Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 232313
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
713 PM EDT SAT AUG 23 2014

.AVIATION...

//DISCUSSION...

LATE AFTERNOON CONDITIONS RETURNED TO VFR AFTER A SLOW IMPROVING
TREND FROM THE LIFR COMBINATION OF FOG AND STRATUS DURING THE
MORNING. THE LARGE SCALE PATTERN REMAINS FAVORABLE FOR REDEVELOPMENT
OF SIMILAR CONDITIONS LATER TONIGHT AS HIGH PRESSURE REMAINS IN
PLACE OVER ONTARIO AND QUEBEC. THE ASSOCIATED EASTERLY FLOW IS
UNUSUALLY MOIST FOR HAVING HIGH PRESSURE ORIGIN AND...COMBINED
WITH CONTRIBUTIONS FROM THE LAKES...ANOTHER ROUND OF IFR/LIFR FOG
AND STRATUS IS EXPECTED LATER TONIGHT THROUGH SUNDAY MORNING.
SURFACE WIND BACKING TOWARD THE SOUTHEAST DURING SUNDAY AFTERNOON
MAY HELP WITH A FASTER PACE OF IMPROVEMENT COMPARED TO EARLIER
TODAY BUT NOT BY MUCH.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CEILING BELOW 5000 FT LATE TONIGHT AND SUNDAY.

* MODERATE CONFIDENCE/POTENTIAL FOR CEILING BELOW 200 FEET AND LOW
CONFIDENCE IN VISIBILITY BELOW 1/2SM AROUND SUNRISE SUNDAY.

&&

.PREV DISCUSSION...ISSUED 350 PM EDT SAT AUG 23 2014

SHORT TERM...TONIGHT

HIGH AMPLITUDE UPPER RIDGING TAKING A PROGRESSIVE HOLD ACROSS SE
MICHIGAN TODAY.  THE ASSOCIATED WARMING THROUGHOUT THE MID LEVELS
WORKING OVER A PREVAILING AND RELATIVELY STABLE LOW LEVEL EASTERLY
FLOW MITIGATING THE POTENTIAL FOR LATE DAY CONVECTIVE DEVELOPMENT.
NOTING THE ONGOING LINEAR AREA OF CONVECTION CURRENTLY SPILLING
EAST-SOUTHEAST IN THE VICINITY OF CHICAGO...REMAIN IN FULL
AGREEMENT WITH LATEST ARRAY OF MODEL GUIDANCE WHICH QUICKLY
EXTINGUISHES ANY ACTIVITY THAT MIGRATES EAST OF A LAKE MICHIGAN
LATITUDE UNDER INCREASINGLY LESS SUPPORTIVE THERMODYNAMICS WITH
EASTWARD EXTENT.  OTHERWISE...MAIN ITEM FOR TONIGHT WILL AGAIN BE
THE POTENTIAL FOR LOW STRATUS AND FOG DEVELOPMENT.  OVERALL SYNOPTIC
PATTERN AND EXISTING AIRMASS SUPPORTING DEVELOPMENT REMAINS LARGELY
UNCHANGED FROM THAT NOTED THIS MORNING...ALTHOUGH THE MEAN LOW LEVEL
FLOW WILL VEER SLIGHTLY TO AN EASTERLY COMPONENT.  THIS MAY TEND TO
DIRECT A MORE SIZABLE PORTION OF THE LAKE HURON MOISTURE FLUX INTO
THE SAGINAW BAY/THUMB CORRIDOR AND POINTS NORTH...BUT WOULD ALSO
INTRODUCE A LAKE ERIE COMPONENT AS WELL FOR THE SOUTHERN COUNTIES.
ASSESSMENT OF MODEL SFC-950MB RH FIELDS POINT IN THIS DIRECTION.
LOWS TONIGHT AGAIN IN THE 60 TO 65F RANGE.

LONG TERM...

UPPER LEVEL RIDGE/BUILDING HEIGHTS OVER LOWER MICHIGAN ON SUNDAY
WILL ONLY FURTHER HELP TRAP NEAR SURFACE MOISTURE WITH THE
STRENGTHENING LOW LEVEL INVERSION...AND BURNOFF OF FOG AND LOW
CLOUDS WILL BE A WORK IN PROGRESS THROUGH MUCH OF THE DAY...HELPING
SUPPRESSING MAXES IN THE LOWER 80S. MORE OF THE SAME SUNDAY NIGHT
INTO MONDAY...HOWEVER SHIFT IN THE LOW LEVEL FLOW DURING MONDAY TO
THE SOUTH-SOUTHWEST...ALONG WITH MODEST INCREASE IN THE GRADIENT
SHOULD HELP ACCELERATE THE PROCESS OF BURNING OFF LOW
CLOUDS/FOG...HELPING TO ACHIEVE MAX TEMPS CLOSER TO THE AIRMASS
POTENTIAL...WHICH WILL BE 90+ DEGREES AS 850 MB TEMPS WARM TO 19-20
C. AS SUCH..WILL MAINTAIN THE UPPER 80S FORECAST DUE TO THE LOW
LEVEL MOISTURE HINDRANCE.

DEEP UPPER LEVEL LOW/TROUGH OVER THE ROCKIES WILL BE TRACKING OFF
TO THE NORTHEAST...AND MOVING INTO MANITOBA/ONTARIO EARLY NEXT
WEEK...WITH MARGINAL HEIGHT FALLS OVER THE SOUTHERN GREAT LAKES ON
TUESDAY. THIS WILL LEAD TO ANOTHER VERY WARM DAY (BARRING EARLY DAY
INITIATION)...WITH AIRMASS ADVERTISED TO BE MUCH MORE UNSTABLE AS
WEST-EAST MOISTURE PLUME LINES UP OVER THE GREAT LAKES
REGION...FACILITATING CAPES OF 2000-3000 J/KG. EVEN WITH THE BEST
0-6 KM BULK SHEAR DISPLACED TO OUR NORTH...AMOUNT OF INSTABILITY
WOULD BE CONDUCIVE TO SEVERE STORMS IF STORMS INITIATE WITH THE WEAK
LOW LEVEL CONVERGENCE FIELDS. WITH THE AMPLE MOISTURE
PRESENT...BUMPED UP POPS. SLOW MOVEMENT WILL BRING WITH IT AN
ELEVATED HEAVY RAIN THREAT.

THE EXTENDED FORECAST THROUGH THE END OF NEXT WEEK IS MARKED BY
CONTINUED PRECIP CHANCES AND SLIGHTLY COOLER TEMPERATURES. MODELS
ARE SHOWING THE LARGE UPPER LEVEL HIGH THAT HAD BEEN POSITIONED OVER
THE SOUTHEASTERN CONUS SLIDING FURTHER SOUTH.  THIS WILL ALLOW THE
GREAT LAKES REGION TO BE IN POSITION FOR CONTINUAL ROUNDS OF
CONVECTION AS MULTIPLE SHORTWAVES RIDE ALONG THE BOUNDARY THAT LOOKS
TO SET UP ACROSS THE AREA.  WEDNESDAY HIGH TEMPS WILL REACH INTO THE
LOWER 80S BEFORE SOUTHERLY WINDS START SHIFTING TO THE WEST BY
THURSDAY.  THE WESTERLY/NORTHWESTERLY WINDS WILL BRING IN COOLER AIR
AS AN UPPER LEVEL TROUGH BECOMES POSITIONED OVER THE REGION WITH
HIGH TEMPS BACKING OFF INTO UPPER 70S.

MARINE...

FOG AND LOW CLOUDS CONTINUE TO ERODE AND SHRINK IN COVERAGE...WILL
ALLOW DENSE FOG ADVISORY TO EXPIRE AT 4 PM AND CARRY AREAS OF FOG IN
THE FORECAST.

EASTERLY WINDS WILL PERSIST THROUGH THE DURATION OF THE WEEKEND AS
HIGH PRESSURE REMAINS CENTERED ACROSS THE EASTERN GREAT LAKES.
OVERALL...WINDS WILL REMAIN LIGHT ALTHOUGH SOME GUSTS OVER 12 KNOTS
ARE POSSIBLE FROM TIME TO TIME ACROSS SAGINAW BAY WHERE THE WATER IS
WARM AND WINDS GET FUNNELED INTO THE BAY. THE HIGH WILL DRIFT EAST
BY MONDAY ALLOWING WINDS TO VEER TOWARD THE SOUTH. WARMER AIR WILL
OVERSPREAD THE REGION WHICH WILL INCREASE THE STABILITY OVER THE
LAKES...KEEPING THE WIND SPEEDS IN CHECK. WARM AND MOISTURE AIR WILL
CONTINUE TO BRING WITH THE POTENTIAL FOR LOW CLOUDS AND
FOG...PRIMARY DURING THE EARLY MORNING HOURS.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

AVIATION.....BT
SHORT TERM...MR
LONG TERM....SF/SS
MARINE.......SF


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AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).






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