FXUS63 KTOP 082340

Area Forecast Discussion
National Weather Service Topeka KS
640 PM CDT Wed Jul 8 2020

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Thursday)
Issued at 251 PM CDT Wed Jul 8 2020

Focus is on evolution of convection across Nebraska and
progression southeast into KS overnight. Water vapor showed main
upper wave across MT with weaker subtle waves across south central
NE and northeast OK. Westerly 500mb flow is finally beginning to
re-establish itself across the region however you have to go up to
MT/WY and the Dakotas to see flow AOA 30kts at 500mb. At the
sfc...cold front was draped from eastern SD through western NE
into northeast CO.

For tonight...expect t-storms to develop in the vicinity of the
front across central NE after 00z and given weak mid lvl flow
storms should congeal into a cluster and form a cold pool rather
quickly. After 00z 850mb LLJ of 30-40kts will nose up toward the
NE/KS state line and should support any ongoing convection diving
southeast into KS. All CAM models suggest a complex sweeping
southeast through the CWA after midnight with damaging winds
being the primary hazard overnight along with 1-2 inches of rain
especially along the western flank of the complex where
some backbuilding/training may take place.

The evolution of the cold pool and resulting placement of the
outflow boundary will determine where the better chcs for any
severe risk develops later tomorrow. At this point it appears that
the better chcs will be across southern KS closer to OK while our
area may see some lingering elevated convection through midday.

.LONG TERM...(Thursday night through Wednesday)
Issued at 251 PM CDT Wed Jul 8 2020

The region will remain in northwest flow aloft however weak
ridging from the sfc to 805mb will attempt to nose into the area
tomorrow night. This would keep any organized LLJ focused
southeast of the area. Upslope flow should allow another cluster
of storms to form across northeast CO/southwest NE however
confidence in how far east this cluster can get without better
850mb flow remains in question. At this point have left in slight
chcs after 6z but this scenario is something that will need to be

The risk for storms will persist through Friday night into
Saturday as the area remains on the periphery of the cap and
overnight clusters of storms attempt to dive south southeast. It
appears that sfc ridging and a sharpening upper trough to our east
may finally put an end to the storm chcs by Saturday night and
Sunday. Thereafter it looks to turn hotter and mainly dry with
very warm mid level temps forecast by mid week which may keep
conds dry despite a frontal boundary forecast to sag south into
the area by mid week.


.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 634 PM CDT Wed Jul 8 2020

A line of strong thunderstorms is expected to impact terminals
tonight, bringing heavy rain, strong gusty winds and limited
visibilities for a few hours. Most likely timeframe for storms at
KMHK looks to be between 06Z and 08Z, and 07Z to 10Z at KTOP/KFOE.
Showers and a few storms may linger into the early morning hours,
especially at eastern terminals. Otherwise, conditions should
clear out and return to VFR by late morning/midday Thursday.




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