Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Lincoln Illinois
605 am CDT Sat Apr 25 2015

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 area...as 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
week...as 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 either...so will
keep Wednesday dry at this time. This feature basically represents
the best chance of any rain next week...as 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 12z tafs through 12z Sunday morning)
issued at 605 am CDT Sat Apr 25 2015

Scattered heavier precipitation over western Illinois is expected to
fill in over the next few hours as strong dynamics associated with
left exit region of jet streak over the arklatex region. NAM time
heights indicate strong deep lift for a period this morning which
should increase rainfall rates and play havoc with ceilings. Will keep
predominate ceilings MVFR for now. As the warm front southwest of the
terminals begins to surge north may have lowering ceilings this
afternoon following the main precipitation area. Will try to trend this
possibility with so much uncertianty by keeping MVFR ceilings and
visibilities in place though there could be spots where IFR ceilings will be
possible. Once the main wave pushes east of the area overnight may
be some partial clearing. Northeast winds are expected to be
significant enough tonight to limit any br visibility drops.

&&

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

$$

Short term...Barker
long term...geelhart
aviation...Barker

National Weather Service Glossary of Abbreviations