Area Forecast Discussion
Issued by NWS Goodland, KS
FXUS63 KGLD 012008
Area Forecast Discussion
National Weather Service Goodland KS
108 PM MST Thu Dec 1 2016
.SHORT TERM...(Today through Saturday night)
Issued at 249 AM MST Thu Dec 1 2016
Main forecast concern will be chance of precipitation Friday night.
Satellite showing a somewhat amplified but progressive and active
flow from the Pacific into North America. Broad trough encompasses
much of the country with slow moving cold upper system near the
Great Lakes and a complicated/developing upper trough from southwest
Canada into the western portion of the country.
At mid levels the models were close and doing surprisingly well in
this active/complicated flow. The Gfs, Canadian, and Ecmwf were
starting out best with the low level thermal field.
Today/tonight...It will be a cold start to the day with light
downslope winds in place. As shown yesterday by the models, mid and
upper level moisture increases during the day, mainly in afternoon,
in advance of western trough. This looks to be a little slower than
yesterday. Current temperature forecast looks reason and made little
to no changes. Cloud cover continues to thicken during the night
however the thicker cloud cover looks to be mostly in the western
half. So the eastern half will have a chance to drop to near to
below guidance and made slight adjustments in that direction.
Friday/Friday night...Cloud cover continues to thicken during the
day but not as fast as previously indicated. Light upslope winds
will be in place through the day. Not a lot there to allow a lot of
warming. Temperatures look similar to todays, and that looks
reasonable and did not change the blend.
The new forecaster blend maintained the thoughts of the day forecast
in keeping a 20 to 30 percent chance of precipitation during the
night in the southern half, which is a lot more that it was showing
24 hours ago. Main jet is south and east of the area so do not
expect help from it, although upper level deformation is decent.
Models show incoherent and unorganized mid level frontogenesis
moving across. Theta-e lapse rates are not very favorable for a good
response to the lift that is there.
Also models are not entirely agreeing on the moisture profile. The
Gfs saturates the air mass down to or just below 700 mb with a dry
layer in place in the southern half of the area. The Nam saturates
the air mass from 700 mb and below. The Gefs probabilities for .05
are less than 10 percent. The Sref probability for .01 is near 30
percent which matches what the blend has. Will keep a slight chance
to low chance of precipitation but the data would indicate amounts
will be very light if we get anything at all.
Saturday/Saturday night...Lift and moisture decreases right before
the beginning of this period and resulting precipitation looks to
have ended as well. The forecaster blend has no measurable and
that looks reasonable. Cloud cover will decrease slowly with light
winds not allowing for a lot of mixing. Temperatures once again
look about the same, and see no reason to change from what the
blend gave me.
.LONG TERM...(Friday night through Thursday)
Issued at 108 PM MST Thu Dec 1 2016
Going into the extended period...the Tri State region will see
two different systems set to affect portions of the CWA. The first
system involves a cutoff low that dives well into northern Mexico
by Friday night. A shortwave does move in tandem slowly with this
low over the northern plains. Strong surface ridging is in place
over a good portion of the Central/Northern plains with the
arrival of these systems. This ridging will allow for blocking of
any major moisture to really work up into the CWA...w/ only the
northern fringe scraping portions of the southern CWA before
shifting east by Saturday morning. With model qpf only pointing
towards a few hundredths of an inch at best...temps in the 20s
will only mean a slight chance for light snow of a few tenths of
an inch at best. The focus for any accum will be south of
Interstate 70 and east of the KS/CO border.
The second of the 2 systems is set to affect the CWA over a 36-42 hr
period...current depicted in latest models from next Monday night on
thru the morning hrs of Wednesday. Models bring this winter wx maker
in as an upper low/arctic front combo. There have been model
discrepancies on timing/strength of this system over the past few
days in terms of snowfall potential. Decent confidence that the CWA
will definitely see a profound shift in temperatures...setting the
area into more of a winter pattern. A shortwave working around the
base of this upper low/trough works thru the CWA. Latest GFS has
more of a north-south pattern set up for the precip that
occurs...while the trough in the ECMWF digs further south and precip
with this has more of an west to east sweep thru the CWA. These
differences are allowing for different snowfall totals. Surface
ridge that will work in behind this exiting system does play a role
late in the period with any easterly fetch that sets up providing an
upslope component that could enhance snow totals...especially over
NE CO. For now the CWA will be looking at an ~1-3 inch potential
based on model consensus...with higher amounts north of I-70. With
several days ahead before this system arrive any change in
track/timing could have these numbers adjusted significantly.
While the snowfall expected for the CWA still has an uncertainty
factor to it...what is certain for the CWA is that the area will see
overall temps drop sharply thanks to the passage of the arctic
front. Before its passage...CWA will highs range in the 40s for Sat-
Mon...then shift down to mainly the 20s for Tues-Wed. The arrival of
the surface ridge going into Thursday will allow for a rebound back
into the 30s. Overnight lows will see 20s before fropa...down to low
teens and single numbers above zero for Tuesday and Wednesday nights.
Accompanying these colder temps overnight will be windy conditions
that will bring wind chill readings as low as -5 to -10 below in
some locales for tues/wed nights.
.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1037 AM MST Thu Dec 1 2016
Vfr conditions are expected to prevail throughout the TAF period.
Winds will be light and generally from the west/northwest. A
disturbance approaching the area causes cloud cover to increase
overnight into tomorrow. No aviation impacts are anticipated.