Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 171552

Area Forecast Discussion
National Weather Service Lincoln IL
1052 AM CDT Thu Apr 17 2014

ISSUED 1045 AM CDT Thu Apr 17 2014
Low pressure system making its way through Wisconsin this morning
dragging a cold front across the state. Measurable precip not
expected for the day along the boundary. Some weak echoes showing
up on radar NW of the boundary however with some of the llvl
clouds. Will keep an eye on the potential for precip...but
anticipate little more than possibly a sprinkle before 00Z. Have
boosted the high temps in the far east as the boundary is not
likely to make it too much further then I-55 and just barely
adjusted a couple of temps. Not even enough to warrant a zone
update. Wave to the SW still expected to ripple through the region
and along the boundary later this evening and produce a bit of
rainfall across the area. Best chances are in the center of the
state/along the boundary as it slows.


ISSUED 630 AM CDT Thu Apr 17 2014

Core of low level jet starting to move northeast out of central
Illinois. Initial stages of our 12Z balloon sounding have peak
winds around 35 knots at 1200 feet, with region radars showing the
stronger winds now in northeast Illinois. Have thus removed LLWS
mention at all sites.

VFR conditions to prevail through the period. Do have some concern
for a large area of MVFR ceilings that was edging into far western
Illinois and extended northeast along the Iowa border. Latest HRRR
guidance wants to bring this as far east as KPIA, but low level
winds would suggest a more northeast component to the moment,
taking a close pass at KPIA in a couple hours. Weakening cold
front will result in a gradual switch to westerly winds today,
then more of a light/variable component overnight. Ceilings
expected to lower to around 5000 feet this evening as an upper
disturbance moves across the state. Moisture below 7000 feet is
somewhat lacking, but some of the models, as well as SREF
probability graphics, showing some light precip potential for the
KSPI-KCMI corridor. Have only gone with a PROB30 group for now due
to the questionable amount of coverage.


ISSUED 238 AM CDT Thu Apr 17 2014

SHORT TERM...Today through Saturday

Low pressure analyzed over western Wisconsin on 07z/2am surface
analysis will continue to lift northeastward today, dragging a
weak cold front into central Illinois. Boundary will make only
slow progress eastward and will eventually stall along the I-57
corridor this afternoon. Little in the way of sensible weather
will accompany the front other than a few mid/high clouds.
Afternoon high temperatures will range from the upper 50s west of
the Illinois River to the middle 60s south of I-70.

Short-wave trough currently evident on water vapor imagery over
the Texas panhandle will track E/NE, passing south of Illinois
late tonight into Friday. Enough synoptic lift will be generated
by this feature to perhaps trigger a few light showers along/near
the stationary frontal boundary. Mitigating factor for precip will
be lack of moisture, as air mass remains very dry in the wake of
the early week cold front that penetrated well into the Gulf of
Mexico. Surface dew points have only recovered into the middle 50s
across coastal Texas, with models projecting 40-45F dew points
reaching central Illinois tonight. Forecast soundings remain dry
below 850mb, so am not expecting much in the way of precip. Will
hold on to low chance PoPs tonight, with scant rainfall amounts of
only a couple hundredths of an inch at best.

Once upper wave passes by to the south, surface high pressure will
resume control of the weather on Friday. After some lingering
sprinkles/clouds across the east during the morning, sunshine will
return across the board by afternoon with highs climbing into the
lower to middle 60s. As the high shifts off to the east, increasing
southerly winds will bring even warmer air into the region on
Saturday resulting in highs reaching the upper 60s and lower 70s.

LONG TERM...Sunday through Wednesday

As has been the case for the past few days, the latest model suite
has once again delayed the onset of the next storm system early
next week. One upper wave is expected to track across southern
Canada over the weekend, while another slower-moving southern
stream wave will track out of the Desert Southwest into the lower
Mississippi River Valley by Monday. The GFS had previously been
the fastest model with this southern stream feature, introducing
precip as early as Easter Sunday. 00z Apr 17 run of the GFS has
now slowed the system and is in much better agreement with the
more consistent ECMWF/GEM, which have featured a dry Sunday for
the past couple of runs. As a result of this model consensus, have
removed mention of rain on Easter and have boosted highs into the
lower 70s. Showers will spread into the western KILX CWA Sunday
night, but will become most prevalent on Monday. Have hit PoPs
hardest and lowered highs into the upper 60s on Monday accordingly.
Have also added mention of isolated thunder due to Lifted Index
values dropping to between 0 and -2C Monday afternoon. There are
some indications that the precip may be delayed even further into
Monday night and early Tuesday. Will hold on to chance PoPs across
the E/SE on Monday night, but will return to a dry forecast on
Tuesday. Once this system exits the region, an approaching warm
front may trigger a few showers across northern Illinois on
Wednesday, but the main weather story in the extended will be the
warm conditions as temps routinely climb above normal into the 70s
next week.




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