Area Forecast Discussion
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FXUS66 KSTO 282144

Area Forecast Discussion
National Weather Service Sacramento CA
244 PM PDT Sun May 28 2017

Warming temperatures for the rest of the holiday weekend followed by a cooldown Tuesday. Isolated afternoon showers or thunderstorms possible over the mountains into mid-week.
1 pm temperatures were about 4-8 degrees warmer than yesterday across much of the valley as the ridging over NorCal strengthens. Daytime highs today should peak in the upper 80s to low 90s for the valley while foothill and mountain regions range mid 60s to mid 80s. Ridge will still be in place on Monday allowing for another 1-2 degrees of warming to the daytime highs. Looking at radar and out our office window, the cumulonimbus clouds are developing this afternoon as we see another round of isolated showers and thunderstorms over the Sierra which we`ll likely see on Monday as well. The ridge over NorCal shifts eastward Monday night into Tuesday as a trough approaches the west coast. This will start a cooling trend in our temperatures as a cooler airmass aloft arrives and onshore flow is enhanced. Tuesday temperatures will drop several degrees putting the valley highs firmly in the 80s as the delta breeze picks up with gusts 25-35 mph. Additional cooling on Wednesday by a few degrees, but the delta breeze won`t be as strong. In addition to the cooling trend, instability over the mountains looks much weaker on Tuesday and Wednesday. Have removed mention of thunderstorms for those days. Shower activity will be minimal on Tuesday...  mainly over the coastal range as the trough moves inland. Overnight Tuesday into Wednesday, chance for showers increases across NorCal over to the Sierra and including portions of the valley with the trough`s eastward track. JBB
.EXTENDED DISCUSSION  (Thursday THROUGH Sunday)   Dry weather now begins Thursday and will last through the weekend as a trough axis shifts east. The 12Z GFS & ECMWF model runs have shifted the following shortwave farther north than yesterday`s runs, resulting in the precipitation chances shifting north of the area as well. Temperatures begin increasing Thursday and will continue to slowly increase through the weekend with Delta highs in the high 80s, valley highs reaching low to mid 90s, and mountain highs mid 60s to 70s. The Delta breeze will diminish slightly by the weekend allowing the southern Sacramento valley highs to reach the low 90s. HEC
VFR conditions expected next 24 hours. Winds generally 10 kts or less for TAF sites with gusts to around 30 knots in vicinity of the Delta.
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