Area Forecast Discussion
Issued by NWS Topeka, KS

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FXUS63 KTOP 240448

Area Forecast Discussion
National Weather Service Topeka KS
1148 PM CDT Fri Mar 23 2018

...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Saturday)
Issued at 341 PM CDT Fri Mar 23 2018

As of 20Z Friday afternoon a cutoff mid/upper low continues to
spin off of the Pacific northwest coast. The central Plains reside
within southwesterly mid-level flow with a fetch of Pacific
moisture streaming across the plains, originating in the Baja
region. WV reveals a shortwave trough traversing the central
Rockies -- which will eject into the central Plains this evening
-- increasing shower and thunderstorm chances. At the surface, a
deepening low was situated near Goodland, KS. A stationary front
arced from the Goodland, KS area into southern NE and east-
southeastward to near Topeka, KS. A dryline extended from near
Goodland, KS to Dodge City, KS into the eastern TX panhandle.
Within the warm sector surface temperatures have reached the low
to middle 70s. Temperatures north of the stationary boundary have
remained in the 50s and 60s. Visible satellite reveals a plume of
deeper moisture associated with a stratus field across eastern OK
and southeastern KS. This deeper moisture will aid in the
potential for rain showers/drizzle and possibly thunderstorms
across much of the area. Otherwise, the main concern through the
short term period is the potential for severe thunderstorms in
northern KS.

As the aforementioned shortwave trough overspreads the central
Plains this afternoon/evening, shower and elevated thunderstorm
activity is expected to develop north of the stationary boundary in
northwest KS/southwest NE. Decent agreement amongst
HRRR/ARW/NMM/NAM with organized thunderstorms paralleling the
boundary and entering portions of northern KS late this evening.
HRRR/NAM forecasting suggest upwards of 600 to 1000 J/KG of MUcape
with updrafts originating between 5000 and 7000 ft. Effective
shear values are progged to be between 35-40 kts, suggesting
rotating updrafts and a large hail threat. As the aforementioned
deeper moisture/stratus advects into the region this evening,
isentropic upglide within the 300 to 310K layer -- ahead of the
surface low -- may contribute to drizzle and rain showers. A stout
EML should limit the probability of thunderstorms south of the
boundary, although HRRR/NAM soundings suggest weak inhibition --
on the order of 50 J/KG -- by 06Z across eastern KS. Therefore,
will maintain a thunder mention during the late evening/overnight

Saturday: The surface trough will push into the MS river valley as
a ridge axis builds into the region. CAA throughout the day will
limit temperatures to the 40s and 50s Saturday afternoon. North to
northwest winds will gust upwards of 25 MPH through the early
afternoon hours.

.LONG TERM...(Saturday night through Friday)
Issued at 341 PM CDT Fri Mar 23 2018

Saturday night through Friday

Broad, positively tilted trough deepens across the western conus
Sunday and Monday. Theta-e advection increases ahead of the wave
Sunday night into Monday allow for the likelihood of precipitation
occurring from all guidance. Temperatures Sunday morning start off
in the lower 30s. Dependent on when precipitation commences, there
may be a light wintry mix of sleet and freezing rain across north
central Kansas. Accumulations are not expected. Variances occur with
the position of the surface low Monday morning and the degree of
moisture surging from the south. The GFS remains the most robust
with readings in the lower 60s, while the ECMWF and SREF guidance is
much lower around 50 degrees. This will have an impact on the amount
of instability realized and the storm mode. Ample effective shear is
present up to 60 kts with enough MUCAPE in the vicinity of a warm
front for a few severe storms being possible. As the inverted sfc
trough lifts northeast over the CWA, main vorticity lobe ejects into
the central plains , surging the cold front southeast Monday evening
and Tuesday. Additional thunderstorms may form along the boundary,
elevated in nature however able to sustain their updrafts with
strong unidirectional wind shear parallel to the boundary.

A cooler airmass ensues for the remainder of the extended as the
elongated upper trough slowly meanders over the southwest CONUS
Wednesday before phasing with an northern stream trough on Thursday.
There is a slight chance for showers along the boundary, otherwise
the region turns dry. Weak southerly flow modulates temperatures
closer to normal with readings back into the 60s by Wednesday.


.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1143 PM CDT Fri Mar 23 2018

The main challenge with this TAF period looks to be ceilings.
Currently, MVFR ceilings are working their way into TOP/FOE with
MHK expected to reach MVFR by 09Z. Models do depict ceilings
reaching IFR shortly after midnight and continuing through the
early morning. IFR ceilings look more likely at TOP/FOE so have
only included SCT IFR ceilings at MHK at the moment. From here,
ceilings will briefly improve through the late morning and
possibly scatter out by the afternoon. Some models do hang on to
MVFR ceiling through the afternoon and this will need to continue
to be monitored. Reduced conditions look to come back near the
very end of the TAF period.




LONG TERM...Prieto
AVIATION...Heller is the U.S. government's official web portal to all federal, state and local government web resources and services.