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Area forecast discussion 
National Weather Service Lincoln Illinois
104 PM CDT Sat Apr 25 2015

issued at 1114 am CDT Sat Apr 25 2015
storm system still well out to the west this morning as first
round of precipitation spread across central Illinois. A short
break in the heavier rainfall possible, though some showers and
thunderstorms will continue to develop, but more scattered in
nature as the low tracks towards the region. Hrrr and NAM both
persistent in development of second round later this afternoon
after 18z. Although the heavier rainfall seems to be projected for
south of a line from roughly Springfield to Paris...some scattered
activity north to the I-74 corridor cannot be ruled out. Some
minor updates, but mainly a wet and showery afternoon with temperatures
hanging up in the 50s. Bigger threat for potential severe
development still in the afternoon hours when the warm front lifts
into the southern County Warning Area...but the trend in the models has been an
increasingly southern track for the low.


Short term...(today)
issued at 228 am CDT Sat Apr 25 2015

Vertically stacked system continues to weaken as it moves across the
plains and into the Mississippi Valley today. Models are relatively
consistent in tracking the associated surface low just southwest of
the forecast area along a warm front that is expected to push into
southern Illinois today. Models from the 00z suite continue to
reflect that even our southeast Illinois counties should remain in cool
sector...suggesting the biggest threat will be from hail and
possibly damaging winds depending on how far north of the warm front
the threatened area develops. Will also have to watch the progress
of the front as there is potential for supercell development along
and just north of the boundary. Bulk shear 0-6km of 40-50 kts is
forecast for south of I-70.

Periods of overrunning precipitation will persist through the day
given our position with respect to the front. Best lift evident
between 12z and 16z. With very moist flow advecting into the area
(shv sounding from 25/00z had 1.84 in. Of precipitable water which
is near the record level for this time of year) rainfall amounts
will likely exceed an inch through most of the forecast area.
Precipitation and abundant clouds should keep temperatures below normal.

Long term...(tonight through friday)
issued at 228 am CDT Sat Apr 25 2015

Have limited evening thunder chances to the southeast part of the
forecast surface low should be sliding across the south
tip of the state by that point. Otherwise...rain chances to quickly
erode from northwest to southeast this evening as the low pulls away.

Persistent northeast flow expected across the area early next an upper low slowly moves out of the Desert Southwest into
the Southern Plains and another spins over New England. Surface high
pressure between these systems will keep things dry from Sunday
through Tuesday. Longer range models keep the precipitation with the
southern low south of our area through middle week. However, a
shortwave moving through the Canadian prairies and the north central
U.S. Will be entering the Midwest by Tuesday evening. A small piece
of energy may cut off in this wave...but there is not good agreement
in the models as to where and how strong. The European model (ecmwf) is wettest and
most progressive with the wave and pinches off a low in the trough
over Southern Lake Michigan on Wednesday...while the GFS and
Canadian models do this about 18 hours earlier in southwest
Minnesota. Ensembles do not show much agreement will
keep Wednesday dry at this time. This feature basically represents
the best chance of any rain next an upper ridge begins to
build across The Rockies and into the plains late in the week. This
trend will result in a gradual warming trend during middle to late
week...with highs in the 70s expected to finally return.


Aviation...(for the 18z tafs through 18z Sunday afternoon)
issued at 1251 PM CDT Sat Apr 25 2015
concern through the near term is the continuing IFR and scattered
LIFR ceilings as the low approaches the ilx terminals. Brief clearing
will remain possible through portions of the afternoon as the
atmosphere gets a bit of a diurnal influence...but any breaks will
be brief with the low in such close proximity and central Illinois
firmly back in the cold air. Chance for scattered thunder still
potential, particularly in the southern terminals around 20z
through 00z. Clearing from west to east expected in the overnight
hours as the system moves out of the region. Tomorrow morning
forecast anticipated to be mild...concern still remains for
potential reduction of visible with the increased relative humidity in the boundary
layer but as is, the winds should stay up enough to counter.


Ilx watches/warnings/advisories...


short term...Barker
long term...geelhart

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