Scientific Forecaster Discussion

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Area forecast discussion 
National Weather Service Lincoln Illinois
632 am CDT Thu Apr 24 2014

Discussion...
issued 330 am CDT Thu Apr 24 2014

Short term...today through Sunday

00z models continue to be slower with cold frontal passage and
associated convection and that is the biggest change in the
forecast package. Most areas will be dry this morning with showers
and thunderstorms affecting areas from I-55 west this afternoon
and possibly getting as far east as I-57 late this afternoon. Storm Prediction Center
keeps slight risk of severe storms in southern Illinois south of our
County Warning Area. Though there is a 5% risk of damaging wind gusts in far SW County Warning Area
from Springfield to Lawrenceville south late this afternoon and
evening. Upper level trof over Colorado/nm with embedded short wave to
move into Illinois overnight while a cold front moves east across Illinois
during tonight. Have increased pops this evening due to slower
movement of front and then decreasing pops from west to east
behind cold front during overnight. Highs today in the upper 60s
NW over Illinois River valley to mid 70s se of I-70. Lows tonight 45-50f
over central Illinois and 50-55f in southeast Illinois. Rainfall amounts this
afternoon and tonight of a half to three quarter inch with locally
three quarter to 1 inch west of I-55.

Storm system to pass east of Illinois across in/Ohio Friday morning with
more sunshine returning and mild highs in the low to mid 70s and
warmest over SW counties. Even a few degrees warmer on Saturday as
models have 850 mb temps of 12-14c. Still appears dry Friday
through the day on Saturday with partly to mostly sunny skies Sat.
Rather mild again on Sunday with highs in the upper 60s to mid 70s.
Models have trended warmer this weekend ahead of next storm system
over The Rockies. Continue chances of showers and isolated
thunderstorms Saturday night and Sunday as warm air advection
regime sets up again.

Long term...Sunday night through Thursday

Extended models like GFS, European model (ecmwf) and Gem develop a strong/large cutoff
upper level low near Colorado Sunday morning and then move it into the MO
valley Tue and mid MS River Valley during middle of next week.
This to bring an unsettled weather pattern with daily chance of
showers and isolated thunderstorms from Sunday through Thursday
with highest chances Sunday night through Tuesday. Mild temps
early in the week to cool by middle of next week as upper level
low moves near Illinois. Widespread rainfall amounts of 1-2 inches
expected during this time with heaviest amounts southern areas.
Seasonable highs in the upper 60s and lower 70s Monday cool into
the low to mid 50s Wed/Thu.

07

&&

Aviation...
issued 625 am CDT Thu Apr 24 2014

Several forecast concerns this period include surface wind gusts
later this morning into this afternoon and a deterioration in
cigs this evening as showers and scattered thunderstorms and rain affect the taf
sites. Band of showers was located over east central Iowa, tracking
mainly to the northeast and not expected to affect our taf
locations this morning. However, as a frontal boundary out to our
west make progress to the east later today, the threat for showers
and storms will increase from west to east in the 20z-01z time
frame. Widespread rain and isold thunderstorms and rain will be the story this
evening with the cigs gradually lowering to MVFR with some brief
IFR cigs possible where some of the heavier showers/storms move
through. Steadier light rains will follow later this evening
before the system shifts off to our east late tonight. Surface
winds will be out of the southeast at 15 to 25 kts today with
a few gusts around 30 kts at times. Frontal passage is not expected until
or just after 03z at pia with cmi the last to see the wind shift
by 08z.

Smith
&&

Ilx watches/warnings/advisories...
none.
&&

$$