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000
FXUS63 KGLD 220826
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
226 AM MDT Tue Jun 22 2021

.SHORT TERM...(This evening through Thursday)
Issued at 200 PM MDT Mon Jun 21 2021

Upper ridge will quickly rebuild over the southern and central
High Plains on Tuesday, persist into Wednesday, then finally break
down on Thursday with a shortwave trough approaching from the
northern Rockies.

Main story for all three days in the short term period will be the
return of much above normal temperatures. Expecting highs on
Tuesday to be in the mid 90s, then lower 100s on Wednesday,
FOLLOWED by 90s to 100s on Thursday as a prefrontal trough
bisects the area. Main cold front associated with the shortwave
does not arrive until Thursday night.

For Tuesday and Wednesday, may see an isolated thunderstorm or two
pop up along a surface boundary/lee trough due to intense surface
heating and some weak support aloft. On Tuesday, that boundary
will lie roughly along a McCook to Tribune line, with a couple of
CAMs showing isolated development after 21z, primarily in
southwest Nebraska. The environment will be weakly unstable but
strongly sheared, around 55kt of deep layer forecast, so although
the threat will be very isolated, any storm that does develop may
bring a localized risk of large hail (there are some loose
matches for significant hail in the SARS sounding analogs) and
gusty winds (DCAPE up to 1500 j/kg) through the early evening
hours before dissipating. Latest SPC outlook for Tuesday does
bring a marginal risk into the northeast corner of the forecast
area, McCook to Norton, where these parameters are best. On
Wednesday, the surface boundary retreats into northeast Colorado.
Another weak impulse comes out of the central Rockies in the late
afternoon around the ridge axis. CAMs, mainly the 3km NAM, do show
isolated storms popping up near the surface boundary. Environment
is again weakly unstable, but deep layer shear remains around
40kts. Main hazard if storms develop on Wednesday will likely be
wind, with more of an inverted-V type sounding in Colorado due to
hot, deeply mixed surface layer resulting in DCAPE of up to 2000
j/kg, and a lesser risk of hail, but still some loose SARS matches
there.

Best chances for precipitation will be with the main cold front
and shortwave on Thursday night. However, global models not in
particularly good agreement on timing or QPF. GFS much wetter
compared to the ECMWF, especially in northeast part of the
forecast area, where GFS appears to be generating an MCS that
moves out of the Nebraska panhandle. ECMWF has little to no
QPF during that time, so confidence remains low on details for
Thursday night.

.LONG TERM...(Friday through Tuesday)
Issued at 224 AM MDT Tue Jun 22 2021

The extended period begins with a surface low over the Great Lakes
with an accompanying cold front moving south through the Northern
Plains and eventually through the Tri-State area during the day
Friday. As the cold front moves south, precipitation chances
become possible over the northern counties during the morning,
then chances increase during the early afternoon and evening for
areas along and south of Interstate 70. As of right now, the
severe threat looks low but an isolated severe storm may be
possible over over the southwestern quadrant of the CWA as the
front will interact with a warmer, moist airmass. Inverted V
soundings indicate that strong winds would be the hazard if a
severe storm does occur, confidence is low at this point. As the
front moves through the area, temperatures should be noticeably
cooler with highs in the upper 70s to low 80s north of I-70; south
of Interstate 70 will continue to see highs in the mid to upper
80s however. If the front moves through quicker than anticipated,
then high temperatures would need to be lowered across the entire
area.

Saturday, will be cooler across the entire area with highs in the
mid 70s to mid 80s. The low over the Great Lakes moves off to the
east and as a result moves a deepening trough into the High Plains
during the afternoon hours. Currently it looks as if the best chance
of showers and storms will be across Colorado as guidance indicates
some drier air working its way into west central Kansas from the
Nebraska panhandle.

For the latter portion of the extended period, guidance indicates a
ridge developing over the western CONUS as the previous days trough
moves east leaving the High Plains with northerly flow. Overall this
period looks dry but some afternoon thunderstorms may develop off of
the Front Range and track east into the CWA. Confidence is to low at
this point to introduce rain into the forecast to account for this.
Temperatures should gradually increase with 80s on Sunday, to
eventually the lower 90s for highs on Tuesday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1135 PM MDT Mon Jun 21 2021

VFR conditions forecast for the TAFs. Main impact will be the LLWS
expected at both sites after 9z. The breezy surface winds are
slightly delayed from when the low level winds increase, so
decided to put a mention in for the LLWS. Once the breezy surface
winds begin the LLWS will end.


&&

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

$$

SHORT TERM...024
LONG TERM...TT
AVIATION...JTL