Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 161711 AAA

Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
1211 PM CDT Wed Aug 16 2017

Issued at 343 AM CDT Wed Aug 16 2017

H5 analysis tonight had a tandem of shortwaves across the central
Rockies and central plains. As of 2 AM CDT satellite and radar
imagery had one shortwave over north central Nebraska and a second
over central Colorado. Current radar imagery has a line of
thunderstorms extending from northeastern portions of the forecast
area, south into south central Nebraska. Behind this line, light
to moderate rainfall continued from Cody Nebraska south to Hayes
Center Nebraska and points east. Temperatures overnight were
generally in the lower to mid 60s.


.SHORT TERM...(Today and tonight)
Issued at 343 AM CDT Wed Aug 16 2017

Lingering precipitation chances today, high temperatures, and fog
potential tonight are the main forecast concerns. For today:
Decided to hold onto clouds and the threat for pcpn, especially in
the east today. The shortwave, currently over Colorado, will track
slowly east into southwestern Nebraska and northwestern Kansas
through midday. The threat for precipitation will linger in
advance of this feature with the best chances from southwestern
into northeastern portions of the forecast area. This threat will
quickly shift east this afternoon as subsidence develops on the
back side of the exiting wave. Cloud cover will be persistent
today with clearing holding off until the afternoon hours. This
will lead to a cool day across the forecast area with highs
struggling to reach the 80 degree mark. With the expected
cloudiness, temperatures were trended downward from the pvs fcst.
Skies will clear overnight behind the exiting wave and surface
high pressure will build into western Nebraska overnight. With the
clear skies and decent radiational cooling, lows will bottom out
in the lower 50s tonight. With light winds, was initially
concerned about fog potential tonight. The latest MET guidance is
favorable for fog tonight at North Platte and Broken Bow. However,
SREF probabilities and MAV guidance isn`t indicative of fog
tonight and will forgo mention in the AM fcst package.

.LONG TERM...(Thursday through Tuesday)
Issued at 343 AM CDT Wed Aug 16 2017

An upper ridge across the Western U.S. amplifies late week, placing
Nebraska in northwest flow. The ridge then flattens and progresses
onto the southern Plains over the weekend, transitioning the flow to
zonal across the central/northern Plains. A strong shortwave will
pass through the northern Plains late Monday into Tuesday. At the
surface, a series of frontal passages will result in periodic precip
chances. The evening model suite pegs the fropas early Friday, late
Saturday, and late Monday.

Kept chc PoPs Thursday evening and night as the first front
approaches. Thinking precip coverage will stay scattered at best as
low level moisture will be the limiting factor. The GFS, NAM, and
ECM are in general agreement with some moisture advection, but dew
points still struggle to reach 60F. Any convection that does develop
could be strong as soundings suggest 1000+ j/kg MUCAPE, mid level
lapse rates near 8C/km, and deep layer shear around 25 kts. Moisture
appears to be more prevalent with the fropa late Saturday with dew
points reaching the lower 60s and 500-700mb RH exceeding 70%.
Convective parameters are also stronger Saturday with CAPE pushing
2000 j/kg across southwest Neb, 0-6km shear around 30 kts, and low
level winds taking on a veering profile. The strongest system will
likely be late Monday, as the sfc front also has the support of the
mid level shortwave.

A gradual warmup will take place across western Nebraska into the
weekend as H85 flow takes on a predominately southerly direction,
except for a brief switch to north Friday night with the fropa. H85
temps reach 25C again over the weekend, and with fairly deep mixing
in the afternoon to 700mb, sfc temps should hit 90F in spots. Precip
coverage and the strong cold front will knock highs back into the
lower/mid 80s early next week. GFS and ECM in good agreement with
strong CAA in the wake of the front.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1211 PM CDT Wed Aug 16 2017

An upper level cold pool across Swrn Neb will continue to spark
showers and isolated thunderstorms this afternoon. The activity
will shift slowly east and northeast this afternoon and exit Ncntl
Neb early this evening. MVFR/IFR cigs and visibility will
accompany the showers and thunderstorms until 00z. VFR is expected
all areas from 03z this evening through 18z Thursday.


Issued at 343 AM CDT Wed Aug 16 2017

Rainfall rates per the latest radar imagery, have decreased to
under a half an inch per hour, so the flash flood watch will be
cancelled with the AM fcst package. A flash flood warning remains
in effect for Custer county where 2 to 4 inches of rain had fallen
earlier tonight. Will re-eval the situation over the next couple
of hrs and make the decision to let the FFW ride or cancel it




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