Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 020822
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
322 AM CDT MON MAY 2 2016

.SHORT TERM...(Today)
ISSUED AT 322 AM CDT Mon May 2 2016

While cooler/drier post-frontal air has overspread all of central &
southeast Illinois since yesterday, the threat for a few showers
will persist today. Forecast area remains on the southern side of a
sheared upper-level trof that extends from eastern Canada into the
southwestern United States. Another disturbance within this mean
flow, currently over the central Plains, will track across the area
today. Radar returns associated with this disturbance are already
tracking across Missouri and approaching Illinois. This feature will
have limited moisture to work on today as it moves through, and
limited diurnal instability is expected to develop. With this
thinking in mind, only Slight Chance PoPs and low QPF are warranted
with the passage of this disturbance. Otherwise, abundant cloud
cover and cool northerly low-level flow support cooler than normal
highs today, with most locations topping out in the 50s.

&&

.LONG TERM...(Tonight through Sunday)
ISSUED AT 322 AM CDT Mon May 2 2016

Little change indicated from previous model runs in terms of the
upper air pattern this week, with significant ridging along the
Rockies and a cold core low dropping southward through the Great
Lakes by Wednesday night. The ridge will get squeezed and shift
eastward with time, as a second upper low comes onshore of
California. A slow breakdown of the ridge will take place this
weekend as a more significant trough drops southeast through central
Canada. Although temperatures will be relatively cool for the middle
of the week, a significant warming trend will take place beginning
Friday as the thermal axis approaches from the west.

The presence of the current elongated trough from the Great Lakes to
the central Plains will continue a threat of a few showers on
Tuesday, mainly over the southeast parts of the CWA. Better chances
of scattered showers are expected Wednesday as the upper low moves
in from the north. Have increased the PoP`s late Tuesday night and
Wednesday with the main frontal boundary, with chance PoP`s as far
south as I-70 by late Tuesday night. While showers will taper for
awhile Wednesday morning as the front exits, scattered showers are
again expected in the afternoon across mainly eastern Illinois, as
the upper low arrives. Coldest air aloft will be centered over
Indiana in the afternoon, and have maintained a mention of isolated
thunder over eastern Illinois due to the steep lapse rates expected.

Late in the period, the extended models start to show some
disagreement. While the upper features are similar, with an upper
low over Colorado or eastern Utah and shortwaves rotating through
the Great Lakes, the ECMWF is further south with a surface warm
front connecting the two. This would result in scattered showers
into central Illinois Saturday night, whereas the GFS does not bring
the boundary into the area until late Sunday afternoon. For now have
mentioned only slight chances of showers and thunderstorms until
this starts to clear up a bit.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1200 AM CDT Mon May 2 2016

Tricky forecast overnight with potential for IFR/LIFR ceilings
across the entire TAF area of central and eastern IL. Plenty of
low level moisture is present in central IL and cyclonic flow is
present from a low in western Ohio, with a trough back toward SE
Iowa. Many of the short range models are advertising a solid IFR
ceiling setting up soon across the area. However, TAF sites from
SPI-DEC-CMI are on the southern edge of the low cloud shield,
which brings into question how quick the ceilings will drop and
stay down.

With the light north to northwest flow that has developed this
evening, the IFR ceilings should settle across the whole region
within the next few hours, and then stay there through much of the
morning hours. Due to the presence of continued surface troughing
and another approaching mid level shortwave trough, it will be
tough to erode the cloud cover Monday afternoon. Will also add
VCSH for the afternoon part of the TAFs with the approaching
shortwave. Should see some breaks in the clouds by evening at PIA
and SPI as the upper trough passes through the region, but in
eastern IL at least MVFR ceilings should persist through 06Z.


&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

SHORT TERM...BAK
LONG TERM...Geelhart
AVIATION...Miller


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