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Area forecast discussion 
National Weather Service Lincoln Illinois
324 am CDT Wednesday Jul 8 2015

Short term...(today)
issued at 324 am CDT Wednesday Jul 8 2015

1021mb high pressure over the Great Lakes has brought a cooler/drier
airmass into much of central Illinois early this morning...as
evidenced by 08z/3am dewpoints only in the lower to middle 50s.
Further southwest...an area of low pressure is developing along a
stationary frontal boundary over southern Oklahoma. The low is
expected to track slowly northeastward today...reaching Saint Louis
by early evening. Latest radar mosaic and surface observation already show
light showers moving northward into west-central Illinois...however
precipitation will be fighting a dry NE flow as it tries to work its way
further northward this morning. Most high-res model guidance keeps
the showers south of the I-74 corridor until closer to midday. As
the airmass moistens...showers will eventually overspread all of
central and southeast Illinois by afternoon. Forecast soundings
show only meager elevated instability today...so thunder should be
at a minimum. Have therefore only mentioned isolated thunderstorms
mainly across the southern two-thirds of the kilx County Warning Area. Flash Flood
Watch currently in effect across all of central and southeast
Illinois will continue for today and tonight...although heaviest
rainfall will be delayed until late afternoon into tonight. Due to
extensive cloud cover and showers...high temperatures will remain
well below normal for this time of year in the 60s. In fact...these
readings will likely break previous records for lowest maximum
temperature for the date by several degrees.

&&

Long term...(tonight through tuesday)
issued at 324 am CDT Wednesday Jul 8 2015

Rain will continue across the entire area tonight...as low pressure
tracks across The Heart of central Illinois into northern Indiana by
early Thursday morning. With this particular track...locations
along/south of the I-70 corridor will punch into the warm sector of
the system. Increasing surface-based instability across this area
could result in a few strong thunderstorms during the evening hours
as suggested by the 4km NAM. Have therefore hit thunder harder
across the southeast County Warning Area tonight...with just isolated mention
elsewhere. Total rainfall today/tonight will generally range from 1
to 1.50 inches...but will be lighter northwest of the Illinois
River. Isolated higher amounts will be possible within
thunderstorms.

Once the low lifts to the northeast...short-wave ridging in its wake
will lead to a mostly dry day on Thursday. Have hung on to slight
chance probability of precipitation across the east during the morning hours in case a few
showers linger...with dry conditions across the board during the
afternoon. Another round of showers and thunderstorms will develop
late Thursday night into Friday as another upper wave approaches
from the southwest and a warm front lifts northward into the region.
Strongest warm air/moisture advection will be focused across
northern Missouri/southern Iowa...so have gone with likely probability of precipitation west
of I-55 overnight accordingly. Further east...probability of precipitation decrease to just
low chance along the Indiana border. Rain chances will continue
throughout the day Friday...with highest probability of precipitation gradually shifting
north of the I-74 corridor by afternoon.

Upper-level ridging will temporarily build into the Midwest this
weekend...however exact strength of ridge remains in question. It
still appears the ridge will be pronounced enough to keep the main
storm track across the southern Great Lakes for Saturday and
Sunday...resulting in a hot and mostly dry forecast. Will carry low
chance probability of precipitation across the northern County Warning Area Saturday night as nocturnal
convection may build far enough south to impact locations from the
Peoria area northward. Better rain chances will hold off until
Monday and Tuesday...when the ridge shifts further westward and a
deep trough digs over the Great Lakes/Midwest.

&&

Aviation...(for the 06z tafs through 06z Wednesday night)
issued at 1155 PM CDT Tuesday Jul 7 2015

Rain showers have temporarily shifted south of the central Illinois taf
sites while large breaks in the low clouds from central Illinois NE.
6-8k feet ceilings at spi and Dec while ceilings drop off to
1.5-4.5k from Macomb to Litchfield to Effingham SW. These lower
clouds along with some light rain showers will spread back NE
across central Illinois during overnight...reaching spi in 1-2 hours and
to I-74 late tonight. Hrrr and rap models have trended 1-2 hours
quicker with rain showers spreading back NE but hesitant about
this due to lower dewpoints in low to middle 50s that has advected
into central Illinois on NE flow. Eventually brought in IFR to low end
MVFR ceilings later tonight or Wednesday morning with visibilities 2-4 miles in
rain showers during Wednesday and Wednesday evening. Frontal boundary had
pushed south toward the Ohio River and southeast MO and extended to weak
1012 mb surface low pressure near Texas/OK border. Low pressure to
track NE across central Illinois during Wednesday evening with widespread
light to moderate rain shower expected Wednesday/Wednesday evening. Best
chance of thunderstorms appears to be south of I-72 (south of low
pressure track) so will keep thunder mention out of tafs for now.
East-northeast winds generally less than 10 kts to prevail next 24 hours.



&&

Ilx watches/warnings/advisories...
Flash Flood Watch from 7 am CDT this morning through Thursday
morning for ilz027>031-036>038-040>057-061>063-066>068-071>073.

&&

$$

Short term...Barnes
long term...Barnes
aviation...07

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