Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 082159

Area Forecast Discussion
National Weather Service Topeka KS
359 PM CST Mon Mar 8 2021

Issued at 353 PM CST Mon Mar 8 2021

Plenty to talk about over the forecast period, with a little of
just everything that mid-March can have to offer.

Another day of critical fire weather conditions continues this
afternoon, though not quite as bad as yesterday. With continued
advection, moisture is slightly deeper today, as seen in the 12z TOP
soundings. This has helped keep relative humidity between 20-30%,
about 5% higher than yesterday. Winds are also slightly weaker, but
are still gusting to around 30 mph across the area.

Overnight, a weak shortwave trough will move eastward through the
region. The scarce moisture keeps precipitation unlikely, but clouds
will increase in coverage this afternoon through tomorrow
morning. Winds will remain elevated at 10-15 mph overnight, as the
surface pressure gradient strengthens. The clouds and continued
winds should keep the boundary layer mixed, with morning lows
tomorrow only falling to around 50. Tomorrow should be another
breezy day, as the tightening pressure gradient and clearing skies
allow stronger winds aloft to be easily mixed towards the
surface. The deeper mixing will also allow temperatures to easily
reach the 70s again.

The main longwave trough currently over the West Coast will slowly
move eastward by midweek, with southwest flow aloft increasing ahead
of it. On Wednesday, one shortwave trough will eject across the
northern Plains, pushing a cold front through the forecast area. A
second shortwave will quickly follow. Moisture advection ahead of
the trough will increase dewpoints into the mid to upper 50s, an
EML will move in aloft, and temperatures will soar to near 80
ahead of the front. This will allow for some instability to
develop along the front. Can`t rule out some convection developing
along the front by late afternoon, but warmer temperatures
between 850 and 700 mb may provide just enough of a cap to
suppress convection during the day. However by mid/late evening
and overnight, storms are more likely to develop as the secondary
shortwave moves through, increasing instability behind the front.
With 500-1000 J/kg of CAPE, and 40-60 kts of effective shear,
there could be a few strong to severe storms overnight. Large hail
of around an inch would be the main threat, especially behind the
front where convection will be the most elevated. Some wind
threat could be present as well, particularly if storms can be
more surface based near the front. Given storm motion generally
parallel to the front, and areas of both cyclonic and anticyclonic
curvature in the hodograph, initial storms should split and
quickly grow upscale. With PWATs around the 90th percentile for
this time of year, and the potential for training storms, there
could be some localized areas of heavy rain in excess of an inch
along and just behind the front. Not expecting significant
hydrologic issues given the recent dryness, but will keep an eye
on this over the coming days. The best chance for storms will end
by early Thursday morning as the front moves south of the region.

By late week into the weekend, the main upper trough will slowly
move eastward towards the central and southern Plains. Low chances
of rain will continue Thursday and Friday to the north of the
stalled frontal boundary. Differences in timing exist, but the
better chance for precipitation will arrive Saturday into Sunday as
the trough approaches, and cyclogenesis occurs in the lee of the
Rockies. Still plenty of time to figure out specifics of this
system, which will depend on the exact track and timing. A southern
track of the system could see snow across portions of the area,
while a more northern track could see another chance for
thunderstorms. The most likely outcome, a track more in the middle ,
would likely be more favorable for just a widespread moderate rain,
with temperatures likely turning cooler than average.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1142 AM CST Mon Mar 8 2021

VFR ceilings will continue for most of the period, though scattered
to broken near-MVFR ceilings may spread north after sunrise tomorrow
morning. Otherwise, the main concern will again be the winds. 15-20
kt south to southwest winds, with gusts around 25 kts will continue
this afternoon, and again tomorrow after sunrise. Overnight, winds
will weaken slightly to around 12 kts, with some 45 kt LLWS
developing as the nocturnal LLJ increases.


Issued at 353 PM CST Mon Mar 8 2021

Extreme fire danger continues across area today, despite slightly
improved conditions compared to yesterday. Relative humidity this
afternoon has dropped to 20-30%, with wind gusts up to around 30
mph. Given the very cured fuels, fire still has the potential to
spread quite quickly, as seen in a few fires across the area today.
Still planning on letting the Red Flag Warning expire at 01z, as
RH recovers and winds slightly weaken.

Winds tomorrow will increase some compared to today, but increased
moisture advection will keep minimum RH values at 30-45%. So while
fire danger will remain high, not anticipating a Red Flag Warning at
this time.

By Wednesday, a slow moving front will move east across the area,
with winds switching to the west and eventually northwest behind it.
There is some uncertainty with regard to specifics, but minimum RH
could fall enough behind the front to allow for very high to extreme
fire danger again for portions of north-central Kansas.


Red Flag Warning until 7 PM CST this evening for KSZ008>012-



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