...Hurricane Arthur will spread torrential rains, strong winds, and
dangerous surf from North Carolina northward along the coast...
...Additional heavy rainfall is possible across interior New England...
...Active monsoonal convection likely across the Southwestern U.S...
Hurricane Arthur, the first hurricane across the Atlantic basin, made
landfall earlier in the night across North Carolina as a category 2 storm. The National Hurricane Center expects Arthur to continue to accelerate north and east while generally maintaining its intensity during the next 12 to 24 hours. Eventually the system will become more extratropical in nature by Saturday morning while offshore of upper New England.
The usual impacts with a tropical cyclone will be in play here with torrential downpours and accompanied flooding, strong winds, along with high surf. Much of the heavy rainfall and high winds will focus along the immediate coastline which will be in closest proximity to the eye wall.
Further inland, tropical moisture surging in advance of Arthur is forecast to interact with a slow-moving cold front over the interior Northeastern U.S. This combination of lift along the boundary and anomalous moisture content may lead to periods of very heavy rainfall and associated flash flooding. By late Saturday, the center of the system will have pushed into Nova Scotia which will allow high pressure to build in the wake across the East Coast.
Although it will be a bumpy start to the Fourth of July holiday weekend, conditions should quickly improve for the latter half of the weekend.
A large mid-level anticyclone positioned over the Four Corners region will allow vast monsoonal moisture to surge northward into the Southwestern U.S. It should be an active next couple of days with the moisture content well above normal for early July. The convection will develop once diurnal heating commences with the individual thunderstorm complexes moving relatively slowly underneath the weak steering flow of ridge aloft. This may enhance the threat for localized flooding concerns, particularly in areas of steeper terrain. Much of the activity should wind down during the overnight hours given the loss of solar insolation.
Elsewhere, periods of showers and thunderstorms will be possible across the Northern Plains and into the Middle/Upper Mississippi Valleys during the next couple of days. Multiple weak impulses streaming eastward through the region should provide an impetus for convection.
The better coverage of precipitation is expected to be north of the international border with Canada. This marks where the mid/upper jet stream winds will be much stronger thus favoring more organized storms.