Area Forecast Discussion
Issued by NWS Central Illinois
FXUS63 KILX 100446
Area Forecast Discussion
National Weather Service Lincoln IL
1146 PM CDT Sun Mar 9 2014
ISSUED 850 PM CDT Sun Mar 9 2014
South to southwest winds will increase across central and
southeast Illinois for the rest of the night, possibly becoming a
little gusty at times. These stronger winds are the result of a
strengthening pressure gradient to the south of an approaching
frontal boundary. These stronger winds will help keep temperatures
from falling much for the rest of the night with most locations
seeing nearly steady temperatures.
Going forecast has this scenario well covered. Have made minor
tweaks to hourly conditions, most notably to bump up the winds a
little. However, these changes do not warrant an update to the
zone forecast at this time.
ISSUED 1146 PM CDT Sun Mar 9 2014
Predominantly VFR conditions expected across the central Illinois
terminals through the 06Z TAF valid time, with mainly AC and CI
cigs. However, some patchy MVFR HZ/BR has developed in the past
few hours. With winds staying up overnight, do not think the
haze/fog should become too problematic. Southwest winds will
prevail through most of the period ahead of an approaching front.
Strong westerly winds aloft will produce LLWS for much of tonight
into Monday morning despite surface winds staying above 10 kts.
Surface winds will actually decrease a little on Monday as the
pressure gradient weakens ahead of the frontal boundary. The front
is not expected to produce any precipitation locally.
ISSUED 205 PM CDT Sun Mar 9 2014
SHORT TERM...Tonight through Wednesday
Unseasonably warm weather to settle in for the next couple of days
then winter returns late Tuesday night into Wednesday morning with
the threat for several inches of accumulating snow.
A rather quiet weather scene is anticipated over our area thru most
of Tuesday as the upper flow deamplifies temporarily across the
central portion of the country. Models showing good agreement with
the upper and surface patterns into Tuesday evening with the large
surface high pressure system that brought the frosty, and in some
locations, foggy conditions this morning slowly shifting to our
south. A weak shortwave will race across the northern Great Lakes
on Monday which will help to increase the southwesterly flow over
our area resulting in some spring-like temperatures Monday afternoon.
Forecast soundings continue to show quite a bit of cirrus clouds
across the area during the day which may keep temperatures from
really taking off later in the morning, but for now, will stay the
course and keep afternoon readings in the upper 50s far north to
possibly the upper 60s in our southwest counties. Despite the
anticipated high level cloud cover, we should be able to mix down
from about 875-900 mb tomorrow afternoon, which should produce the
expected high temps.
The aforementioned upper wave tracking across the northern Great Lakes
will send a cold front southeast into our area early Tuesday morning,
but with limited moisture and lift, no precip is expected with this
boundary. All models suggest the front will settle to or just south
of the I70 corridor by evening as low pressure develops over parts
of Oklahoma and Arkansas. Latest ECMWF and GFS indicating two distinct
areas of precip, one over the Gulf states associated with southern
stream shortwave which should track east and the second batch of
precip will be with the digging shortwave into the Southern Plains.
Initially, strong frontogenetical forcing to our north will produce
a band of rain and snow late in the day and into the evening with
very impressive 700-500 mb omega noted on the NAM and GFS models
Tuesday night, along with 6.5-7 deg C lapse rates right across our
area. As the strong 500 mb trof axis approaches the area late Tuesday
night into Wednesday morning, we should see a quick changeover to
wet snow across the northern half of our forecast area with 2 to 4
inches of slushy accumulation possible by Wednesday morning. Based
on the magnitude of lift, frontogenetical forcing and steep mid level
lapse rates depicted on models late Tuesday night, we may see some
convective elements embedded in the large precip area which will
complicate the snowfall rates/amounts. For now, 2 to 4 inches looks
reasonable in an axis along and north of a Jacksonville to Champaign
line by Wednesday morning. A tight pressure gradient around quick
moving surface low will produce some strong winds for a brief time
late Tuesday night into Wednesday morning with some gusts around
35 mph not out of the question along the northwest and western
periphery of the departing storm.
The low will have raced to West Virginia by 18z Wednesday with any
lingering snow departing our east counties during the afternoon and
winds gradually diminishing by late afternoon. Not a very springlike
day compared to what we started out with on Monday and Tuesday as
high temperatures struggle to between 35 and 40 degrees from north
to south Wednesday afternoon.
LONG TERM...Thursday through Sunday
The weather settles down for the remainder of the week with more
of a northwesterly flow aloft depicted on both the GFS and ECMWF.
Several shortwaves noted in the northwest flow that track mainly
to our north thru Friday, not offering us much in the way of precip
chances. With these features tracking to our north, some decent
warming takes place over our area Friday as we see afternoon temps
back into the 50s, with 40s and 50s slated for Saturday. After
that, models indicate a gradual deepening of another cold 500 mb
trof just north of the Great Lakes by the end of this forecast
period which may bring us a threat for rain and snow late next
weekend, followed by below normal temperatures as we head through
the middle of March.