The same data is available at this site. Please update your bookmarks.
Thank you, and we apologize for the inconvenience.
Please send an email to SR-SRH.Webmaster@noaa.gov with any concerns.
243 FXUS66 KSTO 250501 AFDSTO AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SACRAMENTO CA 1001 PM PDT Thu Apr 24 2014 .Synopsis... A weather system will bring a chance of widespread precipitation along with cooler temperatures and lowering snow levels tonight into early Saturday. Potential for isolated thunderstorms on Friday. && .Discussion... Showers continue to increase this evening as upper trough drops south along the coast. A band of strong thunderstorms developed earlier this evening near Chico with plenty of lightning and a few small hail reports. Best shower chances overnight will shift south over the southern Sacramento valley and central Sierra as shown by latest Hrrr run. Have updated forecast to raise pops in these areas overnight. Showers will increase over northern areas towards morning with upper low dropping south. .Previous Discussion (Today through Sunday)... WSW to SWly flow aloft over Norcal moistening as .80+" TPW plume moves onto the Nrn CA coast. Mostly Light precip forecast through most of tonite as the frontal band moves towards the I-80 corridor by around midnight...and well SE of our CWA by early Fri morning. Synoptic scale or larger scale forcing is forecast to increase over Norcal on Fri (per convergence of Q vectors) as short wave and jet energy on the backside of Ern Pac trof digs the trof along the coast during the day. Then...during Friday night into early Sat this energy continues to dig rapidly into Socal. Thus...for our CWA the bulk of the precip is expected on Fri in widespread and bands of heavier showers/storms. Liquid amounts over an inch in the Siernev are possible and up to a third of an inch in the Valley. QPF should then be decreasing from N to S during Fri afternoon and evening. Cloud top enhancement west of the CA coast beginning to occur this afternoon as short wave energy near 40N/135W begins to interact with the moisture plume. This feature moves Ewd tonite and rain or showers should become more widespread over Norcal during the night. Convergence and surface heating along the E side of the coastal range may result in an isolated storm this evening... otherwise decreasing intensity until dynamics increase Fri morning. Heavier precip is expected on Fri as the digging trof will bring colder/unstable air into Norcal...not only lowering snow levels...but resulting in deep convection (showers/thunderstorms). One...snow levels should lower to around around 4000 Nrn mtns to 4500 to 5500 feet over the Siernev on Fri. Two...the best instability and greatest thunderstorm potential looks to be over the central and southern Sacramento valley in deference to the location of the NE quad of the vort max during the 18z-00z Fri time frame. Increasing onshore gradients on Fri will result in Delta Breezes and topographic channeling of the winds on the E side of the Sac vly. Convergence there could be the focus for stronger storms with possibility of hail. Up to nearly a foot of snow is expected over the higher elevations of the Siernev and 5-9 inches or so near pass levels...although melting/settling at this time of year may account for a couple of inches less accumulation. Greatest snowfall amounts expected to be from the I-80/Hwy-50 corridor Swd in zone 69 given the track of the short wave energy within the upper trof. This rapidly digging trof maintains a neutral tilt over CA. Forecast hodographs for the valley on Fri are mostly cyclonically curved... not broadly looping and favoring left moving storms with negative helicity. This is not the typical TOR set-up for Norcal...and favors more the hail producing storms given the steep lapse rates forecast with the advection of colder air. As this system moves across the Four-Corners area Sat nite... another short-wave is forecast to bring a chance of light precip mainly over the mtns into Sun morning. By Sun afternoon...ridging should prevail over Norcal with warmer/drier wx. JHM .Extended Discussion (Monday through Thursday) Medium range models amplify EPAC upper ridge through first half of the extended forecast period for dry weather and warming. Amplifying EPAC upper ridge Monday is forecast to shift inland Tue/Wed by the GFS/GEM. The ECMWF-HiRes keeps the ridge axis off the West Coast as it digs an upper low southward through the Great Basin. The GFS/GEM solutions suggest more warming than the Euro which points to breezier conditions Tue/Wed. All point to temperatures well above normal early next week with highs from the mid 80s to near 90 in the Central Valley and upper 60s to lower 80s for the mountains and foothills. Models diverge beyond midweek but all suggest minor cooling as the ridge weakens Thursday, either from an approaching Pacific short wave system or from a backdoor trough dropping in from the east. Thus have lowered temps a few degrees day seven with continued dry. PCH && .Aviation... A cold front system continues to impact NorCal tonight into Friday. For the next 24 hours, valley conditions will generally be VFR except for local MVFR/IFR when showers develop. For the mountains, areas of MVFR/IFR expected with local IFR conditions in heavier showers. Snow levels will lower overnight down to 4500-5500 ft by Friday afternoon. Thunderstorms are possible across the valley and mountains between 12z Fri and 03z Sat. Generally W to S winds in the valley now through Friday with enhanced southerly winds in portions of the valley Fri morning and afternoon with local gusts up to 30 kts between KCIC and KSMF. Mountain winds will be SW with gusts up to 35 kts...locally higher over Sierra ridgetops. JBB && .STO Watches/Warnings/Advisories... winter weather advisory until 5 am pdt saturday above 5000 feet in the west slope northern sierra nevada...western plumas county/lassen park. && $$