Area Forecast Discussion
Issued by NWS Kansas City/Pleasant Hill, MO

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FXUS63 KEAX 121056

556 AM CDT Fri Sep 12 2014

.SHORT TERM...(Today through Sunday Night)
Issued at 314 AM CDT FRI SEP 12 2014

As of early this morning, an expansive region of showers stretched
from western Iowa into west central Kansas. This activity was
occurring in an area of deep ascent ahead of a strong
positively-tilted trough encompassing much of the northern and
central CONUS. At the surface, the primary cold front has plunged to
the Interstate 20 corridor, with unseasonably cool air continuing to
advect into the region.

The upper trough will progressively move into the western Great
Lakes states by late this evening. Ahead of the trough, areas of
scattered showers will move into portions of the forecast area
around sunrise. The highest probability, coverage, and rainfall
totals is expected over the northwest quarter of Missouri. This area
will be in closest proximity to the strongest ascent, as depicted in
the RH/omega fields within the H5-H7 layer. This lift notably drops
with southward extent, therefore as the upper trough moves through,
lower probability and lower rainfall totals are expected.
Short-term, high-resolution models (HRRR, EAX WRF) also support this
scenario, with the lowest chance for rainfall south of Interstate
70, and best chances along/north of Highway 36. As for temperatures,
a raw day is expected in the north quarter of the forecast area
where cloud cover, showers, and continued cold air advection will
yield highs only in the middle 50s. Elsewhere, highs will still be
unseasonable cool in the upper 50s to lower 60s.

For tonight, clouds will begin to clear by late evening as drier air
advects into the region, while surface high pressure moves east into
the forecast area. Favorable conditions for strong radiational
cooling will exist tonight as skies clear, winds become light/calm,
and cold H85 air (+2C) associated with the upper trough is in place.
Several record low temperatures are in jeopardy tonight as minimum
temperatures fall between 37-42 degrees by early Saturday morning
over the forecast area. Patchy fog may also be possible across
several areas, especially favorable low-lying areas.

The weekend features a flattening upper pattern over the central
Plains, with surface high pressure gradually moving east of the
area. Southerly winds will return by Sunday with temperatures
moderating each day, but still remaining well below normal. By
Sunday evening, an upper trough will approach from the north. Weak
warm air advection coupled with weak upper ascent from the trough
should begin to spawn scattered shallow convection Sunday night.
Models show weak MUCAPE overspreading the area, suggesting that a
few rumbles of thunder will be possible.

.LONG TERM...(Monday through Friday)
Issued at 314 AM CDT FRI SEP 12 2014

Another cold front will move through the area on Monday as a fast
moving upper-level shortwave trough tracks southeast across the
Northern Plains into the Great Lakes area. This will spread showers
and storms across the area. Moisture should be much more limited
than what we saw earlier this week and as a result instability isn`t
as impressive. But deep shear may be in the 30 to 40 kt range along
the front which could lead to some storm organization. But with
surface winds strongly veered along the front leading to weak
convergence, the overall threat of severe weather still looks rather
low at this time.

For the rest of the extended portion of the forecast, temperatures
look to remain below normal, though not nearly like this weekend.
Instead, the cooler high pressure area will settle over the Great
Lakes and Ohio Valley area, keeping the cooler air to our east. This
will also allow for a quicker transition to southerly flow, as that
high shifts further east, allowing us to remain in the 70s from
Wednesday through Friday.


.AVIATION...(For the 12Z TAFS through 12Z Saturday Morning)
Issued at 547 AM CDT FRI SEP 12 2014

MVFR conditions are expected to continue at terminals through the
daylight hours. Cloud deck may lower to around 1,500ft in the next
few hours in advance of and during scattered shower activity. Higher
confidence of showers reaching and persisting at STJ, with lesser
probabilities with southward areal extent. Ceilings should gradually
improve by late afternoon, with mostly clear skies and a return to
VFR a couple hours after sunset.




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