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Area forecast discussion 
National Weather Service Lincoln Illinois
1243 PM CDT Wednesday may 6 2015

issued at 1045 am CDT Wednesday may 6 2015

Persistent frontal boundary is beginning to lift northward this
morning...with 15z/10am surface observation showing it along a Moline to
Kankakee line. Winds have become southerly across the entire kilx
County Warning Area...allowing temperatures to climb into the upper 70s and lower
80s across all but the far north. Short-wave trough noted on
latest water vapor imagery over Kansas/Oklahoma will lift north/NE
today...however any clouds/precipitation associated with this feature
will remain along and west of the Mississippi River. Further
east...mostly sunny and very warm conditions will prevail with
afternoon highs in the middle to upper 80s. Current forecast is
right on no major changes are anticipated.


Short term...(today)
issued at 324 am CDT Wednesday may 6 2015

Frontal boundary extends from near Macomb to Paris across central Illinois
this morning and cooler temperatures with higher dewpoints north of
the boundary are resulting in areas of fog...with occasional dense
fog observations in Bloomington...and LaSalle and Pontiac to the
north. 7z hrrr model is depicting well the dense area and have
incorporated patchy dense fog in grids according to this. Fog should
dissipate by around 8 am with daytime heating.

For today...a 500 mb ridge axis oriented northwest-southeast across Illinois will shift
northeastward while a shortwave over the Southern Plains ejects
northeastward just west of Illinois. Precipitation associated with
the shortwave will approach the western side of Illinois but will
likely remain just west of the central Illinois forecast area. Forecast
soundings for central Illinois indicate a weak subsidence inversion and
dry air at middle levels which should help to prevent any significant
convection...although enough moisture below the dry subsident layer
could bring scattered to broken shallow cumulus. Southerly flow
ahead of the shortwave will push the frontal boundary northward with
warm air behind the front bringing highs into the middle or upper 80s
across central Illinois. Surface winds expected to be southerly 8-15 miles per hour
with gusts 12-20 miles per hour...the stronger winds toward the western side of
the state.

Long term...(tonight through tuesday)
issued at 324 am CDT Wednesday may 6 2015

Brief dry period will continue through the overnight hours with the
warm temperatures. Storm/wave over the Southern Plains will track
north/northeast but is expected to mostly stay to the west...but
some precipitation chances sneaking into west central Illinois on Thursday,
with the best chances pushing into the evening hours and overnight
for showers and thunderstorms. Bigger system digging into the desert
SW over the next 36 hours or so and will keep the western US under a
trof, amplifying the pattern and setting up southwesterly flow for
the Midwest. Many shortwaves tracking around the trough and up into
the middle Mississippi Valley/Midwest through the end of the weekend
and into the first part of the workweek. Periods of showers and
thunderstorms keep high chance/likely threat in the forecast through
Monday night until the system is slowly driven out of the region.
Still some question as to where the boundary will provide the best
focus and the models are fairly diffuse with the convective
activity. Temperatures remain warm with a pretty stubborn warm
airmass and southerly winds at the surface keeping warm air advection going even with
the showers and least until the trough finally
exits NE and allows cooler temperatures back into the region by day7/day 8.


Aviation...(for the 18z tafs through 18z Thursday afternoon)
issued at 1243 PM CDT Wednesday may 6 2015

Southerly winds gusting to around 20kt will continue through the
afternoon before subsiding to less than 10kt and backing to
southeasterly this evening. Skies will be partly sunny as cumulus-field
seen on latest visible satellite imagery expands northward. Cloud
bases are around 7000ft as per surface observation and rapid refresh
forecast soundings. May see an occasional broken ceiling...but
cloud coverage will generally be scattered this afternoon. These
diurnal clouds will quickly dissipate toward sunset...however an
area of middle-level clouds associated with a short-wave over the
plains will cross the Mississippi River into west-central Illinois
this evening before gradually dissipating overnight. Have
introduced VFR ceilings of around 10000ft at both kpia and kspi
after 03z accordingly. Mostly clear skies will be the rule by
Thursday morning...with gusty southerly winds resuming.


Ilx watches/warnings/advisories...


short term...Onton
long term...hjs

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