Valid 101200Z – 111200Z
…THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EASTERN
OREGON INTO WESTERN MONTANA…FROM SOUTHERN MONTANA INTO FAR
NORTHERN WYOMING…AND OVER A SMALL PART OF EASTERN NORTH
CAROLINA…
…SUMMARY…
Severe storms producing large hail and locally damaging wind gusts
are expected from eastern Oregon into western and southern Montana
during the afternoon and evening. A cluster of storms, some severe,
is also expected over eastern North Carolina during the afternoon.
Other isolated activity is likely from the Black Hills into the
central High Plains with marginal hail and wind.
…Synopsis…
An upper low will move northeastward across OR, with cooling aloft
spreading over ID and western MT. At the surface, low pressure will
exist over northern NV into southern ID, with a cold front from
northwest NV into eastern OR late in the day. Increasing southerly
winds along with heating will result in scattered storms, some with
large hail and locally damaging winds, mainly from eastern OR into
western MT.
To the east, an upper ridge will exist over the High Plains, with
weak lee troughing and backed surface winds aiding westward moisture
transport and destabilization. Scattered daytime storms are again
likely from southern MT into eastern CO, and isolated severe storms
cannot be ruled out from afternoon through early evening.
Meanwhile, an upper trough will lift across the Northeast, with
moderate northwest flow across the Mid Atlantic. A surface trough
will develop over the Carolinas, with a stalled front over NC
providing a focus for clusters of strong to severe storms.
…OR into southwest MT…
The overall setup for severe storms appears more robust than on the
previous day, with lift over a large area and impressive lapse rate
profiles and deep-layer shear. Scattered storm coverage is likely by
mid afternoon as capping will be removed by 18Z, with storms
becoming numerous over central ID and into western MT by late
afternoon. Hail will strongly be favored with long hodographs, and a
few damaging wind gusts will be possible. Other isolated cells are
expected to form over eastern OR, and over Owyhee county ID which
will then move across the valley with a threat of hail in excess of
1.00″ (with isolated reports to ping-pong or golf ball size). A few
storms may affect extreme eastern WA as well. The threat of hail may
persist into the evening as the upper trough continues across the
region providing lift.
…Eastern North Carolina…
The combination of a stalled front, a sea breeze, and strong inland
heating of a very moist air mass will lead to MLCAPE in excess of
2000 J/kg, beneath west/northwest winds aloft which will lengthen
hodographs. A cluster of strong to severe storms is expected to form
around 18-19Z, with splitting cells possible. Hail will be possible
despite warm midlevel temperatures, along with a few damaging wind
gusts.
…Southeast MT into northern WY…
East to northeast surface winds will maintain a band of upper 40s to
lower 50s F dewpoints over southern MT and northern WY, with storms
expected to form over the higher terrain by 21Z. Southwesterly mid
to upper-level winds will result in long hodographs favoring cells
capable of hail, and perhaps a few severe wind gusts with any small
bows.
…Eastern CO into western KS and southern NE…
Strong instability will develop with heating beneath the upper ridge
from eastern CO into western KS/NE, with easterly surface winds
counteracting mixing of dewpoints. Storms will form over the Front
Range by around 21Z, and may produce a few damaging wind gusts as
they travel across CO and into western KS. Other storms are possible
along a modifying outflow boundary, possibly near I-80, with
localized severe wind or hail late in the day.
..Jewell/Cook.. 08/10/2019
$$