Area forecast discussion
National Weather Service Lincoln Illinois
1138 PM CDT Sat may 18 2013
Discussion...
issued 852 PM CDT Sat may 18 2013
01z/8pm water vapor imagery shows a long-wave trough along/west of
The Rockies...with a weak lead short-wave noted further east over
Iowa/Missouri. High-res models such as the nam12 and 4km hrrr
suggest widely scattered showers/storms may develop in advance of
this feature over the next few hours. So far there has been no
evidence of development on regional satellite or radar
loops...however models insist it will occur after 05z. A quick
look at overnight forecast soundings do not look too favorable for
widespread precipitation...but given good model consensus...will leave
slight chance probability of precipitation in place across the west/SW kilx County Warning Area toward dawn.
Will also make a few adjustments to hourly temperature/dewpoint grids.
Zone update will be issued shortly.
&&
Aviation...
issued 1138 PM CDT Sat may 18 2013
Watching the potential for fog development tonight...particularly
across the eastern terminals where temperature/dewpoint spreads are
currently lowest. Will highlight kdec and kcmi for lowest visbys
in the 2-4sm range...with only minimal restrictions of 5-6sm
further west. High-res models still producing isolated
showers/thunder ahead of an advancing short-wave late tonight into
Sunday morning. Latest satellite/radar loops show no evidence of
this yet...but given good agreement/persistence...will include
a 5-hour period of vcsh at all sites except kcmi between 09z and
15z. Winds will initially be southeasterly at 5 to 10kt
overnight...then will veer to the south and increase into the 10
to 20kt range on Sunday. A more widespread area of convection is
expected to develop across Missouri Sunday evening...and this may
move into west-central Illinois after 06z Monday.
Barnes
&&
Previous discussion...
issued 250 PM CDT Sat may 18 2013
upper trough digging in over Rocky Mountains the start of a developing
low pressure storm system that will keep central and southeastern
Illinois in rain chances through middle week. For now...quasi
stationary boundary to the north and plenty of warm air over the
region...with 11c-12c at 850 and partly cloudy skies. Temperatures at middle
levels on the rise for the next couple of days as that surface low
gets a little deeper and southerly flow ahead of it anchors much
of Illinois firmly in the warm sector. Quasi stationary boundary may
drift a bit with mesoscale influence of any ts that may
develop...but for the most part...severe threat for tomorrow
confined to west/northwest closer to the low itself. For Monday...threat
more widespread as the low is slow to progress out of the Midwest.
Short term...tonight through tomorrow...
southerly flow and very warm temperatures tomorrow...upper 80s and close
to 90 as the 850mb temperatures rise to 16-17c. Heat for the northwest going to
be influenced by any ts/outflow/afternoon development of precipitation.
Though there is a chance for ts in the afternoon northwest of the
Illinois River valley...the majority of the threat will be after
00z tomorrow evening. However...much of this is based on the
slower GFS solution with the storm genesis to the SW. Moderate
risk in the SW...with much of the severe activity here being less
widespread in nature...and modified a bit as it moves further
away from the upper level support/dryline/mid level jet maximum that
is far Superior in the SW.
Long term...Monday through Friday...
as the upper low drifts closer to the region...chances for precipitation
and severe weather spread to entire County Warning Area for Monday. Ts chances
best in the afternoon...and wind and hail are the main
threats...though much of that hinges on the available instability
and location of middle level wind maximum. Rain/ts chances continue
through Wednesday evening as a cold front slowly progresses
through the region Tuesday night/Wednesday morning. Upper low slowly gets
out of here thur/Fri. And though GFS/European model (ecmwf) trying to spin up some
weak showers...leaving them out for now as region will be under a
building high briefly as another low digs in over the West Coast
late Thursday.
&&
Ilx watches/warnings/advisories...
none.
&&
$$
