Area Forecast Discussion
Issued by NWS Topeka, KS

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581
FXUS63 KTOP 150422
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1122 PM CDT Mon Aug 14 2017

...AVIATION UPDATE...

.SHORT TERM...(This evening through Tuesday)
Issued at 317 PM CDT Mon Aug 14 2017

As of 20z a low amplified trough is centered over the foothills of
the Rockies. A deepening mid level trough was positioned across the
western CONUS. A stalled surface boundary was positioned just north
of the KS/NE border. Surface heating and weak surface convergence
have spawn a few thunderstorms across far northeast KS. Water vapor
doesn`t reveal any subtle shortwaves, therefore expect this trend of
isolated showers and storms to continue along the boundary through
the afternoon and evening hours. Mesoanalysis suggests ~3000 J/KG of
MLcape. However, effective shear values are <20kts, therefore do not
expect any organized convection.

The stationary boundary will retreat northward overnight, taking
thunderstorm chances northward as well. Any residual cloud cover is
expected to remain along the KS/NE border overnight. With a moist BL
in place and winds ~5kts tomorrow morning, expect patchy fog to
develop across much of the area. As the fog scatters out after
sunrise tomorrow morning, a low level stratus deck is possible,
especially south of Interstate 70. By Tuesday afternoon, mostly
sunny skies will return area wide. Steep low level lapse rates will
contribute to another afternoon of fair weather cumulus clouds. High
temperatures will top out in the mid to upper 80s in the eastern
counties, to near 90 in the western counties. Guidance continues to
suggest a weak shortwave rounding the trough in the west and
traversing southern KS during the late morning and early afternoon
hours Tuesday, which may result in a few showers and storms.
Otherwise, the bulk of precipitation looks to remain along the cold
front late Tuesday night and Wednesday.

.LONG TERM...(Tuesday night through Monday)
Issued at 317 PM CDT Mon Aug 14 2017

A poignant upper trough gradually shifts over the central plains
after 00Z Wednesday as a deepening sfc low increases southerly winds
overnight. Heaviest rainfall axis between cams is consistent from
southern NE through northern portions of the CWA towards Wednesday
morning. Strong moisture transport from the south and southwest,
advects precipitable water values in upwards of 2 inches by
Wednesday morning. The approaching cold front on Wednesday afternoon
is the focus for additional thunderstorms during the afternoon.
Depending on many factors including any clearing in the afternoon
may result in enough instability for a few stronger storms to
develop, especially if the NAM, GFS, and Canadian verify with the
boundary situating over east central KS by late afternoon. Effective
shear values around 30 kts would be enough to support updrafts
capable of hail and damaging winds. Locally heavy rainfall also
becomes a concern at this point with the multiple rounds of
potential rainfall. Precip comes to an end Wednesday night with
rainfall totals ranging from 0.50 to upwards of 2 inches, locally
more.

There are brief periods of dry weather on Thursday-Friday afternoon
and again on Saturday afternoon as temporary ridging passes over the
area. The active westerly flow pattern continues to bring
progressive upper waves through the region Friday night and again
possibly Sunday night. The prevailing southerly winds and warm 850
mb temps hold the forecast highs in the in the middle to upper 80s.
While still a week out, current models are depicting the upper
trough on Sunday night to progress slowly east of the CWA Monday.
Overcast skies will gradually clear in the morning and early
afternoon hours of the Eclipse, with the potential for additional
thunderstorms along a boundary in the region during the afternoon.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday)
Issued at 1122 PM CDT Mon Aug 14 2017

Not much change in forecast thinking. Forecast soundings continue
to show marginal fog potential with the most likely outcome being
some MVFR VSBY around 12Z. As for precip chances, those look to be
increasing towards the end of the forecast period. With the better
potential after 06Z, will not include a mention of TS just yet.

&&

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

$$

SHORT TERM...Baerg
LONG TERM...Prieto
AVIATION...Wolters



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