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000
FXUS63 KILX 011649
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1049 AM CST Sun Mar 1 2015

.UPDATE...
ISSUED AT 1042 AM CST SUN MAR 1 2015
Upper air disturbance moving through the region producing plenty
of snowfall. Some light to moderate snow expected to continue
across areas north of I-72 through midday. Another round of
enhanced radar returns moving just south of Springfield and will
be moving into Taylorville and eastward to Paris through the early
afternoon, producing another inch or two of accumulation. Western
edge of the system seems to be moving through the Illinois River
Valley now and should help to move the majority of the precip out
of the region by mid afternoon...with some fzdz threat remaining
as the system winds down.

&&

.SHORT TERM...(Today)
ISSUED AT 313 AM CST SUN MAR 1 2015

Snow continues to fall over all but far northwest sections of the
forecast area early this morning. However, latest radar trends
indicates a bit of push to the north with the snow with precip
starting back up into Macomb this past hour. Short term models
indicate another band of snow to shift further north into the
advisory area by mid-morning. Was on the fence with the area from
Peoria and northwest whether to cancel the advisory early this
morning but with models suggesting this second wave moving into the
area, will hold off canceling the northwest section of the advisory
for now. If trends suggest the snow will shift further south of the
Peoria area, similar to this first wave, will go ahead and cancel
along the Illinois River valley later this morning.

Further south, where we thought we would see a few 6 inch amounts,
we have had reports of 5-6 inches already roughly from along the I70
corridor north towards Taylorville to just south of Paris. For
consistency sake with our neighboring forecast offices, went ahead
and upgraded to a winter storm warning for a storm total of 5 to 7
inches with locally higher amounts from just east of Springfield to
the Indiana state border. Not your classic winter storm, as the snow
has been falling with very light winds, and we really don`t see the
winds coming up much today at all, so its basically an upgrade due
to more widespread 6 inch snow amounts.

Forecast soundings along and south of I-70 suggest a mix with sleet
and freezing rain for a time this morning before we see surface temps
warm into the low to mid 30s, melting any ice accumulation that may
occur in that area this morning.

&&

.LONG TERM...(Tonight through Saturday)
ISSUED AT 313 AM CST SUN MAR 1 2015

Forecast focus quickly shifts to the next late-winter storm system.
The key will be with significant WAA in the mid levels, with 850 mb
temperatures quickly rising into the +4 to +6C range between
midnight and sunrise Tuesday. Any snow/sleet mixture will quickly
transition to liquid precip, with forecast soundings showing the
above-freezing layer as much as 7000-8000 feet thick. Currently
thinking that up to a tenth inch of freezing rain is likely through
early Tuesday morning before the precip transitions to regular rain
everywhere. The big question is how fast the surface temps respond
with a significant snow pack. Hourly temperature projections showing
areas west of Springfield climbing above freezing shortly before
sunrise, with the ECMWF MOS as high as 37-38F by 6 am, the GFS MOS
in the mid 30s and the NAM MOS just shy of freezing. Trended the
hourly grids in more of a GFS/NAM blend initially, with the overall
highs Tuesday close to the GFS MOS.

In terms of precip timing, a lot of dry air below 700 mb will need
to be overcome first, which will take much of the evening. Have thus
kept most of the CWA dry during the evening, with slight chance
PoP`s in the far southwest. The NAM is the quickest in pulling out
the precipitation Tuesday afternoon ahead of the main cold front,
but went a little slower on the timing and lingered some likely
PoP`s in the far southeast into early evening. However, any
lingering precip will quickly exit as strong CAA takes place with an
incoming high. The trailing end of the cold front will briefly get
hung up in the parallel upper flow south of the Ohio Valley Tuesday
night, and have lingered some low chance PoP`s into early Wednesday
mainly south of I-70.

Another slug of cold air will swing across the northern tier of
states midweek, with 850 mb temperatures as low as -15 to -18C over
our area Wednesday night. Another period of temperatures 20-25
degrees below normal will result. However, the split upper flow will
finally start to merge together over the Midwest late week, helping
to bottle up the colder air north of the Canadian border. This will
allow temperatures to get much closer to normal for the end of the
week.

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
ISSUED AT 520 AM CST SUN MAR 1 2015

MVFR with occasional LIFR cigs/vsbys in snow the main forecast
concern into early this afternoon. Band of snow has been persistent
from SPI east northeast thru DEC and CMI and now was edging closer
to BMI. PIA for the most part has stayed in the VFR category but
looking at the past few runs of the short term models suggest a
period of at least MVFR cigs/vsbys as another band of snow shifts
northeast into that area this morning. Most of the snow should shift
off to the east of the TAF sites by 21z with MVFR cigs continuing
thru this evening when colder and drier air will push southeast into
the area with most areas seeing VFR conditions after 03z. Winds will
not be much of a factor today with a variable direction at most sites
until later this afternoon with speeds of 2 to 7 kts. Winds are then
forecast to shift into the west and northwest after 19z and and
increase to around 10 kts by late afternoon or early evening.


&&

.ILX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY until 6 PM CST this evening FOR ILZ029-
031-036>038-040>051-053-071>073.

WINTER STORM WARNING until 6 PM CST this evening FOR ILZ052-
054>057-061>063-066>068.

&&

$$

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