Area Forecast Discussion
Issued by NWS Goodland, KS

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139
FXUS63 KGLD 291335
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
735 AM MDT Mon May 29 2017

.UPDATE...
Issued at 735 AM MDT Mon May 29 2017

Updated the forecast to remove mention of showers this morning for
the CWA. Current satellite showing mainly msunny conditions with
no radar echoes over the area. Still a slight chance in for the
afternoon hrs. No other changes at this time.

&&

.SHORT TERM...(Monday through Wednesday)
Issued at 320 AM MDT Mon May 29 2017

A few isolated showers will continue through the morning as a cold
front makes its way through the forecast area. Widely scattered
thunderstorms will then develop this afternoon along the front and
in the post frontal upslope environment, perhaps helped by a weak
shortwave aloft in the northwest flow. Instability will peak in
the afternoon at around 600-700 j/kg with deep layer shear around
35kts. Cannot rule out an isolated strong storm mainly due to the
shear, but with limited instability the threat will be low.
Scattered weak storms will continue into tonight as they move
east southeast with the mean flow, ending after midnight.

Northwest flow continues on Tuesday. The old frontal boundary may
try to sneak back into the forecast area during the afternoon as a
warm front. Convergence along the front and surface heating should
be enough for isolated thunderstorms to develop. Instability looks
even weaker than Monday, so not expecting any severe storms. They
will diminish during the evening hours with loss of surface
heating.

Wednesday is shaping up to be the most interesting day of the
short term period for thunderstorms. Frontal boundary again looks
to be in the area as it slowly lifts north as a warm front.
It is currently forecast to be near an Imperial to Hill City line
at the time of peak afternoon heating. Instability will be
maximized along and just north of the front where strong
instability of up to 3000 j/kg is forecast. Moderate instability
is forecast elsewhere. Deep layer shear will be strongest near and
north of the front as well, with 40-50kts forecast by the models,
dropping to around 25kts south of the front. The front itself
will be the strongest forcing mechanism, as a ridge tries to build
in from the the west and upper heights are rising. So coverage
will probably be rather limited, but any storms that do develop
could become severe, especially near/just north of the frontal
boundary.

Temperatures will be near normal today and above normal Tuesday
and Wednesday.

.LONG TERM...(Thursday through Sunday)
Issued at 146 AM MDT Mon May 29 2017

Upper flow pattern will be somewhat split across the southern and
central High Plains on Thursday. A ridge of high pressure will be
positioned just west of the CWA with a deep trough moving onshore in
the Pacific Northwest. Subsidence under the ridge will keep things
dry across the CWA on Thursday; however, moisture levels will build
as south to southeast winds prevail through the day.

A dryline will set up on Friday, providing a focus for thunderstorm
development during the afternoon and evening. CAPE values will
approach the 1500 to 2000 J/Kg range; however, due to the lack of
shear both in the 0-1 km layer as well as the 0-6 km layer,
supercell development is not expected. The more likely mode will be
multi-cell cluster type storms capable of pulse type severe activity
to include hail and damaging wind gusts. Due to the proximity of the
dryline and theta-a boundary, we will need to monitor the potential
for landspout type tornadoes mainly during the late afternoon hours
as there could be just enough low level shear along these boundaries
to allow for brief spin-ups. Additionally, due to very weak upper
flow, storm motion will be quite slow and with PW values around
1.10 inch, we could see localized flash flooding potential.
Showers and thunderstorms could persist into the overnight hours
as the dryline retreats slightly through around midnight.

Global models significantly disagree about the flow pattern going
into Saturday. Generally, a shortwave ridge will begin to set up to
our west once more with weak shortwaves propagating down the leading
edge into the CWA. Slight thunderstorm chances will remain in the
forecast at this time; however, with the ridge being in very close
proximity and approaching from the west, there may be just enough
CIN to prevent anything more than an isolated thunderstorm or two.

For Sunday, another weak shortwave will push across the region as
the ridge slides eastward. Chance PoPs are in the forecast with
afternoon thunderstorms being possible from west to east. The
strength of the thunderstorm activity looks very uncertain at this
time as CAPE values will only be in the 500 to 1000 J/Kg range with
weak 0-6 km shear.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 515 AM MDT Mon May 29 2017

VFR expected at both KGLD and KMCK through the TAF period. A cold
front will move through this morning with surface winds gradually
veering from west to northwest. Widely scattered showers and
thunderstorms will develop this afternoon near the front, but it
will be past both terminals by that time and chances appear slim
that they will directly impact either one.


&&

.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...NONE.
NE...NONE.
&&

$$

UPDATE...JN
SHORT TERM...024
LONG TERM...TL
AVIATION...024



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