Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 231757
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1157 AM CST Sun Nov 23 2014

.UPDATE...
ISSUED AT 1045 AM CST SUN NOV 23 2014

Updated forecast to remove the mention of isolated thunderstorms
this morning, but continued to mention isolated thunderstorms this
afternoon and evening especially along and se of the IL river. SPC
day1 outlook just updated and has expanded the general risk of
thunder this afternoon/evening further nw to a Galesburg to Henry
line. Otherwise just a few adjustments to wx/pop grids today as
occasional showers develop along with isolated thunderstorms.
Rainfall amounts through tonight still appear to average 1-1.25
inches across the CWA. The last time we have 1 inch or more of
rainfall was Oct 2. Highs in the upper 50s today with breezy sse
winds of 10-20 mph and gusts of 20-30 mph, similar to yesterday.

995 mb low pressure deepening se into central OK late this morning
to turn ne and eject into central IL this evening bringing the
showers and isolated thunderstorms to the region with deeper
moisture advecting in from the gulf of Mexico. 850 mb dewpoints
near 10C over southern tip of IL at dawn lifting into central IL
during the afternoon/evening. Temps were already 49-55F and should
climb about 5F more degrees rest of today with breezy sse winds.

&&

.SHORT TERM...(Today)
ISSUED AT 314 AM CST SUN NOV 23 2014

Weak short-wave that brought showers to east-central Illinois
earlier this evening has now lifted into the southern Great Lakes,
leaving behind cloudy, but dry conditions across central Illinois.
Upper air analysis indicates a plume of rich 850mb moisture streaming
northward from the western Gulf of Mexico.  As the low-level jet
gradually strengthens to around 40kt, models are showing showers
re-developing in this moistening airmass across north-central
Missouri between 09z and 12z.  The showers will increase in areal
coverage and lift northward into the Illinois River Valley this
morning, while locations further east toward the Indiana border may
see a lull in the precip chances through midday.  As northern stream
upper wave currently over the Rockies pushes eastward and helps
eject vigorous wave over southern Texas northward, synoptic lift
will increase markedly across the region later today.  Given strong
lift interacting with deep-layer moisture, showers will become
widespread across the entire area by mid to late afternoon.  In
addition to the precip, it will be a breezy and warm day.  Forecast
soundings suggest southeasterly wind gusts of 20 to 25mph, which
will help push high temps a few degrees above guidance into the
middle to upper 50s.

&&

.LONG TERM...(Tonight through Saturday)
ISSUED AT 314 AM CST SUN NOV 23 2014

00z Nov 23 GFS/ECMWF have both shifted the track of the approaching
surface low westward, and now look very similar to previous runs of
the NAM.  The new projected track will take the low from Kansas this
morning to northwest Illinois tonight, meaning central Illinois will
punch into the warm sector of the system this evening.  Given
presence of strong upper dynamics and marginal elevated instability,
have decided to expand the thunder mention further west and north
across nearly the entire area this afternoon/evening.  Rain chances
will be greatest during the afternoon and early evening, then will
decrease by mid to late evening as mid-level dry slot tries to push
into the area from the southwest.  As the low lifts further
northeastward into the Upper Peninsula of Michigan overnight, a
strong cold front will get pulled eastward.  NAM is slightly
faster with the arrival of the cold air, while the GFS generally
delays it until Monday morning.  Will take a blend of the models
here, resulting in deformation zone rain showers mixing with snow
across the Illinois River Valley toward dawn.  As the colder air
arrives in earnest, snow-showers will spread further eastward
toward the I-55 corridor Monday morning.  Heaviest precip will
generally be lifting northeastward with the low, so best chances
for accumulating snow will be along/northwest of a Rushville to
Bloomington line where around 1 inch will be possible.  Further
south and east, precip will be lighter and will remain in the form
of rain east of the I-57 corridor.  Aside from the precip chances,
blustery and much colder conditions will develop courtesy of
westerly winds gusting to between 30 and 35mph.  High temperatures
will be achieved early in the day, followed by readings falling
through the 30s during the afternoon.

Once this system exits the region, cold and dry weather will be the
rule for much of the week.  The only other chance for precip will
arrive on Wednesday as a clipper system skirts through the region.
WAA ahead of the wave will help boost temperatures well into the 30s
and even into the 40s across the far southern CWA, so precip type
will likely be a rain/snow mix.  Since QPF is expected to remain
rather light and temps will be well above freezing, am expecting
little or no snow accumulation Wednesday/Wednesday night.  After
that, a return to cold/dry weather is anticipated for Thursday and
Friday followed by moderating conditions by next weekend.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 1155 AM CST SUN NOV 23 2014

MVFR ceilings of 1-2k ft have developed over central IL airports late
this morning and expect ceilings to lower to IFR during the
afternoon and tonight. VFR visibilities at midday lower to 2-4
miles during mid and late afternoon and continue tonight as rain
showers become more widespread and heavier. Currently no
thunderstorms over IL and nearby states, but isolated
thunderstorms still expected to develop this afternoon and
evening, though coverage too limited to pin point donw in the
TAFS. Rain showers to mix with or change to light snow from west
to east during Monday morning with vsbys as low as 1-2 miles at
PIA and BMI, while 2-4 miles vsbys further south along I-72. SSE
winds 12-17 kts with gusts 18-24 kts this afternoon to diminish
closer to 10 kts this evening and then veer sw by overnight and
WSW later tonight into Monday morning and increase to 17-22 kts
and gusts 25-30 kts by 15Z/9 am Monday.

Deepening 994 mb low pressure just north of Oklahoma City in
central OK at midday to turn northeast and track into central IL
this evening as it deepens to 987 mb. Low pressure then tracks
into western lower MI late tonight as it deepens further to 980 mb
and pulls a strong cold front east across central IL between 08Z-
12Z. Very tight pressure gradient behing cold front to bring the
strong WSW winds by Monday morning along with the colder air
changing the light rain to light snow and more widespread over
northern airports of PIA and BMI.

&&

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

&&

$$

UPDATE...07
SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...07





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