Area Forecast Discussion
Issued by NWS North Platte, NE

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943
FXUS63 KLBF 200443
AFDLBF

Area Forecast Discussion
National Weather Service North Platte NE
1143 PM CDT TUE JUL 19 2016

.SHORT TERM...(This evening through Wednesday)
Issued at 352 PM CDT Tue Jul 19 2016

A ridge of upper level high pressure is centered across central
Kansas this afternoon. Models indicate a few thunderstorms will
develop on the western periphery of the high across central and
northeast Colorado this afternoon. The steering flow around the
high would carry any storm into far southwest and west central
Nebraska this evening before dissipating. Will carry a slight
chance for this area through the evening.

Otherwise a very hot day is expected Wednesday with H850mb
temperatures climbing into the upper 20s to lower 30s celsius.
This will support highs nearing 100 degrees all locations. Added
humidity will push heat index readings to near 105 degrees east of
highway 83, and have issued an Excessive Heat Warning for these
areas. Humidity will be less to the west of highway 83, and have a
Heat Advisory for these locations. Will keep the forecast dry
during the day Wednesday, as a stout capping inversion suppress
any thunderstorm activity.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 352 PM CDT Tue Jul 19 2016

Wednesday Night through Thursday Night: Not much was changed in
terms of sensible weather this time period with excessive heat
anticipated across much of north central, central, and southwest
NE. Wherein, the maximum heat indices in the afternoon will be
greater than 100 degrees Wednesday through Friday. It is also
anticipated that some locations will even see max heat index
values that exceed 105 degrees in local portions of north central
and central NE. The anticipated longevity of this heat event,
Tuesday through Friday, will create a dangerous situation in which
heat illnesses are possible during the day, mostly notably for
sensitive groups.

North Platte is forecast Wed and Thu to read a high at or just
above 100 -- the last time they saw two consecutive days or more
at or above 100 was in 2013 (late Aug). Wed and Thu will be the
hottest days followed by a gradual cooling trend this weekend with
highs Sun in the mid 80s to lower 90s.

Overall, deterministic guidance are in pretty good agreement
during this time frame with the large scale pattern. The mid-level
ridge over the forecast area will be firmly in place at the start
of the period with a large 500 hPa high over southern CONUS
centered over eastern OK. Over time, the high will move slowly to
western OK/TX Panhandle by Thursday night. Models are in fair
agreement in showing a few shortwave troughs rounding the ridge
over this time, these disturbances will provide weak large-scale
ascent. At the surface, a broad leeside trough will have deepened
a bit over the western northern and central plains Wed evening. A
weak surface low is expected to be over central SD Thursday
morning with a trough N-S across central NE and a cold front SW-NE
across extreme northwest NE.

The weak cold front associated with the low is expected to reach
into our northwest quad of the CWA by Thursday afternoon as a
trough extends to the southern great plains. The combination of
the front in the vicinity of the CWA and large-scale ascent via
the disturbance aloft on Thursday provides us a little more
confidence in showers/TSTMs Thu compared to Wed evening. However,
uncertainty in the front`s location and how exactly it will evolve
over time remains a concern. Not to mention the thermodynamic
environment, with very warm temperatures at low-levels/cap, that
may hinder or hold back any convective development. Ultimately,
there is a marginal risk for a few strong storms in our area, and
this is noted also in the SPC Day 3 Outlook that was issued today.
As such, there are slight chances for showers and thunderstorms
Wed evening and Thu afternoon/evening, except for an limited area
of chances across portions of north central NE Thu.

Friday through Tuesday: Despite the weak cold front affecting our
CWA late Thursday, Friday looks to be another hot and humid day.
The weak low will weaken into a trough as a stronger leeside
trough develops and deepens across the northern and central Great
Plains. Meanwhile, a strong disturbance in the mid-level flow will
be rounding the 500 hPa high over the CWA as the southern CONUS
high begins to break down some Friday. This break down of the
ridge could be attributable to a trough moving into the northern
great plains Friday. However, there is still some uncertainty
with regard to phase/timing. The stronger surface trough will then
become a low and move off into eastern ND/SD/NE by Saturday
morning. The flow at mid-levels will become more quasi-zonal
through this period as the 500 hPa high over southern CONUS breaks
down some.

While there are some timing issues between the guidance with some
of the large scale features, a few disturbances aloft will bring
increased chances for showers/TSTMs this period. In general,
cooler temperatures and, overall, less humid conditions are
expected to be in place Saturday as another weak front pushes
through in the morning. Slight cooler conditions are then
expected Sunday.

Models in the long time suggest ridging occurring in the
southwest as the ridge rebuilds somewhat as a trough moves into
the Northeast US late Sunday. That said, models are showing
appreciable discrepancies between each other in phase and
amplitude in the 500 hPa pattern late Sunday into Tuesday. Highs
at this time are for mid 80s to lower 90s Monday and Tuesday.
Confidence is low to moderate from Monday onward at this time.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1143 PM CDT Tue Jul 19 2016

An upper level ridge will keep mainly clear skies and vfr
conditions persisting for the KLBF and KVTN terminals. There will
be a period of low level wind shear at KLBF, from 08z-12z
Wednesday.

&&

.LBF Watches/Warnings/Advisories...
Heat Advisory until 7 PM CDT /6 PM MDT/ Friday for NEZ004-022-
023-035-056>058-069-070.

Excessive Heat Warning until 7 PM CDT /6 PM MDT/ Friday for
NEZ005>010-024>029-036>038-059-071-094.

&&

$$

SHORT TERM...Taylor
LONG TERM...ET
AVIATION...Roberg



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