Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 280340

940 PM CST Thu Nov 27 2014

Issued at 935 PM CST Thu Nov 27 2014

Made an update earlier this evening for clouds and temps, and just
sent out another update. Temperatures fell pretty quickly across
northeast MO and western IL after sunset where there is some
residual snow cover and winds are very light within the center of
the retreating surface high. Meanwhile mid level warm advection
clouds have rapidly advanced across all but parts of south central
IL, and the clouds should overspread that area within the next
hour or so. Once the clouds move in, the temps should steady out
and then eventually rise a bit overnight as southeast winds
increase in the wake of the retreating surface high.



.SHORT TERM:  (Through Late Tonight)
Issued at 245 PM CST Thu Nov 27 2014

Surface ridge to begin moving off to the east tonight allowing winds
to become southerly by daybreak. Lingering mid and high clouds to
keep temperatures from dropping like a brick but will still see lows
in the upper teens to mid 20s.


.LONG TERM:  (Friday through Next Thursday)
Issued at 245 PM CST Thu Nov 27 2014

On Friday, we begin to warm up as winds pickup from the south,
gusting to near 25 mph at times, under mostly sunny skies. Highs
will be in the mid 40s to mid 50s. Milder Friday night with lows
in the mid 30s to mid 40s.

Saturday forecast a bit tricky. Models try to develop some light qpf
in warm sector ahead of next frontal boundary. Feel that it is
overdone and that it will be dry. Thus with models trying to develop
precipitation it is also indicating more clouds. Backed off on cloud
cover a bit to be partly cloudy across my area. Warm southerly winds
to persist so will see highs in the mid 50s to mid 60s.

Saturday night models begin to bring frontal boundary into forecast
area. Sided with the slightly slower NAM/ECMWF solutions. So expect
another mild night in the low 40s to low 50s. On Sunday front to
move through forecast area. So will see a wide range in high
temperatures ranging from the mid 50s far north to the upper 60s far
south. Low level moisture on the increase ahead of front so could
see some light precipitation develop over southeast half of
forecast area. Then as front pushes south of forecast area late
Sunday into Sunday night precipitation to shift a bit further
south...but could see some activity as far north as I70 corridor.
With colder air filtering in will see rain mix with and snow at
times. On Monday, as surface ridge settles into region, some
lingering mixed precipitation across far southern portions of
forecast area as highs will only be in the upper 20s to upper 30s.

Beyond that, extended models have very different solutions for
weather across the area around mid week. So confidence is low an any
of them. GFS keeps zonal flow and wants to bring in precipitation
for Wednesday night and Thursday while ECMWF wants to bring in an
upper level trof centered over great lakes and strong surface ridge
which would mean dry and cold conditions. For now have slight
chance/low end chance pops for this period with highs in the 40s and
lows in the upper 20s to mid 30s.



.AVIATION:  (For the 00z TAFs through 00z Friday Evening)
Issued at 625 PM CST Thu Nov 27 2014

VFR conditions and dry weather will continue thru the valid TAF
period. Main concern is winds, with a ridge of high pressure
currently over the area and this will move east shortly, resulting
in a light east or southeast flow initially...strengthening and
veering south on Friday...and then slackening off a bit while
remaining from the south Friday night. LLWS conditions should be
briefly met over in COU and UIN early Friday morning as a 40-45kt
low level jet forms and eventually mixes out as gusts later in the
day. May see LLWS conditions again later Friday night.

Specifics for KSTL: VFR and dry weather thru the period. Look for
VFR CIGs with light easterly winds developing for most of tonight,
veering southerly and becoming gusty on Friday. A moderate south
wind will continue into Friday night. Marginal LLWS conditions
will be attained on Friday night and will merit some watching for
future issuances. Along with the low level jet developing for
Friday night, model data also suggests non-VFR stratus developing
late as well. Something to consider for the 06z issuance again.





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