Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 281800
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
100 PM CDT SAT MAY 28 2016

.UPDATE...
Issued at 1055 AM CDT Sat May 28 2016

Forecast looked fairly good today and just a minor update to
forecast today to address chances of showers along with possible
thunderstorms this afternoon. Mostly cloudy skies and breezy SSW
winds rest of today with highs in the lower 80s and rather humid
conditions again with dewpoints in the mid to upper 60s.

Isolated to scattered mainly light rain showers had spread NNE
across eastern IL by late morning while some peaks of sunshine in
west central IL. Temps at 1030 am were in the low to mid 70s while
moist dewpoints in the mid to upper 60s. SSW winds have increased
to breezy levels by late morning, with sustained winds of 10-20
mph and gusts of 20-25 mph.

564 dm 500 mb low was along the eastern SD/NE border and models
lift this low northeast into sw MN by sunset today. 1006 mb
surface low pressure near the SD/IA/NE border with a frontal
boundary extending southward into far eastern parts of NE/KS at
late morning. Surface low to eject northeast into sw MN by early
evening and pull frontal boundary eastward into west central IL
this evening. Models show best chances of showers and a few
thunderstorms over eastern IL into early afternoon, then shifting
into western IL later this afternoon and evening with approaching
frontal boundary. Low CAPES of 200-400 j/kg at late morning
elevate to 1-2k ft from I-55 east by mid/late afternoon. Meanwhile
0-6km bulk shear of 30-40 kts this morning lowers to 20-25 kts
this afternoon. Short wave ejects northeast into western half of
IL this evening so highest chances of showers and thunderstorms
will likely be in the evening especially west of I-55 where SPC
has marginal risk of severe storms for wind and hail. Highs this
afternoon mostly in the lower 80s with a few upper 70s around
Taylorville and Shelbyville.

&&

.SHORT TERM...(Today)
ISSUED AT 339 AM CDT Sat May 28 2016

Deep southwesterly flow remains in place across the Midwest this
morning, with several subtle short-waves embedded within the flow.
Despite presence of deep-layer moisture and at least weak synoptic
lift, very little precip is currently occurring across the area.
High-res models such as the HRRR and NAM12 are suggesting scattered
showers will develop across east-central Illinois later this
morning.  Meanwhile further west, a nearly stationary frontal
boundary draped from Wisconsin to Oklahoma will begin to edge
eastward this afternoon.  Scattered showers and thunderstorms will
develop along/ahead of the front, with all models keeping the bulk
of this precipitation west of the I-55 corridor.  End result will be
a partly to mostly cloudy day with widely scattered showers and
thunderstorms.  Will therefore maintain just low chance PoPs through
the day.  High temperatures will top out in the upper 70s and lower
80s.

.LONG TERM...(Tonight through Friday)
ISSUED AT 339 AM CDT Sat May 28 2016

Complicated forecast issues remain in place for the next week or so
as the models continue to struggle with handling the pattern shifts
over the CONUS.  Showery/thunderstorm activity is more the rule than
the exception...but pinning down time frames is problematic.
Temperatures in the forecast remain more summer-like and several
degrees above normal with southwesterly flow aloft and southerly
winds at the surface continuing to feed warm air into the region.
That being said, any one days high temperatures will fall prey to
any shower/cloud activity that could dampen the diurnal curve.

Slow open h5 wave over the Plains this morning on sat imagery slowly
rotating through the broad scale trof over the western half of the
CONUS.  Southwesterly flow keeping WAA active through the region and
setting up for the potential of short wave rippling through the
region.  The models have been struggling with the current weather
pattern that is slow to shift eastward...but upping the pops
overnight tonight as the main wave passes through. Sunday will
slowly clear...but have delayed the chance pops in the far eastern
portions of the state somewhat.  For the next week... pops are off
and on as a loosely defined flow pattern sets up for parts of the
Midwest and southeastern parts of the country.  Showery activity
with a strong diurnal component expected through midweek until a low
dips into the Northern Plains/Upper Midwest, dragging a frontal
boundary expected to scour out some of the chances for a couple days
towards the end of the week.  With current model performance when
handling the active pattern so far...confidence overall in the
forecast is relatively low.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1258 PM CDT Sat May 28 2016

MVFR ceilings have mostly lifted to VFR early this afternoon
except at BMI with 2200 foot broken ceiling. Isolated light
showers from I-57 east next hour or two and have VCSH at CMI to
address this. A developing broken line of showers and
thunderstorms over southern IA into northeast MO was tracking NNE
at 35-40 mph and moving toward northwest IL. This convection
developing ahead of 1007 mb surface low pressure near the IA/SD
border. Also have a weakening 565 dm 500 mb low along the eastern
SD/NE border. Low pressure systems lift northeast into sw MN early
this evening and to spread this band of showers and thunderstorms
eastward toward PIA and SPI by 22Z...to BMI/DEC CMI by 23Z-24Z and
and to CMI from 00-02Z. Have VCTS to address this band of
convection late this afternoon and early evening over central IL.
Also have tempo groups of MVFR ceilings and vsbys for a couple
hours at western airports of PIA and SPI where thunderstorms
could be stronger with gusty winds and possible hail. Breezy SSW
winds 13-19 kts and gusts of 20-27 kts this afternoon to diminish
to 5-10 kts by mid evening. South winds this evening veer WSW
during Sunday morning at 10-15 kts.

&&

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

&&

$$

UPDATE...07
SHORT TERM...Barnes
LONG TERM...HJS
AVIATION...07


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