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Area forecast discussion 
National Weather Service Lincoln Illinois
324 am CDT Wednesday may 6 2015

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 06z tafs through 06z Wednesday night)
issued at 1150 PM CDT Tuesday may 5 2015

Frontal boundary sitting just south of I-74 across the area.
Dewpoints are pooling along this front and should continue this
way through the night. Near where rain occurred this evening, fog
has developed, with bmi being the lowest at this point. MVFR
conditions at pia with IFR at bmi. Awss at bmi is reporting a ceiling
at 2oo ft, but remarks says it is scattered sometimes, so will
have tempo broken in the taf at issuance time. Cmi could see some
fog since the front is south of the taf site. Temperature/dewpoint spread
at cmi is 6deg so will just have a tempo for lower visible in the
tafs. Spi and Dec should remain south of the front and pooling
moisture so expecting VFR conditions there overnight. Conditions
will improve tomorrow morning as the front moves north of I-74.
Pia/bmi/cmi winds will be northeasterly north of the front. Spi
and Dec will see southerly winds overnight. With the front lifting
north tomorrow, all sites will have southerly winds tomorrow.


Ilx watches/warnings/advisories...


Short term...Onton
long term...hjs

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