Area Forecast Discussion
Issued by NWS Goodland, KS

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS63 KGLD 170753

Area Forecast Discussion
National Weather Service Goodland KS
153 AM MDT Mon Jul 17 2017

Issued at 1025 PM MDT Sun Jul 16 2017

As has been the trend, rainfall activity continues to be slower
than expected. Forecast was roughly 3 hours ahead of current
storms coverage. Current data indicates most of the storm activity
will be over the southwest and south central part of the forecast
area before quickly moving northeast later tonight. Question now
becomes is this still too fast. Am still not very optimistic for
rainfall once the storms begin to shift more to the northeast
later on.

UPDATE Issued at 730 PM MDT Sun Jul 16 2017

Adjusted areal extent and timing of rainfall tonight based on
latest near-term data. RAP model seemed to have a decent handle on
current storm activity and had done well last night. The
frontogenesis in the 600-500mb layer and lift in the 310K through
325K levels indicate the storm activity will develop near the
CO/KS border early this evening and be in a north-south line. This
lines up well with the 500mb vorticity that will be rotating
around the center of the closed upper level low. The storms will
move little this evening, so wherever the storms form, they will
linger there for awhile. Have good confidence in the
location/timing of storms this evening, however confidence is
lower for overnight. Models are split with the storms either
tracking more north-northeast or northeast. Regardless of the
track the storm activity will gradually decline overnight as 500mb
vorticity declines. Will hold off making significant adjustments
to the rainfall chances for overnight to see how storms
develop/move, and see if the data comes into better agreement.


.SHORT TERM...(This afternoon through Monday)
Issued at 204 PM MDT Sun Jul 16 2017

Plume of deep moisture continues to linger over our CWA (apparent
on WV imagery), with mid-upper low near CO border.

This afternoon-Tonight: Thunderstorm activity is already beginning
to redevelop along western edge of main instability/moisture axis
near the CO state line. Latest RAP analysis indicates SB CAPE in
excess of 2000 J/KG and supports ML CAPE increasing to this range
within the next few hours. Shear is very weak, so other than less
organized isolated stronger cells (marginal hail) main concern
continues to be hydro. MOdels show increasing forcing over our CWA
as a strong lobe of vorticity on back side of mid level
circulation rotates over our CWA this evening and overnight.
Result should be increasing coverage, though with CAPE decrease
during the evening hours, moderate to occasionally heavy showers
may be favored over thunderstorms. I adjusted PoPs/QPF with latest
short range consensus blends to match these trends.

Monday: Main mid-upper low should be northeast of our CWA, but
lingering forcing on back side of system may support continued
shower and thunderstorms chances in our northeast and east.
Moist/unstable air mass in the afternoon could support isolated
activity further west near building surface trough, but current
guidance is favoring our east with possible subsidence in our west.
Bulk effective shear should be near or just above 30kt, so with
better shear we may have a better chance for severe thunderstorms in
our far northeast than we have had over the past few days.

Regarding temperatures: As has been the case, cloud cover and
linger precip complicate overnight lows, with locations that
clear out dropping to near 60F (more likely west). Otherwise,
where precip lingers overnight lows may not drop much lower than
the upper 60s/near 70F. With mid-upper low exiting and surface
trough building in our west we should see WAA through the day
Monday. This will support highs in the 90s, with a few locations
possibly reaching the 95-98 range assuming good clearing/mixing.

.LONG TERM...(Thursday through Sunday)
Issued at 151 AM MDT Mon Jul 17 2017

Thursday and Friday: CWA will be influenced by the upstream side of
H5 high pressure. Instability will begin to increase very slowly
from the west and northwest through the afternoon; however, CAPE
looks to only build to around 800 to 1500 J/Kg with the Canadian
being the most aggressive model. A few thunderstorms could form
along a theta-e boundary through Thursday afternoon mainly in the
far northwestern corner of the CWA. This boundary will sag further
southeastward and weaken as we head into Friday, bringing
thunderstorm chances slightly further into the CWA. Once more,
instability will be high enough for thunderstorm development during
the afternoon and evening with a few stronger storms possible.
Temperatures on Thursday and Friday will be well above average,
climbing into the upper 90s to just over 100 degrees both days.

Saturday through Monday: A cold front will push through the region
on Saturday with more widespread thunderstorm chances during the
afternoon and evening hours. CAPE will approach 2000 J/Kg with deep
layer shear around 45 knots. This should provide an environment that
will support a few strong to severe thunderstorms along and ahead of
the front as it moves from northwest to southeast, slowing down atop
the CWA overnight. Another round of thunderstorms will develop
Sunday afternoon as the front slowly moves out of the region. The
influence of the ridge will move further east at this point;
however, the general tendency of the pattern will likely build
another ridge to the west as we head into Monday and Tuesday.  High
temperatures Saturday through Monday will be much cooler with highs
generally reaching the middle 80s to middle 90s with Saturday being
the warmest day of the three.


.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1145 PM MDT Sun Jul 16 2017

VFR conditions expected for the TAFs. Have become more skeptical
of rainfall reaching KGLD tonight. Storm activity ended up being
about 3 hours behind the forecast. Current radar shows the storms
are mostly south of the site too. While vicinity showers are
likely, some showers may still move over the site for an hour or
two. Have low confidence for a shower moving over KMCK later
tonight. If any showers do make it that far north, they should be
west of the site.

Tomorrow some storms may be near KMCK in the afternoon, with most
of the storm activity to the east of the site. At this time do
not have enough confidence to place a mention of storms in the




AVIATION...JTL is the U.S. government's official web portal to all federal, state and local government web resources and services.