Area Forecast Discussion
Issued by NWS St. Louis, MO

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
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 45 46 47 48

FXUS63 KLSX 170323

Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
923 PM CST Fri Feb 16 2018

Issued at 919 PM CST Fri Feb 16 2018

Have increased PoPs across the board for tomorrow as much of the
new guidance agrees that a band of measurable precipitation will
move across the CWA tomorrow. NAM Bufkit soundings continue to
suggest that the precipitation will begin as snow due to
wetbulbing effects and transition to rain as the lower atmosphere
continues to warm during the late morning and afternoon hours.
Current soil temperatures across the area are in the lower 40s and
air temperatures will be near freezing or slightly above freezing
during the period of snow, which should preclude any significant
impacts. The caveat is across the eastern Ozarks where heavier
precipitation could offset the relatively warm ground and lead to
a quick inch of snowfall. Have increased snow accumulation in this
area to account for this thinking.



.SHORT TERM...  (Through Late Saturday Afternoon)
Issued at 315 PM CST Fri Feb 16 2018

Surface ridge to continue building into region early tonight. So
will see winds diminish this evening. With the lighter winds and
clearing skies, temperatures to drop into the low 20s to low 30s.
However, will begin to see mid and high clouds move back into region
from the southwest as next system approaches area. The cloud cover
will keep temps steady and maybe even rise a bit towards daybreak
for portions of central and southern MO.

Also, low level moisture will be on the increase, but a lot of dry
air to overcome, so precipitation chances to very slowly ramp up
from southwest to northeast through Saturday morning with this
system. Some concern about precip type initially because of the
colder air and evaporative cooler aloft. So will see it begin as
light snow, then become mixed with rain, then all rain by midday
Saturday. Portions of central and southern Missouri could see a
few tenths of an inch of snow, especially over the Ozarks.
However, the ground will be a bit warmer so most of it will melt
on contact.

The rain will taper off by the late afternoon hours as system exits
region. Despite the cloud cover and precipitation, temps to warm up
into the low 40s to low 50s on Saturday.


.LONG TERM...  (Saturday Night through Next Friday)
Issued at 315 PM CST Fri Feb 16 2018

Active weather pattern to persist through rest of forecast period.

Will have a bit of a break Saturday night through Sunday with
temperatures moderating. Highs by Sunday will be in the mid 50s to
low 60s.

Warm southerly flow to persist Sunday night through Monday as a more
significant cold front approaches region from the northwest. Will
see several rounds of rain from Sunday night through Wednesday
evening. With slow movement of this front, a number of questions
remain. How much rain will fall across the region, will there be any
chances of severe weather, etc. For now will just mention beneficial
rains possible as do not feel that this will cause any flooding
since it will fall over a long period of time. The warmest day will
be Monday, with highs in the mid 60s to low 70s, then beyond that
temps will depend on cloud cover, precipitation and location of cold
front. For now slowly lowered temps through midweek with front
finally exiting region.

Beyond that, extended models continue to show active pattern with
additional chances of rain late Thursday night into Friday.



.AVIATION...  (For the 00z TAFs through 00z Saturday Evening)
Issued at 530 PM CST Fri Feb 16 2018

Ridge of high pressure begins to move east tonight ahead of the
next system for our area. Winds will veer to the east as ridge
moves out and then become gusty and southerly as system moves in
Sat. morning. Cigs will remain VFR until 18z tomorrow when MVFR is
expected for all sites. VFR cigs will return by late afternoon
Sat. as system moves out. This system looks to be a snow to rain
event but have left out snow mention in any TAF at this point. Any
impacts from snow look minimal at this time.


VFR and dry through the overnight hours with some mid and high
level clouds and northerly winds veering to easterly. Precip
begins at 15z and cigs lowering to MVFR around 18z. Winds will
continue to veer to the southwest with the passing of this system
and VFR cigs will return by late afternoon.





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