northern indiana: fxus63 kiwx 082104

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fxus63 kiwx 082104
afdiwx
area forecast discussion
national weather service northern indiana
404 pm est mon feb 8 2010
.short term...
...major winter storm approaches...
tonight through tue night.
tonight...upstream of sern sd vortex isent response underway tonight
with strong/25kt cross-isallobaric/therm with relatively abundant
late winter mstr with over 2 g/kg into nern in to 3 g/kg tap north
of oh rvr to allow for rapid ewd expansion of wrn il to swrn mo
snowfall east-northeast through the entire fa by daybreak...as kilx
and kdtx raobs as well as bufkit cross-sectional views indicate
little/thin dry arctic wedge easily to overcome.
for tue snow becomes heavy at times acrs entire cwa. ern sd vortex
to undergo phasing with srn stream/ok panhandle stratospheric
intrusion assocd with wake of sharp srn stream shortwave...as 200
plus kt ul jet max emerges out of epac ul trof into chihuahuan
desert/edwards plateau by f18. as ul jet max lifts slowly newd acrs
nrn ms tue night and into ern tn by 12 utc wed...wl see strong left
exit region ul divergence with correspondent midlvl/7-5h 12 hr hght
falls of 150m/12 hrs congeal acrs kstl by 18 utc tue per both
gfs/nam and further increase in excess of 200 meter falls by tue
night acrs far nern ky. sfc response noted as sfc trof fm ern ia
curving through tn vly to kmsy draws defined sfc low into cntl tn by
15 utc tue and proceeds to bomb into nrn ohio/tracking just se of
cwa into tue eve. assocd trowal develops acrs ern to cntl cwa and
progresses grdly nwd to nrn cwa and then trowal/deformation pivots
nicely counter-clockwise through cwa with best mstr/lift coexistent
with moist and deep dgz with more than 5kft depth to dgz acrs
nrn/cntl where highest totals are still anticipated despite latest
nam12 slight slower/more nw trend...with any tue night dry slot
concerns remaining well south of cwa. totals upwards of 1 foot psbl
by daybreak wed acrs north and as nw sfc winds begin to cause sig
drifting with start of coastal energy xfer adding to incrs in sig
sfc pres rises.

.long term...
wed through monday
generally high confidence per weather details in the long term
period as a weakly positive pna regime enhanced by the ongoing el nino
interacts with reloaded blocking over greenland. mean nw flow is
expected with continued reinforcement of strong cp airmass from
interior canada...supporting below normal temps through the period.
there is very good support among all deterministic fields and
ensemble means per mean height fields. although given ne pac
troughing offering several clipper like systems to the
table...differences are noted on the timing/strength/and track of
each of these systems...offering very low confidence in any pop
addition. have generally followed a gefs mean through the
period...utilizing the gfs and gfs bias corrected grids in temps
details given a deep snow cover expected from the departing system
wed. did side heavily toward a nam/gfs/sref blend in days 3-4.
wed...deep negative anomaly will be in the process of exiting the
region...with lingering snow expected in the east in the morning.
examination of 285-290 k isentropic maps indicate weak ll ascent
continuing through late morning before subsidence is favored in the
column. still concerned with a lake enhanced mid lake band per long
fetch deep flow over lk mi. although h85-lk sfc delta t/s will be
marginal in the 11-13 c range...seeder feeder/enhanced ll convergent
cyclonic flow/and a possible aggregate connection to lk huron will
offer a period of heavy snow with additional amounts of 1-3 inches
expected over the far nw zones. deep pressure falls combined with
sfc ridging over the western midwest will support a tight pressure
gradient over the region. nam-gfs h950 geostrophic flow over the
region is in the range or 50-60 knots...and given a caa regime in
the presence of unidirectional flow...expecting strong gusty winds
through wed. sfc winds of 15 to 25 mph can be expected with gusts of
35 to 40 mph. this will support sig blowing and drifting of snow
with near blizzard conditions at times. winds will gradually ease
through the day...but still remain breezy into the evening. the lake
effect snow band is expected to shift east align nw-se over the nw
zones...with a break up to multiple parallel bands expected...with
possibly one strong band lingering into the late afternoon. a heavy
wane trend is expected as synoptic lift ends and subsidence with
falling inversion heights limits strong ll ascent in a marginal
stability environment. did carry snow chances through wed night with
a transition to flurries on thur.
thur-mon...general cold nw flow can be expected with mostly cloudy
conditions northeast half per lk mi flux. disturbed nw flow will offer
clipper system chances...but given poor model consistency per
system details have decided to leave any snow chances out of the fa
at this time. gfs solutions per any upper trough is definitely in the
outlier status...with only one or two gefs members supporting pops
in the sat-mon period. sfc ridging will dominate through most of
friday...with light winds...fresh snow pack...and thin clouds to
clear skies offering very cold temps. have adjusted mins down for
this...especially away form the lake in the south. areas close to lk
mi will likely retain low clouds...and feel a warmer bias was
necessary at this time until a better handel on ll flow and moisture
is ascertained. overall...expected temps 10 to 15 degrees below
normal in the period...with sub zero readings possible thur night
where skies are clear.

.aviation /18z tafs/...
cont of prev taf fcst with primary exception to tank the fcst with
moderate snow/lifr conds toward latter 4-5 hrs of valid time as sfc
low begins to lift quickly nne into lwr oh vly with significant mstr
available/strong uplift and favorable temperature profile for large
flake size production to severely limit vsbys with lwrd
obscurations. more precise timing of initial onset of ifr conds to
be afforded with next issuance...psbl pd of mvfr cigs/vsbys prior to
snow starting in earnest aftr midnight.

.iwx watches/warnings/advisories...
in...winter storm warning from midnight est /11 pm cst/ tonight to 7
pm est /6 pm cst/ wednesday for inz003>009-012>018-020-
022>027-032>034.
mi...winter storm warning from midnight tonight to 7 pm est wednesday
for miz077>081.
oh...winter storm warning from midnight tonight to 7 pm est wednesday
for ohz001-002-004-005-015-016-024-025.
lm...gale watch from tuesday evening through wednesday evening for
lmz043-046.


short term...murphy
long term...jc
aviation...murphy

Top tags: snow, expected, sfc, flow, tue, acrs, per, strong, cwa, gfs