FXUS63 KAPX 031524
AFDAPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
1024 AM EST THU DEC 3 2009
.SYNOPSIS.../ISSUED AT 423 AM/
A STORM SYSTEM THAT ORIGINATED OVER THE GULF TUESDAY...WILL LIFT
NORTH ALONG THE ATLANTIC COAST TONIGHT AND THURSDAY...BEFORE
ROTATING BACK INTO QUEBEC FRIDAY.
SNOW SHOWERS WILL BECOME DOMINATE OVER THE NORTHERN GREAT LAKES...
THURSDAY THROUGH THE WEEKEND...IN RESPONSE TO COLDER AIR FILTERING
INTO THE STATE...ON THE BACK SIDE OF THE ATLANTIC STORM SYSTEM.
ADAM
&&
.SHORT TERM.../ISSUED AT 1024 AM/...THIS AFTERNOON
NOT A WHOLE LOT TO UPDATE THIS MORNING...WITH GOING FCST HEADED IN
THE RIGHT DIRECTION. MAIN ISSUE IS OBVIOUSLY CENTERED ON SNOW THRU
THE AFTN HOURS (BOTH SYNOPTIC AND DEVELOPING LAKE EFFECT). LEAD
NORTHERN STREAM SHORTWAVE EVIDENT ON WATER VAPOR IMAGERY CROSSING
SOUTHERN LAKE MICHIGAN AT 15Z HELPING PROVIDE A BRIEF BOOST TO
DEFORMATION-DRIVEN SYNOPTIC SNOW SHIELD ACRS MUCH OF THE CWA THIS
MORNING. BRIEF SURGE OF DEEPER MOISTURE/LIFT ALSO HELPING BOOST THE
"FLUFFINESS" OF THE SNOW AS EVIDENT OUT THE WINDOW HERE AT THE
OFFICE...IN LINE WITH 06Z FCST RAOBS SHOWING BRIEF PERIOD OF
MAXIMIZED LIFT THRU THE DGZ. HOWEVER...THIS ALL A FLEETING A FEATURE
THRU THE AFTN AS LOW PRESSURE OVR NEW ENGLAND SCOOTS NORTHEAST AND
UPR SUPPORT/DEEPER MOISTURE ACRS THE CWA WANES BY 18Z. PER LATEST
RADAR IMAGERY...WILL BOOST SNOW AMOUNTS INTERIOR NORTHERN LOWER JUST
A TOUCH...BUT STILL MAINLY AN INCH OR LESS.
FOCUS THEN SHIFTS TO DEVELOPING LAKE EFFECT ISSUE THRU THE AFTN/
EARLY EVENING WITH STRENGTHENING COLD ADVECTION (H85 TEMPS HEADED
TOWARD -11C TO -13C BY 00Z). THAT SAID...LOSS OF DEEPER H85-H7
MOISTURE COUPLED WITH DECENT BUT NOT STELLAR INVERSION HEIGHTS
(5-6KFT) AS WELL AS BACKING WINDS FROM NORTH/NORTHWEST TOWARD MORE
WEST/NORTHWEST 00-03Z TIMEFRAME SUGGEST LAKE CONVECTION WON'T GET
OUT OF HAND...MAINLY AN INCH OR LESS TARGETING PORTIONS OF NORTHWEST
LOWER AND WESTERN CHIPPEWA/MACKINAC COUNTIES. TONIGHT LOOKS LIKE A
DIFFERENT STORY (HENCE THE HOISTED HEADLINE)...BUT WILL TAKE A
CLOSER LOOK AT THAT FOR THE AFTN PACKAGE. TEMPS HAVE ALREADY PEAKED
MOST SPOTS AND WILL BE HEADED SLOWLY DOWNHILL THRU THE AFTN...SAVE
THE FAR SOUTHEAST WHERE READINGS LIKELY TO STEADY OUT FOR A TIME ON
DOWNSLOPE FLOW.
LAWRENCE
&&
.LONG TERM.../ISSUED AT 423 AM/...TONIGHT AND BEYOND
TONIGHT AND FRIDAY...LAKE INDUCED SNOWS TAKE CENTER STAGE THROUGH
THIS PERIOD IN MAINTENANCE OF VERY GOOD OVER-WATER INSTABILITY
REGIME...WITH INCREASING INVERSION LEVELS AND DEEP MOISTURE ROTATING
BACK ACROSS THE LAKES. NAM-WRF BUFKIT ANALYSIS SHOWS EXCELLENT
PARAMETERS FOR LAKE CONVECTION DEVELOPING QUICKLY TONIGHT...
ESPECIALLY ACROSS NORTHERN LAKE MICHIGAN...AS NEXT SHORTWAVE ROTATES
THROUGH...SPIKING EQUILIBRIUM LEVELS TO NEAR 16KFT AND LAKE INDUCED
CAPE PROFILES NEAR 700 J/KG. INITIALLY SOMEWHAT LESS IMPRESSIVE OVER
EASTERN UPPER MICHIGAN AS BEST MID LEVEL DYNAMICS PASS JUST TO THE
SOUTH TONIGHT...BUT STILL APPRECIABLE AS INVERSION LEVELS STEADILY
INCREASE THROUGH THE NIGHT.
OFF LAKE SUPERIOR...LOW LEVEL CONVERGENCE AXIS FOCUSES INTO ALGER
AND LUCE COUNTY THIS EVENING...EVENTUALLY PIVOTING INTO NORTHWEST
CHIPPEWA COUNTY DURING THE EARLY MORNING HOURS. STILL SOME CONCERN
LIGHT WIND FIELDS MAY LEAD TO DRAINAGE FLOW OFF THE ONTARIO PLATEAU
NORTH OF THE SOO...KEEPING FOCUS WEST OF THE FORECAST AREA. IF BANDS
DO PIVOT INTO THE AREA DURING THE EARLY MORNING...WOULD EXPECT 2 TO
3 INCHES NEAR THE POINT...WITH ONLY THE DELAYED TIMING KEEPING
AMOUNTS SUB-ADVISORY. WINDS CONTINUE TO BACK TO MORE WEST SOUTHWEST
FRIDAY AFTERNOON...DRIVEN THE SNOW BANDS INTO ONTARIO. BEFORE THIS
OCCURS...WOULD EXPECT ANOTHER 2 INCHES OR SO DURING THE
MORNING.
OFF LAKE MICHIGAN...MUCH MORE COMPLEX AS ONGOING AFTERNOON LES
QUICKLY INTENSIFIES THIS EVENING. USING STREAMLINE BOUNDARY LAYER
WIND ANALYSIS AND DIVERGENCE FIELDS...APPEARS HEAVIEST SNOWS WILL
PUSH INTO LEELANAU...BENZIE...AND GRAND TRAVERSE COUNTY THIS
EVENING...PUSHING STEADILY INLAND OVERNIGHT. WHILE BACKING WINDS
SHOULD PREVENT GOOD BANDING STRUCTURES...EXPECTED VIGOROUS
CONVECTION AND LONGEVITY OF SNOWS (SHOULD LAST THROUGH AT LEAST
FRIDAY MORNING) JUSTIFIES ISSUANCE OF FIRST WINTER WEATHER ADVISORY
OF THE SEASON FOR SAID COUNTIES...INCLUDING ANTRIM AND KALKASKA.
COULD SEE AMOUNTS APPROACH A HALF A FOOT BY MIDDAY FRIDAY IN THESE
AREAS. CONVERGENCE SIGNATURE WEAKENS LATER TONIGHT AND FRIDAY AS
SNOWS ADVANCE INLAND...SOMEWHAT LIMITING THE ACCUMULATION POTENTIAL.
BY LATER FRIDAY...WINDS GO WSW...TARGETING THE TIP OF THE MITT
COUNTIES FOR THE HEAVIEST SNOWS...ALTHOUGH DIURNAL DISRUPTION SHOULD
PREVENT SIGNIFICANT ACCUMULATIONS.
AWAY FROM THE TRADITIONAL LAKE ZONES...GOOD MOISTURE AND STEEP LOW
LEVEL LAPSE RATES SHOULD ALLOW FOR GOOD SNOW SHOWER COVERAGE
FRIDAY.
FRIDAY NIGHT AND BEYOND...WSW TO SW FLOW LOCKS IN FRIDAY NIGHT
THROUGH AT LEAST SATURDAY...KEEPING THE TIP OF THE MITT AND PARTS OF
SOUTH-EASTERN UPPER MICHIGAN UNDER THE GUN. PARAMETERS REMAIN
STEAD-FAST...WITH HIGH INVERSION LEVELS...ABUNDANT MOISTURE...AND
GOOD OVER-WATER INSTABILITY. COUPLE THIS WITH EXCELLENT FETCH LENGTH
IN SUCH A FLOW...AND HEAVY ACCUMULATIONS CONTINUE TO LOOK LIKELY FOR
THIS AREA. THOUGHT HARD ABOUT ISSUING A WATCH...BUT GIVEN COMPLEXITY
OF INITIAL EVENT TONIGHT AND FRIDAY...WILL DEFER THAT DECISION TO
LATER SHIFTS. OTHERWISE...LIGHTER LAKE SNOWS SHOULD CONTINUE TO
TARGET AREAS ALONG AND WEST OF THE US-131 CORRIDOR. INHERITED GRIDS
ALREADY HAD ALL OF THIS WELL HANDLED...WITH ONLY CHANGE TO BUMP SNOW
AMOUNTS UP SOME IN TIP OF MITT COUNTIES. COOL CONDITIONS AND CHANCES
FOR ADDITIONAL SNOW CONTINUE INTO THE START OF THE NEXT WORK WEEK.
MSB
&&
.MARINE.../ISSUED AT 423 AM/
SMALL CRAFT ADVISORIES WILL CONTINUE ALL NEARSHORE WATERS AS
GUSTY NORTH TO NORTHWEST WINDS SLOWLY SUBSIDE TODAY WITH LOW
PRESSURE PULLING OFF TO THE NORTHEAST. BRIEF BREAK IN THE ACTION
EXPECTED THIS EVENING BEFORE WINDS BECOME GUSTY WEST TO WEST
SOUTHWEST LATE TONIGHT AND FRIDAY. WILL LIKELY NEED ADDITIONAL
ADVISORIES FOR THIS PERIOD.
MSB
&&
.AVIATION.../ISSUED AT 629 AM/...VALID FOR 12Z TAFS
MVFR DOMINATED FORECAST UNDER LOW CLOUD FIELD AS REMNANT
MOISTURE FROM A DEPARTING STORM SYSTEM INTERACTS WITH INCREASINGLY
FAVORABLE LAKE PROCESSES. LINGERING SNOW THIS MORNING WILL TRANSITION
TO LAKE EFFECT SNOW SHOWERS...ESPECIALLY TARGETING KTVC FOR REDUCED
VISIBILITIES. GUSTY NORTH TO NORTHWEST WINDS TODAY WILL DECREASE IN
SPEED AS THEY BACK WESTERLY LATER TONIGHT. SNOW SHOWERS WILL
INCREASE IN INTENSITY THIS EVENING NEAR KTVC...WITH SNOW SHOWERS
MOVING NORTH TOWARDS KPLN LATER TONIGHT.
MSB
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY FROM 7 PM THIS EVENING TO NOON EST
FRIDAY FOR MIZ020-021-025>027.
LM...SMALL CRAFT ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR LMZ323-
341-342-344>346.
LH...SMALL CRAFT ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR
LHZ345>349.
LS...SMALL CRAFT ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR LSZ321-
322.
&&
$$
