FXUS63 KAPX 040940
AFDAPX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
440 AM EST FRI DEC 4 2009
.SYNOPSIS.../ISSUED AT 440 AM/
COLD CANADIAN AIR WILL CONTINUE TO FLOW ACROSS THE GREAT LAKES
THROUGH THIS WEEKEND. THIS WILL RESULT IN PERIODS OF SNOW SHOWERS
AND FLURRIES...WHICH WILL BE MOST NUMEROUS OVER THE SNOW BELTS. THE
HIGHEST SNOWFALL ACCUMULATIONS ARE EXPECTED OVER THE TIP OF THE MITT
INTO THE SOUTHEASTERN U.P. A COLD FRONT WILL MOVE INTO REGION SUNDAY
AND BECOME STATIONARY. A STRONG LOW PRESSURE SYSTEM IS FORECAST TO
DEVELOP ALONG THE FRONT AND MOVE INTO THE GREAT LAKES AROUND THE
MIDDLE OF NEXT WEEK. THIS SYSTEM COULD BRING ADDITIONAL SNOW TO PART
OF THE REGION...WITH ADDITIONAL LAKE EFFECT IN ITS WAKE.
JH
&&
.SHORT TERM.../ISSUED AT 440 AM/...TODAY
LARGE SCALE TROUGH IN THE PROCESS OF AMPLIFYING OVER THE PLAINS/
GREAT LAKES THIS MORNING...DUMPING A SHOT OF MUCH COLDER AIR TO THE
REGION. SFC TROUGH AXIS EXTENDS FROM NW LOWER MICHIGAN INTO SRN
WISCONSIN. AND AIDED BY A SHEARED VORTICITY CENTER LIFTING NE
THROUGH THE REGION AND GREAT LAKE EFFECT PARAMETERS (INVERSION
HEIGHTS GOING THROUGH THE ROOF/H8 TEMPS HEADING TOWARD -12C)...HAS
RESULTED IN SOMEWHAT DISORGANIZED BUT INTENSE MULTI-CELLULAR LAKE
CONVECTION MOVING THROUGH NW LOWER MICHIGAN OVERNIGHT. AS NOTED BY
EVENING FORECASTERS...INTERESTING TO NOTE THAT CONVECTION IS
SUFFICIENTLY DEEP AS TO FOLLOW MORE ALONG THE 850-700 MB MEAN WIND
OVERNIGHT TAKING A SW-NE PATH...ALTHOUGH LOW LEVEL MEAN WINDS ARE
STILL NW-W. MEANWHILE...ANOTHER ROUND OF BKN SYNOPTIC SNOWFALL HAS
DEVELOPED OVER THE REST OF NRN LOWER MICHIGAN ALONG THE TRACK OF THE
SHEAR AXIS MOVING THROUGH.
MAIN FORECAST FOCUS WILL BE SQUARELY IN THE SHORT TERM...AND HOW TO
PROCEED WITH INHERITED HEADLINES GIVEN WHAT HAS/IS OCCURRING SO FAR.
TODAY...SFC TROUGH AXIS AND MID LEVEL SHEAR AXIS EXPECTED TO SLIP
THROUGH THE REGION BY THIS MORNING. OUTSIDE OF THE LAKE EFFECT...
LIGHT SYNOPTIC PRECIP SHOULD MORE OR LESS END BY MID MORNING.
MEANWHILE...A BIT MORE UNIFORM WIND PROFILE IS ANTICIPATED AS THE
MIXED LAYER FURTHER STEEPENS...WITH WSW MEAN FLOW FORECAST BY MID
MORNING THEN BACKING TOWARD SW BY EVENING. THIS SHOULD RESULT IN
MORE DEFINITIVE LAKE EFFECT BANDING DEVELOPING THIS MORNING AND
IMPACTING NW LOWER MICHIGAN...MAINLY NORTH OF M-32 INTO THE STRAITS.
IN TERMS OF ACCUMULATIONS TODAY: LAKE EFFECT PARAMETERS ARE PRETTY
RESPECTABLE THROUGHOUT THE DAY (HIGH INVERSION HEIGHTS/LAKE DELTA
T/S APPROACHING 20C)...ALTHOUGH GUIDANCE DOES SUGGEST NEUTRAL QG
FORCING DEVELOPING AND PERHAPS SOME THINNING OF SYNOPTIC MOISTURE
THIS AFTERNOON. DIURNAL HEATING CYCLE MAY ALSO PLAY SOME ROLE IN
DISRUPTING CONVECTION ALTHOUGH THAT MAY BE MINIMAL GIVING WE ARE
JUST A FEW WEEKS FROM THE LOWEST SUN ANGLE OF THE YEAR.
REGARDLESS...AND ALTHOUGH THERE MAY BE SOME LULLS IN THE SNOWFALL
TODAY...THINK A GOOD 3 TO 5 INCHES OF ACCUMULATION ARE EASILY
ATTAINABLE IN THE MOST FAVORED AREAS ON TOP OF THE ALREADY 2 TO 4
INCHES ACHIEVED LAST NIGHT. AND GIVEN WHAT IS ANTICIPATED TONIGHT
(SEE BELOW)...PROBABLY MAKES THE MOST SENSE TO GO AHEAD AN
HOIST/EXTEND LAKE EFFECT SNOW HEADLINES FOR A CHUNK OF NW LOWER
MICHIGAN NORTH OF M-72. EASTERN UPPER MICHIGAN IS A BIT TRICKY IN
THAT HEAVY SNOW ACCUMULATIONS WILL PROBABLY IMPACT A RELATIVELY
SMALLER PART OF THESE COUNTIES. NONETHELESS...PLAN TO PLACE MACKINAC
COUNTY INTO A WARNING SINCE THE MAIN POPULATION AREA OF THAT COUNTY
WILL BE IMPACTED. ADVISORY FOR CHIPPEWA COUNTY CONCEDING THAT SOME
SPOTS IN THE SE PART OF THAT COUNTY COULD EASILY HIT WARNING
CRITERIA.
ADAM
&&
.LONG TERM.../ISSUED AT 440 AM/...TONIGHT AND BEYOND
TONIGHT THROUGH SATURDAY...MODEL GUIDANCE REMAINS FAIRLY STEADFAST
WITH LOCKING IN RESPECTABLE SW FLOW LES CONDITIONS TONIGHT...MAXIMIZING
LATE TONIGHT THROUGH THE DAY SATURDAY AS ANOTHER LOBE OF SHORT WAVE
ENERGY ROTATES DOWN THROUGH NRN MICHIGAN BRINGING A BOOST TO THE
LES. HIGH (OR NON-EXISTENT) INVERSION HEIGHTS/LAKE-H8 DELTA T/S NEAR
20C/STRONG LOW LEVEL CONVERGENCE SIGNAL SETTING UP ACROSS NRN LAKE
MICHIGAN THROUGH THE STRAITS ALL SUPPORT HEAVY SNOW ACCUMULATIONS
TARGETING THE TIP OF THE MITT/STRAITS AREA WITH AMOUNTS TOTALING
GREATER THAN 12 INCHES POSSIBLE. A GRADUAL BACKING OF THE MEAN FLOW
FROM WSW TO SW THROUGH SATURDAY MAY ACT TO SPREAD ACCUMULATIONS OUT
JUST A BIT. BUT GIVEN THIS SETUP AND EXPECTED ACCUMULATIONS...PLAN
TO RUN ASSOCIATED WARNINGS/ADVISORIES THROUGH THE DAY SATURDAY.
SATURDAY NIGHT INTO SUNDAY...MAKING ONLY MINOR CHANGES TO THE GOING
FORECAST AT THIS JUNCTURE...GIVEN EVERYTHING THAT IS OCCURRING IN
THE SHORT TERM. BUT ONE POINT TO MENTION...LATEST GUIDANCE SUGGESTS
VIGOROUS SW FLOW LAKE EFFECT MAY CONTINUE THROUGH MUCH OF SATURDAY
NIGHT...POSSIBLY INTENSIFY AS ANOTHER TROUGH AXIS SLIPS DOWN THROUGH
NRN MICHIGAN BEFORE GETTING SHUNTED SOUTH INTO NRN LOWER MICHIGAN.
VERY POSSIBLE THAT WARNINGS/ADVISORIES WILL STILL BE NEEDED THROUGH
AT LEAST SATURDAY NIGHT BEFORE THINGS BEGIN TO WIND DOWN ON SUNDAY.
IF THIS WORKS OUT AS WELL AS IT LOOKS ON PAPER SOME SPOTS IN THE TIP
OF THE MITT/EASTERN UPPER MICHIGAN MAY BE DEALING WITH ONE TO TWO
FEET OF SNOW BY SUNDAY. WELCOME TO WINTER.
ADAM
&&
.MARINE.../ISSUED AT 440 AM/
INCREASING SOUTHWEST WINDS WILL BRING A PERIOD OF SMALL CRAFT
CONDITIONS TO THE NEARSHORE AREAS OF NORTHERN LAKE MICHIGAN AND LAKE
HURON. WINDS AND WAVE WILL GRADUALLY SUBSIDE SATURDAY NIGHT INTO
SUNDAY.
ADAM
&&
.AVIATION.../ISSUED AT 1201 AM/...VALID FOR 06Z TAFS
LAKE EFFECT SNOW SHOWERS WILL IMPACT ALL 3 TAF SITES OVER THE NEXT
24 HOURS. THE LONGEST PERIOD OF REDUCED VISIBILITIES WILL BE AT
KPLN...WHILE KTVC WILL EXPERIENCE SOME RESTRICTIONS OVER THE NEXT 3
TO 4 HOURS. KAPN WILL REMAIN UNTOUCHED THROUGH THE OVERNIGHT HOURS
AND REMAIN VFR. AFTER DAYBREAK...SNOW SHOWERS WILL BECOME MORE
CELLULAR AND WILL MOVE IN AND OUT OF THE TAF SITES THROUGH THE
DAYLIGHT HOURS. THUS...EXPECT CONDITIONS TO FLUCTUATE BETWEEN VFR
AND MVFR THROUGH THE DAYLIGHT HOURS (ALTHOUGH MORE MVFR CONDITIONS
ARE EXPECTED AT KPLN).
KAS
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...LAKE EFFECT SNOW WARNING UNTIL 6 PM EST SATURDAY FOR MIZ015>017-
019.
LAKE EFFECT SNOW ADVISORY UNTIL 6 PM EST SATURDAY FOR MIZ008-020-
021.
LM...SMALL CRAFT ADVISORY UNTIL 5 AM EST SATURDAY FOR LMZ323-341-342-
344>346.
LH...SMALL CRAFT ADVISORY UNTIL 5 AM EST SATURDAY FOR LHZ345>349.
LS...NONE.
&&
$$
