816 
FXUS63 KGLD 211707
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
1007 AM MST Thu Dec 21 2023

.SHORT TERM...(Today through Sunday Morning) 
Issued at 254 AM MST Thu Dec 21 2023

Water vapor imagery shows a shortwave across SE Colorado and NE New 
Mexico moving towards SW Kansas along with a surface low. Out 
ahead of these features some fog is located mainly across west 
central Kansas into central Nebraska. The fog in in west central 
Kansas is from moisture advection, this will be the area of that 
Gove, Sheridan, Graham and Norton will need to watch for through 
sunrise. Some localized dense fog will be a possibility especially
across eastern portions of Gove and Graham counties. As the above
mentioned shortwave moves into the area, light rain will help end
any residual fog. For the rainfall chances went with a blend of 
the WRF-NSSL, HRRR, and NAMNEST. Overall confidence in the SE 
portions of the area being affected by rainfall is around 30-40%, 
it would be higher but there is concerns of the quality of the 
moisture as water vapor does show some dry air aloft just ahead of
the shortwave. Rainfall will slowly move out of the area 
throughout the day, so opted to lower high temperatures across the
east into the upper 40s. Into tonight, some Hi-Res guidance does 
show some fog returning in the extreme eastern portions of Graham 
and Norton county so kept some patchy fog wording in. 

Friday, looks to be a transitional day as a strong upper level low 
develops across the SW CONUS. From a pattern recognition 
standpoint, the day ahead of a strong low is warmer, so went with 
some the warmest guidance I could find (ADJMEX), the fact as well 
that skies will be mainly sunny and breezy southerly winds further
increases my confidence in this occurring. The entire area is 
forecasted in the upper 50s to low/mid 60s. Moisture begins to 
increase again from the south during Friday evening into the 
overnight hours, so will need to keep an eye on fog/stratus 
concerns. If moisture advection and clouds are quicker than 
currently forecasted then overnight lows into Saturday morning may
be to low, so will need to keep an eye on this trend. 

Saturday, as the low moves onto the Plains, the chances for 
precipitation will increase. The NBM loaded in definite pops 
(greater than 80%) ; however if the system takes more of a 
northeast path I do have concerns about dry slotting hurting the 
precipitation chances so opted to put likely wording in (~55-70%) 
as my highest pop in case this does occur. Saturday will have a 
spring time feel to it as dew points will surge into the mid to 
upper 40s to maybe even the low 50s out east. I also went ahead 
and put in a mention of thunder mainly for Highway 25 on east as 
guidance continue to indicate a couple hundred joules of CAPE 
present. The EFI as well, has been consistently showing anomalous
CAPE values, which yes it is late December so it doesn't take much
CAPE to be anomalous. Overall, I wouldn't be surprised if 
thunder, lightning and some small hail is observed especially out 
to the east. Severe weather is not anticipated. 

Saturday night, is when the forecast begins to get tricky. As the 
low moves off to the east, wraparound cooler air will work into 
western portions of the area. As this occurs rainfall will turn into 
snow, additional showers and storms would continue to be possible
across the east through the overnight hours. I did end up moving 
the rain/snow line a bit further east before sunrise Sunday based 
on the latest runs of wet bulb zero, as this precipitation event 
currently looks to be similar to last week where rate driven 
change over from rain to snow would be likely helping the profile 
reach its wet bulb temperature. Depending on the overall 
changeover, some light snow accumulation would be possible across
the higher elevations of Yuma and Kit Carson county as we head 
into Christmas Eve Day.

.LONG TERM...(Sunday through Thursday)
Issued at 337 AM MST Thu Dec 21 2023

Summary: The Christmas winter weather system is still showing a 
good amount of uncertainty particularly with snowfall amounts and
duration, but slick roads and potential blowing snow may cause 
hazardous travel conditions on Christmas Eve and Christmas Day. 
Please watch for future forecast updates as they become available!

At the beginning of the long term period on Sunday, forecast 
guidance differs a bit with the GFS showing the CWA underneath the 
front of an upper air trough while the ECMWF shows the CWA east-
southeast of an upper air low over ID/UT/WY during the morning 
hours. By Sunday night, the GFS shows the axis of its upper air 
trough passing over the CWA while the ECMWF has its low moving over 
the CO/KS border. For Monday, the GFS develops an upper air low over 
NE in the afternoon that moves over the CWA in the evening and 
starts to progress eastward into central KS overnight. The ECMWF's 
solution for Monday slowly moves the upper air low across the CWA 
during the day before placing it over the eastern KS/NE border by 
the evening and going into the overnight hours. For Tuesday, the GFS 
continues the eastward progression of the upper air low into the 
southern Great Lakes region allowing for the forward portion of a 
trailing ridge to move over the CWA by the nighttime hours. The 
ECMWF on the other hand has a slower progression of its low and 
keeps it near the IA/MO border throughout the day giving the CWA a 
northerly flow. For Wednesday and Thursday, the GFS continues the 
eastward progress of the upper air ridge with its axis passing over 
the CWA on Thursday afternoon. By Thursday night, the GFS gives the 
CWA a west-southwesterly flow aloft as the ridge continues to move 
eastward. The ECMWF's solution for Wednesday shows the CWA with a 
north-northwesterly flow aloft during the evening being between an 
upper air ridge to the west and an upper air trough to the east.
The ECMWF on Thursday then projects a northwesterly flow over the
CWA by the evening as a strong upper air low moves down from 
Canada over the MN/WI border. All in all, there looks to be some 
pretty good uncertainty in the long term upper air pattern with 
all of these differences between the extended deterministic 
models. Still too early to tell which model looks best at this 
time. Upon looking at the ensemble models for the upper air 
pattern, they might appear to be a bit closer in their solutions 
in the last few days though some differences still exist. Will 
monitor this going forward as this uncertainty continues to make 
this a difficult forecast.

At the surface, the CWA looks to see chances for wintry 
precipitation on Sunday lasting into Tuesday. The GFS has a surface 
low over southern KS on Sunday morning that shoots northeast into IA 
by the evening hours. The ECMWF takes a different track for its 
surface low with it beginning in northern KS on Sunday morning that 
slowly moves east over the KS/MO/NE border area by the evening and 
resides in that general area until Tuesday evening. With this setup, 
both models show pretty good agreement for chances (PoPs of 50-70%) 
for precipitation at least through Sunday evening. The CWA looks 
to be split in P-Types with the eastern half seeing mostly light 
rain while the western half sees a light rain/snow mix on Sunday 
morning before transitioning to all snow from west to east on 
Sunday night. On Monday, chances for light snow across the CWA 
come down a bit with PoPs of 15-30% due to the differences between
where the long term models place the system. The ECMWF shows 
better chances for light snow to continue particular in the 
eastern portions throughout Monday while the GFS starts having the
precipitation chances depart the CWA early Monday and remain 
mostly east and out of the CWA throughout the rest of the long 
term period. The ECMWF shows the snowfall chances not tapering off
until Tuesday evening with its system stalling out east. As a 
result, snowfall totals differ quite a bit since the ECMWF has 
almost 1.5 days extra worth of possible light snow chances that 
the GFS does not. As a result the latest possible snowfall
forecast totals range from around 1 inch in southern portions of 
the CWA to around 4 inches in the eastern portions of the CWA from
early Sunday into early Tuesday. The ECMWF ensemble currently 
does show a 30% probability of greater than 6 inches in the 
northern half of the CWA which does seem possible if the ECMWF 
solution comes to fruition with the extra snowfall time. The 
latest EFI value for snow on 00Z Monday continue to around 0.7 
while the 00Z Tuesday EFI snow value is almost 0.6 which continues
the trend of a potential positive anomaly in snowfall on Sunday 
and Monday within northern portions of the CWA. Looking at the 
current potential for at least 1 inch of snow using the model 
certainty tool, models show better potential for areas north of 
I-70. Will continue to monitor future models runs for better 
confidence in this system and which model's outcome looks more 
probable, but there is still a good amount of uncertainty at this 
time. Forecast QPF values range from around a tenth in the 
southwestern quadrant to around a half of an inch in the 
northeastern quadrant. Beyond Tuesday evening, the CWA looks to 
stay dry as temperatures slowly creep upwards.

Another concern for the Christmas system looks to be a blowing snow 
hazard particularly on Sunday and possibly Monday. A cold front 
passing through the region early Sunday will allow for some north-
northwesterly winds gusting up to around 30-35 kts in the western 
half of the CWA through most of the day which will blow any falling 
snow and causing the potential travel hazard. These stronger wind 
gusts may spread a little eastward in the CWA on Sunday night as 
well. Maximum wind gusts on Monday look to be slightly slower at or 
under 30 kts which may allow for more blowing snow chances even as 
the snowfall chances look to decline on Monday. Will continue to 
monitor these chances, but travelers should prepare for potential 
reduced visibility due to blowing snow as it along with slick road 
conditions could make travel hazardous during the Christmas holiday.

As for the temperature forecast for the extended period, the Tri-
State Area looks to see daytime highs between the middle 30s and 
lower 50s on Sunday followed by Monday's highs in the lower to upper 
30s range. Daytime highs on Tuesday are forecast to be in the lower 
to middle 40s while Wednesday's highs range between the middle and 
upper 40s and Thursday's highs range between the middle 40s and 
lower 50s. Overnight lows on Sunday expect to be in the middle teens 
to middle 20s with Monday's overnight lows being in the upper teens 
to lower 20s. Tuesday night lows look to be in the lower 20s 
followed by the remainder of the forecast period seeing overnight 
lows in the lower to middle 20s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1006 AM MST Thu Dec 21 2023

VFR expected to prevail at both KGLD and KMCK through the TAF
period. Considerable high clouds will continue through this
afternoon with a shortwave trough moving through the area. Surface
winds will be light and variable. 

&&

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

$$

SHORT TERM...Trigg
LONG TERM...076
AVIATION...024