FXUS63 KDLH 071024
AFDDLH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DULUTH MN
424 AM CST MON DEC 7 2009
.DISCUSSION...THE BIG STORY OVER THE NEXT FEW DAYS WILL DEFINITELY
BE THE POTENTIAL SNOWSTORM...BUT IN THE NEAR TERM...IT WILL BE
LAKE EFFECT SNOW ALONG THE SOUTH SHORE.
AT 4 AM...A BLANKET OF CLOUDS BROUGHT A BIT WARMER TEMPERATURES
THAN THE PAST FEW NIGHTS. TEMPERATURES WERE GENERALLY IN THE
TEENS. LAKE EFFECT SNOW SHOWERS CONTINUED ALONG THE SOUTH SHORE OF
LAKE SUPERIOR. THE SNOW BANDS WERE A BIT STRONGER EARLIER ACROSS
NORTHERN BAYFIELD COUNTY...AND WOULD NOT BE SURPRISED IF THERE WAS
A FEW INCHES OF ACCUMULATION IN SPOTS. BANDS CONTINUED TO TRY TO
ORGANIZE FURTHER EAST...BUT HAVEN/T BEEN ABLE TO ORGANIZE YET. THE
IRON NUGGET RESTAURANT WEBCAM IN HURLEY WAS SHOWING FAIRLY LIGHT
SNOW OR FLURRIES SO FAR THIS MORNING.
HIGH RES WRF EMS GUIDANCE...AND ESPECIALLY THE RUC13 GUIDANCE HINT
STRONGLY AT DEVELOPING AND STRENGTHENING LOW LEVEL CONVERGENCE
DEVELOPING ACROSS THE SOUTH SHORE TODAY...WITH BANDS OF SNOW
FOCUSING OFF THE TIP OF THE BAYFIELD PENINSULA. THE RUC13 ACTUALLY
BRINGS 0.15 INCH OF LIQUID PRECIPITATION THROUGH NOON. HAVE BUMPED
UP SNOWFALL AMOUNTS AND ISSUED A LAKE EFFECT SNOW ADVISORY FOR THE
GOGEBIC RANGE OF ASHLAND AND IRON COUNTIES. LAKE EFFECT SNOW IS
NOTORIOUSLY TOUGH TO FORECAST...BUT THINK THERE IS SUFFICIENT
POTENTIAL FOR SEVERAL INCHES OF FLUFFY SNOW IN THIS AREA TODAY.
WILL GO FOR 3 TO AS MUCH AS 6 INCHES...WITH THE GREATEST AMOUNTS
EXPECTED FURTHER EAST ON THE HIGHWAY 77 CORRIDOR. WHAT GIVES US
HIGHER CONFIDENCE RIGHT NOW IS THE FACT THAT LAND WINDS ARE
GENERALLY FROM THE SW...WITH WINDS ON THE LAKE FROM THE N.
LAKE EFFECT SNOW SHOULD DIMINISH RAPIDLY TONIGHT...ALONG WITH
DIMINISHING WINDS. THE PREVIOUS FORECAST HAD HIGHLIGHTED THE
POTENTIAL FOR LAKE SWIRL GENERATION...AND THINK THE POTENTIAL IS
CERTAINLY THERE...ESPECIALLY ON THE GFS. THE NAM KEEPS WINDS UP
TOO MUCH...BUT IF THE GFS MANAGES TO WIN OUT...WE COULD SEE A FEW
SWIRLS DUE TO THE BOWL EFFECT ON THE WESTERN TIP OF THE LAKE. WILL
MAINTAIN CHANCE POPS ACROSS ADJACENT SHORELINE ZONES.
TUESDAY IS WHEN THINGS START TO RAMP UP FOR THE POSSIBLE STORM. TO
VARYING DEGREES...THE MODELS START TO SPREAD PRECIPITATION
NORTHWARD DURING THE DAY ON TUESDAY...ESPECIALLY IN THE AFTERNOON.
COULD BE SOME DECENT LAKE EFFECT SNOW SHOWERS...AND WILL HAVE TO
WATCH FOR POSSIBLE ACCUMULATION ALONG THE NORTH SHORE...AS WINDS
BECOME MORE E TO NE ON TUESDAY.
TUESDAY NIGHT THROUGH FRIDAY...MODELS INDICATING THE SURFACE LOW
OF THE EARLY/MID WEEK WINTER STORM WILL TRACK NORTHEAST AND PUSH
TOWARDS THE TIP OF LAKE MICHIGAN AS THE UPPER LOW STRENGTHENS AND
BECOMES NEGATIVELY TILTED. THE SURFACE WILL IN TURN DEEPEN RAPIDLY
TUESDAY NIGHT. WHILE THE MODELS ARE IN GENERAL AGREEMENT WITH THIS
IDEA...SOME SIGNIFICANT DIFFERENCES IN THE LOW TRACK WILL
CERTAINLY AFFECT SNOW TOTALS. THE NAM/SREF ARE THE FURTHEST NORTH
AND EAST AT 12Z WEDS...AND THEY SUPPORT THE HIGHEST QPF OVER THE
CURRENT WATCH AREA. LATEST 12 ECMWF IS SLIGHTLY FURTHER NORTH AND
EAST WITH THE LOW TRACK WITH THE UPCOMING WINTER STORM...BUT IS
LESS GENEROUS WITH QPF ACROSS THE AREA ALONG WITH THE MORE
PROGRESSIVE GEM AND GFS ENSEMBLES. GIVEN THIS UNCERTAINTY AT THIS
TIME FRAME...NO CHANGE TO THE CURRENT HAZARD GRID IS EXPECTED.
HIGHEST CONFIDENCE AT THIS TIME FOR WARNING CRITERIA WILL BE FOR
THE NW WISC COUNTIES.
NO MATTER THE LOW TRACK...INTENSE CYCLOGENESIS WILL OCCUR ON
WEDNESDAY AS THE LOW DEEPENS AND SLOWS DOWN IN RESPONSE TO THE
NEGATIVELY TILTING UPPER TROUGH...AND SIGNIFICANT BLOWING AND
DRIFTING OF THE NEW SNOW WILL BE COMMON AS VERY COLD NW FLOW
ENSUES ON THE BACK SIDE OF THE LOW. THIS WILL KEEP LAKE EFFECT
SNOW SHOWERS POSSIBLE ALONG THE SOUTH SHORE WED/NIGHT...AND THEN
WINDS BECOME BACKED TO THE WEST BY THURSDAY AFTERNOON. THIS WILL
SHIFT THE BEST CONVERGENCE ZONE OVER THE BAYFIELD PENINSULA.
FOR THE REMAINDER OF THE WEEK...THE POLAR VORTEX WILL THEN ROTATE
SOUTH TOWARDS THE INTERNATIONAL BORDER. THIS WILL KEEP CONDITIONS ON
THE COLD SIDE OF NORMAL WITH A SLIGHT CHANCE OF SNOW SHOWERS ALONG
THE BORDERLAND AND ALONG THE SOUTH SHORE.
&&
.AVIATION.../06Z TAF ISSUANCE/
LOW VFR CIGS WILL BE PREDOMINANT ACROSS THE NORTHLAND...THOUGH
COULD TEMPO DROP TO MVFR...ESP ACROSS NRN MN TOWARDS MORNING.
OTW...LIGHT NRLY FLOW WILL CONTINUE...ALONG WITH SOME HIGH AND MID
CLOUDS STREAMING ACROSS CENTRAL MN AND WI.
&&
.POINT TEMPS/POPS...
DLH 20 5 20 8 / 10 20 70 80
INL 17 -6 12 -2 / 10 10 20 30
BRD 20 4 16 6 / 10 10 50 70
HYR 24 7 22 16 / 20 10 60 100
ASX 26 11 23 19 / 30 20 60 100
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
MN...WINTER STORM WATCH FROM TUESDAY AFTERNOON THROUGH LATE WEDNESDAY
NIGHT FOR MNZ012-019>021-037-038.
WI...WINTER STORM WATCH FROM TUESDAY AFTERNOON THROUGH LATE WEDNESDAY
NIGHT FOR WIZ001>004-006>009.
LAKE EFFECT SNOW ADVISORY UNTIL 7 PM CST THIS EVENING FOR WIZ003-
004.
LS...NONE.
&&
$$
DAP/DONOFRIO
