Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 05/07/19

previous forecast discussion below. Huston



 A low pressure system will work through the region through Tuesday.
We`ll see a few showers and thunderstorms this afternoon and this
evening, mainly across the high country. Some activity may persist
through the overnight period with a good chance for showers and
thunderstorms on Tuesday as the low is over the area. There`s enough
instability around that we could see a few strong storms with gusty
winds and small hail possible. Valle

.LONG TERM...Wednesday Through Next Monday.
Few changes made to the forecast Wed onward, and no major/high-
impact wx is currently anticipated. Longwave trough axis will be
shifting east of our forecast area Wed, but this progression is
expected to halt with the trough retrograding/stretching back to the
SW over our area Wed night/Thurs, eventually closing off a low over
CA. Thus, some continued shower and t-storm activity will likely
occur both days, especially afternoon/eve hours and especially
across the southern/eastern highlands, with the Snake Plain
remaining mostly dry. Daytime highs will only reach the 50s/60s. A
strengthening ridge of high pressure will build in from the west for
Fri and the weekend with increasing confidence in dry wx and
progressively warming temps, possibly reaching the upper 70s in the
Snake Plain/Magic Valley Sun and approaching 80 Mon. The
GFS/EC/Canadian all show the ridge becoming "dirty" by Mon eve as it
centers itself right over our area, with some moisture possibly
coming into play under the high. For now, we carry a few showers
from the eastern central mntns into the Upper Snake Highlands, but
would like to monitor how models trend in the days ahead.
&&

.AVIATION...The trend we started 2 days ago continues. This
afternoon/eve will feature another round of showers/t-storms as a
slow-moving trough approaches, with slightly greater coverage than
yesterday due to better lifting processes. We carry VCTS for all
terminals this time, generally in the 21Z-04Z window depending on
the airport. Confidence at this time is not enough to upgrade anyone
to TS, but NAM/RAP forecast soundings exhibit inverted-V temp/dew
point signatures with DCAPE values 700-1000 J/kg, which suggests
storms today could put down gusty/erratic outflow winds in excess of
40kts (and small hail). Thus, we will need to monitor radar trends
closely. NAM time-height plots and surface obs continue to show we
are fairly dry near the surface, so even if a cell hits a terminal,
winds will be the greater concern vs. cigs/vsbys, which we have high
confidence will remain VFR. One difference compared to the past 2
days will be lighter environmental winds generally remaining below
10kts, so outside of t-storms, crosswinds should be less of a
concern for GA aircraft (although our confidence in wind directions
is low today). Clouds will gradually thicken/lower tonight and Tues
AM, remaining VFR. There is some potential we may need to trend
toward -SHRA after 11Z in subsequent TAF updates as high-res
guidance is developing some decent shower activity, especially for
KPIH/KIDA/KDIJ, but low confidence is holding us at VCSH for now.
Expect another round of more widespread showers/t-storms Tues. -
KSmith/Valle
&&

.HYDROLOGY...With the warmer temperatures we are beginning to see
rivers and streams rise again. The Big Wood at Hailey has risen to
bankfull stage and is expected to remain in action stage for several
days. A flood advisory has been issued there. Valle
&&

.PIH WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$




Area Forecast Discussion

National Weather Service Reno NV

 327 PM PDT Mon May 6 2019

.SYNOPSIS...

Showers and thunderstorms will continue through this evening. The
threat for storms will become more limited to the Sierra Tuesday,
with dry conditions prevailing Wednesday. Chances for showers and
thunderstorms will return Thursday as low pressure backs into the
Great Basin. Afternoon showers and thunderstorms will be possible
Friday through early next week mainly south of Highway 50.

&&

.SHORT TERM...

The main change to the short term forecast was removing
thunderstorms from Wednesday. Otherwise, we made some minor
refinements to highlight the best thunderstorm chances this
evening, and reduced coverage of late night/morning activity for
the next two nights.

Scattered pulse-type showers with isolated thunderstorms have
developed across areas near and north of I-80 so far today, and
instability will become more favorable later this afternoon for
cell development south of I-80 to Mono and Mineral counties. Due
to the overall short duration of each cell`s peak strength, we
addressed the overall storm scenario with a Special Weather
Statement.

As we get later into the afternoon and early evening, some of the
high resolution guidance favored increased coverage of showers
with embedded thunderstorms in roughly an area from Carson City
southward across Douglas, Lyon, Alpine and northern Mono counties.
While we may need to keep an eye on burn scars within this area,
overall rainfall rates are likely to decrease as the convection
transitions into more of a stratiform rain area. Some rises on
rivers and small streams are also possible, but the risk of
flooding is low.

For Tuesday, as the deformation zone associated with the upper low
moves east of the region, the risk of showers and thunderstorms
will decrease. Some residual moisture and terrain-induced
convergence could produce isolated afternoon convection near the
Sierra, but coverage looks to be more sparse than today. A weak
shortwave moving southward across northern NV will bring
increased NW-N afternoon breezes--the most favorable wind
direction for producing rougher conditions on Pyramid Lake
sufficient for Lake Wind Advisory.

For Wednesday, a dry north to northeast flow will prevail, with
model soundings indicating a stronger mid level cap that will
inhibit thunderstorm formation. Even if some cumulus buildups or
brief showers occur near the Sierra crest during the afternoon,
they would be carried west of the crest by the prevailing flow.

Then for Wednesday night and Thursday, an upper level low is
projected to move in a less common southwesterly track from the
northern Rockies across the northern half of Nevada. This will
lead to shower development during the early-mid morning hours
mainly near and south of I-80. As the cold pool aloft moves
overhead during the afternoon, embedded thunderstorms will be
possible with the best overall chances in Alpine and Mono
counties based on the most likely track scenario. As the low
moves across the Sierra into central CA, a small deformation zone
could keep shower activity going through Thursday night for Mono
and southern portions of Mineral and Lyon counties. MJD

.LONG TERM...Friday through next Monday...

Only a couple of changes were made to the forecast. These changes
include the following:

  *Slightly increasing thunderstorm chances farther north into the
   Tahoe Basin and into southern Lyon County late Friday afternoon.

  *Increasing POP coverage over southern Mono County, the Tahoe
   Basin, and Lyon and Mineral counties Sunday afternoon.

Discussion:

For Friday, a closed low is expected to develop over
central/southern CA. The ECMWF has this closed low and the
attendant area of cyclonic vorticity advection slightly farther
inland over central CA/western NV compared to the GFS. Therefore,
POPs were increased farther north into the Tahoe Basin and
Mason/Smith Valley to account for this change.

On Saturday, the closed low will dig farther south into southern
CA/AZ, allowing for better mid-level cooling and synoptic lift
over the southern portion of our forecast area. Higher POPs and
slight chances for thunderstorms were carried over from the
previous forecast cycle, mainly over the central/southern Sierra
and the Sweetwater Mountains, since the position of the closed
low and the ridge over the northern intermountain west has not
deviated much from previous model guidance.

For Sunday and Monday, a ridge will build in overhead as the
upper low pushes off to the east. Temperatures should increase
about 5-10 degrees above normal for much of the forecast area and
convective coverage should wane, although low-end pops were kept
in the forecast from the previous cycle as increased heating and
weak zephyr-driven convergence could produce a few late day
cells. -Johnston

&&

.AVIATION...

Showers and thunderstorms have developed across the region. Some
of  these storms could be capable of producing heavy rainfall,
erratic outflow winds 35-45 kts, and small hail, all of which
could reduce visibility, cause mountain obscurations and
turbulence. Aircraft icing of the light and mixed variety could
also be a factor this afternoon/evening above ridge level near
RNO-CXP-HTH-NFL-LOL.

Weather looks to remain unsettled through this week, with shower
and thunderstorm chances each day except Wednesday, especially
south of the Interstate 80 corridor. -Johnston

&&

.REV Watches/Warnings/Advisories...
NV...Lake Wind Advisory from 2 PM to 8 PM PDT Tuesday for Pyramid
     Lake in NVZ004.

CA...None.
&&

$$

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