Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 130747

Area Forecast Discussion
National Weather Service Lincoln IL
247 AM CDT Sun Jul 13 2014

ISSUED 247 AM CDT Sun Jul 13 2014

SHORT TERM...Today through Tuesday

07z/2am surface analysis shows cold front extending from near
Chicago to just north of Kansas City. Line of convection
ahead of the boundary is currently impacting the northern KILX
CWA, generally along and north of a Rushville to Bloomington line.
Convection is being aided by a modest 30-35kt 850mb jet streak that
is progged to shift northeastward and weaken toward dawn. As a
result, think storms will gradually dissipate as they sink southward
toward the I-72 corridor. Based on radar timing tools, will go
with a dry forecast north of Peoria today. Further south, will
carry chance POPs as areal coverage of storms continues to
decrease later this morning. Due to the very heavy rainfall that
occurred across portions of east-central Illinois yesterday
morning, will continue the Flash Flood Watch through 18z for
locations along and northeast of a Bloomington to Mattoon line. Do
not think additional flooding is a major threat, but with
weakening showers/thunder coming into the picture this morning,
did not want to cancel the Watch early.

Cold front will sag into south-central Illinois this afternoon,
with storm re-development expected. Airmass ahead of the boundary
will become quite unstable, with surface dewpoints in the lower to
middle 70s contributing to CAPE values of 2500 to 3000J/kg.
Primary mitigating factor for severe storms will be weak 0-6km
bulk shear values of around 25kt. Despite lack of wind shear,
strong instability and decent convergence along boundary will be
enough to trigger a renewed round of strong storms across the
southeast KILX CWA later today. DAY 1 convective outlook from SPC
highlights areas along/south of I-70 and think this looks good
based upon NAM and 4km WRF-NMM forecasts. As a result, will go
with likely POPs across the far SE late this afternoon into the
evening. Main threats from any storms later today will be gusty
winds and hail.

Front will drop south of the Ohio River tonight, bringing an end
to the rain chances across the SE overnight. Meanwhile, secondary
re-enforcing cold front associated with unseasonably deep upper
low centered over southern Canada will arrive on Monday. With
500mb temps progged to drop into the -10 to -12C range during peak
heating, steep lapse rates will contribute to scattered
shower/storm development. Once this front passes, a much
cooler/drier Canadian airmass will arrive Monday night into
Tuesday. Low temperatures early Tuesday morning will dip into the
lower 50s while afternoon highs will only reach the lower 70s.

LONG TERM...Wednesday through Saturday

Deep upper trough anchored over eastern Canada into the Great
Lakes will be the primary weather-maker across central Illinois
through the end of the week. End result will be below normal
temperatures with highs in the 70s and lows in the 50s through
Thursday. After that, trough will weaken and lift further away
from the region, resulting in rising upper heights and warming
temps. Highs will gradually return to the 80s by Friday and
Saturday: however, presence of surface ridging will ensure dry
weather and low relative humidity values through the period.


ISSUED 1152 PM CDT Sat Jul 12 2014

VFR conditions from around KAAA southward with isolated MVFR
conditions to the north. Conditions will deteriorate overnight as
a cold front sags southward across the region bringing a line of
showers with embedded thunderstorms containing heavy rain, and
isolated strong wind gusts. Winds southwesterly around 5-10 kts
until the passage of the front when winds become more westerly.
Precip ending before sunrise in the NW may bring reduced vis due
to fog in the wake of the system. Will keep a subtle reduction of
visibility for the early morning hours in PIA and BMI but should
the mid deck maintain solid coverage, the vis drop will be
minimized. For Sunday...mention of VCTS/TSRA is gradually removed
from TAFS after 11Z-21Z as probability becomes too low once the
front moves east. After 00Z...SHRA/TSRA and areas MVFR conditions
expected to be confined to areas south of KMTO.


FLASH FLOOD WATCH until 1 PM CDT this afternoon FOR ILZ038-


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