Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 091749
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1249 PM CDT Wed Aug 9 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 255 AM CDT Wed Aug 9 2017

Early this morning the region remained under the influence of
surface high pressure, with the center of this surface high
shifting further east toward the Ohio River Valley. Northwesterly
flow aloft persisted with water vapor imagery showing a couple of
weak embedded waves within this flow: one over Nebraska and a
second wave over the Texas/Oklahoma panhandles. Regional radar was
showing some scattered showers popping up across portions of
northwest to north central KS early this morning from the weak
isentropic lift present. Cloud bases were around 8000-10,000 ft
with a modest amount of dry air in the low- levels. However,
observations showed that it wasn`t taking long to overcome the
low-level dry air, thus helping to support some very light
showers. These early AM isolated showers should remain west of a
Marysville to Manhattan line and diminish after sunrise as the
isentropic lift weakens. With the increased cloud cover across
north central KS, early morning low temperatures will range from
the upper 50s to mid 60s from east to west across the CWA.

Models show a couple of embedded shortwaves within the
northwesterly flow aloft tracking into north central KS by late
morning/early afternoon and then progressing eastward across the
CWA through tonight. With these approaching waves, cloud cover
will remain in place across north central KS for much of today
with the cloud cover spreading eastward across the CWA through the
morning hours. Increased forcing and lift from the shortwaves
look to shift into north central KS through mid-morning before
spreading eastward across the CWA this afternoon and evening. As a
result, once the early morning isolated showers diminish after
sunrise, short-range models show the next batch of precipitation
moving into north central KS by mid-morning. These scattered
showers and thunderstorms will become more widespread across the
CWA late morning through this afternoon. As this precipitation
progresses southeastward across the area, expect the bulk of
precipitation to be focused generally along and southeast of I-70
tonight through the overnight hours. With 20- 30kts of 0-6km bulk
shear and MUCAPE values likely remaining below 800 J/kg, these
scattered storms are not expected to be severe. With north central
KS remaining under the cloud cover for most of today, have
continued to trend a bit cooler with afternoon high temperatures
likely only reaching into the mid 70s. Further east into eastern
KS, highs will rise into the upper 70s to low 80s. By tonight,
precipitation should diminish near the KS/NE border with ongoing
precipitation across the southern half of the CWA. As a result,
expect low temperatures tonight to range from the low to mid 60s
from north to south across the CWA.

.LONG TERM...(Thursday through Tuesday)
Issued at 255 AM CDT Wed Aug 9 2017

First round of showers and thunder are on their way out early
Thursday morning, only to be replaced by the next shortwave in the
northwesterly flow pattern and associated surface front moving
into our area by Thursday evening. Models still trying to resolve
some kind of MCS out over western Kansas and moving southeastward,
into an area with respectable instability and enough wind shear
for some rotating storms. May stay just south of our area, but
with some guidance still suggesting a slightly more northerly
track, will carry PoPs into early Friday morning. With that said,
incoming cooler high pressure and subsidence behind this wave
should keep things mostly dry for Friday.

Next impulse approaches in the overnight hours early Saturday
morning, a bit slower than previously forecast and brings more
rain chances for the day on Saturday. Sunday is a bit more
uncertain as flow flattens more westerly and speed of the
shortwaves within vary between guidance, with no one standout
feature to jump on. Have some slight chances early then decreasing
west to east. Passage of the main larger scale trof still varies
about a day between EC and GFS, with the EC a bit faster and would
be a drier forecast for Monday, while the GFS would linger
chances into Tuesday. Forecast is generally a blend, with low end
chances each day. Highs remain below normal for August, with highs
around 80 and lows in the 60s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1244 PM CDT Wed Aug 9 2017

VFR conditions are expected for the TAF period. A complex of rain
showers continues to slowly progress eastward across the area.
Expect shower activity to arrive at MHK within the hour. As the
scattered showers continue eastward, expect the activity to become
widely scattered. Therefore, only have VCSH at the Topeka
terminals. Uncertainty arises for overnight rain chances. Current
thinking is a secondary batch of showers and isolated storms will
develop across central NE and push across the terminals during
the early morning hours. Patchy fog is possible at MHK near dawn,
but will defer to future outlooks due to uncertainty in cloud
cover.

&&

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

$$

SHORT TERM...Hennecke
LONG TERM...67
AVIATION...Baerg



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