Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 222121

Area Forecast Discussion
National Weather Service Topeka KS
321 PM CST Wed Feb 22 2017

.SHORT TERM...(This evening through Thursday)
Issued at 320 PM CST Wed Feb 22 2017

As of 20Z Billard Airport in Topeka has set a new record high
temperature for February 22nd with 77 degrees! A weak surface
trough was bisecting the outlook area from northeast to southwest.
Based on surface observations, little temperature gradient exists
behind the boundary. Southwesterly winds have remained gusty
ahead of the trough with areas southeast of the turnpike receiving
gusts near 20 mph. Td depressions near 40 degrees have resulted
in widespread RH values in the mid 20s. The low RH`s coupled with
gusty winds will continue to create very high fire danger through
the afternoon and early evening hours.

The fire danger concerns will subside by Thursday as a surface
low develops in the lee of the Rocky Mountains overnight. As the
low pushes eastward into southwestern KS, a warm front will
progress northward across the CWA. Scattered rain showers are
expected to develop Thursday morning along and ahead of the front
as WAA and isentropic ascent within the 300-305K layer increase.
Forecast soundings in the southwestern part of the CWA suggest dry
low levels, which could limit rain amounts due to evaporation.
Further north and east across the CWA, forecast soundings suggest
a more moist LL environment, thus have the highest PoPs across far
northeast KS. Precipitation chances then shift northward for the
afternoon, mainly along the KS/NE border. Have introduced isolated
thunder chances as forecast soundings along the KS/NE border
suggest sufficient mid-level lapse rates may allow for upwards of
1000 J/KG of MUcape. However, a warm nose at 800MB may preclude
any instability within this period.

.LONG TERM...(Thursday night through Wednesday)
Issued at 320 PM CST Wed Feb 22 2017

A 990 mb low will be lifting northeast through the CWA at the onset
of the period Thursday night. NAM bufr soundings along and north of
the warm front in NE KS depict 1000-1500 J/kg of MUCAPE rooted at
850 mb with 30-40 kts of effective shear values, though the GFS has
a much stronger warm nose and subsequently less instability. Have
maintained chance thunder wording in the forecast through 03Z Friday
until the low has passed through the CWA. Made only small changes to
the forecast for the wrap around precip on the backside of the low,
mainly to include the slight chance of freezing rain for a couple of
hours Friday morning in the far NW CWA, with NAM/GFS RH cross
sections not quite reaching ice nucleation temps. Kept FZRA probs
low given the transient and marginal nature of the supercooled
liquid layer. QPF values remain very low and any ice/snow accrual
amounts will be minimal. Also increased winds by 5-10 kts for
Friday given the tight pressure gradient on the backside of the
deepening low and BL CAA helping to steepen low level lapse rates
and increase stronger wind gust potential.

Surface high pressure slides through Saturday ahead of a broad upper
level wave and will allow temperatures to fall back to near
average with highs in the 30s and 40s on Friday and Saturday. The
next system in line looks to slide primarily south of the CWA,
though the strength of the ridge north of the low varies between
the GFS and EC, and likewise the northern boundary of the precip
shield varies between the models. A deeper H300 trough moves into
the western CONUS at the end of the period on Tuesday and
Wednesday and will bear watching over the upcoming forecast
cycles. Temperatures look to warm back to above average ahead of
this trough as H850 temps return to +10 to +12 C.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1129 AM CST Wed Feb 22 2017

VFR conditions are expected throughout the period. Winds will
continue to veer the northwest throughout the afternoon, although
decreasing below 10 knots this afternoon. The shifting winds will
continue into Thursday as easterly winds increase by 14Z with
sustained 10-15 knots and gusts near 20 knots. Scattered rain
showers are expected to overspread the area Thursday morning. Any
lingering shower is expected to exit the terminals near the end of
the period.




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