Area Forecast Discussion
Issued by NWS Central Illinois

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS63 KILX 210445
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1145 PM CDT Mon Mar 20 2017

.UPDATE...
Issued at 840 PM CDT Mon Mar 20 2017

Have made a few changes to the overnight period. Have increased
clouds somewhat which should keep temps a little warmer than
previous package overnight.

18z models indicate weak wave moving into dry air from the
northwest will have a hard time precipitating into dry boundary
layer. Will also make some changes to PoPs for tomorrow to reflect
this drier scenario.

&&

.SHORT TERM...(This evening through Tuesday)
ISSUED AT 300 PM CDT Mon Mar 20 2017

19z/2pm surface analysis shows cold front just east of the I-55
corridor...with most of the associated convection well to the east
in Indiana.  While most high-res models suggest any additional
thunderstorms will remain east of Illinois, have decided to include
slight chance PoPs along/east of I-57 late this afternoon into the
early evening as the front passes.  After that, am expecting dry
weather for the rest of tonight with low temperatures ranging from
the middle 30s along the I-74 corridor...to the middle 40s south
of I-70.

Despite Canadian high pressure building into the Midwest on
Tuesday...a weak short-wave trough rippling along the southern
periphery of the high will bring clouds and perhaps a few light rain
showers to portions of central Illinois.  Frontogenetic forcing will
be strongest across the central and northern KILX CWA, so have
therefore focused the highest PoPs across this area during the
afternoon...with only slight chances further south into southeast
Illinois.  High temperatures will be held down to the clouds and
scattered showers, with readings mainly in the lower to middle 50s.

.LONG TERM...(Tuesday night through Monday)
ISSUED AT 300 PM CDT Mon Mar 20 2017

Once the short-wave exits the region on Tuesday, high pressure will
bring cool/dry weather for Tuesday night into Wednesday.  As the
high shifts off to the east, a southerly return flow will
develop...resulting in a marked warming trend by the end of the
week.  Several models are suggesting WAA precip breaking out on
Thursday: however, think they are a bit overdone given initial
relatively dry boundary layer.  Have therefore scaled back PoPs to
feature just slight chance for showers across the W/NW CWA Thursday
afternoon and evening.  Once this initial surge of WAA clouds/precip
lifts northward, a breezy and very warm day will be on tap for
Friday...with high temperatures surging into the upper 60s and lower
70s.

12z Mar 20 models continue to slow the next approaching system late
in the week...with the GFS/ECMWF/GEM all showing a deeper upper low
and a much slower surface low and associated frontal boundary.  As a
result, it appears most of the precip will hold off until Friday
night...then will linger through at least Saturday night as the
system occludes and only slowly meanders through the region.  After
that, it appears a warm/unsettled pattern will prevail...with above
normal temperatures and precip into the middle of next week.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1145 PM CDT Mon Mar 20 2017

High pressure continues to build into Illinois tonight.
Significant moisture remains trapped in the boundary layer
particularly over eastern Illinois. Drier air should advect in
late tonight as wind direction become less easterly, but until
then some IFR CIGS and MVFR vsbys seem likely at KCMI, and
possibly at KDEC, KBMI. Conditions should improve fairly rapidly
Tuesday morning as the drier air advects in.

Quick moving shortwave in northwest flow should impact terminals
Tuesday afternoon, but model trends have been to downplay impact
given the dry conditions near the surface. Will carry a VFR CIG
during the afternoon at the I-74 sites, but will leave out mention
of precip.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Barker
SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...Barker


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.