NATIONAL WEATHER SERVICE FORECAST DISCUSSION
Area Forecast Discussion
Issued by The National Weather Service
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652
FXUS66 KSTO 232307
AFDSTO

Area Forecast Discussion
National Weather Service Sacramento CA
307 PM PST Fri Feb 23 2018

.SYNOPSIS  
Below normal temperatures will continue. Snow showers possible over the mountains Saturday with additional systems next week bringing more widespread precipitation.
.DISCUSSION  Next system off the B.C. Coast will not be impactful for Norcal, a weak, rather benign (nuisance) wx system. Mostly high clouds expected to increase over the CWA on Sat with some lower cloud ceilings over the Mtns with isolated light snow showers/flurries. Another frosty morning expected on Sat in the Srn Sac Vly, Delta and Nrn SJV under clear skies and strong radiational cooling, while the timing of cloud cover for the Nrn portion of the CWA looks to be around sunrise or a little after, but still a chance of at least patchy frost. Dry weather on Sun will be followed by another wx system on Mon. This system will also be similar to its predecessors, cold with relatively low QPF, and high snow ratios. (Favoring the NBM snow ratios during these colder, low WBZs GOA systems.) However, the Central Valley should see more rainfall than yesterday`s system. NAM Bufkit forecasts around a quarter inch for SAC, and this may be the last shot of rain this month. DTS rainfall for the month remains at zero through today, although SAC Exec had .01" yesterday. Here is the list for the driest Febs for DTS: 1) 0.04 in 1899 2) 0.16 in 1913 3) 0.19 in 1995 4) 0.21 in 1953 5) 0.26 in 1997 & 2013 SPC plume forecasts show about 10-11 inches of snow for the mean at BLU for the Mon system. For now, our forecast is trending toward the Bufkit NAM for BLU with about 8 inches, and about 15-20:1 snow ratios for the Sierra. (The "normal" SLR is about 9:1.) A wide swath of 4 to 8 inches of snow is forecast for zone 69 with isolated 12 inch amounts near the Sierra Crest. The WR US West Coast AR Landfall tool (Probability of IVT) continues to show a lack of moisture, albeit it is not as "bone dry" for the next 16 days as yesterday`s models. However, there remains a lack of significant ARs. What moisture there is will be spilling over the Pac Ridge and basically eroding as it hits the Pac NW and spreads inland into our CWA. (One could make a weak argument that the Mon system may have a little more moisture than what was forecast yesterday.)   March may come in as the "proverbial lion". The Landfall Tool shows a weak plume in the mid latitudes on Day 6 which would be Mar 1st. JHM
.EXTENDED DISCUSSION  (Tuesday THROUGH Friday)   A period of dry weather is expected behind Monday`s winter storm before unsettled conditions return. Scattered showers possible over the northern mountains and Shasta county overnight Tuesday. Otherwise, dry weather for interior NorCal Tuesday and Wednesday. Gusty north winds are possible Tuesday behind the passage of the upper level trough on Monday. Models bring in another winter storm that will impact the area Wednesday night into the early weekend. Widespread precipitation is expected with this system, though forecast details continue to change between model runs this far out. Currently, the heaviest precipitation is forecast for Thursday into early Friday with periods of heavy snow impacts possible for the Sierra passes. HEC
.AVIATION 
VFR conditions next 24 hours. Northerly surface winds 10-15 kts continue thru the Central Valley with gusts 20-25 kts through 0z Saturday.
.STO   WATCHES/WARNINGS/ADVISORIES    
None.   
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