Area Forecast Discussion
Issued by NWS Central Illinois
FXUS63 KILX 271156
Area Forecast Discussion
National Weather Service Lincoln IL
656 AM CDT Sun Jul 27 2014
ISSUED 245 AM CDT Sun Jul 27 2014
Sfc map a mess in the wake of yesterday evenings convection. Broad
sfc trof/frontal boundary hung up over the region with light and
variable winds. Some patchy fog out there, with only a couple
sites dropping to a mile vis this morning. Some convection blowing
up over the area turning over some of the air and helping to block
much more of a vis drop in that area...and potentially limiting
the temp drop predawn. Even high res short term models not
handling the current conditions well, much less the next 12 hours.
Many mesoscale dynamics out there not being represented. Front
still not yet through the region...and first issue with the
forecast will be hanging on to pops, particularly in the east with
the frontal passage later mid day and this afternoon.
SHORT TERM...Today and tomorrow...
Keeping chances in for scattered showers and thunderstorms until
the front can progress through the area. Though today is expected
to get warm in front of the boundary...tomorrow is expected to see
signif cooler temps with some relatively drier air filtering in.
Precip chances drop out of the forecast for tonight and tomorrow.
But it bears mentioning that todays pops will be complicated by
small perturbations that are not being resolved well in the
models. HRRR is closest with some approximation of the line of
showers and thunder across central ILX...and some reflection of
the wave interacting with the stalled boundary out in KS. NAM also
trying to key in on it...though it dissolves rather quickly in the
HRRR, and the NAM sends it further eastward, diving sw of ILX and
interacting with the boundary later tonight well out of ILX. More
eastward progression with that disturbance may well change the
outcome of the mid day and afternoon ts chances.
LONG TERM...Tuesday through Saturday...
Cooler air immediately behind the front begins to slowly warm back
up on Tuesday by a few degrees a day. Northwesterly flow dominates
and a deep low digging in a trof over the eastern half of the
CONUS. From mid week on, chances begin to increase with afternoon
instability showers under the deepening cyclonic flow aloft, with
a more stormy afternoon summer pattern. But will be very scattered
and low in coverage. Timing with the next wave diving into the
trof aloft bringing better chances...is lacking continuity in
models. End of the week have better chances for some rainfall...
but certainty and coverage will keep the chances low and diffuse.
ISSUED 655 AM CDT Sun Jul 27 2014
Cold frontal boundary pushing into central IL roughly aligned from
KSPI-KAAA-KBMI as of 1130Z. Along the boundary a combination of a
shower band and locally dense fog is noted in surface obs and
radar imagery. Another hour or two of IFR-VLIFR vsby/cigs in fog
possible before daytime heating raises ceilings. Isold tsra will
remain possible in the vicinity of the boundary through this
afternoon causing isold mvfr vsby/cigs, but probabilities are too
low for mention in TAFs. Cloud cover becoming sct-bkn030-050
after 14Z. After 00Z- 02Z...clearing skies expected. Light winds
becoming NW and increasing to 12-18G20-25 kts through 18Z. Winds
becoming less gusty after 00Z and gradually decreasing overnight.