Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KDTX 300735
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
335 AM EDT TUE SEP 30 2014

.SHORT TERM...TODAY AND TONIGHT

LOW LEVEL COLD AIR ADVECTION WILL PREVAIL THROUGH THE MORNING BEHIND
THE SURFACE COLD FRONT WHICH EXITED THE FORECAST AREA SHORTLY AFTER
06Z. LINGERING POST FRONTAL SHOWERS WILL EXIT TO THE SOUTHEAST OF
THE STATE BEFORE DAYBREAK. THE SHOWERS OVERNIGHT DEVELOPED WITHIN A
RIBBON OF STRONG LARGE SCALE ASCENT ALONG THE LEAD EDGE OF AN
AMPLIFYING UPPER WAVE. RECENT WATER VAPOR IMAGERY ALREADY SHOWS THE
EVOLUTION OF THIS SYSTEM INTO A CLOSED MID LEVEL LOW...WHICH IS
FORECAST TO ROTATE ACROSS THE THUMB THIS MORNING AND INTO NE OHIO
THIS AFTERNOON. THE ASSOCIATED SFC LOW...NOW LOCATED OVER SRN
ONTARIO...WILL IN TURN TRACK INTO WRN PA/WV THIS AFTERNOON.

RESIDUAL LOW LEVEL MOISTURE AND A DEEPENING POST FRONTAL INVERSION
HAS LED TO A STRATUS DECK NOW EXTENDING ALL THE WAY TO SRN LAKE
SUPERIOR. THIS INVERSION WILL ONLY DEEPEN DURING THE COURSE OF THE
MORNING AS 925MB TEMPS FALL THROUGH THE SINGLE DIGITS. LOW CLOUDS
WILL THUS REMAIN IN PLACE INTO AT LEAST LATE EVENING. THIS WILL
LIMIT ANY DIURNAL RECOVERY AND HOLD DAYTIME TEMPS IN THE 50S. THE
EVOLVING COMPACT MID LEVEL LOW WILL SUPPORT THE DEVELOPMENT OF AN
ENHANCED REGION OF MID LEVEL DEFORMATION /TROWEL FEATURE/ TARGETING
NRN/CNTL LAKE HURON AND NE LOWER MI. MODEL SOLUTIONS THEN INDICATE
THIS FEATURE FALLING APART AS IT ADVANCES INTO SE MI TONIGHT AS THE
UPPER LOW WEAKENS AND QUICKLY ADVANCES EAST. SO THE BETTER FORCING
WILL REMAIN NORTH OF THE AREA TODAY. HOWEVER...MODEL SOUNDINGS ARE
VERY SUPPORTIVE OF DRIZZLE TODAY /RADAR AND SFC OBS OVER NRN LOWER
MI OVERNIGHT HAVE ALSO BEEN SHOWING A LOT OF DRIZZLE/. THIS IS DUE
TO A MOIST BOUNDARY LAYER...LOW CLOUD BASES...SUBSTANTIAL DRY AIR
ABOVE THE INVERSION...AND GOOD DIRECTIONAL SHEAR NEAR THE TOP OF THE
MOIST LAYER. THE DRIZZLE IS EXPECTED TO BE QUITE WIDESPREAD OVER
MUCH OF THE THUMB TODAY AS N-NW FLOW OVER LAKE HURON ADDS A LITTLE
BETTER MOISTURE TO THE BOUNDARY LAYER AND ENHANCES CONVERGENCE ALONG
THE SHORELINE.

SFC RIDGING WILL BUILD ACROSS LOWER MI TONIGHT...WHILE ENHANCED
THERMAL TROUGHING WILL RESIDE OVER LAKE HURON. THE FLOW ABOVE THE
BOUNDARY LAYER WILL TURN TOWARD THE EAST WHICH WILL ACTUALLY SUPPORT
SOME LOW LEVEL WARM AIR ADVECTION. THIS WILL WEAKEN /POSSIBLY EVEN
ERODE/ THE LOW LEVEL INVERSION AND MAY SUPPORT SOME CLEARING ACROSS
AT LEAST THE WRN PORTIONS OF THE AREA AS THE SFC HIGH BUILDS IN FROM
THE NORTH. CLEARING POTENTIAL STILL HOWEVER CARRIES A LOW CONFIDENCE
AS THE EASTERLY FLOW WILL ALSO ADVECT SOME HIGHER MOISTURE IN FROM
THE EAST. SO FOG AND/OR ADDITIONAL STRATUS DEVELOPMENT SEEM
POSSIBLE. THE POTENTIAL CLOUD COVER AND LOW LEVEL MOISTURE ADVECTION
WILL WARRANT A LIMITED DROP IN TEMPS TONIGHT /LOWS FROM THE MID 40S
TO LOW 50S/.

&&

.LONG TERM...

CONFIDENCE IS NOT VERY HIGH IN LOW CLOUDS SCOURING OUT COMPLETELY
ON WEDNESDAY...AS NAM/GFS/GEM/EURO ALL SUGGESTING SOME 925-850 MB
RESIDUAL MOISTURE UNDERNEATH THE MODEST UPPER LEVEL
RIDGE...ESPECIALLY BACK ACROSS THE THUMB REGION. WITH JUST PARTIAL
INSOLATION EXPECTED...LOOKING AT MAXES COMING UP JUST SHORT OF 70
DEGREES. WE SHOULD HOWEVER HAVE NO PROBLEM CLIMBING INTO THE 70S ON
THURSDAY AHEAD OF A COLD FRONT...WITH GOOD WARM ADVECTION ALLOWING
925 MB TEMPS TO CLIMB INTO THE UPPER TEENS TO LOWER 20S PER 00Z
EURO. HOWEVER...WITH INCREASING AND THICKENING CLOUDS...BACKED
SOUTHEAST FLOW AT THE SURFACE...BOUNDARY LAYER MIXING WILL PROBABLY
COME UP JUST SHORT OF 925 MB AND WILL HOLD MAXES IN THE MID TO
UPPER 70S.

WITH A VERY GOOD MOISTURE FEED...PW VALUES IN EXCESS OF 1.5
INCHES...COUPLED WITH GOOD HEIGHT FALLS AND MODEST INSTABILITY
THURSDAY NIGHT...RAIN SHOWERS CAN BE EXPECTED...WITH EVEN COLDER AIR
ON TAP FOR THE WEEKEND AS UPPER LEVEL ENERGY OVER THE GULF OF ALASKA
AND OFF THE COAST OF BRITISH COLUMBIA/PACIFIC NORTHWEST CONSOLIDATE
OVER THE GREAT LAKES REGION...LEADING TO DEEP 500 MB LOW. IN
FACT...THE LONGWAVE UPPER LEVEL TROUGH AXIS WILL BE ATTEMPTING TO GO
SLIGHTLY NEGATIVE FRIDAY MORNING...WHICH IS YIELDING A SLOWER
FRONTAL PASSAGE COMPARED TO LAST NIGHT...AND IT APPEARS SHOWERS WILL
LIKELY LINGER INTO FRIDAY. COLD CYCLONIC FLOW AND 850 MB TEMPS
FALLING BELOW ZERO OVER THE WEEKEND WILL LIKELY TRANSLATE TO AT
LEAST SCATTERED LAKE ENHANCED SHOWERS AND MOSTLY CLOUDY SKIES...WITH
FORECASTED 850 MB TEMPS OF -2 C YIELDING HIGHS ONLY IN THE LOW TO
MID 50S ON SATURDAY.

&&

.MARINE...

A STRONG COLD FRONT WILL CLEAR THE CENTRAL GREAT LAKES THIS
MORNING...WITH RELATIVELY SHORT LIVED WINDS OF 15 TO 20 KNOTS WITH
GUSTS TO 25 KNOTS ACROSS CENTRAL AND SOUTHERN SECTIONS OF LAKE
HURON.  THIS WILL PROMPT AN INCREASE IN WAVE HEIGHTS...WITH HEIGHTS
TOPPING OUT SLIGHTLY ABOVE 4 FEET OVER MUCH OF SOUTHERN LAKE
HURON...AND THE PREVIOUS SMALL CRAFT ADVISORIES WILL CONTINUE
THROUGH THE DAY. WINDS WILL DIMINISH BY TONIGHT AS HIGH PRESSURE
BUILDS BACK INTO THE REGION...BUT THE NORTHEAST DIRECTION WILL
MAINTAIN SOME MODEST WAVES OVER THE NEARSHORE WATERS. LIGHT WINDS
AND LOW WAVES WILL PERSIST WEDNESDAY INTO THURSDAY.
HOWEVER...SOUTHERLY WINDS DEVELOPING AHEAD OF A COLD FRONT LATE
THURSDAY COULD RESULT IN WINDS UP TO 30 KNOTS OVER THE OPEN WATERS
OF LAKE HURON THURSDAY NIGHT.

&&

.AVIATION...ISSUED 1212 AM EDT TUE SEP 30 2014

//DISCUSSION...

AVIATION WEATHER IN SE MICHIGAN REMAINS TIED TO THE PASSAGE OF A
STRONG COLD FRONT...NOT AS MUCH WIND AS IN TEMPERATURE...AND THE
RESULTING COLDER AIR MASS SETTLING IN BEHIND THE FRONT. AT PRESS
TIME...THE FRONT ONLY HAD TO MOVE THROUGH THE DTW TERMINAL CORRIDOR
WITH MODEST SPEED BUT SHARP WIND SHIFT TO THE NORTHWEST AND A
PATTERN OF SHOWERS WITH MARGINAL MVFR RESTRICTION. THE RAIN WILL
ONLY LAST A FEW HOURS AND THEN LEAVE WIDESPREAD IFR CEILING THROUGH
THE MID MORNING IN THE DTW AREA...MVFR FARTHER NORTH TOWARD MBS.
CEILING WILL GRADUALLY RISE DURING THE DAY BUT REMAIN LOCKED IN AT
MVFR OVER COOL NORTH WIND.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CEILING BELOW 5000 FEET THROUGH TODAY.

&&

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

LAKE HURON...
     SMALL CRAFT ADVISORY...OUTER SAGINAW BAY AND THE NEARSHORE WATERS
     FROM PORT AUSTIN TO PORT SANILAC...UNTIL 6 PM TUESDAY.

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

&&

$$

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


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






USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.