064
FXUS63 KGLD 181941
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
141 PM MDT Sat May 18 2024

.KEY MESSAGES...

- Active period begins this evening with showers and storms
  overnight; marginally severe hail is possible along with
  torrential rainfall.

- The relative better potential for severe weather is Sunday and
  Monday. Very large hail and damaging winds are the primary
  hazards Sunday.

- Cooler with frost concerns mid week.

- Active weather may return next weekend (Memorial Day Weekend)

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 226 AM MDT Sat May 18 2024

Weak cold front and associated wind shift is moving into
northern portions of the CWA currently. Some spotty virga or
sprinkles may be possible post frontal for an hour or two. The
cold front then looks to stall south of the area during the day
time as a surface high then develops across eastern Nebraska.
The surface high will then create a more easterly/upsloping
component to the winds along for some moisture return. A
disturbance then moves off of the Rockies during the mid to late
afternoon time fram allowing for some showers and storms to
move into the area from the Front Range and move to the
northeast. The above mentioned stationary boundary then begins
to creep ever so slowly back to the north overnight Saturday and
early Sunday morning. The lift from the Rockies wave looks to
interact with this boundary and form additional storms roughly
along a Cheyenne Wells to Norton line. Last night the NAM was
the most aggressive with showing a couple thousand joules over
elevated MUCAPE; more guidance is starting to suggest this now
as well which has increased my concern for some instances of
severe hail around quarter size starting around 06Z through
sunrise Sunday. Looking at forecasted 0-6 wind shear it appears
that the strongest shear looks to be around initiation time near
06Z and then waning through sunrise. PWATS increase to around
1.25 inches overnight as well creating the potential for
torrential rainfall. Still continue to think that any flooding
potential will be low as these storms will moving fairly
quickly but will need to keep an eye on back building and
training storms as some guidance does suggest that rainfall may
last through about 8am Sunday.

Sunday, then continues to be the day of interest for the short term.
Severe threat is looking a bit more promising than vs 24 hours ago.
Last night there were some concerns about fog/stratus lingering
across eastern portions of the area which would limit overall
instability. While this does continue to remain a possibility,
especially if morning convection does linger; most guidance has
the temperatures rebounding. I did nudge down high temperatures
across the northeast a few degrees if this scenario does pan
out; but was not as aggressive as I would have been last night
in this situation.

As anticipated last night, the severe threat has shifted more
westward as guidance has gotten on board with the western
placement of the dryline which the NAM was suggesting. Discrete
storms look to initiate along the dryline (roughly Highway 385)
during the afternoon hours. I have fairly high confidence (70%)
that these storms will remain discrete as a cap will be in
place. Any storm that does manage to develop during this time
will have the potential for very large hail, perhaps up to
tennis ball size with MUCAPE around 2500-3000 j/kg, steep lapse
rates and 0-6 shear around 40-45 knots. Once storms finally do
initiate they are anticipated to grow upscale into more of a
cluster posing more of a damaging wind and heavy threat; this
currently favors locales east of Kansas Highway 25. Dependent on
how much rainfall occurs Saturday night into Sunday morning,
there may be more of an increased threat for flooding. Locales
east of Highway 83 may be the relative more at risk as some
portions of Gove County received 1-3 inches of rain earlier in
the week. Storms look to move completely out of the area between
10p-1am CT across the east. Some additional storms may try to
develop behind this cluster but currently think these should
remain sub severe.

Some near critical to locally critical fire weather concerns look to
be present behind the dryline with RH values in the low to mid teens
and gusts up to 25 mph especially from around the 22-00Z time
when mixing should be strongest; mainly favoring Cheyenne county
Colorado. Not planning and fire weather headlines this forecast
package due to the anticipated limited spatial area and more
marginal conditions. Upcoming shifts will need to keep an eye on
this potential however.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 140 PM MDT Sat May 18 2024

The latest from the GFS/ECMWF continues to show potential for
rainfall/storms to impact mainly the northern portion of the CWA
from late Monday on into the end of next week.

With a blocking upper ridge over the eastern portion of the country
through the midweek timeframe, a strong trough will swing east out
of the north central Rockies late Monday, making a slow trek
eastward due to the blocking effects of the eastern ridge. This
system will eventually lift northeast along the western periphery of
the block. This will be followed by a second shortwave taking a
similar track although a bit more easterly as guidance breaks down
the ridge for the latter portion of the week. Another amplified
ridge build into the Plains region for Thursday, shifting east to
end the week. This will be ahead of an elongated trough stretching
through the northern/central Rockies.

At the surface, low pressure sets up across southern Kansas late
Monday into Tuesday, lifting northeast with an associated front. The
position/track of this low will allow for a moist, easterly upslope
flow from the surface to 850mb and eventually going northerly by
Tuesday as the low lifts east. A similar setup will occur late
Tuesday into Wednesday for the second system, although a bit further
south based on both the GFS/ECMWF. High pressure traverses the CWA
Thursday/Thursday night, with southerly flow setting up increased
warmth/moisture ahead of the end-of-week upper system. A surface low
does work off the Front Range in tandem with the upper system.

As a result, the main wx concerns are going to focus on the
potential for showers and storms. QPF/track through midweek puts the
best chances for rain north of the Interstate, especially
along/north of Highway 36. For Fri/Sat, the coverage is ahead of the
low/front that moves off the Front Range, but for areas closest to
the surface low.

The chances for storms will be focus mainly for the Mon-Tue
timeframe with the passage of the aforementioned shortwaves. The end
of week system does differ with timing/placement of storms/QPF, but
these could be problematic.

Decent instability along with increasing PW values from west to east
on Mon-Tue, will afford the potential for strong to severe storms,
especially Monday. SPC currently has a Marginal risk for most
locales east of the Colorado border. The surface low passages to the
south will bring in PW values of an inch plus, especially east of
Highway 83 which is closest to the surface trough/front that extends
into central Kansas. So, besides a hail/wind threat, heavy
rainfall/flooding potential will also be high. Monday looks to be
the main focus, with WPC having a Marginal risk area out for locales
north of highway 36 Mon night-Tue. Please refer to the Hydro section
below for more details.

The passage of the second system Tuesday night into Wednesday will
bring about some cooler/colder air into western locales. Areas in
Colorado could see some frost potential, but will be highly
dependent on the extent of clearing from the exiting system. Right
now, western portions of Kit Carson/Cheyenne counties are most prone.

For temps, with a cold front settling through the region during the
first portion of next week, looking for a downtrend in daytime highs
before rebounding for the latter portion of the week. On Monday, mid
70s north through the mid 80s south are expected. A wide range for
Tuesday with mainly 60s north of the Interstate and 70s south will
give way to lower and mid 70s area-wide for Wednesday. 80s Thursday
drops to the mid 70s through the lower 80s to end off the week.

Lows during this time will mainly range from the mid 40s west
through the lower and mid 50s east. Tuesday night will be the
coldest, with lower to mid 40s east of the Colorado border, with
upper 30s to around 40F for northeast Colorado.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 451 AM MDT Sat May 18 2024

VFR conditions are currently ongoing at each of the terminals
and are forecasted to continue for the majority of the 12Z TAF
period. Some Alto Cumulus clouds are in the vicinity of each
terminal as weak front has passed through the area, but are
forecasted to dissipate throughout the morning. A period of
breezy winds gusting around 25 knots looks to occur at each
terminal around 14Z and ending before 18Z. Winds will then
slowly become more easterly throughout the day as a surface high
develops in Nebraska. This will increase moisture and also
increase the potential for showers and storms for each terminal
throughout the night. Confidence is also increasing in a period
of stratus behind the exiting showers and storms towards the end
of the period so have introduced IFR ceilings at KGLD and MVFR
conditions as rainfall should be ongoing at KMCK. Also wouldn`t
be surprised if IFR or lower conditions occur at KMCK just after
this TAF period, will pass along to the next shift to look for
this potential.

&&

.HYDROLOGY...
Issued at 226 AM MDT Sat May 18 2024

Some potential does exist for torrential rainfall and isolated
flash flooding starting Saturday night/Sunday morning into early
portions of the new work week. The majority of the area,
especially western and southern portions have seen a lack of
rainfall in recent weeks and worsening drought conditions.
Overall main concern for any hydro issues lies to the east of
Highway 83 in Kansas where portions of Gove county for example
received 1-3 inches of rainfall earlier in the week. PWATS will
rapidly increase tonight around 1.25 inches and remain above 1
inch for the duration of the weekend. Overall widespread
flooding potential is relatively low as overall systems should
be fairly quick moving with fast Corfidi Vectors. The overall
main concern for any hydro related issues lies in multiple
rounds of heavy rainfall and any potential training locales.

&&

.GLD WATCHES/WARNINGS/ADVISORIES...
KS...None.
CO...None.
NE...None.

&&

$$

SHORT TERM...Trigg
LONG TERM...JN
AVIATION...BV
HYDROLOGY...Trigg