Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 151754
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1254 PM CDT Tue Apr 15 2014

.DISCUSSION...
ISSUED 1045 AM CDT Tue Apr 15 2014

Updated forecast just after 9 am for the ending of the freeze
warning sw counties. May need another freeze warning overnight across
the southern counties. Will update the forecast late this morning
to address more cumulus clouds forming over central and eastern IL
than earlier expected where skies currently partly to mostly cloudy.
Still expect mostly sunny skies over western counties and eastern
counties should see cumulus clouds decrease from west to east
during the afternoon as upper level trof shifts east of IL/IN later
today. Brisk nw winds 15 to 25 mph with cool highs in the low to
mid 40s look on track today.

07

&&

.AVIATION...
ISSUED 1255 PM CDT Tue Apr 15 2014

Scattered to broken cumulus cloud field with VFR bases of 4-6k ft
over central IL airports early this afternoon to gradually
decrease from west to east later this afternoon and dissipate by
sunset as upper level trof over MI/IN pulls eastward across the
ohio river valley during this afternoon. Breezy nw winds 10-15 kts
and gusts near 20 kts to diminish light and variable after sunset
as weak high pressure ridge drifts east over IL. 1001 mb low
pressure over central MT to track to the western MN/IA border by
18Z/1 pm Wed. This to increase mid/high clouds from the west later
tonight into Wed morning. Also increasing pressure gradient Wed
morning to increase sse winds 15-20 kts with gusts 25-30 kts
after 14Z/9 am Wed.

07

&&

.PREV DISCUSSION...
ISSUED 301 AM CDT Tue Apr 15 2014

SHORT TERM...Today through Thursday

Unseasonably cool weather will prevail across central Illinois
today. After chilly early morning lows in the upper 20s and lower
30s, afternoon high temperatures will only manage to reach the
middle to upper 40s. Winds will be quite a bit lighter than
yesterday, with a northwesterly breeze of 10 to 15mph expected.
The high pressure ridge will be positioned directly over the area
this evening, then will shift into the Ohio River Valley by dawn
Wednesday. As a result, coldest overnight lows in the upper 20s
will be focused across east-central and southeast Illinois where
winds will be lightest in closer proximity to the ridge axis.
Further west, a 10 to 15mph return flow will develop late tonight
across the Illinois River Valley, which will keep lows slightly
warmer in the lower 30s.

The pressure gradient between the exiting high and an area of low
pressure tracking through the Dakotas into Wisconsin will bring
windy conditions to central Illinois on Wednesday. In fact, a Wind
Advisory may eventually be needed for the W/NW KILX CWA where
gradient will be tightest. Forecast soundings and numeric guidance
indicate sustained southerly winds of 25 to 30mph in this area.
BUFKIT momentum transfer for KPIA shows potential gusts to around
40mph during the afternoon. Further southeast, gusts to 35mph will
be a good bet. Thanks to the strong southerly flow and ample
sunshine, temperatures will rebound into the upper 50s and lower 60s.

As Wisconsin low lifts into southern Canada, it will drag a cold
front toward central Illinois on Thursday. Front will become
stationary across the Illinois River Valley before an approaching
mid-level short-wave gives it a push eastward Thursday night into
Friday. While air mass will initially be quite dry, both the NAM
and GFS indicate a narrow band of post-frontal precip developing
Thursday afternoon/evening. GFS is further east into the NW CWA
with the precip, while the NAM holds it slightly further west
across eastern Iowa and northwest Illinois. Given proximity of
boundary, will carry slight chance PoPs along/west of the Illinois
River Thursday afternoon.

LONG TERM...Friday through Monday

Better rain chances arrive Thursday night into Friday as upper
wave tracks through the region. 00z Apr 15 models are not quite as
strong with the wave or its corresponding surface features.
Previous runs of both the GFS and ECMWF had shown a closed
surface low tracking through Illinois on Friday, but now no such
feature is evident. Even still, the upper wave interacting with a
weak surface boundary will be enough to trigger a few showers
Thursday night into Friday. Once this system moves eastward out
of the area, warm and dry weather will be on tap for Saturday
before another system potentially brings rain on Easter Sunday.
Both the GFS and ECMWF show a 500mb trough tracking through the
Midwest late in the weekend: however, the track and timing of the
wave remain somewhat in question. Latest ECMWF is deeper/further
south with the feature, resulting in a slower arrival of rain
chances mainly Sunday night into Monday. GFS has slowed from its
previous solutions as well, with the strongest lift crossing the
area Sunday night. With so many run-to-run discrepancies, decided
to make very few changes to the going forecast. Will still feature
a chance for showers during the day Sunday, but will hit PoPs
hardest Sunday night before shifting them south out of the area by
Monday.

Barnes

&&

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

&&

$$







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