Area Forecast Discussion
Issued by NWS North Platte, NE

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989
FXUS63 KLBF 210432
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
1132 PM CDT WED JUL 20 2016

.SYNOPSIS...
Issued at 319 PM CDT Wed Jul 20 2016

H5 analysis this morning as a broad area of high
pressure centered over the Ozarks. This feature extends from the
desert southwest east to the southeastern CONUS. Ridging extended
north of this feature into North Dakota and northern Minnesota. A
tandem of low pressure troughs were present east and west of the
ridge. One was oriented along the eastern seaboard, while the
western trough extended from southern British Columbia, southwest
into the eastern Pacific Ocean. On the northern periphery of the
upper level high, numerous shortwaves were noted with one over Iowa,
a second over western Colorado, a third over southern Arizona and a
fourth over northern Mexico about 200 to 400 miles south of El Paso
Texas. No significant height rises or falls were noted across the
CONUS this morning, so the upper level pattern should remain
stagnant for the next 12 to 24 hours. At the surface, low pressure
was located northwest of Pierre South Dakota with a surface trough
extending south southwest into west central Nebraska, while a
dryline was present across the Nebraska Panhandle. Temperatures were
very hot this afternoon with readings ranging from 89 at Broken Bow
to 99 at Valentine.

&&

.UPDATE...
Issued at 1106 PM CDT Wed Jul 20 2016

The cluster of thunderstorms across Yuma County CO may affect
Swrn Neb 05z-10z. These storms are elevated and may be operating
in the elevated mixed layer from 700-500mb. Isolated showers and
thunderstorms are in place across Swrn Neb for a few hours
overnight.

&&

.SHORT TERM...(This evening through Thursday)
Issued at 319 PM CDT Wed Jul 20 2016

Hot and humid conditions will continue along and east of highway 83
Thursday, with hot but a little drier air to the west of highway 83.
Will continue the heat advisories and warnings.

A surface trough of low pressure will meander slowly east and
roughly extend from Valentine to Imperial by late Thursday
afternoon. Convective temperatures are reached along and near the
boundary, so expecting a few thunderstorms to develop. Instability
is decent but overall shear is weak. If any storm becomes strong it
could produce gusty winds but little threat of hail due to high
freezing levels and warm air aloft.

With the surface trough in the area expect little in the way of
wind, so no relief from the heat from any type of breeze Thursday.
Highs most areas will reach near 100 degrees, with heat index
readings over 105 degrees across parts of central and north central
Nebraska.

.LONG TERM...(Thursday night through Wednesday)
Issued at 319 PM CDT Wed Jul 20 2016

In the mid range, temperatures and precipitation chances
will be the main forecast challenges. For Thursday night, the
shortwave currently over southwestern Colorado, will cross northern
Colorado, entering southwestern Wyoming Thursday afternoon. Strong
surface heating will be underway across western Nebraska INVOF of a
surface boundary by late afternoon and will lead to a well mixed
layer and little or no CIN across the panhandle and far western
Nebraska. Thunderstorms should develop INVOF the surface trough and
lift east into the evening hours. Inherited forecast did have a
mention of isolated thunderstorms Thursday Night and these will
continue as is. Some modifications were made to timing, mainly to
slow the eastward progression of the storms based on the latest
model solutions. Did keep pops isolated however, as upper level
dynamics are weak and there is still some timing differences within
the GFS and NAM12 solutions. As for the threat of severe storms,
deep layer shear is weak tomorrow evening, on the order of 10 to 20
kts. Any severe threat would arise from gusty winds given the weak
shear and inverted V forecast soundings. On Friday, overnight
convection from Thursday night will force a surface boundary south
to near the KS/NEBR border. During the day Friday, both the NAM and
GFS solns lift this boundary north as a warm front, however the NAM
is much slower and results in cooler highs for friday compared to
the warmer GFS solution. Decided to trend highs toward the warmer
MAV guidance, which better represents the current inherited
forecast. However, highs may need to be trended downward for Friday
if the NAM12 model continues to hold onto easterly low level winds
as this morning`s run does. The threat for thunderstorms will
continue late Friday afternoon into Friday night as another upper
level disturbance lifts into the forecast area from the southwest.
Thunderstorms will be possible across the entire forecast area
Friday/Friday night with the threat shifting into the central and
eastern CWA for Saturday. This is a result of a cold front which
will track across the forecast area Saturday afternoon.

Beyond Saturday: The front will be forced into Kansas Saturday
night/Sunday with pcpn chances mainly south of the forecast area.
The ridge will continue to break down next week as high pressure
aloft develops over the Carolinas and the southwestern CONUS. This
will result in a zonal pattern across the central and northern
plains with cooler highs in the 80s and an increased threat for
thunderstorms during the afternoon and evening hours.

&&

.AVIATION...(For the 06Z TAFS through 06Z Thursday night)
Issued at 1132 PM CDT Wed Jul 20 2016

The isolated cluster of thunderstorms approaching Swrn Neb may
affect the region for a few hours overnight.

Isolated to scattered thunderstorms coverage is expected across
Wrn and Ncntl Neb Thursday afternoon from 20z onward. Storm
activity is expected to become scattered across Ncntl Neb east of
Highway 83. A general southward progression of storm coverage and
motion is expected across Ncntl Neb. Otherwise...VFR is expected.

&&

.LBF Watches/Warnings/Advisories...
Heat Advisory until 7 PM CDT /6 PM MDT/ Friday for NEZ004-022-
023-035-056>058-069-070.

Excessive Heat Warning until 7 PM CDT /6 PM MDT/ Friday for
NEZ005>010-024>029-036>038-059-071-094.

&&

$$

UPDATE...CDC
SYNOPSIS...Buttler
SHORT TERM...Taylor
LONG TERM...Buttler
AVIATION...CDC



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