Sunrise 6:03 AM   Sunset 8:45 PM Moonrise 6:15 PM   Moonset 3:47 AM

  Print   HELP   Reset   Save   Recall  New

FXUS65 KSLC 202210 AFDSLC

Area Forecast Discussion National Weather Service Salt Lake City UT 410 PM MDT Mon May 20 2024

SYNOPSIS
Cooler, more stable conditions will exist across much of the forecast area on Tuesday as a trough begins lifting out of the region. A brief warm period is anticipated in the return flow on Wednesday, however, active weather returns shortly thereafter, bringing cooler conditions and a chance for showers across northern Utah and southwest Wyoming through the first half of the weekend.

.SHORT TERM (Through 12Z/6AM Wednesday)...An upper trough continues to progress through the region this afternoon, bringing an area of showers and isolated thunderstorms focused along the associated cold frontal boundary. Areas of showers behind the frontal boundary remain active, largely due to an upper diffluent region across northern Utah. Much of the shower activity of the day up until this point has been tied to the western half of the forecast area (i.e. where the front has progressed). Meanwhile, the eastern half of Utah has remained very dry at the surface (relative humidity less than 10-15%) and windy.

Tonight, the front continues to move through the southern and eastern portions of the forecast area, helping to keep showers invigorated overnight. Minimal impacts are expected from these showers, however, as isolated thunderstorm will be possible overnight in southern Utah.

Colder, more stable air will be draped over much of the forecast area tomorrow, helping to bring cooler and drier conditions throughout. That said, trailing disturbances in the wake of the trough axis will keep at least isolated to scattered showers in the forecast across northeastern Utah and southwest Wyoming.
Again, very little impacts are expected from these showers.
Temperature-wise, will see much cooler temperatures (10-15 degrees below normal) across the area as a whole tomorrow, with the most significant cooling anticipated across southern and eastern Utah (i.e. areas where the front has not yet progressed as of 1600 MDT Monday).

.LONG TERM (After 12Z/6AM Wednesday), Issued 427 AM MDT...
On Wednesday, a broad longwave trough will extend from the PacNW on into the Midwest, with the local forecast region sitting beneath largely zonal flow to maybe very weak shortwave ridging.
Through the day, a more marked and compact shortwave impulse along with a cold frontal boundary will dig southward from the PacNW.
Most guidance suggests this feature will only begin to impinge upon the northern fringes of the forecast region by the afternoon/evening, yielding a modest uptick in isolated to scattered shower activity. The majority of the region will remain dry, with afternoon high temperatures fairly close to climatological normal for mid to late May.

Wednesday night on into Thursday, the shortwave will graze the northern half of the forecast region and push the cold frontal boundary southward through Utah and southwest Wyoming. Overall, combination of forcing/moisture doesn't look all too impressive, and while a slightly more organized band of precipitation will be possible along the front, generally just expect isolated to scattered shower chances to continue to creep southward into central Utah or so, with the boundary likely stalling somewhere near the I- 70 corridor during the day. Probably the more noticeable impacts will come in the form of gusty prefrontal winds across southern and eastern Utah (afternoon gusts ~25-40 mph), and much cooler temperatures behind the front. To the latter point, afternoon highs behind the front on Thursday are expected to run about 7 to 15 degrees below normal. Around 80% of ensemble members support some sort of trailing impulse moving through on Friday, but with the boundary washing out and limited overall support, mostly anticipate some isolated afternoon diurnal showers over some of the high terrain. Additionally, places which saw frontal passage the prior day will see temperatures rebound several degrees for afternoon highs as the airmass moderates.

Northern stream remains active moving into the weekend, but some uncertainty is noted on the exact flow evolution. Similar to the Thursday system's progression, another somewhat compact shortwave trough and associated frontal boundary will dig towards the northern Rockies from the PacNW. The amplitude of the trough will largely dictate how far south impacts spread, which is made further complicated by potential for some weak phasing with the southern stream (effectively deepening the trough a bit more). As of this forecast package, around 35% of ensemble members show a deeper trough or weak phase scenario, with remaining membership depicting a flatter pattern and more of a grazing system. In both scenarios, nothing at the moment shows much in the way of substantial precipitation chances or cold air intrusion, so forecast includes near to slightly below normal temps Saturday and Sunday along with some isolated to scattered precipitation generally north of the I-70 corridor.

Deterministic and ensemble guidance show good agreement that Monday into midweek should see a ridge start to build into the area, resulting in drier and warmer weather. That said, Memorial Day does still show a bit of uncertainty with about 20% of ensemble members keeping some modest lingering influences from the departing trough, which would allow for maybe some isolated diurnal showers and a slower warmup. Will want to keep an eye on the forecast for any outdoor plans, but trend is at least favorable so far.



AVIATION
KSLC...Northwest winds expected to hold through the majority of the TAF period, with only a period of light and variable winds within the 10-13z window Monday morning. Shower chances increase with isolated potential after 03z this evening, trending scattered and more consistent than not after 16z. Gusty and erratic outflow possible with showers, most likely on Monday. VFR conditions are expected to be maintained with cigs anticipated to remain above 7kft.

REST OF UTAH AND SOUTHWEST WYOMING
A boundary across central Utah will continue to be the focus of high based showers through this evening. Some gusty and erratic outflow winds will be possible near these showers. Areal coverage of showers will increase across northern Utah and southwest Wyoming after 10z coincident with the next storm system. At this time anticipating VFR conditions, though brief reductions are possible in SW Wyoming within a rain/snow mix Monday, as well as mountain obscuration of northern Utah mountains.

FIRE WEATHER
A cold front progressing through Utah today has brought much cooler and wetter conditions across the western half of the state while the eastern half of the area remains under critical fire weather conditions. The cooler airmass will spread over the remainder of the area through the overnight hours, bringing cooler temperatures to eastern Utah. While only minor moistening of the eastern Utah valleys is expected on Tuesday, the western half of the area will see significant drying.

Warm southerly return flow spreads over the region through Wednesday, bringing a warming and drying trend to the area.
Another day of hot, dry, and breezy conditions is expected across mainly the western half of Utah while the eastern half sees more isolated critical fire weather conditions. Another trough looks to drop into the region Wednesday night through Thursday, which will act to at least moderate fire weather conditions through the early weekend. Much of Thursday and Friday will be mostly dry with increasing chances of precipitation on Saturday.

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

Full Color Weather Map

Link to Loop


Other links: GEOS-West     Contential US     Full GOES-East

Salt Lake City, UT,