Area Forecast Discussion
Issued by NWS San Diego, CA

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FXUS66 KSGX 220437 AAA

Area Forecast Discussion
National Weather Service San Diego CA
930 PM PDT Sat May 21 2022

Unseasonably cool weather through Sunday with low clouds and fog
west of the mountains tonight and Sunday morning, but some afternoon
sunshine is expected. Not nearly as windy in the mountains and
deserts today as it was yesterday but westerly winds are expected to
strengthen for Sunday. High pressure aloft will bring a warmer spell
for Monday through Thursday, with Wednesday and Thursday likely
being the warmest days. The marine layer will be much shallower with
less cloud cover during the nights and mornings. Slight cooling is
expected by the end of next week as a low pressure trough moves in
from the Pacific.



Evening Update:

There were no updates needed to the forecast this evening. A deep
marine layer continues to promote widespread stratus across the
coastal basin, stretching inland across the valleys and across the
coastal-facing mountain slopes. Gusty onshore winds continue but not
as strong as what we had seen yesterday.

Previous Discussion (issued 128 PM):

Forecast confidence is moderate to high through next Wednesday as
there is good agreement across model platforms with respect to the
synoptic-scale pattern as well as only modest spread among ensemble
members. After Wednesday, model solutions begin to diverge
significantly. This introduces more uncertainty into the forecast.

An extensive low pressure trough over the western U.S. will continue
to dominate our weather through Sunday. It will maintain the cool,
northwest flow aloft and continue to bring us a deep marine layer
with widespread low clouds west of the mtns tonight into Sun
morning. Sunday will be a little warmer as the airmass modifies but
temperatures will remain generally a few degrees below seasonal
averages. Onshore pressure gradients strengthen again on Sun which
will bring us more gusty west winds in the mtns and deserts. Wind
gusts of up to 45 knots are likely in the wind-prone locations.

Monday through Thursday...An amplified high pressure ridge over the
eastern Pacific will expand and shift eastward, with a north- south
axis becoming centered over the western U.S. on Wednesday. This will
bring a warming trend which peaks on Wed with high temperatures near
seasonal averages at the coast and 10-15 degrees above seasonal
averages in portions of the inland valleys where temps could reach
the mid 90s. Temps in the lower deserts will be in the 101 to 105
degree range. The ridge will also shrink the marine layer, limiting
the low clouds and fog to the coastal areas during the nights and
mornings when patchy dense fog could develop.

Cooler with increasing clouds and breezy conditions again for next
Fri into Saturday as another low pressure trough moves inland to our


220345Z...Stratus with bases 2500-3500 ft MSL and tops to around
5000 ft MSL filling in west of the mountains tonight with coastal
mountain slopes becoming obscured. Bases locally lowering to around
1500 ft MSL with 3-5 SM vis overnight in patchy DZ. Clouds clearing
inland 16-18Z with only partial clearing in the coastal areas. Low
clouds being to spread back inland 23/00-03Z with bases near 1500 ft
MSL. Elsewhere, mostly clear with unrestricted vis through Sunday

W-NW winds across the mountains, desert slopes, and below the San
Gorgonio Pass with sfc gusts 20-35 kt gradually weakening this
evening. Similar winds expected Sunday afternoon and evening. MOD
up/downdrafts possible over and east of the mountains.


No hazardous marine conditions are expected through Thursday.


Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.





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