Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 221545
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
945 AM CST Thu Jan 22 2015

.UPDATE...
ISSUED AT 944 AM CST THU JAN 22 2015

Not much change needed to the going forecast. Cloud cover to
remain rather extensive today, as forecast soundings show an
inversion around 925 mb holding firm. Visible satellite imagery
showing some thin spots in the cloud cover, but these should be
temporary. Fog across the northeast/east CWA has been improving
and visibility is generally above 2 miles in these areas now. With
little sunshine, temperatures not expected to show a lot of rise.
Have sent some updated grids to refresh the hourly trends, with
new zone forecast to follow in about 15 minutes.

&&

.SHORT TERM...(Today)
ISSUED AT 308 AM CST THU JAN 22 2015

08z/2am IR satellite imagery shows low clouds blanketing nearly the
entire KILX CWA, with the exception of locations along and southwest
of a Taylorville to Lawrenceville line. Temperatures are holding
steady in the lower to middle 30s beneath the cloud deck, but have
dipped into the upper 20s where less cloud cover prevails.  Further
north, an elongated shear axis noted on water vapor imagery
extending from Michigan to Nebraska is sinking slowly southward and
is providing enough synoptic lift to trigger scattered snow flurries
across north-central Illinois.  Radar imagery shows weak echoes
across this area and have seen an occasional report of flurries on
upstream surface obs as well.  Have therefore added scattered flurries
and patchy fog to mainly locations along/north of the I-74 corridor
through the morning hours.  With little or no low-level flow present
today, do not see any mechanism for getting rid of the cloud cover.
Have therefore increased sky cover to go with an overcast forecast
across the board.  Thanks to the clouds and a very light N/NW
wind, temps will be cooler than in previous days.  Will stick fairly
close to numeric guidance, with afternoon highs in the middle to
upper 30s.

&&

.LONG TERM...(Tonight through Wednesday)
ISSUED AT 308 AM CST THU JAN 22 2015

First forecast challenge beyond today will be timing the clearing
trend tonight.  Model soundings disagree on how fast it will occur,
with the NAM being much more pessimistic with cloud cover persisting
through the night.  Meanwhile the GFS suggests skies will gradually
clear from northwest to southeast overnight.  Think NAM may be
suffering from its usual low-level moist bias, so have trended more
toward the GFS with this forecast package.  With surface high
pressure building into the region, have started the evening with
mostly cloudy conditions, but have cleared things out everywhere by
dawn.  Thanks to high pressure, mostly sunny and mild conditions
will prevail on Friday, with high temps rebounding into the 40s.
Another fast-moving clipper system will track into the Great Lakes
Friday night into Saturday.  While any precip associated with this
feature will remain well to the north of central Illinois, winds
will switch to the northwest and clouds will spill back into the
area on Saturday.

Next stronger wave is still on target for late in the weekend,
although 00z Jan 22 models continue a northward trend with its
track.  Just a few days ago, the GFS was showing this system and its
associated surface low tracking across southern Illinois on Sunday,
but it has now shifted the track into southern Wisconsin.  This is
more in line with the ECMWF/UKMET/GEM, which have been showing a
more northerly position for the past several runs.  Latest ECMWF is
a bit further south than it has been, but is still across
north-central Illinois.  End result is growing confidence that very
little precip will occur Sunday/Sunday night as the system tracks by
to the north.  Will continue to feature slight chance PoPs coming
into the far W/NW CWA late Saturday night, with the highest PoPs
focused along/north of I-74 on Sunday.  With surface temps expected
to rise well into the 40s, any rain/snow mix at the onset will
quickly change to rain by midday.  May see precip change back to a
rain/snow mix Sunday night as colder air returns on the back side of
the departing wave, but little or no snow accumulation is
anticipated.  After that, dry weather is expected through the
remainder of the extended with chilly temps in the 30s on Monday
rising back into the 40s by Tuesday and Wednesday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
ISSUED AT 543 AM CST THU JAN 22 2015

Considerable coverage of IFR/LIFR cigs/vsbys across central IL
this morning as a result of a surface boundary across the area and
considerable low level moisture. Area of worst conditions
generally from KDNV-KGBG-KPRG with mainly MVFR surrounding this
area. Isolated FZFG possible as well due to temperatures near to
slightly below freezing. Boundary to sink southward as high
pressure moves over the region, causing light flow and a
temperature inversion aloft to trap low level moisture. Net result
will be diurnal lifting of ceilings and improvement in visibility
with daytime heating, followed by degradation of conditions
evening through overnight.


&&

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

$$

UPDATE...Geelhart
SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...Onton





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