Area Forecast Discussion
Issued by NWS North Platte, NE

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600
FXUS63 KLBF 202004
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
304 PM CDT Thu Jul 20 2017

.SHORT TERM...(This evening through Friday)
Issued at 304 PM CDT Thu Jul 20 2017

The HRRR models, RAP, GFS and NAM were the basis for isolated to
perhaps scattered coverage tonight. Satellite suggests a weak
disturbance across the Tetons will spark MCS activity this
afternoon. This storm activity should translate through the Black
Hills this evening and perhaps affect nrn Neb overnight.

The situation Friday afternoon is more certain as ML-CAPE increases
to 3000-4000 J/KG. Winds aloft at 500mb are weak at 15kt initially
but a localized speed max near 40kt develops from maturing
convection east of highway 83. All indications are heavy convection
will fire and severe weather would soon follow.

A heat advisory is in place for most of the area Friday. The GFS,
HRRR exp and NAM models plus bias correction were the basis for
highs in the upper 90s to mid 100s. Blended guidance plus bias
correction indicates dew points in the 60s to lower 70s which would
support heat indices 100+. The 16C h700mb thermal ridge will move
overhead, ahead of a cold front during the afternoon, and this
should present deep vertical mixing and super adiabatic lapse rates
near the SFC. There just one problem. The models forecast midlevel
clouds which will take a few degrees off the high temperature
forecast. Given that the forecast heat waves have been too cool this
summer, the forecast for 100s will stand for now.

The 16C thermal ridge should move in late tonight and hold up lows
to the upper 60s to lower 70s for a warm start Friday morning. The
12z HRRR exp model indicates North Platte warms to 90F by 10 am and
100F by 1 pm.

.LONG TERM...(Friday night through Thursday)
Issued at 304 PM CDT Thu Jul 20 2017

Whatever convection develops Friday afternoon is expected to grow
upscale Friday night as a significant cold front moves through Swrn
Neb. All models show this except for the ECM. Temperatures at 700mb
fall back to around 10C with precipitable water around 1.5 inches
which should support upscale growth. The models show a series of
weak disturbances crossing the Cntl Rockies Saturday with moisture
still in place across Srn Neb. Precipitable water decreases to an
inch or less Saturday night marking the end of rain chances.

Dry weather is expected Sunday through Tuesday as the subtropical
upper level ridge builds back into the Wrn U.S. Hot weather may
redevelop Wednesday and Thursday as this ridge begins to move east
again. The basis of the temperature forecast a model blend of bias
corrected GFS, ECM and GEM. This produced temperatures close to the
national blended data set.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1232 PM CDT Thu Jul 20 2017

VFR is generally expected this afternoon, tonight and Friday
morning.

Despite east winds tonight, the SREF and other models show no
indicate of fog.

The HRRR models, RAP, GFS and NAM were the basis for isolated to
perhaps scattered coverage tonight. The HRRR model suggests a weak
disturbance across the Tetons will spark MCS activity this
afternoon. This storm activity should translate through the Black
Hills this evening and perhaps affect nrn Neb overnight. Storm
activity, if it develops across nrn Neb, should diminish 12-15z
Friday morning.


&&

.LBF WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from noon CDT /11 AM MDT/ to 8 PM CDT /7 PM MDT/
Friday for NEZ005>010-022-024>029-035>038-056>059-069>071.

Heat Advisory until 8 PM CDT this evening for NEZ070-071.

&&

$$

SHORT TERM...CDC
LONG TERM...CDC
AVIATION...CDC



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