Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

fxus63 kilx 081847 
afdilx

Area forecast discussion
National Weather Service Lincoln Illinois
1247 PM CST Thu Dec 8 2016

Update...
issued at 1044 am CST Thu Dec 8 2016

Short-wave trough currently passing through the area has brought
clouds and scattered snow flurries to much of central Illinois
this morning. 1630z/1030am visible satellite imagery shows cloud
cover blanketing nearly the entire kilx County Warning Area except for locations
along/south of an Effingham to Robinson line where a good deal of
sunshine is still occurring. The clouds are pivoting around a deep
upper low centered over Quebec and are generally tracking to the
east/southeast within the cyclonic flow around the low. Given this
pattern...think the clouds will remain in place for the balance of
the day and into tonight as well. Radar and area obs continue to
indicate occasional flurries, so have extended flurry chances into
this evening. Given the cloud cover and gusty northwesterly
winds, temperatures will not warm much at all today. Afternoon
highs will only be a couple degrees warmer than they currently
are, with readings remaining in the middle to upper 20s.

&&

Short term...(today and tonight)
issued at 349 am CST Thu Dec 8 2016

High pressure ridge is still well west and southwest of the area
which allows the colder air and brief mid level troughs to move
through the County Warning Area. Another weak trough in the northwest flow will be
bringing mostly cloudy skies to a portion of the County Warning Area today.
Observations upstream of central Illinois have reported some flurries with
these clouds, so will be adding flurries in the forecast for this
morning and early afternoon. The area will be roughly along and
north/northwest of I-74. As the trough moves through, dry conditions
will return for late this afternoon and continue through tonight.
West to northwest winds will continue through today and breezy
conditions will continue as well. Gusts of around 25 mph will be
common across most of the County Warning Area. Temps will be below freezing today
with the coldest temps being in the north where most of the cloud
cover will be. Overnight lows will fall into a range of 14-20
degrees by morning. Wind chill readings will be in the single digits
again overnight.

Long term...(friday through wednesday)
issued at 349 am CST Thu Dec 8 2016

Once again the precipitation forecast for the weekend is troubled,
but the cold air snaps are more Concrete. The cold Arctic air
moving into the Midwest for the end of the week will be countered by
some relatively warmer air for the end of the weekend...only to lose
ground to bitterly cold temperatures for next Tuesday and beyond.

Cold Arctic air in place over the area will keep the Max temps in
the 20s for Friday. Winds Friday morning will be up a bit, dropping
wind chills to single digits. The bitter cold will be a bit of a
shock from the mild weather in place for much of the season up to
this point. Temps begin to moderate slightly on Saturday later as
the winds take on a more southerly component and weak warm air advection starts up.

Models have been consistently inconsistent for the weekend. Both the
European model (ecmwf) and the GFS...and to some extent the Canadian shift from
northwesterly flow to more northerly, sheering out a wave across the
Great Lakes for Sat afternoon and overnight. The second wave is now
starting to differentiate from the prev wave with the last few runs
for Sun afternoon and overnight as a surface system develops to the
west-southwest and moves into the mid Mississippi River valley. The questions
remain as to how much of the models are lingering precip too long
and muddying the division of the systems or if the dynamics will be
able to interact and enhance one another. For now...chance pops
dominate...but with some higher pops in for Sunday night and the
better sfc development/deeper wave aloft. Mostly snow anticipated
early... but as the warm air advects into the region...the southern
half of the state could see more rain/wintry mix for Sunday,
particularly in the afternoon.

Beyond the precip issues with the weekend...cold air is coming for
next week. Highs by midweek already showing as teens and low 20s
for Wednesday as a frigid Arctic airmass moves into the Continental U.S..

&&

Aviation...(for the 18z tafs through 18z Friday afternoon)
issued at 1241 PM CST Thu Dec 8 2016

MVFR ceilings will persist at the central Illinois terminals
through the afternoon and likely beyond. Latest satellite imagery
shows widespread cloud cover across the region...with the
southwest edge of the cloud area extending from central Iowa into
southwest Illinois. With deep layer northwesterly flow expected to
persist...think clouds will be very slow to clear later tonight
into Friday. While rapid refresh forecast soundings suggest
clearing skies at kpia as early as 11/12z...the NAM is much more
pessimistic and keeps clouds in place through the day Friday.
Given current and expected flow pattern, have opted to keep
overcast conditions in place at the I-74 terminals through the
entire 18z taf period. Further southwest, trajectories suggest
clearing conditions at kspi and kdec. Exact timing of clearing
remains in question: however, model consensus is between 14 and
16z.

&&

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

$$

National Weather Service Glossary of Abbreviations