Area Forecast Discussion
Issued by NWS Goodland, KS
FXUS63 KGLD 011737
Area Forecast Discussion
National Weather Service Goodland KS
1037 AM 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...(Sunday through Wednesday)
Issued at 249 AM MST Thu Dec 1 2016
The concerns during this period are the temperatures that turn
sharply colder on Tuesday and Wednesday along with the possibility
of precipitation on Monday night through Wednesday.
The closed low that developed over northern Mexico lifts out of
Mexico and across Texas on Sunday and Monday as the next larger
scale low pressure area dives along the west coast of Canada and
enters the northwestern U.S. The initial short wave rotating around
the low lifts out of the central Rockies and moves into the northern
plains Monday night. The second short wave dives in the back side of
the upper low and takes a further south path as it moves east of the
Rockies and emerges over the panhandle region Tuesday night. Model
solutions begin to diverge to a greater degree in lifting this wave
east across the plains on Wednesday. The GFS is more progressive
and has the trough approaching the Mississippi Valley region by
Wednesday evening while the slower ECMWF has a more amplified
pattern with a sharper trough developing and digging deeper south
over the far southwest U.S.
The model consensus along with the Blender output agrees with an
overall colder pattern with temperatures turning sharply colder
following a cold front that moves across the forecast area by Monday
afternoon. Between Monday and Wednesday, high temperatures drop from
the upper 40s to the upper teens and mid 20s while overnight lows
drop from the 20s to between 5-10 degrees by Wednesday night.
The latest GFS may be overproducing QPF amounts, but it may bear
watching along the favored upslope areas extending east of the
Palmer Divide region. Consensus produces mainly snow with very
little mixed phase precipitation that begins Monday evening and
continues in some fashion through the day on Wednesday. Latest
models have precipitation coming to an end by mid day Wednesday, but
the blended solution has yet to pick up on that. Have generally
accepted the blender solution with the expectation that there will
continue to be multiple changes regarding precipitation amounts and
placement, especially following the development and transition of a
frequently problematic closed low over northern Mexico lifting out
across the southern plains. Current expectations for snow across
the forecast area are around 1 to 1.5 inches across far northeast
Colorado and southwest Nebraska with 2 to 2.5 inches further south
along and south of a line extending from around Flagler to Hill
City. The peak snowfall time is between midnight on Tuesday night
and noon on Wednesday as the second short wave trough rotating
through the main upper trough takes a more square aim on the eastern
Colorado and western Kansas.
.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.