High Wind in Utah, May 11, 2022

Area Forecast Discussion
National Weather Service Salt Lake City UT
415 AM MDT Wed May 11 2022

.SYNOPSIS...Southwest flow will remain in place today ahead of a
trough and cold front. A quick round of precipitation is expected
later tonight into Thursday morning as this system crosses the
region. A pronounced warming trend is expected Friday into early
next week.

&&

.SHORT TERM (Through 12Z/6AM Friday)...

A cold area of low pressure embedded within a broad PacNW trough
currently resides across central California. The low/trough will
gradually translate eastward into the Great Basin through the day
today before crossing Utah and southwest Wyoming tonight into
early Thursday morning. In advance of this system, broad southwest
flow will be in place across all but the far NW corder of Utah.
With plenty of sunshine across central and southern Utah in
particular today, strong lapse rates will aid in efficient mixing
and subsequent transfer of momentum to the surface, translating to
SW wind gusts in the 45-55 mph range across much of central and
southern Utah and the eastern valleys this afternoon/early
evening. While winds are not forecast to be as strong as those
observed on Sunday, winds will be strong enough to cause
difficult driving conditions via crosswinds, patchy blowing dust
as well as chop on area waterways. The gusty winds and low
relative humidities will promote increased wildland fire behavior
as well. Inherited Wind Advisories and Red Flag Warning remain in
place. Given that winds have had a tendency to overachieve of
late, winds were populated using a blend of the NBM4.1, NBM 90th
percentile and the HRRR, on top of a locally- produced correction
factor. Discussed upgrading eastern valleys to a High Wind
Warning, and winds this strong are well-represented by the
ensemble max. Opted not to manually increase winds to this
extent, but wind trends will bear watching today

Showers associated with the incoming system are forecast to
gradually develop across northern Utah this evening. As showers
develop in the post cold frontal airmass, a period of gusty winds
are now forecast to develop across the GSL desert and GSL this
evening, and the HREF ensemble mean wind gusts suggest a period of
NW wind gusts near 45 mph reaching the I-80 corridor this evening.
Showers will continue to overspread northern Utah and SW Wyoming
overnight associated with the deformation zone on the NW flank of
the low. A brief period of upslope enhancement appears possible
across favored areas of northern Utah late tonight and early
Thursday morning. While instability parameters are scant, a rumble
or thunder or two can't be ruled out overnight. Snow levels are
forecast to fall to around 5500ft Thursday morning, which will
result in snow as low as Parley's Summit, with a brief period of
rain/snow mix possible on benches as well. Showers will linger
across NE Utah and SW Wyoming through Thursday morning before
diminishing as the system departs.

A cool day is in store on Thursday as 700mb temperatures are
forecast to be 1-2SD below normal. This system is not forecast to
be quite as cold as the Monday one, however. That said, some
localized hard freeze conditions are possible Thursday morning
across central mountain valleys.

A trough is then forecast to reload across the PacNW Thursday and
Thursday night before propagating eastward into the Idaho
Panhandle Friday morning. A round of height falls will graze the
ID/UT border in association with this system, and a resultant
low-end chance for a shower will be possible near the ID/UT
border, although the bulk of this activity should remain north of
Utah.

.LONG TERM (After 12Z Friday)...

Zonal flow will be in place Friday with heights gradually building
associated with a ridge that will move through for the weekend.
Temperatures will warm to near average in northern Utah and
several degrees warmer than average further south.

Warm air advection will take place as winds veer, with zonal flow
transitioning more southwest. Ensembles are in good agreement of the
aforementioned ridge axis to the west. This will result in
temperatures reaching around 10F warmer than Friday.

Temperatures are expected to peak Sunday and Monday as the ridge
axis crests Utah Sunday and moves downstream Monday.

For Salt Lake City, if 80F is not reached Saturday where the
forecast high is 79F, it is likely to Sunday, where the forecast
high is 85F. This would be the first 80F of the season, around a
week and a half later than average. Record temperatures are not
expected for southwest Wyoming and northern Utah. There are better
chances for record temperatures for southern Utah.

Sunday's forecast high of 85F at Cedar City would be 1F short of
that day's record, and Monday's same forecast high would be 2F
cooler than the record. St. George is expected to reach the upper
90s, which would fall slightly lower than record highs for those
days. While winds will be relatively light, very dry conditions will
be in place, with afternoon relative humidity in the single digits
in this portion of the state. Northern Utah will be very dry as
well, with minimum relative humidity values mainly in the teens.

Ensemble guidance has more differences into next week, but a trough
is expected to move into the Pacific northwest. There is a lot of
variance with the trough, but it is expected to lower heights with
the ridge moving east. This will result in cooler, but still warm
conditions Tuesday.

&&

.AVIATION...

KSLC...Mostly clear conditions will transition more cloudy during
the afternoon. Winds will increase through the morning out of the
south or southwest and transition northwest around 21Z. Scattered
rain showers will build in from 06-09Z, with the chance for gusty
outflow winds. Light rain showers are expected from around 08Z or
09Z through 12Z. Ceilings could lower into MVFR range with these
showers, but VFR conditions will prevail.

.REST OF UTAH AND SOUTHWEST WYOMING...Wind gusts will exceed 40
knots for much of southern Utah during the afternoon. This is
expected to result in blowing dust, reducing visibilities. Winds will
be gusty in southwest Wyoming and northern Utah, with gusts reaching
near 30 knots. Clouds will increase in southwest Wyoming and
northern Utah during the afternoon. Scattered rain showers will
build in around 06Z. Outflow wind gusts are possible initially.
Scattered rain showers are expected from around 08-12Z for northern
Utah and through 14Z in southwest Wyoming where snow is expected.

&&

.FIRE WEATHER...

A trough and area of low pressure will move east from central
California today, ultimately crossing through central Utah
tonight. Out ahead of this system, another day of windy conditions
will be in place mainly across central and southern Utah,
especially during this afternoon and evening. Minimum relative
humidity values will range from the single-digits to the mid teens
once again across most of central and southern Utah. The
combination of winds and low relative humidity will create
critical fire weather conditions, especially across portions of
southern Utah where fuels have moved into the critical category.
Red Flag Warnings have been issued for those areas where fuels,
winds and low relative humidity values are juxtaposed.

As the trough and low pass through Utah tonight, an attendant
cold front will also cross the state. This will bring briefly
cooler temperatures in the wake of this system Thursday, along
with a brief shot of showers and better humidity recovery across
northern and portions of central Utah tonight into Thursday
morning. A stout warming and drying trend will Friday into the
weekend. Temperatures are expected to be well above average by
Sunday, with low humidities. At this time, no widespread wind or
precipitation events are expected into early next week.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Wind Advisory from noon today to 9 PM MDT this evening for
     UTZ114>116-119>123-126>131.

     Red Flag Warning from noon today to 9 PM MDT this evening for
     UTZ496-497.

WY...None.
&&

ADeSmet/Wilson

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