Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 200545

Area Forecast Discussion
National Weather Service Lincoln IL
1145 PM CST Fri Jan 19 2018

Issued at 905 PM CST Fri Jan 19 2018

Cirrus clouds of varying thickness will continue to stream across
central Illinois overnight. The clouds, in combination with steady
SW winds, will work to limit the diurnal temp falls tonight. A
brisk 50-55KT LLJ has actually created some sizable wind gusts
this evening, with varying degrees of de-coupling occurring across
the area. Once again, our coolest readings are in the east, where
some snow cover survived today`s warm-up. Plenty of warm air
surging northward through Missouri and into far western Illinois
give support for lows to end up above current forecast numbers,
mainly in the western counties. Have adjusted lows up slightly
west of I-55, and increased the sky cover in a majority of the
area due to the thickness of the cirrus.

Also increased gusts for the rest of the evening to account for
some speeds reaching near 30 mph at times. The rest of the
forecast looks on track.


.SHORT TERM...(This evening through Saturday)
ISSUED AT 255 PM CST Fri Jan 19 2018

More quiet and warm weather continues tonight and into tomorrow.
However, along with the warmer weather tomorrow, low level
moisture will stream up into the area tomorrow and bring overcast
skies by the afternoon. This should not reduce the warming since
waa from the southwest will be coming up with the moisture. Temps
tonight are expected to be right around freezing while temps
tomorrow afternoon should be similar to today, but a tad lower
because of the clouds. Even though some models are spitting out
some qpf, confidence is not high enough for me to put it in at
this time.

.LONG TERM...(Saturday night through Friday)
ISSUED AT 255 PM CST Fri Jan 19 2018

Low level moisture and will continue to stream into the CWA Sat
night ahead of the next weather system. With the pattern becoming
more amplified with a ridge across the eastern half of the US and
a trough across the west, the low pressure area associated with
the next weather system is expected to move northeast toward the
northern Great Lakes region and remain west and northwest of our
CWA. Areas of fog will develop Sat night and along with this,
drizzle will be possible since lots of low level moisture and waa
over the area. The drizzle will become showers as the system gets
closer to the area Sunday into Sunday night. Highest pops will be
Sunday night and Monday as the low tracks northeast across eastern
IA. Thunder might be possible Sun night with the main low and
along the cold front, but instability is relatively week and may
be confined south of the not adding in at this
time...will take a look again tomorrow. All models show a decent
dry slot coming in behind the cold front so expecting a break in
precip on Monday, but timing is tricky this far out, so will not
try to put this feature into the grids just yet. Then the wrap-
around precip of the system will move through the area Monday
night. Precip should go from rain to mix of rain/snow to all snow
before ending. Any snowfall in the are will be minimal.

Beyond this weekend system, dry weather is expected across the
CWA through the mid week as the flow becomes zonal/northwest for a
brief period. Then ridging is expected to return for the end of
next week into the following weekend.

Temps will remain warm through the weekend and into Monday. Then
expect temps to drop, but still remain above freezing during the
daytime hours. Warm temps expected at the end of next week and
into that weekend.


.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1144 PM CST Fri Jan 19 2018

LLWS conditions will continue through 14z, with a strong southwest
LLJ across central IL. Southwest speed maxima has climbed between
50-55KT in the 1500-2000FT layer, affecting all our terminal
sites. The LLJ weakens Saturday morning, as MVFR and IFR clouds
rapidly advance from SW to NE across the area. Cloud heights look
to drop directly to 1200FT around 14z, with IFR to 800FT mixed in
with the initial push of clouds. While mixing will diminish
somewhat with the stratus layer arrival, sustained winds look to
maintain in the 10-14KT range from the S-SW. Any IFR conditions
that do develop in the morning, should improve up to MVFR during
the afternoon as steady warm air advection flows increase the
LCL`s. Slight chances of rain look to begin Saturday evening, in
the broad warm advection pattern. Any rainfall amounts during the
last 6 hours of this TAF period will be very light, so only VCSH
was included at this point. MVFR fog could begin to develop as
winds weaken tomorrow evening.




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