Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 240254

Area Forecast Discussion
National Weather Service Lincoln IL
854 PM CST Mon Jan 23 2017

Issued at 850 PM CST Mon Jan 23 2017

Cloudy but quiet weather is anticipated across central and
southeast Illinois overnight as a ridge of high pressure builds
into the area. An associated subsidence inversion will keep low
clouds trapped in place overnight. These clouds and minimal
temperature advection beneath the inversion should keep
temperatures fairly steady through the night, and help minimize
the development of fog. Going forecast is in pretty good shape and
only minor tweaks are necessary at this time.


.SHORT TERM...(This evening through Tuesday)
ISSUED AT 240 PM CST Mon Jan 23 2017

Forecast has not changed much in the short term for Central and
Southeastern Illinois. A deep surface low has moved off to the
southeast over the Mid Atlantic coast as a narrow surface ridge
edges into the Mississippi River Valley this afternoon.  The layer
of moisture just off the surface is keeping the Midwest under pretty
extensive cloud cover this afternoon. This evening and into the
morning hours will be dominated by the stratus. Clouds in place
through the night should limit the radiational cooling under the least according to the model soundings. Some areas in the
N...with access to slightly cooler air...have higher sfc RH after
midnight and may end up seeing some patchy fog in the early morning
hours. Time heights show the stratus layer persisting through the
morning...breaking up tomorrow afternoon as the warmer air on the
back side of the surface ridge starts to advect in with southerly
flow.  Temps still above normal both tonight and tomorrow as the
airmass remains rather mild.

.LONG TERM...(Tuesday night through Monday)
ISSUED AT 240 PM CST Mon Jan 23 2017

Our next storm system should be over northeast Kansas by early
Tuesday evening with models indicating a track through eastern
Iowa by Wednesday morning and then central lower Michigan by
evening. The better lift and moisture associated with this shortwave
is forecast to remain well north of our area, as a result, the
highest POPs will continue to be north of I-74. As the storm system
shifts off into central lower Michigan by Wednesday evening, colder
air will start to filter southeast into our area with scattered rain
and snow showers possible in the increasing cyclonic flow/low level
cold air regime. Forecast soundings suggest boundary layer
temperatures by Wednesday night/early Thursday morning should
become cold enough to support mainly light snow showers, with
little if any accumulation expected.

Most of the medium range models indicate a series of shortwaves
embedded in a northwesterly flow late in the week and into the
weekend will help to deepen in the trof at 500 mb over eastern
Canada, resulting in a more typical temperature regime for late
January. One such wave will progress southeast into the Midwest
later Saturday with only slight chances for some scattered
flurries. The northwest flow pattern is expected to hold into
early next week, as a result, temperatures should remain fairly
close to normal with little in the way of significant rain or
snow seen as we head into the first few days of February.


.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 529 PM CST Mon Jan 23 2017

Surface high pressure ridge will slide across the region tonight,
bringing light winds. Low level moisture trapped under the
subsidence inversion will keep MVFR ceilings in place. As winds
diminish under 4 kts late tonight 2-3SM fog is expected to
develop, along with IFR ceilings. Some guidance suggests northern
sites KBMI/KPIA could see further visibility reductions for a few
hours around 12Z. Fog should gradually dissipate after sunrise and
ceilings are expected to rise to VFR levels by midday. As low
pressure begins to shift east from the central Plains during the
afternoon, pressure gradient tightens leading to gusty SE winds.




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