Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 311103
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
703 AM EDT SUN AUG 31 2014

.AVIATION...

//DISCUSSION...

SURFACE ANALYSIS INDICATES ENOUGH LOW LEVEL MOISTURE AROUND TO
CARRY IFR/MVFR CEILINGS DURING THE MORNING WITH A LOW CHANCE OF
SHOWERS OR EMBEDDED THUNDERSTORM DEVELOPING ACROSS SOUTHERN TAF
SITES DURING THE AFTERNOON. HOWEVER...MID LEVEL DRY AIR WILL
BECOME BETTER ESTABLISHED THROUGH THE DAY...ENDING THE CHANCE...AS
WELL AS SCATTERING OUT THE CLOUDS. A SURFACE RIDGE AND MOSTLY
CLEAR/PARTLY CLOUDY SKIES TONIGHT WILL SET THE STAGE FOG
DEVELOPMENT...BUT WENT WITH A CONSERVATIVE MVFR VSBY REDUCTION FOR
NOW.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CEILING AOB 5000 FEET THIS MORNING.

* LOW CONFIDENCE IN THUNDERSTORMS THROUGH MID AFTERNOON.

&&

.PREV DISCUSSION...ISSUED 351 AM EDT SUN AUG 31 2014

SHORT TERM...TODAY AND TONIGHT

MID LEVEL CIRCULATION EXITING WISCONSIN THIS MORNING...TRACKING
THROUGH FAR NORTHERN LOWER MICHIGAN. THE ISSUE IS WE DO NOT GET INTO
UPPER LEVEL RIDGING UNTIL TOWARD 00Z MONDAY...AND WEAK SURFACE COLD
FRONT IS STILL DRAPED ACROSS THE AREA. WITH LINGERING LOW LEVEL
MOISTURE (SURFACE DEW PTS STILL IN THE UPPER 60S)...THERE WILL BE AN
OPPORTUNITY FOR SHOWERS AND THUNDERSTORMS TO GO UP ACROSS THE SOUTH
HALF OF THE CWA...WITH DAYTIME/SURFACE BASED INSTABILITY LIKELY
ALLOWING CAPES TO CLIMB INTO THE 1500-2000 J/KG RANGE.
FORTUNATELY...BULK WIND SHEAR WILL BE WEAK AND SEVERE WEATHER IS NOT
ANTICIPATED. ALSO...PRONOUNCED MID LEVEL DRY SLOT WILL BE TAKING
HOLD THROUGH THE DAY...WITH BOUNDARY LAYER DEPTHS EVENTUALLY
INCREASING ENOUGH TO ENTRAIN THE DRY AIR AND END SHOWER/THUNDERSTORM
THREAT LATE IN THE DAY. EVEN SO...COVERAGE/POTENTIAL OF
SHOWERS/THUNDERSTORMS LOOKS TO BE LOW/CHANCE. WITH THE WARM START TO
THE DAY (AROUND 70 DEGREES) AND DEVELOPING SUNSHINE...MAXES SHOULD
HAVE NO PROBLEM CLIMBING INTO THE LOW TO MID 80S WITH 850 MB TEMPS
AROUND 15 C.

SHORTWAVE RIDGING AT THE SURFACE AND ALOFT TONIGHT WILL SUPPORT DRY
FORECAST...BUT THERE DOES LOOK TO BE POTENTIAL FOR SOME FOG BASED ON
NAM SURFACE CONDENSATION PRESSURE DEFICITS...AS MINS MATCH THE DEW
PTS...LOW TO MID 60S.

LONG TERM... MONDAY THROUGH NEXT SATURDAY

MODEL ANALYSIS FIELDS DEPICT AN IMPRESSIVE 120 KT JET AT 250 MB
SPANNING MUCH OF THE NORTH PACIFIC AND GULF OF ALASKA WHICH WILL DIG
INTO AND HELP DEEPEN A BROAD UPPER TROUGH OVER WESTERN NORTH AMERICA
TODAY. SHORT WAVE ENERGY ON THE LEADING EDGE OF LARGER SCALE HEIGHT
FALLS IS ALREADY PRODUCING A BROAD LEE SIDE SURFACE TROUGH WITH LOW
PRESSURE CENTERED OVER SOUTH DAKOTA. THE PRIMARY SURFACE LOW WILL
MOVE INTO NORTHWEST ONTARIO TONIGHT AND HAVE A COLD FRONT TRAILING
SOUTHWARD INTO THE CENTRAL PLAINS. A STRONG LOW LEVEL JET TO THE
EAST OF THE LOW AND COLD FRONT IS SHOWN IN MODEL DATA TO REACH 50
KTS AT 850 MB OVER THE MIDWEST. THE RESULTING STRONG GULF MOISTURE
TRANSPORT WILL EITHER SUSTAIN SURFACE BASED CONVECTION FROM THE
AFTERNOON OR FUEL NOCTURNAL MCS CLUSTERS DURING THE NIGHT. THERE IS
GOOD MODEL AGREEMENT ON THE POSITION OF THE SURFACE TO 700 MB
THETA-E RIDGE REMAINING WEST OF LAKE MICHIGAN BY SUNRISE MONDAY BUT
SURGING EASTWARD DURING THE MORNING. THIS MEANS THAT LABOR DAY WILL
HAVE A PLEASANT START BUT COULD END UP STORMY BY MID AFTERNOON
THROUGH MONDAY NIGHT. MODEL SURFACE BASED CAPE WITH MAX TEMPS IN THE
MID 80S IS FORECAST TO RISE IN EXCESS OF 2000 J/KG OVER LOWER
MICHIGAN AND WILL COMBINE WITH A STRONG UNIDIRECTIONAL WIND PROFILE
TO PRESENT A SEVERE WEATHER RISK. AT A MINIMUM THIS ENVIRONMENT WILL
HELP ANY LINGERING MCS ACTIVITY REINTENSIFY OR LEAD TO A NEW ROUND
OF STORMS DURING AFTERNOON PEAK HEATING. THE LIKELY POPS IN OUR
GOING FORECAST LOOK SOLID IN BOTH SPACE AND TIME TO COVER THE
PATTERN THROUGH MONDAY AFTERNOON FOLLOWED BY FRONTALLY FORCED
SHOWERS AND STORMS MONDAY NIGHT. A SECONDARY SLUG OF MOISTURE IN THE
MODEL SOLUTIONS LATER IN THE NIGHT POINTS TO SOME HEAVY RAINFALL
POTENTIAL AS THE UPPER WAVE AND ENTRANCE REGION OF THE UPPER JET
ALIGN WITH THE FRONT. THE RESULTING LARGER SCALE AGEOSTROPHIC
CIRCULATION WILL HAVE POTENTIAL TO GENERATE A PERSISTENT PATTERN OF
SHOWERS AND STORMS BEFORE THE FRONT EXITS EAST AROUND SUNRISE
TUESDAY.

THE PASSAGE OF THE COLD FRONT EARLY TUESDAY WILL USHER IN A BROAD
AREA OF HIGH PRESSURE OF PACIFIC ORIGIN THAT WILL LAST FOR MUCH OF
THE MID WEEK PERIOD. A STRONG ZONAL UPPER AIR PATTERN AND LOW LEVEL
TEMPERATURE FIELDS IN THE MODEL DATA INDICATE THE SURFACE AIR MASS
WILL SUPPORT READINGS AROUND NORMAL...MAX TEMPS NEAR 80...FOR THE
FIRST WEEK OF SEPTEMBER ACCOMPANIED BY DRY CONDITIONS THROUGH
THURSDAY. THE GLOBAL MODELS ARE IN BETTER AGREEMENT THIS CYCLE ON
THE DEVELOPMENT OF THE NEXT LOW PRESSURE SYSTEM OVER THE PLAINS
THURSDAY INTO FRIDAY. THE BROAD AND STRONG UPPER LEVEL RIDGE IN
EXCESS OF 590 DM OVER THE SE U.S. WILL LIKELY FORCE THE SHORT WAVE
NORTH OF THE GREAT LAKES THURSDAY INTO FRIDAY BUT RETURNING
SOUTHERLY LOW LEVEL FLOW AND EVENTUALLY THE TRAILING COLD FRONT WILL
BRING A NEW CHANCE OF SHOWERS AND STORMS FRIDAY INTO SATURDAY.

MARINE...

MARINE CONDITIONS WILL BE MORE FAVORABLE IN ALL ASPECTS TODAY
COMPARED TO YESTERDAY. THE WIND WILL BE LIGHTER AND WAVES LOWER.
THERE IS A CHANCE OF THUNDERSTORMS OVER THE MARINE AREAS GENERALLY
FROM PORT HURON TO TOLEDO BUT COVERAGE WILL BE SCATTERED AT BEST.
LABOR DAY WILL THEN START OUT PLEASANT BUT WILL LIKELY BECOME STORMY
WITH SOME SEVERE WEATHER POTENTIAL DURING THE AFTERNOON THROUGH
MONDAY NIGHT AS A COLD FRONT MOVES THROUGH LAKE HURON AND LOWER
MICHIGAN. THIS FRONT WILL BRING HIGH PRESSURE INTO THE REGION DURING
TUESDAY WHICH WILL REMAIN IN CONTROL OF THE WEATHER THROUGH THURSDAY.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

AVIATION.....SF
SHORT TERM...SF
LONG TERM....BT
MARINE.......BT


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








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