Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 160535
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1135 PM CST Mon Dec 15 2014

.UPDATE...
ISSUED AT 850 PM CST MON DEC 15 2014

Low pressure center with current storm system is over southeast
Iowa, with a cold front curving south along the Mississippi River
Valley. The majority of the remaining showers are just ahead of
the cold front and are currently pushing into east-central and
southeast Illinois. Some wrap around showers also appear to be a
lingering threat for the rest of the night as well, but the
coverage/intensity should be minimal.

Going forecast is in reasonable shape. Only plan to make tweaks for
the latest trends, most notably to PoPs.

&&

.SHORT TERM...(Tonight)
ISSUED AT 240 PM CST MON DEC 15 2014

Stacked low along the IA/MO border this afternoon will continue to
track ENE through tonight. Trailing cold front currently over
central Missouri will move into IL by late afternoon and then push
across Central and SE IL this evening. Widely Scattered showers can
be expected well ahead of the front as warm moist Gulf air surges
northward into the region. A convective line is expected to develop
along the surface front this afternoon and accompany the front
across IL this evening.  Attm instability remains quite limited and
do not expect any thunder.  Clouds will persist in the wake of the
front given the proximity of the upper low. Showers will also likely
linger near the cold core system, mainly northwest of I-72/Danville.

&&

.LONG TERM...(Tuesday through Monday)
ISSUED AT 240 PM CST MON DEC 15 2014

Pattern across the lower 48 expected to remain active, especially
with the southern stream systems this period, with colder temperatures
pushing in on Tuesday and remaining with us thru next weekend and
possibly through the last week of December.

The surface low over extreme southern Iowa this afternoon will
track northeast and be located over southern Lake Michigan by 12z
Tuesday. Looks as if we will remain on the mild side into early
Tuesday with periodic showers before winds turn into the west and
northwest in the wake of the storm and brings in colder weather
for Tuesday afternoon and beyond. Forecast soundings showing the
potential for some rather gusty winds tomorrow as the colder air
is drawn southeast into our area which should hold into Tuesday
evening.

Thought we might be able to break out of this cloudy and gloomy
spell of weather as the storm system pulls away but current visible
satellite data showing widespread cloud cover to the north and west
of the storm system with the latest 12z NAM-WRF soundings indicating
the low level moisture to hold over our area right into Wednesday
with another rather stout subsidence inversion developing, effectively
trapping the low level cloud cover in place. So will hold the clouds
in longer Tuesday night into Wednesday based on the latest model data.
As the surface ridge axis shifts over our area by late Wednesday, we
may start to see some breaks in the clouds, just in time for some
mid and high level clouds to move in ahead of the next shortwave
slated to push south of our area on Thursday. Models continue to
develop some precip ahead of the system Wednesday night well to
our southwest, but as it tracks northeast into a more confluent
flow aloft and some very dry air at the surface, models back down
on any precip this far north with the better threat closer to the
frontal boundary over the lower Mississippi Valley.

A stronger shortwave in the southern stream will push into Texas
by late Thursday night and Friday and spread a large swath of rain
across the lower Mississippi Valley. Most of the models, including
the high res GFS model, continues to indicate a more suppressed
track to the surface system keeping the bulk of the more significant
snow and rain just south of our area Friday into early Saturday. Will
keep the higher chance POPs over southeast Illinois and still keep
some low POPs further north in case the northern stream wave seen
on models later Friday has a tendency to draw the system a bit
further northwest than what is currently indicated. After the system
on Saturday tracks off to the east, rather quiet weather is anticipated
for the remainder of this forecast period before a strong northern
stream wave begins to dive southeast into the northern Plains late
Monday and possibly phase with another southern stream shortwave on
Tuesday, which would bring a storm system into parts of the Midwest
just after this forecast period, followed by much colder weather for
the Christmas holiday. Medium range models have been hinting at this
pattern change for days now with a large deep trof carving out over
the Great Lakes, while ridging forms over western Canada and our flow
aloft becomes northwesterly drawing down some rather chilly air for
the last week of December.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
ISSUED AT 1129 PM CST MON DEC 15 2014

The threat of steadier rains has come to an end across the central
Illinois terminals, although drizzle and spotty showers will
linger through the night. Still expect IFR conditions to prevail
through the night, but a few periods of MVFR conditions are
possible (especially at KSPI/KDEC). Gusty northwest winds on the
back side of the storm system will develop Tuesday morning, slowly
bringing drier air into the area. All terminals should trend into
the MVFR category during the day, but it looks like these cigs
will linger until at least Wednesday.

&&

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

$$

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





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