Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 191434

Area Forecast Discussion
National Weather Service Lincoln IL
934 AM CDT Thu Apr 19 2018

Issued at 934 AM CDT Thu Apr 19 2018

Stratocumulus deck continues to push southward this morning, with
the northern fringes roughly along I-72. The clearing trend across
the southern CWA will continue through early afternoon, while
sunshine prevails elsewhere the rest of the day. New zones/grids
recently sent for the updated sky trends. Temperatures and winds
looked good and only needed minor adjustments.


.SHORT TERM...(Today and tonight)
ISSUED AT 330 AM CDT Thu Apr 19 2018

Issued another freeze warning for our 8 southeast IL counties
along and south of I-70 overnight from 1-8 am cdt Friday. Clear
skies and light to calm winds to give good radiational cooling
with lows of 28-32F. This is the 3rd freeze waring for southeast
IL this week.

09Z/3 am surface map shows 1002 mb low pressure over central VA
while a weak surface trof hangs back into northeast IL. Meanwhile
a 1031 mb Canadian high pressure extended from southeast Saskatchewan
into the central Dakotas and ridging southward across the central
plains. Radar mosaic shows main area of light snow was over
northeast IL, ne of Pontiac and over northern half of IN, north of
Indy and tracking se. Had scattered flurries over central IL,
north of I-70, early this morning. Aloft a 545 dm 500 mb low was
along the northern OH/IN border and this upper level trof extended
into central IL. Broken to overcast stratocumulus clouds covered
IL early this morning. Chilly temps were in the 32-36F range over
central IL, and 35-39F in southeast IL. Brisk nw winds of 10-17
mph and gusts 18-25 mph was giving wind chills in the low to mid

Upper level low forecast to lift into the St Lawrence valley and
northern New England during this afternoon, while Canadian high
pressure strengthens to 1034 mb as it drifts into northern/nw IA.
Scattered flurries to push se of CWA shortly after sunrise while
low clouds decrease from nw to se during this morning, giving way
to ample sunshine this afternoon. Highs of 50-55F this afternoon
with NNW winds 8-15 mph and gusts to around 20 mph to make it feel
cooler. High pressure ridge to be over the upper MS river valley
and ridging into IL by dawn Friday. This to bring clear skies,
light winds and a widespread freeze with lows of 26-32F. Being the
growing season has started along and south of I-70, had to issue
another freeze warning overnight for 8 southeast IL counties.

.LONG TERM...(Friday through Wednesday)
ISSUED AT 330 AM CDT Thu Apr 19 2018

Canadian high pressure settles east into the Great Lakes region by
Friday afternoon, while upper level ridge shifts east into the MS
river valley by sunset Friday. Ample sunshine Friday and east to ENE
winds less than 10 mph, with a bit milder highs in the upper 50s and
lower 60s. Clouds to increase over central IL overnight Friday
night while southeast IL stays with fair skies longer during
Friday night. Not as cold Fri night with lows in the mid to upper
30s Friday night, coolest in eastern IL.

A 550 dm 500 mb low off the central CA coast will track into the 4
corners are by midday Friday, and into western OK and nw TX
panhandle region on Saturday. Meanwhile weak upper level ridge
lingers over IL while high pressure also stays over the southern
Great Lakes region, keeping central and southeast IL dry with
partly to mostly cloudy skies. Highs in the upper 50s and lower
60s again on Saturday.

Cutoff upper level low moves to near Memphis by sunset Sunday and
keeps most of its showers south of IL, though some models have
light qpf as far north as I-64. Partly to mostly cloudy skies
Sunday, with more clouds over sw portions of CWA. Upper level low
moves into northern AL/southern TN river valley Monday and pivots
light moisture nw into KY and southeast parts of MO/IL/IN,
possible getting isolated light showers near Lawrenceville Mon
afternoon. Highs Sunday in the low to mid 60s, and mid to upper
60s on Monday, which is close to normal for late April.

Upper level low moves into the eastern TN river valley Tue while a
northern stream upper level trof/short wave tracks into the upper
Midwest. Our CWA should be in between these two system on Tue and
generally dry conditions monday night and Tue. Highs Tue again in
the mid to upper 60s. The surface and upper level low moves into
northern WI and western Lake Superior Tue night and still appears
to push a band of rain showers se across IL during Tue night and
shifting east of IL during Wed with a bit cooler temps Wed/Thu
with highs in the lower 60s.


.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 626 AM CDT Thu Apr 19 2018

A trough of surface low pressure rotating through central IL will
depart to the southeast by 14z or so. A few flurries will still
affect DEC and CMI for an hour or two of the 12Z TAF period, then
clearing skies are expected. Satellite loops show the clearing
line approaching PIA and BMI, with little evidence in the forecast
soundings that significant clouds will redevelop in the heat of
the day. The HRRR does show the forward progression of the
clearing slowing down as it reaches I-72, but the MVFR ceilings
should still dissipate by 17z in that area.

Winds will start out NW, but should shift to the N as the surface
trough shifts east of Illinois. Wind speeds will be a little gusty
this morning, with 12g20kt possible at times. Wind speeds should
become less gusty by this afternoon, but still sustain around
10-12kt. Lighter winds will develop tonight, as high pressure
advances farther into IL and the pressure gradient weakens.


Freeze Warning from 1 AM to 8 AM CDT Friday for ILZ062-063-



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