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Area forecast discussion 
National Weather Service Lincoln Illinois
251 PM CDT Thursday Jul 28 2016

Short term...(this evening through friday)
issued at 245 PM CDT Thu Jul 28 2016

A cool front moving southeast toward I-55 at mid afternoon will push
into thru eastern Illinois late today and stall out in southeast Illinois
tonight. Had a few reports of funnel clouds over central Illinois since
midday east of the Illinois River, with the most recent report near
Metamora. Isolated to scattered thunderstorms where over much of Illinois
in the tropical airmass over Illinois where dewpoints in the low to mid
70s and temps in the 80s. Most heat index readings were in the
upper80s and lower 90s, though Springfield had heat index of 98f.
Laps convective available potential energy ranged from 1500-3000 j/kg with highest readings west of
I-57. Isolated to scattered thunderstorms will gradually diminish
from west to east during tonight as instability weakens and front
pushes into southeast Illinois. Have patchy fog overnight until mid
morning Friday with light winds and moist low levels. Hrrr show more
widespread fog over eastern Illinois with locally dense fog possible. Lows
ovenight range from 65-70f with mildest readings south of I-70.
Highs Friday range from upper 70s NW of Illinois River, to the mid 80s in
southeast Illinois from I-70 south. Another frontal boundary and a
shortwave trof pushing southeast over central Illinois on Friday to
develop chances of thunderstorms and carried 30-40%. Storm Prediction Center day2
outlook has a marginal risk (5%) along and south of a Canton to
Bloomington line on Friday where instability will be higher.

&&

Long term...(friday night through thursday)
issued at 245 PM CDT Thu Jul 28 2016

Weak shortwave trof that will affect the area on Friday should start
to shift east of the forecast area Friday night. Still have pops
going Friday night but it appears that most of any convection that
develops during the day Friday will be diurnal in nature and be out
of the area during the evening. After that, the frontal boundary
should push far enough to the south on Saturday to limit the rain
chances to far southern Illinois as weak high pressure settles in
from the northwest. Latest European model (ecmwf) looking drier with this fair
weather system for Saturday and Sunday with the return flow setting
up Sunday night along with pops over southwest Illinois.

Upper level ridging is forecast to build over the region early next
week as a deep trof shifts eastward over the northern rockies. This
should start the heat back up over the area with medium range models
showing varying solutions to how strongly the ridge builds north.
Unfortunately, as has been the case most of this Summer, the ridge
is rather flat and convection has no problem riding the northern
periphery of the ridge and then southeast into the Midwest at least
through the middle portion of the week. This will result in daily
chances for thunderstorms starting Sunday night just ahead of the
warm front, and for the remainder of the period as the model
consensus is rather conservative with any amplification of the
central U.S. Ridge early next week. After our "cool-down" this
weekend, model guidance has most of the area back to or just above
90 Wednesday and Thursday of next week.

&&

Aviation...(for the 18z tafs through 18z Friday afternoon)
issued at 1240 PM CDT Thu Jul 28 2016

Scattered thunderstorms have been quickly developing over central
Illinois at midday in warm and moist tropical airmass as temps have
risen into the low to mid 80s and dewpoints in the low to mid 70s.
Convective available potential energy at midday were 1600-2600 j/kg over central Illinois and highest
west of I-57. A frontal boundary just east of the Illinois River will
push southeast into eastern Illinois during the afternoon and continue
to develop scattered thunderstorms along and ahead of it. A
thunderstorms already affecting spi while another ts was just
southeast of pia and moving southeast. Thunderstorms will track to
near Dec in next hour and possibley to bmi and cmi in about an
hour or 2. Have vsts at all taf sites this afternoon with tempo
groups of MVFR conditions with thunderstorms this afternoon
especially southeast of Illinois River. Have added fog with MVFR vsbys
to taf sites overnight until mid morning Friday with vsbys
possibly getting down to 1-2 miles from 09-13z especially at cmi.
Winds to stay fairly light next 24 hours, trending NW direction
behind the front and staying less than 10 kts, and light winds
tonight.



&&

Ilx watches/warnings/advisories...
none.
&&

$$

Short term...07
long term...Smith
aviation...07

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