Area Forecast Discussion
Issued by NWS Detroit/Pontiac, MI

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
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 200413
AFDDTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DETROIT/PONTIAC MI
1213 AM EDT MON OCT 20 2014


.AVIATION...

//DISCUSSION...

VFR SKIES WILL CONTINUE TO STEADILY LOWER OVERNIGHT AS A COLD FRONT
MAKES ITS WAY TOWARDS THE AREA FROM THE WEST. LOW VFR/MVFR CEILINGS
ARE ANTICIPATED BY MONDAY MORNING WITH THE STRENGTHENING SOUTHWEST
FLOW...WITH LIGHT SHOWERS DEVELOPING DURING THE DAYTIME HOURS. THESE
SHOWERS ARE EXPECTED TO LAST THROUGH MONDAY AFTERNOON AS THE COLD
FRONT SWEEPS THROUGH THE AREA WITH LIGHT SHOWERS MONDAY EVENING
BEHIND THE COLD FRONT.

//DTW THRESHOLD THREATS...

* HIGH CONFIDENCE IN CEILINGS DROPPING BELOW 5000 FEET TOWARD
  SUNRISE MONDAY AND CONTINUING THROUGH MONDAY NIGHT.

&&

.PREV DISCUSSION...ISSUED 338 PM EDT SUN OCT 19 2014

SHORT TERM...TONIGHT

12Z DTX SOUNDING REVEALED A VERY DRY AIRMASS IN PLACE...AND MUCH OF
THE ISENTROPIC ASSENT (295 K) TONIGHT WILL BE USED UP JUST TO
SATURATE THE ATMOSPHERE. THE 12Z NAM STILL SHOWING 295 K
CONDENSATION PRESSURE DEFICITS ABOVE 10 MB THROUGH 12Z
MONDAY...WHICH DOES NOT GIVE ONE A WHOLE LOT OF CONFIDENCE IN
SHOWERS DEVELOPING. HOWEVER...THE UPPER WAVE/ENERGY IS CARVING
THROUGH THE UPPER MISSISSIPPI RIVER VALLEY THIS AFTERNOON...AND THE
RESPONSE DOWN LOW/RADAR ACTIVITY IS ON THE UPTICK. WITH THE SYSTEM
CONTINUING TO DIG SOUTHEAST AND FURTHER MOISTURE TRANSPORT TAKING
PLACE...HIGHER CHANCE POPS ACROSS THE NORTH HALF OF THE CWA...CLOSE
TO THE PARENT SURFACE LOW...SEEMS APPROPRIATE.

LOW LEVEL WARM ADVECTION THROUGH THE NIGHT (925 MB TEMPS RISING TO 7
C) COUPLED WITH INCREASING/THICKENING CLOUDS AND MODEST SOUTHWEST
WINDS EXPECTED TO HOLD MINS IN THE LOW TO MID 40S...IN LINE WITH
LATEST GUIDANCE. TEMPERATURES WILL PROBABLY BOTTOM OUT THIS EVENING
AND THEN HOLD OR ACTUALLY RISE SLIGHTLY OVERNIGHT.

LONG TERM... MONDAY THROUGH NEXT WEEKEND

THE SYSTEM MOVING OUT OF CENTRAL CANADA TODAY AND INTO THE NORTHERN
GREAT LAKES TONIGHT WILL BE POSITIONED ON GOOD MODEL AGREEMENT ABOUT
OVER THE STRAITS TO START THE DAY MONDAY. SE MICHIGAN WILL BE
SUBJECTED TO MILD SOUTHWEST LOW LEVEL FLOW AND THE MODEST RAIN
PATTERN ASSOCIATED WITH REMAINING WARM ADVECTION THROUGH THE
MORNING. THE BEST RAIN POTENTIAL WILL DEVELOP DURING THE AFTERNOON
AS FORCING TRANSITIONS TO UPPER WAVE DYNAMICS AND INTERACTION OF THE
MOISTURE AXIS WITH THE COLD FRONT. THE LOW LEVEL THETA-E RIDGE WILL
BUILD FULLY OVERHEAD BY 18Z AND CONSIST OF SURFACE DEWPOINT RISING
TO ABOUT 50 F AND 850 MB DEWPOINT NEAR 5 C. SURFACE BASED
INSTABILITY DEVELOPS MORE CONVINCINGLY OVER OHIO AND ONTARIO IN THE
NAM OUTPUT BUT ELEVATED INSTABILITY WILL BE ADEQUATE TO MAINTAIN THE
ISOLATED MENTION OF THUNDER ADVERTISED IN THE FORECAST OVER THE LAST
FEW FORECAST CYCLES. LAPSE RATES IN THE 700-500 MB LAYER ARE SHOWN
IN MODEL DATA TO STEEPEN NEAR 7.5 C/KM AS THE UPPER LEVEL COLD POOL
ADVECTS INTO THE REGION WITH 500 MB TEMPS APPROACHING -23 C. MODEL
THETA-E CROSS SECTIONS ALSO INDICATE ELEVATED INSTABILITY
COMMENSURATE WITH 850 MB LI AROUND -1 C WHICH...WHEN COMBINED WITH
DCVA FROM THE UPPER WAVE AND FRONTAL CONVERGENCE...WILL RESULT IN
NUMEROUS SHOWERS ALONG WITH THE ISOLATED STORM POSSIBILITY.

AFTER A PAUSE IMMEDIATELY POST FRONT...EXPECT SOME MOISTURE TO WRAP
AROUND THE WAVE AND LINGER OVER SE MICHIGAN DURING MONDAY EVENING...
BUT ESPECIALLY OVERNIGHT. THIS IS WHEN STRONG CYCLONIC FLOW WILL
DEVELOP A NORTHEAST COMPONENT AND WRING OUT ADDED MOISTURE FROM LAKE
HURON. MODEL SOUNDINGS AND PLAN VIEW TEMPERATURE FIELDS INDICATE
SATURATION THROUGHOUT THE LOW LEVEL THERMAL TROUGH WHICH POINTS TO
DEVELOPING LAKE INSTABILITY HAVING POTENTIAL FOR DEEP INLAND
PROGRESS AND FOR SHOWERS TO HAVE ENOUGH LONGEVITY TO CARRY WELL INTO
TUESDAY MORNING. COLD ADVECTION WILL THEN CONTINUE THROUGH TUESDAY
INTO TUESDAY NIGHT BUT WILL BECOME PROHIBITIVELY DRY FOR
PRECIPITATION AS LOW LEVEL FLOW RELAXES AND THE INFLUENCE OF HIGH
PRESSURE TAKES OVER. THE PACE OF THIS TRANSITION LOOKS SOLID IN THE
LARGER SCALE MODEL PRESSURE AND LAYER MOISTURE FIELDS ACROSS
SOLUTIONS...BUT THE PACE OF BOUNDARY LAYER DRYING SUGGESTS A SLOWER
CLEARING TREND TOWARD WEDNESDAY MORNING.

WEDNESDAY AND BEYOND WILL FEATURE A TRANSITION TO UPPER RIDGING
BUILDING INTO THE GREAT LAKES REGION IN THE WAKE OF THE UPPER LOW
MOVING TOWARD THE MID-ATLANTIC COAST. WEDNESDAY WILL STILL FEATURE
COOL TEMPERATURES WITH LOW LEVEL FLOW REMAINING NORTHERLY THROUGH
MOST OF THE DAY AS IT WILL TAKE A WHILE FOR THE THERMAL TROUGH TO
DEPART AND SURFACE HIGH TO BUILD IN. CALLED FOR A SLOWER BURNOFF OF
CLOUDS AND HIGHS IN THE LOW 50S. AFTER A CHILLY WEDNESDAY NIGHT...A
NICE WARMING TREND AND PLEASANT FALL WEATHER IS IN STORE THURSDAY INTO THE
WEEKEND WITH HIGHS LIKELY REACHING BACK INTO THE 60S BY FRIDAY. ONE
THING TO WATCH WILL BE THE SHORTWAVE TROUGH APPROACHING THE REGION
FROM THE PLAINS THURSDAY NIGHT...BUT MODEL CONSENSUS SUPPORTS THIS
WAVE SHEARING OUT WITH MINIMAL IMPACT TO WEATHER LOCALLY SAVE FOR
PERHAPS AN INCREASE IN MIDLEVEL CLOUDS.

MARINE...

SOUTHWEST WIND WILL STEADILY INCREASE DURING THE NIGHT AS THE NEXT
LOW PRESSURE SYSTEM MOVES FROM NORTHWEST ONTARIO TO THE STRAITS BY
MONDAY MORNING. THE LOW AND ASSOCIATED COLD FRONT WILL PASS ACROSS
LAKE HURON AND LOWER MICHIGAN DURING THE DAY WITH A PATTERN OF
SHOWERS LASTING THROUGH MONDAY NIGHT. WINDS WILL THEN VEER TO
NORTHEAST AS THE LOW PRESSURE SYSTEM CONTINUES TO MOVE TOWARD THE
ATLANTIC COAST AND AS HIGH PRESSURE BUILDS ACROSS NORTHERN ONTARIO.
THE COMBINATION OF A STRONGER GRADIENT AND ONSHORE FLOW WILL BRING A
PERIOD OF GUSTY WIND AND BUILDING WAVES THROUGHOUT CENTRAL AND
SOUTHERN LAKE HURON THROUGH TUESDAY. THE POTENTIAL FOR GUSTS AROUND
30 KNOTS LOOKS SOLID WITH A LOWER PROBABILITY FOR BRIEF GUSTS TO
GALES EARLY TUESDAY. THE COLDER AIR OVER THE WARM LAKE WATER WILL
YIELD STRONG INSTABILITY BUT MAY ALSO LIMIT THE POTENTIAL FOR GALE
FORCE GUSTS BY ALTERING THE PRESSURE FIELD AND LIMITING THE GRADIENT
FLOW. NO GALE HEADLINES ARE PLANNED AT THIS TIME BUT SMALL CRAFT
ADVISORIES WILL LIKELY BE NEEDED TUESDAY INTO TUESDAY NIGHT.

&&

.DTX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LAKE HURON...NONE.
LAKE ST CLAIR...NONE.
MI WATERS OF LAKE ERIE...NONE.

&&

$$

AVIATION.....KURIMSKI
SHORT TERM...SF
LONG TERM....BT/DT
MARINE.......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.