Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 170454

Area Forecast Discussion
National Weather Service Lincoln IL
1054 PM CST Mon Jan 16 2017

Issued at 840 PM CST Mon Jan 16 2017

Surface low pressure approaching Quincy early this evening will
continue to track northeast across the northern half of our
forecast area during the remainder of the evening hours. A band
of showers was located right with the surface low and those will
track over the area through the late night hours. Winds will drop
off as the low moves across the area with the areas of dense fog
holding into the early morning hours accompanied by mainly light
rain or drizzle. Temperatures will continue to slowly rise this
evening until the low shifts off to our northeast during the early
morning hours. Winds will turn into the southwest just ahead of
the low and then turn more westerly as it moves away. Despite a
cold frontal passage early Tue morning, short term models suggest
another band of dense fog will follow the cold front in during the
early morning hours through at least late morning. We may have to
extend and even expand the current dense fog advsy thru at least
the mid morning hours on Tuesday. Have made some changes to the
weather grids in adding the fog threat thru Tue. morning and
adjusted some POPs as well late tonight into Tue. We should have
the updated zones out by 915 pm.


.SHORT TERM...(This evening through Tuesday)
ISSUED AT 243 PM CST Mon Jan 16 2017

Will need to extend the dense fog advisory through the rest of the
afternoon from I-72 north while letting it expire at 3 pm south of I-
72. Easterly winds are shifting southeast and advecting the dense
fog into area nw of the IL river. Peoria and Lacon have returned to
dense fog and Galesburgs vsbys is slowly dropping. Visibilites from
Jacksonville, Springfield, Decatur and Paris south have improved to
1-4 miles in past hour. Widespread dense fog caused in part by
mild/moist air moving over a cold ground (6 am frost depth at
Lincoln was 4 inches and 10 inches at Altona). The latest runs of
the HRRR and RAP models showing areas of fog and locally dense fog
lingering over northern CWA into this evening and lasting longest
over the IL river valley. Visibilities should improve during
overnight as a cold front moves east across IL.

20Z/2 pm surface map shows 1010 mb low pressure over east central KS
with a warm front lifting northward into central parts of MO and KY
and southern IL south approaching I-64. Bands of rain showers were
over IL with a few thunderstorms over eastern MO and lifting ne
toward the MS river. Temps currently range from mid 30s from Macomb
to Lacon northward to the lower 50s south of I-70.

Models deepen surface low pressure from east central KS northeast to
southern Lake MI by 12Z/6 am Tue with pressure down to 1007 mb. A
warm front will lift northward over central IL (especially se of the
IL river) during this evening, followed by the cold front sweeping
eastward across IL during overnight. Have likely to categorical
chances of showers along with isolated thunderstorms this evening,
then gradually diminish pops behind the cold front overnight with
highest pops in eastern IL where isolated thunderstorms still
possible til 3 or 4 am when cold front reaches near the IL/IN
border. Isolated light rain showers could linger over eastern IL and
areas from I-74 ne on Tue morning. Rainfall amounts through tonight
to range from 0.40-0.75 inches. Lows early Tue morning range from
upper 30s nw of the IL river to the lower 50s near the Wabash river
and these will also be the highs early Tue morning. Temps nearly
steady or slowly slipping during the day with WSW breezes.

.LONG TERM...(Tuesday night through Monday)
ISSUED AT 243 PM CST Mon Jan 16 2017

Models are in very good agreement that the modified southwest flow
will continue across the region through the week. Surface high
pressure will build into the area from the west as this past
weekends weather system finally moves off to the east. This high
pressure will keep mild conditions over the area with dry weather.
This will be a brief period of dry weather as another weather system
develops in the southern plains and lifts northeast, in the
southwest flow, through the Miss valley and eventually into the Ohio
valley. Models differ on the intensity of this system, but all agree
that the main low pressure area associated with the system will
remain southeast of the area through the period. The chance of
precip will run from Thursday in the southeast through Friday
morning. The best chance of pops will be in the southeast on
Thursday night. Despite being northwest of the track of the low,
temps overall will remain mild so all precip will be liquid and not
expecting any snow or freezing precip.

Another brief dry period is expected Friday night through Saturday
as the CWA will be in the warm sector ahead of the next weather
system expected for the latter part of the weekend. Models have some
differences with how and where this system first evolves, but agree
that the main low pressure area will come out of the southern plains
and lift northeast somewhere across the mid Miss valley. Location of
this track is where the models struggle with any agreement, but do
agree on the intensity of the system. Precip will move into the area
Sat night and then spread across the CWA for Sun and Sun night.
Temps will remain mild with this system and early look suggests it
will be quite windy as well.

Overall temps will remain warm/mild through the forecast period
with the warmest temps being Sat and Sat night.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1045 PM CST Mon Jan 16 2017

Warm front continues to edge slowly north late this evening and
its along and south of the boundary where we see a marked
improvement in cigs (MVFR) and vsbys (VFR). However, short term
models continue to suggest any improvment in cigs and vsbys
overnight north of I-72 may be short lived, especially along and
north of I-74 where we will see another band of VLIFR vsbys in fog
track over the area tomorrow morning. Finally, as drier air slowly
works its way east across the area late Tuesday morning into the
afternoon hours, we should see an improvement in vsbys across the
board. However, the forecast soundings continue to indicate LIFR
cigs into the afternoon with little hope for any improvement at
least through Tuesday evening. Surface winds will gradually become
south to southwest as the low passes to our northwest later tonight
and then into a westerly direction in the 08z-12z time frame, which
should continue thru the day on Tuesday with speeds in the 10 to
15 kt range.


Dense Fog Advisory until midnight CST tonight for ILZ027>031-



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