Area Forecast Discussion
Issued by NWS Topeka, KS
FXUS63 KTOP 212249
AREA FORECAST DISCUSSION
National Weather Service Topeka KS
549 PM CDT THU JUL 21 2016
...Update to aviation forecast discussion...
.SHORT TERM...(This Evening through Friday)
Issued at 252 PM CDT THU JUL 21 2016
Not much change to overall forecast for the remainder of today with
heat indices likely above 100 degrees until about 9 pm this evening.
There is currently a weak frontal zone across northwest KS and
central NE. This front is forecasted to drift eastward tonight, but
it will not reach our forecast area. Some of the models suggest that
isentropic lift will increase tonight generally above 850 mb over
central KS late tonight. Although it appears that there will be a
decent amount of dry air below about 700 mb. Therefore if showers or
storms can from it will take some time to saturate the environment.
Have slight chances north central KS for a few hours around sunrise.
Temperatures and dew points are forecasted to be similar tomorrow
with the exception of far northern KS, which will be closer to the
frontal zone and possible precipitation. Again tomorrow afternoon
the heat indices will range from 105 to 113.
.LONG TERM...(Friday Night through Thursday)
Issued at 252 PM CDT THU JUL 21 2016
Excessive heat is very likely to continue into Saturday with
temperatures at the same level or even slightly hotter than
Friday. The question regarding eventual heat indices lies in how
high afternoon dewpoints can hold and if today is any indication
the evapotranspiration will remain a strong contributor to high
level near surface dewpoints. Have thus maintained similar
dewpoint values to today and recent days even through Saturday and
with the higher temperatures expect heat indices in the 105 to 115
range. Have the smallest chance for thunderstorms in north central
KS Friday night with an elevated storm possible within the LLJ
upslope, but this looks like a low probability.
On Saturday night into Sunday, a short wave trough currently off
the Oregon coast will move across the northern Plains and is
likely to be strong enough to bring a surface cold front into
northern KS. This front, while likely to be weak, may be strong
enough to kick off a few storms Saturday night with a limiting
factor being a weak low level jet. Models are consistent in
hanging this front across northern KS on Sunday with very hot
conditions persisting south of the boundary and slightly less hot
but with potentially higher dewpoints north of the boundary. This
leads to a chance of continued excessive heat across much of or
all of the forecast area. However at this time with the chance for
thunderstorms, have opted not to extend any products into Sunday
but just know that the potential exists to once again have 100-110
heat index readings.
Late Sunday into Monday morning may be the best chance for
thunderstorms in quite a while, although still not clear cut as a
widespread rain maker. The surface front is likely to sag a bit
farther south across the area as the ridge flattens and a short
wave trough with associated jet streak comes a bit farther south
than previous storm tracks. This setup should provide favorable
jet dynamics for modest deep vertical motion in the local area and
may pose a locally heavy rain potential although the LLJ intensity
remains lacking during that period for such an event.
The first part of next week seems likely to have temperatures in
the lower 90s with heat indices pushing 100 each day...and each
day depending upon thunderstorm coverage as multiple weak upper
disturbances will cross from the northern Plains southeast.
Wednesday into Wednesday night presents itself as another slightly
better opportunity for thunderstorms as a stronger short wave
crosses the region. This may be another scenario for which
individual MCS development is difficult to predict well in advance
but the ingredients for longer track MCS`s will be in place across
the region for much of the weak and could lead to an unsettled
period of weather.
.AVIATION...(For the 00Z TAFS through 00Z Friday Evening)
Issued at 548 PM CDT THU JUL 21 2016
VFR prevails with southerly winds falling below 10 kts sustained
Excessive Heat Warning until 7 PM CDT Saturday for KSZ008>012-