000
FXUS63 KILX 041752
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1152 AM CST Tue Mar 4 2014

.DISCUSSION...
ISSUED 1041 AM CST Tue Mar 4 2014

Ridge of high pressure extending from New England to the Southern
Plains will control the weather across central Illinois today.
Abundant sunshine and southerly winds around the high will help
boost temperatures several degrees higher than they were
yesterday. 16z/10am readings have already risen 10 to 12 degrees
from cold morning lows in the single digits and teens. Based on
rate of temp rise and continued southerly flow, will raise
afternoon highs by a couple of degrees. Warming will be mitigated
somewhat by existing snow cover: however, think higher angle of
early March sun will be enough to raise temps into the upper 20s
and lower 30s today.


Barnes
&&

.AVIATION...
ISSUED 1151 AM CST Tue Mar 4 2014

Southerly winds of around 10kt will back to southeasterly this
evening, then to northeasterly late tonight into Wednesday
morning as a fast-moving clipper system tracks toward northern
Illinois. Models continue to focus the deepest moisture and
strongest lift across the north, with some light precip perhaps
arriving at KPIA and KBMI Wednesday morning. Forecast soundings
are initially quite dry, so have only mentioned VCSH after 12/13z
at those two terminals. Further south, will maintain dry
conditions with low VFR clouds by Wednesday morning.

Barnes
&&

.PREV DISCUSSION...
ISSUED 254 AM CST Tue Mar 4 2014

SHORT TERM...Today through Thursday

Shortwave tracking through southern WI has brought light snow as
close as northern IL early this morning, and radar returns as
far south as the northern CWA. Check of IDOT road cams shows a
dusting of accumulation at Galesburg as narrow band of 20 dbz
radar returns moved through. Aside from this affecting far
northern tier of counties for the next couple hours, main effect
of this wave is increased mid/high clouds which has steadied temps
in the teens. Back edge of mid clouds in central IA at 08Z so
expect clearing skies from W to E this morning. Late season Arctic
surface ridge lingers though the mid Mississippi Valley into this
afternoon, and even with stronger early March sun feel most areas
won`t make it above mid/upper 20s.

Complex forecast scenario unfolding for Wednesday, which could
bring accumulating snow back to the northern CWA. Lead Plains
shortwave is expected to spread light snow over Iowa and northern
IL Tuesday night, while a secondary shortwave lifts E/SE from the
central Plains. Some disagreement among medium range models in
this feature, with NAM most aggressive building energy east and
producing a frontogenesis induced several inch snow band over the
northwest third of the CWA Wed afternoon and evening. EC/GFS/GEM
build this energy south into the southern Plains, and show lighter
snow off the initial shortwave passing to our north. For now will
prefer the consensus solution which has ensemble support, and will
increase pops and snow amounts to an inch or two over the north
due to the northern stream shortwave. This portion of the forecast
will be refined over the next couple model runs. Otherwise, with
thicker clouds and east winds highs will again struggle to get out
of the 20s for most locations north of I-70.

Brief surface ridging brings mostly sunny skies back to the area
for Thursday. Slight moderation in 925/850 mb temps will allow
readings to get at or above freezing.

LONG TERM...Friday through Monday

Warm advection ahead of the next system developing in the Plains
will produce the warmest temps of the week on Friday, with highs
in the 40s expected area-wide. Late Friday a weak cold front is
progged to slide through the CWA, and as it settles near the Ohio
Valley overnight into Saturday morning, light over-running precip
develops north of the boundary in response to yet another
shortwave ejecting from the southwest U.S. trough. Precip type
remains a question at this point with thermal profiles showing
snow for the northern third, a rain/snow mix central and rain south.
QPF looks to be light, under a quarter inch. Surface ridging
brings quiet wx back to the area for Sunday, and as the ridge
shifts east early next week stronger return flow may produce the most
significant warming trend in several weeks.

25


&&

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

$$