Area Forecast Discussion
Issued by NWS Central Illinois
FXUS63 KILX 302046
AREA FORECAST DISCUSSION
National Weather Service Lincoln IL
246 PM CST MON NOV 30 2015
ISSUED AT 240 PM CST MON NOV 30 2015
Initial batch of light rain has exited the forecast area early this
afternoon, however some patches of drizzle were persisting in the
low stratus. Next wave of light rain was crossing the Missouri
border near Quincy as of 2 pm, with some light rain/drizzle seen on
radar as far southwest as southwest Missouri. Have concentrated the
highest PoP`s into this evening across areas west of I-55 and
increased them somewhat.
Latest water vapor imagery showing large upper low centered over
Nebraska this afternoon. Dry slot is spreading northeast out of
Oklahoma and Kansas, and marks the back edge of the precipitation
shield along the cold front. A steady decrease in rain chances will
occur from west to east after midnight as this drier air arrives.
Latest RAP guidance suggests the cold front moving into areas near
the Illinois River in the 2-3 am time frame, reaching the Indiana
border toward 6 am. Until the front gets here, temperatures across
the forecast area likely to remain fairly steady this evening, and
most of the night across eastern Illinois.
.LONG TERM...(Tuesday through Monday)
ISSUED AT 240 PM CST MON NOV 30 2015
The slow moving upper low is forecast to be located over extreme
northwest Iowa Tuesday morning with a well defined dry slot pushing
into southwest Illinois. Most of the rain that occurs overnight
should be off to our east Tuesday morning with a decrease in cloud
cover from southwest to northeast during the morning. Soundings
continue to suggest gusty southwest winds during the day with
temperatures at or just above normal again, mostly in the 40s. The
upper low is then forecast to shift mostly east into southern
Wisconsin by Wednesday morning, which is a bit further south than
what we had been seeing, although the 12z ECMWF from yesterday was
hinting at this. The surface low will push across the lower Great
Lakes as well with a shortwave pivoting southeast into the area late
Tue. night into Wednesday morning which may bring some patchy light
snow or flurries to parts of the area.
With the further south position of the upper/surface lows, the wrap-
around moisture will drive further southeast into our forecast area
as well with some low chance POPs on Wednesday for flurries in the
morning, and sprinkles or flurries in the afternoon as the low level
cyclonic flow dominates into Wednesday night/early Thursday.
Temperatures will be colder as well during the day Wednesday with
afternoon readings in the upper 30s far north to the middle 40s
south, which is close to where they should be this time of year. A
rather quiet weather pattern will prevail through the remainder of
the extended forecast period as the deep upper low shifts away from
the Midwest with 500 mb heights building across the region. This
should result in a gradual moderating trend for the end of the week
with afternoon temperatures by Friday well into the 40s to low 50s.
No sign of any breakdown in the mild pattern for us into early next
week as the main longwave trof will be across the western part of
the country which should result in above normal temperatures for
much of our area through the weekend. A trof is expected to eject
east-northeast into the Southern Plains Sunday and into Missouri by
next Monday bringing a chance for rain to the forecast area.
.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
ISSUED AT 1130 AM CST MON NOV 30 2015
IFR/LIFR ceilings continue to overspread central Illinois. Initial
band of showers has exited most of the TAF sites, but will see
some periods of drizzle and lower visibilities continue this
afternoon until more substantial showers move in from Missouri.
Not much change in earlier thinking on the timing of the cold
front passage between 08-12Z, which will quickly lift ceilings
behind it and VFR should prevail shortly after sunrise. Slow-
moving upper low will result in an increase in ceilings below
3,000 feet from the northwest later on Tuesday, with KPIA most
likely to see these arrive toward midday.