Area forecast discussion
National Weather Service Lincoln Illinois
645 PM CDT Sat may 18 2013
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.
&&
Aviation...
issued 645 PM CDT Sat may 18 2013
Diurnal cumulus will continue to dissipate over the next couple of
hours...resulting in mostly clear skies at the kilx terminals this
evening. Lead short-wave ahead of broad western Continental U.S. Upper trough
will approach from the west late tonight...spreading middle clouds
back into the area. Based on NAM relative humidity profiles and satellite timing
tools...it appears ceilings of around 7000ft will return to kspi
by 06z...then further east to kcmi by 10z. This cloud cover will
track across the area and eventually dissipate later Sunday
morning...leaving behind partly sunny skies for the afternoon.
Will have to watch for fog development tonight...as low-levels
remain moist and winds are expected to be rather light. Given
presence of clouds spreading in from the west and a continued southeast
breeze of around 5kt...have only lowered visbys to around 2-3sm
after 09z. Any fog will quickly burn off Sunday morning...as winds
veer to the S and increase into the 10-15kt range by afternoon.
Barnes
&&
Ilx watches/warnings/advisories...
none.
&&
$$
