Area Forecast Discussion
Issued by NWS Salt Lake City, UT
FXUS65 KSLC 170326
Area Forecast Discussion
National Weather Service Salt Lake City UT
926 PM MDT SAT JUL 16 2016
.SYNOPSIS...High pressure over the southern Rockies will shift
to the east ahead of the next upper level trough settling into
the Pacific Northwest late in the weekend. Moisture pooled to the
south over Arizona will begin to spread north across southern Utah
Sunday, then over most of southern and eastern Utah early in the
.SHORT TERM (Until 12Z Tuesday)...The old surface boundary across
central Utah is still evident in MSAS data at mid-evening. North
of this surface boundary a loosely organized band of light showers
and/or virga exists from west-central Utah up through the Salt
Lake valley. This band appears to be focused along a confluence
zone along the near 600mb baroclinic zone with weak dynamic
support from a possible shortwave entering western Utah at
mid-evening. Not looking at much increase in either areal coverage
or intensity with the loss of daytime heating through the
remainder of the evening hours.
The next upper level trough moving south along the Britcol coast
will strengthen as it settle along the pacific Northwest coast
by early Monday. The downstream pattern across the Great Basin
will see the mean layer flow backing to the southwest beginning
Sunday. A fair amount of moisture pooled over the southern half of
Arizona will be drawn north into southern Utah Sunday, with a
broad area of deep layer moisture over southern and eastern Utah
Will likely see a significant increase in convection between
Sunday and Monday. Absent any substantial dynamic forcing, would
suspect most of the convection will get started over the higher
terrain, with some of the stronger cells drifting into the
adjacent valleys late in the afternoon and evening. The potential
for heavy rainfall will remain limited with the initial surge of
moisture, but could develop over a broader area beyond the short
range forecast period.
.PREVIOUS LONG TERM (After 12Z Tuesday)...A nearly stationary
upper level low off the coast of the Pacific Northwest will be in
place Tuesday morning. A shortwave rotating around the base of
this trough will help to start to elongate this trough toward
western Washington. With this shift, expect the deepest moisture
will be restricted to areas of Utah from the Wasatch Crest
eastward from Tuesday and Wednesday.
By Wednesday afternoon/evening, the next wave in a fairly
progressive pattern across the Eastern Pacific will help to
finally eject the persistent trough out of the Pacific Northwest.
The ejecting wave is then expected to approach the Pacific
Northwest Coast Friday. The main impact this will have is at
least minimal moisture will likely start to build back toward
the northern and western portions of the state after Wednesday.
Models have been relatively inconsistent with this portion of
the forecast, so continued to leave low pops from Thursday onward.
.AVIATION...High-based but weak convection will impact areas from
the terminal southward through the balance of the evening. Brief
but not particularly strong gusts may develop with these light
showers/virga through 04Z. Skies will gradually clear late
tonight. Prevailing winds will turn to the south-southeast after
.PREVIOUS FIRE WEATHER...A weak cold front will remain stalled across
central Utah through this evening. Ahead of this cold front, a
breezy and dry southwesterly flow remains in place. The cold front
will weaken and retreat northward tomorrow, spreading breezy
southwest flow into northern Utah. As a result, have expanded fire
weather highlights into northern Utah for tomorrow.
Moisture begins to spread into southeast Utah tomorrow. This will
bring a small chance of dry thunderstorms to the mountains and some
of the southeastern valleys tomorrow afternoon. The moisture is
expected to increase rapidly across the spine of Utah and eastern
valleys by Monday with a corresponding increase in relative
humidity. Although thunderstorms will increase in coverage, the
chance of wetting rain will also increase. However, west-central and
northwest Utah will remain dry with breezy southwest winds on Monday.
Moisture is expected to decrease a bit on Tuesday, but the rest of
the week will see moisture continuing to spread into the southern
and eastern portions of the fire district.
UT...Red Flag Warning until 8 PM MDT Sunday for UTZ484-489-493-495-
Red Flag Warning from noon to 8 PM MDT Sunday for UTZ479-483.
Red Flag Warning until 9 PM MDT Monday for UTZ492.
Red Flag Warning from noon Sunday to 9 PM MDT Monday for UTZ478.
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