Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 201545
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1045 AM CDT WED JUL 20 2016

.UPDATE...
Issued at 1038 AM CDT Wed Jul 20 2016

Made some minor tweaks to the forecast for the trends of the
current convection working its way through west central IL.

The latest surface analysis indicated a nearly stationary front
from western IA into central and southeast MO. Elevated showers
and thunderstorms have resulted from eastern IA into west central
IL. The rainfall is moving somewhat slowly and training over some
areas as the main area slowly oozes eastward. Have mention of
locally heavy rain in the forecast from GBG-SPI and points west.

Still expecting scattered showers and t-storms to persist through
the afternoon, but with a gradual weakening trend as the airmass
in central/east central IL has much less instability. Temperatures
will take awhile to recover, but still expecting highs in the
upper 80s to lower 90s as the clouds break up in western and
central IL later this afternoon.


&&

.SHORT TERM...(Today and tonight)
ISSUED AT 306 AM CDT Wed Jul 20 2016

Remnants of early MCS is finally moving off to the east of the area
but cloud cover remains over the area early this morning. This cloud
cover has hampered fog development, even with the light winds. So
will not have any fog mentioned in the forecast for early this
morning.

Short-term/HiRes models continue to show development of showers and
thunderstorms this morning along a warm frontal-type zone, but
mainly in the west and central parts of the cwa, and specifically in
the morning through early afternoon. Based on the models, this pcpn
dissipates during the afternoon hours and doesn`t reach the eastern
parts of the CWA. So, will have a chance pops for this morning in
the west and central and continue it into the afternoon hours, but
decrease it into the slight chance category for the afternoon and
into the evening. Will keep a slight chance in the far east for the
overnight hours, while the remainder of the CWA should be dry
overnight.

Temps will be quite warm again today, reaching into the lower 90s in
the west, while still remaining in the mid to upper 80s in the east
and northeast. Dewpoints should push back into the mid 70s by this
afternoon, resulting in HI over 100 over most of the area. Western
areas of the CWA could see advisory criteria being reached, 105, but
only for an hour or two. Therefore will not be making any changes to
current headlines.

.LONG TERM...(Thursday through Tuesday)
ISSUED AT 306 AM CDT Wed Jul 20 2016

Primary focus remains with the heat into the weekend, as massive 598
dm upper high switches to more of a west-east configuration this
weekend. Associated cold front which will bring some relief is not
expected to reach the area until Sunday, as the upper low currently
off the Washington coast opens up and tracks along the Canadian
border this weekend.

No changes being planned for the Excessive Heat Watch yet, but an
upgrade to a warning or advisory will soon be needed. Main concern
is the duration of the peak heat indices. Local warning criteria
calls for 110+ peak heat index for 2 days with nighttime heat index
at least 75F. Friday still is fairly solid in that potential, but
Thursday and Saturday are a bit more iffy and dependent on any
convective cloud debris to our north. Latest guidance suggests areas
east of I-55 may still have 105+ heat index as late as Sunday, which
would satisfy the alternate criteria of 105+ heat index for at least
4 days, but scattered storms are more of a potential with the front
and so this level of heat is more uncertain.

In terms of the actual temperatures, went a bit above MOS guidance
for Thursday as forecast soundings indicate high temperatures in the
mid 90s as far north as Peoria, and went closer to a NAM/GFS MOS
blend for Friday. Temperatures at least in the lower 90s are still
likely into the weekend, before the front passes and more tolerable
mid-80s highs returns early next week.

Main time frame for any showers/storms is mainly this weekend,
especially Sunday as the front arrives. Mid-level capping may break
enough on Saturday for a few storms to form, but main focus will be
on Sunday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 643 AM CDT Wed Jul 20 2016

Thunderstorms have developed in western IL along an elevated warm
front. As this front lifts north, these storms could continue and
effect all TAF sites this morning and into early afternoon. So
will have VCTS at all sites to cover this. As the front lifts
north, additional storms could develop later this afternoon and
effect PIA and BMI. So will have PROB group for these two sites
for late afternoon into the evening hours. Other three sites
should see just high cirrus during the evening time period. Once
any additional storms move north, cirrus will be seen at PIA and
BMI during the evening as well. Winds should be southerly through
the period.


&&

.ILX Watches/Warnings/Advisories...
Excessive Heat Watch from Thursday afternoon through Saturday
evening for ILZ027>031-036>038-040>057-061>063-066>068-071>073.

&&

$$

UPDATE...Miller
SHORT TERM...Auten
LONG TERM...Geelhart
AVIATION...Auten


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