Scientific Forecaster Discussion
fxus63 kilx 170146
Area forecast discussion
National Weather Service Lincoln Illinois
846 PM CDT Mon Oct 16 2017
issued at 846 PM CDT Mon Oct 16 2017
An elongated 1027 mb high pressure system is stretched from
southern Missouri through the Ohio Valley region promoting light
winds and clear skies over central and especially southeast
Illinois this evening. Little movement is expected in the high,
however a shortwave moving through the upper Midwest overnight
should help bring a light 4 to 8 mph south-southwest wind by
morning to areas north of I-70. As a result, the coldest
temperatures should end up south of I-70 with the best radiational
cooling. Temperatures should drop to the upper 30s south of I-70
with patchy frost possible in a few areas, while lower 40s should
prevail to the north. Forecast appears on track, so no significant
updates needed this evening.
Short term...(this evening through tuesday)
issued at 300 PM CDT Mon Oct 16 2017
Quiet and cool conditions will prevail for another night across
central and southeast Illinois, as we experience the second night of
Canadian high pressure. Based on the location of the surface
ridge axis just south of our forecast area, our southeast counties will
have the best chance at some patchy frost late tonight, where
winds will be lighter the longest. Lows in that area could dip
down around 37, so not a significant frost situation, but a few
low spots could see frost on various objects.
Some cirrus clouds could drift across Illinois tomorrow, as a weak
500mb shortwave moves over the top of the upper ridge. Otherwise,
full sunshine is expected tomorrow, with steady southwest winds
helping to push high temps into the upper 60s to low 70s.
Long term...(tuesday night through monday)
issued at 300 PM CDT Mon Oct 16 2017
High surface pressure centered on the mid-East Coast and sprawling
back west to the southern Mississippi River valley, will remain
nearly stationary Tuesday night and Wednesday. It will drift
westward and northward toward the mid-miss rvr Vly Wed night and
Thursday, then stalling out in that location through Friday.
During that time, the upper level ridge axis will shift from the
plains, across Illinois, then settle out just east of Illinois.
The combination of the upper and lower pressure patterns will
keep skies mostly sunny through the week, with gradually warming
temperatures. Friday and Saturday look to be the warmest days of
the next 7 days, with highs topping out in the middle to upper
70s, with lows in the mid to upper 50s.
The upper ridge will shift toward the East Coast on Saturday, in
response to an upper trough progressing across the plains. The
surface low pressure with that system is expected to remain well
to the north of Illinois, in Canada, but an associated cold front
will extend south all the way to Oklahoma. That front will
progress east across Illinois Saturday night and Sunday, when
showers will become likely. A few thunderstorms could develop
during the fropa, but instability parameters look marginal at this
point. Rain should come to an end Sunday night, as the system
departs to the east. Cooler conditions will develop for Monday,
with a few sprinkles even possible due to the upper trough axis
extending into Illinois from Canada. Highs Monday will cool down
about 10 deg from Saturday, with readings in the mid to upper 60s.
Aviation...(for the 00z tafs through 00z Tuesday evening)
issued at 632 PM CDT Mon Oct 16 2017
VFR conditions expected for the next 24 hours as high pressure
dominates the weather pattern. Skies skc-sct250. Light winds
turning to south-southwest by 02z. From 14-18z south-southwest winds increasing up to
10-15 kts with gusts near 20 kts.