Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 232330
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
630 PM CDT Thu Mar 23 2017

.UPDATE...
Issued at 630 PM CDT Thu Mar 23 2017

I`m inclined to keep the wind advisory going through the night
even though current obs show winds below advisory criteria. Models
continue to show a strong pressure gradient remaining over the
forecast area as a low level jet strengthens to near 70KT. With
forecast soundings showing a very weak inversion, if one at all,
am concerned that the momentum of those stronger winds could still
transfer lower with some potential for stronger wind gusts
overnight.

Will also address the red flag warning this evening. Relative
humidity values are generally 40 percent or better and should
gradually recover with the loss of day time heating. So while
winds will remain strong through the night, conditions for extreme
fire danger may not be as favorable. Will touch base with the
land management partners for their input as well.

&&

.SHORT TERM...(This evening through Friday)
Issued at 314 PM CDT Thu Mar 23 2017

A Red Flag Warning and a Wind Advisory remain in effect for the
entire outlook area through the evening. Maintain the wind advisory
though the overnight hours.

As of Thursday afternoon a mid-level trough was located across the
lee of the Rockies. A surface low was also developing in eastern
Colorado. In response to the deepening surface low, a tight pressure
gradient has setup across the CWA, resulting in sustained southerly
winds at 25-35 MPH with gusts 40+ MPH. Expect winds to remain gusty
overnight as the gradient continues to tighten along with a strong
LLJ. Forecast soundings suggest a LLJ magnitude of 55-65 knots
overnight. With a weak surface inversion and the strong surface
winds, I expect a fraction of the LLJ to mix to the surface during
the overnight. We then turn our attention to precipitation chances.
The first chance arrives Friday morning. Have trended PoPs down
during the morning hours as the main trough will remain to the west
along with substantial mid-level dry air. The main system will eject
overhead during the mid to late afternoon and evening hours. As it
does, expect scattered to widespread showers and thunderstorms to
develop across the outlook area. A few storms may become strong to
severe as around 500 to 1000 J/KG of surface based cape and 40 to 50
knots of bulk shear are expected ahead of the dryline. With the
shear profile being predominately in the straight line fashion, I
would expect the primary hazards to be hail and wind, although a
tornado cannot be ruled out.

Not only are thunderstorms possible on Friday but fire weather
concerns continue to areas west of the dryline. Most guidance
continues to suggest dew points in the lower 40s although the 12Z
GFS suggests much drier air with dews in the lower 30s. For now, the
forecast is status quo with minimum RH values in the lower 30s
Friday afternoon. With winds gusting to 25-30 MPH, high to very high
fire danger is expected.

.LONG TERM...(Friday night through Thursday)
Issued at 314 PM CDT Thu Mar 23 2017

By the morning hours Saturday, the upper low is centered over
southwest MO with scattered rain showers and thunderstorms wrapping
around the backside. Gusty northerly winds around 20 mph sustained
linger through the afternoon, before the system gradually shifts
east and the pressure gradient wanes. Subsidence diminishes cloud
cover Saturday evening before the next positively tilted upper
trough lifts over the central plains late Sunday afternoon and
evening. The trough axis position remains fairly consistent between
guidance over northeast KS, bringing higher confidence in general,
non-severe thunderstorms. QPF amounts are low (below half of an
inch) despite the highest pops added during this period. In terms of
temps, if cloud cover holds off until the late afternoon period,
highs in the upper 60s to lower 70s are likely.

Models remain pretty consistent in a temporary ridge aloft Monday
through Wednesday as a strong upper trough deepens over the western
conus. This wave slowly ejects over the southern plains late
Wednesday into Thursday bringing the next chance for rain to the
CWA. This far out, the track is the main uncertainty while both the
GFS and ECMWF are similar on timing. Overall trend of the southerly
track would place northeast Kansas north of the low and therefore
more likely to see rainfall as opposed to stronger storms. Lowered
likely pops given to modest chance pops in the extended as a result.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday)
Issued at 630 PM CDT Thu Mar 23 2017

First concern is potential for LLWS. With forecast soundings
showing only a very weak inversion, the expectation is for strong
wind gusts to continue to mix to the surface through the night.
Additionally winds are expected to remain unidirectional. So with
the forecast keeping surface winds gusting to around 27KT, feel
chances for LLWS are to small to include in the forecast. This
would change in the unlikely event the boundary layer were to
decouple.

VFR conditions should prevail through the night. There are some
indications of another surge of low level moisture moving north by
Friday morning hinting at some MVFR CIGS. At this point think low
level mixing will favor CIGS remaining above 3KFT.

There is some potential for TS Friday afternoon. There are
differences in model placement of TS development, but most
guidance keeps the higher dewpoints near TOP and FOE through the
afternoon. This suggests a VCTS is warranted. Further west, the
dewpoints and instability may mix east before storms have a
chance to form.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 11 PM CDT this evening for KSZ008>012-
020>024-026-034>040-054>056-058-059.

Wind Advisory until 5 AM CDT Friday for KSZ008>012-020>024-026-
034>040-054>056-058-059.

&&

$$

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



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