Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 201730

Area Forecast Discussion
National Weather Service Lincoln IL
1130 AM CST Mon Nov 20 2017

Issued at 1100 AM CST Mon Nov 20 2017

High pressure to the southeast of Illinois will maintaining its
influence on our weather today, with just high cirrus clouds and
ample sunshine. The tight pressure gradient and southwest low
level jet are providing the forcing for gusty S-SW winds today.
Sustained winds will hover around 20 mph, with gusts to 35 mph at
times. The bufkit profiles and HRRR output point toward the gusts
becoming less intense after 3 pm this afternoon, but high profile
vehicles could see some difficult travel on east-west roads this
afternoon. Temps are well on their way to reach above normal
levels, boosted by near full sun and gusty south winds. The
warmest readings will be in our western counties, with cooler
highs in our NE counties along the Indiana border. Updates this
morning were minor, and mainly to sky conditions. Updated info is
already available.


.SHORT TERM...(Today and tonight)
ISSUED AT 345 AM CST Mon Nov 20 2017

09Z/3 am surface map shows 1025 mb high pressure over the TN river
valley and ridging into the southeast Ohio river valley. 991 mb
low pressure was over southern Saskatchewan. SSW winds were
gradually increasing to 7-15 mph over central IL as pressure
gradient increasing between these two weather systems. Nearly
steady or even slowly rising temperatures in the upper 20s to mid
30s, with coolest readings east of I-57 where winds were lighter.
Some bands of cirrus clouds were spreading se across IL and nearby
states in WNW upper level flow pattern across the country.

High pressure to drift over the Carolinas this afternoon while low
pressure moves ESE into southwest Ontario by sunset and continues
to increase pressure gradient over area today. A partly to mostly
sunny day today as cirrus clouds continue to stream across with
filter sunshine. Breezy sw winds of 15-20 mph and gusts of 25 to
30 mph by afternoon to bring milder temperatures back to the area
today. Highs in the lower 50s over east central CWA and upper 50s
to around 60F from Springfield sw.

Low pressure deepens to 987 mb as it tracks eastward across
central Ontario province during tonight, pulling a cold front se
toward the IA/IL border by 12Z/6 am Tue. Increasing clouds tonight
especially nw of I-70 and sw breezes to keep temps up tonight.
Lows of 35-42F, mildest over west central IL, from Springfield

.LONG TERM...(Tuesday through Sunday)
ISSUED AT 345 AM CST Mon Nov 20 2017

Generally quiet/dry weather expected over area from Tuesday
through Thanksgiving weekend as primary storm track is north of
our area. Cold front still expected to pass through dry during
the day Tue as it presses se across IL. Moisture is quite limited
over area with this frontal passage, with deeper moisture tied to
the Gulf coast area and also ne of CWA where better lift closer to
low pressure system passing north of the Great Lakes region.
Slight chances of light rain showers just ne of Vermilion
county/Danville area on Tue afternoon. Highs Tue range from the
mid 40s along and nw of the IL river, to near 55F by
Lawrenceville. Brisk nw winds behind the cold front Tue afternoon
to cool temperatures into the mid to upper 30s by late Tue
afternoon over central IL and low to mid 40s in southeast IL.

NW winds bring in much colder lows in the low to mid 20s on Tue
night as skies clear in the evening and nw winds diminish during
the night as Canadian high pressure settles into the central
plains by sunrise Wed. High pressure to ridge across central IL
and into the Ohio river valley by sunset Wed bringing a fair
amount of sunshine and lighter winds, but cold highs of 35-40F,
similar to what we experienced yesterday. Lows Wed night in the
mid 20s, with some upper 20s western CWA. Highs Thu/Thanksgiving
Day in the lower 40s ne CWA and upper 40s sw CWA with partly to
mostly sunny skies.

High pressure ridge drifts over the southeast states on Friday and
increasing SSW winds to warm temperatures into the 50s, similar to
what we are expecting today, with clouds increasing from the nw
especially by Friday afternoon. A stronger area of low pressure
about 982 mb tracks eastward across central Ontario Friday night
and pulls another cold front se across IL. This front too appears
to mostly pass through dry, though do have 20-30% chance of light
rain showers NE CWA Friday evening. Highs Saturday range from
45-55F, coolest at Galesburg and mildest at Lawrenceville as
cooler air starts to filter in behind the cold front on nw breezes.
Chilly on Sunday with highs in the mid 30s to around 40F as
Canadian high pressure settles over IL by sunset Sunday, and in
the low to mid 40s next Monday as dry weather persists.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1130 AM CST Mon Nov 20 2017

The 18Z TAF period will be highlighted by strong S-SW winds.
Mixing heights are favorable to mix some of the 45-50KT LLJ down
to the surface. Main gusts near the terminal sites looks to remain
down toward 30kt, but we can not rule out a couple of higher gusts
through 22z. Strong winds will continue overnight, but the LLJ
will remain strong as well. Therefore, we kept the mention of LLWS
at all terminal sites tonight. WS015/23050kt. 1500Ft level seems
to be the base of the LLJ, with winds at that level around 50kt.

No significant clouds of not are expected, with just some AC
tomorrow with the passage of the cold front.

Winds will shift from S-SW to the W by late morning, in response
to the impending FROPA. Gusts tomorrow will be less intense than
today, with peak gusts mainly around 20-22kt.




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