Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Salt Lake City Utah
401 PM MDT Tuesday may 26 2015
Synopsis...a moist and unstable airmass will remain in place
across the region. An upper low moving out of the northern rockies
will impact most of Utah through the remainder of the work week.
Short term (til 06z sat)...a closed low remains over eastern Washington this
afternoon with a west-SW flow over our County Warning Area. Abundant airmass moisture is
in place and a short wave trough rotating through the base of the
upper low is working on this moisture bringing fairly widespread
The wave is over eastern Nevada and is forecast to cross Utah overnight
keeping convection active over the County Warning Area through the evening with isolated
activity lingering past midnight.
The upper low drifts slowly south through Thursday with additional weak
waves rotating through the base of the low kicking off convection
across mainly the north tomorrow into Thursday. It looks like there
could be a peak in the activity Wednesday night into Thursday morning as the
upper trough axis passes.
The southern County Warning Area dries a little later tonight and Wednesday but becomes more
active again on Thursday with the trough axis.
Convection Friday should be less numerous in the northwesterly flow as the
trough shifts east but sufficient moisture and instability will
remain present for at least isolated activity.
Long term (after 06z saturday)...the shortwave trough is expected
to dissipate and exit the region in earnest late Friday through
early Saturday...with a ridge building over the Great Basin through
the day Saturday. Enough moisture will likely linger over the area
to allow for some weak convective development over the higher
terrain Saturday afternoon...but otherwise the weekend should be the
driest period in quite a while for the State of Utah.
Southwesterly flow increases on Sunday and Monday ahead of an
approaching Pacific trough...ushering in the warmest airmass of the
year so far. Continued to slowly warm temperatures for these
days...leaning mostly toward the mex and other extended MOS
products...and still cannot rule out the first 90 degree day for the
Wasatch front or the first 100 degree day for St. George.
The cold front associated with the approaching trough looks to enter
northwest Utah on Monday afternoon...sliding through much of the
northern County Warning Area Monday night or Tuesday. Have maintained the cooling
trend for Tuesday...but temperatures will still remain fairly warm compared
to what was observed for most of the month of may. There is a chance
this front could also initiate some precipitation across the
northern third of the County Warning Area...but the best instability looks to remain
north of the area.
Beyond Tuesday...the GFS and European model (ecmwf) begin to diverge greatly. The GFS
has remained fairly consistent...keeping the trough relatively
progressive and putting the region under warm high pressure again
for mid-week. However...the 12z ec has come up with an extended
solution that looks very similar to the may weather
pattern...stalling the trough over the west and putting northern
Utah back into a wetter weather pattern. No major preference between
these two solutions at the moment...and hopefully the models begin
to converge in the next couple days.
Fire weather...a Pacific low pressure system will maintain a moist
weather pattern through Thursday...with a chance of wetting rain
every day. Coverage of showers and thunderstorms may be highest in
the northern half of Utah...but southern Utah will still see a few
thunderstorms through this period. The storm will exit the region
through the day Friday...with significantly drier and warmer
conditions finally expected for the weekend.
Aviation...northerly winds are expected to prevail at the
slc terminal through about 03z although nearby showers will
temporarily shift the winds. A band of showers and isolated
thunderstorms is expected to move through between 2330z and 0100z.
Ceilings will lower to between 4k and 5k above ground level in this band with a 30
percent chance of visibility lowering below p6sm. Winds will shift back to
south southeast after 03-04z this evening.
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