Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 220546
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1146 PM CST Sat Jan 21 2017

.UPDATE...
Issued at 849 PM CST Sat Jan 21 2017

Clouds returning across central and southeast Illinois this
evening, after a rare (at least lately) sunny day. A disturbance
lifting northeast from the southern Plains will continue to
approach the area overnight, with an associated increase in rain
chances across much of the forecast area by morning. The current
radar returns in our vicinity are all virga, with the nearest
reports of rainfall reaching the ground across southwest
Missouri. Temperatures fell quickly this evening in most areas due
to the light winds and minimal cloud cover. Temperature/dew point
spreads are small at most locations, and fog has started to
develop. The fog is currently most significant northwest of the
Illinois River. Expect the increasing clouds to keep the fog from
getting out of hand, although some high resolution models suggest
dense fog developing by morning along and west of I-55. Going
forecast is reasonable for the most part, but plan to make some
adjustments to PoPs and fog, as well as some hourly tweaks to the
other parameters.

&&

.SHORT TERM...(This evening through Sunday)
ISSUED AT 244 PM CST Sat Jan 21 2017

Beautiful spring-like day here in January. Sunshine has become
abundant now that earlier high clouds have exited the southeast CWA,
and temperatures most areas east of the Illinois River are in the
60s, with a few upper 60s near Flora and Lawrenceville. High clouds
are quickly approaching from the southwest this afternoon, and these
will result in mostly cloudy conditions returning by early evening.

Latest water vapor imagery showing a nice spin over northern New
Mexico, as a shortwave moves into the area. Morning model guidance
in good agreement with this feature forming a closed upper low which
will track to the Arkansas/Mississippi border by midday Sunday.
A weak surface boundary will also be traversing the forecast area
this evening. High-resolution model guidance has been giving some
sporadic shower activity with this particular feature, but forecast
soundings showing a fair amount of drier air that will need to be
overcome below 10,000 feet. Thus, will limit PoP`s to about 20% in
areas along and south of I-72 until some additional low-level
moisture begins moving in from the southwest later in the night.
Rain chances across the south half of the CWA significantly increase
Sunday morning as the low lifts northeast. Have increased rain
chances Sunday to categorical range (80%+) south of I-70, but
northerly winds will continue with the drier fetch of air across the
north, and rain chances should be fairly minimal in areas as far
north as Peoria.

While temperatures Sunday will not be as balmy as today, 50s will
still be likely east of the Illinois River, perhaps closer to 60
across the southeast CWA.

.LONG TERM...(Sunday night through Saturday)
ISSUED AT 244 PM CST Sat Jan 21 2017

Large storm system tracking well south of the Ohio River Sunday
night will produce the better rain chances across the east during
the evening with a gradual decrease in POPs from west to east after
midnight. The upper and surface lows will track into the eastern U.S.
on Monday while ridging develops over the Midwest ahead of our next
storm system for late Tuesday into early Wednesday. We should be
cooler on Sunday as a northeasterly flow develops coupled with more
clouds and scattered areas of rain, especially over the east.
However, temperatures tomorrow will still average some 10 to 20
degrees above normal for this time of year with afternoon highs
ranging from the mid 40s northwest to around 60 far southeast.
Most areas should be back down into the 40s by Monday before another
push of warm air is expected on Tuesday afternoon ahead of the
approaching storm. Right now we are forecasting highs from the mid
40s to lower 50s, but with an increasing southerly wind Tuesday
afternoon, we may be raising those highs a category or two in
future forecasts.

The rather deep surface low will track to the north of our area by
Wednesday morning with the more significant rain chances along and
north of the I-74 corridor Tuesday night. Colder weather will follow
in the wake of the storm on Wednesday, but as it looks now, we will
only be returning to more seasonal temperatures by the end of the
week. With the broad cyclonic flow late Wednesday into Thursday, we
may see some flurries or sprinkles from time to time, with the
soundings becoming more favorable for flurries as we head to
Thursday. Looks as if we see any light precip, it would be confined
to the east during this time frame. As the ECMWF advertised
yesterday, the upper trof over the Great Lakes will be more
progressive and not nearly as deep as what was forecast a few days
ago. The past couple of runs of the GFS have trended more towards
the deeper portion of the trof much further to the northeast than
previous runs, resulting in a more of modified Canadian, not
an Arctic air mass progressing over the region as we head towards
the last few days of January. This should bring near to slightly
above normal temperatures to the Midwest with not much in the way
of significant storm systems across the area.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 1140 PM CST Sat Jan 21 2017

Clouds will thicken and lower across the central Illinois
terminals through the day Sunday, associated with the approach of
a weather system from the Plains. Patches of dense fog exist
across north-central Illinois, but the increasing clouds should
mitigate its expansion. Showers will accompany the system, but
coverage over the local terminals should be too low to go above a
VCSH mention at this time. Expect widespread MVFR condtions by
later in the day Sunday.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Bak
SHORT TERM...Geelhart
LONG TERM...Smith
AVIATION...Bak


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