Scientific Forecaster Discussion
fxus66 ksgx 290402
Area forecast discussion
National Weather Service San Diego California
902 PM PDT Tue Mar 28 2017
locally gusty winds will occur below passes and canyons through
Wednesday, mainly below Cajon Pass. Otherwise, skies will be clear
through Wednesday with a warming trend. Highs will be mostly in the
80s in the valleys by Wednesday, and lower 90s in the lower deserts.
A deep low pressure center will develop over the Great Basin late
Thursday and Friday. It will mean Strong Mountain and desert winds
and cooling. Warmer weather will return over the weekend under weak
high pressure, but low pressure will bring cooling again early next
Discussion...for extreme southwestern California including Orange...
San Diego...western Riverside and southwestern San Bernardino
Skies were mostly clear this evening across the forecast area. The
00z Miramar sounding showed continued warming, and a layer of
easterly winds of 10-15 kts had developed between 3k and 8k feet. This
is a good sign that we will see much warmer weather tomorrow.
Surface pressure gradients were still 2-4 mbs onshore to the lower
deserts at 8 PM PDT, but were accelerating offshore from SW Nevada at
around 6 mbs. Even in wind-prone areas though, peak gusts were below
30 miles per hour.
No changes through Wednesday, but a high wind watch has been issued
for Thu PM for the mts/deserts. Models continue to show a powerful
Spring storm wrapping up over Nevada/Utah Thu night into Fri. Rapidly
falling sfc pressure over Nevada will combine with increasing winds
aloft to pose a high wind potential across eastern portions of the
forecast area. The local WRF and MOS guidance suggest there is at
least a moderate potential for wind gusts exceeding 55 miles per hour with
possible mountain wave activity affecting the lower deserts.
From previous discussion...
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 north/northwest early next week for
cooling, but models are very inconsistent with details as GFS and
especially Gem are stronger with the troughs, but European model (ecmwf) has weak
290330z...local gusty north-NE winds will create pockets of low level wind shear through
and below the passes and canyons. Otherwise mostly clear with
unrestricted vis through Wednesday evening.
no hazardous marine weather is expected through Thursday morning.
Gusty northwest winds 20-25 kt and large combined seas are expected
again late Thursday through Friday.
surf of 3 to 6 feet with occasional higher sets will continue at
times through early next week.
Skywarn activation is not requested. However weather spotters are
encouraged to report significant weather conditions.