Area Forecast Discussion
Issued by NWS San Diego, CA

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289
FXUS66 KSGX 281652
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
930 AM PDT Tue Mar 28 2017

.SYNOPSIS...
Low pressure aloft will continue to move east through Arizona today
and combine with surface high pressure building over Nevada to
produce gusty north winds in some of the mountains and valleys
through early this afternoon. Skies will be clear through Wednesday
with a warming trend, with highs mostly in the 80s in the valleys by
Wednesday and lower 90s in the lower deserts. Low pressure aloft
will move by to the northeast Thursday and Friday and bring cooling
along with gusty west winds to the mountains and deserts Thursday
with some northerly winds developing Friday. Warmer weather will
return over the weekend under weak high pressure, but low pressure
will bring cooling again early next week.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

There were patchy low clouds and fog until around 8 AM in western
San Diego County, but otherwise skies were clear. Locally gusty
north winds were occurring over and below the San Bernardino
Mountains and Santa Ana Mountains, with a few gusts in the 35-50 MPH
range. Peak gust was at Snow Peak in San Bernardino County around 3
AM at 61 MPH. HRRR model shows a gradual decrease in the winds
between 11 AM and 3 PM, though high-res models show some increase
again in the winds overnight, though mostly localized below Cajon
Pass and just downwind from the San Bernardino County crests. Winds
tonight should mostly stay below wind advisory criteria with gusts
to around 40 MPH in windier spots.

High pressure aloft will build over the east Pacific with a moderate
ridge extending to Nevada and Utah by Wednesday. Strong moist zonal
flow will occur over the Pacific Northwest. Due to clear skies and a
warm profile, with 850 MB temps rising to around 15 C, surface
temperatures will respond and reach levels of 7-15 deg F above
normal Wednesday. Onshore flow will start to develop again Wednesday
afternoon which could bring a few low clouds or fog to the coast
Wednesday night, though this is more likely Thursday night after a
period of stronger onshore flow from the next low pressure system
coming down from the north. This low will track from far northern
California Thursday southeast to Arizona Friday.
Height/temperature/pressure gradients will be tight on the
west/southwest side of the low and result in strong west winds in
the mountains and deserts Thursday afternoon/evening. High-res
models are indicating strong winds could make it into populated
parts of the Coachella Valley, which is more typical with synoptic
scale winds versus mountain wave winds. Northerly winds, similar to
those of this morning, could form Friday as pressure gradients turn
offshore. With the upper low nearby, temperatures will decrease
Thursday and Friday, with temperatures a little below normal Friday.
With the progressive spring pattern, the upper low, despite being
closed, will move east over the weekend, with warming again over So-
Cal. More troughs could move down from the N/NW early next week for
cooling, but models are very inconsistent with details.

&&

.AVIATION...
281530Z...Clear skies expected today and tonight. Gusty north to
northeast winds 30-45 kts mainly in foothills and adjacent valleys
through about 20Z. LLWS possible at KSNA, KSBD, KPSP, and KONT
when/where winds do not quite surface. Mostly surfacing at these
airports 14-20Z and weakening thereafter.

&&

.MARINE...
A Small Craft Advisory remains in effect through 8 PM this evening.
Although winds will decrease this morning, they will pick up again
this afternoon and evening. Strong winds and large combined seas are
expected again late Thursday through Friday.

&&

.BEACHES...
Surf of 3 to 6 feet with occasional higher sets will continue at
times through early next week.

&&

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

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...Wind Advisory until 2 PM PDT this afternoon for Riverside County
     Mountains-San Bernardino County Mountains-San Bernardino
     and Riverside County Valleys-The Inland Empire-San Gorgonio
     Pass Near Banning-Santa Ana Mountains and Foothills.

PZ...Small Craft Advisory until 8 PM PDT this evening for Coastal
     Waters from San Mateo Point to the Mexican Border and out
     to 30 nm-Waters from San Mateo point to the Mexican Border
     Extending 30 to 60 nm out including San Clemente Island.

&&

$$

PUBLIC...Maxwell
AVIATION/MARINE/BEACHES...Gregoria



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