Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 271749

1249 PM CDT Wed Aug 27 2014

...Update to aviation forecast discussion...

.SHORT TERM...(Today and Tonight)
Issued at 343 AM CDT WED AUG 27 2014

The mid-level pattern has remained fairly unchanged as a broad ridge
was focused across much of the southern and southeastern U.S. with a
closed-off low spinning over the Great Basin region. Southwesterly
flow aloft remained in place over the region with water vapor
imagery showing several weak embedded shortwaves developing along the lee
side of the trough over western Kansas and into southern Nebraska.
These weak shortwaves were co-located with the low-level jet along
with some modest isentropic lift. As a result, widely scattered
showers and isolated thunderstorms prevailed across much of western
Kansas early this morning. Similar to the last few days, this
activity to the west has resulted in several outflow boundaries
moving into the area. Enough lift was present early this morning for
some additional scattered thunderstorms to develop across portions
of north central Kansas. Another weak shortwave was noted in far
southeast Nebraska, which spawned a small cluster of thunderstorms
near the Kansas/Nebraska border. This scattered thunderstorm
activity should continue through the morning hours and remain
focused predominantly north of I-70 across north central and
northern Kansas.

The mid-level trough centered over the Great Basin area should
progress eastward into the Rockies today and tonight, which should
flatten the ridge axis a bit over the region and ultimately allow
more of these weak shortwaves to skim across northern Kansas. The
presence of these shortwaves along with lingering outflow boundaries
from early morning thunderstorms and a fairly stationary front that
continues to waver across northern Kansas will allow for periodic
shower and thunderstorm chances across northern Kansas with isolated
chances elsewhere through much of the day. However, due to the
uncertainty in the exact location of these boundaries and
shortwaves, only have chance PoPs in the forecast at this time
through this afternoon. For tonight, models suggest another MCS will
develop over Nebraska with additional weak shortwaves skimming
across northern Kansas. The low-level jet is expected to strengthen
across much of the state and should once again support scattered
showers and thunderstorms through the overnight period, especially
across western Kansas. As the low-level jet veers to the southwest
overnight, it should help to push this thunderstorm activity further
eastward into portions of north central Kansas into Thursday
morning. Once again, there will be the potential for isolated
thunderstorm development across the remainder of the forecast area,
depending upon the location of any lingering outflow boundaries.
While the threat for severe weather from this activity today into
tonight is low, cannot rule out some strong wind gusts, small hail,
and locally heavy rainfall (with 1.7"-1.9" PWATs in place).

With these chances for isolated to scattered thunderstorms throughout
the day, model soundings show more mid and high-level clouds
developing compared to yesterday. As a result, this cloud cover
should hinder temperatures some by keeping afternoon highs a few
degrees cooler in the mid/upper 80s north to the low 90s south. This
cloud cover will persist through tonight and provide some isolation
across the region, with lows expected to drop into the low 70s.

.LONG TERM...(Thursday through Tuesday)
Issued at 343 AM CDT WED AUG 27 2014

Thursday the upper trough moves slowly out of the Rockies and
into the Western High Plains. Energy will eject out of the base of
the trough and into the Plains. Convection should be ongoing in
the morning as nocturnal MCS is expected across Nebraska and
western Kansas. Also outflow boundaries will be a focus for
additional development through the day. Diffluent flow aloft along
with deep moisture transport into the Central Plains will lead to
locally heavy rainfall Thursday night and Friday. Frontal boundary
will move slowly eastward through Friday along with the upper
trough into central Kansas on Friday. Increasing deep layer ascent
associated with the upper trough along with the eastward moving
front will bring the best chances of thunderstorms to northeast
Kansas. precipitable water values remain high in the 1.60 to 2.0
inch range across eastern Kansas. The NAM is the fastest of the
models with the eastward progression of the upper trough while the
GFS, ECMWF, GEM and the GFS ensemble mean are slower and in
general agreement. Clouds and precipitation will keep the
temperatures in the 80s for highs. The upper trough axis looks to
exit Kansas Saturday morning. The frontal boundary washes out on
Saturday afternoon with southerly surface flow increasing Saturday
evening. Will keep precipitation chances going through the evening
hours on Saturday. Sunday will be a dry and breezy day as low
pressure trough deepens in the Western High Plains as an upper
level trough moves across the Rockies. Highs Sunday will warm back
up into the upper 80s to lower 90s. The next chance of rain will
come during the nighttime hours Sunday as an upper trough moves
across the Plains and a cold front slides into the area on Monday.
Models show periodic shortwaves moving through the Plains through
Tuesday and will maintain precipitation chances going. &&


.AVIATION...(For the 18Z TAFs through 18Z Thursday Afternoon)
Issued at 1247 PM CDT WED AUG 27 2014

Main area of concern will reside with the timing of late evening
and overnight thunderstorm activity over northeastern KS into Southern
NE. Timing is low confidence at this point, however, with no appreciable
airmass change from yesterday as well as a lingering stationary boundary
and residual outflows in the area, we should see redevelopment of general
thunderstorms over the area that will be mostly widespread in nature.
Outside of this activity we can expect mostly VFR conditions to prevail
with winds generally southeasterly.




SHORT TERM...Hennecke
AVIATION...Drake is the U.S. government's official web portal to all federal, state and local government web resources and services.