Area Forecast Discussion
Issued by NWS St. Louis, MO

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FXUS63 KLSX 280545

1145 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 06z TAFs through 06z Friday Night)
Issued at 1145 PM CST Thu Nov 27 2014

VFR conditions and dry weather will continue thru the valid TAF
period. A ridge of high pressure has now moved to our east and has
initiated a light easterly flow. This will then strengthen and
veer south after daybreak on Friday...and then slacken 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 moves overhead and then mix out by late
morning as gusts. May see LLWS conditions again later Friday night
for all TAF sites but will deal with that on later issuances.

Specifics for KSTL: VFR and dry weather thru much of the period.
VFR CIGs will exit late tonight as winds veer from the south and
become gusty after daybreak on Friday. A moderate south wind will
continue into Friday night. LLWS conditions of a marginal nature
could threaten Friday night and will merit some watching for
future issuances. Along with the low level jet developing for
Friday night, model data continues to strongly suggest non-VFR
stratus developing late in the night. Have introduced CIGs at the
1500ft level for now, with data supportive to a degree of IFR





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