Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 130749
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
249 AM CDT Sun Apr 13 2014

.DISCUSSION...
ISSUED 249 AM CDT Sun Apr 13 2014

SHORT TERM...Today through Tuesday

Frontal boundary currently extending from the southern Great Lakes
west-southwestward across Iowa into northern Kansas will serve as
the primary focusing mechanism for convection over the next 24
hours. One round of showers/storms aided by 55 to 60kt LLJ has
lifted into southern Wisconsin/far northern Illinois, while
additional storms are beginning to develop further southwest
around the Kansas City area in advance of an upper short-wave
tracking out of the southern Rockies. As this feature pushes
further eastward, showers and thunderstorms will become more
numerous across the Mississippi River Valley into west-central
Illinois later this morning. Models continue to suggest that the
far E/SE KILX CWA will remain dry throughout the day, so have
confined POPs to locations west of a Danville to Effingham line.
Will be a windy and warm day as well, with southerly winds gusting
to between 30 and 35 mph. Afternoon high temperatures will range
from around 70 west of the Illinois River, to the upper 70s south
of I-70.

As cold front progresses eastward into the region, occasional showers
and thunderstorms are expected across the board tonight. With
strong convergence along the boundary, ample upper support from
the advancing short-wave, and precipitable water values
approaching 1.50, locally heavy rainfall will be likely. Despite
the threat for high rainfall rates within the storms, the risk for
severe weather will be minimal, as strongest instability/low-level
wind shear will remain focused further southwest from the Ozarks
into east Texas.

Cold front will push into Indiana by Monday morning, followed by
windy and sharply colder conditions. High temperatures will occur
during the morning hours, with readings dropping into the upper
30s/lower 40s during the afternoon. Brisk northwesterly winds
gusting to between 25 and 30 mph will make it feel even colder,
with wind-chill values dipping into the upper 20s/lower 30s. In
addition, approaching northern-stream short-wave will keep precip
chances alive despite FROPA. Thermal profiles suggest light rain
showers may mix with snow along/west of I-55 during the afternoon
as 850mb temps drop into the -4 to -8C range. NAM continues to be
the most aggressive in developing snow across central Illinois
late Monday afternoon into Monday evening, while all other models
are much lighter with the QPF within the cold airmass. Given
presence of upper support and adequate moisture profiles, will
carry a chance for snow-showers north of I-70 Monday evening. Any
accumulations will be minor and mainly confined to grassy surfaces
after dark. Once this wave passes, skies will gradually clear from
west to east overnight, allowing lows to drop below freezing.

LONG TERM...Wednesday through Saturday

After cold and dry conditions on Tuesday with highs only reaching
the 40s, rising upper heights will allow temperatures to warm back
into the 60s by Thursday. Next system of interest is beginning to
come into better focus, with the 00z Apr 13 ECMWF coming into
better agreement with prior runs of the GFS. Both models now bring
an upper wave and its associated frontal boundary into central
Illinois on Friday. Despite decent upper dynamics, instability
appears meager with this system, so will not mention thunder at
this time. Will bring chance POPs for showers into the western
half of the CWA Thursday night, then everywhere on Friday. After
that, a return to dry weather and near normal temperatures in the
60s can be expected for Saturday.

Barnes
&&

.AVIATION...
ISSUED 1150 PM CDT Sat Apr 12 2014

The 06Z TAF forecast becomes rather tricky by late tonight across
the central Illinois terminals. Southerly winds, frequently quite
gusty, should prevail through the period ahead of a slowly
approaching storm system. However, the forecast models continue to
struggle with the details regarding when the precipitation threat
arrives locally as the system draws closer. This also has a
significant impact on how soon conditions fall below VFR.

The low pressure center and frontal system with the storm still
lie well west and north of central Illinois through the night.
While some of the guidance has precipitation chances arriving
tonight as convective storm complex remnants to our northwest sink
toward the area, confidence in this occurring is low. The better
chance of showers and storms will come later Sunday morning into
midday as the main system approaches the Illinois border from the
west. Tried to time in arrival of the more widespread pre-frontal
precipitation with the best model consensus, and carried no more
than a VCSH mention before then. As the front draws closer heading
into Sunday evening, showers/storms will become more widespread
and heavier, resulting in the development of IFR conditions.

Bak
&&

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

$$







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