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Area forecast discussion 
National Weather Service Lincoln Illinois
634 am CDT Tuesday Apr 21 2015

Short term...(today)
issued at 323 am CDT Tuesday Apr 21 2015

Windy conditions will once again develop across central Illinois
today, thanks to a tightening pressure gradient and deep-layer
mixing. The strongest winds will be focused along/north of the I-74
corridor, where forecast soundings suggest sustained winds of around
30mph with gusts up to 40mph at times. Will therefore issue a
Wind Advisory for this area from 11am to 7pm. Further south
across the remainder of the kilx cwa, winds will remain below
advisory criteria, mainly in the 25 to 30mph range. Skies will
be mostly sunny through much of the day, with an increase in
clouds noted across the far south during the afternoon as a
middle-level short-wave approaches from the west. All models are
developing scattered showers/thunder in advance of this wave, but
primarily keep the activity just south of the County Warning Area. Higher-res
models such as the hrrr are slightly further north, so have opted
to include slight chance probability of precipitation for showers south of I-70 this
afternoon. Thanks to increased sunshine, high temperatures will
be a few degrees warmer than yesterday, with readings climbing
into the lower to middle 60s.

Long term...(tonight through monday)
issued at 323 am CDT Tuesday Apr 21 2015

Main challenges in the extended continue to be frost potential
Wednesday/Thursday nights, as well as, timing of next precipitation event
by the end of the week.

Deep upper low currently centered over the western Great Lakes will
be the dominant weather feature across the Midwest for the next few
days, resulting in cool conditions through Friday. As a piece of
energy rotates around the low, a weak cold front will drop through
Illinois tonight. Forecast soundings are initially quite dry:
however, the latest models show quite a bit more top-down moistening
than in previous runs. As a result, think scattered light showers
will accompany the front tonight, with perhaps a few showers
lingering into Wednesday morning across the far southeast. Once the
front exits, Canadian high pressure will build into the region for
the middle and end of the week. The ridge axis is prognosticated to be
just west of the Mississippi River by 12z Thursday, so am
expecting winds to diminish considerably as the pressure gradient
weakens. With clear skies and light winds, overnight lows will
dip into the lower to middle 30s, leading to frost development
across much of the area. If skies remain clear, another
potentially frosty night will occur Thursday night as well.

Further out, models are having considerable difficulty pinning down
the end of the week system. Solutions have been flip-flopping from
run to run, so overall forecast confidence beyond Thursday remains
lows. The 00z Apr 21 GFS has made a major shift back to a solution
it featured a couple of days ago. Meanwhile, both the European model (ecmwf) and Gem
seem to be heading in the opposite direction. Given so much model
inconsistency, prefer to make very few changes to the extended.
With Canadian high pressure initially in place across the Midwest on
Wednesday/Thursday, still think a slower arrival of the next storm
system makes sense. As a result, have kept Friday dry despite what
the European model (ecmwf) and Gem are advertising. Have introduced probability of precipitation Friday
night into Saturday as a system over the Desert Southwest gets
kicked eastward. Still quite a bit of uncertainty concerning how
far north precipitation will spread, but have stuck with previous thinking
of keeping highest probability of precipitation focused across the southern half of the County Warning Area.
This is in good agreement with the latest GFS, but not the European model (ecmwf)/Gem
which both focus precipitation much further north. Once the system exits,
a return to dry weather is anticipated for Sunday before another
fast-moving northern-stream wave potentially brings a few showers
back into the picture by Monday.


Aviation...(for the 12z tafs through 12z Wednesday morning)
issued at 634 am CDT Tuesday Apr 21 2015

VFR conditions will prevail at all taf sites next 24hrs. Clear
skies will give way to scattered middle clouds advecting through the
area this morning and into this afternoon. Height of clouds will
lower to around 8kft later this evening just ahead of a weak cold
front expected to move through the area tonight. Believe lower
layers will be too dry for precipitation at first, but thinking showers
will be possible in conjunction with the front beginning late in
the evening and continuing into the overnight hours. Ceilings may
lower into MVFR ranges with pcpn, but not confident with this,
so will keep ceilings in VFR ranges. Precipitation will likely end before
sunrise. West winds will become quite gusty again today and should
get up to 30-35kts during the afternoon. After sunset winds will
taper off but still looking at 11-13kts during the evening. As the
front moves through around midnight, winds will become
northwesterly and still over 10kts.


Ilx watches/warnings/advisories...
Wind Advisory from 11 am this morning to 7 PM CDT this evening
for ilz027>031-037-038-043>046.



Short term...Barnes
long term...Barnes

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