Area Forecast Discussion
Issued by NWS La Crosse, WI

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44
000
FXUS63 KARX 140931
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
331 AM CST Sun Jan 14 2018

.SHORT TERM...(Today through Monday Night)
Issued at 331 AM CST Sun Jan 14 2018

High Impact Weather Potential: Accumulating snow for all areas late
today into tonight. Increasing hints that a second batch of
additional snow will work back westward for areas near and east of
the Mississippi River Monday into Monday evening, but placement and
amounts remain lower confidence. Wind chill concerns also return for
western areas Monday into Tuesday morning.

One more quiet and cold night out the window right now, with surface
ridging just cresting the local area and heading southeast through
the day today. Return flow already underway just to our west,
manifesting in the form of a stripe of lower cloud cover working
back north toward our area, set to overspread most locations by
midday or early afternoon at the latest. Farther north, the main
focus is a robust shortwave dropping south out of northern Manitoba
as of midnight, with that feature well advertised for many days to
amplify southward into the upper Midwest by tonight and actually
close off into Monday before departing Monday night.

Increasing warm advection ascent ahead of said wave today will work
to saturate an initially very dry airmass, with snow expected to
break out by around sunset roughly near/west of the Mississippi
River, overspreading all areas tonight. Excellent tight agreement
among both ensemble and operational guidance for 0.1-0.2 inches of
QPF for most areas should equate to roughly 2-3 inches of snow given
good ratios of 20 to 1 or better with omega squarely bisecting a
deep DGZ, especially near and east of the Mississippi River. The
bigger question regarding additional accumulation arises into Monday
and Monday evening with increasing hints the past 24 hours for an
inverted trough axis to swing back southwestward toward the area,
though still some spread among guidance regarding the exact
placement of that feature. Given the setup, am a little concerned we
may realize some sneaky much higher amounts in persistent light snow
and continued good ratios in the vicinity of that trough axis where
low level convergence is progged to be quite strong, with almost a
TROWAL-like setup in place feeding into that boundary. Definitely
some potential for a few areas to sneak out 6"+ amounts of fluffy
snow before ending Monday evening, so will need to watch the
placement of the best convergence closely the next 24 hours.

As for headlines, do continue to have concerns about some drifting
and blowing snow for open areas and ridge tops toward the Monday
morning commute with shallow cold advection and 25-30 knots in the
mixed layer. Given still some falling snow during this time east of
the Mississippi, and fluffy nature of snow on the ground to the
west, definitely could see some travel issues into the Monday
morning commute (which may be a little lighter than normal with
the Martin Luther King Jr. Day holiday). However, based on current
trends, it won`t snow too long across western areas, but eastern
spots do look to see a long-duration lighter snow event, with many
areas picking up 4+ inches before it`s over. Per coordination with
other offices, have opted to issue a Winter Weather Advisory for
areas mainly east of the Mississippi River, but this may need to
be adjusted based on where any enhanced bands end up. Also have
concerns about wind chills, and have introduced a Wind Chill
Advisory for western counties Monday into Tuesday morning with
some very cold air dropping across those areas. Could even push
warning criteria for a few hours by Monday night.

.LONG TERM...(Tuesday through Saturday)
Issued at 331 AM CST Sun Jan 14 2018

Fairly quiet stretch of weather expected into mid and late week as
yet another iteration of a pattern change gets underway across the
CONUS, with loss of upper troughing across the area replaced by more
zonal and Pacific-dominated flow. That spells a gradual warmup by
late week, with many spots again pushing the freezing mark or better
by Friday per current trends, though pending some potential for
lower stratus (maybe even a little drizzle?) to develop with that
warmer air flowing over the very cold ground up this way. Also
watching increasing consensus for another stronger piece of energy
to eject out of the western CONUS and into the Plains sometime next
weekend, but still a large guidance spread so far out. Should be a
decent thermal gradient in place (similar to this past event) so
could be a messy one somewhere nearby. Lots of time to watch this
one.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1136 PM CST Sat Jan 13 2018

IFR conditions are expected in snow late Sunday afternoon through
Sunday evening, and likely all the way into Monday morning.
Clouds will increase across the region Sunday morning with
ceilings lowering to MVFR by mid afternoon. Snow spreads into the
TAF sites after 19z with conditions falling to IFR in the 20-23Z
timeframe. IFR conditions  in snow will continue through much of
the evening hours. Look for winds to increase out of the south
late Sunday afternoon, switching to the northwest Sunday evening
as an arctic front sweeps through. Some blowing and drifting snow
is possible at times especially at KRST.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Winter Weather Advisory from 6 PM this evening to midnight CST
     Monday night for WIZ017-029-034-041>044-053>055-061.

MN...Wind Chill Advisory from 3 AM Monday to noon CST Tuesday for
     MNZ079-086-087-094-095.

IA...Wind Chill Advisory from 3 AM Monday to noon CST Tuesday for
     IAZ008-009-018-019.

&&

$$

SHORT TERM...Lawrence
LONG TERM...Lawrence
AVIATION...Wetenkamp



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.