Area Forecast Discussion
Issued by NWS Goodland, KS

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379
FXUS63 KGLD 282003
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
203 PM MDT SUN AUG 28 2016

.SHORT TERM...(Today through Tuesday Night)
Issued at 237 AM MDT Sun Aug 28 2016

As of 3 am CDT, 2 am MDT, skies across the Tri-State Region have
quickly become overcast over the past 3 hours due to expansive cloud
cover spreading in from the southwest. Latest WSR-88D radar imagery
indicates the only nearby precipitation can be found in southwest
Kansas. Temperatures are in the upper 50s to upper 60s. One thing to
note is T/Td spreads are much higher than yesterday, on the order of
3 to 8 degrees. At the surface, a weak lee trough is located just
east of the Rockies. Aloft, a weak shortwave is progressing across
southwest Kansas, likely helping to sustain current convective
activity. Another shortwave is moving north over central New Mexico.
This trough is ahead of the main upper level low, seen on water
vapor imagery pivoting across northern Arizona and southern Utah.

For this morning, fog potential is once again something to keep an
eye on. However, guidance has backed off on fog potential, something
I think is for good reason. That reason is expansive cloud cover
moving in from southwest Kansas. This will severely limit
radiational cooling compared to the clear skies that aided dense fog
formation yesterday morning. Due to the low confidence in fog
development, decided to remove fog mention from the forecast for all
locations except southwest Nebraska and extreme northeast Colorado
where dewpoint depressions are only 2-4 degrees at this hour.

Over the next 3 days, a series of upper level disturbances will push
through the region. The first comes this afternoon as a shortwave
trough slides in from New Mexico. Then, a weakening upper level low
spreads over the High Plains for Monday and Tuesday. These
disturbances should keep precipitation chances going from the early
afternoon hours to well after midnight each night. It is somewhat
difficult to pinpoint shower/storm development each day due to weak
forcing, the lack of any cap, and uncertainty on boundary/surface
trough locations. With this package, Tuesday seems to hold the best
chance for precipitation as the upper low remnants move directly
overhead.

With regards to severe weather potential, today holds the highest
threat for strong/severe thunderstorms. SBCape between 1500-2500
J/kg should be realized by this afternoon, accompanied by 850-500 mb
Lapse Rates of 7-8 C/km. Storms should be of the pulse-type variety
due to weak wind shear, generally less than 20 kts of 0-6 km bulk
shear. Widespread severe weather should not be anticipated today but
a few large hail or damaging wind gusts are possible. Instability
and lapse rates diminish some Monday and Tuesday. Combined with very
weak shear (10-15 kts), indications are most thunderstorms should
not be severe. A few strong/marginally severe storms can`t be ruled
completely out but seem quite unlikely.

The most impactful weather over the next 3 days should be heavy
rains and potentially flash flooding. Weak winds aloft are highly
indicative of slow storm motions. In addition, precipitable water
readings soar to the 90th percentile or higher, particularly Monday
and Tuesday. If storms become latched to any boundaries, flash
flooding could easily occur given the heavy rain rates likely to
occur and sluggish storm motion.

.LONG TERM...(Monday night through Sunday)
Issued at 202 PM MDT Sun Aug 28 2016

Weak upper low situated over southwestern Colorado Monday night will
continue to slowly weaken and push northeast on Tuesday. A surface
high will build westward at the same time and eventually move into
the central High Plains. Forcing will be strong enough on Tuesday
afternoon/evening to allow thunderstorm development along a very
weak shortwave and theta-e boundary. We could see strong to
marginally severe thunderstorms; however, widespread severe is not
expected. Very heavy rain will be possible with the stronger
thunderstorms and will combine with relatively slow storm motion
along the boundary; all of this will lead to increased flash flood
risk. This system will remain nearly stationary on Wednesday with
increased PoPs across the region, especially in the eastern portions
of the CWA.

H5 low pressure pushes onshore in southwestern British Columbia on
Thursday and will speed up the pattern a bit as we head into the end
of next week. The boundary that was stationary through Thursday will
push off to the east and allow the region to dry out as we head into
Friday. Temperatures will be in the upper 70s to lower 80s through
Thursday with middle to upper 80s on Friday. Lows will fall into the
upper 50s to lower 60s through the extended period.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1150 AM MDT Sun Aug 28 2016

VFR conditions should continue through most of the TAF period.
Low level moisture will increase east of KGLD and towards KMCK
around 12Z and could lead to stratus/fog development. At this time
guidance is not showing a decrease below VFR, but this might need
to be monitored for possible IFR conditions. Other aviation
concern will be shower/thunderstorm potential through the TAF
period. Weak disturbances will continue to lead to development
over parts of the region. Due to the nature of this disorganized
pattern, the timing out the better coverage is difficult outside
of the first 6hr. As a result, I was hesitant to introduce more
than VCTS or PROB30 to TAFs during this update.


&&

.GLD Watches/Warnings/Advisories...
KS...NONE.
CO...NONE.
NE...NONE.
&&

$$

SHORT TERM...RRH
LONG TERM...TL
AVIATION...DR



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