123
FXUS63 KGLD 210552
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
1152 PM MDT Mon May 20 2024

.KEY MESSAGES...

- A Tornado Watch remains in effect until 2 AM MDT Tuesday
  morning for locations along and north of Highway 36.
  Torrential rainfall and isolated flash flooding are possible,
  especially in southwest Nebraska.

- Potential for patchy frost in northeast Colorado early
  Wednesday morning. Very low confidence.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 250 PM MDT Mon May 20 2024

Across the region this afternoon, with a low/front sitting over
west central Kansas, skies are mixed with sunny conditions
west, and partly sunny east due to a persistent veil of low
cloud associated with the vicinity of the low/front. Winds have
shifted easterly from the mornings northerly fetch, and
temperatures as of 200 PM MDT are ranging mainly in the 70s with
some 60s due to extensive clouds.

Looking aloft, the latest RAP40 500mb analysis is showing broad
SW flow over the region, with a elongated trough pushing
through the north central Rockies. It will be this trough, via
current guidance, that swings off the Rockies and east-northeast
into the north central Plains this evening. This will be
followed by a weaker system on Tuesday with a more easterly
track along the northern fringe of the cwa.

For the short term period, the latest wx concerns continue to
focus on the threat for severe wx this afternoon/evening,
flooding chances later tonight into Tuesday morning. There are
also chances Tuesday/Tuesday night for another round of
rain/thunder.

Currently, with a frontal boundary extending west from the
central Kansas area into central Colorado, this will be the
focus for storm initiation as the upper trough moves off the
Rockies. Current CAMs(HRRR, RAP and NamNest) show development
around 00z Tuesday, moving east through northeast Colorado,
before shifting into SW Nebraska this evening. Some differences
as to the placement/movement of the convection as it moves out
of Colorado, but the overall trend does impact SW Nebraska at
the minimum. Threats do diminish as your push southward through
the cwa. Best chances look to occur along and north of highway
36. SPC does continue to carry an Enhanced Risk for Nebraska,
tapering to a Slight Risk for severe for areas south of this to
Interstate 70, then Marginal concerns thereafter.

Model soundings show decent instability from 00z-06z Tuesday
across the Enhanced Risk area as SBCape/MUCape all reach into
the 2000- 3000j/kg range. Hodographs do support tornado
potential, but large hail up to baseballs and winds up to 70-80
mph are possible, especially north of the Interstate. Things do
taper sharply the further south you go away from the shortwave
vicinity.

Other concerns through tonight will be the threat for flooding
due to heavy rainfall as the storms pass. We do have the
Enhanced Risk area under a Marginal for excessive rainfall. This
will all depend on storm speed through the area tonight. PW
values do approach the 1- 1.3 inch range this evening as east-
southeast flow persists. Have continued the Flood Watch with the
addition of Dundy county through 12z Tuesday.

Another round of rain is expected on Tuesday/Tuesday evening,
with the passage of another shortwave. Surface low south of the
cwa will help funnel moisture into the area, with the focus
along and north of the Interstate. Currently instability is low
so not expecting severe storms at this time, but another round
rain could impact already prone areas. Another Flood Watch could
be needed but will be highly dependent on what is received
tonight in certain areas.

The final issue in the short term will be the threat for patchy
frost Tuesday night. Guidance continues to show cloud cover
meandering over the expected impacted areas in Colorado. With
the uncertainty, have left out mention as temps into the upper
30s at worst.

For temps, with a cold front moving through the region on
Tuesday, a wide range in daytime highs is expected with mid 60s
to mid 70s forecasted. Warmest locales will be along/south of
Highway 40. Overnight lows tonight expected to range widely with
mid 40s to lower 50s west, into the mid 50 through 60F east. A
bit colder Tuesday night, especially west of Highway 27, with a
range from the upper 30s west into the upper 40s east. The lows
for tonight are highly dependent on cloud cover from remnant
storms through tonight. Tuesday night, cloud cover will impact
temps, especially for northeast Colorado. Current guidance keeps
frost chances low at this time, but could encompass much of Kit
Carson, Cheyenne and Yuma counties if cloud cover clears out.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 156 PM MDT Mon May 20 2024

From the latest GFS/ECMWF, west-southwest aloft at 500mb will
persist during the long term period, supplemented by the passage
of a few weak shortwaves through Friday with both models
carrying a few stronger system over the region for the upcoming
weekend. The timing of each system looks to occur during the
evening hours at this time, but can`t rule out some late
afternoon development, especially this weekend.

At the surface, inverted trough Wednesday evening will give way
to a stronger lee-side trough Thursday. while the placement
west of this system during the day will give the region decent
above normal warmth, this will sink south and east of the CWA
Thursday night into Friday. A low on the south side of the
trough on Friday remains over the OK Panhandle region for
Saturday, followed by another lee-side trough for the end of the
upcoming weekend.

Looking for low chances(30-40%) for rw/trw in the Wed-Fri
timeframe, but it will be the weekend/early next week systems
which will give a better potential for areal coverage of qpf. Of
course these will be highly dependent on storm track timing
through the CWA. With all the rain expected before the midweek
timeframe, additional qpf could put more locales into flood
prone status and will have to be monitored.

For temps, daytime highs on Wednesday will range in the lower
to mid 70s. Warmest day in the extended will occur on Thursday
with lower to mid 80s expected. Thereafter, Friday will have
another cooler day with mainly 70s, increasing to a range from
the upper 70s to mid 80s by next Monday. Overnight lows will
mainly range from the mid 40s west into the lower and mid 50s
east. Warmest locales will be along/east of Highway 83.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1145 PM MDT Mon May 20 2024

GLD: IFR-LIFR conditions associated with low ceilings are
expected after midnight (~06Z). While convection cannot be
ruled out at the beginning of the TAF period, the latest high
resolution convection allowing guidance.. and ongoing radar
trends.. suggest that activity will likely remain ~20-30 miles
north of the GLD terminal. Ceilings are anticipated to gradually
lift/improve to VFR late Tue morning and early Tue afternoon.
Variable winds will abruptly shift to the NNW-NW and strengthen
to 20-30 knots within a few hours of sunrise (as a lee cyclone
over western KS progresses eastward into central KS). Breezy
NNW-NW winds will persist through late morning to early
afternoon.. decreasing by mid-late afternoon.

MCK: Expect conditions to rapidly deteriorate ~07-08Z as severe
thunderstorms capable of producing very large hail and damaging
winds progress eastward from Hitchcock County into Red Willow
County. Episodic showers and storms are possible throughout the
day on Tuesday. 10-15 knot NNE-NE winds will shift to the NNW-
NW and increase to 15-25 knots within a few hours of sunrise (as
a lee cyclone in western KS progresses eastward into central KS
and NE).. persisting through the day on Tue.

&&

.GLD WATCHES/WARNINGS/ADVISORIES...
KS...None.
CO...None.
NE...Flood Watch until 6 AM MDT /7 AM CDT/ Tuesday for NEZ079>081.

&&

$$

SHORT TERM...JN
LONG TERM...JN
AVIATION...Vincent