Area Forecast Discussion
Issued by NWS Salt Lake City, UT
FXUS65 KSLC 161046
Area Forecast Discussion
National Weather Service Salt Lake City UT
346 AM MST Mon Jan 16 2017
.SYNOPSIS...High pressure aloft will settle over the Great Basin
for the first half of the week. A return to an active weather
pattern will occur late in the week.
.SHORT TERM (THROUGH 12Z THURSDAY)...
Water Vapor satellite shows the last storm over the Plains, while
a shear axis is currently crossing over Utah. A ridge is building
into the West Coast. 400-200mb MDCARS wind observations place a
90-115kt anticyclonic jet from British Columbia, over the Northern
Rockies, Western Great Basin and central California. GOES/SLC 00Z
RAOB/HRRR indicate that precipitable water values vary from
0.05"-0.10" northern mountains to 0.30"-0.50" southern valleys.
There is a 12mb pressure gradient across the state which may
support pockets of gusty north winds for canyon areas of southern
Utah into tonight. There is a potential that speeds will touch
advisory criteria (45 mph) for a time across outlying Dixie
areas. On the backside of the previous storm system, 700mb flow
strengthens up to 30kts with a period of cold advection today.
The other issue in the short term comes in the way of stratus,
fog and urban haze with an inversion in place. 00Z KSLC RAOB
placed the base of the 2.5C inversion is near 795mb.
Models have been having problems maintaining the stratus deck
seen across the lower elevations of the entire region. Decided to
go persistence and pessimistic, keeping cloudy conditions in the
forecast through the short term period. The 4km NAM seems to have
the best grasp of the stratus.
Finally, air quality will continue to decline into midweek with
the inversion in place and more activity during the workweek.
Will keep on mentioning the urban haze through midweek.
.LONG TERM (AFTER 12Z THURSDAY)...
Very active pattern setting up for the long term portion of the
forecast with multiple storms expected to impact at least portions
of Utah through Monday. By Thursday afternoon, a screaming 200kt
jet max will be offshore the Pacific Coast. A digging shortwave
trough will move into central/southern California Thursday
afternoon and then gradually weaken as it crosses the Interior
West. While this system shows little mid-level baroclinicity, a
notable wind shift and associated development of modest mid-level
cold air advection is noted. More than sufficient forcing should
be in place for a period of precipitation for much of the state
Thursday afternoon into Friday morning.
Ahead of the wind shift, southwesterly flow and associated warm air
advection may increase snow levels to near 5000 feet Thursday
afternoon, but these should fall back to valley floors by late
The previously mentioned jet max will start to focus on the Desert
Southwest Friday evening. Favorable jet dynamics...decent mid-level
moisture and PVA ahead of the next shortwave should provide more
than enough lift for precipitation Friday evening into Saturday
across much of Utah, starting from the southwest and spreading
northeast by Saturday morning. Global model guidance continues to
indicate this storm would be colder with snow down to valley floors
except St. George proper.
A period of shortwave ridging is currently expected to move across
the Great Basin Sunday before another storm takes aim on the area.
Biggest takeaway is a long period of active weather is again
forecast for Utah, with above normal precipitation and near normal
Stratus continues to persist at the SLC terminal this morning.
Ceilings have remained between about 1800-2200 feet AGL overnight.
Expect this to continue through the day, though there is 20
percent chance the stratus will start to break up this afternoon.
Northerly winds will continue through the day as well.
For more information from NOAA`s National Weather Service visit...
For frequently asked questions about the Area Forecast Discussion