Area Forecast Discussion
Issued by NWS Central Illinois

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000
FXUS63 KILX 290438
AFDILX

Area Forecast Discussion
NATIONAL WEATHER SERVICE LINCOLN IL
1138 PM CDT Sat Mar 28 2015

.UPDATE...
ISSUED AT 837 PM CDT SAT MAR 28 2015

01z/8pm surface analysis shows a 1028mb high centered over Ohio
and a 999mb low upstream across North Dakota. As the gradient
between these two features tightens, increasing S/SE winds will
develop across central Illinois tonight. Current winds are only
around 5 mph, but are expected to increase to between 10 and 15mph
after midnight. As a result of the southerly winds, low temperatures
in the upper 20s and lower 30s will be achieved this evening,
followed by steady or slowly rising readings overnight. Latest
Rapid Refresh keeps any precip associated with the approaching low
and its associated frontal boundary west of the area until
mid-morning Sunday. As a result, am expecting dry conditions
through the night. Current forecast has a good handle on things,
so no update is needed at this time.

&&

.SHORT TERM...(Tonight)
ISSUED AT 251 PM CDT SAT MAR 28 2015

High pressure centered over southern Lake Michigan early this
afternoon is resulting in little afternoon cloud cover over our
area. Earlier mid/high clouds associated with the Missouri shortwave
moved out late this morning. Still rather chilly for this time of
year, with temperatures mostly in the mid-upper 30s as of 2 pm.

Focus through the night will be with the shortwave currently pushing
through Montana, which is progged to be approaching western
Wisconsin/northwest Illinois early Sunday morning. Only significant
impact for us before sunrise will be with increasing southerly winds
after midnight, as the pressure gradient begins to tighten. High
clouds will be on the increase as well across the northwest CWA,
while the southeast remains mostly clear through the night. The
increase in winds will slow the temperature descent overnight, with
most areas seeing fairly steady temperatures after midnight.

&&

.LONG TERM...(Sunday through Saturday)
ISSUED AT 251 PM CDT SAT MAR 28 2015

Fast moving shortwave and frontal boundary will affect the area on
Sunday bringing gusty south winds and light rain to most of the
forecast area. Fairly decent lift and impressive 700-500 mb lapse rates
suggest an isolated rumble or two of thunder not out of the question
in the morning. Still thinking by the time the precip gets into our
far northwest counties Sunday morning, surface temperatures should
have risen above freezing so will continue from previous forecast
in not including any mention of freezing precip as the rain spreads
east as the morning wears on. Lowest POPs continue to be over
southeast Illinois in the morning with high chance POPs in the
afternoon and early evening before the rain threat shifts off to
our east by sunset. Forecast soundings continue to suggest some
gusty winds starting up by mid-morning into the late afternoon
hours with gusts around 35 mph at times, especially across the
northern third of the forecast area. Wouldn`t be surprised to see
a few gusts approach 40 mph at Bloomington and Champaign early in
the afternoon.

The upper forcing is forecast to shift away from the area Sunday
evening with high pressure settling in from the west on Monday into
early Tuesday before another shortwave approaches the area Monday
night into Tuesday. Models continue to indicate the better lift and
moisture with this system will remain to our north so will continue
to keep rain chances out of our area into Tuesday. As the shortwave
shifts away from the Midwest on Tuesday, the front will settle
southeast into the Ohio River valley by Tuesday evening as surface high
pressure edges southeast across the Great Lakes. Models do indicate a
weak upper wave over southeast KS into northwest Arkansas late
Tuesday with some showers associated with that feature, expected to
stay south of our forecast area Tuesday night into Wednesday. The
latest ECMWF does indicate a jog to the northeast from the weak
shortwave into the Ohio Valley late Wednesday, which may be in
response to the stronger northern stream shortwave over the Dakotas
which may be drawing the feature northward. At this time will
continue to keep most of our area dry through Wednesday as models
suggest a slower transition of the stronger northern stream wave to
the east mid-week and the associated precip chances with it.

After Wednesday, we see some significant differences with respect to
the upper trof to our west and how quickly the storm system
associated with it gets kicked out and into the Midwest towards the
end of the work week. Model consensus indicates after our shower and
thunderstorm chances on Thursday associated with a cold front that
temporarily shifts southeast Thursday evening, a much stronger wave
moves up the boundary into our area on Friday bringing another round
of showers and storms to the region. The 00z ECMWF indicated a much
stronger upper wave which actually brought the surface low up
sharply to the west of our area suggesting the potential for heavy
rain and widespread severe weather on Friday, while the GFS was
flatter with the surface low track with more rain and isolated
storms on Friday as the low tracked mainly to our south. The latest
ECMWF has trended towards the last two runs of the GFS, but still
brings the low a bit further north on Friday, resulting in the
potential for heavy rainfall, especially across our north. Looks
like a rather active pattern to end the month of March with over
the Midwest.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
ISSUED AT 1138 PM CDT SAT MAR 28 2015

VFR conditions will prevail through the entire 06z TAF period
despite passage of a frontal boundary Sunday evening. Clear skies
initially will give way to increasing high clouds toward dawn. As
the front approaches, a band of mid-level clouds and scattered
light showers will develop across the area Sunday morning.
NAM/Rapid Refresh timing still indicates showers arriving at KPIA
by 14z, then further east to KCMI by around 16z. Front will have
very little moisture to work with and strongest upper dynamics are
expected to stay well to the north across the Upper Midwest, so am
not expecting widespread rainfall. Will therefore maintain just
VCSH at the terminals into the afternoon. Light S/SE winds tonight
will increase markedly, with forecast soundings suggesting gusts
reaching the 25 to 30kt range by Sunday morning. Winds will
gradually veer to S/SW, then will decrease and become NW between
02z and 05z as the front passes.

&&

.ILX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

UPDATE...Barnes
SHORT TERM...Geelhart
LONG TERM...Smith
AVIATION...Barnes






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