Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 121745

Area Forecast Discussion
National Weather Service Topeka KS
1245 PM CDT Sat Aug 12 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 322 AM CDT Sat Aug 12 2017

High clouds were streaming eastward across the state this morning and
advancing across the cwa at 08Z. Water vapor satellite loop shows a
circulation over southwest New Mexico while a shortwave trough was
moving into Montana. At the surface the high pressure ridge extended
into central Kansas early this morning. Convection across western
Kansas is expected to approach north central Kansas this morning
before decaying as it encounters drier air. CAMS differ with
precipitation moving into north central Kansas this morning with the
HRRR the only one bringing it into central Kansas about mid morning.
Moisture transport vectors suggest best moisture advection will
remain to the west of the forecast area and will maintain a dry
forecast for much of the day. A split flow pattern develops with the
New Mexico wave moving through the southern stream across north
Texas and southern Oklahoma today while the upper trough moves
across the northern Plains. This will keep forcing to the south and
north of the forecast area this afternoon and evening. The surface
high will remain entrenched from Iowa into eastern Kansas through the
evening hours before moving off to the east. Convection that is
expected to develop across Nebraska into western Kansas may move
into north central Kansas tonight after midnight and have maintained
precipitation chances across north central and east central Kansas.
Instability axis is forecast to be across the high Plains into
central Kansas tonight with little to no instability across northeast
Kansas. Will keep a dry forecast going for much of northeast Kansas
tonight per current forecast. Highs today will again be below normal
with highs in the lower 80s. Lows tonight in the lower 60s.

.LONG TERM...(Sunday through Friday)
Issued at 322 AM CDT Sat Aug 12 2017

By Sunday, a broad mid-level trough will be stretched across the
eastern CONUS, with an embedded shortwave trough over the Dakotas.
At the surface, the CWA will be wedged between high pressure to the
northeast and low pressure over Colorado.  As the shortwave trough
over the Dakotas slides southeastward toward the Great Lakes region
Sunday into Monday, models show several weak embedded waves
developing within the mid-level flow and producing scattered chances
for showers and thunderstorms Sunday afternoon and again on Monday.
A weak mid-level ridge will build into the central U.S. behind the
exiting trough, with a brief dry period Monday night before the next
disturbances move into the region.  On Monday, models show a mid-
level trough nosing southward from Canada into the Pacific
Northwest, and this trough will continue to dig southeastward
Tuesday into Wednesday.  This advancing trough will shift the weak
ridge to the east, with models showing a few embedded shortwaves
developing along the southeastern edge of the trough axis.  As this
trough advances eastward toward the central U.S., it will also start
shifting the surface low pressure over Colorado into Kansas, with an
associated warm front lifting northward across the CWA Tuesday
afternoon into Wednesday.  The mid-level trough axis will pivot just
north of the CWA into the Northern Plains, but it will be enough to
push the low pressure further eastward across Kansas with an
associated cold front tracking across the CWA Wednesday afternoon
into Thursday morning.  The combination of these frontal passages
and weak embedded waves within the mid-level flow will support
continued scattered shower and thunderstorm chances Tuesday through
early Thursday.  We will have to monitor these mid-week storms to
see if the frontal passage will provide enough forcing and lift to
support the development of any strong storms with the modest
CAPE/shear in place.  Models show the potential for continued
scattered precipitation chances Thursday into early Friday as
additional embedded waves develop within the broad mid-level trough
stretched across the western and central U.S.

As for temperatures, highs will remain steady in the low/mid 80s
Sunday through Tuesday with highs rising into the mid/upper 80s
ahead of the frontal passage on Wednesday. Do not anticipate cool-
air advection behind this frontal passage, so expect temperatures to
rise a bit toward the seasonal normals with highs in the upper 80s
and low temperatures rising to around 70 degrees.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1221 PM CDT Sat Aug 12 2017

VFR prevails at terminals with sfc high pressure in place. Dry
advection from the east holds off precip to our northwest and
south through forecast period. Light easterly winds prevail below
10 kts.




LONG TERM...Hennecke
AVIATION...Prieto is the U.S. government's official web portal to all federal, state and local government web resources and services.