717
FXUS63 KLBF 120608
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
108 AM CDT Wed Jun 12 2024

.KEY MESSAGES...

- Growing concerns for heat on Wednesday with forecast highs in
  the mid 90s through low 100s expected. Current heat indices
  remain below Advisory criteria.

- Recurring rain and thunderstorm chances Wednesday through
  Saturday with the greatest potential being late Friday into
  early Saturday. An isolated strong storm or two will be
  possible Wednesday and Thursday with the threat becoming more
  uncertain Friday into Saturday.

- Temperatures will favor near to above normal values in the
  extended.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 346 PM CDT Tue Jun 11 2024

General zonal flow remains prevalent across the central CONUS as low-
amplitude ridging sets up across the Desert Southwest. Troughing
continues to hang out across the Northeast CONUS with another system
tracking into the upper Mississippi Valley and far southern Canada
and the next system approaching the Pacific northwest as of Tuesday
afternoon. At the surface, broad high pressure was situated in the
Ohio Valley with a mid-level disturbance off the Baja of California
that will come into play later on in the forecast.

Today, a warm front will lift north through the area as modest low
pressure develops across Wyoming. This warm front and moisture
advection has led to a few isolated light rain showers across
portions of the Sandhills. What few radar echoes that did crop up
did not manage to last long and likely didn`t produce much more than
virga as surface dew point depressions approach 20 to 25 degrees
across the area. This warm front should lift north through the day
and exit into South Dakota by late tonight. Continued warm air
advection behind this front will potentially lead to low-end
precipitation chances. With the nose of the developing low-level jet
focusing near if not north of the Nebraska/South Dakota state line,
expecting most if not all locations to remain dry. Lows tonight will
only fall into the upper 50s to lower 60s or nearly 10 degF above
normal.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 346 PM CDT Tue Jun 11 2024

Wednesday...The hottest day of the weekend and likely to have at
least some moderate heat concerns. Surface low will track east
across South Dakota through the early morning hours. This will draw
a surface trough extending from the NE/SD border invof Keya Paha
County south through MCK and into far western Kansas. Ahead of this,
strong southerly flow will continue to reinforce rich low-level
moisture with a fairly unimpeded Gulf of Mexico tap at least early
in the day. Behind this, west-northwesterly downsloping flow will
establish itself across the western forecast area in a fairly dry
environment. This will not only help promote compressional warming
but also deeper mixing into the heart of the thermal ridge where h85
and h7 temperatures will both exceed the 90th percentile. Have
boosted highs slightly as a result, with a few locations now forecast
to break the century mark across far southwest Nebraska. While heat
will be of great concern given ongoing outdoor activities, limiting
overall concern will be the relatively limited overlap of hottest
temperatures and greatest low-level humidity. Because of that,
forecast heat indices fall short of Advisory (100 degF) criteria
though upper-90s should be prolific for areas south of Interstate 80
and east of Highway 183. Back east in the richer moisture quality,
the Storm Prediction Center (SPC) maintains a Marginal Risk (Level 1
of 5) for areas east of Highway 183. A moderately unstable
atmosphere will be in place as MLCAPE values range from 1500-2500
j/kg in a strongly sheared environment, the forcing necessary to
overcome strong capping is hard to find. This is largely due to lack
of an appreciable shortwave aloft within an environment with steady
h5 height rises and such anomalous warmth in the h85 to h7 layer. It
doesn`t appear that capping fully erodes in the immediate area and
with little in the way of surface convergence due to veered surface
flow in the warm sector, anticipating dry conditions to largely win
out.

Thursday into Friday...recent trends have decreased heat concerns
for Thursday. An early morning cool front will drop south out of the
northern Plains. This is being propelled as high pressure shifts out
of western Canada. Though h5 heights remain at anomalous levels,
surface flow shifting to northeast and eventually easterly is not
supportive of intense heat. Temperatures at h85 look to fall 5 to 10
degC across the board. Temperatures will still push the upper 80s to
low 90s in our furthest south counties but should remain in the mid
80s or cooler elsewhere. As the surface front stalls south of the
area, it`ll provide the focus for afternoon rain and thunderstorm
chances. This will be aided by eventual easterly upslope flow. Where
this boundary ends up will play a large role in where thunderstorms
develop and subsequently if they were to impact portions of western
Nebraska. For now, will maintain the inherited Slight Chance to
Chance (< 35%) PoPs from the NBM blend. Various deterministic
solutions show limited coverage of any precipitation chances and
only the GEFS appears to match the coverage and magnitude of these
PoPs so confidence remains low. The SPC maintains a Marginal Risk
(Level 1 of 5) for the Highway 23 corridor and south. Believe this
is adequate given MLCAPE values surpassing 1500 j/kg and 0-6km BWD
of 40 knots. Strong capping will likely need to be overcome and this
should limit more expansive coverage. An increasing low-level jet
late Thursday should provide the focus for more rain and
thunderstorms across our far northwest zones. The nose of this
feature will track west to east across much of western and central
Nebraska taking with it increased PoPs (up to 40%) as it does. The
previously mentioned system off the Baja of California will, by this
time, have reinserted itself into the flow aloft and begin to exit
the Desert Southwest into the Great Basin by early Friday. Trends
have been to slow ejection slightly but overall timing still favors
late Friday into Saturday. Greatest height falls/DCVA will favor
peak heating. Flow aloft will support a severe threat but casting
some uncertainty is the anticipated narrow corridor of any warm
sector. Deterministic solutions depict a fairly small swath of 60+
degF dew points but all output shows this nosing into southwest
Nebraska. While the SPC shows "Predictability too Low", thoughts are
we should see at least an isolated severe threat materialize during
the late afternoon and evening with large hail and damaging winds
the main concerns. Convection will continue to blossom into the
overnight as greater forcing arrives from the southwest. PoPs peak
around 70% (Likely categorical) but given signals from NBM, GEFS,
and EPS guidance believe these could increase further. Probabilities
of exceeding 0.10" QPF exceed 60% for all locations in the County
Warning Area and latest NBM probabilities for exceeding 0.25" at
almost 50%. This supports a fairly widespread wetting rain event
with localized higher amounts due to convection. Daytime highs
Friday are likely to remain in the 80s for all.

Saturday into early next week...height falls peak around the middle
of the day with fairly widespread rain and thunderstorms persisting
into the first half of the day. This should quickly wane as the
trough axis clears and shortwave ridging builds in behind. Ensemble
guidance shows a quick east progression of greatest precipitation
potential through the day Saturday and into early Sunday.
Deterministic solutions suggest airmass recovery allowing for
additional thunderstorm development across central Nebraska but
confidence in this is low at this time. Overall, low amplitude
southwesterly flow appears probable with increasing amplitude
possible as another mid-level disturbance approaches the West Coast.
The southwesterly flow will support low-level southerly flow which
should prolong seasonable to slightly above normal temperatures in
the extended. More precise timing of the next big disturbance early
next week is greatly in doubt at the current time as evolution
varies greatly across NWP output. For now, the day-to-day Chance (up
to 40%) represent current thinking fairly well.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1253 AM CDT Wed Jun 12 2024

Low-level wind shear will be of concern early this morning as a
southwesterly low-level jet be present just off the surface.
Otherwise, a weak wind shift will cross the area today. South
winds will shift to the northwest as it crosses the area. A few
thunderstorms may develop along the wind shift line, but that
appears to occur across eastern Nebraska later this afternoon.
VFR conditions will prevail today through tonight across all of
the area.

&&

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

&&

$$

SHORT TERM...NMJ
LONG TERM...NMJ
AVIATION...Taylor