Area Forecast Discussion
Issued by NWS Topeka, KS
FXUS63 KTOP 242348
AREA FORECAST DISCUSSION
National Weather Service Topeka KS
648 PM CDT TUE MAY 24 2016
...Update to aviation forecast discussion...
.SHORT TERM...(This Evening through Wednesday)
Issued at 324 PM CDT TUE MAY 24 2016
A familiar synoptic pattern is seen in the 19Z water vapor imagery.
With a mean trough still over the west and northern Rockies,
southwesterly flow aloft remains over the central plains. A surface
low was again analyzed over the OK panhandle with a dryline
extending south through west TX. Outflow from morning storms has
muddled up the surface pattern over northeast KS and the better
moisture convergence is appears to be over southwest KS between the
surface low and the outflow boundary over southern KS.
A lot of this forecast is based on expected persistence of the
pattern and previous nights. Think that storms will once again
develop over southwestern KS and congeal into an MCS moving across
eastern KS tonight. The HRRR/ARW/NMM show a bowing MCS developing
this evening and move it across the forecast area by the late
evening. 0-6KM shear remains rather marginal around 30KT so the main
concerns with the storms will be damaging winds, hail and localized
flash flooding. Have likely POPs going tonight, but confidence is
only medium as some of the models still show various tracks to the
MCS. POPs taper down during the morning Wednesday as models move the
storms through earlier in the night. Although if an MCV is slow to
move east, there could be some lingering precip late in the morning.
Lows tonight should be in the lower to mid 60s with rain cooled air
helping to cool temps more so than they would be without precip.
Highs Wednesday are forecast to be in the lower and mid 80s as
models advect warmer air into eastern KS with 850MB temps warming to
around 22C and 700MB temps between 8 and 10C. Because of this,
forecast soundings show an elevated mixed layer capping the boundary
layer through much of the afternoon. So the question becomes whether
there is enough convergence along the dryline to force storms
because large scale forcing again appears to be weak at best. Most
guidance seems to keep the boundary layer capped as they do not
generate much QPF in the afternoon, so have kept some small POPs in
the forecast for Wednesday afternoon on the small chance a storm
.LONG TERM...(Wednesday Night through Tuesday)
Issued at 324 PM CDT TUE MAY 24 2016
Wednesday Night Friday...
Convective chances by early evening will be dependent on what
mesoscale boundaries will be present from any convection earlier in
the day. Otherwise the dryline and front will be located west of the
forecast area. There is not much in the way of upper support,
however the models suggest that there may be a weak wave moving out
of western Kansas into Nebraska Wednesday night. Instability,
moisture and shear will be sufficient for a few severe storms with
hail and wind the main hazards and a low probability for tornadoes.
Thursday may start out dry as models move off an MCS well east by
12Z Thursday. The models have slowed the ejection of the main energy
ejecting out of the western trough, but do eject a lead shortwave
out into the Plains Thursday afternoon and evening. Forecast
soundings show Steepening lapse rates and increasing shear around 30
to 35 kts toward 00Z Friday along with mlcape around 2500 J/kg.
Expect thunderstorms to develop along the front and dryline then
move northeast and east across the CWA during the evening and
overnight hours. Have maintained higher precipitation chances for
Thursday night and Friday as the upper level trough advances out
into the Plains. Forcing will also be aided by left exit region of
the upper jet across central and north central Kansas on Friday. Any
ongoing precipitation will likely leave mesoscale boundaries across
parts of the area by Friday afternoon.
Friday Night through Tuesday...
The active spring pattern will continue through the extended period.
Friday night an upper level trough across the four-corners region
will eject northeastward into the central plains. A strong vort-max
will will eject across the forecast area Friday evening into
Saturday morning, bringing likely chances for thunderstorms across
the entire area. Strong to severe thunderstorms will also be
possible as sufficient CAPE and shear will be in place. The
remainder of the period will consist of southwest flow aloft and
embedded weak upper-level waves. With the plentiful boundary layer
moisture that will be in place, have at least slight chance PoPs
through the remainder of the period.
.AVIATION...(For the 00Z TAFS through 00Z Wednesday Evening)
Issued at 648 PM CDT TUE MAY 24 2016
Only minor changes to going forecast with timing and impacts of
convection the main challenge. Thunderstorms in SW Kansas a bit
slower than earlier anticipated and HRRR has also slow
progression. Added some gusty winds and IFR visbys in window of
greatest potential. Still some concern for MVFR cigs to around 18Z
Wednesday but not sold on inclusion yet.