Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 160306
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
906 PM CST Wed Nov 15 2017

.UPDATE...
Issued at 906 PM CST Wed Nov 15 2017

Updates mainly for cloud cover associated with a cold front moving
into northern IL this evening. An area of low cloudiness looks to
skirt along I-74 and areas northward starting late this evening
and continuing perhaps a few hours after midnight. Otherwise, Lows
generally in the upper 20s are expected, as colder air pushes in
behind this front. Breezy and gusty winds can also be expected
behind this front, with a period of 15-20 mph NW winds and gusts
into the 20s in the cloudy areas.

&&

.SHORT TERM...(This evening through Thursday)
ISSUED AT 240 PM CST Wed Nov 15 2017

The cold front that pushed across the area today should be well
off to our east this evening with high pressure forecast to track
southeast into our area by Thursday morning. However, in the low
level cyclonic flow in the wake of the front, a rather large band
of clouds were tracking southeast out of central Iowa and will
affect at least the northern part of the forecast area overnight.
Forecast soundings suggest Peoria and Bloomington stand the best
chance for seeing a period of cloudiness this evening into the
overnight hours before surface high pressure settles into the area
Thursday morning bringing quiet weather for the day. Lows tonight
should drop off into the upper 20s to lower 30s with afternoon
highs on Thursday expected to top out in the middle 40s.

.LONG TERM...(Thursday night through Wednesday)
ISSUED AT 240 PM CST Wed Nov 15 2017

High pressure will push off to our east Thursday night allowing a
return flow to set up, especially across the western half of the
state. This should bring the coldest temperatures to the east
late Thursday night while readings across western IL will hold
mostly in the mid to upper 30s. Our next weather system will take
shape later on Friday with a strong southerly flow in advance of
the storm system during the day which should help push afternoon
temperatures well into the 50s over west central Illinois. With
the strong southerly winds during the day, we may see a stratus
deck move up from the south and that may have an impact on
afternoon temperatures, but for now, will continue to go with
the warmer guid values across the west despite the possible
cloud cover. In addition, some drizzle of light showers may
develop as well with the strong low level warm advection pattern
noted on the latest NAM/ECMWF models as early as Friday morning
with some low chance POPs continuing over parts of the forecast
area. Forecast soundings off the NAM and ECMWF suggest more of
a daytime threat for light precip but the stronger dynamics with
this system still appears to be holding off until Friday night
into Saturday morning.

As the frontal system and upper dynamics approach our area Friday
night into Saturday morning, a more widespread rain event will
unfold with isolated thunder. Models still depicting meager
elevated instability across our area through Saturday morning
with some increase in MUCAPEs over far southeast Illinois after
12z Saturday. A typical cool season low cape/high shear system
pushing through late Friday into Saturday, with little in the
way of lightning with the showers. Bufkit soundings off the NAM
12z model showing 45 to 55 kt winds from around 2500 to 5000 feet
AGL Friday night into early Saturday, so any stronger updrafts
that may develop in the band of showers may be capable of
producing an isolated strong wind gust, if it can break through
the persistent low level inversion in place. The fact that the
frontal passage and stronger dynamics are arriving late Friday
night into Saturday morning will keep any threat for stronger
storms limited across our area.

Once the front shifts off to our east Saturday morning, strong
northwest winds, with gusts up to 40 mph possible, will usher in
colder temperatures during the day with steady or slowly falling
temperatures as we head through the afternoon hours. The steadier
rains and any isolated convection should push off to our east
by late morning or early afternoon but with the 500 mb trof axis
still to our west, we still can`t rule out some lingering shower
activity, especially across eastern Illinois Saturday afternoon.
Cold temperatures will be the rule for the rest of the weekend
with Saturday night`s lows in the low to mid 20s with highs on
Sunday struggling through the 30s. Temperatures should then begin
to moderate some early next week as the deep upper trof shifts off
to our east and upper level heights begin to rise over the region.
However, any warmup should be short-lived as another strong
shortwave is forecast to deepen in over the Great Lakes next
Tue/Wed which should bring a cold front across our area later
Tuesday. Moisture ahead of this feature looks rather limited at
best as any feed of Gulf moisture will be tied up with an upper
level low which is forecast to cut-off over Texas late Tuesday
into Wednesday. Another chilly Canadian air mass will be poised to
track southeast into our area on Wednesday and Thanksgiving day
keeping temperatures at or slightly below normal.

&&

.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 530 PM CST Wed Nov 15 2017

A cold front and associated MVFR cigs and gusty winds moving into
NW IL early this evening will be the main feature for central IL
over the next 24 hours. Expecting this feature to affect KPIA-
KBMI-KCMI northward from around 02Z to 06Z, while to the south KSPI-
KDEC remain clear and less gusty. Otherwise, winds will be NW for
most of the next 24 hours, generally under 12 kts with a
decreasing trend. Late afternoon Thursday may see winds become
light and variable as a high pressure ridge axis moves over the
area.


&&

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

$$

UPDATE...37
SHORT TERM...Smith
LONG TERM...Smith
AVIATION...37



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