Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 271906
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
206 PM CDT Sun Jul 27 2014

.DISCUSSION...
ISSUED 200 PM CDT Sun Jul 27 2014

18z Surface map indicating cold front has shifted into extreme
southern Illinois with a secondary boundary/dew point dicontinuity
located from near Chicago southwest to Bloomington to just south
of Quincy. Early afternoon temps have risen into the mid to upper
80s with dew points still in the 70s to the east of the secondary
boundary, with upper 50s to lower 60 dew points filtering southeast
into west central IL. Along and just to the east of this dew point
discontinuity, widely scattered showers and thunderstorms have
developed. Local objective analysis indicates Mixed Layer Capes of
1500-2000 J/Kg to the east of boundary with minimal low level
convergence noted at 18z. 0-6km bulk shear values in the 50-60 kt
range, so any strong updraft along the boundary will have the
capability of producing gusty winds. Visible satellite data showing
quite a bit of wrap around moisture shifting south into the lower
Great Lakes early this afternoon as an upper level trof shifts
southeast.

SHORT TERM...Tonight through Wednesday

Main forecast challenge this period will be with temperatures and
amount of cloud cover and possible showers associated with the
aforementioned Great Lakes trof as it slowly settles south into
the upper Midwest early this week. Models in decent agreement with
respect to the trof deepening in over the Great Lakes this week.
As the cooler temps aloft and high based cu field settle south,
we may see some shower activity across the northeast into early
this evening but several of the hi-res models suggest the bulk of
the shower threat should be east of our area by early this eve so
at this point will keep the evening portion of the forecast dry.
Forecast soundings have suggested the potential for some ground fog
development by morning but with as much mixing that is occurring
this afternoon, will hold off mentioning for now. The southeast may
be close as they will be last to really mix out later this afternoon,
but even there will keep it out of the forecast.

Rather quiet weather expected over the remainder of the forecast period
with the upper trof settling south over the next several days. As temps
aloft continue to cool, our chances for some diurnally driven showers
and storms will increase, especially as we head towards midweek and
beyond. Latest NAM-WRF model indicates parts of our area may see some
afternoon showers tomorrow afternoon. Think that model may be too
strong aloft with the trof and associated cold pool so will tend to
side more with the GFS solution in keeping the area dry for tomorrow.
Temperatures will be cooler than normal but on the pleasant side with
afternoon temps in the mid to upper 70s tomorrow and Tuesday and around
80 by Wednesday with early morning lows in the mid 50s to near 60.

LONG TERM...Thursday through Sunday

Low ensemble spread with the trof expected to drop south into the
Ohio Valley by the weekend. The real challenge will be how the
medium range models handle the individual shortwaves rotating thru
the trof and combining with daytime heating and cool temperatures
aloft to bring about daily chances for mainly afternoon and evening
showers during this period. 850 temp progs suggest not a great deal
of temperature change during this period. We should edge back to
or just above 80 for daytime highs with early morning lows around
60 degrees.

Smith
&&

.AVIATION...
ISSUED 1255 PM CDT Sun Jul 27 2014

One cold front has passed southeast of IL by early afternoon with
scattered strong to severe thunderstorms ahead of it over OH and
eastern KY. Meanwhile another frontal boundary delineated by
enhanced narrow band of cumulus clouds extended from the south side
of Chicago through BMI airport to Jacksonville. Tropical/muggy
dewpoints in lower to middle 70s se of this boundary, while dewpoints
fall through the 60s and even some upper 50s over IL river valley.
Isolated convection recently developed along and just ahead of
this boundary southeast of BMI. Will carry VCSH at southeast airports
of DEC and CMI next few hours until this boundary passes se of
them during mid afternoon. Have scattered cumulus clouds 2.5-5k ft
this afternoon and broken at times from I-55 se next few hours
with high end MVFR ceilings possible. Broken cumulus cloud field
over WI/MN and central/ne IA could skirt northern taf sites of PIA
and BMI later this afternoon and early evening. Breezy WNW winds
12-17 kts with gusts 18-25 kts this afternoon and early evening to
diminish to 7-10 kts after sunset. Drier air advecting into
central IL should limit fog development overnight to patchy
shallow ground fog near rivers/streams especially in southeast IL,
so kept out of TAFS. Expect NNW winds 9-14 kts by 15Z/10 am Monday
with few gusts near 20 kts by midday Monday as scattered cumulus
clouds around 4k ft redevelop.

07
&&

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

$$






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