Area Forecast Discussion
Issued by NWS Goodland, KS

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799
FXUS63 KGLD 260326
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
926 PM MDT Tue Jul 25 2017

.UPDATE...
Issued at 922 PM MDT Tue Jul 25 2017

Just completed an update. Raised mins in the east. Guidance has
been consistent in having the lows in those locations a few
degrees warmer than currently forecast. Also adjusted winds to
match the recent trend of a gust front moving across the area in
advance of the incoming cold front. Hrrr caught this nicely and
used that.

Thunderstorm coverage and intensity has been decreasing. Model
guidance has been poor and inconsistent with this, even the high
resolution and rapidly updating output is not doing well. So will
leave alone for now, and continue to watch trends. Still may trend
down later.

UPDATE Issued at 632 PM MDT Tue Jul 25 2017

Just completed an update to adjust pops. All scale of model output
having difficulty as to where to pinpoint locations of
thunderstorms. Majority of output emphasizes the west and
especially northwest portion of the area. Current activity does
support that. However, where the models are lacking and where the
update had to be made through the rest of the night was for the
convection over the south and west central portion and activity
approaching from the southwest.

The model catching the details the best right now, especially over
and near our southern areas is the Nam. Using it and latest trends
expanded pops further east faster and also farther east. Based on
that also adjusted the qpf.

&&

.SHORT TERM...(This afternoon through Wednesday)
Issued at 1126 AM MDT Tue Jul 25 2017

17Z Water vapor imagery indicated large anticyclonic circulation
centered over south central Colorado. Morning soundings indicated
a large change in airmass qualities between KDDC and KDEN. KDEN
sounding was primarily dry with steep (greater than 8 C/km) lapse
rates off of the surface. KDDC was much more humid with PW values
of 1.29 inch and a fairly deep moist layer, but with overall poor
lapse rates between H7 and H5. At the surface, trough axis was
draped across eastern Colorado with dewpoints in the mid and upper
60s to its east and dewpoints in the 50s to the west.

Thunderstorm chances will be primary forecast concerns tonight and
tomorrow, followed by magnitude of cool down behind cold front
Wednesday.

Various short range models show a lot of variance with respect to
how afternoon and evening thunderstorms develop. Solutions vary
from storms remaining near sfc trough to forming into large
cluster and advancing across whole CWA. Starting to see cumulus
development along trough which may shed some light on how storms
will evolve. As cold front advances south tonight and short wave
trough flattens ridge somewhat, expect storms to advance to the
east and south with best coverage mainly along and north of
Interstate 70 where large scale forcing and available instability
most in line.

Expect storms to diminish in the morning hours with the bulk of
the morning and afternoon being dry across the area. Thunderstorm
development will be heavily influenced by how much clearing and
heating can occur. Should a low stratus deck maintain itself this
will greatly diminish potential for any post frontal storms.

Overall confidence high that temps will be around 15 degrees
cooler than today in northwestern CWA, but confidence in frontal
position lower to the south so not ready to dial down temps a lot
in this area.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 141 PM MDT Tue Jul 25 2017

Wednesday night-Thursday: As front pushes through the area, there
will continue to be a a chance of storms and showers across our
southern CWA. Model soundings are not that impressive on shear and
CAPE, therefore, widespread severe weather is not expected at this
time. Thursday should be dry with ridging aloft. Temps will be
below normal Thursday with highs in the low to mid 80s and
overnight lows in the upper 50s and low 60s.

Friday-Tuesday: Upper level ridge amplifies over the Rockies placing
us in strong NW flow aloft. Monsoonal moisture plume builds back
into the area. A series of shortwaves should traverse the periphery
of the ridging through the period. Will have chance of showers and
thunderstorms each afternoon and evening. Saturday night into Sunday
looks to have the best chance of precipitation. Models also hinting
at a good amount of fog Sunday morning, but chose to leave out of
the forecast at this time, since it was in the Day 5/6 period.
Temperatures will be near normal for the time frame.

&&

.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 544 PM MDT Tue Jul 25 2017

For Kgld, vfr conditions and south southeast winds are expected
through mid evening. From 04z to 07z thunderstorms are expected to
be near or affect the site. At this time chose to just have vcts
because high resolution models are showing a variety of scenarios.
There are currently storms to the west and north of the area. Will
amend if storms become move certain. However, mvfr conditions
will be possible with the stronger storms. Because of surface
boundaries and outflow from storms the winds will be variable in
direction from mid evening until mid morning tomorrow. A cold
front will start moving through the area around 15z with sustained
winds near 18 knots with gusts to near 26 knots. This and mvfr
ceilings are expected until 20z. At that time vfr conditions and
north winds near 15 knots are expected.

For Kmck, at this time vfr conditions are expected through the
entire period. south southeast winds near 15 knots with gusts to
near 22 knots will decrease to 12 knots near sunset and will
continue until the middle of the night. At this time it looks like
thunderstorms will be near or affect the site from 05z until 08z.
As with Kgld uncertainty is above average due to model
differences so will have vcts during this time. This will also be
the time period where mvfr conditions could occur and high
variable winds due to outflow. Around 15z a cold front will also
move through this site as north winds increase to near 15 knots
with gusts to near 22 knots. This will continue until the end of
the period.


&&

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

$$

UPDATE...BULLER
SHORT TERM...JRM
LONG TERM...SME
AVIATION...BULLER



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