Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 231718

Area Forecast Discussion
National Weather Service Lincoln IL
1218 PM CDT Thu Mar 23 2017

Issued at 938 AM CDT Thu Mar 23 2017

Warm air advection managed to spawn a decent convective cluster
that mainly tracked to our southwest, but a larger wing of light
showers has been pushing eastward across the forecast area this
morning. Morning balloon sounding from our office sampled some
fairly dry air below 8,000 feet and precipitation has been fairly
light, with some brief heavier showers that reduced visibility to
a few miles. The dry air is starting to take its toll and the
showers have begun decreasing in coverage. Forecast was updated
earlier to bring the showers much further east/southeast this
morning. The short-range high-res models do have some showers
lingering into the first part of the afternoon from west central
into south central Illinois, with the RAP and HRRR fizzing them
out by mid afternoon, and the updates tailed back the PoP`s to
just the northwest CWA by then.

Temperatures off to a bit of a cooler start due to the rain, so
hourly trends and highs were adjusted a bit downward.


.SHORT TERM...(Today and tonight)
ISSUED AT 351 AM CDT Thu Mar 23 2017

Strong high pressure will slide off the east coast today as a
weather system develops in the western plains. A pseudo warm front
has developed just west of the area and radar is showing that warm
air advection precip has already begun to develop in eastern MO.
Models agree that precip will continue to increase into this
morning, but differ on how extensive it will become. NAM and ECMWF
have very little precip while the GFS is a little more extensive
with its coverage, but all agree that western areas of the CWA is
where pops should be highest with eastern areas probably not seeing
any precip at all. So will keep chance pops going this morning, but
diminish the eastern extent of coverage. Then will have diminishing
pops during the afternoon hours as the best forcing lifts to the
north. Drier air returns this evening so dry weather expected
through the night as best forcing is well north of the CWA and the
main low pressure of the system continues to deepen out west. Winds
will remain southeasterly through the day with some gusts to around
25mph. Winds will become more southerly tonight with wind speeds
remaining around 10-15mph. Temps today will be warmer than yesterday
with warmest temps in the west where some sun should be able to work
into the area during the afternoon. The continued warm air advection
tonight will hold temps up, remaining nearly steady or falling only
a few degrees.

.LONG TERM...(Friday through Wednesday)
ISSUED AT 351 AM CDT Thu Mar 23 2017

A breezy and mild day expected Friday with partly to mostly
cloudy skies and highs in the low to mid 70s, warmest in western CWA
along and west of I-55. Isolated showers and thunderstorms possible
west of a Peoria to Jacksonville line late Friday afternoon. So most
areas will likely stay dry through the day Friday.

A vigorous upper level trof digging into CA early this morning will
develop a strong cutoff upper level low near the southern CO/KS
border by sunrise Friday, and move east into the Ozarks by sunrise
Sat. Showers and isolated to scattered thunderstorms will likely
spread eastward across areas west of I-57 during Friday evening and
overspread eastern IL overnight Fri night. Widespread showers along
with some thunderstorms expected across the area Sat with plenty of
cloud cover. Isolated thunderstorms will continue Sat evening then
be confined to areas near the IN border overnight Sat night as
weakening upper level low moves into central IL by early Sunday
morning. SPC has marginal risk of severe thunderstorms far sw CWA
Sat afternoon/evening from Jacksonville to Olney sw. Mild lows Fri
night in the mid to upper 50s which is close to normal highs for
late March. Still mild Sat with highs in the mid to upper 60s, with
lower 60s from Peoria north.

Weakening upper level low lifts into central IN and nw Ohio by
sunset Sunday and keeps a fair amount of clouds over central IL
along with lingering chances of showers with highest pops over
eastern and ne CWA. A bit cooler highs Sunday in the lower 60s in
central IL and mid 60s southeast of I-70.

Dry conditions return briefly during most of Sunday night with just
isolated showers sw of Jacksonville late Sunday night. Then a good
chance of showers spreads ne across central IL during Monday as next
upper level trof moves toward the mid MS river valley by Mon
evening, with shower chances continuing Monday night. Have isolated
thunderstorms on Monday into early Monday evening south of I-72.
Highs Mon range from lower 60s nw of the IL river, to around 70F in
southeast IL.

Dry conditions expected from Tue through Wed morning as Canadian
high pressure ridge ridges southward across the western Great Lakes
and toward IL by dawn Wed. Highs Tue and Wed in the upper 50s and
lower 60s over central IL and mid 60s in southeast IL as skies
become partly sunny by Tue afternoon.

Another strong storm system ejects into the central plains on Thu
and models differ on timing and position of this storm system.
Stayed close to consensus from Wed afternoon on, with small
chances of showers Wed afternoon sw of I-74, then higher chances
of showers later Wed night into Thu. Highs Thu in the upper 50s
and lower 60s.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1218 PM CDT Thu Mar 23 2017

Main forecast issue during this period will be with the winds.
Strong low level jet will be setting up this evening, with
southwest winds increasing to around 60 knots a few thousand feet
off the ground. Have maintained the mention of LLWS at all sites,
with greatest impact near KSPI/KBMI westward. Some of this higher
wind will begin mixing down Friday morning as the strong warm air
advection continues, with gusts increasing to around 25 knots.

Have seen some brief MVFR/IFR conditions in the heavier showers
this morning, but general trend through about 12Z will remain with
mid and higher level clouds. However, models are suggesting a
surge of MVFR ceilings out of southern Illinois Friday morning.
Most likely impacts would be around KDEC/KCMI toward mid-late
morning and have included ceilings around 2500 feet in these areas
late in the period.




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