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Day 1 Outlook Convective Tornado
Hail Wind
Categorical Day1 1200Z Outlook
  
Images courtesy of the NWS Storm Prediction Center
 Forecast Discussion


000
ACUS01 KWNS 240553
SWODY1
SPC AC 240552

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1252 AM CDT Mon Jul 24 2017

Valid 241200Z - 251200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER A PORTION
OF THE NORTHERN PLAINS AND UPPER MISSISSIPPI VALLEY...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER A PORTION
OF THE NORTHEAST STATES AND MID ATLANTIC AREA...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER A PORTION
OF THE SOUTHEAST STATES...

...SUMMARY...
Isolated strong/severe storms may occur over portions of the
northern Plains vicinity, as well as across parts of the Northeast
States, Mid-Atlantic, and Mid-South.

...Synopsis...

Synoptic upper trough will continue through the Northeast U.S.
today, while an upstream trough advances through the Canadian
Prairies. A low-amplitude impulse now moving along the WY/MT border
will continue through the Dakotas and weaken. Cutoff upper low
should remain over northern CA. 

At the surface a quasi-stationary front will persist from NY to
southern New England. A cold front will move into the Middle
Atlantic area with trailing portion likely to stall over the TN
Valley.  Farther west a cold front will move through the northern
Plains in association with the Canadian shortwave trough. Warm front
will lift slowly north through the northern Plains and upper
Mississippi Valley.

...Northern Plains and Upper Mississippi Valley area...

Modified continental-polar air with dewpoints generally in the 50s
to near 60F will advect into the northern Plains beneath steep
mid-level lapse rates associated with a warm elevated-mixed layer,
contributing to destabilization. The atmosphere in this region
should become moderately unstable, but strong convective inhibition
may limit surface-based thunderstorm initiation until later this
afternoon when a few storms could form over central SD in
association with the weakening shortwave trough. Other storms might
also develop farther west within the more deeply mixed regime across
the western Dakotas and along the southeast-advancing cold front.
Given generally weak forcing aloft and moderate to strong convective
inhibition, storm coverage will probably remain isolated, but the
thermodynamic environment would support a conditional risk for
downburst winds and hail. Any storms that form during the day will
likely diminish with loss of heating. However, additional storms may
occur overnight across MN within zone of isentropic ascent north of
the warm front. Some of this activity could pose a risk for
marginally severe hail.  

...Northeast States and Mid Atlantic...

In wake of early morning convection associated with lead shortwave
trough, storms will once again develop along and ahead of the cold
front in the moist, weakly capped warm sector. Pockets of diabatic
warming will promote destabilization of the boundary layer, but the
thermodynamic environment will remain weak in most areas due in part
to poor mid-level lapse rates. Westerly unidirectional winds aloft
will reside across this region supporting 35-45 kt effective bulk
shear. A few storms might develop some mid-level updraft rotation
and evolve into bowing structures with a threat for a few locally
strong to damaging wind gusts. However, expected weak thermodynamic
environment should remain a limiting factor for a robust severe
risk. 

...Tennessee Valley area and Southeast States...

The atmosphere in this region will become moderately unstable, and
storms will likely redevelop along and south of the cold front. Weak
vertical shear will promote multicell and pulse storms. A few of the
stronger storms might produce locally strong to marginally severe
wind gusts from mid afternoon to early evening.

..Dial/Dean.. 07/24/2017

$$