Active weather pattern (Napa, Sonoma, Ione: campers, centers, pools)

[BayAreaHillbilly]

At the moment the KMUX radar is back on line (not sure for how long, the NWS say upgrade activities are going on into May). Not much happening yet in this CWA. However, it looks like LA may take a direct hit tonight.

[BayAreaHillbilly]

Getting a little cold front here in the Bay Area. This one probably won't make it past 36 N.

Seems like we're now on about a once a week cadence of typical late spring storms. Of course the jet stream is split, so the odd cut off low further south is still possible.

[DynamoLA]

Apparently La Nina is now done:
Climate Prediction Center: ENSO Diagnostic Discussion

A majority of models predict ENSO-neutral conditions to continue from April-June (AMJ) through the June-August (JJA) season (Fig. 6). However, at least half of the dynamical models predict development of El Niño conditions by JJA. Still, from JJA onward there is considerable forecast uncertainty as to whether ENSO-neutral or El Niño conditions will prevail, due largely to the inability to predict whether the warmer SST will result in the ocean-atmosphere coupling required for a sustained El Niño event. The official forecast calls for ENSO-neutral conditions through JAS, followed by approximately equal chances of Neutral or El Niño conditions for the remainder of the year

[BayAreaHillbilly]

Originally Posted by DynamoLA

Apparently La Nina is now done:
Climate Prediction Center: ENSO Diagnostic Discussion

A majority of models predict ENSO-neutral conditions to continue from April-June (AMJ) through the June-August (JJA) season (Fig. 6). However, at least half of the dynamical models predict development of El Niño conditions by JJA. Still, from JJA onward there is considerable forecast uncertainty as to whether ENSO-neutral or El Niño conditions will prevail, due largely to the inability to predict whether the warmer SST will result in the ocean-atmosphere coupling required for a sustained El Niño event. The official forecast calls for ENSO-neutral conditions through JAS, followed by approximately equal chances of Neutral or El Niño conditions for the remainder of the year

With an overarching negative PDO modulating ENSO, there is definitely a bias towards neutral to La Nina conditions in general. Therefore I think your prog is good.

[BayAreaHillbilly]

There may be no more rain this rainfall year other than whatever SW Monsoon / Tropical systems we get (or in the mountains and deserts, local convection). The robust Siberia Express we had last year is just not coming into place. Ironically that's due to too progressive a pattern for it to set up. There is no long term trough over the Great Basin, occasionally retrograding, like there was last year. The flow is very zonal, not at all meridional as with last year. Put a brick in your toilet tank!

[BayAreaHillbilly]

Seeing some light returns off the coast, and a few in the Sierra. This cut off low is managing to squeeze out a bit of moisture. Another one prog'ed for Th - F, that may also yield a small amount. So all hope is not lost - yet.

[BayAreaHillbilly]

Well system #2 came up dry. However, after the front passed through this AM, a pretty significant Cold Air Advection (CAA) event set up. Winds (NW) are strong enough to impact aviation and needless to say sea conditions are pretty nasty. Bad thing of it is, not only is cold stress impacting ag, so too is dessication.

NWS prog a progressive ridge this weekend then another low early next week. That one is supposed to pull a trough into the Great Basin that is prog'ed to become stationary. Maybe it will retrograde, yielding some late season upslope snow showers in the Eastern Sierra.

[BayAreaHillbilly]

Maybe grasping at straws, but in any case, we'll take whatever we can get. If the system later next week is as cold as the one that came through yesterday there could be low snow for this time of year. That would indeed be good news, perhaps a late kicker to what's left of the snow pack:

MEDIUM RANGE MODEL SOLUTIONS HAVE COME INTO BETTER AGREEMENT CONCERNING THE REMAINDER OF THE WORK WEEK WITH A BROAD UPPER LEVEL TROUGH SETTING UP OVER THE WESTERN STATES. BY WEEK`S END...THE MODELS INDICATE A CUT-OFF LOW DROPPING SOUTH OVER NORTHERN CALIFORNIA. DEPENDING ON HOW THIS LOW TRACKS...THERE COULD BE RAIN CHANCES ACROSS PORTIONS OF OUR CWA NEXT FRIDAY AND SATURDAY IF THESE VERIFY. STAY TUNED.

[BayAreaHillbilly]

The system late this week seems to be drawing a bead on the Eastern Sierra / Tahoe. Caveat - it's mid to late spring and storm tracks are notoriously unpredictable this time of year. Therefore, we are probably talking Eastern Sierra / Tahoe +/- 200 miles.

[BayAreaHillbilly]

Update:

DRY COLD FRONT EXPECTED TO SWEEP SOUTH THROUGH THE AREA THURSDAY NIGHT AND COMPLETELY ERODE MARINE LAYER AS FREEZING LEVEL POTENTIALLY DROPS BELOW 7000 FT. LEANING TOWARD DEEPER ECMWF SOLUTION BUT NUDGED TOWARD GFS MODEL FOR FRIDAY AS MODELS DIVERGE ON UPPER LOW STRENGTH. EVEN THOUGH SYSTEM SHOULD PROVE TO BE DRY FOR CENTRAL COAST...COULD SEE SOME CONVECTIVE BUILDUPS AND A POSSIBLE SHOWER FRIDAY OVER THE INTERIOR MOUNTAINS.


Watch out for dry thunderstorms and, at pass levels and above, winter weather.