Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
416 FXUS66 KSTO 160815 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 115 AM PDT Thu May 16 2024 .SYNOPSIS... Comparatively cooler, but still seasonably warm weather continues through the end of the week with a gradual cooling trend then expected from the weekend into next week. Otherwise, mostly dry and periodically breezy conditions look to persist as well. && .DISCUSSION (Today through Sunday)... Early this morning, quiet weather continues across interior NorCal. West-southwesterly onshore flow is beginning to work through the Valley, aiding the diurnal cooling after the warm weather yesterday. Resultant low temperatures will continue falling into the 50s for most, with portions of the northern Sacramento Valley remaining in the low 60s. A trough currently ejecting out of the Gulf of Alaska toward the Pacific Northwest is already beginning to flatten the large scale ridging that has dominated the weather pattern lately. As broad troughing settles in across the Pacific Northwest and Intermountain West into the weekend, the ridge aloft should continue to retrograde westward. As a result, high temperatures look to fall closer to the mid 80s to low 90s throughout the Valley, while 70s to 80s prevail at higher elevations. Otherwise, diurnally breezy onshore winds are anticipated. Some uncertainty still remains with regards to the exact evolution of the upper level pattern late weekend into next week. A shortwave moving through the broad troughing to the north does look to deepen within the vicinity of interior NorCal on Sunday. At the same time, a closed low, currently sitting over the eastern Pacific, is expected to translate eastward toward the California coast as well. The primary uncertainty still lies in the interaction between these two features, with latest cluster analysis indicating around a 60/40 split on potential solutions (60% remain dry, with 40% showing mountain shower/thunderstorm potential). Regardless of the exact evolution, a gradual cooling trend toward near normal temperatures looks to be ushered in with this pattern shift, beginning on Sunday. && .EXTENDED DISCUSSION (Monday THROUGH Thursday)... While the broad troughing and general shift to southwesterly flow aloft should begin by Sunday, the aforementioned trough interaction looks to occur more on Monday. The current ensemble consensus favors dry weather prevailing into early to mid next week, but there is still around 40% of cluster analysis membership indicating some potential for isolated showers or thunderstorms along the Sierra on Monday. Overall though, the primary impact of the upper level pattern shift at this time looks to be high temperatures holding steady around normal values for mid-May. Moving toward late next week in the extended period, there is a signal for another trough ejecting out of the Gulf of Alaska. With potential for considerably less resistance from ridging aloft, this trough may be able to drop further southward toward NorCal and bring additional cooling and precipitation chances to the region. The exact progression and attendant impacts remain highly uncertain at this time though. && .AVIATION... VFR conditions next 24 hours except local IFR/MVFR ceilings possible vicinity west Delta thru 16Z associated with marine layer stratus (only a 30% chance of extending into the Sacramento area TAF sites). Southwesterly surface wind gusts 25-35 kts continue in the west Delta with local southerly surface wind gusts 15-20 kts in the Sacramento Valley after 22Z, otherwise winds generally less than 12 kts. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$