789
FXUS63 KLBF 110615
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
115 AM CDT Tue Jun 11 2024

.KEY MESSAGES...

- Strong to severe thunderstorms are again possible Monday
  afternoon and evening, mainly for areas west of Highway 83,
  with large hail and damaging winds the main concerns.

- Temperatures will climb towards the middle of the week with forecast
  highs in the middle to upper 90s for much of southwest
  Nebraska, increasing heat concerns.

- Temperatures cool towards late week into the weekend with
  continued rain and thunderstorm chances, peaking Friday
  afternoon and evening.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 258 PM CDT Mon Jun 10 2024

Conditions have remained dry during the day today as the area
remains under the influence of high pressure which sits just east of
the local area. As this feature continues to shift into the
Mississippi Valley, southerly flow will increase across the High
Plains. At the same time, a more pronounced shortwave tracking just
north of the Canadian border will bring modest height falls into the
area as a surface cool front trails the main low and approaches from
the northwest. Ahead of this feature, dew points have climbed into
the mid to upper 50s. Steep mid-level lapse rates continue to
overspread the area, promoting moderate to strong instability
denoted by MLCAPE values in the 1500-2500 j/kg range. Shear is
adequate with h5 flow immediately behind the front of 30 to 40 knots
Combined with low-level southerly to southeasterly flow and 0-6km
BWD values range from 25 to 35 knots in closer proximity to greatest
low-level forcing along the boundary. Thunderstorms are already
ongoing across the far western Nebraska Panhandle and will gradually
shift east this afternoon and evening into the local area. Storms
initially will favor discrete modes capable of large hail and
damaging wind gusts but as they congeal with eastward progression,
expecting the threat to largely transition to damaging winds. PoPs
ramp up markedly after 21z (4pm CDT) and peak around the 6-11pm CDT
window with values as high as 80%, or Definite categorical, across
the Sandhills. A heavy lean on HRRR/HREF/NAM Nest guidance was used
to come up with the timing and progression of these. Given fairly
appreciable PWATs, can`t rule out some locally heavy rainfall.
Latest QPF values generally range from 0.25" to 0.75" with locally
higher amounts possible. This, in general, matches latest HREF
output though HREF ensemble max values suggest values as high as 1-
2". Believe quick progression, rapid decrease in intensity, and
topography of Sandhills should preclude any Flooding concerns with
this activity. Regarding this rapid decrease in intensity...storms
will continue to track east into central Nebraska but are largely
expected to outrun the greatest instability. Latest SPC Mesoanalysis
guidance shows a rapid decrease from west to east with most
locations along and east of Highway 83 showing less than 500 j/kg of
MUCAPE. This should hasten the weakening after 10pm CDT tonight with
no severe weather anticipated thereafter though lingering rain and
general thunderstorms should persist through the overnight before
exiting to the east prior to dawn Tuesday. Lows tonight should fall
into the low 50s west to near 60 degF east.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 258 PM CDT Mon Jun 10 2024

Tuesday...modest high pressure will shuffle through the area which
will help promote dry conditions. Winds will be light and variable
through the day, becoming more southerly by late afternoon.
Temperatures at h85 will actually increase from Monday to Tuesday
and with deeper mixing expected, forecast highs will add 2 to 5 degF
for all locations from Monday`s values. Forecast highs will settle
in the 80s for all and even some upper 80s for far southwest and
north central Nebraska. Quasi-zonal flow will settle in behind
departing trough with the main h5 ridge beginning to shift east out
of the Great Basin. Subsidence aloft and increasing mid-level
temperatures should squash any precipitation chances for the day and
evening even with a surface boundary stalled in the area. This focus
should remain south though of the area.

Wednesday...the hottest day of the week and focus of increasing
concern for heat issues. Low amplitude ridging continues to drift
east across the US/Mexico border with ridge axis focusing across the
Central Rockies for Wednesday and the High Plains by late Thursday.
The associated thermal ridge will gradually spread west out of the
Great Basin with h85 temperatures climbing above the 90th percentile
by Wednesday morning and peaking around the 99th percentile by early
Thursday. A northern stream trough rounding the top of the mid-level
high pressure will propel a surface trough into the area. Ahead of
this, increasing southerly will propel a warm front north into east
central South Dakota. Broad WAA in the open warm sector will promote
rapid moistening in the low-levels. As daytime temperatures rise,
convective temperatures look to be breached by late afternoon which
would open the door for rain and thunderstorm development. What is
more lacking in the immediate area is a focus. The lack of any
appreciable surface convergence due to veered low-level winds or
forcing aloft casts considerable doubt on seeing the development of
any convection. Similarly minded, the NBM shows near negligible
probabilities for precipitation with only 20-30% chances of seeing
measurable rain for the day across far north central Nebraska. The
latest SPC Day 3 Outlook covers much of the area east of Highway 83
in a Marginal Risk (level 1 of 5) with a Slight Risk (level 2 of 5)
just encroaching in far eastern Boyd County. Believe a gradual
downtrend in Risk Categories is warranted should the going forecast
persist over the next day or two. The notable southwesterly flow
should support fairly deep mixing as forecast soundings show
potential for boundary layer depths to top 2-3km. This supports the
hot temperatures in the latest forecast with mid to upper 90s
prevalent for all areas with the exception of the western Sandhills.
Fortunately, the core of greatest surface moisture remains east of
the area, thus heat index values appear likely to fall short of
advisory criteria (100 degF). Even so, WBGT values will climb into
the Elevated to Moderate criteria with the latest Heat Risk guidance
reaching levels 2 and 3. This suggests concern for folks with
outdoor plans. The expected temperatures under mostly sunny skies
will be hazardous to folks if adequate precaution is not taken.

Thursday...similar to Wednesday, another hot day is likely for
mainly southwest Nebraska. Weak low pressure will drift through the
area in the early morning hours. This will promote increasing
northerly flow immediately following this feature which will drive a
cool front south into far southwest Nebraska up through northeast
Nebraska. With the thermal ridge still in place, modest mixing is
all that`s needed to tap in the anomalous temperatures off the
surface. In the post frontal air mass, cold air advection will
settle in but the overlap of strongest winds on the forward edge of
CAA and the 28+ degC h85 temperatures will be the area to expect
heat concerns yet again. This favors far southwest Nebraska, mainly
south of Highway 23, where afternoon highs will again climb into the
middle 90s. Heat concerns continue with heat index values climbing
into the upper 90s, Wet Bulb Globe Temp values reaching the Elevated
to Moderate levels, and Heat Risk values of 2. Though not as severe
as Wednesday, caution is again advised for folks spending time
outdoors. Further north across the area, CAA will abate the heat
with many locations returning back to the 80s. Late afternoon and
evening thunderstorm chances will return in close proximity to the
surface boundary expected to settle south of the immediate area.
Ensemble guidance remains fairly pessimistic with output showing low
probabilities but various deterministic solutions showing increased
potential. Will maintain the inherited Chance PoPs (< 30%) for now.

Friday and Saturday...the next notable chance for rain and
thunderstorms will arrive later in the day Friday. Ridge breakdown
will occur late in the day as a stronger shortwave tracks out of the
central Rockies. NBM PoPs paint a steady increase through the day,
peaking in the evening in the Likely (55-65%) category. A closer
look shows PoPs favoring the late afternoon through the early
morning hours Saturday based on 50th Percentile output and various
deterministic solutions. QPF amounts appear to be notable, with
both the EPS and GEFS solutions showing 50-70% probabilities of
seeing > 0.10" and 20-40% probabilities of seeing > 0.50". The
threat for severe will need to be monitored but the overall pattern
setup suggests at least an isolated threat with a narrow plume of
moderate instability and h5 flow approaching 30 to 40 knots. Highs
on Friday will reach the low to mid 80s, increasing to the mid to
upper 80s for Saturday.

Sunday and beyond...continued modest southwesterly flow will promote
fairly active weather continuing in the extended period. Variations
in precise evolution of the extended period casts some doubt, but
the overall pattern will favor warm temperatures and recurring
chances for precipitation. A strong northern stream system will
track east out of the Pacific Northwest, dragging a cool front south
into the area sometime early next week. The latest Climate
Prediction Center Outlook favors continued above normal temperatures
likely due to southeastern ridging. At the same time, the latest 6-
10 Day outlook shows above normal precipitation favored as well
which supports the daily low-end PoPs for Days 6 and 7.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 109 AM CDT Tue Jun 11 2024

Rain will exit the area early this morning with VFR conditions
expected to prevail though the day today. Winds will be light
and gradually become south to southeast at 5 to 15 kts by late
this afternoon lasting into tonight.

&&

.CLIMATE...
Issued at 258 PM CDT Mon Jun 10 2024

Record Highs for LBF CWA Climate Sites:

               Wed 06/12   Thu 06/13   Fri 06/14
North Platte   102 (1952)  108 (2022)  101 (1952)
Valentine      104 (1952)  103 (1956)  105 (1979)
Broken Bow     101 (1952)  103 (2022)  101 (1952)
Imperial       104 (1952)  106 (2022)  108 (2006)

At this time, no records are projected to be broken.

&&

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

&&

$$

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