677 
FXUS63 KLSX 210324
AFDLSX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE ST LOUIS MO
924 PM CST WED JAN 20 2016

.UPDATE:
Issued at 859 PM CST Wed Jan 20 2016

Mid-high level cloudiness will continue to spread eastward
through our forecast area ahead of a strong shortwave moving
slowly eastward through KS. There may also be some stratus clouds
developing or retrograding from IL into parts of the area. The
radar was depicting some light precipitation in eastern KS ahead
of the shortwave. Looking at the latest HRRR and NAM model runs it
appears that this precipitation will remain west of our forecast
area tonight. With the cloud cover and lowering cloud ceilings
expected the temperatures later tonight should be nearly steady or
even rise slightly.

GKS

&&

.SHORT TERM:  (Through Late Tonight)
Issued at 330 PM CST Wed Jan 20 2016

Morning stratus has developed several holes in it during the course
of the day and now only occupies areas in southern IL and northeast
MO.  Temps are in the upper 20s and lower 30s where the sun has
broken out of the clouds, while still in the lower to mid 20s
elsewhere.  Another storm system has taken shape over western and
central KS with an area of snow, while a much more significant
system is moving thru UT and western CO at this time. 

The system over KS is expected to move slowly east tonight and
weaken with time, only making it to the eastern part of the state by
12z/Thu.  Any pcpn associated with this system should remain to the
west of our region tonight.  Of more significant note and challenge
will be sky cover, its effects on temps, and potential for any fog.
Sky cover should come from two main sources tonight:  first from mid
and hi clouds that will overspread our region later this evening
from the KS system, and also from the low stratus that survives
(mainly in southern IL) that will take advantage of veering cloud
level winds from north to southeast to both advect westward into the
heart of our region and expand in coverage as it does so.
Ultimately, this will cloud up all areas again, but not before many
areas will have the opportunity to have several hours of mostly
clear skies with light easterly winds this evening with fresh snow
cover.  Have tried to compensate for this contingency in the min
temp forecast, allowing for some areas in IL especially to drop into
the single digits, and this will probably also allow for some fog
development.  As clouds increase later tonight, should see temps
either steady out or even rise a few degrees.  Biggest adjustments
to MOS min temps are to the north and northeast of STL. 

TES

.LONG TERM:  (Thursday through Next Wednesday)
Issued at 330 PM CST Wed Jan 20 2016

Focus continues to be system on Thurs into Fri. 

Latest mdl guidance has continued a more sly track. Mdls do continue
to track a leading s/w lifting newd into the region late tonight
into Thurs. Can not completely rule out light precip across portions
of central MO, but based on forecast soundings, any precip will be
light and sct. Of some concern is that while the NAM is the only mdl
to suggest precip across this area, soundings also suggest that the
available moisture may not be deep enuf for SN and FZDZ may be a
threat. 

Otherwise, PoPs have been removed thru the weekend. Will need to
continue to monitor the more nrn trof Thurs night into Fri as it
drops swd into the area. Mdls suggest that any available moisture
will precip out before it reaches the CWA. Regardless, will need to
continue to monitor. 

Focus then turns to a system on Mon into Tues with a more amplified
trof digging into the region. Mdls disagree regarding how this
system will evolve and have therefore kept PoPs on the low end. Have
also kept a RA vs. SN going for now. Will begin to fine tune p-types
as the system approaches and mdls come into better agreement.

Tilly

&&

.AVIATION:  (For the 00z TAFs through 00z Thursday Evening)
Issued at 536 PM CST Wed Jan 20 2016

VFR flight conditions prevail across the region at this time,
however MVFR cigs are not far removed and that is the forecast
issue for this TAF package. Stratus with cig heights from
1500-2000 ft stretched from the OH Valley into far southern IL and
was also located across south central MO. Current expectations are
that the flow in the lowest 3kft of the atmosphere will gradually
veer to more southeasterly this evening, and this should allow the
stratus to advect northwest. If this in fact occurs the St. Louis
region terminals and KCOU will be impacted and that is reflected
in the latest TAFs, with cigs lowering to IFR on Thursday morning
at KCOU. Will also have to be on the watch for some light snow in
central MO but the probability is currently too low to mention. Some
improvement expected by midday and into the afternoon on Thursday
as the low level flow veers to more northeasterly.

Specifics for KSTL: 

VFR flight conditions prevail across the region at this time,
however MVFR cigs are not far removed as stratus with cig heights
from 1500-2000 ft stretched from the OH Valley into far southern
IL. Current expectations are that the flow in the lowest 3kft of
the atmosphere will gradually veer to more southeasterly this
evening, and this should allow the stratus to advect northwest and
back into the terminal. Improvement expected by midday and into
the afternoon on Thursday as the low level flow veers to more
northeasterly.

Glass

&&

.LSX WATCHES/WARNINGS/ADVISORIES:
MO...NONE.
IL...NONE.
&&

$$

WFO LSX