Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Salt Lake City Utah
454 PM MST sun Feb 1 2015
Synopsis...a moist west northwest flow will develop across the
northern Great Basin for the first half of the week.
Discussion...an upper ridge remains over the West Coast this
afternoon with a northwesterly flow over the County Warning Area. Middle and high clouds
streaming through the ridge have reached the northwestern County Warning Area and should
It appears the last of the stratus in the central and eastern County Warning Area
has dissipated as of middle afternoon and do not expect it to
redevelop tonight. Also do not expect any fog in the northern valleys
due to increasing cloud cover.
The upstream ridge remains more or less in place through Wednesday but
a series of weak short wave troughs will move over it spreading a
fairly moist airmass into the northern County Warning Area. 12z models were very
generous with storm total quantitative precipitation forecast for the Wasatch mountains with the GFS up
to about 1.5 inches water and the NAM near 2.5 inches. Both of
these backed off about .5 inch in their 18z runs and think this
trend is correct in spite of the moist airmass as the jet stays to
our north and dynamics will be weak over our County Warning Area.
Have opted to hold off on any winter weather highlights at this
time as these amounts will be distributed over an extended time
frame and impacts will probably not be sustained.
The upstream ridge finally starts to shift inland Wednesday and precipitation
begins to taper off.
Long term (after 00z thursday)...the tail end of an embedded
shortwave in northwest flow across the County Warning Area will bring a few showers
to the mountains of far northern Utah at the beginning of the
long term forecast period. The ridge is then expected to gradually
shift eastward through the end of the week.
The 12z GFS and 12z ec differ a bit with the degree of amplification
of the ridge over the intermountain region. The 12z GFS is a bit
less amplified and allows several weak disturbances embedded in the
flow around the top of the ridge to impact far northern Utah Friday.
The 12z ec is a bit drier as the track of these disturbances is
further north impacting Idaho rather than northern Utah.
Much of the model guidance is fairly consistent with the next
wave...forecast to move through the area Saturday. This wave is
fairly strong but quite progressive in the westerly flow. It should
bring a quick shot of precipitation to the northern half of Utah.
Another wave embedded in the zonal flow is expected to impact the
area later in the weekend through early next week. The 12z model
suite varies quite a bit in timing and location of this wave...so
just trended probability of precipitation up above climatology for the north.
Aviation...west to northwest winds are expected at the slc terminal
through the evening...shifting back to the southeast between 02-04z.
Aviation...southerly winds are expected at the slc terminal
through the taf period although there is a chance of a switch to
northwest Monday afternoon. Ceilings will remain around 8000 feet above ground level or
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