666
FXUS63 KLBF 132035
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
335 PM CDT Tue Aug 13 2024

.KEY MESSAGES...

- A Slight Risk (Level 2 of 5) for severe weather across
  southwestern Nebraska this evening and tonight. Tonight`s
  primary severe threat will be severe wind gusts and locally
  heavy rainfall. Storms this evening will have the capability
  of bringing over 1 inch of rain under the heavier downpours.

- A Marginal Risk (Level 1 of 5) for all of western and north
  central Nebraska tomorrow afternoon for wind and hail.

- The week continues on with near seasonal temperatures and
  near daily rain chances through the end of the week.

&&

.SYNOPSIS...
Issued at 331 PM CDT Tue Aug 13 2024

Upper level analysis and water vapor satellite imagery reveal a low
amplitude ridge over western Nebraska, with an upper level
disturbance in the flow. At the surface, a stationary front is
observed along the Nebraska-Wyoming border. A few showers and
thunderstorms are noted on satellite and radar across the western
Nebraska Panhandle and northeastern Colorado.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 331 PM CDT Tue Aug 13 2024

As storms develop this afternoon along the front, they will continue
to trek to the east, eventually reaching western Nebraska. Better
instability exists over northeast Colorado, where CAPE values this
afternoon hover around 1000-1500 J/kg, expected to increase around
1500-2000 J/kg late this afternoon into the evening. The upper level
flow remains relatively slow, with only around 25 kts at 500 mb.
With the more marginal shear, a more multi-cellular mode is expected
for convection this evening, with the greatest severe potential
being damaging wind gusts, though some large hail cannot be ruled
out. With the increasing confidence in more organized convection
this evening, the Storm Prediction Center upgraded the Marginal Risk
for today into a Slight Risk across portions of southwest Nebraska,
generally along and south of Interstate 80.

Interestingly, PWAT values across western Nebraska are around 1.5
inches, which puts it around our 50th to 75th percentile compared to
climatology. However, the PWAT values have been increasing the past
24 hours, thanks to southeast flow pumping more moisture into the
region. Latest model guidance has been picking up on the efficient
rain processes, and multiple models have painted a stripe of higher
QPF values across southwest Nebraska, with some solutions further
north into the Sandhills. Although wind is the primary severe
weather concern with storms this evening and overnight, will need to
keep a close eye on the potential training nature of storms this
evening. With the amount of available moisture, storms this evening
could be quite efficient rain producers, with widespread
precipitation coverage across southwest Nebraska ranging from .5
inches to 1 inch. However, if the storms train, would not be
surprised to see locally higher amounts in excess of 2 inches.

On the topic of moisture, after rain and storms clear out of the
area early Wednesday morning, there is yet again a chance of patchy
fog through the morning hours. With the recent rainfall, humidity
values will be near 100 percent, with calm winds to boot. Currently
unsure on how dense the fog may get, but will need to keep a close
eye on visibilities overnight to see whether any fog headlines are
required in the morning.

As for Wednesday, a break in the cloud cover is expected late
Wednesday morning, which will help with daytime heating. With all
the recent moisture, and another shortwave in the upper level flow,
another round of severe weather may be on deck. Guidance suggests
the possibility of CAPE in excess of 2000 J/kg across central
Nebraska, however, there is question on how far west this will
extend. Again, upper level flow is not overly robust, with 500 mb
winds around 30 kts. Forecast soundings appear supportive of large
hail in stronger cells, and cannot rule out potential for severe
wind gusts. As of now, the ingredients for more organized severe
weather appear to be lining up over eastern Nebraska. However, as
storms initiate over central and north central Nebraska, there may
be a window for potentially severe thunderstorms tomorrow afternoon
and evening. For now, the Storm Prediction Center has placed a
Marginal Risk for severe weather across all of western and north
central Nebraska for Wednesday.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 331 PM CDT Tue Aug 13 2024

An upper level low will attempt to flatten the low amplitude ridge
over western Nebraska Wednesday afternoon, bringing more zonal flow
on Wednesday night and Thursday, before another ridge is expected on
Friday. A few shortwaves are expected to track through the upper
level flow, and with those shortwaves, at least slight chances of
showers and thunderstorms through the end of the week. At this time,
the severe potential of any thunderstorms remains uncertain. By the
weekend, precipitation chances are expected to drop below 20
percent, but will need to see how guidance handles the upper level
flow. There were already deviations setting up in spaghetti plots by
the weekend, so will need to keep an eye on model trends to see how
these deviations resolve. Also of note, will be the return to
seasonal temperatures, generally highs in the 80s, starting as early
as Wednesday.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1227 PM CDT Tue Aug 13 2024

Areas of MVFR/IFR/local LIFR in low or very low ceilings across
wrn Nebraska will gradually improve to MVFR by around 21z this
afternoon. A return to IFR/LIFR in low/very low ceilings and
vsbys is expected to commence around 03z this evening and last
until 15z or later Wednesday morning. It`s worth noting an
eastward moving cold front Wednesday morning will improve flight
conditions from west to east.

Aviators will also have to negotiate scattered to numerous
thunderstorms from 01z this evening through 12z Wednesday
morning, generally affecting areas along and south of highway 2.
This flight concern is associated with a UA disturbance moving
east northeast out of Colorado this afternoon.

&&

.LBF WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

SYNOPSIS...Richie
SHORT TERM...Richie
LONG TERM...Richie
AVIATION...CDC