Area Forecast Discussion
Issued by NWS Salt Lake City, UT
FXUS65 KSLC 251032
Area Forecast Discussion
National Weather Service Salt Lake City UT
432 AM MDT MON JUL 25 2016
.SYNOPSIS...Deepening trough along west coast will turn the flow a
little more southerly across the CWA today into Tuesday. This
trough will weaken and move across the northern Rockies Tuesday
night into Wednesday resulting in a dry westerly flow through
Thursday across CWA. A more moist southwest flow returns this
.SHORT TERM (through 06Z Thursday)...A deepening trough along the
west coast will kick a weak disturbance inland across Nevada
today. Water vapor satellite showing an expansion of deeper
moisture lifting northward over southern and eastern Nevada at
this time. Precipitable water values have increased from near 0.40
of an inch yesterday afternoon over the GSL desert to about 0.70
of an inch now. The GFS seems to be the only model catching onto
this trend so have only slightly increased pops as far north as
the Central Wasatch Mountains this afternoon into this evening but
not in the valleys as a dry sub cloud layer is expected to remain
in place. Have increased cloud cover some as well to Wasatch
mountains and adjacent valleys. The CAPE remains below 125 across
northern CWA so not too worried about strong storms.
Farther south and east the moisture remains a little deeper and
therefore have kept isolated showers in the forecast for today and
Tuesday. The trough along the west coast weakens and moves
eastward across the Northern Rockies early Wednesday. This will
result in a drier westerly flow across the entire CWA by Wednesday
afternoon. Above normal temperatures will continue during this
short term period.
.LONG TERM (After 06z Thursday)...High pressure remains centered
near southern Nevada Wednesday night and is progged to remain in
place through late week. The main difference between the GFS and
EC during the Wednesday night through Friday timeframe is that
the EC bulges the high farther northwest into central California.
This would be a drier solution compared to the GFS which allows a
bit of moisture to spread into southwest Utah around the high
center by late Thursday afternoon.
Even if the GFS solution proves more correct, this is still not an
ideal monsoon pattern and moisture will be limited to the
southwestern part of the forecast area. Have trended the forecast
closer to the drier EC, but did introduce small PoPs for Friday for
a couple of southwest Utah zones. Regardless of the moisture, the
thermal ridge will remain firmly over Utah with H7 temperatures in
the 18-20c range across much of the area. This will keep very
warm temperatures in place through the end of the week.
Models indicate a weak disturbance developing near the high center
will lift across Utah over the weekend. However, this occurs on
Saturday in the GFS and Sunday in the EC. If and when this happens,
the ridge will flatten and shift east and moisture will
increase across the area.
.AVIATION...Light southeast winds will prevail at the SLC terminal
this morning but then will shift to northwest between 19 and 20Z.
A return to southeast winds is expected about 04Z this evening.
.FIRE WEATHER...Some mid level moisture will squirt northward up
along the spine of the Utah mountains today as a weak disturbance
ejects northeast out of the west coast trough. This will bring the
threat of isolated thunderstorms as far north as the Central
Wasatch Mountains and Uintas this afternoon and evening. Meanwhile
enough moisture remains over the eastern and southern portions of
the area for continue isolated showers and thunderstorms today and
Tuesday. A drier westerly flow will set in Wednesday in the wake
of a weak trough moving across the Northern Rockies. Dry and hot
temperatures are expected to prevail Wednesday through Thursday
before the flow aloft returns to a more southwesterly direction
and imports mainly mid and high level moisture into the Great
Basin this weekend which will elevate concerns for dry
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