Area Forecast Discussion
Issued by NWS Goodland, KS

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FXUS63 KGLD 260542
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
1142 PM MDT WED MAY 25 2016

.UPDATE...
Issued at 1105 PM MDT Wed May 25 2016

Regarding convective potential during the late night period into
Thursday morning:

A much more stable post outflow air mass has settled over our
CWA, supporting a lull in convective activity at least over the
next 3 hours. A shortwave (apparent on WV imagery), is currently
moving into south central Colorado. This will be a feature of
interest in the next 3-6hr, as latest NAM/RAP/HRRR show this
shortwave deepening and moving over our CWA by 09Z. The surface
low over SE Colorado deepens in response, and shifts a
warm/stationary front north at least near southern CWA. The
combination of WAA along nose of LLJ, positive frontogenesis, and
increasing large scale support from shortwave all could lead to
shower/thunderstorm redevelopment in our southern CWA (to near the
I-70 corridor).

Return flow north of this front bring much higher Tds back into
our CWA, and support MU CAPE values 1500-3000 J/KG (highest in
the southeast) after 09z. Effective sheer will also remain high
due to LLJ (45-55kt). I am concerned that if this set up is
realized parcels in this potential environment could quickly
become severe with elevated supercells and very large hail. The
questions are just: will CinH weaken enough for this to be
realized, and what nature of coverage.

I have adjusted overnight PoPs to account for this and will amend
HWO as well.

&&

.SHORT TERM...(This evening through Thursday)
Issued at 146 PM MDT Wed May 25 2016

Across the forecast area this afternoon...the remnants of the low
cloud deck which lingered over central portions of the area...now
resides only over far eastern zones and continues to thin out. Temps
in areas where clouds have finally left have rebounded nicely by
several degrees. Most of the CWA now in the 70s with some upper 60s
east. Weak ridging over the area giving the region mainly variable
conditions of 5 mph or less.

Going into tonight and on into Thursday...weak shortwave moving
through the Central Rockies at this time...will move at a northeast
vector across mainly northern zones tonight. Models do hint at
potential for some light rw/trw development..but chances do look
thin. Have put in a slight chance for isolated trw/rw concentrating
in locales over NE Colorado and those along the Nebraska/Kansas
border.

This quick moving system will give way to an approaching warm front
going into Thursday morning. Out ahead of this front...do expect
linger isolated rw/trw...along with areas of fog. The focus of the
fog will be from a few hours before sunrise thru the mid morning
hours before burning off.

It will be along and ahead of this frontal boundary that the focus
for the next round of severe wx will be for the afternoon hours.
Going into the afternoon hrs Thursday...increased instability occurs
with the influx of higher dewpts...daytime highs reaching will into
the mid to upper 70s...and strong wind shear. Strong to severe
thunderstorms are expected to develop...and as a result the storm
prediction Center has put the majority of the region into Enhanced
Risk for severe wx...with only a small portion in Slight Risk to the
SW. Have put in enhanced wording for the afternoon hours to reflect
this.

For temps...daytimes highs will range mainly in the mid to upper
70s. Some locales may even reach near 80F in far E/SE zones. Locales
in NE Colorado may only reach near 70F as a result of cloud cover.
Overnight lows tonight will range from the upper 40s west...to the
mid 50s east.

.LONG TERM...(Thursday night through Wednesday)
Issued at 223 PM MDT Wed May 25 2016

Thursday evening is the primary period of concern with this extended
forecast period. A severe weather outbreak should be anticipated as
several favorable factors come together. First, a warm front will
provide a focus for thunderstorm development Thursday afternoon.
Storms will continue across the region Thursday evening. Second, an
extremely unstable atmosphere is forecast by many guidance members.
SBCAPE in the 2000-3500 J/KG range is likely. Further, strong height
falls of 6-8 dam are indicated as the negatively tilted low passes
over. In addition to the large instability, a highly sheared
atmosphere should also develop. 0-6 KM Bulk Shear of 50-60 kts
should be realized shortly after noon. 0-3 KM Helicity of 300-450
m2/s2 is also forecast, and environment highly favorable for
tornadoes. Finally, the upper level forcing will be perpendicular to
the boundary these storms form on. This means that storms should
initially be supercelluar before activity congeals into an MCS.
Expect a continued threat for very large hail, damaging winds, and
tornadoes (some strong, long-tracked possible) to persist well into
the evening hours. Storms will progress north-northeast and should
exit the region by midnight. Some shower/thunderstorm activity will
persist through the overnight hours, particularly on the western
edge of the departing low along and west of the Colorado border.

Aside from Thursday night, am anticipating chances for convective
activity to persist across the region throughout the extended
forecast period. The severe weather threat should diminish for at
least Friday and Saturday. This is because the negatively tilted
trough slides northeast away from the region. In addition, the
dryline surges east into eastern Nebraska and eastern Kansas,
greatly reducing the high atmospheric instability.

Atmospheric instability becomes quite high once again for Sunday
through Tuesday as moisture return from the southeast commences.
However, a lack of significant disturbances or a highly sheared
atmosphere suggests the severe weather threat should be much lower.
There will be enough shear for a few severe thunderstorms each day,
given the instability buildup, but any type of severe thunderstorm
outbreak currently appears unlikely.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1142 PM MDT Wed May 25 2016

Currently: VFR conditions and lull in shower/thunderstorm
activity at both KMCK and KGLD. By 09Z stationary front begins to
lift north and easterly return flow will bring very moist air mass
into over both terminals. There is a potential for stratus/fog
and thunderstorms as this front slides northward. Best chance for
IFR (or lower) will be at KGLD with a delay in stratus/fog
development at KMCK. There is also the potential for stratus to
linger at KMCK through much of the TAF period, though models are
inconsistent and I felt more comfortable leaning towards the more
positive end of guidance at this point. Better thunderstorm
potential tonight is at KGLD, with both terminals expected to be
impacted by thunderstorm activity Thursday afternoon/evening
(possibly severe).

&&

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

$$

UPDATE...DR
SHORT TERM...JN
LONG TERM...RRH
AVIATION...DR



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