577 
FXUS63 KLSX 181740
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1140 AM CST Wed Dec 18 2019

.SHORT TERM...  (Through Late This Afternoon)
Issued at 312 AM CST Wed Dec 18 2019

Light fog developed last night and early this morning across 
parts of the area, but visibilities should improve after daybreak.
Most of the area should see a fair amount of sunshine today, 
especially during the afternoon, and this will help to melt some
of the snow/ice from the recent winter storm. Highs will range 
from the upper 20s in west central IL to around 40 degrees in the 
eastern Ozarks. Such temperatures are around 5-15 degrees below 
normal for this time of year. 

Kanofsky

.LONG TERM...  (Tonight through Tuesday)
Issued at 312 AM CST Wed Dec 18 2019

Another cold night is expected tonight with lows ranging from the
teens in SW IL to the low/mid 20s in central and SE MO. The colder
temperatures are due to the combination of the snow-covered ground
and the lingering influences of a high pressure ridge extending
into the eastern CWA. A more noticeable warmup is expected
tomorrow with highs in the 40s to near 50 degrees with limited
cloud cover during the day, and this will accelerate the melting
process for the remaining snow/ice across the region. Although it
is not currently in the forecast, one item to watch will be the
fog potential for tomorrow night given the light winds and
additional moisture added to the lowest levels of the atmosphere
by the melting snow. The warming trend will continue through the
weekend and into early next week with highs expected to range from
around 50 degrees to nearly 60 degrees on Monday, which is 10-15
degrees warmer than average.

There appears to be little chance of precipitation over the next
several days. That said, model guidance has not reached a 
consensus regarding the only upper features of note during this 
period, and this introduces some uncertainty for Fri/Sat. Model 
guidance remains in reasonably good agreement through 
approximately 00z Fri regarding the overall upper air pattern, 
but the latest solutions are in no better agreement beyond that 
point than they were 24 hours ago. As noted yesterday morning, one
group of solutions depicts a strong PV anomaly over NM 
progressing eastward and becoming closed off from the prevailing 
flow, but another group of solutions depicts much more phasing 
between this feature and a separate PV anomaly to the north. The 
phased solutions depict a sharp trough axis moving quickly through
the region, but the unphased solutions keep a closed upper low 
across the ArkLaTex or ArkLaMiss regions. A closed upper low over
that area could affect the weather for the southern part of the 
LSX CWA. BUFKIT soundings continue to show dry air below 500 hPa 
as well as a saturated layer between approximately H5-H3, 
therefore these PV anomalies are currently expected to produce
only an increase in mid/high level clouds for Fri.

Kanofsky
&&

.AVIATION...  (For the 18z TAFs through 18z Thursday Afternoon)
Issued at 1137 AM CST Wed Dec 18 2019

Stratus and fog have moved south of all TAF sites, so VFR flight
conditions expected through the forecast period with surface 
ridge overhead. Light and variable winds will pickup and veer to 
the south by later this evening as ridge begins to move off to the
east.

Byrd
&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$

WFO LSX