Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 300200
AFDILX

Area Forecast Discussion
National Weather Service Lincoln IL
900 PM CDT FRI APR 29 2016

.UPDATE...
Issued at 900 PM CDT Fri Apr 29 2016

Updates this evening mainly to refine the short term timing of
precipitation spreading northward into central IL overnight as low
level warm advection starts to develop ahead of low pressure
moving ENE out of the TX panhandle. Leading edge of this
precipitation is very light and with no lightning detected so have
kept mention of thunder until a few hours after midnight south of
a Springfield-Effingham line spreading northward to I-74 by around
6 a.m. Initially, expect some light showers reaching Springfield-
Effingham by around midnight and continuing northward overnight.

Current temperatures range from the upper 40s in Galesburg and
Lacon to the lower 60s I-70 southward. Lows overnight should only
fall a few more degrees. Winds northeast 6-12 mph will increase to
10-15 mph and become a bit gustier by morning.

&&

.SHORT TERM...(Tonight)
ISSUED AT 303 PM CDT Fri Apr 29 2016

18z/1pm surface analysis shows stationary frontal boundary extending
from West Virginia southwestward to an area of low pressure over the
Texas panhandle.  As a vigorous upper low noted on the latest water
vapor imagery over northern New Mexico pivots northeastward, the
front will get a push northward tonight.  Rain will eventually
spread into central Illinois ahead of the front: however, the models
remain in poor agreement as to how fast this process will occur. The
NAM continues to be the most aggressive in spreading rain across
much of central Illinois by midnight, while both the GFS and Rapid
Refresh tend to hold it back until later tonight. While the upper
low appears rather progressive, a dry E/NE low-level flow north of
the front will likely impede the initial northward progress of
precip.  As such, prefer the slower GFS/Rapid Refresh consensus in
the short-term.  Have therefore cut back PoPs during the evening to
go with a dry forecast along/north of a Rushville...to Lincoln...to
Paris line.  Showers will then overspread the entire area from the
southwest after midnight, with locations along/north of I-74
remaining dry until close to dawn Saturday.  Forecast soundings show
modest elevated instability developing late, so have included
isolated thunder south of I-74.  Overnight low temperatures will
range from the upper 40s north, to the middle 50s south of I-70.

.LONG TERM...(Saturday through Friday)
ISSUED AT 303 PM CDT Fri Apr 29 2016

Still looks like a rather wet weekend in central and eastern IL as a
potent upper level low and cyclonic surface system works its way
into the Midwest from the southern Plains. Fairly strong
isentropic lift is expected to develop along I-70 tonight, and
work its way northward Saturday morning. Moderate low level
moisture transport will bring seasonally high precipitable water
values northward, resulting in total precipitation in the 1.00 to
1.50" range across most of the forecast area by late Saturday
night. MUCAPES in the 100-200 range indicate the potential for
some embedded, elevated thunderstorms in the precipitation shield
Saturday morning and early afternoon.

The potential for strong/severe storms south of I-70 later
Saturday will be dependent on the amount of partial clearing and
atmospheric recovery/instability that can develop in the wake of
the rain. Could see scattered strong t-storms as far north as a
SPI-DEC-Paris line toward evening and overnight, with scattered
showers elsewhere as the surface low tracks through south central
IL.

Should see quite a few showers and isolated t-storms in the forecast
area Sunday as the upper level low/cold pool moves across central
and eastern IL. The presence of plenty of clouds and periods of rain
will keep temperatures on the cool side Sunday with highs only in
the 55-60 range west of the IL River, and generally in the 60s to
east.

The GFS and European models both indicate that as upper ridging
builds rapidly into the Canadian Rockies, a series of shortwaves
will drop into the Midwest from the north. The models have timing
differences with these, particularly by midweek. The result will be
a slight chance/isolated showers in central IL Monday, with more
uncertainty as to the next chance mid-week and again late in the
week. With a faster, longitudinal flow anticipated, will side
more with the quicker GFS and go with low chance PoPs in eastern
IL Wednesday, and central IL later Friday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 655 PM CDT Fri Apr 29 2016

MVFR ceilings continue to be predominant over the central IL
terminals this evening despite a late afternoon trend toward a
decrease in cloud cover that has since reversed. HRRR model and
other guidance products suggest the BKN-OVC layer around 3 kft
AGL will thin later this evening for a possibility of VFR cigs
developing for a time before lowering again overnight as a warm
front lifts northward toward the area. Predominance of model
guidance suggests IFR ceilings and predominant rain by around 09z
at KSPI and 12z at the I-74 terminals KPIA-KBMI-KPIA and have
continued this timing. Modest elevated instability suggests the
potential for a few embedded thunderstorms, so have included VCTS
after 12z. Winds will be from the northeast at 5 to 10 kts this
evening, then will veer to the southeast and increase to around 15
kts with gusts to around 25 kts Saturday morning.


&&

.ILX Watches/Warnings/Advisories...
NONE.
&&

$$

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



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