SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1219 PM CDT Mon Aug 08 2022
Valid 091200Z - 101200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TUESDAY
AFTERNOON ACROSS PARTS OF CENTRAL OREGON AND PARTS OF THE NORTHERN
MID ATLANTIC INTO SOUTHERN NEW ENGLAND...
...SUMMARY...
Isolated to widely scattered strong thunderstorms may impact parts
of central Oregon, as well as portions of the Mid Atlantic and
southern New England, Tuesday afternoon, and pose at least some risk
for severe weather.
...Synopsis...
In the southern mid- and subtropical latitudes, models indicate that
weak lower/mid tropospheric ridging will prevail across the western
Atlantic into much of the Southeast through this period. At the
same time, to the west, a mid-level high is forecast to become
increasingly prominent near/east of the Rockies into much of the
Great Plains, downstream of amplified mid-level troughing
near/offshore of the U.S. Pacific coast. While there will likely be
little, if any, eastward progression of this larger-scale troughing,
a fairly deep embedded mid-level low may migrate slowly
north-northeastward offshore of the northern California/southern
Oregon coast.
Flow in the higher latitudes likely will remain more zonal and
progressive. This is forecast to include one significant mid-level
trough, with a couple of vigorous embedded smaller-scale
perturbations, shifting east of the Canadian Prairies through the
northern Ontario/Hudson Bay/western Quebec vicinity by 12Z
Wednesday. A much more modest preceding perturbation is forecast to
accelerate across and east of the Canadian Maritimes and New England
into the northern Atlantic. This will be accompanied by the
southward advancement of one surface cold front across the St.
Lawrence Valley, and to the lee of the lower Great Lakes, offshore
of New England into northern Mid Atlantic coast by late Tuesday
night. The western flank of this front likely will stall across the
lower Ohio into middle Mississippi Valleys, while a reinforcing
front advances into the Upper Midwest and northern Great Plains.
Moisture content will remain seasonably high along and to the south
of the lead front, to the east of the Rockies, while monsoonal
moisture will gradually advect around the southwestern periphery of
the strengthening high, from the Southwest into the northern
intermountain region, to the east of the developing low offshore of
the Pacific coast.
...Northeast...
Large-scale forcing for ascent along and ahead of the southward
advancing front appears likely to remain generally modest to weak.
However, strong heating of a moist boundary layer (temps rising into
the 90s with surface dew points in the mid 60s to around 70F) may
contribute to moderate CAPE (on the order of 1000-2000 J/kg) along
the front and pre-frontal surface trough, inland of the northern Mid
Atlantic into southern New England coast by Tuesday afternoon. It
appears that this will be sufficient to support widely scattered to
scattered thunderstorms. Although deep-layer shear will be weak,
model forecast soundings indicate southwesterly to westerly flow
around 20 kt in the 850-700 mb layer. This may be enough, coupled
with the fairly steep low-level lapse rates and potential heavy
precipitation loading, to support the risk for a few potentially
damaging wind gusts before storms weaken by Tuesday evening.
...Central Oregon (near/east of the Cascades)...
Downstream (to the northeast of the approaching mid-level low),
forcing for ascent is generally forecast to contribute to
considerable thunderstorm development Tuesday afternoon into Tuesday
evening. Forecast soundings indicate that CAPE may remain limited
to 500-1000 J/kg or less, but beneath 30-70 kt southerly flow in the
500-300 mb layer, strong deep-layer shear will be at least
conditionally supportive of isolated supercells posing a risk to
produce severe hail and locally strong surface gusts.
..Kerr.. 08/08/2022
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