Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 191648

Area Forecast Discussion
National Weather Service Lincoln IL
1048 AM CST Sun Feb 19 2017

Issued at 1044 AM CST Sun Feb 19 2017
Low level moisture trapped under the inversion set up the fog this
morning for much of Central Illinois. By mid morning, the fog is
confined to the east and south...and south of the Il River Valley.
Vis sat imagery showing erosion of the fog bank on the north and
south...and erosion from solar radiation through in scattered
spots. However, since it is lingering into the late morning hours,
there is a concern that the high temperatures will be modified
considerably. Have taken the temps in the east down a see
how quickly the airmass can rally once the fog dissipates. May
need another update around midday. Update out momentarily.


.SHORT TERM...(Today and tonight)
ISSUED AT 327 AM CST Sun Feb 19 2017

Dense fog has developed along and east of the I-55 corridor early
this unseasonably warm/moist air flows northward ahead
of a weak trough axis along the Illinois River.  HRRR has been
handling the development and evolution of the fog quite nicely over
the past several have followed its forecast closely in
the short-term.  HRRR shows fog expanding...eventually encompassing
the entire area east of the Illinois River by daybreak.  Based on IR
satellite trends showing the fog spreading as expected...a Dense Fog
Advisory has been issued for all counties east of the Illinois River
until 15z/9am.  This may need to be extended in time for another
hour or two...particularly from Taylorville to Champaign where the
fog will likely persist the longest.  Visbys will rapidly improve
toward midday...with clearing skies noted by early afternoon.  High
temperatures will range from the lower to middle 60s along and east
of I-57 where low clouds will persist the the lower 70s
in the Illinois River Valley where sunshine will be more prevalent.
A cold front will slowly approach from the west tonight, spreading
high clouds across the area overnight.  With ample boundary layer
moisture in place and light winds expected, fog will once again
develop tonight.  Both NAM and GFS soundings show low-level
saturation after 06z.  Think the increasing high cloud cover will
prevent widespread dense fog, but have decided to mention patchy
fog in the forecast overnight.

.LONG TERM...(Monday through Saturday)
ISSUED AT 327 AM CST Sun Feb 19 2017

Cold front will approach from the west on Monday...but with
pronounced upper ridging over the Midwest, think most of its
associated precip will remain west of the Mississippi River until
evening.  Have scaled back PoPs accordingly...with rain chances
mainly confined to locations west of I-55 during the afternoon.  As
the boundary comes into the area, better chances for showers and a
few thunderstorms will arrive Monday night into Tuesday morning.
Despite ridging, all models aggressively push the front through
central Illinois by midday have gone with a largely dry
forecast by afternoon.  Pacific-origin airmass behind the front will
offer little in the way of cooling, resulting in high temperatures
once again in the upper 60s and lower 70s.  Warmest day of the
forecast period looks to be setting up on Wednesday when ample
sunshine, southwesterly winds, and thermal ridging suggest highs
temperatures in the lower to middle 70s.

A potent storm system is still slated to impact the region by the
end of the week...bringing another chance for thunderstorms.  00z
Feb 19 models are in relatively good agreement...with low pressure
tracking from western Kansas Thursday evening to the southern Great
Lakes by Friday evening.  The ECMWF is slightly further northwest
with its track and thus a bit slower with FROPA during the day
Friday.  The big key for this system will be the timing of the front
and whether or not it will have enough time to tap into sufficient
Gulf of Mexico moisture to produce strong to potentially severe
thunderstorms Friday afternoon.  With the faster GFS, its
instability axis shifts eastward into the Ohio River Valley by
18z...thus the threat for any severe weather would likely
materialize further east.  However, the ECMWF is slower and suggests
the eastern KILX CWA could see storm development late in the day.
Given highly amplified nature of this system...think a slower
solution is prudent.  Have therefore extended thunderstorm chances
across the east through Friday afternoon.  After that...much cooler
air will arrive by next weekend...with highs returning to near
normal for this time of year in the upper 30s and lower 40s.


.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 600 AM CST Sun Feb 19 2017

Dense fog will continue to affect the terminals east of the
Illinois river through mid-morning. The fog may change between
1/4sm and 1/2sm during that time, but will lean toward persistent
1/4sm for BMI, SPI, DEC and CMI. Forecast soundings indicate fog
will improve after 15z, with low clouds clearing by late morning.
South to southwest winds will remain less than 10 kt today and
tonight. Winds will shift toward the southeast and remain light
tonight. Fog and low clouds are expected to develop again late
tonight, with dense fog possible east of the Illinois river.


Issued at 339 AM CST Thu Feb 16 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


Dense Fog Advisory until 11 AM CST this morning for ILZ031-037-



LONG TERM...Barnes
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