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Area forecast discussion
National Weather Service Lincoln Illinois
412 am CDT sun Sep 22 2019

Synopsis...
issued at 355 am CDT sun Sep 22 2019

Bands of showers and some thunderstorms will continue to spread
across central Illinois during today, with a Flash Flood Watch over the
Illinois River valley into this evening. A cold front will push through
the area during tonight, with showers and thunderstorms diminishing
later this evening and overnight as cooler and less humid air
arrives on Monday.

&&

Short term...(today and tonight)
issued at 355 am CDT sun Sep 22 2019

Continued the Flash Flood Watch for the Illinois River valley through 1
am CDT tonight. Widespread showers and some embedded thunderstorms
to bring an additional 1.5-2 inches of rain today into mid evening
with locally around 3 inch amounts possible. Already a widespread
1-3 inch rain has fallen since Friday morning along and NW of the
Illinois River with locally 4-6 inch amounts.

Scattered rain showers continue to skirt northern/NW County Warning Area early
this morning and they lift NE. Areas from I-55 southeast have seen
little if any rainfall during the night. More widespread showers
and some thunderstorms were moving NE into parts of Schuyler,
Fulton and Knox counties with widespread convection over central
and eastern Iowa into NW MO. This moisture is in part due to
remnants of Imelda and supported by very high precipitable water
values of 1.6 to 2 inches, highest over northern/NW County Warning Area. Surface
map early this morning shows a cold front over NW parts of WI/Iowa
into central KS, to 1006 mb low pressure along the southern Colorado/Kansas
border.

Latest cams have low pressure ejecting NE along the front into NW
Illinois by late afternoon while pushing a widespread band of showers
and some thunderstorms eastward across the Illinois River valley during
this morning and into eastern/se Illinois during this afternoon and
early evening. Areas se of I-70 will likely stay dry much of today
and also have warmer highs in the mid to upper 80s. Widespread
clouds and showers to keep cooler highs in the mid to upper 70s NW
of I-55. Breezy SW winds will develop today with gusts of 20 to 30
mph expected. In addition to heavy rain threat over the Illinois River
valley today, Storm Prediction Center day1 outlook has marginal risk of severe
thunderstorms over much of County Warning Area from I-70 NW and se of Galesburg
this afternoon and early evening with 5% risk of hail and damaging
winds.

A cold front is projected to track se toward the Illinois River by
03z/10 PM this evening and into southeast Illinois by 09z/4 am
overnight. Showers and thunderstorms move into southeast Illinois this
evening, and then diminish from NW to se behind the cold front
late this evening and overnight. The cold front will pass se of
County Warning Area by dawn Monday with dry and less humid air ushering into the
area. Lows overnight to range from the mid 50s NW of the Illinois River,
to the mid 60s far se Illinois by Lawrenceville.

&&

Long term...(monday through saturday)
issued at 355 am CDT sun Sep 22 2019

Weak high pressure settles into MO/Illinois by Monday afternoon and
brings return of more sunshine and less humid air with dewpoints
in the 50s. Highs Monday in the mid to upper 70s which is closer
to normal for late September. Lows Mon night mostly in the mid
50s. High pressure settles over the mid MS valley and into Kentucky/Tennessee
on Tue and brings another nice day to central/se Illinois. Skies become
partly sunny by Tue afternoon with highs in the upper 70s in
central Illinois and near 80f in southeast Illinois. Dewpoints in the upper
50s to around 60 on Tuesday so fairly comfortable humidity levels
yet.

Next wx system to move into the area overnight Tue night with
surface low passing north of Lake Superior and a frontal boundary
moving into NW Illinois late Tue night. Have chances of showers and
thunderstorms over central and especially western County Warning Area. Storm Prediction Center day3
has marginal risk of severe storms overnight Tue night NW of I-55
while slight risk is over large part of Iowa and western WI. Cold
front to push se thru County Warning Area on Wed and bring chances of showers and
thunderstorms, then diminish from NW to se during Wed night.
Cooler and less humid air returns again by Thu with weak high
pressure settling over the area by Thu morning.

Another wx system moves into the upper Midwest late Thu night and
Friday with best chances of convection to our NW while keeping
20-30% pops over central Illinois and drier in southeast Illinois late this
week. Temperatures and humidity levels expected to increase Friday
into the weekend with highs back into the 80s and dewpoints rising
into the upper 60s/lower 70s. CPC 8-14 day outlook for Sep 29-Oct
5 has greater than 80% chance of above normal temperatures over Illinois
so summerlike weather may hang around another week as a
subtropical ridge builds across the Southern Plains and southeast
states and into the mid MS River Valley by early next week.

&&

Aviation...(for the 06z tafs through 06z Sunday night)
issued at 1153 PM CDT Sat Sep 21 2019

Scattered showers are expanding in coverage late this evening,
with some northeast movement to the main area. It appears that our
area will see a few hours of these showers, then a short break
before additional development occurs with the next shortwave.
Prevailing rain will begin in our northwest counties by Sunday afternoon,
as the cold front reaches near Illinois. Despite the slow arrival on Sunday,
the front is expected to become more progressive as it pushes
east across the remainder of the central Illinois Sunday afternoon
and Sunday night. By 12z Monday, the front will have exiting our
forecast area to the southeast.

MVFR ceilings are likely to develop with the onset of rain on
Sunday, with IFR clouds not out of the question. Vis should
generally remain VFR, with brief periods of MVFR during heavier
rain showers or storms. MVFR conditions look to close out the 06z
taf period, after MVFR conditions develop Sunday afternoon into
early evening.

Winds should remain southerly until at least Sunday morning, with
a shift toward the SW during the day on Sunday. Winds should
become gusty again on Sunday, with 20-25 kts possible at times
before the cold frontal passage.

&&

Ilx watches/warnings/advisories...
Flash Flood Watch through late tonight for ilz027>031-036-037-
040-041-047>050.

&&

$$

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