FXUS63 KAPX 050159
AFDAPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
859 PM EST THU DEC 4 2008
.SYNOPSIS.../ISSUED AT 357 PM/
AN ALBERTA CLIPPER WILL DROP ACROSS THE WESTERN GREAT LAKES
SATURDAY...RESULTING IN A TRANSITION FROM LAKE EFFECT TO MORE
WIDESPREAD SNOWFALL FRIDAY NIGHT INTO SATURDAY...WITH LOCALLY
HEAVIER AMOUNTS IN SOUTHWEST FLOW OFF LAKE MICHIGAN. A FRESH SHOT
OF COLD AIR WILL MOVE IN BEHIND THE SYSTEM FOR SUNDAY...KEEPING THE
THREAT FOR SNOW SHOWERS GOING IN AREAS FAVORED BY MAINLY NORTHERLY
FLOW.
JPB
&&
.SHORT TERM.../ISSUED AT 900 PM/...TONIGHT
AFTER WAITING A BIT...PERSISTENT LAKE EFFECT SNOW BANDS HAVE SET UP
OVER NORTHWEST LOWER MICHIGAN AS NORTHWEST FLOW CONTINUES. THREE
TO FOUR GOOD BANDS SETTING UYP BETWEEN HARBOR SPRINGS AND
KALKASKA. APX UPPER AIR SOUNDING THIS EVENING SHOWS INVERSION
HEIGHTS AROUND 6000 FEET ASL... WHICH SHOULD CONTINUE TO SUPPORT
MODERATE SNOW. MODEL SOUNDINGS SHOW LOWERING INVESION HEIGHTS OVERNIGHT
WHICH SHOULD DIMINISH THE SNOWFALL RATES THROUGHOUT THE NIGHT.
MEAN 925 TO 800 MB WINDS SLIGHTLY BACK TO WEST OVERNIGHT WHICH
SHOULD SHIFT THE BANDING MORE TO THE NORTH. CURRENTLY...FORECAST
WARNINGS APPEAR TO BE ON TRACK.
IN THE UPPER PENINSULA...CANADIAN RADAR SHOWS BANKS VEERING FROM
NORTH TO NORTHWEST OVER THE EVENING. ONE PRIMARY BAND HITTING
WHITEFISH POINT AREAS AND INTO THE CITY OF SAULT STE MARIE. WITH
SLIGHT BACKING OF WINDS OVERNIGHT...LAKE BAND MAY TO PUSH OFF
SHORE DIMINISHING THE ACCUMULATIONS...BUT NOT CONFIDENT TO ALTER
ANY HEADLINES AT THIS TIME.
LITTLE CHANGE TO OVERNIGHTS FORECAST. TEMPS ON TRACK TO BE
SLIGHTLY COLDER... SO HAVE ADJUSTED ONGOING FORECAST.
CAMPBELL
&&
.LONG TERM.../ISSUED AT 357 PM/...FRIDAY AND BEYOND
FRIDAY...WESTERLY FLOW LAKE EFFECT WILL BE ONGOING FRIDAY MORNING...
WITH WINDS EXPECTED TO BACK SOUTHWEST AS CLIPPER LOW MOVES INTO THE
UPPER MIDWEST. SHIFTING SNOW BANDS AND LOWERING INVERSION HEIGHTS
ALONG WITH SOME DRYING SHOULD LIMIT POTENTIAL ACCUMULATIONS...
HEAVIEST PROBABLY IN THE STRAITS/TIP OF THE MITT WERE 2-3 INCHES MAY
OCCUR. FORCING AND DEEPER MOISTURE WILL SPREAD ACROSS THE FORECAST
AREA FROM THE NORTHWEST FRIDAY NIGHT...SYNOPTIC AMOUNTS SHOULD
GENERALLY BE ON THE LIGHT SIDE (1-3 INCHES)...BUT SOUTHWEST FLOW
ENHANCEMENT EXPECTED TO INCREASE SNOW INTENSITY OVERNIGHT AROUND THE
STRAITS AND DOWN TOWARD GRAND TRAVERSE BAY. INVERSION HEIGHTS CLIMB
TOWARD 700MB BY SATURDAY MORNING...ALONG WITH STRONG LOW LEVEL
CONVERGENCE WHICH SHOULD RESULT IN A BAND OF HEAVY SNOW DEVELOPING
OVER FAR NORTHERN LAKE MICHIGAN.
SATURDAY...PERIODS OF SNOW WILL CONTINUE SATURDAY AS SURFACE LOW
CROSSES THE STATE...INITIAL MID LEVEL WAVE FORECAST TO BYPASS LOWER
MI BUT A SECONDARY PIECE OF ENERGY DROPS IN DURING THE AFTERNOON.
THIS SECOND WAVE HAS SOME FOCUSED F-GEN FORCING TO HELP THINGS ALONG
AS WELL. BAND OF HEAVY SNOW EXPECTED ALONG THE LAKE MICHIGAN
SHORELINE AND INTO THE STRAITS AREA SATURDAY MORNING...SHOULD PUSH
INLAND AS THE SURFACE FRONT ADVANCES EAST...AND MAY BRING A COUPLE
HOUR PERIOD OF MORE INTENSE SNOWFALL TO MUCH OF NORTHERN LOWER.
WILL PROBABLY NEED ANOTHER ROUND OF WATCHES/WARNINGS AT LEAST ALONG
THE NORTHWEST LOWER SHORELINE INTO MACKINAC COUNTY FOR FRIDAY
NIGHT/SATURDAY...BUT WILL LET THE INITIAL LAKE EFFECT EVENT CLEAR
OUT FIRST SINCE "HEADLINE WEARINESS" SEEMS TO BE SETTING IN.
FOR SATURDAY NIGHT...NORTHWEST FLOW SETS UP AS CLIPPER PASSES BY TO
THE EAST...WITH 850MB TEMPERATURES DROPPING ONCE AGAIN THIS TIME
CLOSER TO -20C. INVERSION HEIGHTS START OUT HIGH AND DROP OFF
OVERNIGHT...AND MID LEVELS DRY OUT...BUT SEVERAL MORE INCHES OF SNOW
POSSIBLE IN FAVORED NORTHWEST FLOW AREAS EXPECTED.
EXTENDED RANGE (SUNDAY THROUGH THURSDAY)...LARGE SCALE PATTERN NEXT
WEEK WILL CONTINUE TO FEATURE MEAN LONG WAVE TROUGHING ACROSS
CENTRAL/EASTERN NORTH AMERICA...A FEATURE THAT HAS BEEN SLOWLY
RETROGRADING OVER THE PAST WEEK. LONG RANGE DISPOSITION OF THIS
TROUGH WILL BE COMING INTO QUESTION HEADING INTO MID MONTH...AS
RECENT STABLE FOUR WAVE PATTERN SHOWING SIGNS OF BREAKING DOWN.
WILL BE INTERESTING TO SEE IF THIS LIBERATES THE GREAT LAKES FROM
THE RECENT PERSISTENT COLD/SNOWY WEATHER FOR THE LATTER HALF OF
DECEMBER. JUST SOME FOOD FOR THOUGHT. IN THE MEANTIME...THE
EXTENDED PERIOD STARTS WITH TIGHT CYCLONIC FLOW IN THE WAKE OF
DEPARTING CLIPPER...WITH A NEW PUSH OF COLD AIR (850MB TEMPERATURES
OF -15C TO -20C) OFFSET BY DEEP LAYER DRYING AND WARMING ALOFT
IMPLIED BY RISING HEIGHTS. SO EXPECTING THESE LATTER FACTORS TO PUT
A DAMPER ON SIGNIFICANT SNOWFALL POTENTIAL. THE IDEA OF HIGH
PRESSURE BUILDING INTO THE STATE SUNDAY NIGHT HAS BEEN PERSISTENT IN
THE GUIDANCE...WITH EXPECTED CLEARING INLAND LEADING TO A VERY COLD
NIGHT WITH MANY AREAS EXPECTED TO DROP BELOW ZERO. AS WARM AIR
RETURNS TO THE GREAT LAKES THE REPRIEVE FROM SNOWFALL WILL BE SHORT
LIVED WITH A CHANCE OF MORE WIDESPREAD WARM ADVECTION SNOWS
MONDAY...AND WILL CONTINUE THIS INTO TUESDAY. THE MIDWEEK PERIOD
WILL BECOME MORE INTERESTING WITH A WEAK SPLIT IN THE FLOW
DEVELOPING AS SOME ENERGY DIGS TOWARD THE GULF COAST...WITH MORE
NORTHERN STREAM ENERGY CROSSING THE NORTHERN PLAINS. FOCUS ON THE
MIDWEEK PERIOD HAS BEEN ON WHETHER OR NOT A STORM SYSTEM WOULD SPIN
UP IN ASSOCIATION WITH EITHER OF THESE FEATURES. OPERATIONAL GFS
HAS BEEN WARMING TO THE SPLIT FLOW IDEA AND HAS BEEN TAKING THE
SOUTHERN STREAM ENERGY AND SPINNING UP VARIOUS STORM EVOLUTIONS OVER
THE PAST THREE RUNS...04/00Z RUN WEST OF THE APPALACHIANS...04/12Z
RUN BACK CLOSER TO THE EAST COAST. 24/00Z GGEM DEVELOPS STRONG
SYSTEMS WITH BOTH PIECES OF ENERGY...HITTING THE STATE TUESDAY
(SIMILAR TO ITS IDEA A COUPLE DAYS AGO). GUIDANCE IS GOING TO
STRUGGLE WITH THIS...SO FOR NOW BEST BET IS TO TRY AND KEEP
WEDNESDAY DRY...AND START THURSDAY OUT WITH A CHANCE FOR SNOW.
NEEDLESS TO SAY...TEMPERATURES THROUGH THE PERIOD WILL REMAIN BELOW
NORMAL. SOME MODERATION EXPECTED MONDAY/TUESDAY AS SOUTHERLY WINDS
DEVELOP.
JPB
&&
.MARINE.../ISSUED AT 900 PM/
SMALL CRAFT ADVISORIES WILL CONTINUE OVERNIGHT OVER WFP AND THE
LOWER MICHIGAN SHORELINES AS WINDS ALONG THE COAST GUST TO NEAR 25
KNOTS. WEST TO NORTHWEST WINDS WILL BACK TO THE WEST SOUTHWEST
FRIDAY MORNING.
&&
.AVIATION.../ISSUED AT 626 PM/...VALID FOR 00Z TAFS
LAKE EFFECT SNOW BANDS WILL KEEP ALL SITES UNDER MAINLY MVFR CONDITIONS
OVER THE FORECAST PERIOD. OCCASIONALLY IFR CONDITIONS ARE POSSIBLE
WITH THE HEAVIEST SNOW SHOWERS.
CAMPBELL
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...WINTER WEATHER ADVISORY UNTIL 4 AM EST FRIDAY FOR MIZ023-029-
031>033.
WINTER STORM WARNING UNTIL 4 AM EST FRIDAY FOR MIZ016-017-
019>022-025>028.
LAKE EFFECT SNOW WARNING UNTIL 10 AM EST FRIDAY FOR MIZ008.
LM...SMALL CRAFT ADVISORY UNTIL 7 AM EST FRIDAY FOR LMZ323-342-
344>346.
LH...SMALL CRAFT ADVISORY UNTIL 7 AM EST FRIDAY FOR LHZ345-347>349.
LS...SMALL CRAFT ADVISORY UNTIL 7 AM EST FRIDAY FOR LSZ321-322.
&&
$$
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