Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 271754
AFDTOP

AREA FORECAST DISCUSSION
National Weather Service Topeka KS
1154 AM CST Sun Nov 27 2016

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 259 AM CST Sun Nov 27 2016

Early this morning an intense upper trough was located across
western AZ and will lift northeast into the central plains Today and
this evening. A secondary upper trough will follow behind the main
upper trough and move into far west TX by 12Z MON.

A 40 to 50 KTS LLJ early this morning extended from west central TX,
northeast across KS and was transporting deeper gulf moisture
northward. Forecast soundings show a deep dry air layer above 800mb,
thus at this time the increasing isentropic lift on the 295 theta
level should not cause any thunderstorms due to the dry layer of air
and EML. I cannot rule out some light showers or drizzle developing
through the morning hours. By afternoon the stronger ascent ahead of
the upper trough will cool and moisten the mid levels of the
atmosphere. The elevated showers and thunderstorms should remain
elevated through most of the afternoon hours across the CWA. Several
of the higher resolution models show a break in the showers and
scattered thunderstorms during the mid and late afternoon hours.

Farther northwest of the CWA across northwest and west central KS a
dry line will push east from western KS and a surface cold front
will begin to push southeast into northwest KS. The NAM and WRF
solutions show the better instability developing in the afternoon
hours across west central KS. The most robust MLCAPE values of
around 400 j/kg will be centered from the Hill City, KS area
northward to the NE border. The vertical windshear will be strong
across west central KS with 0-6KM effective windshear of around 50
KTS. The low-level 0-1KM SRH will be between 200 and 300 j/kg. If
surface based storms can develop along the dryline and front
intersection across west central and northwest KS during the
afternoon hours they may evolve into low-top supercells. However the
instability is rather weak and the vertical windshear may inhibit
any deep moist convective updrafts from developing. Gradually the
instability axis of 200 to 300 J/KG will shift east into the western
counties of the CWA. If there are any isolated storm ongoing they
may move into the western counties during the early evening hours.
Though the tendency after sunset will be for these scattered surface
based storms to become elevated. I suppose with any low top
supercell there may be small hail, a possible severe wind gust and
perhaps a isolated weak tornado if any low top supercell can remain
surface based while entering into the western counties of the CWA
this evening. IMO, I think the storms will become elevated and will
only provide a chance for small hail and gusty winds while moving
into the western counties of the CWA after 00Z. The better chance
for any severe low top supercells will be west of the TOP CWA during
the afternoon hours. The WRF solutions show only a line of surface
based storms developing southwest of Hill City northeast into south
central NE, and these storms remaining northwest of the CWA during
the late afternoon and early evening hours. There may be some
elevated thunderstorms across most of the CWA but unless they become
surface based they will not be severe. Farther east across the CWA
the MLCAPE values drop off to less then 50 J/KG even though the low-
level shear remains strong with 400-500 J/KG of 0-1KM SRH.

As the H5 trough lifts northeast into the central high plains, a
lee surface low will deepen across eastern CO and western KS.
The tightest surface pressure gradient will develop across west
central KS during the early afternoon hours, and shift northeast into
south central NE. Sustained surface winds across north central KS
will increase to 25 to 30 MPH with gust to 40 MPH and continue into
the afternoon hours. The south central counties will see similar
winds developing through the afternoon hours. It looks as if the
cloud cover will hold through the afternoon, so I do not expect
dry adiabatic mixing to be much above 900mb. Therefore I don`t think
a wind advisory will be needed for the CWA Today. It will be windy,
especially southwest of a Emporia to Concordia line where wind
speeds may come close to having 30 MPH sustained winds with some
gusts of 40 to 45 MPH. Northeast  and east central KS will see
southerly surface winds increase through the morning hours to 15 to
25 MPH with gusts of 35 MPH possible through the afternoon hours.
Overall, it will be a windy day across the CWA.

Cloud cover should keep highs in the mid and upper 50s. There may be
some lower 60 degree readings across the southwest counties of the
CWA.

Tonight, if a line of elevated storms develop they will move through
the CWA during the evening hours and should be southeast of the CWA
after midnight. Once again the best chance for a few strong storms
will be in the early evening hours across the western counties of
the CWA. Though the higher resolution models such as the WRF and RAP
keep the stronger surface based storms northwest of the CWA during
the afternoon and early evening hours. Once the lead H5 trough lifts
northeast of the CWA the 850mb winds will veer more to the southwest
and the western edge of deeper gulf moisture will translate east
into MO.

.LONG TERM...(Monday through Saturday)
Issued at 259 AM CST Sun Nov 27 2016

Another quiet weather period for the work week into next weekend
with no precipitation expected. The upper low system continues to
track north on Monday bringing slight WAA in the morning, and
neutral advection towards the afternoon.  This leaves northeast
Kansas with warmer than normal temperatures once again Monday, with
highs in the upper 50s and low 60s.   The system shifts east Tuesday
bringing northwest flow back to the area and moderating temperatures
back to near seasonal values.  Wednesday onward, conditions remain
relatively similar with high temperatures in the mid 40s and lows in
the 20s. The next upper level system moves into the northwest US
Thursday morning; however, this system is progged to move south and
cut off from the mean flow leaving northeast Kansas in relatively
zonal flow beginning Friday.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1146 AM CST Sun Nov 27 2016

Cigs have remained MVFR for TOP and MHK, while FOE has remained
IFR. Expect cigs to remain steady through the afternoon and early
evening hours before scattering to VFR by 03-05Z. Surface winds
will continue to gust 30-45 knots through the afternoon hours.
Expect the strongest winds to occur when showers/storms move
over the terminals as the precip mixes a portion of the 60-70 knot
winds at H850 to the surface. Winds will decrease late this
evening back to near 15 knots. A front will veer winds to the west
by mid-morning on Monday.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Gargan
LONG TERM...Heller
AVIATION...Baerg



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