Area Forecast Discussion
Issued by NWS Central Illinois
FXUS63 KILX 012149
Area Forecast Discussion
National Weather Service Lincoln IL
349 PM CST Sat Mar 1 2014
ISSUED 310 PM CST Sat Mar 1 2014
SHORT TERM...Tonight through Tomorrow night...
Storm developing over the west coast, expected to move in and move
along an elongated piece of energy hovering with the quasi
baroclinic zone across the Midwest. The initial impact of
precip/snow for the FA will be frontogenetic in nature before
changing over to more of a deformation zone. Details are changing
as far as the duration of the precip, now ending sooner...the
thermal profiles, altering ptype...and the locations of the best
heavy snowfall potential. All models have been backing off of
precip at times, while still pointing to banding and mesoscale
enhancements to the snowfall. Enough borderline conditions in a
couple of time frames to raise concerns for impact based warnings.
Changed the product headlines across the area to reflect this. One
major concern is the changing thermal profile in the SE. Should
the evaporative cooling eliminate the very subtle warm layer in
the mid levels (GFS is far more subtle and shallow than the NAM),
the QPF will be even more dedicated to snow. This would result in
higher amounts. This, in addition to the proximity to the greatest
chance for mixed precip and signif ice potential, is the reason for
the Winter Storm Warning. Though criteria may be missed as this is
over more than a 24 hr time frame...impact and collaboration have
resulted in that warning decision. Elsewhere...the QPF is
currently outside of the warning criteria over any 24 hr pd and
trending down. That being said, a lot of snow is coming.
Isentropic lift is weak at best over ILX, more signif to the
south. Fn vectors maxed over saturated 1000-500mb RH supporting
the frontogenetic forcing from 03z-12z over ILX. At that point the
movement stalls somewhat as the sfc system begins to develop over
the southwest and move NE through the region. Where exactly the
storm stalls will greatly impact ILX. Too far south and the totals
may need to be knocked down even further. A little further to the
north and the weak deformation region will shift. HPC snow totals
not in complete agreement with the QPF, and as a result have kept
the warning area as conservative as possible. Situation will be
very subject to adjustments through the overnight hours. Last
couple runs have brought the precip to an end sooner...with the
NAM and the GFS both out of the CWA by 12z Monday morning.
LONG TERM...Monday through Friday...
More cold air for the extended. Mon-Thursday still well below
freezing. Although Friday is showing signs of a warm up, the WAA
looks a bit weak at this point. Brief waves bringing quick shot of
precip possibly on Wed across the north. Otherwise, dry beyond
the current storm.
ISSUED 1146 AM CST Sat Mar 1 2014
Complicated scenario for this TAF set. MVFR conditions this
afternoon have briefly popped up to ceilings over 3000 feet in
some places and into IFR range in others. Also have had some
recent reports of some freezing fog just northwest of KSPI. Main
onset of widespread IFR conditions will be this evening, as snow
rapidly spreads across the TAF sites in the 01-05Z time frame.
Latest high-res models diminish the heavier snow for a time around
KPIA/KBMI late tonight before the next surge northward during the
daylight on Sunday. Have added blowing snow mention after 12Z as
winds ramp up into the 15-20 knot range.
WINTER STORM WARNING from Midnight tonight to 6 AM CST Monday
WINTER WEATHER ADVISORY until 6 PM CST Sunday FOR ILZ027>031-
WINTER WEATHER ADVISORY from Midnight tonight to 6 AM CST Monday