Area Forecast Discussion
Issued by NWS Central Illinois
FXUS63 KILX 270818
Area Forecast Discussion
National Weather Service Lincoln IL
318 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 1157 PM CDT Sat Jul 26 2014
Fog has developed in areas where there was rain this afternoon.
Some places have gotten as low as 1/4sm. MVFR cigs are developing
in the north and expect this to overspread PIA and BMI during the
overnight hours. The dense fog seems to have developed around SPI
and DEC, and unsure if it will get to CMI since CMI site did not
have a lot of rain. So have tried to forecast for LIFR or IFR
conditions at SPI and DEC overnight, with MVFR at PIA/BMI/CMI.
Then all sites will improve to VFR tomorrow morning with scattered
CU developing for the daytime hours. Skies should clear for
tomorrow evening. Winds will be light and variable overnight and
then become northwesterly after the cold front moves through.
There is a slight chance that some showers will develop along the
front late tonight as it encounters the juicy air. But chances are
low and confidence is low, so will not have any mention in TAFs at