Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 182320
AFDTOP

Area Forecast Discussion
National Weather Service Topeka KS
520 PM CST Sun Feb 18 2018

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Monday)
Issued at 258 PM CST Sun Feb 18 2018

The strong southerly winds this afternoon will diminish slightly
after 00Z as the mixed boundary layer decouples slightly. The wind
advisory for the entire CWA will remain in effect through 6 PM.

An upper level trough across the northwestern US will dig south-
southeast into the southwest US. Strong southwesterly mid-level
flow across the central Rockies will cause a lee surface cyclone
to deepen across southeast CO. A strong southwesterly low-level
jet will advect deeper moisture northeast across the CWA. An EML
will overspread the CWA and there may be enough isentropic lift
for scattered showers and perhaps an elevated thunderstorms
developing. The RAP and ARW show the most MUCAPE across the CWA
with 400-800 J/KG while the NAM and GFS show only 100-300 J/KG.
Therefore, I cannot rule out an elevated thunderstorm after
midnight and through the morning hours of Monday. As the low-level
moisture increase through the night there could be some patchy
drizzle. However, we may be mixed deep enough with the stronger
low-level winds that drizzle may not develop.

Monday, Stronger CAA across the central plains will cause a surface
cold front to push southeast across the CWA through the day. The
front may move just southeast of the CWA before becoming stationary
across south central and southeast KS due to a deepening surface low
and surface pressure trough from southeast CO, east-southeast
across north central OK, then northeast across central MO.
Temperatures across north central KS will start out in the 40s and
lower 50s in the early morning hours but fall through the 30s
into the upper 20s by late Afternoon. As the H5 trough across
lifts northeast into the high plains, stronger isentropic lift
will develop north of the front where an area light rain will
develop. The rain across northeast and north central KS may change
over to light freezing rain through the afternoon hours. East
central KS will see highs in the lower to mid 60s during the mid
morning to early afternoon hours with temperatures falling into
the 40s through the late afternoon hours. Temperatures across east
central KS will remain warm enough for only rain through the
afternoon hours. There is still some question on how far southeast
the front will make it during the late afternoon hours. Most of
the shorter range models have the front pushing southeast of the
CWA and most forecast soundings only show only elevated CAPE above
the shallow colder airmass which will advect southeast behind the
front. At this time the surface based convection will occur south
and southeast of the CWA along the front, where there may be a
threat for gusty winds and perhaps large hail with any rotating
storms.

.LONG TERM...(Monday night through Sunday)
Issued at 258 PM CST Sun Feb 18 2018

Tonight and Tuesday, As the H5 trough across the southwestern US
lifts northeast into the central plains there will be stronger WAA
across eastern OK and southeast KS which will cause the front
across southeast KS to lift northwest into the southeast counties
of the CWA. The stronger CAA will remain across the western and
northern counties of the CWA. Periods of light freezing rain will
continue across northeast and most of the western and central
counties of the CWA. Temperatures will remain above freezing
across much of east central KS through the night. The greatest ice
accumulations will occur across the northeast and north central
counties, southwest into the central counties of the CWA where
0.1" to 0.2" of ice may accumulate through the overnight hours
into the morning hours of Tuesday. However, if the boundary pushes
even farther northwest then temperatures may warm closer to or
slightly above freezing and ice accumulation may be less than
forecasted. A winter weather advisory may be needed for areas
northwest of a Nortonville, to St. Marys to Council grove line
Monday night through the morning hours of Tuesday.

As the upper trough lifts out into the central plains the stronger
CAA will push the front and colder air southeast across east
central KS after 12Z. The area of rain across east central KS may
mix with or change over to freezing rain before ending early
Monday afternoon. The 00Z NAM model solution shows a stronger
push of colder air across east central KS during the morning
hours, which may cause a longer duration of freezing rain through
the late morning into the early afternoon hours of Tuesday across
east central KS. We`ll have to keep an eye on temperature trends
and when the steadier rain shifts southeast of the CWA. If the 00Z
NAM solution ends up being more accurate, then there could be up
to 0.1" of ice accumulations across east central KS from 15Z
through 20Z. However, the NAM QPF looks to be a bit too high
given that 850mb winds begin to veer as the H5 trough lifts out
into the central plains.

Highs on Tuesday will occur in the morning hours across east central
with temperatures in the mid 30s to 40s. Temperatures across east
central KS will fall through 30s into the upper 20s during the
late morning and early afternoon hours, as the surface front
pushes southeast across MO. Temperatures across north central and
northeast KS will remain steady in the upper 20s to lower 30s.

Tuesday night through Sunday, A longer wave length trough will
remain across the western US. A shorter-wave length trough will
lift northeast across the plains bringing a chance for light rain
Thursday afternoon which will chance over to snow or freezing
rain, depending on the thermal pattern aloft. A second upper
trough will lift out across the plains Friday into Saturday.
Temperatures will warm into the 40s and 50s, thus the precip will
fall as rain. Though coder air Friday night may change the precip
back over to light snow.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 515 PM CST Sun Feb 18 2018

MVFR ceilings are approaching the taf sites currently and should
arrive in the next hour or two. Towards sunset there may enough
saturation and lift for drizzle as the winds gradually decrease
ahead of an approaching front. An isolated shower may develop near
TOP/FOE prior to the frontal passage. Some guidance is also
suggesting possibly enough instability for thunder showers along
the front at TOP/FOE in the late morning and early afternoon.
Winds shift to the north behind the front and will not be as
gusty. Ceilings will likely drop down to IFR prior to the front
then gradual improvement through the day tomorrow.

&&

.FIRE WEATHER...
Issued at 258 PM CST Sun Feb 18 2018

Strong southerly winds of 25 to 35 MPH with gusts of 35 to 45 MPH
will continue through the remainder of the afternoon hours, and will
only diminish slightly after 00Z. Even though RHs have steadily
risen above 40 percent through the afternoon hours, the
combination of dry fuels and strong southerly winds will cause a
very high fire danger the remainder of this afternoon and into the
evening hours. Any outdoor burning should be postponed.

&&

.TOP WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 6 PM CST this evening for KSZ008>012-020>024-
026-034>040-054>056-058-059.

&&

$$

SHORT TERM...Gargan
LONG TERM...Gargan
AVIATION...Sanders
FIRE WEATHER...Gargan


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