Day 2

Categorical Day 1 Outlook

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.

Probability of one inch diameter hail or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of two inch diameter hail or larger within 25 miles of a point.

Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% or greater probability of wind gusts 65 knots or greater within 25 miles of a point.

000
ACUS01 KWNS 041957
SWODY1
SPC AC 041955

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0255 PM CDT Tue Aug 04 2020

Valid 042000Z - 051200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
INTO TONIGHT ACROSS MUCH OF NEW ENGLAND AND PARTS OF THE CENTRAL
GREAT PLAINS...

...SUMMARY...
A risk for tornadoes will continue in association with Isaias,
across southern New England by late this afternoon, and perhaps
through northern New England this evening.  Otherwise, scattered 
thunderstorms across parts of northern and central Great Plains may
pose a risk for severe hail and wind late this afternoon and
evening.

...Discussion...
The only notable change is to reduce hazard probabilities across
southern New England in association with the northward movement of
Isaias.

..Smith.. 08/04/2020

.PREV DISCUSSION... /ISSUED 1108 AM CDT Tue Aug 04 2020/

...Synopsis...
Large-scale mid-level troughing remains amplified across much of the
Mississippi Valley into the Appalachians, but as a significant
embedded short wave impulse pivots across and northeast of the Great
Lakes region, some loss in amplitude appears likely to commence
later today and tonight.  This perturbation is preceded by Isaias,
now accelerating north-northeastward across the northern Mid
Atlantic coast, and likely to gradually become absorbed within the
larger-scale cyclonic flow developing across the St. Lawrence Valley
by late tonight.

Upstream, some suppression of mid-level ridging appears probable
across the Great Plains, perhaps more notably across the northern
portions, than central and southern, associated with a more
substantive digging short wave impulse now near the international
border.  

Given the persistence of the eastern troughing, seasonably high
moisture content air is now largely confined to near and east of the
Atlantic Seaboard, with steep lower/mid tropospheric lapse rates
largely confined to the Intermountain West, Rockies and adjacent
portions of the Great Plains.

...Northeast...
Clockwise-curved low-level hodographs remain maximized near the core
of the strongest 850 mb flow curving to the east and north of
Isaias, along which there has been a persistent arcing band of
convection, with embedded low-level mesocyclones.  This band appears
likely to pivot north of Long Island through much of southern New
England by late afternoon, accompanied by a continuing risk of
tornadoes, as lower/mid 70s surface dew points advect ahead of it. 
Models suggest that this low-level moist inflow will eventually
become cut off, which may lead to decreasing potential for tornadic
development across northern New England this evening.

...Front Range into central Great Plains...
Although late afternoon mid-level height falls may be more subtle
than farther north, models suggest that mixed-layer CAPE will become
maximized on the order of 2000 J/kg, to the lee of the Front Range
by late this afternoon.  Aided by orographic forcing and perhaps
lift associated with a subtle mid-level impulse, thunderstorms are
expected to initiate off the Front Range, then advect off the higher
terrain within modest northwesterly mid-level flow.  Aided by strong
shear, isolated supercells and organizing storm clusters are
possible, which may pose a risk for severe hail and strong wind
gusts into this evening.

$$
        

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Day 4