High Wind in Wyoming, April 11, 2022

Area Forecast Discussion
National Weather Service Salt Lake City UT
449 AM MDT Mon Apr 11 2022

.SYNOPSIS...A strong low pressure system will push a potent cold
front across the region late this afternoon through this evening.
Much colder and unsettled conditions will follow through midweek.

&&

.SHORT TERM (Through 12Z Wednesday)...A compact upper low spinning
along the Pacific Northwest coast will translate inland and across
the interior Pacific Northwest and northern Rockies today through
tonight. The associated cold front will reach northwest Utah by
mid afternoon, then push through much of northern, central and
southwest Utah by mid evening. Meanwhile an axis of IVT along the
southern periphery of this low is currently making landfall along
the southern OR/northern CA coastline. This IVT axis will
gradually decay as it shifts south today, but allow for inland
moisture penetration both to the north of the Sierra this morning,
then eventually around the southern end of the Sierra late this
afternoon and evening as this IVT axis shifts south. The result
will be ample moisture spreading into the eastern Great Basin.

Anticipate high based convection to develop ahead of the
approaching front as upper diffluence increased across northern
Utah by mid afternoon, followed by a band of heavy precipitation
along the surface front and trailing baroclinic zone as it crosses
northern and central Utah late this afternoon through this
evening, and interacts with the aforementioned moisture. The
majority of this precipitation will fall as rain along the
northern and central valleys through mid evening before snow
levels fall to the valley floors late in the evening, toward the
tail end of the primary precipitation band. Meanwhile a period of
very heavy snow is expected along the higher terrain of northern
Utah this evening. This heavier precipitation will shift south
along the I-15 corridor of central and southwest Utah late evening
into the overnight hours. Precipitation will trend downward and
become more orographically forced across the north in the wake of
this boundary overnight, as snow levels fall to the valley
floors.

The compact nature of the upper low and a deepening surface low
along the frontal boundary, will result in strong low level wind
fields across central and southern Utah later this afternoon
through this evening within the prefrontal environment. As such
have expanded wind advisories into the remaining central valleys
this afternoon and evening ahead of the approaching front, as well
as included a wind advisory for northwest Utah within the post
frontal environment this afternoon and evening.

A cold and unstable northwest flow will maintain orographic
snowfall through much of the day Tuesday. Most valley locations
will run 20-25F cooler Tuesday afternoon, as they struggle to
reach the 40F mark.

.LONG TERM (After 12Z/6AM Wednesday)...Snow showers are expected to
linger across the northern portion of the forecast area into
Wednesday afternoon, especially across the northern mountains. Areas
typically favored in northwest flow may be able to squeeze another
inch or two of accumulations out despite the rapid decline in
available column water as the best transport moves east of the
forecast area. A brief period of ridging is likely to develop, noted
in H5 heights across the model suite and supported by the ensembles
as evident in nearly all of the membership. This will finally bring
a break in the action with any remaining snow showers ending in the
evening. Much warmer temperatures are on deck for Thursday with a
push of warmer air from the southwest and likely breaks in the
cloud deck allowing for some help from afternoon solar heating.

The majority of the ensemble forecasts support the development of a
distinct shortwave trough digging southward out of a parent longwave
over the PNW, as evidenced by 3/4 of the clusters (90% of the
membership). There is a staggering amount of spread in the depth and
time of arrival for this feature, and as a result PoPs remain
relatively low with broad areas of minor QPFs across northern Utah.
Can say with some degree of certainty that a few additional inches
of snow can be expected for the northern mountains, and that much of
the northern half of the forecast area will see continued unsettled
weather from Friday morning through the weekend. However, remains to
be seen if enough cold air can propagate southward to push snow
levels down to valley floors with this trough. The ensemble mean H5
pattern suggests not, with the shortwave quickly lifting back into
the mean flow without causing much in the way of impacts. Offering
the more potent scenario, a GEFS-dominated cluster (well represented
by the 00Z GFS) with 30% of the total membership suggests an
additional northern valley snowfall event with the bulk of the
precipitation falling Friday-Saturday.

At least a brief break in the active weather across the forecast
area is expected to start off next week with ensemble mean heights
favoring a high amplitude ridge setting up over the California coast
or the Great Basin. This continues into the day 8-10 (mid next week)
period, with a minority 30% of the ensembles rushing the next trough
in from the west.

&&

.AVIATION...KSLC...Expecting southerly winds to ramp up through the
morning hours as mixing increases and surface winds tap into strong
low-level flow ahead of the incoming cold front. Gusts could reach
as high as 30kts out of the south-southwest at times, especially
after 19Z. The frontal passage is expected between 21-23Z with a
rapid shift to northwesterly winds at the terminal, which are
expected to come in fairly strong, in the ballpark of 15-25kts.
Initially dry air will delay the onset of precipitation at the
surface, but will lead to gradually lowering CIGs in the post-
frontal environment. Expecting rain to change to snow around 03Z,
and with it a likely transition from VFR to IFR conditions that are
expected to persist through the early morning hours Tuesday.

REST OF UTAH AND SOUTHWEST WYOMING...Active weather with strong
gusty winds at the majority of terminals and a mixed bag of VFR
through LIFR conditions are possible across the forecast area
starting Monday afternoon. A cold front moving into northwestern
Utah will bring with it widespread precipitation and rapidly
lowering CIGs. Precipitation will likely begin as rain, changing
over to snow in the late evening for northern through central Utah
and southwest Wyoming. In the pre-frontal environment, expect gusty
winds out of the south through southwest, potentially in excess of
45kts at times, especially across southern Utah and the eastern
valleys. With ample moisture and lift, widespread mountain
obscurations and multiple cloud decks are likely throughout the
forecast area, especially in the afternoon and evening.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Wind Advisory from 3 PM this afternoon to 6 AM MDT Tuesday for
     UTZ120-121-131.

     Wind Advisory from noon today to midnight MDT tonight for UTZ101-
     115>119-122-125>127-129.

     Wind Advisory from 3 PM this afternoon to 4 AM MDT Tuesday for
     UTZ123-124.

     High Wind Warning from 3 PM this afternoon to 6 AM MDT Tuesday
     for UTZ128-130.

     Winter Storm Warning from noon today to 3 AM MDT Wednesday for
     UTZ110>112.

     Winter Weather Advisory from 8 PM this evening to 3 AM MDT
     Wednesday for UTZ113-117.

WY...Winter Weather Advisory from noon today to 3 AM MDT Wednesday
     for WYZ021.

&&

Seaman/Wessler

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