Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 211945
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
245 PM CDT Sun Sep 21 2014

.SHORT TERM...(Tonight)
ISSUED AT 244 PM CDT SUN SEP 21 2014

Strong 555 dm 500 mb low over Lake Huron will pull eastward across the
eastern Great Lakes region tonight. Meanwhile at the surface, 998 mb
low pressure over southeast Ontario to lift ne into the Saint
Lawrence Seaway by Monday morning, while 1027 mb high pressure over
the western Dakotas and western Nebraska to settle into the Midwest.
Broken to overcast cumulus/stratocumulus clouds from I-74 northeast
and  cattered clouds to the sw to gradually diminish during the
evening after sunset and linger longest from BMI and CMI northeast.
Breezy northwest winds 10-20 mph and gusts of 20 to 35 mph during
mid/late afternoon to diminish to less than 10 mph around sunset and
turn more northerly during the night. Despite clearing skies and
winds diminishing, do not think fog will be an issue tonight due to
drier air advecting into central/se IL. Lows tonight in the mid 40s
central IL and upper 40s in southeast IL.


&&

.LONG TERM...(Monday through Sunday)
ISSUED AT 244 PM CDT SUN SEP 21 2014

An extended period of dry weather, with gradually warming
temperatures can be expected in central and southeast Illinois for
the next 7 days.

The medium and long range models indicate that a complex upper level
pattern will evolve the next several days. The week will begin with
a northwest upper level flow and a surface ridge of high pressure in
control through Tuesday. This will give us cooler than normal
temperatures and plenty of sunshine. By midweek, the departing upper
level trough in the northern stream will allow ridging aloft to
build across the Midwest. This will produce a warming trend with a
dry east-southeast low level flow and rain-free weather through the
end of the week.

Model differences become apparent very late in the forecast period
for next weekend. The GFS model pushes the upper level ridge axis
much farther east than the European and Canadian models by Saturday.
This allows a return flow to develop, with tropical moisture surging
northward, resulting in the potential for rain late Saturday-Sunday.
For the upper ridge to move toward the Appalachians by Saturday, an
upper low in the southwestern U.S. would need to kick out much
quicker. It seems that the GFS is too fast moving this feature out
considering the overall expected flow pattern in the Pacific and
Rockies. Thus, will keep the forecast dry through next weekend.


&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
ISSUED AT 1255 PM CDT SUN SEP 21 2014

VFR conditions should continue across the central IL airports
through 18Z/1 pm Monday. Strong 555 dm 500 mb low near Saginaw Bay
in east central lower MI is producing broken cu/stratocu clouds
of 3.5-5k ft along and nne of I-74. These clouds to continue to
expand southward into central IL next few hours and reach into DEC
after 19Z and possibly SPI by 20Z which will be on sw edge of this
cloud deck later this afternoon. Models have trended slower with
clearing the cu/stratocu clouds and could linger until 02Z-04Z
along I-74 especially at BMI and CMI. Fair skies expected across
area overnight into Monday. Breezy nw winds of 12-17 kts with
gusts of 20-27 kts this afteroon due to tight pressure gradient
between 999 mb surface low pressure in southeast Ontario north of
Lake Ontario and 1028 mb high pressure over western Dakotas and
western NE. Winds to diminish to 4-8 kts by sunset and veer more
northerly and continue Monday morning. No fog expected overnight
with drier air advecting in on NNW winds.


&&

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

$$

SHORT TERM...07
LONG TERM...MILLER
AVIATION...07





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