Area Forecast Discussion
Issued by NWS Central Illinois
FXUS63 KILX 170200
Area Forecast Discussion
National Weather Service Lincoln IL
900 PM CDT Wed Apr 16 2014
ISSUED 900 PM CDT Wed Apr 16 2014
Made minor adjustments to the forecast to slightly increase the
cloud cover and drop the overnight low temperatures a tad.
The latest surface analysis indicated a cold front extending from
low pressure in north central IA through NW MO to extreme northern
TX. A moderate to strong pressure gradient will keep the S to SSE
winds going at 10 to 15 mph in central IL through much of the
night. The gusts have dropped off in most locations, and should
diminish in the rest of central IL soon.
Less of a pressure gradient will be present in eastern IL
overnight. This will combine with very dry air/dew points in the
20s, to allow temperatures to dip into the mid 30s. Forecast
soundings and high resolution model moisture profiles indicate
that most of the significant cloud cover will be along and west of
the IL River valley tonight.
ISSUED 646 PM CDT Wed Apr 16 2014
VFR conditions can be expected in all of central and eastern
Illinois the next 24 hours.
The main concern for early this evening will be the gusty south
winds. Wind gusts in excess of 25 knots will continue through at
least 00z and then drop off by 01z as the momentum transfer in the
lower atmosphere weakens. The wind will continue at 10 to 15 knots
from the south-southeast much of the night, but without the gusts.
A broken cirrus shield will cover the whole area through the
night. The lower and middle atmosphere is quite dry, so the
upstream clouds will have a hard time reaching central Illinois
late tonight and Thursday morning. Satellite interpolation and
moisture fields in the 850-700 mb layer on the GFS and NAM
indicate that a period of broken mid clouds may reach KPIA, but
not much farther than that.
The cold front extending from low pressure in central Iowa into
central Kansas will only slowly approach Thursday. The front is
expecting to reach the IL River Valley around mid-morning and
slowly advance toward east central IL by late afternoon and weaken
considerably. Upper level support, and just enough low level
moisture from the southwest, is not expected to interact with this
boundary until late Thursday evening, so the next 24 hours will be
ISSUED 211 PM CDT Wed Apr 16 2014
High pressure dominating the eastern half of the country from the
Mississippi River Valley eastward. Low pressure developing over
the Plains expected to move into the Midwest this evening bringing
a cold front in its wake. Relatively dry atmosphere in place will
limit the rain chances at this point...but a wave rippling along
this boundary will be the next problem in the forecast. The next
system in the forecast will bring pops for the end of the weekend
and into the next work week. Models having some consistency for
the early system...but having some major timing issues for the
weekend precip. For now, forecast remains more of a blend of the
ECMWF and the NAM, while ignoring the far more aggressive GFS in
SHORT TERM...Tonight through Friday...
Prolonged southerly flow over the region today has pushed warmer
temps into the FA this afternoon. This continues through the
overnight, resulting in a far warmer morning as lows tonight drop
to the upper 30s and lower 40s. Some clouds anticipated as a weak
boundary moves into the region tomorrow...somewhat tempering the
climb...warmer conditions with highs from the upper 50s to lower
60s. Agree with previous forecast that the dry atmosphere will be
hard pressed to produce rainfall tomorrow afternoon as a shortwave
ripples along the slowing boundary in Central Illinois. Once the
system has a chance to saturate, the pops go up for the overnight
Thursday night through to Friday morning, wrapping up by midday.
LONG TERM...Friday through Tuesday...
A general warming trend kicks in on Saturday as the warm
temperatures that were building under a midlevel ridge over the
west starts to shift eastward. Next chance for precip approaching
Sat night with two waves, one in the northern stream across
southern Canada... and the southern one a broader open wave over
the southern Plains. Between the two, a rather diffuse and
widespread area of rain for Sunday into Monday. GFS is far more
aggressive with the onset...and lingering the precip. Whereas even
the GFS was previously showing a dry Easter morning...it is
showing issues with run to run consistency. Have eliminated the
differentiation btwn Sun morning and evening for now. But the
best chances for precip will be later that night and into Monday.
On the other side of the precip, a warming trend continues for the
region with milder and drier weather. Max temps reaching into the
70s by Tuesday.