Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 300521
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1221 AM CDT Tue May 30 2017

.UPDATE...
Issued at 837 PM CDT Mon May 29 2017

Convergence along a slow moving frontal boundary from around Paris
to Shelbyville, combined with a shortwave trough aloft caused
widely scattered showers and isolated thunderstorms from near St.
Louis into east central IL and Indiana this evening. The shower
and thunderstorm activity is now settling southward and eastward
and should be out of the central IL forecast area by 10 p.m. which
matches well with the afternoon forecast package. Updates this
evening were mainly to adjust earlier development slightly
northwestward. With slightly cooler and drier air in place today
compared with yesterday, lows should drop lower tonight. Expect
around 50 in Galesburg ranging up to 57 in Lawrenceville.

&&

.SHORT TERM...(This evening through Tuesday)
ISSUED AT 305 PM CDT Mon May 29 2017

A slow-moving cold front and vorticity max will push across the
southeast portion of our forecast area the rest of the afternoon
into this evening. While no showers have developed to this point,
the high res models are all pointing toward isolated
showers/storms developing along the boundary late this afternoon
into early evening. MUCAPEs of 1000 J/kg should be sufficient for
that to occur. Have lingered low chance/slight chance PoPs along
and south of I-70 early this evening. Subsidence in the post-
frontal airmass should set up mostly clear and seasonable
conditions for the remainder of the night. Low temps should
settle out in the low to mid 50s.

Tuesday should start out sunny, but afternoon conditions will turn
more cloudy with spotty showers/storms developing ahead of the
next trough/cold front. Once again, the front will be moisture
starved. There will be limited instability in the 500-800 J/kg
range, but bulk shear of 50-60KTS will be a catalyst toward storm
development along the front. Have included slight chance PoPs
Tuesday afternoon along and west of I-55. Enough morning into
early afternoon sunshine should push high temps into the low 70s
north of I-74, with upper 70s south of I-70.

.LONG TERM...(Tuesday night through Monday)
ISSUED AT 305 PM CDT Mon May 29 2017

The extended forecast will be primarily influenced by a long wave
trough across eastern Canada and the eastern half of the lower 48.
An upper low centered over NW Ontario will pinwheel north and then
south again over the next several days, setting the stage for
periods of showers and storms. Tuesday night will see a cold front
depart through the southeast half of our forecast area, triggering
showers/storms for areas SE of the Illinois River.

Wednesday and Wed night look to be a dry period, as high pressure
passes across Illinois, bringing our coolest temperatures of the
next week. Highs Wed will be a couple degrees cooler than Tues,
but still mainly in the 70s. Wed night lows will mirror Tuesday
night, with low 50s north and upper 50s south.

Once the high shifts off to the east, a warm front will lift
northward into the area on Thursday. The extended models continue
to point toward an MCS developing across the Plains Wednesday
night, then tracking E/SE toward central Illinois by Thursday
morning. The ECMWF, GFS, and NAM all generally show the wave
arriving Thursday morning, then weakening as it pushes across
Illinois during the day. Despite marginal synoptic forcing, the
presence of a warm front across Illinois warrants at least chance
PoPs Thursday into Thursday evening. There are indications of a
break in the rain from midnight Thursday to Noon on Friday.

The warm front will continue a slow progression northward Friday
night into Saturday, putting our area firmly in the warm sector.
Isolated to scattered showers/storms are in the forecast for
Saturday into early Sunday due to low pressure moving east along
the front and passing across northern Illinois Sunday morning. A
break in the rain looks to close out the extended forecast Sunday
afternoon through Monday as high pressure arrives behind the
departing low.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1221 AM CDT Tue May 30 2017

VFR conditions to continue the next 24 hours. Only issues of
consequence for the TAF`s are some west winds gusting to near 20
knots late morning into the afternoon, as well as some isolated
convection late afternoon as a weak boundary settles into the
area. Right now will only mention VCTS at KPIA/KBMI, as the
boundary arrives further south as diurnal heating is lost.

&&

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

$$

UPDATE...37
SHORT TERM...Shimon
LONG TERM...Shimon
AVIATION...Geelhart



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