I'm not in it for who is better at temperatures. I am in it for these types of events. Who is the most accurate. I'll compare Forecast Discussions. Here is what they have against me.
NWS Area Forecast Discussion.
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES.
LARGE COLD 554 UPPER LOW CENTERED OVER OREGON HAS INCREASED ONSHORE
FLOW AND HAS DEEPENED THE MARINE LAYER TO 4000 FEET. A STRONG SURFACE
LOW PRESSURE WILL DEVELOP AHEAD OF THE LOW OVER NEVADA THIS AFTERNOON
CAUSING GUSTY WEST WINDS OVER THE MOUNTAINS AND DESERTS. WINDS
ALOFT WILL CAUSE THE GUSTY WINDS ON THE THE MOUNTAIN RIDGES AND DOWN
THE DESERT SLOPES THURSDAY AND FRIDAY. THE LOW IS NOW PROGGED TO MOVE
SLOWLY...SO THE BEST CHANCE FOR RAIN AND THUNDERSTORMS WILL WAIT
UNTIL FRIDAY AFTERNOON THROUGH SATURDAY. HOWEVER...THERE WILL REMAIN
A SLIGHT CHANCE OF LIGHT SHOWERS OR DRIZZLE TONIGHT AND THURSDAY
NIGHT DUE TO A 6000 FOOT DEEP MARINE LAYER CAUSED BY THE UPPER LOW.
THE VERY COLD AIR ALOFT WILL CAUSE THE CHANCE OF THUNDERSTORMS AS
THE 560 UPPER LOW CENTER SLOWLY DRIFTS ACROSS SOUTHERN CALIFORNIA
FROM SW TO NE. THE COLD AIR WILL ALLOW SNOW LEVEL TO DROP TO 6000
FEET FRIDAY NIGHT AND SATURDAY. THE LOW DOES NOT HAVE A BIG SOURCE OF
MOISTURE...SO RAINFALL TOTALS WILL BE QUITE VARIABLE RANGING FROM
LIGHT TO UP 3/4 INCH IN ISOLATED LOCATIONS. HEAVIER AMOUNTS ARE
POSSIBLE UNDER ANY THUNDERSTORMS...AND THAT COULD SPELL A PROBLEM FOR
RECENT BURN AREAS IN SBD AND SAN DIEGO MTS. THE LOW EJECTS RAPIDLY
EASTWARD ON SUNDAY...AND VALLEY TEMPS REBOUND INTO THE 80S SUNDAY
THRU WEDNESDAY UNDER HIGH PRESSURE.
.SGX WATCHES/WARNINGS/ADVISORIES...
DENSE FOG ADVISORY IN EFFECT UNTIL 9 AM PDT THIS MORNING...
AND WIND ADVISORY IN EFFECT FROM NOON TODAY TO 11 AM PDT FRIDAY FOR
SAN BERNARDINO COUNTY MOUNTAINS-
RIVERSIDE COUNTY MOUNTAINS-
SAN DIEGO COUNTY MOUNTAINS-
DENSE FOG ADVISORY IN EFFECT UNTIL 9 AM PDT THIS MORNING FOR
SANTA ANA MOUNTAINS AND FOOTHILLS-
WIND ADVISORY IN EFFECT FROM NOON TODAY TO 11 AM PDT FRIDAY FOR
APPLE AND LUCERNE VALLEYS-
COACHELLA VALLEY-
SAN DIEGO COUNTY DESERTS-
OWS Weather Forecast Discussion.
Category - Dynamics include Heavy Rain, Major Winds, and Severe Thunderstorms possible. Upgraded from Category 4 to Category 5 storm. This is a dangerous situation and must not be taken lightly. Flood watches will be issued with this so stay to OWS.
Winter Storm Avery is still very much on track to nail the forecast area Thursday and Friday. I will start out with Thursday. On Thursday Morning before sunrise the center of Avery would be Northwest of San Luis Obispo area. This would put the area under the mid level jet which would aid in shower developments. Thunderstorms are very possible in the area from a -24C 500mb temperature which would create the instability needed. Vorticy advection will add a bonus to this and I don't see how thunderstorms will not form. They should. Small hail is possible with these storms so driving conditions will be hazardous. Areas East of Los Angeles should remain rather dry however some mid level clouds will be with the mid level moisture ahead of Avery and associated jet dynamics.
By Thursday Night Avery would look like a tropical system with structure such as that on satellite. It will look pretty neat and I'll have some archives of those on the post storm discussion of this storm. We will be seeing a major enhancement of vorticy advection for the areas West of Los Angeles after Midnight however with the mid level moisture putting the Inland Empire areas under a dryslot it looks like they will be between moisture fields. Also the vertical velocity patterns would not be strong enough for much of anything but watching this very closely on the next forecast which could alter this. The rest of the forecast area such as Santa Barbara and Vandenberg will have low level vertical velocity/ vort advection / and instability would create thunderstorms in the areas, especially South, and offshore.
By Friday Avery takes a negative tilt which is always good for wicked weather. By the Morning, Avery looks to lose some of it's low level rotation. This would be good for a spiral like band to come into the forecast area from the Channel Islands Vicinity. What I am trying to say is it looks a bit more than just hit and miss showers and thunderstorms. It looks like a full on spiral band type event like a hurricane. Certainly very impressive if this unfolds this way. This band would make it into the Ventura area by the Afternoon bringing showers and thunderstorms to the area with heavy rain. Tehachapi areas would stay drier than the coastal areas as moisture is not very plentiful there at this time but will be later. Being the southerly flow and jet dynamics would be over the areas East of Los Angeles there will be the chance for your action to start there during the Afternoon and increase into the Evening as more moisture and dynamics work their way in.
Snow level Friday would be around 9,000 Feet for the Ventura County Mountains, 8,000 - 7,500 Feet for Big Bear for the dry air in place, 8,000 Feet over the rim, 7,000 Feet Los Angeles County Mountains, 8,000 to 7,000 Feet for the Tehachapi Mountains areas, and 10,000 to 9,000 Feet over the Riverside County Mountains.
By Friday Night the fun really starts for the Los Angeles, Orange County, Inland Empire and Mountain areas nearby as the main dynamics of Avery come in. The main show will be the spiral like band ejecting out which would be in the Los Angeles area by 9pm. This band will satisfy the want for thunderstorms as it will be associated with a very good chance of a light show. These thunderstorms will be driven by a vorticy advection almost too powerful for this area and at this time of year. Same goes with the cold air aloft. I've never in my 10 years of forecasting seen such cold temperatures in September at 18,000 Feet here. The mid level jet will be East of the area however the upper jet will be over the area. A jet streak North of the Inland Empire would make the areas South of the High Desert into the coastal LA/OC/SD areas having thunderstorms as they will be in the upper divergence section of this storm. Favorable jet dynamics and instability will be enough for the mention of tornadoes into Southern California. Yes, I know it sounds crazy but right now it looks like the chance of tornadoes are there. A rare upper level jet will aid the shear positive enough for tornadoes. Waterspouts will be a very good bet as well and all boaters must take this note. It is possible that the OWS Tornado and Severe Thunderstorm Watch will be issued with is so stay tuned. Too much to talk about now so I'll leave it there. For the Vandenberg areas, subsidence on the backside of the storm system would clear out showers and thunderstorms over the night. Thunderstorms will increase over the LA/OC/IE/SD/Mountain/Desert areas night into sunrise Saturday Morning where after then we should clear out the showers and thunderstorms to the Northeast forecast area.
Snow Level Friday Night be 8,000 Feet over the Ventura County Mountains, 7,500 Feet Tehachapi Mountains, 8,000 Feet for the Los Angeles County Mountains, 8,000 Feet for the San Bernardino Mountains, and 8,000 Feet for the Riverside County Mountains. Snow levels can lower a couple thousand to a few thousand feet in the more powerful thunderstorms so take note of the elevation when hitting one overnight. Because of the path of this and associated band, I am inclined to say amounts at this time. The amounts are usually given a day before the event so it will probably be given on Thursday for the areas West of Los Angeles but stay tuned.
Winds The approaching Winter Storm Avery is going to produce the Northerly winds offshore Central California. This would create a 10mb difference from the ocean to the deserts. These winds will drive through the Cajon Pass and jet out in the form of advisory level winds during the Afternoon, Evening for the High Deserts. These winds usually die down overnight but do not count on it. OWS formula indicates winds gusting 45-50mph in the High Desert locations based on Avery's mid level jet moving in. Winds will likely be gusting over 50 mph near 55+ mph for the Antelope Valley sections and Tehachapi Mountains. I have issued a High Wind Warning for this cause for strong Southwesterly winds tonight in those areas. Going to add a Wind Advisory for the Riverside/San Bernardino/and San Diego County Mountains as well overnight tonight. The jet would orient itself much better for Mountain Waves to also surface into the lower deserts including the Coachella Valley as 40-50mph gusts.
Thursday Afternoon Avery's mid level jet sticks over the San Diego and Riverside County Mountain for the strongest winds from 40-50 mph in gusts there with stronger gusts surfacing in the deserts and Eastern Mountain slopes known as Mountain Waves. This will need to be monitored for updates so stay in tune to OWS. Wind Advisory level 35-45+ mph gusts will be in the High Desert during this time as well, along with the San Bernardino County Mountains. Take note.
By Thursday Night, the jet decreases a bit as Avery makes it's transition phase toward a negative tilt. This would make the winds drop in gusts 10-15 mph in all areas mentioned above.
By Friday this transition phase would be completed and the jet would be allowed to speed up. This jet is very strong for this time of year. 55-60 mph gusts will be possible across the San Diego, Riverside, and San Bernardino Mountains, with Mountain waves surfacing in the Northern slopes and adjacent Valleys and Desert areas to the orientation of the Mountains.
By Friday Night - Winds will decrease with the Jet moving East of the forecast area.
ONTARIO WEATHER SERVICE...WATCHES / WARNINGS / ADVISORIES = FOUR
High Wind Warnings -
Tehachapi town - OWS High Wind Warning Issued for 50+ mph gusts in spots favored for Southwest winds overnight tonight. Wind advisory level winds would start of your night and end it with stronger winds in OWS warning level as the mid level jet parks overhead.
Antelope Valley including the Eastern slopes of the Tehachapi Mountains - OWS High Wind Warning Issued for 50+ mph gusts overnight tonight as the mid level jet parks overhead. Mountain Waves surfacing near the Northern slopes looks good right now so keeping it at that.
Wind Advisories -
High Desert - OWS Wind Advisory Issued for 30-45 mph gusts starting on the weak advisory level side in the Afternoon and Evening, increasing to the higher Advisory level overnight. Mountain Waves are possible to surface with a bit stronger gusts at times. Mountain Waves would be for the Lucerne Valley areas.
San Diego County Mountains - OWS Wind Advisory Issued for 30-45 mph gusts starting on the weak advisory level side in the Evening, increasing to the higher Advisory level overnight. Mountain Waves are possible to surface with a bit stronger gusts at times. Mountain Waves would be for the Eastern slopes and adjacent low desert areas.
San Bernardino County Mountains - OWS Wind Advisory Issued for 30-45 mph gusts starting on the weak advisory level side in the Evening, increasing to the higher Advisory level overnight. Residents in Southwest wind favored locations will see these winds, and anyone on the peaks will definitely see them.
Riverside County Mountains - OWS Wind Advisory Issued for 30-45 mph gusts starting on the weak advisory level side in the Evening, increasing to the higher Advisory level overnight. Mountain Waves are possible to surface with a bit stronger gusts at times. Mountain Waves would be for North and Eastern slopes including the Coachella Valley.
Coachella Valley - OWS Wind Advisory Issued for 30-45 mph winds at advisory level overnight. Mountain Waves are possible to surface from the Riverside County Mountains with a bit stronger gusts at times in spots.
Blowing Dust Advisory - Blowing Dust Advisory Issued for the fact the winds will be advisory and warning levels for the High/Low Desert areas including the Coachella Valley The Afternoon/Evening/Overnight. Drivers in the Desert can prepare for visibility drop with most of it dropping in the Antelope Valley Overnight. Be careful.
Fire Weather Watch Issued - While humidity and temps will be down, the main concern is the High Winds OWS is forecasting over the night tonight into tomorrow. These will come without precipitation during that period so I am very concerned about the fire situation. If the winds provide a boost of it it's not going to be too good. I have cautioned and issued an Extreme Risk Fire Watch for this chance. For the San Bernardino Mountains and San Diego Mountains fires. Both are at a risk here.
PENDING WATCHES : TORNADO, SEVERE THUNDERSTORM, FLOOD, BLOWING SNOW ADVISORY.
FINAL THOUGHTS: I think they will bust their 35 mph gust forecast on the fawnskin area tonight. SB Mountains would see 40-50mph gusts or so with this system depending where you are. So we will see.
Kevin