FXUS63 KDLH 062201
AFDDLH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DULUTH MN
401 PM CST SUN DEC 6 2009
.SHORT TERM...TONIGHT THROUGH TUESDAY...
COLD AIR REMAINS WELL-ENTRENCHED ACROSS THE REGION THIS
AFTERNOON..WITH N/NW FLOW RESULTING IN THE PERSISTENCE OF LAKE-
EFFECT SNOW SHOWERS OVER THE SOUTH SHORE. CLOUDS WILL CONTINUE TO
INCREASE TONIGHT AS FAST-MOVING LOW AMPLITUDE WAVE SCOOTS EWD FROM
THE FRONT RANGE INTO THE OH VALLEY TONITE. PRECIP FROM THIS SYSTEM
WILL STAY WELL TO OUR SOUTH..BUT IT WILL RESULT IN A SLIGHT
INCREASE IN NRLY LOW LEVEL FLOW LATE TONITE AND MONDAY..WHICH SHUD
ACT TO KEEP SCATTERED LAKE EFFECT SHOWERS GOING INTO MONDAY NIGHT.
OVERALL..RATES WITH THE LAKE EFFECT ARE NOT EXPECTED TO BE
HEAVY..BUT LONG DURATION MAY RESULT IN 2-4 INCH TOTALS BY LATE
MONDAY IN SOME OF THE HIGHER TERRAIN FAVORED AREAS OF THE BAYFIELD
PENINSULA AND GOGEBIC RANGE. OTHERWISE..SCATTERED TO BROKEN
STRATUS AND PERIOD OF FLURRIES EXPECTED TO PERSIST.
THINGS THEN BEGIN TO GET MORE INTERESTING MONDAY NIGHT AND TUESDAY
AS DEEP LAYER MOISTURE INCREASES AND LOW LEVEL FLOW GRADUALLY
TURNS EASTERLY AS STRONG SYSTEM FOR THE TUE-WED TIME FRAME
ORGANIZES AND APPROACHES THE REGION. LIGHT FLOW BUT VERY COLD
TEMPS MONDAY NIGHT MAY RESULT IN THE FORMATION OF LAKE-EFFECT SNOW
WHIRLS ACROSS WRN LAKE SUPERIOR DUE TO THE BOWL SHAPED
SHORELINE/TERRAIN AND LAND BREEZE INTERACTIONS. MOST OF THE MODELS
INDICATE THE POTENTIAL FOR AN ORGANIZED LAKE-EFFECT BAND TO BEGIN
AFFECTING THE NORTH SHORE TUESDAY MORNING. TUESDAY AFTERNOON..WARM
ADVECTION/MOISTURE AND UPWARD MOTION CONTINUE TO INCREASE..AND WE
EXPECT MORE WIDESPREAD LIGHT/MODERATE SNOWS TO GRADUALLY DEVELOP
OVER MUCH OF THE AREA BY TUESDAY EVENING. SINCE THERE APPEARS TO
BE A RISK OF HEAVY LAKE EFFECT SNOW SHOWERS DEVELOPING AS EARLY AS
MIDDAY TUESDAY..WE CHOSE TO START THE WINTER STORM WATCH MIDDAY
TUESDAY..ALTHOUGH THE GREATEST THREAT IN AREAS AWAY FROM THE LAKE
IS NOT EXPECTED TO DEVELOP UNTIL TUESDAY NIGHT.
.LONG TERM...TUESDAY NIGHT THROUGH FRIDAY...
MODELS CONTINUE TO EXHIBIT STRONG CONSENSUS THAT A SIGNIFICANT
CYCLONE WILL EXIT THE SRN PLAINS AND TREK INTO THE CNTRL GT LAKES
TUES/WED. THERE HAS BEEN A TREND TO THE NORTH AND WEST OVER THE
PAST 24HRS. SINCE THE MID LVL FEATURE ASSOCIATED WITH THE
DEVELOPING SFC SYSTEM HAS NOT ENTERED THE CONUS DATA SENSING
REGION YET..ADDITIONAL SHIFTS IN THE STORM TRACK ARE POSSIBLE. THE
MDL CONSENSUS AVERAGE LIQUID QPF AND THE ANTECEDENT COLD AIR MASS
SHOULD ALLOW A SNOW/LIQUID RATIO OF 15/20:1. SNOW SHOULD INCREASE
OVER ERN/SRN CWA TUES NIGHT. A WINDOW OF LAKE EFFECT ENHANCEMENT
WILL OCCUR AT BEGINNING OF SYNOPTIC SYSTEM...PROBABLY ON THE ORDER
OF 4-8 HR DURATION. AS SYSTEM INTENSIFIES TUES NIGHT.. SFC PRESS
GRADIENT REACHES 15/20MB ACROSS CWA. WIND BLOWN SNOW WILL ADD TO
TRAVEL DIFFICULTY AS THE SNOW CONTINUES AND DRIFTING POTENTIAL
INCREASES BY WED MORNING. AREA MOST PRONE TO HIGHEST ACCUMULATION
APPEARS TO BE NW WISC WHERE DURATION OF SYNOPTIC SCALE SNOW AND
ADDED LAKE EFFECT WILL PROVIDE TWO FORCING MECHANISMS. SNOW SHOULD
TAPER OFF LATE WEDNESDAY NIGHT ACROSS ERN CWA BUT WINDS MAY
CONTINUE TO CAUSE BLOWING AND DRIFTING SNOW. INTENSE CYCLONE WILL
ALSO HELP DRAIN ANOTHER LARGE POOL OF ARCTIC AIR FROM CANADIAN
PRAIRIES INTO CWA THUR/FRI. COLDEST 85H TEMPS SO FAR THIS SEASON
ON THE WAY SO TEMPS REMAIN BELOW NORMAL FOR THE END OF THE WEEK.
&&
.AVIATION...18Z TAF ISSUANCE...
LARGE CLOUD SHIELD ACROSS NRN/CNTRL CWA WITH MVFR CEILINGS. LT
SNOW COVERAGE HAS DECREASED UNDERNEATH THIS CLOUD COVER THIS
AFTERNOON. EXPECT TERMINALS TO STAY MAINLY VFR INTO EVENING. MAY
SEE SOME REDEVELOPMENT OF CLOUD DECK LATER THIS EVENING IF SREF
PROBABILITIES ARE CORRECT.
&&
.POINT TEMPS/POPS...
DLH 10 18 10 23 / 10 10 20 60
INL 3 13 -1 12 / 10 10 10 20
BRD 8 18 7 18 / 10 10 10 50
HYR 8 21 10 22 / 10 20 10 60
ASX 16 24 16 23 / 20 30 20 60
&&
.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.
LS...NONE.
&&
$$
MILLER/CANNON
