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Area forecast discussion 
National Weather Service Lincoln Illinois
255 PM CST sun Nov 29 2015

Short term...(tonight)
issued at 250 PM CST sun Nov 29 2015

High pressure ridge axis stretching from south of Hudson Bay, back
through the Great Lakes and into the upper Midwest. Although the
high is still building, it has lost ground today to the impacts of a
broad area of lift in the Missouri River valley. Precipitation has
slowly edged towards the region, overcoming a very dry layer in the
mid levels. The trend will continue with the moisture driving
precip in west central Illinois this evening. As the column
saturates a bit more, precip will spread across central Illinois
tonight. Precip is mainly an issue of scattered light showers
still...with little in the way of quantitative precipitation forecast. Current radar echoes are
mainly virga and it will be a while before that trend gives way
across much of the state. As a result, have held off until after
06z before the precip spreads into the eastern half of the state.
Lows tonight should remain above freezing with plenty of cloud cover
across the region.


Long term...(monday through sunday)
issued at 250 PM CST sun Nov 29 2015

The sprawling upper low that has been out over The Rockies for
several days is finally forecast by all models to start to push east
on Monday with surface low pressure developing ahead of it over
western Missouri. Stronger forcing ahead of the feature in the left
exit region of a 250 mb jet Max should increase the areal coverage
of rain across the forecast area on Monday. Initially, forecast
soundings across the east still exhibit some very dry air in the low
levels, similar to what we saw today which should keep the bulk of
the precip over western Illinois before shifting over the east during the
afternoon. Despite the better dynamics associated with the upper
wave, the deeper moisture will be to our southeast tied to the
stalled frontal boundary over parts of Tennessee and Kentucky and to
our northwest, closer to the track of the 500 mb low. As a result,
quantitative precipitation forecast amounts will only range from around a quarter of an inch to
nearly four tenths of an inch, with the higher totals across our

The aforementioned surface low will track north to western Iowa by
00z Tuesday with the higher pops maintained during the first half of
Monday night before a mid level dry slot shifts northeast into our
forecast area by 12z Tuesday. The storm system will then track
northeast into Wisconsin by Tuesday afternoon with a gusty southwest
wind across our area, with any lingering low chance pops confined to
the far north. Some fluctuations with the respect to the upper low
seen on the 12z ECMWF, compared to the GFS, Gem and sref which seem
more reasonable at this time. That would take the upper low east-
northeast into central lower Michigan by Wednesday afternoon with
our northern counties more favored for some scattered flurries
Tuesday night and possibly into Wednesday, especially if the European model (ecmwf)
turns out to be right. For now, will keep the slight chance of
flurries for Tuesday night and not have any precip in the forecast
for Wednesday based on the GFS, Gem and sref solutions.

Not a great deal of cold air poised to sweep across our area in the
wake of the storm on Wednesday and Thursday with seasonably cold
temperatures expected. That should be short lived though as upper
level heights build across the center of the nation as troffing once
again establishes itself over the southwest portion of the country.
However, medium range models showing some differences with respect
to shortwave energy tracking across the upper Great Lakes late Thu
into Friday. The European model (ecmwf) digs this feature sharply into the Midwest,
while the GFS and Canadian suggest more of a progressive track to
our north and northeast during this time frame. Whatever solution
works out, the overall affect in our area, at least precip-wise will
be minimal. A wide variation in temperatures were seen though as the
European model (ecmwf) solution would hold back the warming a couple of days, with
the more consistent GFS and Gem solutions pointing towards 50s for
afternoon highs starting on Friday in our west and south, and over
all but our northern counties on Saturday with little in the way of
significant rain or snow seen as we head into next weekend.


Aviation...(for the 18z tafs through 18z Monday afternoon)
issued at 1144 am CST sun Nov 29 2015
925-950mb relative humidity in models a little complex towards the morning
causing some complications in the forecast. Today, mid/high
clouds, and northeasterly winds, 5-10kts, VFR. However, in the
overnight the llvl moisture starting to surge north and east from
the shower activity in the SW. Have timed out the advance of
clouds at 3kft across ilx terminals from 09z-15z. Winds also
becoming more easterly in that time frame. Further adding to the
complications is the shower activity northwest of Illinois River this morning
altering the llvl moisture content. Peoria may end up with
MVFR/IFR conditions before dawn as these current showers were
underestimated in prev model runs.


Ilx watches/warnings/advisories...


Short term...hjs
long term...Smith

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