Jun 1, 2018 2000 UTC Day 1 Convective Outlook
Updated: Fri Jun 1 19:50:14 UTC 2018 (20180601 2000Z Day 1 shapefile | 20180601 2000Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Public Severe Weather Outlook

The SPC is forecasting ...Severe thunderstorms expected over parts of the central Plains this afternoon and tonight....   Please read the latest public statement about this event.  View What is a Watch? clip.

Categorical Graphic
20180601 2000 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
MODERATE 14,635 264,013 Grand Island, NE...Columbus, NE...
ENHANCED 56,169 1,711,382 Omaha, NE...Lincoln, NE...Council Bluffs, IA...Bismarck, ND...Bellevue, NE...
SLIGHT 192,775 10,377,822 Atlanta, GA...Birmingham, AL...Columbus, GA...Sioux Falls, SD...Topeka, KS...
MARGINAL 235,074 17,510,970 Charlotte, NC...Kansas City, MO...Raleigh, NC...Greensboro, NC...Durham, NC...
Probabilistic Tornado Graphic
20180601 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
10 % 9,783 184,567 Bismarck, ND...Mandan, ND...
5 % 43,415 316,426 Grand Island, NE...Minot, ND...Hastings, NE...
2 % 59,843 1,669,082 Omaha, NE...Lincoln, NE...Council Bluffs, IA...Bellevue, NE...Kearney, NE...
Probabilistic Damaging Wind Graphic
20180601 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
SIG SEVERE 25,174 1,515,461 Omaha, NE...Lincoln, NE...Bellevue, NE...Grand Island, NE...Kearney, NE...
45 % 10,661 255,206 Grand Island, NE...Columbus, NE...
30 % 25,135 1,433,754 Omaha, NE...Lincoln, NE...Council Bluffs, IA...Bellevue, NE...Kearney, NE...
15 % 198,822 10,552,822 Atlanta, GA...Birmingham, AL...Columbus, GA...Sioux Falls, SD...Topeka, KS...
5 % 250,770 17,487,477 Charlotte, NC...Kansas City, MO...Raleigh, NC...Greensboro, NC...Durham, NC...
Probabilistic Large Hail Graphic
20180601 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
SIG SEVERE 69,236 552,806 Bismarck, ND...Grand Island, NE...Kearney, NE...Hastings, NE...Mandan, ND...
45 % 10,047 120,196 Grand Island, NE...
30 % 45,966 514,012 Bismarck, ND...Minot, ND...Kearney, NE...Norfolk, NE...Hastings, NE...
15 % 131,102 2,129,457 Omaha, NE...Lincoln, NE...Sioux City, IA...Council Bluffs, IA...Bellevue, NE...
5 % 249,344 25,380,743 Charlotte, NC...Kansas City, MO...Atlanta, GA...Raleigh, NC...Greensboro, NC...
   SPC AC 011950

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0250 PM CDT Fri Jun 01 2018

   Valid 012000Z - 021200Z

   ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS LATE THIS
   AFTERNOON AND EVENING ACROSS PARTS OF CENTRAL/EASTERN NEBRASKA...

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS
   SURROUNDING AREAS OF THE CENTRAL PLAINS...AND ACROSS PARTS OF THE
   WESTERN/CENTRAL NORTH DAKOTA...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE EASTERN GULF COAST STATES...

   ...SUMMARY...
   Large hail, damaging winds, and a few tornadoes are likely from the
   northern and central Plains into the middle Missouri Valley late
   this afternoon into tonight. Severe winds and some hail are also
   possible across parts of the Southeast.

   ...20Z Outlook Update...
   Adjustments to the 10 percent probability of thunder (categorical
   thunder) line and severe categorical and probabilistic lines (mainly
   across parts of the southern high Plains and Southeast) have been
   made.  This is mostly in at attempt to better account for current
   trends concerning destabilization and the influence of ongoing and
   prior convection.

   Areal coverage suggested in the vicinity of the dryline across the
   southern high Plains, near/beneath the center of prominent
   subtropical ridging, may still be a bit generous.  Aside from the
   higher terrain of southwest Texas, forcing to support convective
   development is generally weak/unclear, but convection allowing model
   output suggests the initiation of storms is at least possible.

   Primary severe weather potential will remain focused across parts of
   the northern and central Plains late this afternoon and evening,
   supported by large-scale forcing associated with the short wave
   trough now progressing across/east of the northern Rockies.  For
   more detailed information concerning ongoing or imminent severe
   weather potential across this and other areas, please refer to the
   latest SPC mesoscale discussions and watches.

   ..Kerr.. 06/01/2018

   .PREV DISCUSSION... /ISSUED 1145 AM CDT Fri Jun 01 2018/

   ...Northern/central Plains...
   Water vapor imagery late this morning features a notable late-spring
   shortwave trough spreading northeastward from the northern Rockies
   toward the northern High Plains, with appreciable height falls
   expected as far east as the middle Missouri Valley and Upper Midwest
   by tonight. A belt of strengthening (and backing) mid-level winds
   will precede this trough, while surface cyclogenesis occurs across
   the Dakotas today, and secondary cyclogenesis occurs across the
   central Plains tonight. 

   It appears that an initial increase in severe thunderstorms will
   occur relatively early this afternoon across northern Wyoming and
   southeast Montana with a few supercells capable of large hail.
   Another focus for potentially intense storm development will be in
   and around west-central/south-central North Dakota near a surface
   triple point. Persistent regenerative convection at midday poses
   some uncertainty, but abating cloud cover should allow for rapid
   destabilization by mid/late afternoon. Deep-layer/low-level shear
   will be more than adequate for supercells capable of large hail and
   a few tornadoes especially across west-central/south-central North
   Dakota where low-level SRH is likely to be maximized. 

   Farther south, additional at least isolated to widely scattered late
   afternoon/early evening development is expected southward across
   South Dakota and into central Nebraska initially in vicinity of a
   surface trough, with more extensive upscale-evolving development
   likely this evening as an upstream cold front overtakes the surface
   trough. A very unstable environment will exist along and
   south/southwest of a warm front, with deep-layer/low-level shear
   maximized near/just north of the warm front. Supercells capable of
   very large hail and some tornado risk can be expected initially,
   with the scenario likely to result in mature MCS development by late
   evening. Aided by a strengthening (50+ kt) low-level jet, an MCS is
   likely to spread southeastward with damaging wind potential across
   the Missouri Valley this evening and possibly into the overnight.

   ...Southeast States...
   Although the severe-weather potential may not be as widespread as
   previously thought, multiple outflow/differential-heating related
   boundaries will help focus an increase in coverage/intensity of
   thunderstorms this afternoon within a moist and increasingly
   unstable environment. Damaging winds will be the most common impact,
   although some hail is possible as well.

   ...Southern High Plains...
   Widely scattered thunderstorms are forecast to develop this
   afternoon near the dryline, from northwestern OK and the eastern TX
   Panhandle southwestward across the lower Caprock region to the lower
   Pecos River area around FST.  Isolated severe gusts and/or hail
   appear possible for a few hours before nocturnal cooling stabilizes
   the air mass in the evening and convective coverage/intensity
   accordingly declines.

   By mid-afternoon, intense insolation will contribute to surface
   temps above 100 F and very deep/well-mixed boundary layers -- even
   on the moist side of the dryline -- beneath midlevel lapse rates
   exceeding 8 deg C/km.  Even where moist-sector dew points mix down
   into the 50s F, heating and weak mass convergence readily should
   remove MLCINH and contribute to MLCAPE exceeding 2000 J/kg in much
   of the outlook corridor.  DCAPE of 1000-2000 J/kg should be common,
   supporting maintenance of hail and acceleration of downdrafts to
   surface.  Vertical shear is forecast to be modest by most measures
   under or near the upper ridge, as low-level flow is expected to
   weaken with southward extent, yielding small boundary-layer
   hodographs.  As such, the primary convective mode should be
   multicellular, though some supercell structures are possible over
   the Panhandle/western OK area where mid/upper winds and cloud-layer
   shear will be more favorable.

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