Area Forecast Discussion
Issued by NWS Goodland, KS

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812
FXUS63 KGLD 200215
AFDGLD

Area Forecast Discussion
National Weather Service Goodland KS
715 PM MST Mon Feb 19 2018

.UPDATE...
Issued at 710 PM MST Mon Feb 19 2018

Current forecast for tonight looks in pretty good shape. Did
remove mention of blowing snow given winds in the 10 to 15 mph
range.

Convective looking showers starting to increase in coverage across
the western 1/2 to 1/3 of the area where weak elevated instability
and little cin forecast from a batch of moisture in the 850-500mb
layer through midnight. This batch of moisture and elevated
instability weakens around 09z then dissipates by sunrise.

Current snowfall forecast looks good but will have to watch where
any bands set up for possibility of axis shifting a bit from
current forecast location.

Based on current temperatures and dewpoints I did follow the
latest ruc/hrrr which has a good handle on things compared to
observed readings. Doing so lowered temperatures quite a bit from
previous forecast. Wind chill advisory criteria (-15F to -24F)
looks to be met in Yuma county which is already under a Winter
Weather Advisory.

&&

.SHORT TERM...(This evening through Tuesday)
Issued at 236 PM MST Mon Feb 19 2018

Forecast problem will be snowfall amounts tonight. Light snow has
fallen most if not the entire day over the northwest half of the
forecast area. This is despite the saturated air mass being below
700 mb. Not only was there ice in the column at the bottom of the
sounding according to the upstream 12z soundings but the dendritic
zone is at or near the surface. So the minor weak lift we have
received all day has allowed light snow or flurries to occur.
Accumulations so far have been near a half or below. The main change
for this air mass during the night will be for it to move over the
southern portion of the area and deepen over the remainder of the
area, especially in the northwest portion.

For tonight...Models are showing elevated Cape during the evening
over the western half of the area. But would not be surprised to
see this moving into the east overnight. I say that because
negative low and mid level theta-e lapse rates stay over the
western half of the area through the evening and then slowly
transition east through the rest of the night. So felt confident
to add isolated thunder to most of the area into the overnight
hours.

Right rear quadrant of upper jet starts affecting the northwest half
of the area during the mid and late evening. That area moves very
little during the night. Also strong mid level trough/baroclinic
zone and frontogenetic forcing follow this same path. High
resolution guidance has been very consistent through the day in
producing some bands of higher intensity snowfall near or over the
northwest corner. After running through all the parameters, I came
up with 3 to 5 inches of snow in the northwest corner, Yuma and
Dundy counties, for tonight. So went ahead and have hoisted a Winter
Weather Advisory for the night. The winds will be strong enough
enough that some patchy blowing snow will be possible, even a little
outside the area. Evening shift will have to watch if higher
snowfall amounts and the advisory need to be changed.

Also something else to watch for. Current forecast shows wind chills
dropping into the 10 to 15 below zero range in the northwest corner
as well.

For Tuesday...Above mentioned wind chills are in the northwest
corner during the morning. The mid level trough line stays to the
west the entire day. Models continue mid level lift and favorable
theta-e lapse rates over the area with the deepest moisture profile
over the northwest half. Baroclinic zone at 700 mb also remains over
the area. Above mentioned upper jet moves very little during the day
and is still affecting the southeast half of my area by the end of
the afternoon. Am thinking the models are ending snowfall to soon
and light snow or flurries could continue the entire day. Night
shift will have to look to see if this needs to be expanded or
increased.

Cloud cover, snowfall, snow cover, and an arctic air mass will keep
things cold with expected high temperatures near or below the
guidance blend.

.LONG TERM...(Tuesday night through Monday)
Issued at 254 PM MST Mon Feb 19 2018

A series of weaker short wave troughs will continue to rotate
through  the main upper trough over the western U.S. and lift out
across the Central High Plains region through the long term
period. The focus will remain on the two main systems that are
expected to bring the potential for a mix of wintery precipitation
to the forecast area. Colder high pressure will remain entrenched
over the Central High Plains Region through Wednesday with high
temperatures only reaching into the 30s.

On Thursday and Friday, the cold air begins moving east out of the
region ahead of a surface low and inverted trough developing over
SE Colorado ahead of one of the stronger short wave troughs aloft
lifting out across the region. Precipitation expected on Thursday
will likely start as snow and transition to light freezing drizzle
or light rain through the day on Thursday as the colder airmass
becomes more shallow and surface temperatures approach and
eventually go above freezing across a good portion of the forecast
area by late Thursday. Patchy areas of light snow or freezing
drizzle may continue Thursday night.

Another round of mixed precipitation is expected Friday night into
Saturday ahead of the main upper trough axis that moves across the
region early Saturday. Precipitation will again initiate as light
snow with a transition to rain during the day on Saturday as
daytime temperatures rise above freezing.

A more chaotic upper westerly flow develops across the western
U.S. through the remainder of the weekend into the beginning of
next week with some divergence in model solutions due to more
poorly defined smaller scale waves present in the upper flow. Dry
and warmer conditions are expected Sunday through Monday.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 420 PM MST Mon Feb 19 2018

For KGLD and KMCK, sub vfr conditions expected from taf issuance
through approximately 18z. Winds generally from the east and
northeast occasionally gusting near 20kts. Light snow will
continue for much of this period with an increasing chance this
evening as a weather disturbance moves over the terminals from the
southwest. Banded precipitation is possible and if it were to
develop over either terminal visibilities may be lower then
currently forecast. VFR conditions return during the afternoon
Tuesday with north winds gusting near 25kts through late afternoon
before falling below 12kts at the end of the period.


&&

.GLD WATCHES/WARNINGS/ADVISORIES...
KS...NONE.
CO...Winter Weather Advisory until 5 AM MST Tuesday for COZ090.

NE...Winter Weather Advisory until 5 AM MST Tuesday for NEZ079.

&&

$$

UPDATE...99
SHORT TERM...BULLER
LONG TERM...LOCKHART
AVIATION...99



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