Sunrise 6:08 AM   Sunset 8:39 PM Moonrise 9:56 AM   Moonset 12:46 AM

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FXUS65 KSLC 131006 AFDSLC

Area Forecast Discussion National Weather Service Salt Lake City UT 406 AM MDT Mon May 13 2024

SYNOPSIS
A weak storm system will graze northern Utah late this afternoon and into the evening before another system moves through the area Tuesday into Wednesday, bringing less warm and more unsettled conditions. High pressure will return late in the week with a renewed warming and drying trend.

.SHORT TERM (Through 12Z Wednesday)...Seeing clear skies over Utah and southwest Wyoming this morning under the influence of high pressure currently centered near the Utah/Nevada border. Under the influence of the ridge, temperatures across the area will be quite mild, with maxes averaging 10F above seasonal normals. However, The ridge is already starting to flatten as a weak wave moves onshore along the Pacific Northwest coast. This system is on track to graze northern Utah later this afternoon and into the early evening, bringing a cold front into the state. Afternoon convection will be focused along this boundary, and thus primarily confined to areas near the Utah/Idaho border. Given the relatively dry lower levels, gusty outflow winds will be the primary threat with any storms that develop.

The arrival of this initial wave will usher in a period of unsettled weather for the midweek period. Guidance indicates the first wave will be followed by a second grazing wave on Tuesday that will push the frontal boundary into southern Utah. Moisture and instability with the second wave look to be less impressive than the first, which was not particularly impressive in and of itself. Thus, the primary impact will be to make temperatures less warm across northern Utah, with maxes running 5F above seasonal normals.

.LONG TERM (After 12Z Wednesday)...Extended forecast period starts out in a post-frontal environment as Tuesday's trough continues to exit the region. Temperatures cool off by another few degrees across a large majority of Utah and southwest Wyoming. Even though Wednesday will feature some of the "cooler" temperatures of the week, highs will still remain about 2-6 degrees above normal for this time of year (highest anomaly across lower Washington County).
Lingering moisture and mid-level instability draped over the region will help to bring isolated to scattered showers and thunderstorms to higher terrain and adjacent valley areas, with a focus across both the southern and eastern portions of Utah. Minimal impacts are anticipated from these showers, however, a north to northwesterly storm motion could allow a shower to build into a flashy drainage in southern Utah. Thinking the overall probability of this is low (less than 15%) given PWAT values are right around normal for this time of year.

Stabilization of the environment ensues heading through Thursday as high pressure becomes the dominant weather feature over the area.
Generally clear skies and warming temperatures will be the trend through the end of the week, so long as high pressure remains in place. As of right now, models are in good agreement of above normal mid-level heights with a ridge axis to the west (dictating surface high pressure) through at least Friday. Through then, expect above normal temperatures across the area alongside dry conditions.

Thereafter, uncertainty in the forecast increases notably. Models continue to indicate potential for another trough to dive into at least the northern half of the area out of the PacNW region. The biggest uncertainty appears to be whether or not the upstream ridge will expand far enough east to minimize the blow of this potential trough. Trends amongst the ensemble guidance seems to be favoring a weaker trough translating across the northern Rockies region, bringing minimal impacts across our local area. Timing of this occurrence is also a point of contention as some models (~15%)
support troughing over the region by Friday evening with ~85% favoring a ridge. For Saturday, ~50% of ensembles favor a weaker trough with the remaining 50% of ensembles (slightly more) favoring ridging. Needless to say, the most likely high temperature range for the weekend is upward of 8 to 10 degrees for some areas. Have maintained a mostly dry forecast through at least Saturday, with increasing chances (marginally) for precipitation thereafter.

AVIATION
KSLC...VFR conditions are forecast over the KSLC terminal through the valid TAF period. Southerly flow will revert to a northerly flow between 18 and 19Z today, with potential for gusty winds later in the evening as area showers develop.

REST OF UTAH AND SOUTHWEST WYOMING
VFR conditions are expected to prevail across the area, with high based showers developing across far northern Utah, and isolated areas of southern Utah. Area showers will have the potential to generate gusty and erratic outflow winds in excess of 30 mph, but otherwise winds will be generally light and terrain driven.

FIRE WEATHER
High pressure over the Great Basin will flatten this morning as a weak Pacific Northwest storm system grazes northern Utah this afternoon and this evening, bringing through a weak cold front. Scattered showers will accompany the front, primarily over far northern Utah. A second grazing system will push the front into central Utah for Tuesday, and with the passage of a third weak system on Wednesday, the front will move through southern Utah. Overall impact will be to make temperatures gradually less warm through Wednesday, though highs will still be above normal for this time of year. Some showers will be possible, with the best coverage expected over far northern Utah today and across the remainder of the area on Wednesday, but the system will not be accompanied by a lot of moisture, limiting convective development.
High pressure will return beginning Thursday, bringing a warming and drying trend through Saturday.

SLC WATCHES/WARNINGS/ADVISORIES
UT...None.
WY...None.

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