Area Forecast Discussion
Issued by NWS Salt Lake City, UT
FXUS65 KSLC 220126
Area Forecast Discussion
National Weather Service Salt Lake City UT
726 PM MDT SAT MAY 21 2016
.SYNOPSIS...A broad upper level low pressure system will remain
over the western states well into the upcoming week. This low
pressure will maintain periods of unsettled spring like
conditions across the region throughout the week.
Water Vapor loop shows a broad closed low over the Pacific
Northwest. AMDAR 400-200MB wind observations place a 120-140kt
cyclonic jet from Southern California into the Northern Rockies.
GOES/HRRR/00Z KSLC RAOB indicate the precipitable water value
ranges from 0.10"-0.30" Southwest Valleys and mountains to
0.30"-0.50" most valleys.
Let the wind advisory go early as winds were dropping off quickly.
Otherwise given the proximity of the upper level jet, approaching
cold pool instability will be retained overnight in the form of
scattered showers across the North. Snow levels will be around
7500 feet. Kept thunder in for the evening based on activity
currently near the Idaho border, though prospects will wane
quickly after sunset.
The upper low currently centered across eastern Oregon will
maintain a steady northeast track into south- central Canada by
early Sunday. A secondary shortwave diving south along the west
coast will fill in behind the exiting Oregon low, maintaining the
broad but loosely organized mean trough across the interior west
through the upcoming week.
Mostly clear skies earlier today across northwest Utah allowed for
convection to develop quickly early this afternoon. Some
organization noted along the moisture discontinuity north of the
drier air moving north through western Utah. A second area of
organized convection is also forming near the Nevada border in an
area of near 700mb convergence. Outside of an early afternoon
storm over the northern Wasatch Front, convection for the most
part has been short-lived pulse storms. See some potential for the
near 700mb boundary to become more active as it drift east
tonight. This low-level boundary supported by an apparent, albeit
weak shortwave crossing the Sierras and the 130+ knot upper jet
across southwest through northeast Utah should sustain some
convection overnight through early Sunday morning.
Looking at lingering terrain-based convection Sunday afternoon and
evening. The next shortwave diving south along the west coast
Monday will likely eject some moisture along with a weak shortwave
or two across the Great Basin late Monday night through Tuesday
evening. Suspect that the greatest areal coverage for convection
will remain across central and northern Utah through Tuesday
evening, with southern Utah seeing limited activity confined
mainly to the higher terrain.
In the active weather pattern of shortwaves, long range forecast
models continue this trend with a longwave trough settled over the
Western CONUS through much of the upcoming week. Weak temperature
advection will lead temperatures to be changed very little day to
day. Expecting diurnally driven convection day to day with the jet
placement and southwest flow pattern of the trough with embedded
low situated across Nevada and forecast to track eastward over
northern Arizona and southern Utah.
Mid-level moisture content should be sufficient for showers and
thunderstorms to develop and diurnal heating as well as weak dynamic
lift will be important ingredients each day for convection. By late
week, forecast models are in agreement with the low tracking
eastward and becoming absorbed into the mean flow with yet another
cold upper low developing just off the Gulf of Alaska.
.AVIATION...Expect northwesterly winds to continue at the SLC
Terminal through the evening. Winds are expected to shift to the
southeast between 05-07Z, though the wind shift may be delayed as
late as 09Z. Otherwise, there will remain a chance of a shower
overnight which may cause gusty erratic winds along with a
lowering of the ceiling.
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