Area Forecast Discussion
Issued by NWS Topeka, KS

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000
FXUS63 KTOP 011747
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
1147 AM CST Wed Mar 1 2017

...Update to aviation forecast discussion...

.SHORT TERM...(Today and tonight)
Issued at 325 AM CST Wed Mar 1 2017

A few weak returns remain aloft from nearby radars but area is
becoming increasingly dominated by mid/upper dry air moving in
behind the upper wave. Cold air advection behind the cold front was
diminishing but an area of stratus was pushing southeast out of
eastern and northern Nebraska.

Dry air aloft, nearly unidirectional flow into the mid levels, and
subsidence behind the wave leads to increasing northwest winds
today. Stratus may clip northeastern areas early, but dry air will
build on down with time as surface high builds in from the west-
northwest. Highs in the low to mid 50s still on track for today.
Went a bit cooler for lows tonight with light winds and boundary
layer decoupling as next surface low nears in continued northwest
flow.

.LONG TERM...(Thursday through Tuesday)
Issued at 325 AM CST Wed Mar 1 2017

A general warming trend is expected at least through Sunday as upper
level heights steadily increase. Do expect one cold frontal passage
on Thursday which will be felt in the form of a wind shift but the
cool air will be a glancing blow and still expect highs in the 50s.
Thursday, Friday, and Saturday all look to be characterized by dry
relative humidity with Min values less than 30 percent each day and
possibly flirting with the 20 percent level especially on Thursday.
Winds on Thursday will probably be too low to meet fire product
criteria but still anticipate very high fire danger. Expect windier
conditions for Friday and Saturday so will want to give special
attention to RH forecasts as there is at least moderate potential
that conditions will be drier/warmer than currently forecast and
could result in the need for fire products. Again, while meeting
specific 20% RH and 25 mph gust criteria in tandem is uncertain, see
a high probability for at least very high fire danger each day.

A strong upper level trough is forecast by all model guidance to
move from the Pacific NW across the northern Plains Sunday into
Monday, with an attendant 120+ kt jet streak over the central
Plains. Strong warm advection and strong moisture advection will
focus into the local area by Sunday with some indication of surface
dewpoints into the upper 50s or even low 60s in advance of this
storm. Will also see temperatures warm into the 70s during the
weekend. There are substantial model differences in the timing of
this northern Plains energy that preclude having much confidence in
the specifics of the forecast. Will say at this time that IF a
slower eastward progression progression should occur similar to that
of the 00Z GFS, a severe weather threat is not out of the question
for Monday. Other faster model guidance at least suggests severe
potential with this storm system but displace it farther to the east
to the faster system speed. So again, worth watching the progression
of the forecast for this period. Model differences compound by mid
week with the GFS solution being cool with northwesterly flow aloft
while the ECMWF would suggest a warm and convectively active period,
and ensemble members show significant variance as well.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1147 AM CST Wed Mar 1 2017

VFR conditions are expected through the period. Gusty northwest
wind of 15 to 20 kts with gusts to near 29 kts will be possible
through 00Z Thur then decrease to less than 10 kts after 01Z.
Winds increase from the west after 16Z into the 10 to 13 kt range.

&&

.FIRE WEATHER...
Issued at 1147 AM CST Wed Mar 1 2017

Deep mixing this afternoon will allow minimum relative humidity
to drop to 20 percent or less across much of north central and
into east central Kansas. These area will have extreme fire danger
this afternoon. With winds of 15 to 20 mph and gusts to 30 mph or
higher expected this afternoon have issued a red flag warning
until 6 PM for these areas.

The remainder of the area should see RFD values into the Very
High Category this afternoon.

Current forecast for Thursday suggests that RH will be rather low,
most likely in the 17-25 percent range across the whole forecast
area. However, wind speeds seem likely to be a bit lighter from the
northwest than on Wednesday, probably topping out with gusts up to
but less than 20 mph. Deep mixing is expected so there is a bit of
uncertainty in the max gust speeds. Also expect slightly windier
conditions in far northeast KS where RH is currently forecast to be
a bit higher and closer to the 25 percent range.

Friday and Saturday will be windier from the south with gusts
approaching 30 mph Friday and 35 mph Saturday. RH is currently
forecast to be in the 20-30 percent range, but do see some signs
that lower RH will be possible both days, and while current model
guidance does not go aggressively low, conceptual model in scenarios
with strong boundary layer mixing and dry air above the boundary
layer suggests potential to be in the 15-20 percent range so will
closely monitor these periods as we get closer in time.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 6 PM CST this evening for KSZ008-020-021-
034>037-054.

&&

$$

SHORT TERM...65
LONG TERM...Barjenbruch
AVIATION...53
FIRE WEATHER...53/65/Barjenbruch


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