Scientific Forecaster Discussion
fxus65 kslc 301618
Area forecast discussion
National Weather Service Salt Lake City Utah
1017 am MDT Thu Mar 30 2017
Synopsis...an upper low will develop across the Great Basin
today, then slowly drift east along the Utah Arizona border
tonight through Friday. High pressure will return Saturday,
followed by another cold front early next week.
Discussion...the upstream trough is currently evident on satellite
imagery diving south over California and is accompanied by a potent
cold front which is currently crossing central Nevada. Ahead of this
storm, precipitation has developed across northern Utah given a
combination of increasing upper diffluence, cooling aloft, and warm
temperatures at 700mb. Snow levels remain high with this initial
round of precipitation with 700mb temperature remaining in the -1 to
-2c range. Dual-pol data and bright banding on kmtx support snow
levels around 7500ft. This prefrontal precipitation will continue
spreading into southwest Wyoming, through the uintas, and into
Castle country late this morning into this afternoon.
Winds will increase ahead of the front, strongest across southern
Utah. A Wind Advisory remains in place along the Arizona border.
Considered adding the southwest Utah zone which includes Cedar City
and Milford, but duration will be shorter and increasing cloud cover
and precipitation through the afternoon hours may hinder mixing.
The trough will pinch off into a closed low over Nevada and as it
does so, the cold front will slow and then weaken over Utah this
afternoon and evening. An initial look at the 12z GFS shows the
front making slightly less eastward progress over Utah. Still,
enough of a surface gradient will exist to bring some gusty
postfrontal winds to the western Utah valleys. A Wind Advisory
remains in place for these postfrontal winds across northwest Utah.
Precipitation will increase across western Utah along the boundary
this afternoon. This will be widespread and locally heavy at times
and may contain embedded thunderstorms. With the low center then
tracking across southern Utah tonight into tomorrow, moisture
wrapping around the low will favor southern and portions of eastern
Utah as well as southwest Wyoming, but in particular the I-15
corridor across southwest Utah and adjacent mountains. The coldest
air will be near the low center across southern Utah, and looks to
fall into the 4500-5500ft range. Various going winter weather
highlights cover areas of concern.
Easterly flow across northern Utah developing tonight and maxing out
tomorrow night into Saturday morning is still Worth watching.
Currently, the surface gradient does not appear to be especially
tight, and although 700mb winds are forecast to reach 50kt across
northeast Utah and southwest Wyoming, the lack of any decent cold
advection except for a period Friday night into early Saturday
morning suggest the likelihood for a significant wind event is not
very high at this time. That being said, local gusty winds are still
expected, especially near canyons.
No updates this morning.
Aviation...showers will be moving in the vicinity of the slc
terminal at times this morning, the main impact of these being
occasional periods of erratic winds and ceilings dropping below 7k
feet. Outside of these showers VFR conditions and at times strong
southerly winds will prevail until frontal passage around 22-23z.
Frontal passage should bring a period of MVFR rain and a wind shift to the
Utah...Wind Advisory from 2 PM this afternoon to 9 PM MDT this evening
Winter Storm Warning from 6 PM this evening to 6 am MDT Saturday
Winter Weather Advisory from 6 PM this evening to 6 am MDT
Saturday for utz007-008-010-014.
Wind Advisory from 2 PM this afternoon to 4 am MDT Friday for
Wyoming...Winter Weather Advisory from 3 am Friday to 6 am MDT Saturday
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