FXUS63 KAPX 050830
AFDAPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GAYLORD MI
330 AM EST SAT DEC 5 2009

.SYNOPSIS.../ISSUED AT 330 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 WEAK LOW PRESSURE SYSTEM IS FORECAST TO 
TRACK ALONG THIS FRONT MONDAY. THIS SYSTEM WILL BRING ADDITIONAL 
MINOR ACCUMULATIONS TO THE REGION.

JH

&&

.SHORT TERM.../ISSUED AT 330 AM/...TODAY

PERSISTENT SW FLOW LAKE ENHANCED SNOW EVENT CONTINUES...WITH HIGH 
PRESSURE CENTERED SOUTH OF MICHIGAN AND DEEP TROUGHING NORTH OF OUR 
STATE. HEAVIEST SNOW BANDS CONTINUE TO TARGET FAR SE SECTIONS OF 
MACKINAC AND CHIPPEWA COUNTIES AS WELL AS EMMET...CHARLEVOIX AND 
CHEBOYGAN COUNTIES...ALL OF WHICH REMAIN UNDER A LAKE EFFECT SNOW 
WARNING THRU EARLY EVENING. THE NRN TIP OF LEELANAU COUNTY REMAINS 
UNDER A PERSISTENT LAKE BAND...BUT SURROUNDING WATERS SEEM TO BE 
HAVING AN EFFECT ON SNOW CONSISTENCY AND THUS AMOUNTS...LENDING TO A 
WETTER SNOW THAT DOES NOT STACK UP AS QUICKLY. SCT/NMRS SNOW SHOWERS 
CONTINUE TO IMPACT THE HIGHER TERRAIN REGIONS OF NRN LWR MICHIGAN... 
ESPECIALLY KALKASKA AND OTSEGO COUNTIES. THESE TWO COUNTIES...ALONG 
WITH LEELANAU COUNTY REMAIN IN AN ADVISORY THRU EARLY EVENING. 
LATEST NAM AND GFS ARE IN DESCENT AGREEMENT IN HOLDING ON TO 
PERSISTENT SW LOW LEVEL FLOW THROUGHOUT THE DAY. MODELS DO HINT AT 
SOME MID LEVEL DRYING BRIEFLY TAKING PLACE AROUND MIDDAY...BUT STILL 
EXPECT THERE WILL BE SUFFICIENT MOISTURE AND PLENTY OF OVER-LAKE 
INSTABILITY FOR SNOW SHOWER PRODUCTION TO CONTINUE. HAVE INCREASE 
EXPECTED SNOW AMOUNTS TODAY FOR BOTH THE WARNING AND ADVISORY AREAS. 
HAVE ALSO EXPANDED SCT SHSN TO ERN AND SE SECTIONS OF OUR CWA BASED 
ON LATEST RADAR AND SURFACE OB TRENDS...AND WITH THE EXPECTATION OF 
ONGOING EVENT TO EVOLVE INTO A MORE CELLULAR STRUCTURE AS IS TYPICAL 
DURING THE DAYTIME. 

&&

.LONG TERM.../ISSUED AT 330 AM/...TONIGHT AND BEYOND

SW FLOW EVENT HANGS ON INTO THE EVENING HOURS. SOME UPPER SUPPORT 
ARRIVES FROM THE NORTH AS THE 500 MB TROUGH AXIS DIPS INTO NRN 
MICHIGAN. LOW LEVEL WINDS SHIFT TO THE WEST OVERNIGHT BEHIND THE 
UPPER TROUGH AND ASSOCIATED SHORT WAVE. SHOT OF ENHANCED MID LEVEL 
MOISTURE WILL ARRIVE JUST AHEAD OF THE TROUGH WITHIN AN AREA OF GOOD 
DPVA. OVER-LAKE INSTABILITY REMAINS MORE THAN SUFFICIENT FOR LAKE 
SNOW PRODUCTION...WITH INVERSION HEIGHTS REMAINING AROUND 7-9 KFT. 
HAVE MODIFIED WX/POP AND SNOWFALL AMOUNTS TO ACCOUNT FOR THE WIND 
SHIFT OVERNIGHT...TARGETING WESTERLY FLOW AREAS ALONG AND SOUTH OF 
THE STRAITS FOR BEST SNOWFALL AMOUNTS OF 2 TO 5 INCHES. HAVE ALSO 
INCREASE POPS AND SNOW AMOUNTS FOR THE REST OF OUR CWA...EXPECTING 
THAT MOST AREAS WILL SEE SOME SNOW WITH THE ARRIVAL OF THE SHORT 
WAVE AND ENHANCED MOISTURE. 

RELATIVELY WEAK W/NW LOW LEVEL WINDS...DELTA T'S HOLDING IN THE 
UPPER TEENS AND INVERSION HEIGHTS HOLDING AROUND 7 KFT WILL LEND TO 
ADDITIONAL LAKE EFFECT SNOW SHOWER DEVELOPMENT ON SUNDAY. HIGHEST 
POPS WILL TARGET CHIPPEWA COUNTY...AS WELL AS CHARLEVOIX...ANTRIM 
AND OTSEGO COUNTIES WHERE ANOTHER 1 TO 3 INCHES CAN BE EXPECTED 
THROUGHOUT THE DAY. LIMITATION TO SNOWFALL WILL BE DIMINISHING MID 
LEVEL RH AS THE SHORT WAVE MENTIONED ABOVE DEPARTS. SUNDAY NIGHT 
WILL SERVE AS A TRANSITION PERIOD FROM THE LAKE EFFECT EVENT TO AN 
APPROACHING SYNOPTIC SYSTEM RIDING NE OUT OF THE CENTRAL PLAINS 
TOWARD MICHIGAN. LOW LEVEL WINDS WILL SHIFT FROM THE W/NW TO THE SE 
IN ADVANCE OF THIS SYSTEM. WILL REARRANGE WX/POPS TO ACCOUNT FOR 
THIS WIND SHIFT...AND WITH THE ANTICIPATION OF SOME LAKE HURON 
ENHANCEMENT AS DELTA T'S HOLD IN THE MID TO UPPER TEENS. WILL KEEP A 
CLOSE EYE ON THE EVOLUTION OF THIS SYSTEM OVER TIME AS IT COULD BE 
ANOTHER PRODUCER OF ACCUMULATING LAKE ENHANCED SNOW.

WINTER IS HERE IN FULL FORCE WITH PERSISTENT COLD AND MULTIPLE 
CHANCES FOR ACCUMULATING SNOW.

PATTERN: NAO IS NEGATIVE IS FCST TO REMAIN NEGATIVE THRU MID 
DECEMBER. THIS FAVORS LOCKING IN THE COLD WITH POLAR VORTEX IN 
VICINITY OF ONTARIO-HUDSON BAY. PNA IS CURRENTLY POSITIVE AND BUT 
FCST TO TURN NEG NEXT WEEK...POSSIBLY SUPPORTING RISING HEIGHTS OVR 
THE SERN USA. WITH -NAO...THIS WOULD SUPPORT CONTINUED STORMINESS

TEMPS: SOME PARTS OF THE FA WILL REMAIN BLO FRZG FOR AT LEAST THE 
NEXT 7 DAYS. CANADIAN ENSEMBLE 10-DAY MEAN TEMP ANOMALY IS FCST -2.

MON: WEAK LOW PRESSURE/LOW AMPLITUDE SHRTWV TROF/VORT MAX IS FCST TO 
TRACK THRU SRN LOWER WITH LEFT EXIT REGION DYNAMICS. THIS EVENT 
COULD BE ADVY MATERIAL. PRESENT INDICATIONS ARE THAT BAND OF 
SNOWFALL WILL AFFECT MUCH OF THE FA ALONG AND S OF M-32. NAM SNOW 
ALGORITHM OUTPUTS 2-4 INCHES FM MBL-APN. SNOW RATIOS SHOULD BE 
15-20:1. FROM AVERAGE OF MULTI-MODEL QPF...THIS WOULD SUPPORT 3 TO 5 
INCHES. THE NEW DGZ TOOL IN AWIPS SHOWS MAX UVM IS FCST TO BE 
COLLOCATED WITH THE DGZ. 

MINOR LAKE ENHANCEMENT IN E FLOW OFF LAKE HURON.

COORD WITH GRR/DTX. CONFIDENCE IS ABOVE AVG.

QPF IS 00Z/5 NAM WITH SUPPORT FROM 03Z/SREF.

TEMPS ARE CONTINUITY WITH 4 PM APX FCST.

MON NGT: MINOR LES LIKELY TO CONTINUE IN NW BOUNDARY LAYER FLOW.

LATE TUE-WED: WE'RE STILL LOOKING AT POTENTIAL FOR A MAJOR WINTER 
STORM. DUE TO GEFS AND MULTI-MODEL AGREEMENT/TIGHT-CLUSTERING... 
CONFIDENCE IS HIGH. MUCH REMAINS TO BE DETERMINED. BE AWARE THAT 
SOME ENSEMBLE MEMBERS AND OPERATIONAL MODELS ARE FCSTG AN IDEAL 
TRACK FOR S+ OVER OR NEAR NRN MI. 00Z/4 GFS ENSEMBLES ARE FCSTG LOW 
PRESSURE TO BE -3.5 STANDARD DEVIATIONS. GRUMM AND HART (2001) HAVE 
SHOWN THAT LOWS OF THIS MAGNITUDE HAVE THE POTENTIAL TO PRODUCE 
POTENTIALLY RARE/SIGNIFICANT IMPACTS.

WILL BE WATCHING FOR ENHANCEMENT OFF LAKE HURON.

00Z/5 GFS ENSEMBLE MEAN OF SLP AT 983 MB OVR LAKE HURON AT 120 HRS 
IS IMPRESSIVE.

JH/MR

&&

.MARINE.../ISSUED AT 330 AM/

PLENTY OF OVERLAKE INSTABILITY COUPLED WITH MODEST WIND FIELD ALOFT 
WILL YIELD A CONTINUATION OF SMALL CRAFT ADVISORY CONDITIONS TODAY...
PRIMARILY ON THE LAKE MICHIGAN SIDE WHERE SOUTHWEST FLOW COASTAL 
CONVERGENCE REGIME WILL HELP THINGS OUT. WILL ALSO KEEP THE STRAITS 
OUT TOWARD DETOUR IN THE MIX WITHIN SOUTHWEST FLOW REGIME (SOME 
CHANNELING/ONSHORE FLOW). MORE TRANQUIL CONDITIONS LOOK TO RETURN TO 
ROUND OUT THE WEEKEND.

LAWRENCE/RUNYAN

&&

.AVIATION.../ISSUED AT 1205 AM/...VALID FOR 06Z TAFS

IN SHORT...UGLY CONDITIONS AT PLN...APN LOOKING GOOD...TVC SOMEWHERE 
IN BETWEEN. 

LOW PRESSURE WELL TO OUR NE...HIGH PRESSURE IN THE CENTRAL PLAINS 
AND OHIO VALLEY. IN BETWEEN THESE FEATURES...WSW WINDS WILL PRODUCE 
LAKE EFFECT SNOW TARGETING THE TIP OF NORTHERN MI...INCLUDING PLN... 
THRU THE NIGHT AND INTO SATURDAY. SNOW WILL BE HEAVY AT TIMES...IFR 
CONDITIONS COMMON. TVC SEES LESS VIGOROUS LAKE EFFECT SNOW WITH THAT 
WIND DIRECTION...MVFR/IFR. PRIMARILY VFR AT APN.

JZ

&&

.APX WATCHES/WARNINGS/ADVISORIES...
MI...LAKE EFFECT SNOW WARNING UNTIL 6 PM EST SATURDAY FOR MIZ008-
     015>017-019.
     LAKE EFFECT SNOW ADVISORY UNTIL 6 PM EST SATURDAY FOR           
     MIZ020>022-027.
LM...SMALL CRAFT ADVISORY UNTIL 5 PM EST SATURDAY FOR LMZ323-341-342-
     344>346.
LH...SMALL CRAFT ADVISORY UNTIL 5 PM EST SATURDAY FOR LHZ345-346.
LS...NONE.

&&

$$