Area Forecast Discussion
Issued by NWS Goodland, KS

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FXUS63 KGLD 281927
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
127 PM MDT Wed Jun 28 2017

.SHORT TERM...(Today and tonight)
Issued at 247 AM MDT Wed Jun 28 2017

Westerly flow is in place across the Central Rockies with sever
shortwave troughs propagating through the mean flow. The strongest
is currently east of our CWA with a general trend towards
subsidence in wake of shortwave trough and associated thunderstorm
activity. At the surface a Cold front has moved into our western
CWA, with surface low pressure over southeast Colorado.

Early this morning: Showers and isolated thunderstorms continue to
rebuild along/ahead of frontal zone in our north where axis of 1500
J/KG elevated CAPE is lingering. This should continue a eastward
transition and weakening trend before sunrise, supported by
RAP/HRRR.

Today-Tonight: Mid-upper level jet stream approaches region this
afternoon and moves into a position to put our CWA in line of a
couple jet structure over our CWA by this evening/overnight. Another
mid level shortwave trough rotates across the region from the west,
and showers/thunderstorms will begin to initiate in the west where
CAP weakens near surface trough. Coverage should increase this
evening with increased forcing, then transition eastward overnight.
NAM and to a lesser degree RAP were favored for severe parameters
with GFS possibly overly mixed. Tds in the lower levels in NAM may
be running high, but even conservatively we should see moderate
instability with increasing shear after 00Z with approaching mid
level jet and intensifying LLJ. Parameters continue to favor large
hail/damaging wind potential with thunderstorm activity. I increased
PoPs particularly in the evening and added severe mention to wx grids
during this mornings update.

Thursday-Thursday night: Larger upper level trough finally starts to
dig south out of Canada, with stronger forcing and a much stronger
cold front moving into our CWA. Current models depict main
instability axis across our south and east where NAM depicts MU CAPE
around 4000 J/KG. Shear is also much stronger during peak timing of
event. As would be expected this overlap of good deep shear, steep
mid level lapse rates, and higher CAPE values would support a much
better chance for super cell development and eventual MCS
development. The question will be if this favorable overlap is in
our area or shifted too far south or east based on frontal
timing/position of surface low. I went ahead and added severe
mention to wx grids.

Friday-Friday night: Post frontal air mass, increasingly stable air
mass, large scale subsidence should all support dry conditions. I
could see a window for lingering showers or weak thunderstorms
Friday morning as some models are still showing a lobe of mid level
vorticity transitioning east, but there isn`t a strong enough precip
signal to deviate for dry trend favored by model mean.

Regarding temperatures: Seasonally warm temps around 90F (maybe a
few warm spots in the middle 90s) are expected today as WAA rebounds
east of surface low. There is less confidence on highs Thursday due
to falling heights and approaching cold front. Current bend shows
spread of lower 80s post frontal (in our northwest) to near seasonal
in the lower 90s ahead of the pre frontal trough. Overnight lows
will tend to be seasonal tonight (50s west to upper 60s east). Post
frontal air mass Friday-Friday night will support below normal
temperatures in the upper 70s/80s and overnight lows in the 50s.

.LONG TERM...(Thursday night through Wednesday)
Issued at 127 PM MDT Wed Jun 28 2017

At the start of this extended period the models are showing an
amplified upper level trough moves out of the Central Canada with an
associated cold front and into the High Plains on Thursday. This
system looks to have enough instability to support the development
of super cell activity and possible MCS development over the region
Thursday night and into early Friday morning. There is still a
question in regard to what impact this system will have on the local
area as the track could shift to the south or east of our CWA. After
frontal passage, there will still be some lingering showers or weak
thunderstorms on Friday with temperatures reaching the upper 70s to
lower 80s.

Over the weekend, an increase in stable air mass and large scale
subsidence should support dry conditions on Saturday and into the
afternoon on Sunday. High temperatures will start out in the middle
80s on Saturday followed by the lowers to middle 90s on Sunday. Late
Sunday afternoon a chance of showers and thunderstorms return to the
local area as a surface trough combined with an upper level
shortwave approaches the area from the west.

Next week high temperatures look to maintain in the lower to middle
90s. Upper level troughs will pass over the local area on Monday and
will aid in producing another afternoon and evening of showers and
thunderstorms. As for the 4th of July, and the rest of this extended
period, the blended model is showing dry conditions. at this time I
see no reason to change anything.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1132 AM MDT Wed Jun 28 2017

VFR conditions forecast for the TAFs. Focus will be on the timing
of storms for both sites today/tonight. For KGLD anticipate
isolated storms moving out of CO late this afternoon will become
more numerous during the late evening. Reduced visibility in the
heavy rainfall and strong winds will be likely as any storms move
over the site. KMCK will be on the north edge of the better
chances for storm activity. Reduced visibility from the heavy
rainfall and strong winds can also be expected. Both sites could
receive hail from these storms.


&&

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

$$

SHORT TERM...DR
LONG TERM...BW
AVIATION...JTL



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