Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 271749

Area Forecast Discussion
National Weather Service Lincoln IL
1249 PM CDT Tue Jun 27 2017

Issued at 1041 AM CDT Tue Jun 27 2017

Much cooler weather still expected today across the CWA as high
pressure continues to move southeast. Current forecast for
all parameters looks fine for remainder of the afternoon so no
update required at this time.


.SHORT TERM...(Today and tonight)
ISSUED AT 336 AM CDT Tue Jun 27 2017

Surface map of the country dominated by high pressure from the
Plains to the Atlantic coast. Aloft...a sin wave pattern has
amplified quite a bit over the last few days, with Central IL
firmly under northwesterly flow at h5. As the ridge shifts
eastward into the Midwest, mild weather will continue for today,
albeit with a warming trend. Mostly sunny today and drier as
temperatures warm into the 70s. High pressure moving into Central
IL will put the region under the axis of the ridge...with lighter
winds in absence of a significant pressure gradient. As the ridge
slides slowly eastward...winds will gain a southerly component to
them... but todays warm up will be mainly driven by sunshine
early...then a slow transition to more southwesterly flow. Tonight
will remain dry for Central IL as a wave encroaches on the region
to the north. Temps tonight dropping into the 50s
again...although west and northwest may be limited by clouds
moving into the region and limiting radiational component to the
diurnal drop.

.LONG TERM...(Wednesday through Monday)
ISSUED AT 336 AM CDT Tue Jun 27 2017

The northwesterly flow over the Midwest at 500mb modifies over the
next couple days...with a more zonal regime settling into the
region and southwesterly flow in the midlevels sets up a strong
warm air advection period. This shift opens the region to the
deep warm air over the desert SW. 850 mb temps warm from 7-8C on 17-20C by Wednesday evening. Temperatures at the
surface climb a good 7 to 9F on Wednesday and to the mid to upper
80s on Thursday. Guidance so far may be undercutting the potential
for Thursday, and to a lesser extent on Friday as temps at 850mb
spike. But cloud development on Thursday as moisture also feeds
into the well as potential precip keeping the boundary
layer RH in place.
As the flow aloft becomes more zonal...a weak frontal boundary
sets up and seems to stall somewhat over the region resulting in a
prolonged period of precip chances...slowly progressing from the
NW on Wednesday...spreading across the state for Thursday and
Friday. Models have a bit of agreement at this point with bringing
the next wave and a potential MCS to interact with the boundary
already in place for the end of the week, Thu night thru Friday.
However, the details are fuzzy at this point, as outflows and
redevelopment will certainly change on a mesoscale. Warm end of
week likely...with stormy chances through the end of the week.
Weekend not necessarily in the clear, but chances drop briefly.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1249 PM CDT Tue Jun 27 2017

VFR conditions will prevail at all TAF sites next 24hrs. Most
sites will remain SKC remainder of the afternoon and this evening.
Around midnight cirrus will begin to advect over the sites, but
only few cirrus. By morning cirrus clouds will begin to increase
and become broken. With high pressure still dominating winds will
remain light and variable until the ridge moves east later
tonight. Then winds become southerly overnight and then increase
in speed with gusts over 20kts starting around 14-15z.




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