Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 290403
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1103 PM CDT SUN AUG 28 2016

.UPDATE...
Issued at 845 PM CDT Sun Aug 28 2016

Except for southeast Illinois where a few storms were continuing,
the bulk of the precipitation has ended. The frontal boundary that
was the primary focus for the afternoon storms was still located
over north central Illinois, while the outflow boundary from the
thunderstorm complex to our north this afternoon has shifted south
of Springfield this evening. This may be a focus for additional
widely scattered storms to develop overnight, similar to the past
several nights. A second area of concern is over southeast
Illinois where the HRRR has been consistently suggesting showers
and storms to continue at least several more hours this evening.
Precipitable water values were the highest across the north with
1.9" analyzed on the SPC mesoanalysis. The 00z ILX sounding
continues to show rather weak wind fields aloft so any storm will
be slow moving, with the primary threat being from torrential
rainfall.

Making some adjustments to POPs in the southeast counties to take
into account the ongoing convection and the potential it may
continue in that area for a few more hours. Very few changes made
further to the north overnight. We should have the updated zones
out by 900 pm.

&&

.SHORT TERM...(This evening through Monday)
ISSUED AT 252 PM CDT Sun Aug 28 2016

Slow-moving thunderstorms with locally heavy rainfall continue to
track across north-central Illinois this afternoon, with 1930z/230pm
radar imagery showing most of the activity along and north of a
Galesburg to Minonk line.  Will continue to monitor this area for
the next few hours, as training cells could produce localized flash
flooding through sunset.  Once evening arrives and daytime
instability begins to wane, the thunderstorms will diminish and come
to an end.  HRRR has been consistently showing the precip fading
away by 03z/10pm and this seems reasonable.  Main question tonight
will be whether or not additional convection forms late.  While the
HRRR remains dry through dawn Monday, the NAM suggests widely
scattered showers/thunder will re-develop over at least the western
KILX CWA.  Following a persistence forecast from the past several
nights, will trend toward the wetter NAM in this case.  As a result,
after a lull in the precip late this evening into the first part of
the overnight, have brought slight chance PoPs back into the picture
toward dawn everywhere west of the I-57 corridor.  With synoptic
frontal boundary remaining stalled just north of the area, think
scattered thunderstorms will once again develop everywhere during
the day Monday.  High temperatures will reach the middle to upper
80s, with readings around 90 along/south of I-70.

.LONG TERM...(Monday night through Sunday)
ISSUED AT 252 PM CDT Sun Aug 28 2016

A broad subtropical high pressure ridge aloft will be in place
across the southern and central U.S. by Monday evening with surface
high pressure centered over the eastern Great Lakes. A moist air
mass with 1.75-2.0 inches of precipitable water will be in place
over much of the southern and central U.S. including central IL.
Expect a chance of mainly afternoon and evening thunderstorms
Tuesday with the moist and unstable conditions. Heavy localized
rainfall from slow moving thunderstorms will be the main threat.
Highs will range from 84 in Galesburg to 88 in Lawrenceville.
Lows Monday night and Tuesday night upper 60s to around 70.

The surface high over the eastern Great Lakes...trailing a cold
front moving into the northeast U.S. tonight and Monday...will keep
a light prevailing E-NE wind across central IL through
Tuesday...although it looks that any drier air associated with the
high will not make it as far west as Illinois. By Wednesday...a deep
upper level trough amplifying into the northeast U.S. will rapidly
push out the high pressure and drive a cold front into central IL
from the north bringing much drier air of around 0.5 to 0.75 inch
precipitable water into central IL. After a chance of thunderstorms
along the front...the drier air and high pressure building into the
midwest should bring dry conditions to central IL from Wednesday
night through Saturday...along with cooler highs in the upper 70s to
lower 80s, gradually rising through the period. Lows in the upper
50s and lower 60s will be typical. Wednesday`s highs expected to
range from near 80 along the I-74 corridor to the mid 80s south of I-
70, although the high will be sensitive to the exact timing of the
front and precipitation that day.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1100 PM CDT Sun Aug 28 2016

Main forecast concern continues to be with the potential
for MVFR vsbys in fog in the 09z-13z time frame. Most of
the showers and thunderstorms have dissipated this evening
except for areas well to our southeast. Copious low level
moisture, light winds and a mostly clear sky should lead
to at least some patchy shallow fog early Monday morning.
Like yesterday morning, we may see some brief MVFR cigs
develop as well after 09z but both the fog any any lower cigs
should lift by 15z with low VFR cigs developing by afternoon as a
cumulus deck in the 3000-4000 foot level quickly develops. Can`t
rule out a TSRA again during the early morning hours but coverage
will be too small to include in the TAFs at this time.

The atmosphere will be quite unstable again Monday afternoon so
widely scattered thunderstorms are again possible during the
afternoon and early evening hours. will include VCTS in this set
of TAFs in the 19z-00z time frame. Winds will again be quite
light thru the night and east to southeast on Monday at 4 to 9
kts.

&&

.CLIMATE...
Issued at 252 PM CDT Sun Aug 28 2016

As of noon today Springfield has reached the 2nd wettest summer on
record with 21.43 inches of precipitation since June 1st. The
wettest summer on record was in 1981 when 24.93 inches fell from
June-August.

&&

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

$$

UPDATE...Smith
SHORT TERM...Barnes
LONG TERM...Onton
AVIATION...Smith
CLIMATE...Onton


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