564
FXUS63 KGLD 190447
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
1047 PM MDT Fri Aug 18 2017

.SHORT TERM...(This evening through Saturday)
Issued at 148 PM MDT Fri Aug 18 2017

Main forecast issue will be onset of thunderstorms and associated
hazards Saturday afternoon. Winds will become light and variable
with the winds staying the lightest in the eastern portion of the
area the longest. With lower dewpoints, no cloud cover, and recent
biases, undercut guidance a little in the eastern portion of the
area.

Lee trough/dryline develops or moves to near the Colorado border
during the mid and late afternoon hours. Shortwave trough will move
over the top of this surface feature at the same time. So expect
thunderstorms to develop in this area. However, guidance over all
and especially the high resolution guidance differs on where
initiation will be with convective feedback issues causing problems
with the Nam. So confined the pops mainly to the western half to two
thirds.

Most of the area is in a marginal risk. Severe parameters/indices
would support this and even expand it through most of the area. Also
precipitable water values increase into the 1.5 to 2 inch range. So
locally heavy rainfall definitely be a threat. For high temperatures
current guidance supports warming the maxes to near what the
previous forecast had so adjusted accordingly.

.LONG TERM...(Saturday night through Friday)
Issued at 151 PM MDT Fri Aug 18 2017

Saturday night and Sunday: Nearly zonal flow aloft will prevail
through early Sunday. High pressure slides east, out of Texas and
into the southeastern states late in the day, adding a slightly
monsoonal tendency to the upper flow across the four corners region.
This will assist in maintaining relatively high moisture levels
across the CWA. Not expecting much in the way or precipitation and
any thunderstorm activity would be isolated due to lack of upper
support.

Monday (Day of the eclipse): For Monday, a shortwave will take shape
in the lee of the Rockies. GFS soundings indicate increased moisture
levels at both the 700mb level and the 500mb to 300mb layer.
Condensation pressure levels are generally over 80 mb through the
afternoon, thus cloud cover will be dependent upon how fast the
shortwave develops and enhances the theta-e boundary. Once this
boundary forms, we will see increased cloud cover and thunderstorm
chances especially for the eastern two thirds of the CWA, otherwise,
scattered and variable cloud cover is likely with coverage
increasing during the early afternoon.

Tuesday through Thursday: The upper pattern becomes amplified as we
head into Tuesday. High pressure forms and extends into the northern
Plains with low pressure over both the eastern portions of the Great
Lakes region and the southern reaches of British Columbia. Look for
isolated thunderstorm chances at best each day as the ridge
dominates the pattern.

Friday: Model guidance varies greatly heading into Friday as the GFS
develops a closed low in the four corners region. This will move
through southeast Colorado and across western Kansas going into
Friday afternoon. CAPE will be approaching 2500 to 3000 J/Kg per GFS
guidance with deep layer shear upwards of 45 knots. If the guidance
remains consistent, we could see scattered severe thunderstorms and
very heavy rainfall.

&&

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1045 PM MDT Fri Aug 18 2017

VFR conditions forecast for the TAFs. South winds will become
breezy Saturday afternoon. Thunderstorms may develop near KGLD
during the latter half of the afternoon. Do not have enough
confidence at this time to put a mention in the TAFs.

&&

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

$$

SHORT TERM...BULLER
LONG TERM...TL
AVIATION...JTL