Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 111126

Area Forecast Discussion
National Weather Service North Platte NE
626 AM CDT Tue Aug 11 2020

.SHORT TERM...(Today through Wednesday)
Issued at 359 AM CDT Tue Aug 11 2020

The main forecast challenges over the next couple days revolve
around thunderstorms, including severe potential, and temperatures.
Mid-level shortwaves along with a surface warm front and then a
dryline will provide the forcing for thunderstorms, while
temperatures return to seasonably warm levels.

This morning... A surface warm front is progressing through the
western panhandle. Enhanced isentropic lift combined with a weak mid-
level shortwave may spark a few rain showers across northwest Neb.
As of 08z, radar echoes and cooler cloud tops (from IR) are moving
by KCDR, however no moisture is being observed at the surface.
Nevertheless, kept schc PoP across the far north through the mid-
morning given increasing low level moisture. The most aggressive
CAMS suggest isolated showers in Sheridan and Cherry, while most
solutions keep the area dry. H85 flow has fully transitioned to
southerly, signaling strong moisture advection into the region.
Patchy stratus has developed near the Platte River Valley and is
pushing north into the Sandhills. Light east winds at the surface
may aid in moisture pooling and lead to an expansion in the stratus
coverage this morning. Soundings and isentropic analysis indicate
fairly deep lift, so thinking stratus will be primarily favored over

This afternoon and evening... After the stratus dissipates and full
boundary mixing is achieved, WAA at H85 with temps reaching 25C
should translate to highs in the mid 80s north central to lower 90s
far west. Abundant mid level moisture will keep the sky from
clearing completely, which may hold max temps down a degree or two.
Regardless, conditions are setting up to be warm and unstable with
MUCAPE values exceeding 2000 j/kg across the area and H5-7 lapse
rates approaching 9C/km. The cap should break around 21z in the
panhandle where the forcing is strongest near the warm front and the
convective temp is more likely to be achieved. Soundings keep the
cap in check farther east through 00z. Expect iso-sct thunderstorms
to develop and then spread east, possibly reaching Hwy 83 corridor
00-03z and Hwys 183/281 corridors 03-06z. With deep layer shear of
30+ kts and some veering winds in the lowest 3km, conditions would
support supercells.

Tonight... Most of the storm activity should be out of the forecast
area by 09z, with the exception of far north central Neb. The LLJ
kicks into gear across the Sandhills with speeds approaching 40 kts.
It should nose into the Dakotas before veering east, which should
keep any overnight convection to the north of the forecast area.
Slow clearing of the clouds combined with continued weak WAA should
keep min temps milder than the previous few nights, ranging from
around 60 in the panhandle to upper 60s north central.

Wednesday... Even warmer weather is in store as H85 temps rise
another 3C or so, resulting in widespread 90s for highs. Low level
moisture sticks around as shown by dew points near 70F. This not
only leads to heat index values in the upper 90s, but also MUCAPE
values of potentially 4000 j/kg. Moisture convergence will be
maximized along a dry line that slowly nudges into the western
Sandhills. Large discrepancies exist in the CAMS regarding overall
coverage of thunderstorms, but hedging on at least isolated. The
NAMnest hints at rapid upscale growth into an MCS that barrels
through the forecast area during the late evening. Given ample
instability and modest deep layer shear up to 30 kts, this is one
possibility that will need to be monitored.

.LONG TERM...(Wednesday night through Monday)
Issued at 359 AM CDT Tue Aug 11 2020

Thursday and beyond... A large upper ridge maintains control over
the southern Plains while a trough tries to dig into the northern
Plains. This setup keeps Nebraska in quasi-zonal flow aloft, which
then transitions to northwest as the ridge builds across the Desert
Southwest. The potential for thunder appears to decrease from early
week, but left isolated mention through the weekend. A cool front
works through the region on Saturday, which would likely bring the
best chance at seeing precip. Hot and humid conditions remain up
until the front, then temps back off to lower/mid 80s.


.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 626 AM CDT Tue Aug 11 2020

A few aviation weather hazards arise over the next 24 hours,
including low ceilings this morning, thunderstorms this evening,
and low level wind shear late tonight. For this morning, an area
of stratus with patches of fog is advancing north across southwest
Nebraska. Cigs may drop to IFR at KLBF, along with brief drops in
visby around sunrise and shortly after. Isolated thunderstorms
then develop mid/late afternoon in the panhandle and spread east
through the evening. Strong erratic winds will likely accompany
any thunderstorm, while large hail is also possible. In the wake
of the storms, a strengthening southerly low level jet will lead
to wind shear conditions.




SHORT TERM...Snively
LONG TERM...Snively
AVIATION...Snively is the U.S. government's official web portal to all federal, state and local government web resources and services.