Scientific Forecaster Discussion
fxus65 kslc 190404
Area forecast discussion
National Weather Service Salt Lake City Utah
1004 PM MDT Mon Jun 18 2018
Synopsis...the upper level low pressure system centered over
Idaho will drift into the northern rockies on Tuesday, then
eventually end up over the plains states midweek. Cool
temperatures with unsettled weather conditions will be confined
to far northern Utah Tuesday. High pressure will strengthen
across the region midweek.
Short term (through 12z thursday)...the broad and well-defined
upper low encompassing the northern half of the western Continental U.S. Will
continue on a northeast track toward the northern rockies Tuesday.
The remnant of this feature will eventually work into the
northern/Central Plains states midweek.
The cool and somewhat unstable air mass at core of this low will
limit precip to far northern portion of Utah Tuesday. A vorticity
lobe rotating through the southern portion of the upper low will
cross far northern Utah later tonight through early Tuesday.
Increasing low-level cold advection associated with the vorticity
lobe will nudge a surface boundary south across northern and
central Utah overnight through Tuesday. Any precip will likely
remain close to the best dynamic support from the passing
vorticity lobe and in close proximity to the cooler air aloft
across far northern Utah. Temperatures across northern and central
Utah will remain below seasonal norms, with temps running at or
above normal to the south of the surface boundary across southern
Building heights to the west of Utah Tuesday night/Wednesday will
bring an end to any precip and push temperatures upward on
Previous long term (after 12z thursday)...short-lived ridging
moves eastward through the forecast area on Thursday, accompanied
by increasing southwesterly flow ahead of a shortwave trough
moving inland. As such, afternoon temps should ramp up on the
Summer solstice to 5-10 degrees above seasonal norms.
Global models remain in confident agreement regarding the movement
of this trough southeastward through the northern rockies, showing
the primary moisture to remain north of the County Warning Area. Have decreased pops
to reflect this trend, while maintaining The Drop in temps into the
weekend. That said, frontal instability will likely promote
convective thunderstorms over the northern mountains on Friday
Models in better agreement about diving a closed low into the area
on the weekend, but the timing and extent of movement are still a
bit nebulous. The European model (ecmwf) keeps the center of the low, and the
accompanying moisture, well north of the Idaho/Utah border, while the GFS
dips into the north/NE region of the County Warning Area. Have maintained slight chance
of pops pending further model agreement. High pressure ridging
begins to build during the beginning of the work week.
Aviation...VFR conditions are expected through tonight at the slc
terminal. Light north winds this evening will turn more to the
northwest and increase a bit behind a weak cold front moving south
across the region later tonight. Winds may briefly turn a light
southeast drainage around 12z to 13z, but shift back to the
northwest around 16z to 17z.
Fire weather...a weakening storm system will provide instability
for some showers and thunderstorms over northern Utah through
Tuesday, with the best coverage near the Utah/Idaho border.
Meanwhile, over southeast Utah gusty southerly winds are combining
with low relative humidity values to result in some severe fire
weather conditions. The winds will start to decrease tomorrow as
the system continues to weaken, so critical fire weather
conditions are not anticipated. High pressure will move in for
Wednesday into Thursday bringing a warming and drying trend before
unsettled conditions return for the upcoming weekend.
Utah...red flag warning until 10 PM MDT this evening for utz484-489-494.
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