Area Forecast Discussion
Issued by NWS Salt Lake City, UT
FXUS65 KSLC 301454
Area Forecast Discussion
National Weather Service Salt Lake City UT
854 AM MDT SAT JUL 30 2016
.SYNOPSIS...High pressure extends from the southern Rockies into
southern California. Moisture rotating around this ridge will
remain across the region through early next week.
Water vapor loop shows ridging over the southwest CONUS with
westerlies to our north. MDCARS wind observations show a 50-95kt
westerly jet across southern Canada and the northern Rockies.
GOES/HRRR/12Z KSLC RAOB indicate the precipitable water value ranges
from 0.35"-0.50" northern mountains to 1.00"-1.50" southern valleys.
Storm coverage will be on the increase today with a combination of
terrain driven storms and additional triggering due to weak waves
propagating across Utah from Nevada.
BUFKIT model forecast soundings show that the sub-cloud layer is
moistening somewhat compared to the last couple of days. So today
should be a hybrid day between dry microburst threat and locally
heavy rainfall threat.
With that in mind increased PoPs as more storms will contain
measurable precipitation. Also increased Sky coverage based on
satellite trends. Lowered MaxT many places due to the cloud
coverage, especially our southeast zones.
The mid level ridge extends from the southern Rockies to srn Ca
early this morning and moisture has spread around this ridge to
cover all but the far nern CWA. A weak short wave trof is noted in
mean layer streamline analysis over srn Ut and this is supported
by fairly extensive cloud cover stretching across the central and
srn mtns ewd across sern Ut. The motion of the scattered weak
echoes on radar also delineate this trof.
Expect scattered showers associated with this trof to persist over
the east thru the morning while isolated storms generated by daytime
heating look to develop over the remainder of the area by noon. The
weak trof is moving out of the CWA by mid aftn with a trailing
portion lingering over the far se. This should serve to limit
convection somewhat in its wake altho it will not eliminate it.
Temps should get hot again across the north as cloud cover should
not be a factor til later in the aftn. Models indicate another weak
wave crosses the CWA overnight tonight and expect this to keep
convection active through the night.
There is less upper support for convection on Sun but the moisture
remains in place and terrain based development is expected. Temps
should finally dip a bit across the north.
The mid level ridge extends wwd across srn Ca and into the ern Pac
on Sun as well and this starts to allow westerlies over the nrn CWA
to start drying out. This will result in less convection on Mon over
the north and allow temps to tick back upwards again. Another weak
wave crosses the CWA on Tue with a little better coverage of
A Pacific Northwest trough passing well north of the area is
expected to bring a weak frontal boundary through northern Utah
Tuesday night/early Wednesday. As a result, maxes over northern Utah
are expected to drop up to 5F between Tuesday and Wednesday. This
front will temporarily allow drier air to move into northern Utah.
However, EC/GFS both indicate the flow becoming more southerly by
Thursday, allowing moisture to rebound. Because of this, have left
scattered afternoon POPs in for southern and eastern portions of the
forecast area for much of the upcoming week. Latest GFS indicates
drier air moving in from the west for the upcoming weekend, but the
drier air is slower to come in the 00Z ECMWF with a more southerly
The most likely time for winds to switch to the northwest at the
SLC terminal is between 19Z and 21Z today. Scattered showers and
thunderstorms will form across northern Utah this afternoon and
evening, with gusty erratic winds as the most likely impact to the
terminal. Lightning, brief heavy rain, and ceilings below 7000
feet are also possible.
Primary concerns revolve around new starts due to lightning. A Red
Flag Warning continues for much of Utah through this evening.
Yesterday`s ERC values were above the 97th percentile for many
stations across central and northern Utah, with areas greater than
the 80th percentile across southern Utah.
Storm coverage will have a noticeable uptick today with a bit less
coverage tomorrow. Though with a moistening sub-cloud later the
chance of wetting rain will be fairly similar both days.
Some of the thunderstorms will contain little rainfall, but gusty
and erratic winds. This combination will not only support new fires,
but also lead to extreme fire behavior.
A slight cooling trend is forecast today into next week, with
greater rh especially southern and eastern Utah. Northwest Utah will
likely dry back into the single digit RH values by mid week.
UT...Red Flag Warning until 10 PM MDT this evening for UTZ492-493-495-
Red Flag Warning until 3 AM MDT Sunday for UTZ478>484-488-489.
For more information from NOAA`s National Weather Service visit...
For frequently asked questions about the Area Forecast Discussion