Area Forecast Discussion
Issued by NWS Goodland, KS
FXUS63 KGLD 151729
Area Forecast Discussion
National Weather Service Goodland KS
1029 AM MST Sun Jan 15 2017
.SHORT TERM...(This morning through Tuesday night)
Issued at 336 AM MST Sun Jan 15 2017
A negatively tilted upper level trough is currently centered over
norther Mexico with diffluent flow aloft extending out across the
plains. A plume of deep moist air is advecting north across the
plains ahead of this trough.
Winter storm still expected to impact our CWA, though there have
been trends supportive of lowering amounts/impacts for NW parts of
Large scale divergence within diffluent flow aloft continues to
spread northward into our CWA. Lightning activity indicates
instability advecting northwards in region of WAA aloft. Radar
shows light to moderate precipitation returns (dual pol fields
indicating liquid and some areas of sleet) moving north-northeast
from SW Kansas. There have already been reports of accumulating
freezing rain upstream in southern Kansas. Short range guidance
shows this activity continuing to transition north and then
northeast with freezing rain/sleet spreading across much of our
CWA though this morning.
Latest model trends of all guidance show an easterly jog of main
upper low as it turns and moves over the plains. This results in
main axis of forcing/moisture advection to shift eastwards while a
slightly deeper cold layer moves out of the north transiting
precip to sleet then snow over our CWA during the day today. RAP
shows slightly warmer surface Tw, but most other guidance still
supports freezing surface temps. A deformation band is still
shown to develop tonight as this trough makes its turn with the
band elongating along the stretched out occlusion through Monday.
Due to this track confidence is lower in the higher amounts
previously advertised, as better forcing will remain west and warm
conveyor may be cut off from most of our CWA. A period of moderate
snow is still possible particularly Monday morning. Precip during
the day today may end up being lighter as a result of main waves
shifting just to our southeast. With instability and a slower
progression we may still see snow amounts exceed warning criteria
late tonight and Monday morning, but there enough
variances/questions with latest guidance to lower confidence some.
Forecast changes: I trended freezing rain amounts downward based on
these trends, though I still think our south/southeast is in line
for warning criteria ice. Sleet/snow accumulation may end up
dominating this afternoon/evening before moderate snow develops
tonight and I made adjustments to reflect this. I replaced the
Winter Storm Warning in Yuma county with an advisory to reflect
confidence in lower accumulations in northeast CO.
As the transition to sleet/snow occurs midday and we get a better
handle on trends we may need to convert ongoing Warnings as well
(particularly Ice Storm Warning). I was not as confident yet in
the remaining counties to make a change at this time, as the
ingredients are still there for warning level conditions to
Monday night-Tuesday night: There may be a brief period of
forcing Monday evening supportive of flurries or very light snow,
otherwise we should see a drying trend as subsidence builds aloft.
Temperatures Moderate Tuesday and we should be above freezing,
however any lingering snow/ice on the ground will complicate
potential diurnal heating.
.LONG TERM...(Wednesday through Saturday)
Issued at 235 AM MST Sun Jan 15 2017
Forecast concerns will be affects of upcoming storm on temperatures
at the beginning this period, and the next chance of precipitation
toward the end of the period. Satellite showing a progressive but a
little more amplified flow over most of the Pacific with an even
more amplified and split flow over the western portion of the North
America, especially over the western portion of the country.
Again a little uncertainty on the high temperature forecast at the
beginning of the period due to not knowing for sure how much of the
area will be covered by snow/ice and how much snow/ice there will
be. Do not feel as confident as yesterday about lowering
temperatures. So made little to no changes in the temperature
forecast through the period.
As yesterday,there continues to be a lot difference among the
deterministic output and the ensembles. Models were also different
from yesterday. From Wednesday through Thursday night the models
develop a cutoff over the central/south central plains and then move
it east. The Ecmwf is furthest north, the Gfs the furthest south
with the Canadian in the middle.
From Friday into Saturday night, the models develop a negatively
tilted upper trough over the western half of the country. A lot
detail differences start with shortwave trough rotating through the
area in southwest flow aloft. The strongest of these through in the
Friday to Friday night frame.
Right now the forecast blender gave me spotty precipitation chances
Friday and Friday night with the better/more widespread
precipitation showing up on Saturday and beyond. Based on the above
will leave the precipitation forecast alone, and hope for better
resolution of the details as we get closer.
.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1029 AM MST Sun Jan 15 2017
For KGLD...conditions will range briefly MVFR down to mainly an
IFR/LIFR mix. Looking for a change in precipitation from more
freezing rain/sleet to snow by 21z-22z this afternoon as colder air
works into the region. This will drop visibility from 3sm down to a
1/2sm to 2sm range. Ceilings to remain below ovc005 thru the
forecast period. Winds...ESE around 5-10kts becoming NNE aft 05z
For KMCK...conditions will be a MVFR/IFR mix as visibility ranges
from 5sm down to 1-2sm with a change over to snow around 21z this
afternoon. Ceilings will go from ovc015-025 down to ovc010 or less
by 21z. Winds mainly light/variable thru 14z Monday...then north
KS...Winter Storm Warning until 7 PM MST /8 PM CST/ Monday for
Ice Storm Warning until 11 AM MST /noon CST/ Monday for KSZ004-
CO...Winter Storm Warning until 7 PM MST Monday for COZ091-092.
Winter Weather Advisory until 7 PM MST Monday for COZ090.
NE...Winter Storm Warning until 7 PM MST /8 PM CST/ Monday for