Area Forecast Discussion

KEY MESSAGES

- Anomalous heat persists with daytime highs generally 10 to 20 degrees above normal through Tuesday.

- Gusty southerly winds will develop Tuesday ahead of an approaching storm system. Gusts of 40-50 mph (80% probability) can be expected across western valleys Tuesday afternoon. - An unsettled pattern develops by Wednesday as a trough and associated cold front move in. Snow levels will fall to around 6500 feet, resulting in valley rain and mountain snow, particularly north of I-70/US-50.

- Locally freezing temperatures will be possible (10-40% chance) Thursday through Saturday morning at some valleys of western and central Utah, the western Uinta Basin, and portions of eastern Box Elder County where sensitive early season agricultural growth may be underway.

DISCUSSION

Evening synoptic analysis shows ridging building into the Rockies while a broad trough gradually approaches the US Pacific coast. Combination of the ridge influence and increasing southwesterly flow between the two features has resulted in a noticeable uptick in temperatures compared to yesterday, with daytime highs around 5-10 degrees above normal. Mid/upper level moisture advection within the southwesterly flow is also resulting in some partly to mostly cloudy skies, but overall an arguably pleasant spring day. While gradually clearing skies and calm conditions will support good radiative cooling overnight again, overnight lows will generally be around 5-10 degrees above the prior night, and widespread impactful freezing temperatures are not anticipated.

Monday and Tuesday will see deep southwesterly flow continue to increase, driving temperatures further upward into the 10-20 degrees above seasonal normal range. A very subtle upper level trough shifting through in combination with meager moisture advection will result in some isolated afternoon showers along some of the higher terrain, but otherwise anticipate most locations to remain dry. South to southwesterly gusts will also increase, likely becoming maximized on Tuesday as the broad trough nears. There is approximately an 80% chance of wind gusts in the 40-50 mph range Tuesday afternoon across western Utah valleys, and especially portions of the West Desert. Locally gusty conditions may continue Wednesday ahead of the front, dependent on the exact frontal timing. Eastern Utah and southwest Wyoming would be most likely to see these gusty conditions maintained.

General model consensus supports the front advancing into Utah ahead of the trough Tuesday night into the day Wednesday. Precipitation chances will increase as the front moves in, with potential for a few thunderstorms as destabilization increases through the day. Isolated to scattered shower chances are then maintained through Friday or so as embedded impulses within the broad cyclonic flow of the trough pivot through. By later Wednesday the trough's eastward trajectory would likely start to support more west to northwesterly flow, which may lead to some locally higher precipitation at favored high terrain. Overall, moisture associated with this system is expected to favor the northern half of the area, primarily from around I-70/US-50 northward. Snow levels will be around 7500 feet ahead of the front, falling closer to 6000-6500 feet behind it. As such, generally expect precipitation in the form of valley rain and modest mountain snow.

While not anticipated to be as cold as the system from the prior week, cooler air will result in temperatures falling back to below normal. 75th to 25th percentile 700 mb temps generally look to be in the -3C to -7C range across the area, with the most uncertainty noted in the southward extent to the cold air as the trough swirls in. With enough clearing and if winds can settle enough, this once again will result in potential for some locally freezing temperatures in areas that may be undergoing early season agricultural growth. The degree of clearing seems to be the biggest question, with winds most likely to relax more in sheltered valley areas. Currently, there is around a 10-40% chance of a period of freezing temperatures Thursday, Friday, and Saturday morning in some western/central Utah valleys and portions of the western Uinta Basin and eastern Box Elder County.

Ensembles still maintain support for some continuation of the cooler unsettled pattern into the weekend. Details are still a bit uncertain though as it appears it would to a degree be a result of a southern stream shortwave pushing inland and interacting with the slowly departing trough, and any extra lobe it may try and break off. In any case though, both the 6-10 day and 8-14 day CPC outlooks show favorable odds for above normal precipitation, supporting that the return of strong ridging is at least unlikely for the next bit.

AVIATION...KSLC

VFR conditions prevail at KSLC through the TAF period, with a persistent high level cloud deck. Typical light southeasterly winds will continue through around 19z before switching more southwesterly. Increased southwest breezes are expected to develop after 22z, with gusts to 20kt possible through the evening.

REST OF UTAH AND SOUTHWEST WYOMING

VFR conditions prevail for all regional terminals. Across the airspace, a persistent mid to high level cloud deck will prevail through Monday. Overall light, terrain driven winds are expected areawide overnight with enhanced southwesterly breezes with gusts to 20kt for all terminals developing Monday afternoon.

SLC WATCHES / WARNINGS / ADVISORIES

UT...None. WY...None.