Winter Storm and High Wind in Utah, March 5 to 6, 2017

Area Forecast Discussion
National Weather Service Salt Lake City UT
256 AM MST Sun Mar 5 2017

.SYNOPSIS...A very cold Pacific storm system will cross the Great
Basin and northern Rockies through Monday. High pressure aloft
will return to the region by midweek.

&&

.SHORT TERM (THROUGH 00Z WEDNESDAY)...
Water Vapor Satellite shows heights continuing to lower with a
strong and deep closed low along the Pacific Northwest coast.
400-200mb MDCARS wind observations place a 125-150kt cyclonic jet
from the Pacific into northern California and southern Idaho.
GOES/SLC 00Z RAOB/HRRR indicate that precipitable water values
vary from 0.10"-0.15" mountains to 0.25"-0.33" valleys.

Going headlines in good shape. Just a few tweaks. This next storm
is quite energetic, you can see it just by looking at the
Potential Vorticity at 500mb and also a reflection down to 700mb.
This storm is forecast to deepen rapidly as it makes its way
through the upper plains. In fact the RAP has the deepening
cyclone down to 993mb by early this evening!

700mb flow increases to 60kts with 7mb pressure falls and a
modest southerly pressure gradient in place. This will support
widespread 50 mph gusts with gusts around 60 mph across western
Utah.

RAP 850-700mb saturated equivalent potential
temperature/thickness/streamlines indicate the cold front is a
little slower than originally expected. The front nears the
Northwest tip of Utah around 15Z, and finishes the daytime from
south of Wendover to Salt Lake to west of Evanston. It will clear
the rest of the region tonight.

With the slower frontal timing, lowered PoPs out west this
morning. By late afternoon it looks likely for precipitation from
Wendover to Ogden, northward, with lower chances closer to the
surface frontal zone near Salt Lake area. There are low SREF
probabilities for thunder during the day Sunday. But considering
simulated reflectivity structures, have opted to keep a mention in
the forecast.

Post frontal winds should be strong. While MOS guidance for
Wendover and Evanston were not particularly high for winds, with
10mb-12mb/3hr pressure rises, a strong pressure gradient winds
may necessitate a continuation of future wind headlines post
frontal as well, despite 700mb winds only being between 15-20kts.

Quick burst of snow expected tonight with the best period of cold
advection, with snow levels rapidly dropping to the valley floor.
This will thin out Monday as warming takes place aloft and
heights rise, though precipitation lingers due to the passage of a
secondary wave.

One other thing to watch is the potential for additional lake
effect snow late tonight into Monday morning, most likely pointed
toward Davis/Weber counties. BUFKIT forecast soundings adjusted
for a 37F GSL temperature yield around 800j/kg of CAPE with an
equilibrium level near 18kft.

Expecting light rain/snow chances across the far north Tuesday due
to warm advection.

For temperatures, went on the high side today, and went low end of
the guidance tomorrow.

.LONG TERM (AFTER 00Z WEDNESDAY)...
Increasing heights across the region will start the long term
forecast period. Moderate warm air advection will continue into
Wednesday, with 700mb temperatures near -4 to -6C across northern
Utah at 00Z Wednesday, reaching 0 to -2C by 00Z Thursday.

With near zonal flow across northern Utah, a weak disturbance will
cross northern Utah later Tuesday, bringing the potential for light
precipitation across mainly the far northern Utah mountains through
early Wednesday morning.

Another weak disturbance will quickly cross northern Utah in deep
westerly flow Thursday, again bringing the threat of a light
precipitation to mainly the far northern mountains of Utah.

Global models vary significantly after Friday, with the 00Z GFS
bringing the storm track further south and bringing several features
through the state Friday into early next week. Meanwhile, the EC
continues to depict a storm track further north, with much of the
precipitation limited to about I-80 and north. This model to model
consistency issue has been problematic through the past several
runs. For now, leaned toward the drier solution. It should be noted
the Canadian as trended toward the EC solution.

Biggest takeaway remains warm temperatures, averaging 5 to 10 and as
high as 15 degrees above normal through Thursday to Friday with an
unsettled pattern potentially developing by next weekend.

&&

.AVIATION...
Very strong southerly winds are expected to continue at the SLC
terminal through the day, with gusts in excess of 45kts possible.
A strong cold front is expected to cross the terminal between
23-01Z. This will shift winds to the northwest with wind gusts in
excess of 35kts possible for several hours behind the front. Any
rain will quickly change to snow behind the front, with a period
of moderate to potentially heavy snow expected through 03-05Z.
Accumulations on untreated surfaces are expected to range from 2
to 3 inches.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Wind Advisory from noon today to midnight MST tonight for UTZ013-
     014-020.

     Winter Weather Advisory from 5 PM this afternoon to 4 PM MST
     Monday for UTZ009-010-517.

     Winter Storm Warning from 6 AM this morning to 4 PM MST Monday
     for UTZ007-008.

     Winter Weather Advisory from 5 PM this afternoon to noon MST
     Monday for UTZ006.

     High Wind Warning from 8 AM this morning to 9 PM MST this
     evening for UTZ005-015-016.

     Winter Weather Advisory from 5 PM this afternoon to 8 AM MST
     Monday for UTZ003-004.

     Wind Advisory until 9 PM MST this evening for UTZ003-004.

     Winter Weather Advisory from 2 PM this afternoon to 5 PM MST
     Monday for UTZ001-002.

WY...Winter Weather Advisory from 5 PM this afternoon to noon MST
     Monday for WYZ021.

&&

SHORT TERM...Rogowski
LONG TERM/AVIATION...Kruse

For more information from NOAA's National Weather Service visit...
http://weather.gov/saltlakecity

For frequently asked questions about the Area Forecast Discussion
visit...
http://weather.gov/saltlakecity/general/afd_faqs.php

Hazardous Weather Outlook
National Weather Service Salt Lake City UT
250 AM MST Sun Mar 5 2017

UTZ001>016-019>021-517-518-WYZ021-061400-
Cache Valley/Utah Portion-Northern Wasatch Front-
Salt Lake and Tooele Valleys-Southern Wasatch Front-
Great Salt Lake Desert and Mountains-Wasatch Mountain Valleys-
Wasatch Mountains I-80 North-Wasatch Mountains South of I-80-
Western Uinta Mountains-Wasatch Plateau/Book Cliffs-
Western Uinta Basin-Castle Country-San Rafael Swell-
Sanpete/Sevier Valleys-West Central Utah-Southwest Utah-
Utahs Dixie and Zion National Park-South Central Utah-
Glen Canyon Recreation Area/Lake Powell-Central Mountains-
Southern Mountains-Southwest Wyoming-
250 AM MST Sun Mar 5 2017

This Hazardous Weather Outlook is for the western two thirds of
Utah and southwest Wyoming.

.DAY ONE...Today and Tonight

Flooding of fields and residential basements will continue across
low lying mostly agricultural areas of far Northern Utah due to
snowmelt.

Strong gusty southerly winds will increase across portions of the
western outlook area this morning and become widespread this
afternoon as the cold front approaches. The winds will continue
ahead of the front into the evening across the south and east.

Gusty winds will also continue into this evening behind the cold
front across portions of the northern outlook area.

Significant snowfall is expected with this front late this
afternoon through tonight, especially across the northern and
central outlook area, with snow levels falling to the valley
floor quite quickly. Winter driving conditions will impact travel
along most routes across this area at times tonight including
I-80 across most of Utah east into Wyoming, and I-15 from the
Idaho border to near Cove Fort.

.DAYS TWO THROUGH SEVEN...Monday through Saturday

Local residential and agricultural flooding will continue across
low lying areas of far Northern Utah early in the week.

The snow will turn showery late tonight but accumulating snow
showers will persist through Monday across the northern and
central mountains as well as in some of the northern valleys.
Winter driving conditions will continue through Monday morning
along all mountain routes from I-70 northward. Local impacts are
expected on the Monday morning commute along the Wasatch Front,
mainly along secondary routes.

Accumulating snow could persist across portions of the northern
outlook area into Tuesday before ending.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to standard operating procedures.

Rogowski/Kruse

For more information from NOAA/s National Weather Service visit...
http://weather.gov/saltlakecity

For information on potential road travel impacts visit...
http://www.udottraffic.utah.gov/roadweatherforecast.aspx