Area Forecast Discussion
Issued by NWS Topeka, KS

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000
FXUS63 KTOP 141048
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
548 AM CDT Thu Sep 14 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 301 AM CDT Thu Sep 14 2017

Isolated to scattered showers and thunderstorms moving across the
northern half of the forecast area at this hour, associated with
some isentropic lift over a pretty dry lower level airmass.  Echoes
appear strong enough for at least a brief shower in some locations.
Some guidance keeps this mid level front moving slowly east with
time through the morning hours, and have extended rain chances
farther east and longer in time, with most of it breaking up around
the noon hour.  Clouds and earlier showers may shave a few degrees
off the warm highs expected out west, with highs in the middle 90s
west and middle 80s east.  Winds of 15-20 mph with higher gusts in
the afternoon will combine with low relative humidities /generally
25-30 percent in our western counties/ to make for higher fire
danger there.  Not yet critical, but worth mentioning as area
grasses continue to dry and cure.

.LONG TERM...(Friday through Wednesday)
Issued at 301 AM CDT Thu Sep 14 2017

Pacific northwest upper trough phases with the southern stream low
by Friday morning with an expansive broad trough across the western
conus. Strong southwesterly flow south of the frontal boundary will
lift mid level moisture into the region by the morning, resulting in
a warm,muggy and breezy afternoon Friday. Increased wind speeds a
few knots over north central Kansas again where the pressure
gradient is stronger, while boosting highs towards the middle 90s.
Isentropic upglide is observed within an embedded vort max Friday
night across far eastern Kansas into Missouri. Kept the slight
chance mention since low level moisture is still limited through
Saturday morning. Main trough axis lifts out into the northern
plains Saturday evening as the frontal boundary drops into north
central Kansas. Highest pops were placed in the evening period for
the cwa given the better dynamics and forcing from the front.
Overall severe parameters are marginal with the best effective shear
in north central KS into Nebraska. Could see a few stronger storms
initially capable of gusty winds, otherwise no organized
severe weather is expected.

Upper shortwave trough quickly builds off the southwestern
coastline, backing mid level winds to the southwest towards the
region, and maintaining periods of mid level lift and moisture
Sunday through next week. The frontal boundary stalls over southern
KS before lifting northward Sunday night into Monday. A few stronger
storms are once again possible with ample elevated instability and 0-
6 km bulk shear in the 30-35 kt range. Rainfall amounts are
generally light and less than an inch through Monday.

Another poignant upper Pac NW trough phases with the southern stream
wave next week, slowing the upper low and maintaining southwesterly
flow aloft through mid week in northeast Kansas. There may be off
and on periods of thunderstorms however uncertainties are high
given the available low level moisture and location of the upper
ridge in the southern conus during this time.

&&

.AVIATION...(For the 12Z TAFS through 12Z Friday morning)
Issued at 536 AM CDT Thu Sep 14 2017

Scattered showers with isolated TSRA will near the terminals
through 15Z this morning per observational and short term model
trends. Kept the VCTS mention since coverage is fairly sparse and
cloud bases are high near 12 kft. Marginal llws also persists
until southerly winds increase in the 14Z to 15Z time frame. VFR
prevails through forecast period with the possibility of
additional LLWS after sunset this evening.

&&


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

$$

SHORT TERM...67
LONG TERM...Prieto
AVIATION...Prieto



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