Sprinklers or Not?

Synopsis: Easterly waves working their way over us created some thick, high clouds Monday afternoon.  This helped to knock down temperatures from Sunday’s highs.  Periods of high clouds are likely again on Tuesday with moist layers between 600-400mb (15-20,000 feet).  Also, it may feel even a bit more muggy on Tuesday as lower level moisture is projected to enter our region.  Another easterly wave is likely on Wednesday morning.  However, this one will be farther to the east.  Either way, afternoon thundershowers are possible for the mountains and deserts.  A strong subsidence inversion (strength:  5-6°C; Base height:1,200 ft) will maintain a shallow marine layer near the surface.  Overnight low clouds will be confined to the coasts and will quickly leave during the morning.  Daytime highs should run near 80°F for inland areas (but, could penetrate mid-80’s if high clouds dissipate).  On Friday, a southwesterly flow will dry out all layers.  This weekend (July 5-6th) could be much cooler.

Synopsis: We reached 78°F on Friday.  A trough is digging down over central California Friday evening.  This has contributed to an onshore push and a deepening of the marine layer.  Further moistening and deepening is anticipated.

Saturday: Cloudy with drizzle possible during the morning hours.  Afternoon clearing is unlikely, especially along the coast.  Highs will depend on the persistance of the cloud cover.  We may not break 70°F on Saturday.

Sunday: Late morning clearing is likely with temps into the 70’s.

Subsidence inversion has strengthened from Thursday:  Base: 1,700ft; Strength:  11C; Cloud depth: 800ft.  So, a slower burnoff is possible Friday morning.  Clearing slightly later than Thursday (after 10am, inland) with high temperatures near 76-78°F (inland Irvine).  An onshore push begins Friday evening with more persistant clouds for Saturday and cooler temperatures.

Synopsis: A subsidence inversion is evident in Thursday morning’s sounding.  Inversion base at 925mb (2,500ft) with a strength of 7°C.  Substantial drying aloft compared to Wednesday with a weak northeast to north flow at all levels.  The solid cloud deck (approx 900ft deep) will quickly be removed later Thursday morning.  Temperatures were bumped up during the early morning hours from the offshore flow.  Highs Thursday should reach into the upper 70’s with an afternoon sea breeze.

Synopsis: The marine layer has shoaled compared to yesterday from 6,500ft to 4,000ft (900mb).  We are now under a large and substantial area of subsidence (seen below).  This area of subsidence is the result of a equatorward fetch east of a large ridge over the eastern Pacific and the backside of the trough:

This area of subsidence is projected to increase in intensity Wednesday.  To our east, a different story applies.  Although, the atmosphere has dried at most levels since yesterday west of the mountains, moist layers still exist to the east.  Some thundershowers are likely during the late afternoon over the deserts to our east.  The low clouds will clear by mid-morning.  A weak offshore flow will persist with stagnant conditions.  Afternoon highs could approach 80° for inland Irvine.

Synopsis: This morning’s sounding shows a cloud layer at 600mb (14,000ft circled in red) and cloud layer seen outside.  Should see a well-mixed layer to 925mb (drawn on the sounding (temperature in red, mixing ratio in green)).  Surface based CAPE for this afternoon is limited given this morning’s sounding and the predicted warming aloft.  However, afternoon elevated CAPE over the mountains is possible.  This combined with slow winds and moderate moisture aloft should result in some cumulonimbus clouds over our mountains this afternoon.

Forecast: Morning low clouds lifting and clearing.  Afternoon sun with some high clouds and highs in the upper 70’s.  Afternoon convection over the mountains and deserts should be visible.  The tops of these clouds could drift over the valleys and coastal regions at sunset.  I cannot rule out the possibility of some brief sprinkles or shower this afternoon or evening.

12Z 06/16 San Diego Sounding

UPDATE (Tuesday at 4pm):  Convection over the deserts on Tuesday afternoon as expected (seen below).

Synopsis: Most of the moisture is staying off the coast.  The trough will deepen overnight with some upper level dynamics in place for Tuesday morning.  Drizzle or a light shower is possible Tuesday morning. Tuesday afternoon, convection over our local mountains could create some isolated showers.  Some of these storms will be visible during the late afternoon.  AN OFFSHORE FLOW WILL CREATE A TEMPERATURE SPIKE ON WEDNESDAY.  Temperatures could surge well into the 80’s with dry conditions.

Synopsis: Yet another shortwave (Red number 1 below) will pass overhead Sunday night and Monday morning.  Low clouds will return later Sunday night (after midnight) and should persist into late Monday morning.  Temperatures will drop into the upper 50’s Monday morning with calm conditions.  Slightly cooler on Monday with highs near 70° for inland Irvine.  A stronger shortwave (red number 2) comes through on Monday night/Tuesday morning.  Along with it, plenty of moisture and some upper level dynamics.  So, looks like we could get some drizzle or light rain overnight Monday/early Tuesday.  A return to warmer weather is likely beginning on Thursday.

Mostly cloudy skies during the morning.  Early morning convection will result in thicker clouds with areas of blue skies.  So, partly cloudy during the late morning.  Mostly clear during the afternoon with clouds against the foothills.  Slightly warmer than Saturday.

Friday night: Mostly cloudy with a chance of drizzle or light rain Friday night.

Saturday: Drizzle possible during the early morning hours with mostly cloudy skies.  Clearing to partly cloudy skies during the morning.  The inversion is very weak with a deep moist layer extending above 850mb (5000ft).  This will keep clouds broken in most areas.  Warmer temperatures are on tap for Saturday (highs in the mid to upper 70’s for Northpark).  Increasing clouds Saturday evening.