Area Forecast Discussion
Issued by NWS North Platte, NE

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FXUS63 KLBF 180503 AAB
AFDLBF

Area Forecast Discussion...UPDATED
National Weather Service North Platte NE
1203 AM CDT THU AUG 18 2016

...Updated Aviation section...

.SYNOPSIS...
Issued at 333 PM CDT Wed Aug 17 2016

H5 analysis this morning had a low amplitude ridge in
the Rockies. This was undercut by a shortwave over the four corners.
A secondary disturbance was noted over central California. Across
Canada, a nice upper level low was noted over eastern portions of
the Northwest Territories of Canada. Upstream of this feature a
tandem of PV anomalies were noted: the first over northeastern
British Columbia and a second over the southwestern Yukon. Across
the high plains and central CONUS: Abundant convection was
developing over the central Rockies this afternoon underneath the H5
shortwave, which as of mid afternoon, was located just north of
Alamosa Colorado. At the surface: A cold front was beginning to
push into northwestern Montana this afternoon. South of this
feature,a trough of low pressure extended south southeast into
Wyoming and far northern Colorado. Skies were mostly clear this
afternoon across western and north central Nebraska. Mid afternoon
temperatures ranged from 87 at Ainsworth, to 93 at Thedford.

&&

.SHORT TERM...(This evening through Thursday)
Issued at 333 PM CDT Wed Aug 17 2016

One more warm August day in store before significant changes arrive
to the area, see long term discussion. A couple areas of concern for
isolated thunderstorms early tonight. One area is across far
southwest Nebraska as storms move east off the higher terrain to the
west. A second area across north central as warm and humid area has
eroded most of the cap. Although forcing is weak but like last
evening a storm or two cannot be ruled out. Overnight the confidence
grows that the area will be dry. The past couple of mornings some
patchy fog has developed in the Platte River valley and into
portions of Custer county, so have added some patchy fog for a few
hours in the morning.

The eyes focus on the last warm day of this warm spell. Highs into
the lower and mid 90s warmest just ahead of the approaching cold
front due to compressional heating. Dry conditions over the heart of
the CWA will combine with the strongest winds for fire weather
concerns. See fire discussion for more. By mid afternoon a cold
front will enter NW Nebraska. This will bring a chance for
thunderstorms.

.LONG TERM...(Thursday night through Wednesday)
Issued at 333 PM CDT Wed Aug 17 2016

mid term...Thursday night through Saturday: In the mid term,
precipitation chances will be the main forecast concern. For
Thursday night: A cold front will track across western Nebraska and
will clear the forecast area by 12Z. Behind the front, a nice lead
shortwave will track from eastern Wyoming into South Dakota and
northern Nebraska overnight Thursday Night. Decent mid level lift
will develop in advance of the shortwave leading to precipitation
across the area. Lift and dynamics continues to favor the highest
pops across the northern CWA and little change was made to the
inherited forecast as this was handled well. On Friday, the front
will slow down across central Nebraska. As it moves east during the
day on Friday into a nice area of rich boundary layer moisture,
showers and thunderstorms will develop across eastern portions of
the forecast area. This is in addition to any residual showers in
behind the exiting front Friday morning. CAPE ahead of the front
Friday afternoon is impressive from south central into east central
Nebraska with CAPE`s in excess of 4000 J/KG. Wind shear is marginal
initially but increases into the afternoon hours so the severe
threat appears viable ATTM over eastern Nebraska. Based on the
latest NAM solution, the severe threat for western and north central
Nebraska will be very limited Friday with the front being east of
the forecast area by midday. For Friday night into Saturday the main
shortwave trough will push across the northern plains. The models
this morning did have some timing issues with this feature as the
GFS/EC solns are faster than the NAM solution. ATTM...feel confident
about precipitation chances for friday night and have some likely
pops in northern Nebraska. However, for saturday, have limited pops
to the 20 to 30 percent range given the model timing differences.
Highs will be cool on Friday and Saturday with readings mainly in
the 70s.

long term...Saturday night through Wednesday: The upper level trough
is expected to clear the northern plains Saturday night into early
Sunday. Low level moisture will be forced well south of the area
for the next couple of days resulting in dry conditions across
western and north central Nebraska. The next chance for
precipitation will creep back into the forecast Tuesday night into
Wednesday as moisture returns north into the high plains. The
northern stream will become active as well as a nice northern stream
trough of low pressure tracks from the northern Rockies into the
northern plains Tuesday night into Wednesday. With the return
southerly flow...temperatures will rebound back into the 80s.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1203 PM CDT Wed Aug 17 2016

Conditions are currently quiet across western and north central
NE. VFR prevail across the forecast area with some high clouds
present across portions of north central and central NE from
earlier convection. No more showers or thunderstorms are
anticipated the rest of tonight. Patchy fog may develop across
portions of Lincoln and Custer counties this morning, specifically
along the river valleys and climo prone areas. Current thinking
is a brief period with visibility reduced to MVFR.

Tomorrow...A front roughly oriented SW-NE is expected to enter the
far northwest portion of the forecast area by early afternoon.
Latest guidance and trends suggest front will bisect the center
of the forecast area, south and east of KVTN, roughly by late
evening. Winds will shift primarily from SSW to N with its
passage. Slight chances for showers and thunderstorms in the
afternoon north and west of a line from Ogallala to Ainsworth --
with the greater chances roughly north and west of a line from
Lisco-Bingham-Nenzel. Some strong or severe thunderstorms are
possible in the afternoon and evening.

&&

.FIRE WEATHER...
Issued at 333 PM CDT Wed Aug 17 2016

A cold front will approach the area late in the day. Ahead of the
front compressional heating will push temps into the mid 90s. The
dry line will surge east with areas in the lower 50s and even mid to
upper 40s. This combination will produce rh values near critical 15
percent. In addition to the low rh values will be gusty southerly
winds. Winds of 15 to 25 with higher gusts are likely. The cold
front will slide across the area overnight with winds becoming
northerly and will also see a chance for rain post frontal.

&&

.LBF Watches/Warnings/Advisories...
Fire Weather Watch from Thursday afternoon through Thursday
evening for NEZ206-208-210.

&&

$$

SYNOPSIS...Buttler
SHORT TERM...Masek
LONG TERM...Buttler
AVIATION...ET
FIRE WEATHER...Masek



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