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Area forecast discussion 
National Weather Service North Platte NE
634 PM CDT Thursday Aug 27 2015

Synopsis...
issued at 330 PM CDT Thursday Aug 27 2015

Upper level trough moving across the County Warning Area this evening...in
association with a surface low pressure system. Meanwhile ridging
redeveloping across the western rockies. Partly to mostly cloudy
skies across much of the region have kept temperatures in the upper 70s to
middle 80s. A few temperatures nearing 90 across SW Nebraska were more sun prevails.

&&

Short term...(this evening through friday)
issued at 330 PM CDT Thursday Aug 27 2015

Main focus will be early tonight with the thunderstorm chances. The
low pressure system/trough pushing east across the area will be the
area to focus on. Cape is plentiful...with 2500 to 4000
j/kg...however shear is less than impressive...20 to 25 kts. The NAM
briefly increase the shear across north central to 25 to 30 kts for a
few hours around 03z. Thus severe threat is there...but not great
and is best when the shear is greatest. Precipitable waters on the increase...with
models bring values above 1.50 inches to parts of north central.
Storm motion is 10 to 15 kts so heavy rain is possible...but not
expecting flooding rains.

Overnight the storms push east with some lingering wrap around. Nose
of the nocturnal ll jet is across eastern Nebraska and western Iowa so
any mesoscale convective system will be east of the County Warning Area. Clouds and showers likely to linger
in the wrap around...however more generally and no severe threat.

Tomorrow the ridge begins to expand across the area. Lingering
clouds to help slow warmup in the east...where highs top out around
80. Middle to upper 80s expected for the western zones with more sun.

Long term...(friday night through thursday)
issued at 330 PM CDT Thursday Aug 27 2015

South flow in the low levels will bring warm/dry air from northern
New Mexico and southern Colorado to western Nebraska. This will
result in the return of Summer-like temperatures to western Nebraska
with upper 80s on Saturday and low to middle 90s Sunday. In central and
north central Nebraska where the dry trajectory is not as strong...
highs both Saturday and Sunday will be in the middle to upper 80s. It
is not until Sunday that significant low level moisture is pulled
into western Nebraska. At that time...the Theta-E ridge on the High
Plains becomes strong and precipitable water increases to more than
an inch. Even with the moisture supply increasing...there is still a
lack of a boundary or other focus for the development of more than
spotty convection in central and southwest Nebraska Saturday or
Sunday.

Turning to weather...light east wind in central and north central
Nebraska could favor fog early Saturday. However...the low level (0-
1km and boundary layer) relative humidity indicates 80-85 percent at
the highest. Of the probabilistic guidance (sref...met and mav
guidance)...only the met indicates fog. This results in considerable
uncertainty with the forecast...so we will exclude the mention of
fog for now.

As convergence develops along the Lee side trough...moisture will be
in place for thunderstorms to develop Monday afternoon. The 0-6km
shear is expected to be 20 knots or lower and the convective
potential energy less than 1000j/kg...so severe storms are not
likely.

Afternoon and evening thunderstorms are possible along the dry line
Tuesday through Thursday but severe weather is not likely.

&&

Aviation...(for the 00z tafs through 00z Friday evening)
issued at 630 PM CDT Thursday Aug 27 2015

VFR conditions are expected at klbf and kvtn through the next 24
hours. The only concerns are scattered thunderstorms across
central Nebraska this evening...which impact terminals such as
kbbw and konl through 06z. Brief heavy rain...hail...and erratic
gusty winds are possible with any thunderstorm activity. Then
overnight...some model guidance is indicating IFR visbys due to fog
after 09z. However...current satellite trends do not favor the
development of fog as an expansive area of broken middle to upper level
cloud cover will spread over much of the area. Trends will need to
be monitored tonight with adjustments made to the taf as
necessary.

&&

Lbf watches/warnings/advisories...
none.
&&

$$

Synopsis...masek
short term...masek
long term...Springer
aviation...Martin

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