411
FXUS63 KLBF 181937
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
237 PM CDT Sat May 18 2024

.KEY MESSAGES...

- An active weather pattern brings a variety of impacts,
  including severe weather and heavy rainfall Sunday through
  Tuesday.

- A limited threat for late season frost, but cannot rule out a
  localized threat following a cool down mid week.

- The pattern remains active through the week, brining the
  potential for precipitation nearly every day. Confidence on
  daily precipitation chances remains relatively low, due to
  uncertainty in exactly how the upper level pattern evolves.

&&

.SYNOPSIS...
Issued at 235 PM CDT Sat May 18 2024

Upper air analysis and satellite imagery this morning reveal an
upper level low over north central North Dakota, and a developing
shortwave over western Washington. At the surface, a low pressure
system is located over Winnipeg, Manitoba this morning, with a cold
front extending south through north central Kansas. High pressure is
observed over the Nebraska Panhandle.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 235 PM CDT Sat May 18 2024

Tonight, the stage becomes set for several days of active weather.
As surface high pressure ejects to the east, a weak surface boundary
may be the focus for some showers and thunderstorms this evening
through Sunday morning, particularly across southwest Nebraska. As
the nocturnal low level jet settles in, a plume of warm, moist air
advects into the region. While this is happening, a low
pressure system over Wyoming is expected to form and mature,
developing a warm front and cold front before it heads east.

The main forecast challenge in the short term will be how long these
showers and thunderstorms linger, which sets up two main scenarios
for Sunday evening. If the storms exit the region more quickly, as
seen in HRRR guidance, there is a greater period of daytime heating,
and as such a greater severe weather threat Sunday afternoon and
evening. These solutions are presenting decent surface based CAPE
and generally initiate storms along a line through most of the
region. On the other hand, there is some slower guidance such as the
NAM Nest, which holds the cloud cover from showers and storms a bit
longer, limiting the daytime heating. These slower solutions limit
the surface based CAPE, keeping storms more elevated in nature, and
in some cases wipes the thunderstorm threat out by tomorrow evening.

What does remain consistent is the plume of moisture ahead of the
approaching system. Additionally, forecast soundings all tend to
show a potential severe weather environment tomorrow evening, with
ample CAPE and shear profiles. If the daytime heating can erode the
capping layer, and storms can tap into the surface based layer, the
environment seems primed to produce large hail and damaging winds.
If the cap remains in place, then convection likely remains
elevated, still with large hail potential, but may end up being
hindered unless it can tap into the surface moisture.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Issued at 235 PM CDT Sat May 18 2024

Showers and thunderstorms Sunday night begin to taper off after
midnight, giving a brief dry period on Monday morning. By the
afternoon, another batch of showers and thunderstorms develops to
the west and begins to track across the forecast area. Overnight
Monday into Tuesday continues to be highlighted as the peak intensity
of this precipitation event. Current guidance suggests that forecast
precipitable water values will exceed the climatological 90th
percentile. To further back this, ensemble guidance is now
highlighting portions of north central Nebraska and the Sandhills
with a 60 percent chance of exceeding 1 inch of rain in 24 hours. As
for expected amounts, followed with the Weather Prediction Center
guidance which calls for storm total rainfall around 1 to 3 inches
across the region from tonight through early Wednesday morning.
Currently, the highest amounts are expected across the Sandhills,
but with the convective nature of the rain, locally higher amounts
are possible.

The next concern comes with a mid week cool off Wednesday morning.
The latest forecast sees temperatures trending up slightly, however
some of the lower end guidance brings mid to lower 30s across
southern portions of the Panhandle. Will continue to keep an eye on
temperature trends over the next several days, as temperatures in
the mid to lower 30s could cause some late season frost concerns
across the southern Panhandle. At this time, the chances seem
somewhat limited, but again, will be worth keeping a close eye on.

Mid week through the end of the week, the upper level pattern
remains fairly active. A series of shortwave and upper level lows
persist across the Northern Plains, with variations in the placement
of surface systems and associated rainfall. Precipitation chances
remain through the end of the week, however, it is a bit difficult
to nail down a precise timing right now. Certainly, the synoptic
forcing will be there, so it will also be worth keeping an eye on
how the upper level pattern evolves over the next several days to
more precisely time precipitation chances through the week. For now,
will continue to stick with general chances of showers and
thunderstorms through the week, however, follow on forecasts may be
able to refine the timing as models resolve the pattern later this
week.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1221 PM CDT Sat May 18 2024

VFR will continue through this evening for western and north
central Nebraska terminals as high pressure provides fair skies
and a gradually waning northerly breeze. Gusts above 20kts
should decrease to below 12 kts by 18/21z. Northerly winds
transition to east and eventually southeast/south through the
course of the evening and nighttime. Clouds will also fill in
and lower as rain showers develop early tomorrow morning. MVFR
to locally IFR ceilings are likely for southern terminals (LBF)
after sunrise, while southerly winds also strengthen with gusts
exceeding 25 kts.

&&

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

&&

$$

SYNOPSIS...Richie
SHORT TERM...Richie
LONG TERM...Richie
AVIATION...Snively