FXUS63 KILX 192018
Area Forecast Discussion
National Weather Service Lincoln IL
318 PM CDT Thu Jul 19 2018
.SHORT TERM...(This evening through Friday)
ISSUED AT 315 PM CDT Thu Jul 19 2018
A weak band of showers/storms located from Springfield to the
WI/IL border continues to move to the northeast this afternoon. An
upper level low is currently located over southern Minnesota, and
will slide southeastward towards northern Illinois over the next
Forecast guidance continues to struggle with the ongoing
convection this afternoon, which complicates the forecast for
tonight. There are significant differences between the 12z
GFS/ECM/NAM and the past few runs of the CAMs. GFS/ECM continue
to be bullish, and develop scattered to widespread convection in
Iowa before storms spread into the western CWA after 00z tonight.
This solution has support from the past several runs of the HRRR.
On the other hand, the 12z NAM and most CAMs keep most of the CWA
dry through most of tonight and Friday. For now, expect at least
some convective development with the highest PoPs in the northern
CWA closer to the upper level low. Given a sheared (>30 kts) and
modestly unstable (>1000 J/kg) environment, at least a conditional
severe threat exists.
By Friday, considerable uncertainty remains regarding convective
evolution. A cold front should be progressing through the CWA
Friday morning, with MLCAPE values exceeding 2000 J/kg ahead of
the front. Combined with 30-45 kts of effective shear, severe
thunderstorms are likely...though model trends have shifted this
threat southeast of our forecast area... south of I-70 towards
IN/KY/TN. Convective trends will need to be monitored through
tonight for any changes.
.LONG TERM...(Friday night through Thursday)
ISSUED AT 315 PM CDT Thu Jul 19 2018
Upper level low to track across the southern Great Lakes and Ohio
river valley over the weekend. Isolated showers/thunderstorms are
possible during the daytime hours through Tuesday, especially
east of I-55. Temperatures will likely stay near or below normal,
with highs in the upper 70s to mid 80s.
Upper level low will finally drift south towards the gulf coast
by mid-week. Ridge will begin to build over the western U.S.,
keeping temperatures seasonable through the end of next week.
Convection chances should remain low during the middle of next
week with slight chances of showers/thunderstorms in southeast IL
on Tue and Wed during the afternoon hours.
.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1250 PM CDT Thu Jul 19 2018
Leaned on the HRRR model with handling convection into tonight. A
broken band of showers and thunderstorms moving eastward over
western IL early this afternoon, to weaken as it spreads to PIA
and SPI around 19Z, to BMI and DEC by 21Z and isolated coverage
at CMI by 23Z. Carried VCTS for a few hours to cover this, and may
need higher coverage this afternoon especially western airports.
The HRRR model shows another area of convection spread eastward
over central IL mainly north of I-72 from 05-09Z, mostly north of
SPI and DEC. Carried VCTS at I-74 TAF sites overnight for this
possibility. MVFR conditions could briefly occur with
thunderstorms, but otherwise VFR conditions next 24 hours. Models
showing MVFR clouds moving into northern/nw IL during Fri morning
and kept these lower MVFR clouds nw of PIA thru 18Z/Fri. More
convection expected with cold front during Fri afternoon, mainly
east of I-55 and just beyond the 24 hour TAF period for DEC and
CMI. SE to SSE winds of 7-12 kts this afternoon and evening to
veer sw during Fri morning with gusts of 15-20 kts after 15Z/10 am
Back to Main Forecast Discussion Page