Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 040549
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1149 PM CST Tue Mar 3 2015

.UPDATE...
ISSUED AT 707 PM CST TUE MAR 3 2015

01z/7pm surface analysis shows cold front approaching the I-57
corridor, with light rain ongoing well ahead of the boundary
across southeast Illinois. Front is expected to settle southward
toward the Ohio River overnight, while several weak upper-level
impulses ride northeastward along it. This will keep precip going
across the SE KILX CWA throughout the night. Further north, there
will be a lull early this evening before an approaching wave
spreads light precip back northward toward the I-72 corridor from
late evening into the overnight hours. Based on the latest Rapid
Refresh forecast soundings, it appears the main precip type will
be rain through 03z, then the rain will gradually mix with
snow/sleet from northwest to southeast overnight. Areas across the
far southeast around Lawrenceville likely will not see any
snow/sleet until after 09z. End result will be some light wintry
precip along and south of a Jacksonville...to Decatur...to
Danville line later tonight. Will only mention flurries along the
northern edge of the precip area. Further south, may see a couple
tenths of snow/sleet accumulation closer to the I-70 corridor
overnight. Forecast update has already been issued.

&&

.SHORT TERM...(Tonight)
ISSUED AT 330 PM CST TUE MAR 3 2015

Freezing rain and sleet developed over western Illinois around
midnight and quickly tracked east over all but extreme southeast
Illinois by 08z/2am. Already seeing the back edge of our second
band of wintry precip entering west central Illinois, so it appears
we will have a brief lull in the freezing rain and sleet. However,
the latest HRRR suggests another band of rain, freezing rain and
sleet will move northeast across our area at or just after dawn
Rainfall rates have not been much with these quick moving bands
of freezing rain/sleet with most areas seeing less than 0.05" per
hour, but certainly enough for some light icing to occur on bridge
decks and overpasses and on lesser traveled roads.

RAP forecast soundings continue to suggest temperatures will rise
above the freezing mark over southeast Illinois by dawn...central
sections of the forecast area by 900 am...and between 10 am and Noon
roughly along and north of the Interstate 74 corridor. By late
morning into the afternoon hours the stronger lift associated with
the low level warm advection/ isentropic ascent shifts off to our
east and southeast with a gradual lowering of POPs warranted from
northwest to southeast. Best 850-700 forcing edges into southeast IL
by mid to late afternoon where our highest POPs will be located.
Guidance temperatures look reasonable for this afternoon with highs
ranging from the upper 30s far north to the upper 40s far southeast.

&&

.LONG TERM...(Wednesday through Tuesday)
ISSUED AT 330 PM CST TUE MAR 3 2015

The cold front currently passing through the forecast area will
stall out south of the Ohio River Valley early Wednesday as it
becomes parallel to the upper-level flow. A 180+ kt jet streak will
be in our vicinity on the cool side of this front/low level
baroclinic zone for much of the day Wednesday. A very small portion
of our forecast area south of I-70 will be at least nicked by the
good frontogenetical forcing/jet dynamics in this flow regime. With
this in mind it is looking like 2-4 inches of snow will fall late
tonight through Wednesday evening across at least Clay, Richland,
and Lawrence counties. There is some model disagreement on where the
axis of heavier snow will set up, and the snow totals may need to
be boosted a little and pushed further north or decreased and pulled
further south depending on future model runs.

The snow threat in southeast IL diminishes later Wednesday night, as
the current system finally pulls away, and another Arctic high
(hopefully the last of the winter) builds into the entire forecast
area. This high will be accompanied by a couple nights of mainly
single digit lows Wednesday night and Thursday night, and highs
mainly in the teens for Thursday.

Temperatures are still expected to gradually moderate beginning
Friday and continuing into next week. High temperatures may actually
be above normal for a change by early next week, with highs in the
50s possible by next Tuesday. The models do not suggest the passage
of any significant system from Thursday-Tuesday, so predominantly
dry weather looks to be the rule through the period.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
ISSUED AT 1149 PM CST TUE MAR 3 2015

MVFR ceilings temporarily cleared at the central Illinois
terminals this evening: however, another patch of lower clouds is
noted on 05z satellite imagery along/west of the Illinois River.
These clouds will spread eastward over the next couple of hours
before clearing out once again later tonight. Latest HRRR suggests
MVFR ceilings will depart KPIA by 09z, then further east to KCMI
by around 13z. Even when the lower clouds exit, a mid-level cloud
deck at 12000-15000ft will remain as low pressure tracks along a
frontal boundary draped along the Ohio River. Any associated
precip will remain south of the central Illinois terminals,
although overcast conditions will persist through the entire 06z
TAF period. Northwesterly winds will gust to between 15 and 20kt
tonight through Wednesday afternoon before subsiding to less than
10kt by Wednesday evening.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY from 6 AM to 6 PM CST Wednesday FOR
ILZ071>073.

&&

$$

UPDATE...Barnes
SHORT TERM...Onton
LONG TERM...Bak
AVIATION...Barnes






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