FXUS63 KDLH 300923
AFDDLH
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DULUTH MN
323 AM CST MON NOV 30 2009
.DISCUSSION...
THRU TUE...
SFC RIDGING WILL BE OVERRUN BY AN UPR LVL S/WV TDA WHICH IS EXPECTED
TO DEVELOP A BROAD SFC TROF BY MIDDAY. AMS REMAINS DRY...BUT UPR LVL
LIFT SUFFICIENT TO JUSTIFY SLGT TO LOW CHC POPS FOR MOST AREAS. BEST
CHC FOR -SN WILL BE ARROWHEAD THIS AFTN WITH PSG OF SFC TROF AND UPR
LVL VORT MAX. ANY ACCUMS SHUD BE LESS THAN AN INCH. BRIEF PD OF
RIDGING TNGT FOR MAINLY DRY CONDS. ANY LES ALG S SHORE WILL BE WEAK
AND SHORT LIVED. MUCH STRONGER S/WV APPROACHES ON TUE ACCOMPANIED BY
STRONG SFC SYSTEM. GFS/CN/ECMWF IN REASONABLY CLOSE AGMT ON POSITION
OF SFC LOW...WITH THE NAM A BIT SLOWER AND FARTHER N. MAIN SNOW BELT
WILL BE ACRS NRN PART OF CWA...GENERALLY ALG AND N OF THE IRON
RANGE. SNOW ACCUMS DIFFICULT TO DETERMINE AT THIS POINT...BUT
SEVERAL INCHES ARE LIKELY DUE MAINLY TO THE STRONG DYNAMICS AND IN
SPITE OF THE LACK OF A GOOD MSTR SOURCE. MUCH WILL DEPEND ON FINAL
TRACK OF THE LOW AND POSITION OF THE WFNT. EXPECT A SMALL INCRS IN
TEMPS TDA AND TUE IN WAA PATTERN AHD OF THE SFC LOW. RAPID COOL DOWN
THEREAFTER WITH THE BUILDING OF A HIGH AMPLITUDE RIDGE OVR THE W
COAST AND SHIFT IN TRAJECTORY TO ARCTIC REGIONS.
TUE NGT THRU FRI...
A WELL DEVELOPED MID LVL TROF/ASSOCIATED SFC LOW WILL CROSS NRN
TIER OF CWA AT BEGINNING OF PERIOD. MDLS DIVERGE SOMEWHAT ON
EXACT TRACK OF MAIN FORCING HOWEVER IT AN AREA OF ACCUMULATING
SNOW WILL CROSS THE NRN THIRD OF THE CWA TUESDAY NIGHT. SNOW MAY
BE ACCOMPANIED BY SOME INCREASINGLY STRONGER NW WINDS BY
MORNING.THIS SYSTEM WILL OPEN THE DOOR TO A PROGRESSION OF COLDER
AIR FOR THE REMAINDER OF THE WEEK. A LARGE AMPLITUDE MID LVL TROF
WILL DOMINATE THE REGIONAL PATTERN THROUGH THE REST OF THE WEEK.
THERE ARE SOME MINOR DIFFERENCES BETWEEN GFS/EC/GEM REGARDING AXIS
OF MID LVL TROF AND TIMING OF INDIVIDUAL SHORTWAVES WITHIN DEEPLY
CYCLONIC FLOW. WITH PROGRESSION OF COLDER AIR SOUTH FROM PLAINS OF
CANADA EXPECT SNSH TO BE COMMON THROUGHOUT THE PERIOD. OVERALL
SYNOPTIC PATTERN WILL PROMOTE INCREASING POTENTIAL OF SIGNIFICANT
LAKE EFFECT SNOW ACROSS WI SNOWBELT. BUFKIT LAKE EFFECT PARAMETERS
INDICATE A MAXIMUM INSTABILITY PERIOD BETWEEN LATE WEDNESDAY INTO
EARLY FRIDAY. DURING THIS PERIOD LAKE INDUCED CAPE WILL RISE ABOVE
500J/KG. MODERATE INSTABILITY VALUES ON THE COLLIER INDEX WILL
OCCUR AS 85H TEMPS DROP BELOW -10C AND LAKE INDUCED EQL REACHES
OVER 10K FT. VARIOUS QPF/LIQUID TO SNOW RATIO TECHNIQUES AND SNOW
AMNT ALGORITHMS SUGGEST AMOUNTS IN EXCESS OF SIX INCHES MAY BE
EASILY REACHED. STREAMLINE/TRAJECTORY IN LOW LEVELS STILL
UNCERTAIN AT THIS TIME SO WILL NEED TO MONITOR DEVELOPMENT OF LOW
LVL FLOW AS CORE OF INSTABILITY IS REALIZED.
&&
.AVIATION...06Z TAFS...
MVFR CLOUDS WILL CONTINUE TO ERODE FROM THE WEST OVERNIGHT.
ANOTHER AREA OF LOW PRESSURE WILL QUICKLY MOVE IN ON MONDAY...AND
SPREAD AN AREA OF FLURRIES OR LIGHT SNOW ACROSS MAINLY NORTHEAST
MINNESOTA MONDAY MORNING...SPREADING EAST DURING THE AFTERNOON.
THERE COULD BE A NARROW BAND OF BRIEF HEAVIER SNOW THAT TRANSLATES
THROUGH THE NORTHLAND...BUT AT THIS TIME...IT'S TOO DIFFICULT TO
TELL WHERE THIS BAND WILL SET UP AND WHICH TAF SITES IT WILL
AFFECT.
&&
.POINT TEMPS/POPS...
DLH 35 27 37 23 / 40 10 30 40
INL 33 22 32 18 / 40 30 60 40
BRD 37 26 42 24 / 30 10 10 20
HYR 35 21 41 26 / 40 10 10 20
ASX 35 25 39 29 / 50 20 30 50
&&
.DLH WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...NONE.
LS...NONE.
&&
$$
04/CANNON
