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Area forecast discussion 
National Weather Service Lincoln Illinois
236 am CDT Fri Oct 24 2014

Short term...(today)
issued at 235 am CDT Friday Oct 24 2014

A weak short wave continues to move through the eastern parts of the
County Warning Area this morning, but this should be out of the state by time the
new forecast is issued, or shortly after. The main concern this
morning is the development and advection of stratus clouds and fog
early this morning. Dense fog is present across most of eastern Iowa
this morning and the hrrr model advects this into the area for this
morning. This will keep lots of clouds in the area for this morning,
and could affect Max temps for this afternoon, depending on how
quickly the clouds dissipate. Models have it diminishing during
the late morning hours. And with winds becoming southerly by
afternoon, believe some dissipation of the clouds will happen. So
will have less clouds during the afternoon. However, afternoon
high temps may not be as high as first forecast, so have decreased
Max temps 1-2 degrees from previous forecast. Mav guidance is
higher than met by several degrees, so took a compromise between
the two due to cloud cover issues.


Long term...(tonight through thursday)
issued at 235 am CDT Friday Oct 24 2014

Main forecast issue this weekend and into Monday involves
temperatures. Latest model runs for Saturday have been warmer, as
main core of cooler air associated with a frontal boundary track
more across the Great Lakes region. Have bumped up Saturday highs by
a couple degrees. 850 mb warm front progged to lift through the area
late Saturday night and early Sunday, with +16c temperatures
spreading across central Illinois Sunday afternoon, lingering into
Monday. Have also raised highs several degrees both Sunday and
Monday, with a few 80 degree readings possible on Monday across
southwest and southeast portions of the forecast area. Record highs
for Monday are in the mid 80s and currently appear safe.

Split upper flow early next week focuses the deeper part of the next
wave along the northern stream. Model guidance is fairly uniform
with rain chances Monday night through about midday Tuesday, and
pretty much has the forecast area dry by sunset as a high pressure
ridge quickly builds into the mid-Mississippi Valley. However, the
guidance diverges later in the week. The European model (ecmwf) persists in a rather
broad trough along the Mississippi River midday Thursday, but now
significantly ramps up rain chances along the associated surface
front. The GFS has a weaker, more progressive wave with little
precipitation. Have leaned more toward the progressive solution for
now. The European model (ecmwf) also persists in developing a large closed low over
the Great Lakes late week, which would pump significantly cooler air
into Illinois. Meanwhile, the GFS builds a ridge eastward, with much
warmer air (850 mb temperatures range from -5c to +8c between the
two models). However, this particular aspect is just beyond the
current forecast range, but will need to be addressed with the
afternoon forecast issuance.


Aviation...(for the 06z tafs through 06z Friday night)
issued at 1141 PM CDT Thursday Oct 23 2014

A trailing shortwave feature will produce a few additional
showers over east central Illinois until 9-12z, but otherwise mid- and
upper-level clearing overnight will allow areas of fog and low
cloud to continue, especially west of the Illinois River.
Potential IFR or worse vsby/cigs expected, however potential for
dense fog is mainly west of central Illinois taf sites. Daytime heating
expected to dissipate fog around 15z Friday leaving cloud cover
scattered-bkn025 through afternoon. Another weak disturbance will bring
additional potential for MVFR ceilings after 00z Saturday.


Ilx watches/warnings/advisories...


Short term...auten
long term...geelhart

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