Severe Storm Outlook Narrative (AC)
Issued by NWS

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
ACUS11 KWNS 211838
SWOMCD
SPC MCD 211838
CTZ000-NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-DCZ000-VAZ000-WVZ000-212115-

Mesoscale Discussion 1108
NWS Storm Prediction Center Norman OK
0138 PM CDT Wed Jun 21 2017

Areas affected...Portions of central/southern PA...MD...far eastern
WV...DC...far northern VA...DE...NJ...southern NY...and CT

Concerning...Severe potential...Watch unlikely

Valid 211838Z - 212115Z

Probability of Watch Issuance...5 percent

SUMMARY...Strong/gusty winds associated with isolated thunderstorms
this afternoon may produce sporadic tree damage. A watch is not
anticipated for this marginal severe threat.

DISCUSSION...Isolated thunderstorms have developed over the past
hour or so along a remnant front across central PA. Visible
satellite imagery shows partly to mostly sunny conditions to the
east of this isolated convection (across eastern PA/northern NJ into
southern NY/CT), and surface temperatures have generally warmed into
the 80s away from the coast. Although the low-level airmass is not
overly moist along/south of the remnant front per area 18Z surface
observations and 12Z soundings, it is sufficient to support weak
instability of generally 250-750 J/kg (MLCAPE). Some additional
diurnal heating through late afternoon may locally boost MLCAPE to
around 1000 J/kg.

Recent VWPs from KCCX depict nearly unidirectional westerly flow
strengthening quickly to around 45-50 kt at 5 km, and the
mid/upper-level flow likely increases further through the remainder
of the troposphere given the presence of a belt of enhanced flow
over this region per latest short-term guidance and water vapor
satellite imagery. Related effective bulk shear of 40-50 kt should
support some convective organization even with instability expected
to remain modest owing mainly to poor mid-level lapse rates.
Steepening low-level lapse rates owing to continued diurnal heating
combined with the strong shear may result in an isolated
strong/gusty convective downdraft wind risk. However, nebulous
large-scale forcing for ascent, weak instability, and generally
isolated thunderstorm coverage will likely keep the overall severe
threat marginal. Therefore, watch issuance is not expected at this
time.

..Gleason/Weiss.. 06/21/2017

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...BOX...OKX...ALY...PHI...BGM...CTP...LWX...PBZ...

LAT...LON   40657944 40847805 40997660 41117494 41957371 41977287
            41817218 41477196 40897223 40627291 40437381 39867399
            39637409 38927477 38787498 38677632 39077820 39417951
            40367985 40657944



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.