Los Angeles, CA...San Diego, CA...Long Beach, CA...Santa Ana, CA...Anaheim, CA...
Probabilistic Tornado Graphic
Probability of a tornado within 25 miles of a point. Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Day 1 Tornado Risk
Area (sq. mi.)
Some Larger Population Centers in Risk Area
New Orleans, LA...Baton Rouge, LA...Mobile, AL...Jackson, MS...Metairie, LA...
Houston, TX...Long Beach, CA...Huntington Beach, CA...Oxnard, CA...Oceanside, CA...
Probabilistic Damaging Wind Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point. Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
SPC AC 201243
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0643 AM CST Fri Jan 20 2017
Valid 201300Z - 211200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING
ACROSS THE UPPER TEXAS COAST...AND TONIGHT ACROSS THE LOWER
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
GULF COAST SLIGHT RISK AREA...
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
ALONG THE SOUTHERN CALIFORNIA COAST...
Severe storms will develop this evening and spread across the lower
Mississippi Valley tonight through Saturday morning, with a few
tornadoes, large hail, and damaging winds all possible. Strong
thunderstorms with at least some severe-weather potential are also
possible near the southern California coast this afternoon.
Broad cyclonic flow is now established across much of the contiguous
U.S., as a series of embedded shortwave troughs move from the
Rockies to the MS Valley in advance of a strong mid-upper jet
approaching CA. A broad/diffuse cyclone will be maintained across
the Plains, which will encourage gradual inland progress of the
warm/moist sector across the Gulf coast. A lead shortwave trough
now over northern Mexico will begin to affect the TX coast by this
evening, with its influence spreading east-northeastward across the
lower MS Valley by Saturday morning.
...TX coast this evening to the lower MS Valley overnight...
Convection on Thursday shunted the richer low-level moisture
southward into the northern Gulf, but low-level air mass recovery is
underway across the northwest Gulf coast. Today will be quiet in
terms of convective potential across the lower MS Valley. However,
the risk for severe thunderstorms will increase by this evening as
the lead midlevel trough from northern Mexico interacts with the
moisture/buoyancy gradient along the TX coast. The storm
environment will support supercells capable of producing large hail
and damaging winds as convection spreads east-northeastward toward
The more pronounced mass response to the midlevel trough will occur
tonight across the lower MS Valley, where strengthening low-level
flow/warm advection will contribute to multiple thunderstorm
clusters near and after midnight. Boundary layer dewpoints in the
mid-upper 60s will maintain surface-based buoyancy through the
overnight hours, while the increasing low-level shear will favor
supercells and some risk for tornadoes. Otherwise, steepening
midlevel lapse rates (emanating from northeast Mexico/south TX) will
promote large hail formation in the stronger/supercell storms, as
well as a risk for damaging winds.
...Southern CA coast this afternoon...
The latter system will overspread the central/southern CA coast
today, with focused ascent in the left-exit region of the mid-upper
jet. Steepening lapse rates and some increase in low-level moisture
with onshore flow later today will drive at least weak surface-based
buoyancy near the southern CA coast. Deep-layer vertical shear and
buoyancy will be sufficient for low-topped supercells and organized
line segments capable of producing isolated damaging gusts, and
perhaps a brief waterspout/tornado along the coast.
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