Jan 19, 2017 1730 UTC Day 2 Convective Outlook
Updated: Thu Jan 19 17:30:08 UTC 2017 (20170119 1730Z Day 2 shapefile | 20170119 1730Z Day 2 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170119 1730 UTC Day 2 Outlook Graphic
Day 2 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 57,244 5,296,792 New Orleans, LA...Baton Rouge, LA...Mobile, AL...Jackson, MS...Metairie, LA...
MARGINAL 52,648 14,729,806 San Diego, CA...Long Beach, CA...Santa Ana, CA...Anaheim, CA...Birmingham, AL...
Probabilistic Graphic
20170119 1730 UTC Day Probabilitic Graphic
Probability of severe weather within 25 miles of a point.
Hatched Area: 10% or greater probability of significant severe within 25 miles of a point.
Day 2 Prob. Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
15 % 57,254 5,260,942 New Orleans, LA...Baton Rouge, LA...Mobile, AL...Jackson, MS...Metairie, LA...
5 % 52,679 14,118,468 San Diego, CA...Long Beach, CA...Santa Ana, CA...Anaheim, CA...Birmingham, AL...
   SPC AC 191730

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1130 AM CST Thu Jan 19 2017

   Valid 201200Z - 211200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FRIDAY NIGHT
   ACROSS PARTS OF THE LOWER MISSISSIPPI VALLEY AND ADJACENT GULF
   COASTAL AREAS...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS
   SURROUNDING PORTIONS OF THE GULF COAST STATES...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS NEAR SOUTHERN
   CALIFORNIA COASTAL AREAS...

   ...SUMMARY...
   A few severe storms are possible Friday night into early Saturday
   across the lower Mississippi Valley and adjacent Gulf coastal areas.
   Strong thunderstorms with at least some severe weather potential are
   also possible near the southern California coast.

   ...Synopsis...
   Models continue to indicate that a seasonably strong mid/upper jet,
   with a number of embedded speed maxima, emanating from the
   mid-latitude Pacific will continue to develop inland across the
   southern tier of the U.S. during this period.  This appears likely
   to include a 110-130 kt 500 mb jet streak, which is generally
   forecast to dig southeastward near the southern California coast and
   contribute to the development of larger-scale mid/upper troughing
   inland of the Pacific Coast through the Mississippi Valley by 12Z
   Saturday.  Preceding this feature, an elongating closed low and
   associated upper troughing, now over the central and southern
   Plains, is expected to become increasingly deformed/sheared while
   pivoting north/east of the middle Mississippi/lower Ohio Valley
   Friday through Friday night.

   In lower levels, temperatures will continue to moderate across most
   areas east of the Rockies, with general deepening of low pressure
   across much of the Plains and Mississippi Valley into the lower Ohio
   Valley.  The primary frontal zone or zones may continue to develop
   well inland of the Gulf Coast region.  However, the leading edge of
   lower/mid tropospheric warming and drying in the wake of the lead
   upper impulse may reach north central Gulf coastal areas and the
   northwestern Gulf of Mexico by 12Z Friday, before stalling during
   the day Friday.  This may include a convectively generated or
   enhanced surface boundary which could advance offshore, before a
   significant southerly return flow of moisture develops across the
   northwestern Gulf Coast and lower Mississippi Valley Friday night.

   ...Northwestern/north central Gulf Coast and lower MS Valley...
   The exact position of the potential convective outflow boundary and
   leading edge of the lower/mid tropospheric subsidence and
   warming/drying remains a bit uncertain through much of the day
   Friday.  It is possible that it could stall close enough to coastal
   areas, from the upper Texas coast through the western Florida
   Panhandle, that widely scattered storms could initiate across those
   areas in response to daytime heating.

   More likely, primary convective development may occur in response to
   strengthening low-level warm advection on the leading edge of the
   deeper/more favorable low-level moisture return.  This is expected 
   across parts of the northwestern Gulf of Mexico/upper Texas and
   Louisiana coastal areas Friday evening, northeastward through
   portions of southern Louisiana and central Mississippi Friday night.
   In the presence of strengthening wind fields and vertical shear,
   including a southerly 850 mb jet to 40-50+ kt, destabilization is
   expected to become sufficient to support a risk for severe storms. 
   This may be mostly in the form of severe hail, with activity
   initially elevated above a residual stable near surface layer.

   By late Friday night, forcing for ascent may become strong enough,
   southward along the 850 mb jet axis toward southeast
   Louisiana/Mississippi/Alabama coastal areas, to overcome inhibition
   and support increasing convective development.  In the presence of
   increasingly boundary layer based instability, the risk for
   supercells with potential for tornadoes, in addition to large hail
   and damaging winds, may increase by or shortly after 12Z Saturday.

   ...Southern California coastal areas...
   Some uncertainty exists concerning the exact track of the intense
   mid/upper jet streak, and just how cold mid-level temperatures will
   be near the coast and coastal waters.  However, at least scattered
   convective development appears possible during the day Friday, in
   the presence of lower/mid tropospheric warm advection.  Including
   west southwesterly 850 mb flow on the order of 40+ kt, vertical
   shear in the convective layer may be sufficient for low topped
   supercells, with a risk for strong surface gusts and perhaps a
   tornado.

   ..Kerr.. 01/19/2017

   NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0700Z