Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Lincoln Illinois
324 am CDT Monday Jul 25 2016
Short term...(today and tonight)
issued at 323 am CDT Mon Jul 25 2016
The weak cold front has slowed down and appears to be nearly
stationary from SW to NE along the Illinois River. The consensus of
short term guidance still project the front to re-gain some forward
momentum today and advance into southeast IL, in response to high
pressure in the plains pushing east.
At present, showers and storms ahead of the front have become
confined to areas east of I-55 at 3 am. Additional showers and
storms have begun to develop farther southwest of our counties, and
are heading toward Scott, Morgan and Sangamon counties. There should
be enough support for that convection to advance into our forecast
area, with 2500-3000 j/kg of MUCAPES still avail.
Severe potential before sunrise should remain low, but flash
flooding will be a concern due to the very heavy rainfall from
earlier last evening, when many areas along and just east of I-55
picked up 2-3" of rain. Those storms are progressing to the NE along
an axis of precipitable water values of 2.2 to 2.3". Any storm
development this afternoon could approach severe levels southeast of
a line from Shelbyville to Mattoon, where Storm Prediction Center has a marginal risk in
the severe outlook. While strong wind and hail may occur in the
stronger storms, flooding will remain a concern with any storm.
Storms will eventually progress southeast out of our forecast area tonight,
as high pressure builds into Illinois from the W-NW.
Temperatures today will warm to near 90 south of I-70, with heat
indices in that area of 100-103 (just below advisory criteria (105).
Will not have any heat headlines today, after the brutally hot day
yesterday. Father north, high temps should only reach the mid 80s,
as dewpoints begin to pull back into the mid 60s.
Long term...(tuesday through sunday)
issued at 323 am CDT Mon Jul 25 2016
For tomorrow, some very low pops confined to south of I-70 with the
front settling down into the Ohio River valley. Remainder of the
area is dry through tomorrow night. Pops return as early as Wed
afternoon in the European model (ecmwf) and the NAM with the front pushing back into
the region from the S/SW as a warm front. GFS is a little slower
with the development of any rain, but precip spreading across the
County Warning Area through Wed night. Both days slightly cooler than the past few
days, but still well into the 80s, with enough relative humidity to result in heat
indices in the 90s.
On a bigger scale, the western ridge will start to build again after
midweek, ultimately amplifying the flow aloft. This sets up more
northwesterly regime for the Midwest, and the forecast becomes
dominated by chance pops with a few periods of slights...but rarely
without the risk for any precip. Several waves dive down into
region, with the best chances for precip looking like Thursday
through Friday, with a possible break for Saturday. Temps in the
extended remain in the 80s in the afternoons...and overnight lows in
the mid to upper 60s.
Aviation...(for the 06z tafs through 06z Monday night)
issued at 1122 PM CDT sun Jul 24 2016
Convection slowly building south late this evening and expect that
trend to continue during the overnight hours. One more round of
storms for bmi with the emphasis on our 3 southern taf sites for
occasional thunderstorms and rain with brief MVFR cigs. After 08z, all the storms
should be south of the taf sites. As a cold front approaches the
area, there may be a brief period of MVFR cigs before VFR
conditions return for the daylight hours on Monday. Surface winds
will be light southerly overnight, but much higher in gusts near
any tsra, and then shift into a northerly direction between 08z
across the northwest and around 11z in our southern sites.
Northerly winds are expected on Monday at 5 to 10 kts.