Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 211734 AAA

Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
1234 PM CDT Fri Jul 21 2017

.SHORT TERM...(Today and tonight)
Issued at 409 AM CDT Fri Jul 21 2017

Weather highlights the next 24 hours revolve around hot and humid
conditions today and thunderstorm activity this afternoon-tonight.
Local radar display shows an area of elevated thunderstorms over
far north central NEB moving northeast with predominantly inter
-/intra-cloud flashes and infrequent cloud to ground lightning
associated with them. These thunderstorms have increased in
coverage over the last hour or so in far north central NEB to
northeast NEB in response to a zone of amplifying low-level
(850-700 hPa) warm advection. Current thinking is these storms may
linger in extreme north central NEB through the small hours then
move off east based on radar trends and guidance.

Inherited heat advisories in decent shape. Downsloping winds in
place today in the High Plains from across the Panhandle into far
western NEB that should promote drying with lower minimum
afternoon RH in the eastern Nebraska Panhandle and far western NEB
compared to yesterday. Largely hotter temperatures will prevail
compared to yesterday with appreciable thermal ridge at 850 hPa
setting up overhead western and north central NEB. 850 hPa
temperatures ranging from 28-32 C. For context, SPC sounding climo
for today shows a daily average of about 22, and a 90% centered
moving average and daily max value of 26 C and 31 C, respectively.
A well-mixed boundary layer and steep lapse rates are anticipated
this afternoon with adequate insolation to prompt highs 10-15
degrees above seasonal normals. Further, dew points across
southwest NEB to extreme north central NEB will range from the mid
50s to about 70 degrees. As such, no changes made with heat index
readings for the most part peaking 100-105 degrees.

Otherwise, isolated strong to severe thunderstorms anticipated
today with ample instability in place. Thunderstorms are expected
to develop in the afternoon, best chances between mid afternoon-
early evening, across southwest NEB into central NEB. There could
be locally heavy rainfall as well tonight, attributable to
regeneration with tracking over the same location and slow storm

.LONG TERM...(Saturday through Thursday)
Issued at 409 AM CDT Fri Jul 21 2017

With an H5 ridge building over the Great Basin and a progressive
low over the Great Lakes, Nebraska is placed in northwest flow
through the weekend. The ridge broadens across the Plains through
Tuesday, then begins to break down mid to late week. Toward the
surface, one low pressure moves along the NE/KS border on
Saturday, a cool front is dragged across SoDak late Tuesday, and a
stronger cold front drops through Nebraska late Wednesday.

Saturday... As the surface low tracks across northern Kansas and a
mid level shortwave pushes through the Sandhills, kept chc TSRA
across SW Neb. NAM and GFS soundings agree in keeping the best
moisture in the mid levels, generally above 700mb, so precip
coverage may be scattered at best. However, the NAM is rather
bullish in low level forcing associated with the sfc low. Dry air
entrains into the system by Saturday evening, which should taper off
any remaining showers/storms around sunset. The severe threat is low
as CAPE and deep layer shear are limited. Temperatures are a bit
tricky, dependent on the expanse of the thick cloud cover and the
coverage of TSRA. Trended max temps down slightly in SW Neb, while
kept lower to mid 90s across the north. Forecast soundings also
indicate backed winds.

Sunday through Tuesday... Southerly flow resumes at H85, which will
allow for a slow warming trend. Highs in the lower 90s seem
reasonable given H85 temps around 25C and a mixed layer to 700mb.
Just a couple small chances of precip to contend with during this
period. On Monday, a trough approaches the Black Hills, which may
help trigger iso T in the panhandle with the help of some upslope
flow. Late Tuesday, the system moves through SoDak, where some
precip may skirt far northern Neb. The best forcing and moisture
remain north of the border.

Wednesday and Thursday... Nebraska takes a more direct hit with a
cold front. GFS and ECM are in general agreement with bringing the
front through the area Wed night into early Thu. GFS suggests a
stout low level thermal ridge ahead of the front, translating to mid
90s for highs, especially if convective initiation is sluggish. The
best forcing and moisture don`t arrive until later Wed in the
panhandle and western Sandhills. Post frontal moisture remains with
dew points in the lower 60s, so can`t rule out sct TSRA Thu, mainly
across SW and central Neb.


.AVIATION...(For the 18Z TAFS through 18Z Saturday afternoon)
Issued at 1234 PM CDT Fri Jul 21 2017

The model consensus of the RAP, HRRR, NAM and HRRR exp appear to be
keying on a disturbance moving through Ncntl Colo as the forcing for
storm development across Swrn Neb this evening. The models appear to
be ignoring the robust CAPE across Ncntl Neb. This instability is
ahead of a cold front moving through Wyoming which could form a
stronger cluster of thunderstorms late this afternoon and this
evening. This cluster of storms could ultimately form near or across
Scntl Neb.

850mb winds this evening become northeast and this should support
upslope theta-e advection into Colorado supporting the model
consensus. This storm activity would be late evening and overnight.
Precipitable water will be very high supporting locally heavy
rainfall. Storm activity should dwindle 09z-12z Saturday morning.


Heat Advisory until 8 PM CDT /7 PM MDT/ this evening for



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