AN INBOUND COLD
FRONT.  00Z MODEL GUIDANCE HINTING AT SOME POSSIBLE CONVECTIVE
DEVELOPMENT ALONG THESE FEATURES ACROSS WESTERN LOWER MI BY LATE
MORNING/MIDDAY...EVENTUALLY MIGRATING INTO PORTIONS OF CENTRAL MI BY
PEAK HEATING.   SOME SEMBLANCE OF ORGANIZED ASCENT INTO AN
INCREASINGLY SUPPORTIVE THERMODYNAMIC PROFILE WOULD THEN PROVIDE AT
LEAST A CHANCE FOR CONVECTION TO DEVELOP AND EXPAND INTO A PORTION
OF THE REGION /FAVOR NORTHWEST SECTIONS/ FROM MID AFTERNOON INTO THE
EVENING HOURS.

STEADY INFLUX OF SHORTWAVE ENERGY WORKING THROUGH THE MEAN SW FLOW
WILL EASE THE AFOREMENTIONED COLD FRONT INTO SE MICHIGAN SOMETIME
WITHIN THE FRIDAY NIGHT AND SATURDAY WINDOW.  POTENTIAL FOR A WEAK
WAVE TO DEVELOP ALONG THIS FRONTAL BOUNDARY WITH THE PASSAGE A
SLIGHTLY STRONGER HEIGHT FALL CENTER...A SCENARIO WHICH WOULD
ENHANCE THE ODDS FOR A MORE SIZABLE ROUND OF CONVECTION TO EXPAND
ACROSS PORTIONS OF THE GREAT LAKES DURING THIS TIME.  MODELS
PROVIDING A VARYING DEGREE OF CONFIDENCE ON THIS EVOLUTION...THE GFS
STILL MORE PROGRESSIVE RELATIVE TO THE ECMWF/CANADIAN COMBO IN
TRANSLATING THE FRONTAL STRUCTURE AND CORRESPONDING MOISTURE
COMPONENT THROUGH LOWER MICHIGAN ON SATURDAY.  THIS MUDDLES THE
FORECAST MOVING FORWARD THROUGH THE LATTER HALF OF THE
WEEKEND...WITH THE ECMWF/CANADIAN SOLUTION SPACE STILL FAVORING A
STALLED AND MORE ACTIVE FRONTAL BOUNDARY HOLDING IN THE VICINITY OF
SE MICHIGAN THROUGH THE DURATION OF THE WEEKEND. A POTENTIALLY
ACTIVE PERIOD...KEYING ON THE EVENTUAL PLACEMENT OF THIS BOUNDARY.
THE ADDED MOISTURE/CLOUD DEBRIS WILL EASE TEMPERATURES DOWN FROM
THE 10+ DEGREE ABOVE NORMAL WARMTH NOTED FOR THU/FRI...BUT STILL
LOOKING AT ABOVE NORMAL READINGS THROUGH THE WEEKEND.

&&

.MARINE...

HIGH PRESSURE LIFTING ACROSS THE CENTRAL GREAT LAKES WILL MAINTAIN
LIGHT WINDS TODAY.  MODEST SOUTHERLY WINDS WILL DEVELOP BEHIND THIS
HIGH ON THURSDAY.  SOUTH TO SOUTHWEST WINDS WILL INCREASE ON FRIDAY
IN ADVANCE OF A COLD FRONT.  THIS WILL BE ACCOMPANIED BY AN INCREASE
IN MOISTURE...BRINGING A CHANCE FOR THUNDERSTORMS BY LATE FRIDAY
INTO FRIDAY NIGHT.  RISK FOR THUNDERSTORMS WILL CONTINUE THROUGH AT
LEAST THE FIRST HALF OF THE WEEKEND.  IN ADDITION...THE POTENTIAL
WILL EXIST FOR MARINE FOG TO DEVELOP AS WARM/MOIST AIR MOVES ACROSS
THE COLDER LAKE WATERS.

&&

.AVIATION...ISSUED 1149 PM EDT TUE MAY 5 2015

WIDESPREAD IFR AND LOW MVFR REMAIN FIRMLY IN PLACE FROM KPTK SOUTH
WITHIN LOW-LEVEL MOISTURE AXIS NORTH OF THE SURFACE WARM FRONT.
SHOWERS TRAINING WITHIN THIS CORRIDOR WILL COME TO AN END IN THE
DETROIT AREA BETWEEN APPROXIMATELY 07Z AND 08Z. NOCTURNAL LOWERING
OF CIGS AND REMNANT MOISTURE FROM THIS EVENING`S SHOWERS WILL
CONTRIBUTE TO PERSISTENCE OF IFR AND PERHAPS SOME DETERIORATION TO
LIFR CEILING OVERNIGHT ALONG WITH VSBY RESTRICTION. MOISTURE AXIS
WILL LIFT NORTH OVERNIGHT EVENTUALLY BRINGING IFR TO FNT AND LOW
MVFR TO HIGH IFR TO KMBS DURING THE PREDAWN HOURS. WINDS WILL REMAIN
LIGHT AND EASTERLY. CIGS ARE EXPECTED TO MIX BACK UP TO MVFR
MID/LATE MORNING WEDNESDAY.


//DTW THRESHOLD PROBABILITIES...

* HIGH FOR CIG AOB 5KFT

* LOW FOR CIGS AOB 200 FT.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.

&&

$$

SHORT TERM...BT
LONG TERM....MR
MARINE.......MR
AVIATION.....JVC


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



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