Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 160455

Area Forecast Discussion
National Weather Service Topeka KS
1155 PM CDT Thu Mar 15 2018

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Friday)
Issued at 309 PM CDT Thu Mar 15 2018

Red Flag Warnings are in effect through early this evening and
again tomorrow (Friday) as addressed in the Fire Weather section

Strong surface cyclogenesis continues over the central High
Plains. The interaction of the broader, strengthening cyclonic
flow within an eastward/southeastward-arching baroclinic zone is
inducing a zone of frontogenesis over the far northern forecast
area -- toward the Nebraska border. This zone serves as the
northern bound for the deepest boundary layer within which gusty
winds and low relative humidity are creating extreme fire danger.

While the boundary layer undergoes slight decoupling tonight and
surface winds correspondingly back, an influx of poorly modified
Gulf moisture will occur -- aided by a nocturnally strengthening
low-level jet within the cyclone`s warm sector. While more
appreciable boundary-layer moistening is presently confined to
central Texas vicinity and points southward, the substantial
poleward low-level mass flux above the surface should foster
elevated moisture transport into the region. This moisture will
eventually be manifest at the surface via shear-driven and then
diurnally enhanced mixing late tonight into Friday within a narrow
corridor arching eastward/southeastward from a surface cyclone
migrating eastward across northern Kansas. Larger-scale downslope
flow within the southern semicircle of the cyclone will encourage
the eastward and eventual northeastward spread of the diurnally-
enhanced deep boundary layer into portions of northeast Kansas
Friday afternoon. Sufficiently strong low/mid-level flow
overlapping with the boundary layer will result in extreme fire
danger across Friday`s Red Flag Warning area.

As the periphery of steep low-level lapse rates intersects the
corridor of modest return moisture, sufficient buoyancy will exist
for some potential for diurnal storm development, especially as
height falls preceding a migratory mid/upper-level low overspread
the buoyancy. Despite marginal buoyancy, sufficient deep shear
and low-level hodograph curvature may conditional foster
sustained, organized, rotating convection. However, present
indications are that storm motions may quickly displace convection
toward the cool/stable side of the return-moisture corridor upon
development, restricting the residence time of its ingestion of
surface-based effective inflow. As a result, the risk for strong
to perhaps severe storms is non-zero, but is highly conditional,
and will be confined to areas generally north of the Red Flag
Warning area.

.LONG TERM...(Friday night through Thursday)
Issued at 309 PM CDT Thu Mar 15 2018

An influx of continental air behind the departing cyclone will
result in little in the way of impactful weather through much of
the weekend. A surface cyclone accompanying a midlevel speed
maximum is forecast to move across parts of Oklahoma and Kansas
late Sunday into Monday. Surface-based buoyancy associated with
Gulf moisture return should remain south of the region, though
showers and perhaps a few thunderstorms may affect the area.
Strong storms are not expected. An influx of cooler air behind
the latter cyclone may support some potential for light snow
Monday night into Tuesday as another disturbance crosses the
region, before drier conditions become established later in the


.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1147 PM CDT Thu Mar 15 2018

Southeast winds at the 1500 to 2000 feet range will continue to
increase to 40 to 45 KTS and if surface winds remain from the
east-southeast at 10 to 13 KTS then there may be 30 KTS of low-
level shear in the lowest 2000 feet. The southerly winds will
bring a stratus deck with MVFR ceilings and scattered rain
showers to the terminals later Tonight and through the morning
hours. The showers will end by late Friday morning. Scattered
showers and potential an isolated thunderstorm will redevelop
Friday afternoon and may affect the KFOE and KTOP terminals.
Surface winds will also increase to 13 to 16 KTS with gusts of
20-25 KTS through the day Friday but will switch to the west by
late Friday afternoon and early evening.


Issued at 803 PM CDT Thu Mar 15 2018

The Red Flag warning for this afternoon and early evening was
allowed to expire at 8 PM as relative humidities will continue to
rise as temperatures cool and residual moisture advects northward.
Occasional gusty winds and dry fuels Tonight will cause a very
high fire danger.

A Red Flag Warning will be in effect from 10 AM to 8 PM Friday
along and south of a line from Minneapolis to Ottawa. Strong
winds will combine with relative humidity around 20-25 percent
across the Red Flag Warning areas. These factors combined with the
presence of very dry fuels warrant the Red Flag Warnings. Of
note, a wind shift from the south to west and then northwest is
expected from Friday afternoon to Friday evening.


Red Flag Warning from 10 AM to 8 PM CDT Friday for KSZ034>038-



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