Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
666 FXUS66 KSTO 222155 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 255 PM PDT Wed May 22 2024 .SYNOPSIS... Warm and dry weather continues. Breezy north winds Thursday. Minor cooling this weekend before warming returns next week. && .DISCUSSION... Another gorgeous, cloudless day today over interior Northern California with breezy winds and Valley temperatures in the upper 70s to mid 80s (as of 1:57pm). Temperatures are running roughly 5 degrees cooler than compared to this time yesterday in the Valley, but remain on track to climb up into the mid-upper 80s. A low pressure system moving across the Pacific Northwest will tighten the pressure gradient resulting in another round of gusty north winds tonight into tomorrow morning. Winds will begin to pick up late tonight in the northern Sac Valley and continue into tomorrow through the rest of the Valley with gusts 20-35 mph. The National Blend of Models (NBM) indicates a 40-70% chance of gusts greater than 30 mph, with the highest probabilities (greater than 60%) between Red Bluff and Vacaville along the I-5 corridor. This wind event will be weaker than the one earlier this week, but it`s still recommended to secure any loose objects and practice fire safety. A descending trough on the back end of this low will reinforce a cooling trend through Saturday and a return of onshore flow by Friday. As the trough digs further south and its axis passes over the Sierra on Friday, daytime heating plus the added forcing may (10-15% chance) result in a few isolated afternoon/evening mountain thunderstorms. Any thunderstorms that develop will be along the Sierra crest and move eastward. && .EXTENDED DISCUSSION (Sunday THROUGH Wednesday)... Cluster Analysis and ensembles have upper-level ridging develop over the Great Basin region through at least mid week next week. This will allow high temperatures to be in the upper 80s to mid 90s for the Valley. The only notable variance in the clusters is the ridge heights (intensity) and how quickly it is shifted eastward with weak shortwaves progged to move through British Columbia/WA late week. Given the location of the ridge axis, some variation of weak west to southwest flow will be overhead late week next week, keeping onshore flow, and thus somewhat limiting the upper-end potential of the NBM forecast highs late week. Even so, the shortwave trough may not influence our apparent weather much late next week, allowing for temperatures to be warmer than currently advertised, especially for areas less likely to be influenced by onshore flow (central/northern Sacramento Valley). The NBM forecast high temperature spread between the 25th and 75th percentiles for Thursday and Friday next week differ by 12-15 degrees. Given these uncertainties, confidence in the temperatures forecast late week isn`t super high, so stay tuned as the forecast gets closer and details become more clear. //Peters && .AVIATION... VFR conditions next 24 hours. Areas of northerly surface wind gusts 15-28 kts develop after 21Z over the northern Sacramento Valley, which will remain overnight tonight and through much of Thursday. Typical onshore winds will reach the southern Sacramento and northern San Joaquin terminals this evening shifting the winds to be more westerly. By tonight, winds will become more north-northwesterly for areas south of the northern Sacramento Valley, remaining mainly below 10-12 knots. An occasional gust to around 20 knots will be possible through tomorrow afternoon. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$