Weather Service Report


348 
FXUS65 KSLC 300323
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
923 PM MDT FRI JUL 29 2016

.SYNOPSIS...High pressure aloft across the southern Rockies into
southern California will remain in place over the next several
days. Moisture rotating around this ridge will increase across
the region this weekend, then remain in place through early next
week.

&&

.DISCUSSION...Evening water vapor and H5 analysis depict a well
defined mid level ridge over the southern Great Basin region with
center of circulation over southern Nevada. Deeper moisture has
advected northwest into Northern Nevada over the last 12 hours
and a distinct moisture gradient exists stretching from NE Arizona
through Northwest Utah delineating PWAT values in excess of .8
inches to the south and west, and less than .80 inches to the
north and east. Along and southwest of this gradient scattered
high based showers and isolated thunderstorms remain in place this
evening with focused activity over the extreme southwestern
portions of the state. A downward tick in convection is expected
through the remainder of the evening with only isolated coverage
expected over the far south overnight.

Isolated high based showers also nosed into the Wendover area this
evening associated with a very subtle mid level wave transitioning
west out of northern Nevada attm. Outside of brief gusts into the
30 mph range from outflow, not much to note with thIS activity
now, or over the next few hours, as bulk of returns on KMTX are
high based virga.

The aforementioned moisture axis will shift east Saturday
allowing PWAT values to climb above .80 inches areawide, with
values pushing or exceeding 1.25 inches across the southwest.
Vertical profiles in BUFRs do support better instability areawide
and forecast of scattered or better convective activity remains on
track for the peak heating hours. Bulk of these storms will
remain high based and quite dry carrying an elevated potential of 
microburst winds, but will have to start paying attention to
locally heavy rainers across the southwest due to PWAT/Instability
parameters becoming more favorable.

Made only minor updates to PoP/WX/Sky grids to match recent
trends. Previous discussion below.

.PREVIOUS DISCUSSION...The upper level trough settling into the
Pacific Northwest through the northern Rockies Saturday
night/Sunday could bring strong convection to the northern for the
latter half of the weekend. Embedded shortwaves associated with
the main trough will graze far northern Utah Saturday evening,
then again on Sunday, This dynamic support along with a favorable
moisture profile should be sufficient for organized, and possibly
strong, convection with these passing features.

Drier air will begin to move northern Utah/southwest Wyoming early
next week. For the remainder of the state the bulk of the weekend
moisture will remain in place, leading to mostly terrain-based 
convection to begin the week. 

.LONG TERM (AFTER 06Z TUESDAY)...Moisture is forecast to reside
across much of the forecast area at the beginning of the long term
period, as mid level ridging is forecast to reside near the Four
Corners region. An upper low is forecast to quickly translate
eastward through the Pacific Northwest/Northern Rockies region
Tuesday through Tuesday night. The models differ a bit with respect
to how much drying occurs across northern Utah in the wake of this
wave during the midweek period, with the EC more aggressively pushing
drier air southward into Utah, while the GFS is more stubborn in
keeping deeper moisture across a good portion of the CWA.
Regardless, moisture looks to remain in place across southern UT
throughout the upcoming week. Temperatures at the beginning of the
long term period will remain above normal, but with slightly cooler
air behind the passing wave, should see a slight cooling trend
during the latter half of the week. 


&&

.AVIATION...Surface winds at the KSLC terminal are slowly
transitioning from a light northwest to the normal overnight
southeast orientation. Expect this to occur around 04z. Isolated
to widely scattered high based storms will develop around the KSLC
terminal after 18z tomorrow. The primary impact from these will be
gusty and erratic outflow winds in the 20z-03z window.

&&

.FIRE WEATHER...Moisture circulating around the upper high over
the southern Rockies remains concentrated over the southern two-
thirds of Utah this afternoon. This moisture will work north
across the remainder of the state Saturday, leading to scattered
convection across all fire districts this weekend.

For tonight convection will likely not generate more than isolated
wetting rains across southern Utah. The threat for mostly dry
thunderstorms and the associated gusty/erratic winds will keep the
fire danger on the high side down south overnight and well into
Saturday afternoon. Wetting rains may finally become a bit more
common for the south as the air mass continues to moisten down
south late Saturday afternoon and evening. For the north could see
a few dry thunderstorms over the northeast mountains and near the
Nevada border this evening. The increase in moisture Saturday will
lead to increased areal coverage of showers/storms, though the
threat of wetting rains will remain low. Will expand the REd Flag
Warning to cover all zones with critical fuel conditions.

A weather disturbance moving east across the northern Rockies
late Sunday/Monday will draw somewhat drier air into the far
north heading into early next week. For the remainder of the
region moisture will remain in place, leading to the potential of
showers and thunderstorms, mainly terrain-based, into early next
week.

&&

.SLC Watches/Warnings/Advisories...
UT...Red Flag Warning until 10 PM MDT Saturday for FWZ492-493-495-497-
     498.

     Red Flag Warning from 10 AM Saturday to 3 AM MDT Sunday for 
     FWZ478>484-488-489.

WY...None.
&&

$$

DISCUSSION...Merrill
PREVIOUS DISCUSSION...CONGER/SEAMAN

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