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FXUS63 KLBF 092201

Area Forecast Discussion
National Weather Service North Platte NE
401 PM CST Mon Dec 9 2019

.SHORT TERM...(This evening through Tuesday night)
Issued at 336 PM CST Mon Dec 9 2019

Impacts/Highlights and Confidence: Limited sensible weather
concerns in the short term. There is potential for flurries or 
very light snow across parts of northern NEB tonight into tomorrow
morning, best chances across far northwest NEB with little to no 
accumulation expected. 

Impacts/Highlights and Confidence: Latest day cloud phase 
distinction imagery and surface obs show scattered to broken mid 
and high level ice clouds tracking eastward across the area. A
weak northern stream positive pv anomaly moves into the Central 
High Plains late today/early tonight. Moisture and magnitude of 
forcing is a concern. Lee-side convergence sets up tonight from 
the black hills under northwest flow along with the development of
lower tropospheric frontogenesis focused across northwestern NEB.
Current thinking is this will result in mainly flurries to very 
light snow with soundings show dry air that needs to be overcome
initially at low-levels with a very light QPF. Decreasing sky 
cover then tomorrow with fair conditions through tomorrow night.
Northwest flow aloft tomorrow then keeps cooler temperatures in
place with only little improvement compared to today.

.LONG TERM...(Wednesday through Monday)
Issued at 336 PM CST Mon Dec 9 2019

Impacts/Highlights and Confidence: Warming trend takes hold early
in the long term peaking Friday. Friday highs are forecast in the
40s to lower 50s ahead of a front, this is about 5 to 10 degrees 
above seasonable normals. Slight chances for snow Friday night. 
However, confidence is low in occurrence and location/timing at
this time. There is then potential for unsettled conditions/snow 
Saturday night-Sunday but confidence is low due to a wide forecast
envelope. It will be something to monitor as we go forward.

Discussion: Large scale pattern will be characterized by a mid-
level longwave trough extending from Hudson Bay south to the Lower
Mississippi Valley early Wednesday. Upstream there is northwest
flow over western NEB and a northern stream shortwave trough
apparent near northern ID embedded within an upper trough. Weak 
southerly low-level flow starts to form Wednesday as the flow
aloft becomes zonal that starts a slight warm up in the far
southwest. The northern stream trough then tracks southeastward 
into the central High Plains by Wednesday night. Meanwhile, a weak
cold front is expected to advance into the area with the main 
sensible weather impact more so related to wind/wind shift. 
Warmer conditions anticipated Thursday as a lee-side trough 
sharpens with a developing surface low pressure system near 
southern Alberta/Northern High Plains associated with a shortwave
trough near southern Alberta. This upper trough digs south into 
the Northern Plains Friday with its cold front starting to then 
move into the area. However, moisture and forcing appears to be 
limiting factors with respect to precipitation. The former with 
dry air in place in the lower-levels and the latter with the best 
lift late Friday and Friday night northward along with the better 
isentropic ascent at 285K and 290K surfaces in the DGZ. Colder air
moves in this weekend with a stronger cold front late Saturday 
and Saturday night. While there is potential for unsettled 
conditions and snow chances this weekend as an upper trough 
deepens in the western CONUS, there is increasing uncertainty 
given forcing and timing seen between guidance. 


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1112 AM CST Mon Dec 9 2019

Latest satellite imagery showed low stratus across the western and
central Sandhills has diminished. Latest surface obs continue to
show breezy northwest winds across the area with gusts generally 
20-30 mph. The main aviation concerns revolve around ceilings
tonight-early tomorrow and low-end chances for light snow or 
flurries tonight. Winds will lessen gradually over the course of 
today as broad high pressure currently over southern SD moves to 
eastern NEB. A weak cold front sagging south that will help aid 
light winds across northern NEB, along with low-end chances for 
light snow and flurries, best chances across northwest NEB. Low 
confidence in light snow affecting KVTN terminal thus no mention 
at this time in the TAF. Ceilings will deteriorate to MVFR across
much of northern NEB overnight with low-end VFR (less than 7 kft)
spreading across the remainder of the area late tonight-tomorrow 
morning. Mostly cloudy skies are then expected to prevail into 
early tomorrow.



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