Area Forecast Discussion
Issued by NWS Salt Lake City, UT

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391
FXUS65 KSLC 271030
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
430 AM MDT Thu Jul 27 2017

.SYNOPSIS...Monsoonal moisture will remain in place across the
region today. A slight drying trend is expected through at least
the first part of the weekend for much of the area while deeper
moisture remains over southeast Utah.

&&

.SHORT TERM (Through 12Z Saturday)...Southwesterly flow aloft
continues to prevail across the forecast area this morning.
Although the airmass has dried somewhat over the past 24 hours,
ample boundary layer moisture remains in place, characterized by
GOES-derived PW values near 1 inch across most valleys, and
surface dew points in the 50s in the western valleys, and low to
mid 60s across the south and east.

An upper low which had resided across northern CA over the past
couple of days is in the process of ejecting northeast through the
northern Great Basin. A 700mb convergence axis coupled with upper
level diffluence is helping to maintain a persistent band of
convection across east central NV at the present time. As the
parent wave continues to lift northeast today, given the abundance
of boundary layer moisture would anticipate scattered convection
to fire across the northern half of the area late morning through
mid afternoon. The most recent versions of the HRRR dissipate the
ongoing convection across NV as it spreads into western UT with
very limited redevelopment by early afternoon. However given the
aforementioned moisture and some degree of upper level support,
have included 30-40 PoPs across the north through the afternoon.
Mid level flow near 30 kts could allow for enough shear for
loosely organized convection early this afternoon as well. Further
south would anticipate convection to be more driven by terrain
circulations through this evening, as is more typical.


The airmass is forecast to continue to slowly dry on Friday, and
with the lack of an obvious forcing mechanism aside from heating
of elevated terrain, would suspect the convective threat across
the forecast area will trend further downward, and become
increasingly tied to the terrain.

.LONG TERM (After 12z Saturday)...Overall, mean ridging will remain
in place across the West through the long term portion of the
forecast period. Drier air will work into the western portions of
the state, suppressing convection to the west of the Wasatch,
central and southern mountains through early next week. For much of
the forecast, any focused lifting mechanism remains well displaced
from the CWA and convection will largely depend on terrain and
outflow/boundary interactions for development and any sustained
organization.

By Monday, several global models are bringing at least a period of
higher PWs further west, which may help to develop convection
further west into the Wasatch Front. Most guidance indicates this
period is brief, with convection suppressed to areas south and east
by Tuesday.

&&

.AVIATION...An area of showers and thunderstorms is expected to
impact the SLC terminal beginning around 15-17Z and continuing at
times through about 20-22Z. This should bring occasional lightning
and winds that may be gusty and erratic at times.

Light and variable winds are expected to become predominately
southerly between 14-16Z.


&&

.FIRE WEATHER...Monsoonal moisture lingering across the region
will maintain a threat of showers and thunderstorms capable of
producing wetting rains today. A greater chance will exist across
the north, where a weather disturbance will brush by the area.
High pressure is forecast to gradually strengthen across the
region late in the week through the upcoming weekend. This will
result in a slow drying and warming trend, with any threat for
thunderstorms becoming more isolated, and tied to the higher
terrain.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...None.
&&

$$

Seaman/Kruse

For more information from NOAA`s National Weather Service visit...
http://weather.gov/saltlakecity

For frequently asked questions about the Area Forecast Discussion
visit...
http://weather.gov/saltlakecity/general/afd_faqs.php



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