Area Forecast Discussion
Issued by NWS Salt Lake City, UT
FXUS65 KSLC 182159
Area Forecast Discussion
National Weather Service Salt Lake City UT
359 PM MDT MON JUL 18 2016
.SYNOPSIS...High pressure over the southern plains with an upper
level trough settling into the Pacific Northwest will leave the
Great Basin under a southwest flow through much of the week, with
deep moisture over southern and eastern Utah.
.SHORT TERM (Through 06Z Friday)...The forecast area remains under
southwest flow aloft in between the ridge over the central United
States and the trough off the Pacific Northwest coast. This has
allowed deep moisture to be drawn northward into southern and
eastern Utah with widespread PWs in excess of 1.0 inch.
Instability, however, is not particularly impressive so associated
shower/thunderstorm coverage this afternoon has been widely
scattered at best. Some additional development is possible through
the early evening before convection decreases in coverage.
Temperatures are rather warm over northern Utah, with maxes
running 5-8F above seasonal norms. Cloud over is keeping
temperatures near climo over southern Utah.
Little change in the overall weather pattern is expected over the
next few days. Southwest flow will continue on the back side of
the broad ridge that should move little. The initial Pacific
Northwest trough is progged to shift northward over the ridge into
Canada, but another trough is expected to take its place behind it
for the middle part of the work week. As a result, temperatures
will remain on the warm side and ample moisture will allow for
showers and thunderstorms over primarily southern and eastern Utah
each afternoon/early evening. However, instability is expected to
remain relatively weak, limiting organized convection, and
enhanced southwest winds will keep storm motion swift enough to
keep the threat of flooding limited as well. The trough is finally
expected to move onshore late Thursday into Friday, remaining
north of the forecast area but bringing a weak front into northern
Utah, cooling temperatures a bit.
.LONG TERM (After 06Z Friday)...The trough off the Pacific northwest
coast retrogrades westward this weekend allowing the ridge over the
Central portion of the country to move westward. This westward
migration of the ridge will cut off the monsoonal flow providing a
dry westerly flow rather than the southerly flow encountered during
the middle of the week. Max temperatures are expected to increase
very gradually as this ridge builds in with temperatures averaging 5-
10 degrees above normal by Sunday.
.AVIATION...Isolated high based showers have developed across the
Wasatch Front...and will continue to move across the area through 01-
02Z. These high based showers will have the potential to bring
strong...gusty and erratic winds to the SLC terminal through this
time. Otherwise...gusty south winds will continue into the
.FIRE WEATHER...Trough off the Pacific Northwest coast will remain
nearly stationary through Thursday with several disturbances moving
through the trough. The strongest disturbance is moving northeast
across western Montana this afternoon which caused the strong winds
today. Weaker disturbances will impact northwest Utah and southwest
Wyoming through the next couple of days but winds are expected to be
Farther south and east a monsoonal surge is under performing so far
as thunderstorms have been few and far between. The air mass is
remaining rather stable despite the increase in moisture.
Consequently, although some thunderstorms are expected over the next
few days there are no obvious disturbances moving northward from
Arizona that would concentrate thunderstorm activity over Utah
Tuesday. Have coordinated with the GACC not to issue any RFW
highlights for tomorrow unless a disturbance forms. RH values over
eastern Utah have increased a lot past 24 hrs and are expected to
remain rather high through at least Thursday.
A drier westerly flow will develop over northern Utah Friday and
spread across the region this weekend. Temperatures will remain
above normal in most areas through this weekend as well as low
relative humidity values.
UT...Red Flag Warning until 9 PM MDT this evening for UTZ478>480-
LONG TERM/FIRE WEATHER...Struthwolf
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