Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 200459
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
1059 PM CST Sun Feb 19 2017

.UPDATE...
Issued at 835 PM CST Sun Feb 19 2017

Latest surface map indicating the weak area of high pressure that
pushed across central Illinois today has shifted off to our east
this evening. This has allowed a southeasterly flow to develop over
the forecast area which should help keep overnight lows from dropping
too far tonight. That coupled with a large area of cirrus tracking
across the Midwest this evening should also keep the temperatures
up most of the night. The main forecast concern will be another night
with fog overspreading the area from the south. Already seeing
visibilities dropping off to a quarter mile in a few locations over
southeast Illinois and expect that trend to continue to shift north
and northwest late this evening into the early morning hours.

Hard to beat how well the RAP and HRRR did with the stratus and
fog last night and both of these models through much of today have
been advertising a large band of low clouds and fog tracking north
and northwest tonight again. Two negative factors for widespread
fog that has us a bit concerned about going too far west and north
with any advisory are the extensive high clouds and then a
southeasterly wind that is expected to hold between 5 and 10 mph
overnight. Forecast soundings continue to show quite a low level
inversion in place through the night with the boundary layer wind
fields more east to southeast bringing the stratus and fog more
northwest into our forecast area, similar to what the high
resolution models have been advertising for quite some time. As a
result, we will be needing a Dense Fog Advisory soon for far
southeast and east central Illinois and then wait to see how far
west and north to take it later tonight.

Have already sent an updated ZFP out to address the widespread
fog starting to develop in the southeast early this evening. Once
we have determined the areal extent of any advsiory, we will have
an additional ZFP update later this evening.

&&

.SHORT TERM...(This evening through Monday)
ISSUED AT 312 PM CST Sun Feb 19 2017

Dry weather will continue tonight as a weak weather system
develops to the west and moves toward the area for tomorrow. Fog
will be an issue again tonight as there has not been any change in
airmass since this morning and the HiRes models continue to
forecast fog across the area. Will have patchy fog in the west
with areas of fog in the west. Fog will also linger into the
morning hours. Fog could become dense again, but hoping enough
mixing has taken place today to keep visibilities from going as
low as they did this morning. So advisory is not being issued at
this time. Models in good agreement on timing of precip with all
models suggesting that all precip will remain west of the I-55
through afternoon. However, some showers could be possible east of
I-55 during the late afternoon as the system moves into the state.
Temps during the day Monday will remain well above normal, with
records again possible.

.LONG TERM...(Monday night through Sunday)
ISSUED AT 312 PM CST Sun Feb 19 2017

Models are in very good agreement with the bulk of the precipitation
coming into the CWA Monday night and then being out of the area by
Tuesday afternoon. System is not very strong and looks like a simple
front/mid level wave coming through, so most of the precipitation
will be showers. However, very warm temps and an increase in
moisture means that some isolated thunderstorms will not be out of
the question. By Tuesday morning, most of the precip will have moved
off to the east with only the eastern part of the CWA left with come
lingering showers. By Tue afternoon, all the precip will be out of
the area and well east of the state.

Dry and warm weather will return for Tue night through Wed night as
the CWA sits in a some-what zonal flow. This flow will keep the area
in a very warm airmass for middle of the week and into the latter
part of the week.

Then another system will be developing in the southwest US and move
out into the plains Thur into Thur night. Models are in agreement
that this will be occurring but differ on timing and location of the
weather and surface features, including a warm front. The Canadian
has the warm front further south than the GFS and ECMWF and with
such warm air we have been having the last week, believe Canadian
too far south and am more inclined to side with the other two
models. This system will also be deepening some as it moves out of
the southern plains. There should be plenty of moisture and with
dynamics increasing, showers and thunderstorms appear likely,
especially in the warm sector and probably along the developing warm
front. Current forecast models indicate the timing of the front
through the CWA could be late enough that the best instability and
dynamics would be in eastern IL Fri afternoon, then pushing east
into Indiana for Friday evening. This is 5-6 days out and lots could
change between now and then. However, believe showers and storms
warranted in the forecast for Thur night and Fri across the CWA. As
the system lifts northeast into the Great Lakes region Fri night,
showers will linger in the east with any wrap around precip being
north of the CWA.

Dry weather then returns for a brief period for Sat and Sat night
and temps will drop to slightly below normal for Sat during the day
and also that night. However, this cool down will be very short
lived as warm temps will quickly return for next Sunday. A weak wave
will lift northeast across northwest IL and some precip is possible
in northwest part of the CWA during the day.

Temps will remain above normal through most of the week, but then
cool briefly for Sat and Sat night.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1052 PM CST Sun Feb 19 2017

Cigs and vsbys will continue to deteriorate over the next several
hours from south to north as fog and stratus track back into the
area. We continue to expect LIFR to occasional VLIFR conditions
during the morning hours of Monday thanks to the fog and low
stratus. Forecast soundings haven`t really changed that much
with a low level inversion strengthening again overnight
into Monday morning with only a gradual improvement in conditions
as we head into the late morning hours. In fact, most soundings
now suggest once we lose the low clouds and fog by late morning,
we should see VFR conditions during the afternoon hours. Then
our attention will turn to a frontal boundary that will approach
our area during the evening with an increasing threat for showers
and a return to MVFR cigs after 03z. Southeast winds will continue
tonight at 6 to 11 kts and then increase to between 12 and 17 kts
on Monday with a few gusts to 23 kts at times, with winds turning
more into a south to southwest direction Monday evening at 12 to
17 kts.

&&

.CLIMATE...
Issued at 312 PM CST Sun Feb 19 2017

Record Highs / Record Warm Lows - Sunday Feb 19th...
Peoria........ 71 / 50
Lincoln....... 71 / 46
Springfield... 70 / 54
Champaign..... 68 / 46
Bloomington... 70 / 47
Decatur....... 66 / 48
Danville...... 70 / 54
Galesburg..... 63 / 52
Charleston.... 72 / 53
Effingham..... 70 / 45

Record Highs / Record Warm Lows - Monday Feb 20th...
Peoria........ 68 / 46
Lincoln....... 70 / 46
Springfield... 74 / 46
Champaign..... 71 / 45
Bloomington... 67 / 45
Decatur....... 70 / 47
Danville...... 70 / 48
Galesburg..... 64 / 41
Charleston.... 73 / 48
Effingham..... 68 / 54

Record Highs / Record Warm Lows - Tuesday Feb 21st...
Peoria........ 69 / 46
Lincoln....... 69 / 45
Springfield... 69 / 48
Champaign..... 67 / 47
Bloomington... 69 / 46
Decatur....... 68 / 48
Danville...... 67 / 50
Galesburg..... 68 / 40
Charleston.... 71 / 52
Effingham..... 73 / 52

Record Highs / Record Warm Lows - Wednesday Feb 22nd...
Peoria........ 71 / 51
Lincoln....... 71 / 52
Springfield... 71 / 53
Champaign..... 69 / 49
Bloomington... 70 / 53
Decatur....... 72 / 51
Danville...... 71 / 54
Galesburg..... 61 / 45
Charleston.... 71 / 52
Effingham..... 74 / 55

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 10 AM CST Monday for ILZ038-042>057-
061>063-066>068-071>073.

&&

$$

UPDATE...Smith
SHORT TERM...HJS
LONG TERM...Auten
AVIATION...Smith
CLIMATE...Auten


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