Linn, Kansas Weather Forecast Discussion

246
FXUS63 KTOP 192236
AFDTOP
Area Forecast Discussion
National Weather Service Topeka KS
536 PM CDT Fri Sep 19 2025
.KEY MESSAGES...
- Some showers and thunderstorms likely tonight into Saturday
  morning with isolated heavy rain possible. A few severe
  thunderstorms are possible into the early evening mainly in
  western locations with small hail and gusty winds.
- Mainly dry Saturday afternoon and evening but several chances
  for more showers and thunderstorms late weekend into much of
  next week.
&&
.UPDATE...
Issued at 536 PM CDT Fri Sep 19 2025
The last couple runs of the RAP as well as the 18Z NAM show a
pretty good signal for elevated showers and storms to become
more widespread overnight as the low level jet noses into
northeast KS within a good warm air advection pattern. This
lends more confidence to the CAM progs of scattered to
widespread coverage overnight. Timing could be a little tricky
as the CAMs haven`t had a good handle on the convection across
northwest KS, but the consensus is for lift to pick up around
06Z. Have nudged POPs a little higher with coverage wording in
the forecast to reflect the better confidence. Severe weather is
a non-zero proposition especially this evening across north
central KS. Models keep some decent shear over the area with
modest elevated instability (CAPE values up to 500 J/kg). But
overall trends in the models show weakening lapse rates and
less shear overnight as the shortwave trough axis passes east.
So with conditions forecast to become less favorable for strong
convection overnight, severe weather is not obvious but
something to keep an eye on.
&&
.DISCUSSION...
Issued at 227 PM CDT Fri Sep 19 2025
Upper low over southeastern South Dakota slowly moving east-
southeast with one wave rotating around it over central Nebraska
sparking showers and thunderstorms ahead of it. The wave continues
east-southeast tonight and should continue to support thunderstorms
southeast into the area. Instability this evening may approach 1000
J/kg with deep layer shear enough to support a few severe
thunderstorms until around sunset in north-central and central
Kansas. A modest low-level jet looks to form tonight though there
are differences in where the best convergence will set up, but
isentropic lift across the entire area suggests at least moderate
chances area-wide. Instability looks modest but precipitable water
values near 1.3 inches and some suggestions of training storms could
lead to some locally heavy rainfall. The wave`s exit late tonight
into Saturday morning should lead to decreasing precipitation with
slightly cooler temperatures. There is some fog potential Saturday
night depending on cloud trends with light winds likely.
There are indications of a weak wave moving through Sunday into
Sunday night for the next chance for showers and storms. LREF
ensembles exhibit a large spread in solutions by Tuesday with
clusters showing ridging, troughing, and nearly zonal flow, though
recent GFS and ECMWF runs support troughing Monday night into
Tuesday where higher NBM PoPs are supported. Somewhat warmer
temperatures are likely Monday with cooler conditions behind the
likely trough Tuesday into the late week.
&&
.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 536 PM CDT Fri Sep 19 2025
Timing SHRA at the terminals will be a challenge with better
chances overnight within the warm air advection pattern. Will
use the CAMs as a first guess and adjust timing as it becomes
more apparent. The RAP and NAM suggest lowering CIGS with the
warm air advection. With the NAM (which is notorious for
over saturating the boundary layer) not quite as aggressive
with the low level RH, and a little hesitant to bring in really
low CIGs. Objective MOS guidance shows some lower CIGs by
Saturday morning, but no IFR stuff. So may have some CIGS
between 2 and 3KFT Saturday morning and into the afternoon.
&&
.TOP WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...Wolters
DISCUSSION...Poage
AVIATION...Wolters

NWS TOP Office Area Forecast Discussion