Area Forecast Discussion
Issued by NWS Central Illinois

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595
FXUS63 KILX 251543
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1043 AM CDT SUN SEP 25 2016

.UPDATE...
Issued at 1040 AM CDT Sun Sep 25 2016

Update the forecast about an hour ago to remove the patchy fog
wording this morning. Also updated to lower pops over western CWA
this morning as much of area still mostly sunny and dry at 1030
am. HRRR model appears to be too quick develop convection over
central and western CWA late this morning and slowed this down by
a few hours. Otherwise one more warm and rather humid summerlike
day expected over central and southeast IL, with highs mostly in
the 80s, ranging from lower 80s over far nw CWA by Galesburg, to
near 90F far southeast CWA by Lawrenceville. Late morning surface
map shows a cold front over central IA and western MO while a
prefrontal trof was pushing east near the MS river. Aloft an upper
level ridge was over the OH/TN river valleys. Patchy fog lifted
during mid morning leaving mostly sunny skies across CWA.
Temperatures warmed up into the upper 70s and lower 80s while
dewpoints ranged from 65-72F with southerly winds 5-15 mph.

Models continue to push cold front east into the IL river valley
late this afternoon, and through central and eastern IL during
this evening. Models agree with scattered convection developing
across much of CWA during the afternoon and continuing this
evening especially east of the IL river. SPC day1 outlook has a
marginal risk of severe storms for 5% risk of damaging wind gusts
this afternoon until sunset/7 pm along and east of a Peoria to
Springfield line and north of I-70. CAPES increase to 1-2k J/kg
east of the IL river during this afternoon into mid evening and
highest over southeast IL where some models have CAPES peaking a
bit above 2k J/kg. The 0-6km bulk shear is weak over central and
southeast IL today, less then 30 kts east of the IL river this
afternoon and only increase above 30 kts behind the front nw CWA
late this afternoon.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 322 AM CDT Sun Sep 25 2016

CWA is now caught right in between the surface ridge to the east and
the cold front approaching from the west. Short-term model trend has
to slow the onset of precip into the CWA. Based on radar trends and
surface analysis, looks like precip will not arrive until this
morning; so, will have just slight chance of precip over the western
part of the CWA this morning and then increase pops to chance
northwest of the Illinois river before noon. Precip will spread east
through the CWA during the afternoon and into and then continuing
into the evening hours. Precip will gradually come to an end, from
west to east, behind the front after midnight. POPs will be in the
chance category ahead and behind the front, with likely along the
front as it moves east through the CWA. Precip type should be
showers and storms, mainly in the afternoon and evening, but
isolated thunderstorms will continue into the overnight hours
tonight.

Temps will once again be very warm across parts of the CWA, mainly
looking at the mid to upper 80s east of the Illinois river and
toward the IN border. Overnight lows will be cooler than the last
several days, with mid to upper 50s common, except in the southeast
parts of the CWA where lower 60s is likely.

.LONG TERM...(Monday through Saturday)
ISSUED AT 322 AM CDT Sun Sep 25 2016

Main focus for the longer range period will be the evolution of the
current upper low spinning over North Dakota. Models remain in good
agreement in this evolving into a fairly strong upper low over Lake
Superior by midday Monday, with the low only slowly weakening with
time as it wobbles across much of the Midwest. The latter week still
shows some discrepancies with the track of this low. The ECMWF
drifts it back north from the Tennessee Valley and it still is
present over northern Ohio by late Sunday, while the GFS lifts it
into New England on Friday. The former scenario would suggest some
late week showers as the associated surface low drifts north out of
Kentucky, while the latter scenario pretty much keeps us high and
dry aside for a few potential lake-effect showers over the far
northeast CWA on Thursday. With the uncertainty and what likely
would be spotty coverage at best, will continue to keep the forecast
dry for the time being.

A gradual moderation of the air mass should result in temperatures
climbing a degree or two each day this week, but the overall dry
conditions should result in a nice diurnal swing each day. Lows in
the 40s are likely Monday and Tuesday nights, and perhaps
Wednesday night as well if the ECMWF pans out.

The deepening of the low will result in rather breezy conditions
Monday and Tuesday afternoons, with some wind gusts of 25-30 mph
across the northern CWA.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 558 AM CDT Sun Sep 25 2016

MVFR conditions should prevail at all TAF sites next 24hrs, except
for some light fog around 2-4sm will be present this morning.
Based on dewpt spreads and what`s occurring right now, believe fog
will only last 1-2hrs. Satellite shows some scattered clouds
around 5kft, but the cold front approaching will keep these
scattered clouds and mid/high clouds around some of the western
TAF sites this morning. The cold front, still sitting across
central IA is forecast to reach the TAF sites this afternoon,
which is when the showers and isolated thunderstorms should reach
the TAF sites. Showers and storms have dissipated out west, but
expecting them to refire near the front as it moves into the area.
Precip will begin at the TAF sites later this afternoon and
continue into the early evening hours. Early evening will see area
still in cyclonic flow so isolated showers appear to still be
possible. Have a 20pct for showers at all sites. The after
midnight, clouds will scatter out. Winds will be southeast through
most of the day, and then become northwest...this evening.

&&

.ILX Watches/Warnings/Advisories...
NONE.

&&

$$

UPDATE...07
SHORT TERM...Auten
LONG TERM...Geelhart
AVIATION...Auten



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