Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 152340
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
640 PM CDT Tue Aug 15 2017

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Wednesday)
Issued at 310 PM CDT Tue Aug 15 2017

Sfc map this afternoon features a warm front across southern NE with
low pressure across southeast CO. Meanwhile, water vapor sat loop
shows one wave across northern OK moving into southern KS with the
main upper trough still back near the Four Corners. MLCAPE of
2000=2500 j/kg was common while effective shear was around 20-30kts
with better shear across SE KS southward.

For tonight...expect 2 areas of convection to impact some part of
the area with the first associated with the upper wave across OK.
Scattered t-storms will develop as the wave moves north. 30-40kt LLJ
will also develop along the Flint Hills into the area so expect an
increase in coverage through 6z. Next it still appears that a
complex of storms will develop across southwest/southern NE this
evening and those storms will gradually build SSE with time and
could move into central KS toward or after 6z.  Bottom line is that
storm chcs will increase for all areas overnight with best chcs
after 6z toward 12z Weds. Locally heavy rains will occur with any
storms given slow movement and warm cloud depth/high PWATS
approaching 2" and increasing LLJ. Only feature lacking is a
925/850mb boundary to focus convection on.

Weds...main upper trough will pass during the afternoon/evening but
coverage and intensity of any t-storm re-development near the sfc
low/cold front will be dependent on evolution of morning storms so
uncertain for severe risk tomorrow.  Will keep high precip chcs
going given expected morning convection at this point with highs 80
to 85.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 310 PM CDT Tue Aug 15 2017

The main trough axis lifts out over south central and eastern NE
Wednesday night. There still remains the question of the exact
position of the sfc front with the GFS being the outlier further
north towards north central KS. Consensus guidance has the front
bisecting the CWA, progressing southeast of the area by 12Z
Thursday. Depending on if convection occurs earlier in the
afternoon, if skies clear for a time in the afternoon, could see a
few strong to severe storms aft 00Z, mainly for hail and gusty
winds. Widespread threat for heavy rainfall remains, especially if
we get a decent amount of rainfall on Wednesday. Total rainfall
amounts by Thursday morning from both events could range from 1 to 3
inches or more locally.

Northerly winds return the drier dewpoints in the 60s from Thursday
through the weekend. Broad westerlies with embedded weak upper
troughs bring periodic chances for thunderstorms during the Thursday
evening - Friday time and Sunday night time periods. Temps are
generally near normal for this time of year with highs in the upper
80s and lows in the 60s.

.Solar Eclipse for Monday, August 21st...

Available guidance this far out remains uncertain on precipitation
chances and subsequent cloud cover. There is an apparent signal with
all guidance for an embedded upper wave traversing the central
plains region in the Sunday evening to Monday morning time frame.
There is at least a slight chance for precip mentioned in the
forecast Monday morning, with a gradual drying trend towards the
afternoon. Cloud cover is even trickier this far out with the
residual low and mid level moisture potentially lingering in the
area after the wave passes. Model fluctuations and changes to the
forecast will continue throughout the week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 636 PM CDT Tue Aug 15 2017

There may be a slight chance for showers and thunderstorms across
the terminals later this evening but shower and thunderstorms
chances will increase through the early morning hours. We may see
a break during the late morning and early afternoon hours of
Wednesday, but storms may redevelop along a surface cold front
during the mid and late afternoon hours of Wednesday. There could
be a period of MVFR ceilings at the terminals from 12Z through 17Z
but the lower ceilings should rise above 3,000 feet by Wednesday
afternoon.

&&

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

$$

SHORT TERM...Omitt
LONG TERM...Prieto
AVIATION...Gargan



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