NZUS99 KGJT 130454 RRA WRKBGB 4/12/2026 AFD --------------------------------------------------------------------- Key Messages --- - A cold front arrives Monday morning, setting up for multiple days of near or below-normal temperatures. - Valley rain and mountain snow is expected beginning Monday and lasting for the majority of the week. - Travel over the mountain passes could be difficult on Tuesday due to slippery and slushy roads. --------------------------------------------------------------------- Discussion - Today - Day 7 --- MONDAY-TUESDAY SYSTEM: Our next system has moved into Northern California this evening, with strong, moist southwesterly flow pushing into eastern Utah and western Colorado. This will keep winds elevated over the next 24-48 hours, as well as advect increasing upper level moisture. Forecast PWATS of 100-150% of normal are expected by mid-day tomorrow, increasing to 150-200% of normal by Tuesday morning. A cold front is expected to reach the region tomorrow, though it looks to stall as the energy in the parent trough splits into a northern-stream trough and southern-stream closed low. This will keep much of the region under pre-frontal southwesterly flow, but notably also keep the surface pressure gradient weaker than initially anticipated. So while winds will be breezy, with gusts up to 35 mph, Wind Advisories appear unneeded. The southern-stream low becomes mobile once more tomorrow night into Tuesday, gradually weakening as it lifts northeast through the area during the day on Tuesday. The surface cold front will push through ahead of the main low, ushering in a much colder airmass. Temperatures will run 5-15 degrees below normal, and snow levels look to lower to 7000-8000 feet. This means accumulating snow at and above pass level, with valley rain showers below. The big question remains how much snow will accumulate, and how impactful it will be. The best forcing moves through during the day Tuesday, meaning that any accumulating snow will be fighting against the high spring sun- angle and the warm surface temperatures. There also remains uncertainties in snow-ratios and QPF. As a result, have opted not to issue any advisories with this package. But if travelling over the mountains on Tuesday, be prepared for sloppy driving conditions. COOLER AND UNSETTLED THROUGH THE WEEK: Wednesday and Thursday look to bring a brief break from the wind and the cooler temperatures, as transient ridging passes through. Temperatures rebound to near or around 5 degrees above normal. However, another system will already be moving into the Pacific Northwest. Model guidance remains bullish on this system bringing another substantial cool-down late week, with blended guidance dropping temperatures back into the 5-15 degrees below normal range. There remains much uncertainty with other factors about this system, such at track, strength, and moisture content. So stay tuned. Taking a look even further out, models look to keep this unsettled pattern in place. --------------------------------------------------------------------- Aviation --- -------------------------------------------------------------------- Fire Weather --- --------------------------------------------------------------------- Hydrology --- ---------------------------------------------------------------------