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000
FXUS63 KDTX 241102
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
702 AM EDT FRI MAY 24 2013


.AVIATION...

//DISCUSSION...

DEEP COLUMN TROUGHING AND COLD AIR ADVECTION HAS TEAMED TOGETHER TO
ALLOW A STRATUS BLANKET TO EXPAND SOUTHWARD INTO THE CENTRAL GREAT
LAKES. A STRAIGHT NORTHERLY WIND TRAJECTORY WILL MAINTAIN THE VERY
AGGRESSIVE MOVEMENT. THE SHALLOW SATURATION MAKES IT EXTREMELY
DIFFICULT FOR THE NWP TO CATCH UP WITH THE TRENDS...WITH THE CLOUD
FORECASTING DISTILLING DOWN TO A NOWCAST OF LATEST SATELLITE
IMAGERY. EXPECT A INCREASING DIABATIC HEATING TERM TO PROMOTE
MIXING AND A OVC TO BKN TREND BY LATE MORNING. REGIONAL RAOBS FROM
LAST EVENING RECORDED THE AMOUNT OF DRY AIR THAT IS NEARBY...SO ONCE
THE DRY AIR BEGINS TO EXERT AN INFLUENCE AT ANY ONE AREA EXPECT A
DECIDED MOVE TO CLEAR AND SUNNY SKIES. IN OTHER WORDS...THERE IS LOW
CONFIDENCE IN TIMING.

AT DTW...LINEAR INTERPOLATION OF EXISTING CLOUD DECK IS SET TO MOVE
INTO THE TERMINAL PRIOR TO THE START OF THE TAF PERIOD. LOW
CONFIDENCE EXISTS IN WHEN TO END THE MVFR CEILINGS...BUT A SAFE
ESTIMATE WILL BE LATE MORNING WITH AN INCREASE IN DAYTIME SURFACE
HEATING.

//DTW THRESHOLD THREATS...

* LOW CONFIDENCE THAT CEILING HEIGHTS OF LESS THAN 5000FT WILL
PLAGUE THE TERMINAL THROUGH THE MORNING HOURS.

&&

.PREV DISCUSSION...ISSUED 340 AM EDT FRI MAY 24 2013

SHORT TERM...TODAY AND TONIGHT

THE WEATHER UP FOR DISCUSSION IS THE PROSPECTS FOR OVERCAST SKIES
TODAY AS AN OPAQUE BLANKET OF 030-035 FT STRATUS IS AGGRESSIVELY
DIVING SOUTHWARD ACROSS LAKE HURON. TRAJECTORY OF CLOUD DECK IN
ADDITION TO THE ORIENTATION OF THE WESTERN EDGE ALIGNS WELL WITH THE
AXIS OF MAXIMUM 925-850MB COLD AIR ADVECTION AND THE DEPRESSION OF
THE LONGWAVE TROUGH AXIS. NWP DATA IS VIRTUALLY VOID OF CLOUD...A
RESULT OF INADEQUATE VERTICAL RESOLUTION WITHIN THE MODELS. WHILE
THE CLOUD IS COMPLETELY OPAQUE IT IS UNDOUBTEDLY A SHALLOW LAYER OF
MOISTURE THAT IS LIKELY TRAPPED WITHIN THE BASE OF THE INVERSION
AT/AROUND 900-890MB. RUC SOUNDINGS SHOW SATURATION AT THIS
ZONE...BUT THE SOUNDING STRUCTURE ITSELF DOES NOT INSPIRE MUCH
CONFIDENCE AS IT IS THE WRONG PROFILE. GIVEN THE TRUE NORTHERLY
TRAJECTORY...HAVE DECIDED TO INTRODUCE OVERCAST CONDITIONS FOR MUCH
OF THE CWA THROUGH THE MORNING HOURS. IT WILL BE DIFFICULT TO
PINPOINT ANY WEST EDGE OF THE CLOUDS GIVEN DEGREE OF DRY AIR
IMMEDIATELY TO THE WEST. PATTERN RECOGNITION SUGGESTS ENTRAINMENT AT
THE EDGE SHOULD AID DIURNAL MIXING TO FORCE STRATUS TO GO BROKEN BY
LATE MORNING...EVENTUALLY CLEARING OUT FOR THE AFTERNOON.

LOWERED MAX TEMPERATURES FOR MANY AREAS DUE TO THE CLOUD AND STEADY
COLD AIR ADVECTION. EXPECT TEMPERATURES TO EVENTUALLY REACH 60-61
DEGREES ACROSS THE SOUTH AND SAGINAW VALLEY VERY LATE IN THE DAY.
OTHERWISE TEMPERATURES ARE GOING TO STRUGGLE TO REACH THE LOWER 50S
IN THE THUMB.

FOR TONIGHT...THE COMPACT VORT OVER NORTHERN MANITOBA WILL GET
SQUEEZED WITH A ROGUE VORTICITY STREAMER OFF OF THE PACNW ANOMALY
MERGING OVER THE WESTERN GREAT LAKES. THIS WILL OCCUR DOWN THE FRONT
EDGE OF THE CENTRAL CONUS RIDGE...ALLOWING FOR A VERY HEALTHY
AGEOSTROPHIC RESPONSE AND STRIPE OF FRONTOGENESIS VERY LATE. ANY
SIGNIFICANT TEMPERATURE GRADIENT WILL RESIDE WELL WEST OF LOWER
MICHIGAN WHICH IS WHERE THE PRECIPITATION RESPONSE WILL OCCUR.
REGARDLESS...INCREASING CLOUDS LATE WILL ESTABLISH A FLOOR ON
MINIMUM TEMPERATURES TONIGHT.

LONG TERM...SATURDAY THROUGH THURSDAY

THE OVERALL PATTERN ACROSS NORTH AMERICA THIS WEEKEND WILL FEATURE A
QUASI OMEGA BLOCK. SHORT WAVE ENERGY NOW SHOWN ROTATING INTO NRN
MANITOBA IS FORECAST TO TRACK ACROSS THE ERN GREAT LAKES AND MID
ATLANTIC EARLY SATURDAY...LEADING TO DEEPENING OF AN UPPER LOW
ROTATING ACROSS NEW ENGLAND. LOWER MI WILL BE LOCATED BETWEEN THIS
SYSTEM AND AMPLIFYING MID LEVEL RIDGING ACROSS THE NRN PLAINS/UPPER
MS VALLEY. THIS WILL PLACE THE FORECAST AREA WITHIN A STRONGLY
CONFLUENT UPPER FLOW WITH PERSISTENT HIGH PRESSURE AT THE SURFACE.
THE RESIDENT AIRMASS ACROSS THE GREAT LAKES WILL BE COOL AND VERY
DRY. TEMPS ON SATURDAY SHOULD ONLY RISE TO THE LOW 60S OVER MUCH OF
THE FORECAST AREA WITH 850MB TEMPS HOVERING AROUND +2C. THE AIRMASS
WILL MODERATE DURING THE COURSE OF THE WEEKEND...WITH HIGHS EXPECTED
TO BE AROUND 70 BY MEMORIAL DAY. GIVEN THE DRY AIRMASS AND LIGHT
WINDS...NIGHTTIME LOWS WILL BE QUITE CHILLY THIS WEEKEND /30S AND
40S/.

A SEASONALLY STRONG 140+ KNOT UPPER JET IS FORECAST DIVE INTO THE
PACIFIC NORTHWEST EARLY NEXT WEEK...LEADING TO LONG WAVE TROUGH
AMPLIFICATION ACROSS THE WRN US AND A BUILDING SUBTROPICAL RIDGE
ACROSS THE SERN US. THIS WILL ALLOW THE MID LEVEL RIDGE TO BECOME
MORE PROGRESSIVE AND PASS EAST OF LOWER MI TOWARD MIDWEEK...ALLOWING
A SFC WARM FRONT TO LIFT ACROSS THE REGION FROM THE SOUTHWEST. THIS
WARM FRONT WILL ADVECT A WARM...MOIST AND UNSTABLE AIRMASS INTO THE
FORECAST AREA. THE GFS CONTINUES TO BRING THIS WARM FRONT THROUGH
FASTER THAN THE OTHER MODEL SOLUTIONS /SUGGESTING CONVECTION AS
EARLY AS MON NIGHT/. THE GFS HAS SOME OBVIOUS CONVECTIVE FEEDBACK
ISSUES DUE TO POTENTIAL MCS DEVELOPMENT OVER THE PLAINS. THE GFS IS
ALSO LESS AMPLIFIED WITH THE LONG WAVE TROUGH OVER THE WRN US. GIVEN
THE STRENGTH OF THE POLAR JET AND POTENTIAL PHASING WITH THE
SUBTROPICAL JET...THE MORE AMPLIFIED ECMWF REMAINS THE PREFERRED
SOLUTION. THIS SUGGESTS THE BETTER CHANCES FOR CONVECTION WILL HOLD
OFF UNTIL THE TUES NIGHT/WED TIME FRAME. DESPITE THIS UNCERTAINTY...
THE OVERALL TREND NEXT WEEK WILL BE FOR WARMER AND MORE HUMID
CONDITIONS WITH INCREASING CHANCES FOR THUNDERSTORMS.

MARINE...

UNSEASONABLE CONDITIONS ARE IN PLACE OVER THE CENTRAL GREAT LAKES
TODAY AS COLD AIR ADVECTION IS ONGOING WITHIN A DEEP TROUGH AXIS.
EFFICIENT NORTHERLY FLOW AND A LONG FETCH OVER THE WATERS WILL
SUSTAIN HIGH WAVE ACTIVITY FROM SAGINAW BAY DOWN TO PORT HURON.
RECENT WATER TEMPERATURE READINGS FROM THE BUOYS SUGGESTS THAT
CONDITIONS WILL BE SOLIDLY IN THE NEUTRAL REGIME OUT OVER THE OPEN
LAKE WHICH IS ATYPICAL FOR LATE MAY. IN FACT...CONDITIONS ARE
UNSTABLE FOR SAGINAW BAY WITH WATER TEMPERATURE READINGS SUGGESTING
LSTS ARE AT AROUND 13 TO 14 C VS AN 850MB TEMPERATURE THAT WILL BE
DIPPING DOWN TO -4C BY 12Z THIS MORNING. WILL EXPAND THE ADVISORY TO
INCLUDE INNER SAGINAW. CONDITIONS ARE MORE MARGINAL ON LAKE ST CLAIR
AND LAKE ERIE. WILL GIVE RESPECT TO PEAK OF THE COLD AIR ADVECTION
THAT WILL OCCUR THIS MORNING FOR THE SOUTHERN ZONES AND EXTEND THE
SMALL CRAFT FOR THEM AS WELL. THE STABLE SURFACE ANTICYCLONE WILL
BUILD INTO THE CENTRAL GREAT LAKES TONIGHT BRINGING A RETURN OF MUCH
MORE FAMILIAR STABLE SEASON MARINE WEATHER.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.

LAKE HURON...
     SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT
     HURON...UNTIL 8 PM FRIDAY.

     SMALL CRAFT ADVISORY...OUTER SAGINAW BAY...UNTIL 6 PM FRIDAY.

     SMALL CRAFT ADVISORY...INNER SAGINAW BAY...UNTIL 10 AM FRIDAY.

LAKE ST CLAIR...
     SMALL CRAFT ADVISORY...UNTIL 4 PM FRIDAY.

MI WATERS OF LAKE ERIE...
     SMALL CRAFT ADVISORY...UNTIL 4 PM FRIDAY.

&&

$$

AVIATION.....99
SHORT TERM...CB
LONG TERM....SC
MARINE.......CB


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