Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 281546

Area Forecast Discussion
National Weather Service Lincoln IL
1046 AM CDT Wed Jun 28 2017

Issued at 1045 AM CDT Wed Jun 28 2017

Updated forecast to increase chances of showers and thunderstorms
today further southeast across the IL river valley. Peoria airport
recently had a thunderstorm with heavy rain. Convection from MCS
this morning has been confined to areas from Peoria north and
tracking ENE toward the Chicago metro. Also increased SSW winds
today which have already been gusting 20-28 mph north of I-70.
Warmer and more humid today with highs in the lower to middle
80s. Dewpoints currently ranging from 55-60F in eastern IL to
60-65F in western IL, will climb into the low to mid 60s during
the afternoon, highest over the IL river valley.

Late morning surface map shows 996 mb low pressure near the
MN/ND/SD border and its cold front through central Nebraska and
western KS. 1025 mb high pressure was over the western Virginia.
Pressure gradient has been tightening up over central IL causing
SSW winds become breezy during this morning. South winds 10-15 mph
over southeast IL not quite as gusty yet, but will become gusty in
the 20s during this afternoon with gusts up to 30 mph over central
IL. SPC day 1 outlook continues slight risk of severe storms nw of
IL river for tonight, mainly overnight with marginal risk as far
se as I-55. The enhanced risk was from the Quad cities nw into se
half of Iowa closer to frontal boundary. 996 mb low pressure to
track east to nw WI/Lake Superior area this evening and pull cold
front eastward toward central IA. The convection from Peoria north
should diminish next few hours as MCS weakens. More widespread
convection to develop during afternoon/evening nw of CWA and move
into IL river valley overnight.


.SHORT TERM...(Today and tonight)
ISSUED AT 318 AM CDT Wed Jun 28 2017

With the high pressure ridge over the eastern CONUS, the Midwest
is moving into an unsettled warming trend, with showers and
thunderstorms expected through the end of the week. At 500mb, the
northwesterly flow is giving way to a slightly more zonal
regime...with a strong wave over the Plains states this morning
resulting in an MCS already over IA. HRRR is already about 2 hrs
behind. However, the storm is expected to move north of the FA for
the first half of the morning. Have sped up the onset of precip
and thunder in the NW a couple hours just to cover some of the
more discrete cells that has formed ahead of the main lines of
storms, as the HRRR is indicative that that activity may continue.
The bulk of the precip and storm threat is confined to the
northern tier of the state for today...edging towards Peoria,
particularly this afternoon. Later this evening, the precip
chances begin to spread southward. Warm air continues to move into
the region with an increasing pressure gradient resulting in
strong southerly winds through the day. Gusts will extend to the
evening hours as well with such turbulence in the boundary
layer...and keep the temperatures above climatological norms

.LONG TERM...(Thursday through Tuesday)
ISSUED AT 318 AM CDT Wed Jun 28 2017

The shift to a more zonal flow across the country opens the
region to the deep warm air over the desert SW. 850 mb temps warm
quickly today, and remain in place through the end of the week.
Even though the temps cool a few degrees at the midlevels for the
weekend as a quick wave rotates around the trough over the Great
Lakes, the difference at the surface is negligible. Temperatures
by and large will oscillate between highs in the 80s and lows in
the 60s through the end of the forecast. Cloud development and
storms through the end of the week will be producing enough
mesoscale impacts with boundaries of rain cooled air and pockets
of more efficient daytime heating to create a mask over potential
detail in the forecast. Generally speaking, southerly flow across
the region will feed warm temps and plenty of moisture into the
region as fuel for potential convection. A weak developing
boundary will provide some focus as the boundary settles into the
Midwest. Models have a bit of agreement at this point with
bringing the next wave and a potential MCS to interact with the
boundary already in place for the end of the week, Thu night thru
Friday. Thursday (Day 2) has Central IL in a slight risk... and
Friday (Day 3) in a marginal. Increasing instability invof a
boundary and interactions with other outflows...good shear to
40-50 kts in the midlevels...threat for severe weather will linger
over to Friday and/or until the focus shifts. Weekend not
necessarily in the clear, but chances drop briefly as the boundary
drifts south. Not much of a more stable airmass ends up giving way
quickly to the next wave/system moving in out of the Southern
Plains for the first of the work week.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 548 AM CDT Wed Jun 28 2017

VFR throughout for now. Increasing pressure gradient will result
in prolonged gusty southerly winds on this side of the ridge well
into this evening. Scattered shower and thunderstorms will move
in NW of the IL River and PIA later this evening. Have delayed
mention of thunder until around 04z, but started VCSH earlier. It
is expected to be a slower progression to the south...but starting
trend for VCTS for PIA SPI and BMI...holding in VCSH for CMI and
DEC for now. Cirrus and mid level clouds...increasing as
convection moves in. Winds becoming increasingly southerly...
around 16-22 kts with gusts 25-30 kts.




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