Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 242330
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
730 PM EDT SUN AUG 24 2014

.AVIATION...

//DISCUSSION...

CLOUDS KEPT AFTERNOON TEMPERATURES BELOW PEAK HEATING POTENTIAL AND
WILL HAVE A HEAD START ON NIGHT TIME COOLING WHICH WILL KEEP FOG IN
THE PICTURE FOR AVIATION INTERESTS LATER TONIGHT AND MONDAY MORNING.
SATELLITE IMAGERY IS BEGINNING TO SUPPORT A DRIER LOOK TO THE LOW
LEVEL MOISTURE PROFILE IN THE 950-925 MB LAYER DEPICTED BY THE
LATEST MODEL DATA. THIS SEEMS TO BE PRIMARILY A RESULT OF BACKING
LOW LEVEL FLOW TOWARD THE SOUTH THAT IS DRAWING A STREAMLINE FROM
THE MID APPALACHIANS AND HAVING LESS MOISTURE INFLUENCE FROM THE
GREAT LAKES. WHILE HIGHER BASED CLOUDS WILL BE POSSIBLE...THE DRIER
SOURCE REGION MAY DELAY OR PREVENT MVFR STRATUS FORMATION OVER SE
MICHIGAN EARLY IN THE OVERNIGHT. AT THE SAME TIME...SURFACE WIND
WILL REMAIN FROM THE SOUTHEAST AND KEEP A LAKE ERIE/ST CLAIR
CONTRIBUTION TO SURFACE MOISTURE TO MAINTAIN FOG POTENTIAL AND/OR
LIFR STRATUS TOWARD SUNRISE AT DTW/YIP AND LIKELY PTK AS WELL...
ESPECIALLY IF VFR CEILING DRIFTS OUT OF THE REGION BY THEN. THE GOOD
NEWS HERE IS THAT MODEL FORECAST SOUNDINGS DO INDICATE A FASTER RATE
OF IMPROVEMENT BY MONDAY AFTERNOON COMPARED TO RECENT DAYS.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CEILING AOB 5000 FT OVERNIGHT INTO MONDAY
  MORNING.

* LOW CONFIDENCE FOR CEILING BELOW 200 FEET AND/OR VISIBILITY BELOW
  1/2SM EARLY MONDAY MORNING.

&&

.PREV DISCUSSION...ISSUED 320 PM EDT SUN AUG 24 2014

SHORT TERM...TONIGHT

ITS BEEN AN ALL DAY PROCESS REMOVING THE LOW CLOUDS ACROSS SOUTHEAST
MICHIGAN...AS 12Z DTX SOUNDING SHOWED A VERY STRONG INVERSION JUST
ABOVE 3000 FEET. NONE-THE-LESS..LOCATIONS WHICH HAVE BEEN ABLE TO
DEVELOP PARTIAL SUNSHINE HAVE/WILL HAVE RISEN TO AROUND 80 DEGREES.
WITH THE LOW LEVEL FLOW STILL LIGHT EASTERLY AND LOW LEVEL MOISTURE
STILL NOT FULLY SCOURED OUT AS WE EXIT PEAK HEATING...ANOTHER ROUND
OF LOW CLOUDS AND/OR FOG SEEMS LIKELY TONIGHT. THE ONLY
HINDRANCE/WILD CARD IS THE SHEARED OUT UPPER WAVE SLOWLY WORKING
THROUGH LOWER MICHIGAN...EMBEDDED IN THE BACKDROP OF THE LARGE SCALE
UPPER LEVEL RIDGE. THIS FEATURE SHOULD SUPPORT SOME MID CLOUDS...BUT
DO NOT THINK IT WILL BE ENOUGH TO PREVENT THE LOW CLOUDS AND/OR FOG
FROM DEVELOPING. CURRENT MID 60 DEW PTS LOOK LIKE A GOOD BOTTOM
FOR TEMPS TONIGHT...IN LINE WITH LATEST GUIDANCE.

LONG TERM...MONDAY THROUGH SATURDAY

EXISTING UPPER RIDGE AXIS ANCHORED OVERHEAD EARLY MONDAY WILL
STEADILY TRANSITION EASTWARD AND DAMPEN THROUGH THE MID WEEK
PERIOD.  THIS PROCESS WILL EVOLVE AS A COMPACT MID LEVEL CIRCULATION
NOW OVER THE NORTHERN ROCKIES EJECTS NORTHEAST AND ACROSS WESTERN
ONTARIO.  THIS WILL ALLOW MODEST HEIGHT FALLS ALONG THE SOUTHERN
PERIPHERY TO EASE INTO THE GREAT LAKES...SENDING AN ATTENDANT WEAK
FRONTAL BOUNDARY INTO LOWER MICHIGAN BY TUESDAY.  A DEEPENING
PRE-FRONTAL LOW LEVEL SOUTHWEST FLOW TUCKED BENEATH 500 MB HEIGHTS
OF 590 DM STILL POINTS TOWARD AN INCREMENTAL UPWARD ADJUSTMENT IN
DAYTIME HIGHS FOR MONDAY.  THIS PATTERN DOES REMAIN VERY CONDUCIVE
TO AN EXTENSIVE LOW STRATUS/FOG COMPONENT TO EXIST EARLY IN THE
DAY...LIKELY TEMPERING THE DIURNAL RESPONSE TO SOME DEGREE.  HOWEVER
THE SOLID LATE DAY INSOLATION AND WARM AIR ADVECTION WILL MAKE THE
MOST OF 18-19C 850 MB TEMPERATURES...HIGHS ARRIVING IN THE MIDDLE
AND UPPER 80S.  LOW LEVEL MOISTURE ADVECTION WILL ADD TO THE
HUMIDITY AS WELL...DEWPOINTS CLIMBING INTO THE UPPER 60S.  THIS WILL
BRING AFTERNOON HEAT INDICES INTO THE LOWER 90S.  CAPPED MID LEVEL
PROFILE AND LACK OF ANY TANGIBLE FORCING CONTINUES TO SUPPORT A DRY
FORECAST THROUGH THE AFTERNOON HOURS.

CONVECTIVE POTENTIAL BECOMES MORE COMPLEX STARTING MONDAY EVENING/
NIGHT.  GREATER PROSPECTS FOR LATE DAY CONVECTIVE INITIATION WILL
TEND TO CENTER ACROSS WISCONSIN AND/OR THE UPPER PENINSULA AS THE
INBOUND FRONTAL BOUNDARY WORKS INTO A LESS CAPPED AND STRONGLY
CONDITIONALLY UNSTABLE ENVIRONMENT.  THE POTENTIAL DOES EXIST FOR
SOME DEGREE OF UPSCALE EXPANSION OF THIS ACTIVITY EAST/SOUTHEAST
INTO LOWER MICHIGAN AFTER SUNSET.  IN ADDITION...POSSIBLE NOCTURNAL
MCS ACTIVITY EMERGING ALONG THE RIDGE PERIPHERY ACROSS EASTERN
NEBRASKA/IOWA MAY ENTER THE PICTURE BY TUESDAY MORNING.  THE HIGH
DEGREE OF UNCERTAINTY IN THIS SCENARIO CONTINUES TO WARRANT A
CONSERVATIVE APPROACH WITH POPS REMAINING AT A LOWER END CHANCE.

CONVECTIVE CHANCES AND OVERALL STRENGTH AS THE FRONTAL BOUNDARY
SHIFTS ACROSS SE MICHIGAN LATE TUESDAY WILL THEN CARRY A STRONG
DEPENDENCE ON THE SCALE AND TIMING OF ANY EARLY DAY PRECIPITATION/
CLOUD DEBRIS.  HIGHS AGAIN OF UPPER 80S LOOK ATTAINABLE UNDER A
SIMILAR THERMO PROFILE...ASSUMING LIMITED EARLY DAY DISRUPTION TO
THE HEATING CYCLE.  THIS WOULD YIELD AT LEAST A MODERATELY UNSTABLE
ENVIRONMENT DURING THE PEAK HEATING FROPA.  WIND FIELDS WILL BE
LACKING IN OVERALL MAGNITUDE...WITH A NOTED INCREASE IN THE DEEP
LAYER SHEAR TRAILING THE FRONTAL PASSAGE.  HOWEVER GIVEN THE DEGREE
OF INSTABILITY...A FEW STRONG TO POSSIBLY SEVERE MULTICELL CLUSTERS
LOOK PLAUSIBLE LATE TUESDAY.

MAIN HIGHLIGHT IN THE EXTENDED PERIOD...WEDNESDAY THROUGH
SATURDAY...WILL BE THE COOLER AIR THAT WILL BE FILTERING INTO THE
AREA.  HOWEVER...FOCUS IS STILL ON THE THE BAROCLINIC ZONE THAT IS
FORECAST TO SLIDE AND SET UP JUST TO THE SOUTH MEANING PRECIPITATION
CHANCES WILL EXTEND INTO WEDNESDAY BEFORE HIGH PRESSURE PUSHES IN
FROM THE NORTH.  MODELS ARE SHOWING THE UPPER LEVEL RIDGE AND
ASSOCIATED HIGH PRESSURE HOLDING THROUGH AT LEAST THURSDAY NIGHT
BEFORE THE NEXT SYSTEM MOVES TOWARDS THE GREAT LAKES REGION BY THE
END OF THE WEEK AND INTO THE WEEKEND.

MARINE...

A PERSISTENT MOIST EASTERLY FLOW WILL AGAIN RESULT IN SOME AREAS OF
FOG TONIGHT THROUGH EARLY MONDAY.  THE LOW LEVEL WINDS WILL THEN
TURN MORE TOWARD THE SOUTH ON MONDAY AS A COLD FRONT APPROACHES THE
NORTHERN GREAT LAKES. VERY WARM AIR LIFTING INTO THE AREA AHEAD OF
THIS FRONT WILL KEEP STABILITY VERY HIGH OVER THE LAKES AND THUS
KEEP WINDS AND WAVES IN CHECK. THE FRONT WILL SLOWLY PROGRESS FROM
NORTHERN LAKE HURON MONDAY NIGHT INTO THE OHIO VALLEY ON WEDNESDAY.
THIS FRONT WILL SUSTAIN A CHANCE OF STRONG STORMS AS IT TRACKS
ACROSS THE REGION.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

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


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








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