Area Forecast Discussion
Issued by NWS Central Illinois

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

FXUS63 KILX 301956

Area Forecast Discussion
National Weather Service Lincoln IL
256 PM CDT SAT JUL 30 2016

.SHORT TERM...(This evening through Sunday)
ISSUED AT 244 PM CDT Sat Jul 30 2016

Isolated to scattered showers and thunderstors north of I-72 and in
far southeast IL should disspate after sunset as weak instability of
800-1400 J/kg wanes. A short wave trof moving into central IL this
afternoon will exit east of IL this evening allowing convection to
diminish as well. A surface frontal boundary over southeast parts of
IN/IL/MO will track southeast of the Ohio river on Sunday as weak
1020 mb high pressure over the upper Great Lakes region noses
southward toward IL tonight into Sunday. This should provide fair
weather overnight and Sunday with partly sunny skies Sunday. Patchy
fog expected to develop after midnight and lift by mid morning
Sunday, similar to past few morning. HRRR shows the fog
developing/spreading from ne to sw overnight similar to last night
with light northeast flow regime and moist boundary layer with
dewpoints in the mid to upper 60s. Lows overnight mostly in the mid
60s with highs Sunday in the low to mid 80s.


.LONG TERM...(Sunday night through Saturday)
ISSUED AT 244 PM CDT Sat Jul 30 2016

An upper level ridge is forecast to amplify over the central U.S.
starting on Monday as the 500 mb trof that was across the region for
the start of the weekend gradually shifts off to our east. A warm
front is expected to move closer to our area later Sunday night into
Monday bringing increasing chances for showers and thunderstorms,
especially to the western half of the forecast area. Orientation of
the low level jet on the latest ECMWF further west than what we saw
yesterday with one segment over northern Iowa into northern
Wisconsin with a second segment over central Kansas. This would put
the more favorable lift and theta-e advection to our west and north
Sunday night into Monday morning with convection developing out along
the Missouri River valley and tracking east-southeast along the warm
front. The ECMWF not showing much development in this area while the
GFS continues from its previous runs in bringing the rain chances
further east into our area by Monday morning.

Rain chances will increase from west to east on Monday with another
complex of storms possible to our west and north Monday night, which
would track southeast into parts of our area into Tuesday morning.
Low level forcing looks more favorable for our area Monday night
into Tuesday and that is when our POPs are at their highest as the
warm front edges slowly north Tuesday and Wednesday. As the upper
level heights continue to build over the central U.S. midweek, we
should start to see a gradual lowering of rain chances for later
Wednesday through Thursday, although the model consensus suggests
at least a 20-30 percent chance of rain during at least the
afternoon hours Wed/Thu. A stronger shortwave is forecast to track
across the U.S./Canadian border later Thursday which will help to
push a cool front east into the Midwest late Thursday night and
Friday with POPs starting to increase again ahead of that feature.

Warmest temperatures still appear to be from Tue thru Friday with
afternoon readings rising into the upper 80s to lower 90s.
Combining the surface temperatures with another round of high dew
points from the mid to possibly upper 90s, we are looking at heat
index values to increase into the upper 90s to around 103 degrees,
with the higher heat index readings edging into southeast Illinois
Friday afternoon. Something to keep an eye on early in the week,
the latest deterministic models, especially the NAM-WRF, were
indicating the surface dewpoints starting to pool along the slow
moving warm front Tuesday afternoon with areas over west central
Illinois seeing dewpoint temperatures approaching 80 degrees again.
That would push heat index values close to 105 degrees in some of
our western counties Tuesday afternoon, however, this solution 80
to 84 hours out appears to be an outlier at this time, especially
with as much uncertainty with the forecast position of the warm
front over our area in the Tuesday through Wednesday time period.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1258 PM CDT Sat Jul 30 2016

MVFR ceilings of 2-3k ft possible into mid afternoon at times over
central IL airports mainly along I-74. Isolated showers beginning
to develop north of Lincoln and carried VCSH or VCTS at PIA, BMI
and CMI this afternoon until sunset due to weak upper level trof
and short wave moving through IL. Southern extent of convection
will be close to SPI and DEC by mid/late afternoon and may need to
add it there too. Fog and low clouds expected to develop again
after 08Z and lift by 14Z. MVFR visibilities with IFR possible
along I-74. Winds remain light next 24 hours generally less than
10 kts and lightest tonight, varing from NW to NE direction.


.ILX Watches/Warnings/Advisories...


AVIATION...07 is the U.S. government's official web portal to all federal, state and local government web resources and services.