360
FXUS63 KLBF 051922
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
222 PM CDT Fri Jul 5 2024

.KEY MESSAGES...

- A couple waves of thunderstorms are possible Saturday through early
  Sunday with strong to severe activity possible for much of
  Saturday.

- More widespread rain and thunderstorms will accompany a
  passing cool front Sunday, which will bring to threat of
  locally heavy rain in addition to holding afternoon
  temperatures in the 70s.

- Overall weather pattern next week will be dominated by strong
  upstream ridging and highly amplified northwesterly flow
  locally. This suggests fairly dry weather and moderating
  temperatures.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 221 PM CDT Fri Jul 5 2024

Early morning satellite analysis shows a modest disturbance tracking
across southwest Nebraska. This is producing enough lift via modest
h7 convergence within a weakly unstable environment to drive
isolated showers. Further satellite analysis depicts some convective
elements to this though lightning has not recently been observed
with this activity. On a broader scope...large scale ridging remains
anchored across the West Coast with departing trough diving east-
southeast across the Great Lakes. Slight northwesterly flow remains
in place across much of the central and northern Plains and will
dominate the upper-level pattern through the valid forecast period.

Aforementioned mid-level wave producing light showers across the
southwest will continue to shift east-southeast through early
afternoon. Have maintained Chance (< 35%) PoPs across our southern
three counties with anticipation that some strengthening may occur
as temperatures climb and instability builds. Even so, MUCAPE values
peak around 500 j/kg in the area within weak shear (< 30 knots) so
no severe weather is expected. This may allow more precipitation to
reach the ground, however, as a few stronger updrafts may develop
with spotty QPF amounts indicated by various hi-res guidance. Behind
this, northwesterly low-level flow continues to reinforce a fairly
dry airmass in place. Precipitable water values across much of
Nebraska remain below normal with latest NAM guidance suggesting
values nearing 50% of normal. With steady northwest winds,
mechanical mixing should support gusty winds and deeply mixed
boundary layers. Signs of this are already showing up as of 17z with
an expansive cu field across the Sandhills. Can`t rule out a widely
isolated shower or weak thunderstorm develop this afternoon and will
cover this potential with a 15% PoP (Slight Chance). Friday morning
HREF guidance shows this potential with fairly aggressive QPF
painting across the area. While this is likely overdone compared to
what will actually occur, it speaks to the potential of development
that may occur anywhere in short order. Activity, should any form,
will likely dissipate with loss of daytime heating this evening.


Saturday...Winds quickly veer this evening as weak low pressure
develops over southeast Wyoming in response to approaching Alberta
Clipper. Timing of this feature makes for an interesting forecast as
greatest upper-level dynamics including associated height falls and
DCVA favor the morning hours Saturday. With the main surface low
progged to slide west of the area, southerly flow ahead of this will
draw in theta-e rich air with increasing instability through the
early morning hours. Eventually, this theta-e nose will intersect
the main h5 trough across western Nebraska with decreasing
LIs/increasing MLCAPE reaching -4 to -8 degC/1500-2500 j/kg ranges
respectively. Compressing flow aloft with the approaching h5 trough
axis will yield increasing mid-level flow which in turn will
strengthen deep layer shear. By sunrise Saturday, 0-6km BWD values
will exceed 30 knots across the whole of the area and peak around 40
knots for the Sandhills in closer proximity to the main mid-level
speed max. All this to say that ongoing activity from the northwest
will encounter a more favorable environment and increase the threat
for strong to severe thunderstorms in the morning hours. While
questions linger about how early storms can become surface based,
steep lapse rates within strong unidirectional flow from the level
to MU parcel through the mid-levels supports a threat for large hail
with isolated 2"+ hail possible in supercellular structures. Latest
SPC Day 2 outlook highlights much of the area in a Slight Risk
(level 2 of 5) and am in agreement with this placement as well as
the staggering of greatest wind threat further south and east due to
the previously mentioned uncertainty of if and when storms can
become surface based. Renewed thunderstorm development appears
probable during the afternoon along the trailing surface
trough/instability gradient but expectations are for this activity
to have shifted south and east of the forecast area. Thunderstorm
activity should depart the area by early evening and this idea is
supported by quickly decreasing SREF/HREF precipitation
probabilities and raw CAM guidance. Temperatures behind convection
should recover well with afternoon highs in the upper 70s to middle
80s, the coolest values expected for central Nebraska which should
see a later end to thunderstorms.

Saturday Night through Sunday Night...behind departing storms and
after temperatures have somewhat recovered, southeasterly flow will
redevelop which will help prevent boundary layer moisture from
scouring out. As such, with steep lapse rates aloft remaining
steadfast across our western zones, a moderately unstable atmosphere
will redevelop during the afternoon. A progressive cool front will
invade the area and encounter the increased instability with fairly
focused, strong low-level lift. With rain and thunderstorms possible
and the environment conducive for organized convection, cannot rule
out another overnight threat for strong to potentially severe
thunderstorms. Given the timing of the day, expecting the main
threat to be elevated hail storms with a few 1" hail reports
possible. With precipitable water values having likely recovered
ahead of the front, am a little concerned about the prospect of
locally heavy rainfall. Synoptic models, notably the GFS/ECWMF are a
little more pessimistic about the potential while the CAMs are much
more bullish. Generally speaking, will side with the CAM guidance
with support from SREF output suggesting the potential for wetting
rains in the area. Whether this winds up being a widespread issue
remains in question as individual NWP solutions only show a few more
isolated stronger cores versus widespread such as with a MCS. NBM
90th percentile QPF values show values nearing 0.50" for much of the
area through the day Sunday. Latest QPF from the WPC shows slight
increases locally and would expect to see these continue to trend
upwards should confidence in solutions such as the NAM become more
certain. Similar to Saturday, timing will favor Sunday morning
through early afternoon so the majority of activity should exit the
area by early evening. Temperatures will likely be slightly cooler
in the post frontal airmass with highs remaining in the 70s for all.
Northerly flow will persist into the evening hours as high pressure
settles into the central Rockies. This will be the beginning of
another fairly quiet period as decreasing moisture due to incoming
dry air will help stymie precipitation chances for the extended
period. Lows Sunday night will settle to below normal values due to
light northerly winds and clearing skies.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
Issued at 221 PM CDT Fri Jul 5 2024

Monday...perhaps the best potential for precipitation in the long
term forecast prior to high pressure aloft moving in. Elongated
trough axis will remain stagnant from the upper Mississippi Valley
down through the central Plains. Even though the main trough axis
will likely settle east of the area, enough low-level lapse rates
may induce a few isolated showers across central Nebraska. Forecast
soundings depict reasonable mid-level moisture and lapse rates to
support isolated development, similar to what is observed today. For
now, the NBM populates a dry forecast but as the day draw nearer,
would not be surprised to see a need to introduce low-end PoPs to
the forecast.

Tuesday and beyond...long term will be characterized by increasing
ridging aloft working in from the west with highly amplified
northwesterly flow. This plays out typically with increasing
temperatures and limited precipitation chances. Ridge axis arrives
into the Great Basin by mid-week with building high pressure aloft
finally reaching into the central Plains by late Thursday. While
most of the anomalous heat will be focused west of the Rockies,
temperatures will still likely climb through next week with near
steady 1-3 degF day-over-day increases in NBM 25th, 50th, and 75th
percentile values. Meanwhile after Tuesday, QPF probabilities nearly
flatline with exceedance probabilities of only 0.01" falling to less
than 20% each day Wednesday through Saturday. Individual ensembles
such as the EPS and GEFS do not inspire much more hope with only a
smattering of foundational members suggesting measureable
precipitations. Signals increase somewhat by early the following
week but at this range, timing is murky at best. For now, expect the
dog days of summer to return by late next week with highs returning
to above normal values and precipitation chances to be few and far
between.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 103 PM CDT Fri Jul 5 2024


Mostly quiet aviation conditions are expected through Saturday
morning. Some isolated showers are possible across the region
tonight, however, confidence remains too low in timing, development,
and location to put it into the prevailing forecast at this time.
Ceilings will begin to lower by mid morning in advance of the next
frontal system which will bring scattered showers and thunderstorms
by Saturday afternoon.

&&

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

&&

$$

SHORT TERM...NMJ
LONG TERM...NMJ
AVIATION...Kulik