Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 260146

Area Forecast Discussion
National Weather Service Lincoln IL
846 PM CDT Fri May 25 2018

Issued at 839 PM CDT Fri May 25 2018

Updated forecast a little while ago to better reflect shower/storm
coverage associated with a mesoscale convective vortex that is
currently tracking east-northeast across the forecast area. This
feature should move east of the area over the next few hours. This
fact, as well as the loss of diurnal instability, should continue
to trend precipitation chances downward. However, will continue to
monitor the strong-severe cluster of storms diving southeast
across southwest Wisconsin/northeast Iowa. At its current
trajectory/speed, these storms would reach far northern portion of
the forecast area around Midnight. Some high-resolution guidance
suggests they will make it this far. However, other guidance
suggests the storms will fall apart before getting here. The
storms will be moving off an axis of stronger instability shortly,
and into an environment with weaker forcing. Following the more
optimistic forecast of the storms falling apart at this time when
considering all factors, but will continue to monitor trends.

Aside from the PoP adjustments, only minor hourly tweaks were
needed to most other elements overnight.


.SHORT TERM...(This evening through Saturday)
ISSUED AT 315 PM CDT Fri May 25 2018

An MCV center near St Louis has bands of showers and thunderstorms
west of I-55, with another band of convection spreading ne across
sw IL along I-64. A few strong to severe storms with heavy rains
too over IL and MS river valleys of nw IL. Another very warm and
more humid day over central IL. Temps were in the mid to upper
80s, except rain cooled 70s over the IL river valley. Dewpoints
range from 50s over eastern IL, to the mid 60s to around 70F from
Peoria and Springfield west.

Remnants of MCV to drift east across central IL during late
afternoon and evening, and spread scattered showers/thunderstorms
into eastern IL late this afternoon and early evening. SPC has a
marginal risk of severe storms into early evening as far east as a
Danville to Effingham line with gusty winds and hail possible.
Locally heavy rains and frequent lightning also possible with
stronger thunderstorms. Altona in northern Knox county had 1.05
inches of rain in about an hour early this afternoon. Any
remaining convection will diminish east of the IL river during
overnight as airmass stabilizes and MCV remnants moves into IN.
Milder lows overnight in the mid to upper 60s as dewpoints will be
higher tonight than past several nights.

Not much lift in wake of the MCV east of IL on Saturday, but
airmass gets unstable again especially in the afternoon, and in
response isolated showers and thunderstorms could develop. Very
warm Saturday with highs in the upper 80s in eastern IL and around
90F along and west of I-55. Afternoon heat indices peak from

.LONG TERM...(Saturday night through Friday)
ISSUED AT 315 PM CDT Fri May 25 2018

Summertime pattern to continue from this holiday weekend through
at least the end of next week. Upper level ridge building over IL
Sunday and Monday to bring even hotter conditions with highs in
the low to mid 90s and afternoon heat indices in the 90s Sun/Mon.
This will approach record highs in the mid 90s on those 2 days.
Generally dry conditions prevail, though can not completely rule
out an isolated afternoon/early evening thunderstorm especially
over the Wabash river valley.

Subtropical Storm Alberto off the east coast of the Yucatan
Peninsula will lift northward across the gulf of Mexico through
Monday and strengthen to a strong tropical storm. NHC has it
reaching near the LA delta/MS coast Monday night, then lifting
into the TN river valley on Wed and curving ne over the ohio
river valley Wed night. Clouds to increase from the south on Tue
with isolated convection possible later Tue especially in
southeast IL. Highs Tue in the upper 80s and lower 90s and
afternoon heat indices of 90-95F. This system will be closest to
southeast IL on Wed and have the highest pops then, ranging from
30% in central IL and 40-50% in southeast IL. Highs in the mid to
upper 80s on Wed, likely coolest in southeast IL where more clouds
and higher rain chances. Isolated convection could linger Thu
especially in southeast IL. Models build upper level ridge back
into area later next week and in response, temperatures to rise
back into the upper 80s Thu and around 90F or lower 90s next Fri.


.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 647 PM CDT Fri May 25 2018

A cluster of showers and thunderstorms making its way across
central Illinois at the moment, but it should depart within the
next couple of hours. Then, another shower or storm can`t be ruled
out for the next several hours, but coverage will be too low to go
above a VCSH mention. VFR condtions should prevail for much of the
period, although some model guidance patches of low-end MVFR CIGs
between about 06Z and 12Z tonight. Have not included these CIGs
at this time, but trends will need to be watched. Light winds are
expected for most of the period, outside of any thunderstorms
early this evening.




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