226
FXUS63 KLBF 020541
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
1241 AM CDT Thu May 2 2024

.KEY MESSAGES...

- Strong to severe storms across central and southwestern
  Nebraska late this evening into the early overnight hours.
  Primary threat is large hail, however, damaging wind gusts
  (60+ mph) cannot be ruled out.

- Brief break from precipitation on Thursday with mild
  temperatures in the 60s ahead of a second system expected to
  impact the area on Friday which will bring the potential for
  strong to severe thunderstorms and locally heavy rainfall.

- Dry conditions return Saturday and Sunday. However, unsettled
  weather conditions continue next week with additional chances
  for precipitation and a gradual warming trend bringing high
  temperatures back to near or slightly above normal. The severe
  threat remains uncertain at this time.

&&

.SYNOPSIS...
Issued at 331 PM CDT Wed May 1 2024

Recent GOES-16 WV imagery and RAP 500-mb analysis showed a
persistent low pressure system centered across southern
Alberta/Saskatchewan with a trough extending southwest into the
Great Basin and Desert Southwest. An upper-level shortwave was
ejecting off the parent low pressure system, across the Upper
Midwest/Great Lakes. A more robust southern stream trough was
traversing eastward out of the northern and central Rockies.
Southwesterly flow aloft has continued to increase across the
central and southwestern Plains. At the surface, high pressure
was noted across the Midwest into portions of the northern
Plains. Surface low pressure was apparent across the
Texas/Oklahoma Panhandle with a dryline extending southwestward
into the Upper Rio Grande in Texas and a warm front was tracking
northeastward across central Kansas. Isentropic lift on the
northwest periphery of the surface high pressure and multiple
weak upper-level shortwaves tracking through has resulted in
continued scattered light rain showers across north and north
central Nebraska. As the surface high pressure tracks
northeastward, this activity should exit the area in the next
few hours. Some light to moderate rain showers have also
developed across the northwest Sandhills this afternoon in
vicinity of an inverted surface trough and weak cold front
extending across eastern Wyoming into northwest South Dakota.
However, the main focus for rain showers and a few thunderstorms
this evening into the overnight period will occur as an
inverted surface trough extends northeastward out of the
southern Plains into the area. As of 3 PM CT, temperatures
ranged from 51 degrees at Gordon to 61 degrees at Broken Bow.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 331 PM CDT Wed May 1 2024

Tonight...Upper-level lift will increase over the area this evening
into tonight as the shortwave ejects across the local area. A
complex of storms appears to develop in vicinity of the inverted
trough across southwest into central Nebraska, primarily after 00Z.
This complex of storms will move from west to east across the area,
exiting the area by ~09Z tonight as the system tracks northeast into
the Midwest region. While the main area for severe weather resides
further south and east of the area, continuing to see the potential
of a brief window for isolated strong to severe storms across
portions of central and southwest Nebraska. Elevated CAPE and
steep lapse rates aloft will create an environment that will be
supportive of large hail and gusty winds for the cores that are
able to maintain themselves. The area of concern will be along
and south of a SW-NE line from Chappell to Burwell with the
greatest threat across Frontier County where the greatest
moisture and forcing will set up. Outside of the severe threat,
locally heavy rainfall is possible across portions of the
southwest Nebraska into northeastern Nebraska. Some uncertainty
remains on the placement of heaviest rainfall due to recent CAMs
continuing to waver back and forth. However, anticipate this to
occur where the strongest ascent is as the low-level jet (LLJ)
noses into the southeastern portion of the state, intersecting
the front and MUCAPE >1,000 J/kg. Current thinking is the
greatest threat for rainfall amounts of 1 to 2" will reside
southeast of a SW-NE line from Hayes Center to Broken Bow to
O`Neill. While the threat for flash flooding is low, this will
be the area most favorable for heavy rainfall with the
possibility of lowland flooding.

Thursday and Thursday Night...Outside of the potential for lingering
showers and embedded thunderstorms through the early morning hours
on Thursday across north central Nebraska, quieter conditions
set up across the area during the day. A strong surge of drier
air will push into the area behind the exiting system with
surface high pressure centering over central Nebraska. West
winds will strengthen as a result with frequent gusts of 25 to
30 miles per hour throughout the day. These gusty winds combined
with afternoon humidities bottoming out near 20 percent will
introduce elevated fire weather concerns for portions of the
area, primarily across the Panhandle into the Sandhills (Fire
Weather Zones 204 and 210). Unseasonably cool temperatures are
expected Thursday, ranging from the upper 50s across northwest
Nebraska to upper 60s across southwest. Chilly air will begin to
filter in from the northwest overnight with lows ranging from
30 degrees across northwest Nebraska to 40 degrees across
southwest.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 331 PM CDT Wed May 1 2024

On Friday, the main upper-level low pressure system will finally
begin to move northeastward into Ontario with a trough extending
into the northern Plains. At the same time, associated surface low
pressure will deepen across Ontario with a strong, attendant cold
front advancing out of the northwest across the local area through
the day on Friday. A modest 250-mb jet maxima of 100+ kts will
orient southwest to northeast from southern Wyoming through southern
Minnesota, aiding in upper-level divergence. Robust
frontogenetical forcing behind the front resulting in increased
cloudiness and a threat for precipitation across much of the
area Friday and Friday night. While the greatest moisture and
instability will reside further south of the area, the robust
forcing combined with steep lapse rates will bring create an
environment supportive of severe storms capable of producing
large hail and damaging winds for areas generally south of
Highway 2. Convection appears to initiate off the Front Range,
eventually congealing into a Mesoscale Convective System (MCS)
as it tracks eastward across southern Nebraska. With the
potential for the MCS setup, localized flooding will be a
concern with current models highlighting modest QPF of 1"+
across portions of southwest Nebraska. Recent rainfall over the
last few days has resulted in saturated ground across much of
the aforementioned area which will lead to additional concerns
for localized flooding. This is highlighted by the Weather
Prediction Center (WPC) Day 3 Marginal Risk of Excessive
Rainfall Outlook (ERO) across the southern third of the state of
Nebraska. Will continue to monitor the severe potential as CAMs
get into range and get a better handle on the track of the low
and the environment.

As the main system departs eastward early Saturday morning, a return
to dry conditions is expected during the day Saturday into Sunday as
the upper-level ridge nudges eastward into the Plains. Mild
temperatures in the 60s are expected on Saturday, warming into the
mid 60s to mid 70s on Sunday. These dry and relatively quiet
conditions will be rather short-lived as a strong upper-level
low pressure system moving in from the west coast, through the
Rockies and into the Plains by the start of next week. This
system is very dynamic and may bring a threat for severe
thunderstorms to Nebraska on Monday. However timing, location,
and degree of the severe threat is uncertain at this time. With
the potential for an active period for early next week, make
sure to keep up to date with the latest forecasts as details get
ironed out with subsequent forecasts.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1240 AM CDT Thu May 2 2024

Poor flight conditions early, then improving to VFR Thursday
morning with potential for gusty winds.

Low pressure passing by to our southeast will pull the lingering
precipitation eastward with it. KVTN is already on the backside
of the precipitation and expect KLBF will also be in about
another 2 hours. However as the precipitation ends, the boundary
layer will stratify and low clouds/fog will develop with
IFR/LIFR conditions expected at TAF sites thorugh daybreak,
though improvement will be rapid with a return to VFR later
Thursday morning. VFR conditions will then persist through the
end of the valid period.

Winds will generally be light overnight, then become
westerly/northwesterly by midmorning with gusty conditions
developing. There is a lot of wind at the top of the mixed layer
that may reach the surface if mixing is deep enough, so will be
watching closely to see how the clearing and heating develop
this morning. For now will keep gusts at 30kt for KLBF and 35kt
at KVTN this afternoon, but if mixing is robust and allows winds
to reach maximum potential, could be looking at gusts 10kt or
more above the current TAF values this afternoon especially at
KVTN.

&&

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

&&

$$

SYNOPSIS...Viken
SHORT TERM...Viken
LONG TERM...Viken
AVIATION...MBS