Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 191630

Area Forecast Discussion
1030 AM CST Wed Nov 19 2014


16z/10am surface analysis shows cold front quickly pushing toward
the I-57 corridor. Strong southwesterly flow ahead of the boundary
has helped boost temperatures into the middle to upper 30s across
the eastern half of the KILX CWA, while readings remain in the
upper 20s/lower 30s behind the front across the Illinois River
Valley. High temperatures for the day have already been achieved
across the west, but may climb a few more degrees into the lower
40s across the far SE before readings drop back into the 30s this
afternoon after FROPA. Once front passes, northwesterly winds will
increase markedly. Given several ob sites across Iowa showing wind
gusts to between 30 and 35mph, have increased gusts across the
western CWA accordingly. Large area of low clouds and flurries
noted on upstream satellite imagery across Iowa will spill into
central Illinois this afternoon. Latest surface obs show flurries
as close as KCID and a weather observer north of Galesburg noted a
few flurries as well. Have updated sky, temp, and weather grids to
better reflect current and expected trends.


.SHORT TERM...(Today)

Very broad 500mb trof dominating the country this morning, with a
small sfc trof/weak front approaching the region.  This morning at
least, with a ridge axis slipping to the southeast, southerly flow
is warming up the temps as the morning goes into the 20s
from the teens earlier tonight.  Short term forecast is rather
benign, though some small chances for snow showers across mainly the
northern portions of the state earlier.  Chance for flurries will
lessen as the day progresses in the wake of the sfc boundary and
have kept the mention only in the north for now, based on satellite
imagery and obs to the NW. Temps will reach very near their max T
early in the NW as the front moves through with more westerly winds
and cooler air by mid day.


.LONG TERM...(Tonight through Tuesday)

Deep cyclonic flow will keep the temps below normal through the end
of the week, though more southerly winds will begin to set up late
Friday in advance of a developing system to the SW. The main issue
in the forecast is the advancement of the rain while the sfc remains
below zero.  Too dry upstairs to support snow, and threat for fzra
is increasing with the precip preceding the warm up at the sfc after
the sun sets Friday evening.  So much struggle in the last few runs
with timing, and sfc and 850 temps that the detail is still lacking,
and forecast has remained somewhat conservative.  However, growing
concern that the cold air will be slow to erode after 06z early
Saturday has resulted in an extension of the fzra mention
overnight.  So far, little accumulation is showing in the qpf...with
temps struggling near freezing that night in Central
far south as Decatur through midnight...lingering into the early
morning hours. Models still lacking in timing and now the pop spread
is mainly from a messy ECMWF that is lingering precip in the wake of
the exiting system into Tuesday, which was removed from the
forecast.  Best chances for the weekend is in the high chance/likely
category for precip, though the temperature profile for now is still
indicating rain Saturday through Sunday.  With timing issues, am
keeping the likely mention to a minimum with the exception of the
Saturday night/Sunday...which is at least consistent with 24 hrs
ago.  That being said, a gap between the precip with the warm
frontal development and the core of the storm is developing which
may provide a break within that time frame. GFS and ECMWF still
showing some differences...and although the GFS is far more succinct
with the back end of the storm,  has still maintained the double
barrel look to the low center, elongating to the NW. The ECMWF is
becoming increasingly slow and with a lack of kicker wave...cannot
completely buy into either solution.  Either way...the weekend looks
wet, although struggling into the 50s will give Central Illinois a
break from the cold for Sunday.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)

A frontal system will track across the area this morning bringing
gusty southwest winds...which will shift more into a westerly
direction after FROPA (btwn 15z-18z). Not much in the way of
precip associated with the front this morning with the main
weather concern being the stratocumulus clouds tracking southeast
across central Iowa behind the fast moving cold front. Based on
the present movement over Iowa, it appears the low VFR with areas
of MVFR cigs (ranging from 2500-3500 feet) will arrive at PIA and
SPI btwn 14z and 15z and by 17z over at CMI. Forecast soundings
indicate as the colder air moves in, we may see the cloud bases
lower a bit which may take it down to MVFR for a time this
afternoon. Soundings also showing the clouds holding at least
thru 03z before high pressure builds in from the west which should
bring about a gradual clearing trend overnight. South to southwest
winds gusting as high as 23 kts ahead of the front will become
more westerly later this morning into the afternoon hours at 15 to
22 kts with a few gusts up to 30 kts at times before diminishing
this evening from the west.




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