501 
FXUS63 KLBF 180115 AAA
AFDLBF

Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
815 PM CDT Sat Jul 17 2021

.UPDATE...
Issued at 815 PM CDT Sat Jul 17 2021

A forecast update is in place which lessens the chance of
thunderstorms across wrn Nebraska as suggested by the short term
model blend. The storm activity across the Panhandle will 
struggle to move east in wrn Nebraska for a few reasons. 

-KLBF UA sounding indicates warming has occurred aloft and the 
 lapse rates no longer steep.
-The resultant instability is low.
-The Corfidi vectors suggest the storm activity which becomes
 rooted in the boundary layer will move mostly south.

&&

.SHORT TERM...(This evening through Sunday night)
Issued at 349 PM CDT Sat Jul 17 2021

The main weather concern in the short term will be the chance of 
afternoon and evening thunderstorms today and tonight. A shortwave 
trough will combine with surface heating leading to an unstable 
environment across the High Plains by late afternoon. Storms will 
initiate in a fairly favorable environment with steep low level 
lapse rates (6 to 7 C/km) and CAPE values near 2000 J/kg. However, 
as storms move east, they are expected to encounter a slightly more 
stable region. This combined with rapidly dropping temperatures 
after sunset limiting diurnal instability will likely cause any 
storms to quickly weaken. As such, the best chance for any severe 
storms will be west of Highway 61, with lower chances as one moves 
east. Initially, threats will include large hail and strong winds, 
but as the evening progresses, threats will change to mainly a 
strong wind event. Small hail, frequent lightning, and heavy rain 
cannot be completely ruled out, they just won't be the primary 
threats. 

For Sunday, rain showers with isolated thunderstorms are expected to 
continue through much of the day. Current SPC outlook has most of 
the eastern half of the forecast area (east of US-83) in a marginal 
risk. While this seems appropriate, there is some concern that 
lingering rain and stratus may affect severe potential across the 
region. If stratus and rain showers end earlier than expected, 
allowing for some breaks in the clouds adding to diurnal instability, 
the potential for severe storms will increase. For now,though, the 
severe storm risk appears to be low. Stay tuned to later forecasts 
for possible changes severe risk especially tomorrow morning when we 
will have a better idea about the environment leading up to 
thunderstorm development.   

.LONG TERM...(Monday through Saturday)
Issued at 349 PM CDT Sat Jul 17 2021

The first part of the extended and next week will bring quieter 
weather to north central and western Nebraska. Strong upper level 
ridging and surface high pressure will build across the Great 
Plains. Strong warm air advection will also usher in a much warmer 
airmass bringing 850mb temperatures in the 24C to 30C range. These 
temperatures will easily support surface temperatures in the 90s, 
with highs even approaching the 100s in a few locations by Thursday 
and Friday. Despite warm daytime temperatures, overnight lows will 
drop off into the low to mid 60s. 

The next chance of precipitation is expected to arrive on Friday 
night and into next Saturday morning. Precipitation associated with 
a mid-level trough will skirt across northern Nebraska and into 
South Dakota. Confidence is quite low in timing, location, and 
strength of this late week system. Therefore, only introduced a 
slight chance pop (15 to 20 percent) into the forecast during this 
issuance. Any strengthening of the upper level ridge will make this 
entire precipitation chance disappear altogether. The models will get 
a better handle on this in the next few days.  

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 648 PM CDT Sat Jul 17 2021

VFR conditions are expected outside of convection for the
terminals.

Afternoon cu field in the LBF vicinity should dissipate by early
evening with the loss of daytime heating. Thunderstorms across the
Black Hills and near KBFF will drop southeast through the evening
and approach the OGA and IML areas. Confidence has decreased with
respect to seeing any activity approach LBF so have removed VCTS
mention for now. Will maintain VCTS for early morning Sunday at
VTN as elevated convection should develop across north central
Nebraska prior to sunrise with the remainder of the period
becoming quiet. 


&&

.LBF WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

UPDATE...CDC
SHORT TERM...Kulik
LONG TERM...Kulik
AVIATION...NMJ