498
FXUS63 KGLD 221746
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
1046 AM MST Fri Nov 22 2024

.KEY MESSAGES...

- Brief warmup today and Saturday before a cold front Sunday
  afternoon/evening brings temperatures back to normal.

- Slight chance (20%) of light snow Sunday PM currently favoring
  Yuma county.

- Holiday travel could be impacted by some precipitation
  across the area next Wednesday and Thursday. Stay tuned for
  further updates.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 152 AM MST Fri Nov 22 2024

Mid level ridging is ongoing across the High Plains along with some
high clouds moving NW to SE down the eastern periphery of the ridge.
This upper level cloud cover may impact the amount of radiational
cooling across the north and eastern portions of the area through
the morning as light winds and dew points in the mid teens to low
20s are present. If the upper clouds don`t make it or thin out any
then temperatures do look to cool to the current forecast in the low
20s. Through the rest of the day, the ridge looks to bring quiet
weather to the Plains with clear skies and light winds. Temperatures
will continue to be above normal with highs in the mid 50s to low
60s across the area as 850mb temperatures look to rise to the 11-13C
range across the area. Friday night will see winds from the SW
overnight which looks to help moderate the overall cooling as the
winds will be from the climatologically favored 210-240 degree range
so have nudged temperatures up a few degrees closer to the
freezing mark. The exception is across the northeast primarily
Hitchcock, Red Willow and Norton counties where a subtle ridge
axis looks to nudge into that portion of the CWA allowing winds
to become calm and support the potential for some patchy fog
currently favored across eastern portions of Red Willow and
Norton counties. Upcoming shifts will need to monitor this
potential in case the area favored for fog shifts any further
west or south.

Saturday, ridging remains across the area but doesn`t appear to be
as pronounced as some effects from a system across the northern
Rockies begins to influence the pattern. Do have some concerns
of cirrus where if it thick enough which may be the case based
on the amount of 300mb RH temperatures may not warm up to their
potential as 850mb temperatures of 12-15C are favored by nearly
all guidance. As a result of this concern I did trend
temperatures down towards the low to mid 60s.

Sunday winds will become more ENE as the ridge begins to break down
in advance of an incoming cold front. High temperatures for Sunday
are a little tricky as there are signals in ensemble guidance of the
cold front moving through during the mid afternoon vs the evening as
deterministic guidance suggests. Typically cold fronts do move
through quicker than what guidance shows so have trended
temperatures down some. Along or just behind the front may also have
the potential for some snow currently looking to favor Yuma county
via mid level moisture forecasts of the GFS and ECMWF. At this time
it currently appears that light snow with minimal if any
accumulations is the most likely outcome however guidance
overall isn`t in great agreement with the amount of moisture
available which as of this forecast package does lead to
overall low forecaster confidence. Typically the NAM which
normally favors a higher moisture bias has less moisture
available throughout the atmospheric profile than the GFS. So
despite the larger and higher GFS mid level moisture that signal
on the NAM does make me question whether or not the snowfall
will even occur so will continue with the slight chance (15-24%)
snow chances. The GFS also does show a fairly strong 7-9mb
pressure rise over 3 hours behind the front which would support
breezy to gusty winds along with the snowfall which may lead to
some blowing snow concerns, with potentially a dry snow favored
as strong cold air advection occurs; conversely the NAM has very
little pressure rises along with the lack of snowfall. Overall,
continue to monitor the forecast as these inconsistencies with
guidance should resolve itself over the next 24-36 hours.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
Issued at 213 AM MST Fri Nov 22 2024

We will start the long-term in a fairly calm, zonal pattern with the
250 mb jet sitting overhead of the CWA until about 12Z Wednesday.
During the first 48 hours, we can expect an 850 mb weak high to keep
us cool Monday with highs in the 40s. Overnight Monday, the ridge
axis moves east and we will receive southerly flow Tuesday, allowing
us to warm near 50.

Come Tuesday evening and lasting through the overnight hours, a jet
streak over the southern California coast is expected to create a
surge of moisture that will move across the southwestern CONUS. This
moisture will end up in the southern Great Plains Wednesday
morning. The tracking of this moisture is most easily done
looking at the the 300K maps.

On Wednesday, a heavily tilted trough extending from a low north of
the Great Lakes to northern California will push the jet stream
south, out of the CWA. As the jet exits the CWA, we can expect a
wave or two of vorticity, acting as a forcing mechanism for
potential precipitation.

Confidence is extremely low on what exactly will happen with this
system, but here are a couple options that could play out based on
current guidance.

Option 1 (GFS/Dry Solution): The trough pushes the cold front
through the Great Plains before the moisture has a chance to arrive
from the west. This would keep the moisture south of the GLD area,
reducing our PoPs to less then 15% across the CWA.

Option 2 (ECMWF/Warm and Wet Solution): The moisture arrives before
the trough and cold front. This would greatly increase PoPs, likely
to around 60-70% for most of the area. Precipitation would start off
as rain early Wednesday morning. The cold front would pass through
the area later in the morning Wednesday, transitioning the P-type
into snow by Wednesday evening. However, during most of the day
Wednesday, a rain/snow mix would occur across the CWA. Worst case
scenario, black ice would form in the evening and overnight hours
Wednesday. More likely would be a slush forming instead of ice.

Option 3 (CMC-NH/Cold and Wet Solution): The moisture and cold front
move into the area at basically the same time. This would lead to
PoPs around 20-35 in the northern CWA increasing to around 60 in the
southern CWA. Also, the P-type would mostly be snow with a little
rain/snow mix in the southern CWA. Having snow be the dominate P-
type would greatly reduce the potential for re-freezing or black
ice, or slush forming.

With options 2 and 3, the higher QPF amounts would be focused on the
western CWA, rapidly lowering by highway 27. Travel may be impacted
Wednesday into Thursday morning, but there is too much uncertainty
at this point to know any specifics.

Regardless of which precipitation scenario plays out, we are
expecting temperatures to cool off for Thanksgiving, aided by
northwesterly winds. Current NBM guidance suggests highs on the
holiday will be in the mid 30s to low 40s. If there is snow,
temperatures will lower, otherwise, they could rise a few degrees.

Friday, there are some suggestions, primarily from the GFS with the
ECMWF also hinting at it, we could see another through impact the
area. There does not seem to be any moisture associated with this
trough, but a northwesterly 850 mb LLJ does look possible. If this
feature forms, we could see efficient CAA Friday evening and night,
but we`ll focus on that more tomorrow.

List of acronyms:
NBM - National Blend of Models
GFS - Global Forecast System
ECMWF - European Centre for Medium-range Weather Forecasts
CMC-NH - Canadian Meteorological Centre-Northern Hemisphere
CAA - Cold Air Advection
PoP - Probability Of Precipitation
LLJ - Low Level Jet
K - Kelvin
QPF - Quantitative Precipitation Forecast
P-type - Precipitation type
mb - Millibar
kts - Knots
Z - Zulu time (UTC)
CWA - County Warning Area
CONUS - CONtiguous United States
GLD - Goodland

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1044 AM MST Fri Nov 22 2024

VFR conditions forecast for the TAFs. Light and variable winds
will continue for both TAF sites. KGLD winds will be a bit more
consistent, thus the added lines for the TAFs.

&&

.GLD WATCHES/WARNINGS/ADVISORIES...
KS...None.
CO...None.
NE...None.

&&

$$

SHORT TERM...Trigg
LONG TERM...CA
AVIATION...JTL