National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

-- Discussion containing changed information from previous version are highlighted. --
000
FXUS63 KDTX 131952
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
352 PM EDT MON MAY 13 2013

.SHORT TERM... 
-- Changed Discussion --
THIS EVENING THROUGH TONIGHT

UPPER LEVEL PATTERN CONTINUING THE PROGRESSIVE TREND THROUGH THE
SHORT TERM. THE BACKSIDE OF THE DEEP UPPER TROUGH WILL FINALLY EXIT
THE GREAT LAKES AS UPPER RIDGING BUILDS IN FROM THE WEST. THE SFC
RIDGE AXIS WILL SLIDE THROUGH EARLY TONIGHT BACKING WINDS FROM
WESTERLY TO SOUTHERLY. DIURNAL CU FIELD WILL QUICKLY DISSIPATE THIS
EVENING AS DAYTIME HEATING CEASES. THE CLEARING SKIES WITH LIGHT
FLOW UNDER THE RIDGE AXIS AND VERY DRY BOUNDARY LAYER WILL PRESENT
FAVORABLE CONDITIONS FOR RADIATIONAL COOLING FOR A FEW TONIGHT
BEFORE CIRRUS DEBRIS STREAMS INTO SE MI. THE CIRRUS WILL GRADUALLY
LOWER THROUGH THE NIGHT AS AN AREA OF ISENTROPICALLY FORCED SHOWERS
TRACKS THROUGH LOWER MI TOWARD MORNING. BETTER CHANCES FOR SHOWERS
WILL BE UP AROUND FNT AND MBS WITH LITTLE TO NO CHANCE SOUTH OF PTK.
THE COMBINATION OF INCREASING CLOUDS AND SOUTHERLY FLOW...WHICH WILL
INCREASE SFC MOISTURE AND WAA...WILL PREVENT TEMPS FROM DROPPING
MUCH BELOW 40F. THE EXCEPTION MAY BE IN THE THUMB REGION WHICH
STRUGGLED TO EVEN HIT 50 TODAY THUS WILL LIKELY DROP INTO THE
MID/UPPER 30S BEFORE THE MODERATING TREND TAKES OVER. WILL HOLD ONTO
THE PATCHY FROST MENTION FOR A FEW HOURS OVERNIGHT. OVERALL IT WILL
BE A BIT WARMER THEN LAST NIGHT WITH THE POSSIBILITY OF A FEW LIGHT
SHOWERS BY MORNING.
-- End Changed Discussion --

&&

.LONG TERM... 
-- Changed Discussion --
TUESDAY THROUGH NEXT MONDAY

SHOWERS ARE LIKELY OVER SE MICHIGAN DURING TUESDAY MORNING AS A WARM
FRONT TAKES SHAPE OVER THE MIDWEST. THE MID LEVELS OF THIS FEATURE
WILL EXTEND UP AND OVER LOWER MICHIGAN WITH THE ASSOCIATED MOIST
ISENTROPIC ASCENT LEADING TO ELEVATED INSTABILITY AND SHOWER
FORMATION. INCOMING 12Z MODELS MOISTENED UP NOTICEABLY COMPARED TO
THE 00Z RUN AND BETTER REFLECT THE BANDS OF SHOWERS OVER MINNESOTA.
ACTIVITY THERE WAS UNDER FORECAST IN EARLIER MODEL RUNS WHICH IS A
USUAL BIAS IN NOCTURNAL MOISTURE TRANSPORT SCENARIOS. SO, JUST IN
THAT SENSE, THE INCREASING MOISTURE TREND OVER LOWER MICHIGAN IN THE
12Z SOLUTIONS LOOKS SOLID, BUT GOVERNING ASPECTS OF THE PATTERN ALSO
LOOK INCREASINGLY FAVORABLE. THE DEPARTURE OF THE FULL LATITUDE
UPPER TROUGH ALONG THE ATLANTIC COAST WILL LEAD TO LARGE SCALE
HEIGHT RISES OVER THE GREAT LAKES AS THE LONG WAVE PATTERN BECOMES
MORE ZONAL OVER NORTH AMERICA. DEEP SOUTHWEST RETURN FLOW IN THE LOW
LEVELS WILL POWER THE HEIGHT RISES DUE TO WARM ADVECTION AND DRIVE
THE MOISTURE TRANSPORT OVER LOWER MICHIGAN WITH SOME ENHANCEMENT BY
THE SHORT WAVE MOVING THROUGH CENTRAL CANADA. THE RESULT WILL BE A
SHARP MID LEVEL FRONTAL ZONE AS INDICATED BY THE GRADIENT IN THETA-E
IN THE 850-700 MB LAYER. MODEL CROSS SECTIONS ALSO SHOW A DEEP LAYER
OF INSTABILITY ABOVE THE FRONTAL ZONE FEEDING 850 MB DEWPOINT NEAR
10C INTO THE SOUTH FLANK OF THE BROAD UPPER LEVEL JET AXIS OVER THE
NORTHERN GREAT LAKES. THE RESULTING ENHANCEMENT OF THE WARM FRONTAL
CIRCULATION BY THE NOCTURNAL INCREASE IN THE LOW LEVEL JET,
ASSOCIATED INCREASE OF INSTABILITY, AND SYSTEM RELATIVE ISENTROPIC
ASCENT WILL FEED THE PATTERN OF SHOWERS BUT COME UP SHORT ON
INGREDIENTS FOR ELEVATED THUNDERSTORM ACTIVITY.

THE MORNING PATTERN OF SHOWERS WILL DEVELOP OFF TO THE EAST BY EARLY
AFTERNOON AS THE SURFACE WARM FRONT APPROACHES THE SOUTHERN MICHIGAN
BORDER. MODEL SOLUTIONS THEN INDICATE THE NEXT SHORT WAVE REACHING
THE UPPER MIDWEST DURING THE AFTERNOON BUT THE SURFACE LOW STRENGTH
AND POSITION OVER NORTHWEST WISCONSIN REMAINS LESS THAN CONVINCING
ON THE ABILITY TO DRAW THE WARM FRONT THROUGH SE MICHIGAN. THIS TIME
OF YEAR, ANY SE WIND COMPONENT BELOW 850 MB WILL STRONGLY OPPOSE THE
NORTHWARD MIGRATION OF THE FRONT UNTIL LATER TUESDAY NIGHT AS THE
SURFACE LOW/TRIPLE POINT MOVES THROUGH NORTHERN LOWER MICHIGAN. FOR
NOW, PLAN TO SHARPEN THE GRADIENT OF MAX TEMPS ACROSS THE AREA AS
THE THUMB REGION WILL STRUGGLE IN THE 50S WHILE INTERIOR SECTIONS
NEAR THE OHIO BORDER WILL PUSH 70. THE AREA WILL THEN BREAK INTO THE
WARM SECTOR WITH STEADY OR RISING TEMPERATURES TUESDAY NIGHT JUST AS
ANOTHER SURGE OF NOCTURNAL MOISTURE TRANSPORT ATTEMPTS A REPEAT
PERFORMANCE OF SHOWERS INTO WEDNESDAY MORNING, ONLY THIS TIME WITH
ENTRY LEVEL THUNDERSTORM POTENTIAL ADDED TO THE MIX.

THE MAIN CONCERN DURING THE SECOND HALF OF THE WEEK WILL BE WITH THE
WEAK COLD FRONT TRAILING OVER THE REGION WEDNESDAY AFTERNOON THROUGH
THURSDAY. THIS BOUNDARY LOOKS SHALLOW IN MODEL CROSS SECTIONS AND
SUBJECT TO MIXING DURING PEAK SURFACE HEATING, BUT THERE IS GOOD
AGREEMENT ON SUBSTANTIAL COLD ADVECTION TAKING PLACE WEDNESDAY
AFTERNOON JUDGING FROM LOW LEVEL TEMPERATURE AND THICKNESS FIELDS.
ADD TO THAT THE UNCERTAINTY OF CLOUD COVER LEFT OVER FROM ANY
MORNING SHOWERS FOR ENOUGH EVIDENCE TO STICK WITH OUR GOING MAX
TEMP GRID FOR WEDNESDAY AFTERNOON, WHICH LOOKS BETTER THAN ANY OF
THE LATEST GUIDANCE OPTIONS AND OFFERS AT LEAST LOWER 80S NEAR THE
OHIO BORDER. IT SEEMS MORE LIKELY THAT A SECONDARY/BACKDOOR COLD
FRONT WILL BE WHAT IT TAKES FOR A CONVINCING FRONTAL PASSAGE
WEDNESDAY NIGHT INTO THURSDAY. THE INCOMING 12Z ECMWF INDICATES
THIS WILL DRIVE THE BAROCLINIC ZONE INTO THE OHIO VALLEY WITH HIGH
PRESSURE SETTLING OVER LOWER MICHIGAN FRIDAY.

HEADING INTO THE WEEKEND, THE GLOBAL MODELS DEPICT THE RETURN OF AN
ACTIVE PRECIPITATION PATTERN OVER THE GREAT LAKES. THIS WILL BE DUE
TO A TRANSITION TOWARD GREATER AMPLIFICATION IN THE LARGE SCALE
UPPER LEVEL FLOW. LOW PRESSURE DEVELOPING OVER THE NORTHERN PLAINS
WILL CONNECT WITH THE OHIO VALLEY FRONT AND FORM A BREEDING GROUND
FOR CLUSTERS OF SHOWERS AND STORMS BUT WITH TEMPERATURES AT OR ABOVE
NORMAL THROUGH THE PERIOD.
-- End Changed Discussion --

&&

.MARINE...

-- Changed Discussion --
HIGH PRESSURE WILL CONTINUE SLIDING THROUGH THE REGION OVERNIGHT
PROVIDE GENERALLY FAVORABLE MARINE CONDITIONS. A STABLE 10 TO 15
KNOT SOUTHEASTERLY FLOW WILL DEVELOP ON TUESDAY IN ADVANCE OF A WARM
FRONT. INCREASING STABILITY WILL KEEP WIND GUSTS AND WAVE HEIGHTS ON
THE LOW SIDE. THE PASSAGE OF THE WARM FRONT WILL BRING A CHANCE OF
THUNDERSTORMS TUESDAY NIGHT. A COLD FRONTAL PASSAGE ON WEDNESDAY
WILL SHIFT WINDS TO WESTERLY AND POSSIBLE BRING ANOTHER ROUND OR
THUNDERSTORMS.
-- End Changed Discussion --

&&

.AVIATION...
-- Changed Discussion --
ISSUED 121 PM EDT MON MAY 13 2013

//DISCUSSION...

VFR CONDITIONS ARE EXPECTED TO PERSIST THROUGH THE TAF PERIOD AS
HIGH PRESSURE HOLDS OVER LOWER MI. 5KFT DIURNAL CU FIELD WILL ERODE
THIS EVENING WITH THE LOSS OF HEATING. AN APPROACHING WARM FRONT
WILL BRING THICKENING HIGH CLOUDS OVERNIGHT...GRADUALLY LOWERING
TOWARD MORNING. THE FRONT WILL BRING SOME LIGHT SHOWERS TUESDAY
MORNING BUT DRY SURFACE LAYER WILL KEEP CIGS VFR WITH LIKELY LITTLE
TO NO VSBY RESTRICTIONS. WESTERLY WIND GUSTS WILL SUBSIDE THIS
EVENING BEFORE BACKING TO THE SOUTH AND INCREASING LATE TUESDAY
MORNING AGAIN.

//DTW THRESHOLD THREATS...

* NONE.
-- End Changed Discussion --

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...DRK
LONG TERM....BT
MARINE.......DRK
AVIATION.....DRK


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