Jul 4, 2020 2000 UTC Day 1 Convective Outlook

Categorical Graphic 20200704 2000 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 218,346 1,493,824 Amarillo, TX…Billings, MT…Fargo, ND…Bismarck, ND…Grand Forks, ND…
MARGINAL 227,616 3,205,211 Shreveport, LA…Pueblo, CO…Tyler, TX…Longview, TX…Missoula, MT…
Probabilistic Tornado Graphic 20200704 2000 UTC Day 1 Tornado Probabilities 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.) Area Pop. Some Larger Population Centers in Risk Area
5 % 10,009 46,527 Jamestown, ND…Valley City, ND…
2 % 188,056 1,453,014 Billings, MT…Fargo, ND…Rapid City, SD…Bismarck, ND…Grand Forks, ND…
Probabilistic Damaging Wind Graphic 20200704 2000 UTC Day 1 Damaging Wind Probabilities 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.
Day 1 Wind Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
15 % 218,086 1,528,995 Amarillo, TX…Billings, MT…Fargo, ND…Bismarck, ND…Grand Forks, ND…
5 % 227,046 3,168,407 Shreveport, LA…Pueblo, CO…Tyler, TX…Longview, TX…Missoula, MT…
Probabilistic Large Hail Graphic 20200704 2000 UTC Day 1 Large Hail Probabilities Graphic Probability of hail 1″ or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2″ or larger within 25 miles of a point.
Day 1 Hail Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
15 % 209,338 1,154,488 Billings, MT…Bismarck, ND…Grand Forks, ND…Minot, ND…Bozeman, MT…
5 % 206,382 2,163,231 Amarillo, TX…Pueblo, CO…Fargo, ND…Missoula, MT…Rapid City, SD…
   SPC AC 041943

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0243 PM CDT Sat Jul 04 2020

   Valid 042000Z - 051200Z


   Severe thunderstorms are expected this afternoon and tonight from
   southwest/central Montana to the Dakotas and northwest Minnesota, as
   well as parts of the south-central High Plains.

   No changes have been made to the ongoing forecast.  Thunderstorms
   are just beginning to develop over the mountains of southwest
   MT/northwest WY.  These storms will overspread much of the SLGT risk
   area this afternoon and evening, posing a risk of large hail and
   damaging winds.  Other storms are expected to form over eastern ND
   in a few hours, with an associated risk of hail and wind as well.

   ..Hart.. 07/04/2020

   .PREV DISCUSSION... /ISSUED 1142 AM CDT Sat Jul 04 2020/

   ...Northern Plains from Montana to Dakotas/northern Minnesota...
   Multiple episodes or clusters of strong/severe thunderstorms are
   expected to affect the region later this afternoon into tonight,
   with large hail and severe wind gusts as the primary hazard. Aided
   by an eastward-shifting upper trough over the Canadian Rockies,
   storms are expected to develop this afternoon initially over the
   mountains/higher terrain of southwest/south-central Montana as well
   as northern/eastern Wyoming. These storms will encounter an
   increasing moist/unstable environment as they spread
   east-northeastward, with 40+ kt effective shear contributing to
   organized storm modes including some supercells. Multiple
   east-northeastward moving bands/MCSs may materialize across eastern
   Montana/western North Dakota this evening into the overnight, with
   severe wind/hail potential continuing. 

   In the wake of the early day MCV, another focus for severe
   thunderstorm development may occur across southeast North Dakota in
   association with near a decaying/northward shifting outflow boundary
   and differential-heating zone. While deep-layer winds will not be as
   strong as across Montana (or northern North Dakota), low-level
   shear/vorticity may be maximized near the boundary. Along with steep
   lapse rates and 2500-3500 J/kg MLCAPE, this could support some
   initial supercells capable of large hail and possibly some tornado
   risk. These storms could grow upscale into a southeastward-moving
   MCS this evening.

   ...Central/southern High Plains...
   Isolated to scattered thunderstorms are expected to develop this
   afternoon over the eastern ranges and foothills of the Rockies, from
   the Laramie Mountains southward into the Sangre de Cristos,
   including the Raton Mesa and Palmer Divide. Some of this activity
   should persist eastward across the adjoining High Plains with a
   threat for severe wind gusts and large hail. The greatest
   concentration of convection and associated severe potential may
   occur for a few hours late this afternoon into early evening ahead
   of the shortwave trough and associated vorticity maxima, over
   portions of southeastern Colorado/northeast New Mexico, shifting
   into parts of the Texas Panhandle. Forecast soundings suggest steep
   low-level lapse rates, well-mixed subcloud layers, and sufficient
   moisture to support 1000-1500 J/kg MLCAPE, with large DCAPE. After
   an initial hail/wind blend of threats, some of this activity may
   aggregate outflows to produce a cold pool that would
   forward-propagate eastward for a few hours before weakening.

   ...Southeast Oklahoma/ArkLaTex vicinity...
   An MCV will continue to slowly drift southeastward today across the
   region. Ongoing convection may weaken/somewhat disperse today, but
   redevelopment of deeper convection is possible late this afternoon
   and more so this evening, primarily on the immediate southern fringe
   of the MCV and near persistent or decayed outflow. A cluster of
   storms could ultimately evolve, with the potential for some stronger
   thunderstorm wind gusts as storms progress southeastward within a
   moderately unstable environment.