Area Forecast Discussion
Issued by NWS Salt Lake City, UT
FXUS65 KSLC 231516
Area Forecast Discussion
National Weather Service Salt Lake City UT
916 AM MDT MON MAY 23 2016
.SYNOPSIS...An elongated upper level trough stretching from southern
Canada to the California coast will maintain a mild southwest flow
over Utah early in the week. Cooler and more unsettled conditions
will return midweek as the trough shifts east through the Great
Water Vapor loop shows an expansive trough firmly in
place across the Western CONUS. One embedded wave is currently
crossing Central Utah while the next one off the Pacific coast
will approach the West Coast tonight. AMDAR 400-200MB wind
observations place a 80-120kt cyclonic jet from the Eastern
Pacific across the Desert Southwest and into the Upper Midwest.
GOES/HRRR/12Z KSLC RAOB indicate the precipitable water value
ranges from 0.10"-0.20" Southwest Valleys and mountains to
0.30"-0.50" most valleys.
Going forecast in great shape. Expecting periods of mid and high
clouds across Northern Utah downstream of the aforementioned wave.
Radar trends already indicate high based shower activity across
the North, which will continue to deepen especially near the
higher terrain with diurnal destabilization.
Only minor tweaks based on latest observational and model data.
A mean longwave trough remains in place over the western CONUS
this morning, with several embedded shortwave disturbances evident
on water vapor imagery. The first such feature is currently over
southern Nevada and will lift northeast across Utah today. Some
mid and high clouds have already spread into Utah ahead of this
trough, and a few weak showers are evident on radar across
northwest Utah. However, with a drier southerly flow spreading
across central Utah, showers and thunderstorms today should remain
confined to northern Utah with less coverage than in the past few
days. Otherwise, the airmass will see a warming trend today
although temperatures will remain a few degrees below
climatological normals across most areas.
After a bit of a lull in shower activity tonight, the next shortwave
disturbance, currently off the West Coast, will rotate into the area
tomorrow afternoon. This more energetic feature should bring a
slightly better chance of showers and thunderstorms to the area.
The third feature, currently just southwest of Vancouver Island,
will dive strongly south before swinging inland as a weak closed low
tomorrow night. This low will track across far northern Arizona and
could bring a small chance of showers to portions of southern Utah
Wednesday afternoon and evening. Meanwhile, another shortwave
disturbance is progged to rotate around the closed low currently
over southern Alberta/Saskatchewan and graze northern Utah. This
wave will help push a weak boundary into northern Utah which could
keep scattered showers in place across the northern and west-central
Utah Wednesday into Thursday morning.
The bulk of the Pacific trough is expected to exit to the east
through the day Thursday, but enough moisture and instability
should be in place to keep showers going through the afternoon.
Some warming and drying is expected Friday, as shortwave ridging
builds over the Rockies between storm systems.
The next system coming out of the Pacific Northwest is a large
closed low that is forecast to dig into western Idaho starting
Friday night. However, confidence beyond that is very low for Utah
and southwest Wyoming. The GFS hangs this low back to the west,
keeping the forecast area relatively dry and warm through the
weekend, while the ECMWF insists on pushing a decent cold front into
northern Utah on Saturday. While there isn`t a huge difference in
the placement of this low in the models, the devil is in the
details, and that is what keeps the nature of the weekend and beyond
sketchy. For now, have raised POPs to place them closer to
climatological values, with no major changes to most other forecast
elements for days 5-7.
.AVIATION...A light southeast drainage wind will transition to a
northwest lake breeze around 17Z. VFR conditions are expected to
prevail through the valid TAF period. While shower and
thunderstorm coverage across the Salt Lake Valley will be less
than occurred the last couple of days, there is a 20 percent
chance for a shower or thunderstorm to impact the KSLC terminal
from mid afternoon into this evening.
.FIRE WEATHER...Today and Tomorrow expect more sunshine low RH and
warm temperatures across the South as Southwest winds pick up. The
North will see higher RH and more clouds with isolated to
scattered showers and thunderstorms but still mild conditions.
Snow Levels look to range 7000 to 9000 ft.
A storm system looks to take aim on the region Wendesday into
Friday. The biggest expected changes will be the extent of
convection should cover the entire region with more moist
conditions resulting across the south as a result. Initial
convection could see a high risk of gusty/erratic winds due to dry
microbursts. With a cold frontal passage Wednesday and Wednesday
night Northwest flow will become predominate. Temperatures and
snow levels should remain fairly steady through the week.
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