FXUS65 KSLC 190847

AFDSLC



Area Forecast Discussion

National Weather Service Salt Lake City UT

247 AM MDT Tue Aug 19 2025



.SYNOPSIS...High pressure will bring a warming and drying trend 

to the region through Tuesday. A monsoon surge will begin as early

as Wednesday and continue through at least early next week. 



&&



.DISCUSSION...A nearly 600dam ridge will set up across the Four 

Corners area today, bringing a very hot, dry airmass to the

region. While monsoonal moisture is pinned to the Arizona/Mexico

border at the current time, this moisture will quickly advect

around the ridge into the western Great Basin later today and

begin to spread into the mid-levels over Utah by Wednesday. 



This will not dial back the heat though for Wednesday, as

temperatures warm to near record to record levels across the

region. Sufficient instability exists for at least a few isolated

high-based thunderstorms across northwestern Utah as well as the

southern mountains. These high-based thunderstorms will bring the

attendant threat of gusty and erratic microburst winds.



By Thursday, deep moisture advection will continue and storms will

become more widespread across the state. Thursday's convection

will likely be a mix of wet and dry thunderstorms as the column

moistens...or in reality for most...trend toward actually seeing 

precipitation at the surface. The Weather Prediction Center has

outlooked portions of southern Utah in a marginal risk (at least

5% chance) for flash flood guidance to be exceeded across 

southern Utah Thursday afternoon. 



Even with the moisture increasing across southern Utah,

temperatures will be in the 105-108 range across lower Washington

County and Zion National Park Thursday, and closer to 102 to 105

for lower portions of Glen Canyon National Rec Area. Overnight

lows will creep up to near to above 80F Thursday morning and

Friday morning. In coordination with WFO Las Vegas, issued an

Extreme Heat Watch for both Zion and lower Washington County for

Thursday...and this threat may extend into Friday. Held off on

Glen Canyon after coordination with WFO Flagstaff as confidence

isn't quite as high to warrant issuance at this time.



By Friday, PW values will meet or exceed the 90th percentile

across the bulk of the region, and exceeding 200% of normal by 

Saturday. With a persistent monsoon circulation in place through 

at least early next week, anticipate a daily increased threat of 

flash flooding through the period. After an extended period of no 

measurable precipitation across large portions of the state (KSLC 

hasn't seen measurable precipitation since July 4), the rain will 

be a welcome relief to high evaporative demand across the state. 



&&



.AVIATION...KSLC...VFR conditions prevail under clear and dry 

conditions at the KSLC terminal through the period. Winds are 

expected to remain generally light, with southeasterly winds this 

morning transitioning to the northwest around 19z. 



.REST OF UTAH AND SOUTHWEST WYOMING...Winds remain generally 

light and diurnally driven at all regional terminals. Clear skies 

prevail areawide this morning. Cumulus buildups are expected 

across the high terrain of southern Utah, and some isolated 

convection is possible across far northwest Utah this afternoon. 

Otherwise, conditions remain generally dry and clear across the 

remainder of the airspace.



&&



.FIRE WEATHER...Hotter, drier conditions will be the rule across 

the region today as high pressure moves into the area. Mid-level 

moisture due to southerly flow around this ridge will increase 

Wednesday, with high-based thunderstorms possible across the 

southern mountains and northwestern Utah Wednesday afternoon and 

evening. Strong, gusty microburst winds will be possible with 

these thunderstorms. 



Moisture will deepen through the atmosphere Thursday into Friday,

with thunderstorms transitioning from mainly dry to mainly wet 

through this time. The chances of wetting rain will remain 

elevated through the weekend and into early next week as this 

longer duration monsoon surge continues. 



&&



.SLC WATCHES/WARNINGS/ADVISORIES...

UT...Extreme Heat Watch from Thursday afternoon through Thursday 

     evening for UTZ123-124.



WY...None.

&&



$$



Kruse/Whitlam



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