Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 222331
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
631 PM CDT Sun Oct 22 2017

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Monday)
Issued at 332 PM CDT Sun Oct 22 2017

No substantial impactful weather concerns are expected for this
period, except for fire-weather conditions addressed below.

.LONG TERM...(Monday night through Sunday)
Issued at 332 PM CDT Sun Oct 22 2017

The main headline for the extended period continues to be much
colder temperatures arriving by weeks end.

Monday night into Tuesday -- A broad upper level trough will be
positioned across the upper midwest with a deepening surface cyclone
across the southern Great Lakes region. In response to the
deepening surface low, a notable surface pressure gradient will
setup across the central Plains. Expect sustained winds to remain
near 20 kts with gusts approaching 25-30 kts throughout the day on
Tuesday. Given the gusty northwesterly winds and low relative
humidities in the upper 20s to mid 30s anticipated, elevated fire
danger can be expected Tuesday afternoon.

Middle of the week -- As the aforementioned upper level trough
continues its trek southeastward, the central Plains will reside
in the northwesterly regime for mid and upper level flow. A low
amplitude upper level ridge will traverse the central and northern
Plains, transitioning upper level flow to zonal. A secondary upper
level trough will encroach the area Thursday into Friday. In
conjunction with the upper trough, a surface cold front will
traverse the CWA Thursday night/Friday. The first shot of true
Canadian air will overspread the area for Friday and the upcoming
weekend. Confidence is increasing in a widespread hard freeze
Saturday morning as low temperatures look to bottom out near 30
degrees. A repeat performance is possible Sunday morning with lows
once again in the low 30s. As far as precipitation goes, moisture
associated with the frontal passage Thursday night and Friday
looks limited. The lack of moisture coupled with dry solutions
from the GFS/EC/Canadian have decided to keep the extended period
dry.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 610 PM CDT Sun Oct 22 2017

VFR prevails with main concern being LLWS and strong northwest
winds behind the front above 15 kts sustained with gusts in excess
of 20 kts aft 16Z. Strong sfc inversion develops tonight in
approach of a cold front towards sunrise. Winds above the
inversion layer begin to increase above 20 kts as they veer
towards the northwest in the 09-12Z time frame. While initially
top of llws layer may be closer to 1000 feet, winds in excess of
50 kts from the northwest are expected at 2 kft with light sfc
winds persisting until the inversion mixes out mid morning.

&&


.FIRE WEATHER... Issued at 339 PM CDT Sun Oct 22 2017

Fire-weather concerns Monday afternoon will be the primary impact
for this forecast period. Water vapor loops indicate amplification
of a mid/upper-level trough ongoing over the southern Canadian
Prairies and north-central CONUS, within the exit region of an
extensive polar stream. Dry/continental trajectories will be
reinforced across the region, in association with strong surface
ridging overtaking the western states owing to subsidence beneath
the aforementioned speed maximum -- upstream from the trough. The
influx of deep dry air will occur following the passage of a dry
cold front early in the day on Monday, with strengthening northwest
winds through the day. Vertical mixing will manifest strong
northwesterly flow aloft at the surface, with afternoon surface
winds gusting to 30-35 mph -- strongest across north-central KS. The
influx of deep dry air should allow RH to fall into the 20s. These
factors will support elevated fire-weather conditions --
particularly across north-central KS. However, diurnal RH reductions
will be muted to some extent by the background cold advection, as a
warm-thermal ridge moves south of the area well before peak heating.
Moreover, some antecedent fuel moisture may also mitigate the
overall fire-weather risk to some extent. As such, a Fire Weather
Watch has not been issued at this time, though very high fire danger
is expected.

&&

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

$$

SHORT TERM...Cohen
LONG TERM...Baerg
AVIATION...Prieto
FIRE WEATHER...Cohen



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