Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 201555
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1055 AM CDT Fri Oct 20 2017

.UPDATE...
Issued at 1055 AM CDT Fri Oct 20 2017

Another beautiful fall day expected across central and southeast
IL with sunshine filter through some thin cirrus clouds and
southerly winds 7-14 mph and few gusts 15 to 20 mph by afternoon.
Mild highs in the upper 70s to near 80 degrees.

Late morning surface map shows 1029 mb high pressure over WV and
ridging from the eastern Great Lakes into AL/GA. A deepening 989
mb low pressure was over western MT. Increasing pressure gradient
over central IL today was giving stronger southerly winds. This
will combine with ample sunshine to warm temperatures currently in
low to mid 60s to upper 70s to near 80F for highs this afternoon.
A 591 dm 500 mb high pressure was over the northeast Gulf of
Mexico and ridging northward across the TN/OH river valleys and
into lower MI. Surface and upper level high pressure ridge will
stay in place rest of the day keeping IL warm and dry rest of
today.

&&

.SHORT TERM...(Today and tonight)
ISSUED AT 320 AM CDT Fri Oct 20 2017
Regardless of oscillation in the models, the forecast remains very
much the same from a consensus point of view. Unseasonably warm
temperatures today and tomorrow...wet weekend from Saturday night
and into next week. Cooler temperatures on the other side of the
weekends rain.

Wave digging in over the Pacific coast this morning on sat imagery
has begun to modify the upper air pattern into a more amplified
signal...with southwesterly flow becoming more prominent and
resulting in the warmest day in the forecast for today. Max temps
expected to climb into the mid to upper 70s. Tonights lows
relatively mild in the 50s.

.LONG TERM...(Saturday through Thursday)
ISSUED AT 320 AM CDT Fri Oct 20 2017

For Saturday, the warm airmass is still in place over the region
as the upper trof moves across the Rockies and into the Plains.
The max temps will be slightly tempered, however, with an increase
in the cloud cover in advance of the approaching front. Models had
originally kept the wave phased and a long line of showers
progressed with the sfc front. The past few runs split the energy
into a cut off low to the south, and a more progressive flow
pattern just to the north. If anything, current runs are a hybrid,
trending back to a more phased pattern. Low is not as strong as it
cuts off to the south. However, small shifts in that particular
feature will result in fairly significant changes for the forecast
in Central IL. With the low to the south keeping the better
dynamics, ILX may end up on the edge of the northern stream, and
just north of the developing low over the Gulf Coast. More shower
activity in the gap between materializing in the GFS again this
run...with an appropriate drop in QPF guidance. Forecast remains
mainly unchanged with the best chances for rain Saturday night and
Sunday. Pops linger into the work week with cooling temperatures
as the progression of the weakening boundary is slowed. Cooler
temps come to an end on Thursday as winds come around to more
southerly and start at least a brief warming trend again.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 619 AM CDT Fri Oct 20 2017

High pressure centered to the east of Illinois will provide VFR
conditions for the 12z TAF period. Winds will be the main concern
to aviation, as south winds increase to 10-15kt, especially in
western Illinois closer to the tighter pressure gradient. Cloud
cover will be limited to mainly cirrus clouds, as southwest flow
aloft pushes some upper level moisture into the area.

No reduction to visibility is expected at the terminal sites
through tonight.


&&

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

$$

UPDATE...07
SHORT TERM...HJS
LONG TERM...HJS
AVIATION...Shimon



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