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 212324 CCA
AFDDTX

AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
704 PM EDT TUE OCT 21 2014

CORRECTED TO ADD PREVIOUS DISCUSSION

.AVIATION...

THE CLEARING WHICH HAS BEEN PUSHING ACROSS THE SAGINAW VALLEY THIS
EVENING SHOULD SLOW ITS SOUTHEASTWARD PROGRESS OVER THE NEXT HOUR OR
SO AS THE LOW LEVEL FLOW REMAINS N-NE OVER LAKE HURON. A PERSISTENT
LOW LEVEL INVERSION AND ADDED MOISTURE SHOULD SUSTAIN CLOUDS WELL
INTO THE DAY WED. THE LOW LEVEL FLOW WILL VEER MORE TOWARD THE NE
THIS EVENING...WHICH SHOULD CAUSE THE CLOUDS TO ADVANCE BACK INTO
MBS. ALTHOUGH AVAILABLE OBSERVATIONS ACROSS THE THUMB SUGGEST THE
HEAT FLUX OFF LAKE HURON IS LIFTING CLOUD BASES...LARGE SCALE
SUBSIDENCE THROUGH THE NIGHT SHOULD HOLD INVERSION HEIGHTS LOW
ENOUGH TO SUPPORT MAINLY MVFR BASED CLOUDS.

FOR DTW...GIVEN THE SLIGHT DOWNSLOPE OFF THE HIGHER
TERRAIN...CEILING HEIGHTS MAY FLUCTUATE ABOVE AND BELOW 3K FT INTO
THE MORNING.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CEILINGS BELOW 5000 FT TONIGHT AND MONDAY
  MORNING. MEDIUM CONFIDENCE MONDAY AFTERNOON.

&&

.PREV DISCUSSION...ISSUED 418 PM EDT TUE OCT 21 2014

.SHORT TERM...TONIGHT

STRONGLY CYCLONIC FLOW AROUND THE NW PERIPHERY OF THE DEPARTING
CLOSED LOW CONTINUES TO SUPPORT EXTENSIVE STRATOCU ACROSS SE
MICHIGAN THIS AFTERNOON. EROSION OF THIS CLOUD DECK FROM NW TO SE IS
NOTED OVER NORTHERN LOWER AS DRIER AIR FILLS IN JUST BEHIND THE AXIS
OF DEEPER MOISTURE. INDICATIONS FROM THE 12Z MODEL SUITE, HOWEVER,
ARE THAT THIS EROSION WILL SLOW AS THE NOCTURNAL INVERSION
STRENGTHENS LATER THIS EVENING AND MOIST NORTHERLY FLOW PERSISTS OFF
OF LAKE HURON. THEREFORE, CONTINUED THE TREND FOR A PESSIMISTIC SKY
FORECAST FOR THE OVERNIGHT PERIOD AND CORRESPONDLY BUMPED LOWS UP
ANOTHER COUPLE OF DEGREES. MOST LOCATIONS ARE FORECAST TO SEE LOWS
FALL TO AROUND 40, ALTHOUGH ANY CLEARING - PARTICULARLY IN THE
SAGINAW BAY AREA, COULD ALLOW TEMPERATURES TO DROP OFF SEVERAL MORE
DEGREES BEFORE CLOUDS POTENTIALLY FILL BACK IN.

&&

.LONG TERM...WEDNESDAY THROUGH MONDAY

THE FORECAST FOR WEDNESDAY WILL BE PREDICATED ON THE MOVEMENT OF THE
WESTERN BACK EDGE OF THE UPPER LEVEL CLOSED LOW OVER THE EASTERN
UNITED STATES. MODEL DATA KEEPS THE UPPER LEVEL CURVED JET CORE OVER
THE FAR EASTERN PORTION OF THE CWA THROUGH MIDDAY BEFORE
RELINQUISHING CONTROL. IT IS WITHIN THIS TIGHT CYCLONIC FLOW THAT
LOW LEVEL COLD AIR ADVECTION AT ROUGHLY 3-4 KFT AGL WILL SUPPORT
CONTINUED STEEP LAPSE RATES...SATURATION...AND STRATUS. WAS VERY
AGGRESSIVE IN KEEPING CLOUDS IN THROUGH 18Z. WHAT IS KNOWN IS THERE
IS A HIGH SIGNAL FOR VERY STRONG UPPER LEVEL CONFLUENCE AND DEEP
COLUMN SUBSIDENCE IMMEDIATELY ON THE PERIPHERY OF THE CLOSED LOW
CIRCULATION. THERE IS A MATCHING SURFACE REFLECTION OF HIGH
PRESSURE. THE UNCERTAIN PORTION IS WHERE EXACTLY THE WEST EDGE OF
THE CLOUD FIELD WILL BE TO START THE DAY. WITH 850MB RH BEING A GOOD
PROXY TODAY FOR THE WESTERN EDGE OF THE
STRATUS/STRATOCUMULUS....USED THAT IDEA FOR WED AFTERNOON. AS A
RESULT...WENT AGGRESSIVE WITH CLEARING FOR THE AFTERNOON HOURS.
TEMPERATURES WEDNESDAY WILL AGAIN BE COOL...RUNNING 5 DEGREES BELOW
AVERAGE.

WEDNESDAY NIGHT...THE ELONGATED SURFACE HIGH PRESSURE CENTER WILL
SLIDE OVER LOWER MICHIGAN LEADING TO LIGHT WINDS. CLEAR SKIES AND
COOLEST OF NEAR SURFACE AIR IN PLACE WILL ALSO LEAD TO FAVORABLE
RADIATING CONDITIONS AND A LOW FLOOR POTENTIAL FOR MIN TEMPERATURES.
FOLLOWED THE AGGRESSIVE THEME HERE AGAIN AND LOWERED LOWS FOR
THURSDAY MORNING. FOR AREAS OUTSIDE OF THE METRO...WENT 20S TO NEAR
30.

THURSDAY...SOUTHEASTERN MICHIGAN WILL REMAIN WITHIN THE PINCHPOINT
OF TWO UPPER LEVEL PV ANOMALIES WHICH PLACES THE CWA UNDER A
WEAKENING SURFACE RIDGE. QUIET WEATHER...SUNNY SKIES...AND A
MODERATING AIRMASS WILL LEAD TO BEAUTIFUL AUTUMN WEATHER.

SOME UNCERTAINTY REMAINS WITH UPPER ENERGY CURRENTLY OVER IDAHO AS
IT ENTERS OUR AREA THURSDAY NIGHT/FRIDAY. FOR EXAMPLE...12Z GFS
SHOWS THE ENERGY GETTING STRUNG OUT OVER THE WESTERN GREAT
LAKES...WHILE THE 12Z ECMWF STRENGTHENS IT A BIT AS IT SLINGSHOTS
AROUND THE BROADER UPPER CIRCULATION OVER THE NEW ENGLAND COAST.
REGARDLESS...MOISTURE WILL BE AT A PREMIUM AND BEST FORCING FOR
ASCENT APPEARS TO STAY TO OUR SOUTH/WEST SO HAVE KEPS FRIDAY DRY.
DRY AND SEASONABLE THIS WEEKEND WITH A WEAK DRY FRONTAL PASSAGE
SATURDAY NIGHT KNOCKING TEMPS DOWN AROUND 5 DEGREES SUNDAY...THOUGH
STILL AROUND SEASONAL NORMALS. MORE SUBSTANTIAL WARMUP IS POSSIBLE
EARLY NEXT WEEK AS UPPER HEIGHTS BUILD AHEAD OF PROGRESSIVE LONGWAVE
TROUGH OVER THE WESTERN CONUS. THIS ENERGY LOOKS TO PROVIDE THE NEXT
MEANINGFUL PRECIP CHANCES OVER THE AREA SOMETIME IN THE MONDAY
NIGHT/TUESDAY TIMEFRAME. LOW CHANCE POPS TO ACCOUNT FOR NORMAL
TIMING UNCERTAINTY.

&&

.MARINE...SHORELINE CONVERGENCE IS ADDING LOCAL EFFECTS TO THE
STRONG NORTHERLY WINDS IMPACTING THE SHORE ALONG SOUTHERN BASIN OF
LAKE HURON. FORT GRATIOT OBSERVATIONS HAVE SHOWN A SHORT DURATION OF
GALE FORCE WINDS THIS AFTERNOON. SUSPECT THERE IS NOT WIDESPREAD
GALE CRITERIA BEING REACHING GIVEN THE FACT THIS IS AN ELEVATED
SITING. WILL NOT BE MAKING ANY CHANGES TO THE HEADLINES FOR THE
NEARSHORE WATERS OF LAKE HURON INCLUDING SAGINAW BAY. PER LATEST
SURFACE OBSERVATIONS...DID INCLUDE SMALL CRAFT ADVISORIES FOR LAKE
ST CLAIR AND THE MICHIGAN WATERS OF LAKE ERIE THROUGH THIS EVENING.
WINDS AND LARGE WAVES WILL GRADUALLY DECREASE OVERNIGHT AS LOW
PRESSURE OVER THE EASTERN GREAT LAKES TRACKS EAST AND A RIDGE OF
HIGH PRESSURE BUILDS INTO THE WESTERN GREAT LAKES. THIS HIGH WILL
REMAIN OVERHEAD DURING THE MID-WEEK PERIOD...ALLOWING FOR CALMER
CONDITIONS.

FURTHER TO THE SOUTH...SLIGHTLY LOWER WIND SPEEDS ARE EXPECTED OVER
LAKE ST CLAIR AND FAR WESTERN LAKE ERIE TODAY...WITH GUSTS EXPECTED
TO TOP OUT BELOW 25 KNOTS.

&&

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

LAKE HURON...
     SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT
     HURON INCLUDING OUTER SAGINAW BAY...UNTIL 6 AM WEDNESDAY.

     SMALL CRAFT ADVISORY...INNER SAGINAW BAY...UNTIL 10 PM TUESDAY.

LAKE ST CLAIR...
     SMALL CRAFT ADVISORY...UNTIL 10 PM TUESDAY.

MI WATERS OF LAKE ERIE...
     SMALL CRAFT ADVISORY...UNTIL 10 PM TUESDAY.

&&

$$

AVIATION.....SC
SHORT TERM...JVC
LONG TERM....CB/DT
MARINE.......CB


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.