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Area forecast discussion 
National Weather Service Lincoln Illinois
1217 am CDT Monday may 25 2015

Update...
issued at 859 PM CDT sun may 24 2015

A shortwave upper level pressure trough will eject northeastward
from eastern Kansas toward northwest Illinois overnight promoting a strong low
level jet through western Illinois and associated 0-6 km bulk
shear into western Illinois. Combined with instability to around
1000 j/kg cape...severe thunderstorms remain possible from about
midway between I-55 and I-57 westward through the evening. An
isolated tornado still not out of the question with any rotating
storms...and a Tornado Watch is in effect for these areas until 1
a.M. Instability will wane overnight as nighttime cooling
develops. Nevertheless...showers and thunderstorms will become
likely across central Illinois overnight as lift associated with
the shortwave crosses the region. In the warm humid air mass
behind a warm front that crossed earlier today...lows in the middle
and upper 60s can be expected...and breezy winds 15-20 miles per hour
continuing. No major updates expected this evening except short
term adjustments for current convective trends and
temperatures/wind trends.

&&

Short term...(tonight)
issued at 230 PM CDT sun may 24 2015

Thunderstorms are beginning to become more widespread across
central/southern Missouri in conjunction with a mesoscale convective
vortex (mcv) generated by an upstream storm complex last night.
These cells are lifting mainly northward and will stay west of the
Mississippi River late this afternoon into the evening. Further
east...widely scattered thunderstorms will develop across the
western half of the kilx County Warning Area...however weak wind shear and an
overall lack of forcing will keep areal coverage to a minimum into
the early evening. Stronger forcing will gradually arrive as a
short-wave trough evident on 19z/2pm water vapor imagery across
Texas lifts northward into the region later this evening. High-res
models continue to delay the onset of widespread convection...with
the latest hrrr suggesting that east/NE parts of the County Warning Area will likely
remain dry until after midnight. Have tailored rain chances
accordingly...with likely probability of precipitation gradually overspreading all locations
southwest of a Bloomington to Paris line during the evening...then
further northeast across the remainder of the area overnight.
Despite arrival of stronger lift associated with Texas
wave...waning instability after sunset will prevent widespread
severe weather from materializing...although a few cells could
produce gusty winds and small hail.

Long term...(monday through sunday)
issued at 230 PM CDT sun may 24 2015

Short-wave trough will extend from northern Missouri to southern
Illinois by 12z Monday...then will quickly lift northward into the
Great Lakes by midday. Once feature passes...short-wave ridging
in its wake will create synoptic subsidence and a dry afternoon.
Will still need to watch for potential mesoscale boundaries from
the overnight convection...as these could possibly trigger
additional storms later in the day as the airmass becomes
moderately unstable. At this time...think subsidence and
middle-level drying behind the wave will prevent convection...so
will go with a dry forecast in the afternoon. Main story on
Monday will be the windy and very warm conditions. Models are
showing a 50-55kt 925mb jet developing from the Ozarks to the
southern Great Lakes later tonight. As mixing begins to take
place Monday morning...some of this higher momentum air will be
transferred to the surface resulting in gusts of 30-35mph.
Thanks to the strong southwesterly winds and clearing
skies...high temperatures will soar well into the 80s.

The next upstream short-wave currently over Arizona will round the
base of The Rockies trough and lift into Illinois on Tuesday.
Models continue to be in good agreement with the strength and timing
of this feature. Will bring probability of precipitation back into the picture after
midnight Monday night...then will go likely across the board on
Tuesday. Latest day 3 convective outlook from Storm Prediction Center features a slight
risk for severe along/south of I-70 on Tuesday...however widespread
convection in the morning will likely limit instability for much of
the day. Latest NAM shows sbcapes increasing to 1500j/kg across the
southeast County Warning Area late in the day...while 0-6km shear remains quite weak at
around 25kt. While isolated strong storms cannot be ruled
out...widespread severe weather seems unlikely in the outlook area.

Once this wave exits the region...forcing once again becomes meager
for the remainder of the week. A subtle wave may pass through
Illinois on Wednesday...so have maintained low chance probability of precipitation at that
time. Thursday still appears to be the overall driest day of the
week...with only slight chance probability of precipitation and high temperatures well into the
80s. By the end of the week...a more significant northern-stream
wave will begin pushing a cold front toward Illinois. Still some
model discrepancy with the timing of that process...but trends are
suggesting enhanced rain chances will hold off until Friday night
through Sunday.

&&

Aviation...(for the 06z tafs through 06z Monday night)
issued at 1217 am CDT Monday may 25 2015

Showers and isolated thunderstorms will continue through early
morning. Isolated MVFR ceilings/visibilities possible in showers early in the
night...while model time-height sections and upstream
observations indicate predominant ceilings lowering to MVFR
overnight. Diminishing rain showers/thunderstorms and rain activity early in the morning
resulting in VFR conditions after 15-18z through the evening.
Winds S 10-20 kts...decreasing to around 15 kts for Monday
afternoon/evening.

&&

Ilx watches/warnings/advisories...
none.
&&

$$

Update...Onton
short term...Barnes
long term...Barnes
aviation...Onton

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