Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

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FXUS63 KDTX 150046
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
746 PM EST SUN DEC 14 2014

.UPDATE...

FOG CONTINUES TO GRADUALLY THICKEN GENERALLY ALONG AND NORTH OF
THE M 59 CORRIDOR WITH LOCALLY DENSE FOG BECOMING MORE COMMON
DURING THE PAST 1 TO 2 HOURS. GIVEN THESE TRENDS...FEEL A DENSE
FOG ADVISORY IS IN ORDER FOR THESE AREAS INTO MONDAY MORNING AS
THIS PROCESS SHOULD CONTINUE INTO THE OVERNIGHT HOURS WITH DENSE
FOG BECOMING MORE WIDESPREAD WITH TIME. WILL LIMIT THE ADVISORY TO
THE M 59 COUNTIES NORTHWARD FOR NOW AS MUCH DRIER LOW LEVEL AIR
HAS WORKED INTO THE SOUTHERN CWA WITH VISIBILITIES AT 6 MILES OR
MORE AND MUCH HIGHER CEILINGS IN MOST LOCATIONS FROM DETROIT
SOUTH. THESE AREAS CAN BE WATCHED LATER TONIGHT IF FOG FORMATION
BECOMES AGGRESSIVE ENOUGH.

&&

.AVIATION...ISSUED 556 PM EST SUN DEC 14 2014

//DISCUSSION...

IFR/LIFR CIGS LOOK TO PERSIST KPTK NORTHWARD WHERE VSYBS WILL ALSO
DROP TO 2SM OR LOWER AT TIMES THIS EVENING. THESE CONDITIONS SHOULD
PERSIST/INCREASE INTO THE OVERNIGHT HOURS AS FG/DZ INCREASE. MVFR
CIGS ALONG THE I 94 TERMINALS ARE EXPECTED TO LOWER BACK TO IFR
OVERNIGHT AS WELL WITH SOME INCREASE IN FOG. ANY IMPROVEMENT IN
CIGS/VSBYS DUE TO DAYTIME MIXING ON MONDAY WILL LIKELY REVERSE INTO
MONDAY EVENING AS LOW LEVEL MOISTURE CONTINUES TO INCREASE ON A
STEADY SOUTH/SOUTHEAST WIND THAT WILL DEVELOP IN ADVANCE OF AN
APPROACHING LOW PRESSURE SYSTEM.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CEILINGS BELOW 5000 FEET THROUGH THE TAF PERIOD.

* LOW CONFIDENCE IN CIGS AT 200 FEET AND/OR VSBYS AOB 1/2SM BY
  10Z-14Z MONDAY AM.

&&

.PREV DISCUSSION...ISSUED 312 PM EST SUN DEC 14 2014

SHORT TERM...THIS AFTERNOON AND TONIGHT

THE LARGE SCALE RIDGE IN PLACE ACROSS THE GREAT LAKES WILL SLOWLY
HEAD EAST DURING THE OVERNIGHT HOURS. DESPITE THE EASTWARD
PROGRESSION OF THIS FEATURE THE AREA WILL SEE ANOTHER REPEAT OF THE
LAST FEW DAYS OF LOW CLOUDS AND DRIZZLE DURING THE OVERNIGHT HOURS.
A DEVELOPING WARM FRONT AND INCREASED MOISTURE COULD BRING SOME
SHOWERS TO THE AREA AS IT LIFTS NORTH...HOWEVER DRIZZLE STILL
APPEARS TO BE THE MAIN THREAT GIVEN THE STABILITY AFFORDED BY THE
STILL STRONG INVERSION IMPOSED BY THE MID LEVEL RIDGING.

DESPITE SOME CLEARING ACROSS THE FAR SOUTHERN CWA THIS
AFTERNOON...THIS APPEARS TO BE A SUCKER HOLE AS ADDITIONAL UPSTREAM
MOISTURE ADVECTS IN FROM THE WEST DURING THE EVENING HOURS. THE
PRESSURE GRADIENT SHOULD SLACKEN TONIGHT...ALLOWING WINDS TO BECOME
LIGHT WHICH SHOULD AID IN THE DEVELOPMENT OF FOG WITH A CONTINUED
MOIST SURFACE LAYER AS DRIZZLE FALLS. UPSTREAM OBSERVATIONS THIS
MORNING OF DENSE FOG ARE CERTAINLY A CONCERN AS THIS AIRMASS ADVECTS
EAST. HOWEVER MOS GUIDANCE IS A BIT LESS BOLD WITH THE FOG FORMATION
THIS RUN...ESPECIALLY ACROSS THE SOUTHERN CWA WHICH IS NOT
SURPRISING GIVEN THE CURRENT BREAK IN THE CLOUD COVER AND ELEVATED
CEILINGS. AS THE DEVELOPING WARM FRONT LIFTS NORTH IT IS ALSO NOT
CLEAR IF THESE RISING CEILINGS WILL MAKE THEIR WAY NORTH...SQUASHING
THE POTENTIAL FOR DENSE FOG DEVELOPMENT AS DRIZZLE BECOMES LESS
LIKELY. GIVEN THE BACKING OFF FROM THE PREVIOUS FORECAST AND
UNCERTAINTY WILL FORGO A HEADLINE WITH THIS ISSUANCE AND CONTINUE TO
MONITOR OBSERVATIONS FOR ANY DENSE FOG HEADLINES THAT NEED TO BE
ISSUED. THE BEST POTENTIAL APPEARS TO BE ALONG AND NORTH OF M-59
WITH THE CONTINUED LOW CEILINGS AND RESTRICTIONS TO VISIBILITIES.

LONG TERM...

POTENT UPPER WAVE CENTERED CLOSE TO THE PANHANDLE...WITH NEGATIVELY
TILTED UPPER LEVEL TROUGH AXIS ROTATING THROUGH THE REST OF TEXAS.
THE AMPLIFIED PATTERN IN PLACE OVER THE CONUS WILL CAUSE THE
CENTER/MID LEVEL CIRCULATION OF THIS SYSTEM TO ARRIVE OVER LOWER
MICHIGAN A TOUCH SLOWER THAN NORMAL. HOWEVER...GOOD 500 MB HEIGHT
FALLS AND NICE 850-700 MB THETA-E RIDGE AXIS WILL BE ARRIVING MONDAY
EVENING/NIGHT...WHICH SHOULD SUPPORT WIDESPREAD SHOWERS WITH GOOD
ISENTROPIC ASCENT (290-295 K)...AS MARGINAL INSTABILITY ALSO
DEVELOPS WITH SHOWALTER INDEX FALLING TOWARD ZERO TUESDAY MORNING.
HIGH MOISTURE CONTENT FOR MID DECEMBER STANDARDS...PW VALUES JUST
ABOVE THREE QUARTERS OF AN INCH. 500 MB HEIGHT RISES WILL ACTUALLY
TAKE PLACE TUESDAY AFTERNOON...AS THE NORTHERN STREAM TROUGH/WAVE
DROPPING INTO MINNESOTA ACTS A KICKER/SEPARATE ENTITY. THIS IS
CAUSING AN ISSUE WITH THE EXACT PLACEMENT OF THE SURFACE LOW
FEATURE...AS THERE LOOKS TO BE A ILL DEFINED LOW PRESSURE AREA
ACROSS MOST OF LOWER MICHIGAN ON TUESDAY. NO REAL CONCERNS FOR SNOW
THROUGH 00Z WEDNESDAY...AS 925 MB TEMPS REMAIN AROUND 3 C AT THE END
OF THE DAY. GOOD SURGE OF LOW LEVEL COLD ADVECTION TUESDAY EVENING
WILL SUPPORT THE POSSIBILITY OF ANY LINGER RAIN SHOWERS CHANGING TO
SNOW SHOWERS. HOWEVER...AGGRESSIVE MID LEVEL DRY SLOT WILL BE
PUSHING IN AROUND MIDNIGHT...LIKELY SHUTTING OFF THE PRECIPITATION.
INHERITED TEMPERATURES MONDAY-TUESDAY NIGHT LOOKED REASONABLE AND
MADE NO CHANGES. WAS TEMPTED TO RAISE TEMPS SLIGHTLY TOMORROW...BUT
SURFACE WINDS COMING OUT OF THE SOUTHEAST OFF COOL WATERS OF LAKE
ERIE/ST. CLAIR DECIDED AGAINST IT.

POCKET OF COLDEST H85 AIR /-10 TO -15C/ WILL BE OVER LOWER MICHIGAN
FROM 12Z WED TO 12Z THURSDAY. DEPTH OF DRY AIR WILL LIMIT LAKE
MICHIGAN RESPONSE...THOUGH A FEW FLURRIES/LIGHT SNOW SHOWERS CANNOT
BE RULED OUT DURING THIS TIMEFRAME. SURFACE HIGH PRESSURE WILL BUILD
IN TO THE WESTERN GREAT LAKES THURSDAY AND FRIDAY KEEPING THINGS DRY
WITH SEASONABLE TEMPERATURES. 12Z MODEL CONSENSUS KEEPS A MORE
SIGNIFICANT STORM TO OUR SOUTH FOR NEXT WEEKEND /SAVE THE GFS/ BUT
WITH CHARACTERISTIC UNCERTAINTY WILL KEEP LOW CHANCE POPS IN THE
FORECAST.

MARINE...

MILD AND MOIST AIR WILL CONTINUE TO STREAM INTO THE CENTRAL GREAT
LAKES THROUGH TUESDAY. THE LIGHT WIND AND INCREASED STABILITY OVER
THE WATER WILL RESULT IN FAVORABLE WAVE CONDITIONS UNTIL THE NEXT
LOW PRESSURE SYSTEM SLIDES THROUGH THE SOUTHERN GREAT LAKES TUESDAY.
THIS SYSTEM WILL BRING RAIN TO THE AREA FOLLOWED BY COLDER AIR AND
STRONGER NORTHWEST WINDS GUSTING NEAR 30 KNOTS OVER THE OPEN WATERS
OF NORTHERN LAKE HURON TUESDAY NIGHT INTO WEDNESDAY.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...DENSE FOG ADVISORY UNTIL 10 AM EST MONDAY FOR MIZ047>049-053>055-
     060>063-068>070.

LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MICHIGAN WATERS OF LAKE ERIE...NONE.
&&

$$

UPDATE.......DG
AVIATION.....99
SHORT TERM...KURIMSKI
LONG TERM....SF/DT
MARINE.......SF


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