Area Forecast Discussion
Issued by NWS Topeka, KS
FXUS63 KTOP 241134
AREA FORECAST DISCUSSION
National Weather Service Topeka KS
634 AM CDT WED AUG 24 2016
...Update to aviation forecast discussion...
.SHORT TERM...(Today and Tonight)
Issued at 350 AM CDT WED AUG 24 2016
Morning convection continues to push a cool boundary southward at
this hour with rain showers still developing over the cold pool as
the LLJ slowly veers through the night. Think most of this will
diminish and shift east by around sunrise. Larger scale surface
front extends from central Nebraska southwest into southwest Kansas.
Energy progged to lift over and along this front into our area this
afternoon appears to be over the TX panhandle at this hour.
Concerns for today will be amount and location of rainfall
associated with the boundary, and the strength of the storms that
develop. Mid level winds over central Kansas not quite as strong as
over the eastern counties, where the better bulk shear coupled with
around 2000j/kg of cape could make for strong winds and hail from
mid day storms and into the evening hours. Surface frontal boundary
makes slow southern progress later this afternoon and overnight, and
with near 2 inches of PW in the column will need to watch for heavy
rainfall and localized flooding potential. Swath of 2-3 inch
rainfall today runs from near Concordia to north of Topeka, and will
have to monitor that area in particular if the front stalls and
several storms train over one location as they move along the front
to the northeast. Will go ahead and match up with neighbors with a
flash flood watch for the evening/overnight hours for the counties
that had rainfall on Tuesday. Highs up to the north may hold in the
low 80s behind the cold pool and as the front moves south, while
southeast counties may reach near 90 today. Muggy dewpoints in the
70s remain through the day, with overnight lows tonight from the low
60s north to near 70 south.
.LONG TERM...(Thursday through Tuesday)
Issued at 350 AM CDT WED AUG 24 2016
Effective front should be south of the area by midday but some
instability will remain aloft. Winds aloft remain rather strong for
late August with 500mb winds around 40kt to support some shear and a
small concern for mainly elevated, marginally severe storms
producing hail. Southwest flow aloft will continue and may bring
weak waves overhead. Front will likely become more zonally oriented
but PW values around 1.75" will keep some heavy rain concern going.
Front pushes back north and undergoes frontolysis Thursday night
into early Friday, but mid to low level winds will bring increased
isentropic ascent for a continued storm chance through these
periods. Upper wave translating east across mainly the Northern
Plains brings decent precip chances Friday night into Saturday
night. Forcing for ascent becomes more uncertain beyond this time,
though PW values remain well above normal for above normal precip
chances. High temps remain challenging into the weekend with
northeast winds and low cloud potential on top of precip
possibilities. Dropped temps a bit both Thursday and Friday but SREF
and GFS ensemble MOS showing wide spreads both days. Temps should
modify back to near normal by Sunday.
.AVIATION...(For the 12Z TAFS through 12Z Thursday Morning)
Issued at 632 AM CDT WED AUG 24 2016
Main concerns with terminal forecasts are rain chances and timing.
Morning showers should dissipate over next few hours, and LLWS
continues until mixing develops around 14z. Anticipate a break
before next round develops this afternoon, and do think this will
become a prevailing area of showers and thunder and have carried
as such after 0z. Will likely need a period of lower cigs and
visby to be determined in later forecasts.
Flash Flood Watch from this evening through Thursday morning for