Jul 17, 2018 0600 UTC Day 1 Convective Outlook
Updated: Tue Jul 17 04:54:11 UTC 2018 (20180717 1200Z Day 1 shapefile | 20180717 1200Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20180717 1200 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 46,296 31,868,581 New York, NY...Boston, MA...Newark, NJ...Jersey City, NJ...Yonkers, NY...
MARGINAL 313,435 31,497,568 Philadelphia, PA...Baltimore, MD...Denver, CO...Washington, DC...Wichita, KS...
Probabilistic Tornado Graphic
20180717 1200 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
2 % 17,231 2,920,683 Manchester, NH...Lowell, MA...Nashua, NH...Lawrence, MA...Portland, ME...
Probabilistic Damaging Wind Graphic
20180717 1200 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 % 45,815 31,662,325 New York, NY...Boston, MA...Newark, NJ...Jersey City, NJ...Yonkers, NY...
5 % 318,466 32,341,777 Philadelphia, PA...Baltimore, MD...Denver, CO...Washington, DC...Tulsa, OK...
Probabilistic Large Hail Graphic
20180717 1200 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
5 % 362,597 63,358,878 New York, NY...Philadelphia, PA...Baltimore, MD...Boston, MA...Denver, CO...
   SPC AC 170454

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1154 PM CDT Mon Jul 16 2018

   Valid 171200Z - 181200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE NORTHEAST...

   ...SUMMARY...
   Strong to severe storms capable of primarily damaging wind will be
   possible across portions of the Northeast today.  Widely-scattered
   severe storms capable of hail and wind are also possible from
   eastern Wyoming and Colorado across Kansas and northern Oklahoma.

   ...Synopsis...
   An upper trough with a belt of 40 kt midlevel flow will spread
   eastward across Quebec and the northeastern states during the day
   with a cold front extending southwest into the Mid Atlantic. A moist
   and unstable air mass will exist ahead of this front with widespread
   upper 60s F to dewpoints resulting in sufficient instability for
   strong daytime storms. Lift associated with the upper trough will
   result in widespread rain and storms from midday through afternoon
   from the Mid Atlantic into New England, and a few storms may produce
   severe wind gusts.

   To the west, and upper high will remain centered across CA and NV,
   with a ridge axis extending eastward into the southern High Plains.
   West/northwesterly flow atop this ridge will extend from the
   northern Rockies into the central Plains, with a surface high over
   the upper MIdwest. A large area of warm and unstable air will remain
   over the central Plains, with sporadic severe storms possible during
   the day from eastern WY and CO into KS and northern OK.

   ...Northeast...
   Areas of rain and storms are forecast to be ongoing ahead of a cold
   front and in association with low-level warm advection out of the
   southwest from PA across NY and into New England. This lends some
   uncertainty to how unstable the area will become during the day.
   However, areas from central and southern New England toward the Mid
   Atlantic should remain free of storms through 18Z with the potential
   for more destabilization. The gradual increase in mean wind speeds
   through a deep layer along with overall linear forcing mechanism
   suggest locally strong to severe wind gusts may occur along with
   heavy rain. Some low-level turning of the winds with height may also
   favor an isolated supercell or two mainly across New England where
   winds will be strongest.

   ...Central Plains...
   Outflow from a storm complex ongoing across Nebraska early Tuesday
   will likely provide some focus for new development later today.
   Widespread warmth and instability will redevelop over the entire
   region, with southeasterly surface winds helping to shunt moisture
   northwestward into CO and WY. Weakly veering winds with height look
   to support southeastward-moving clusters of storms developing along
   the Front Range late in the day, and across KS near aforementioned
   outflows. Both hail and wind will be possible, and may extend into
   northern OK. A small Slight Risk cannot be ruled out in later
   outlooks once predictability with the ongoing activity increases.

   ..Jewell.. 07/17/2018

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z