…A coastal low brings a threat of flash flooding to the Mid-Atlantic
today with precipiation chances lingering through Wednesday…
…A strong low pressure system will bring unsettled weather to the
northern/central Rockies and Plains with severe thunderstorms expected
this evening in the northern/central High Plains…
…Very heavy rainfall expected in Montana on Wednesday with some flash
flooding possible…
An area of low pressure, previously labeled as Potential Tropical Cyclone
Eight, will continue to slowly move north across the Carolinas towards the
Mid-Atlantic over the next day or so. Moist, onshore flow will support
persistent showers and thunderstorms across portions of North Carolina and
the southern Mid-Atlantic through early Wednesday, and locally heavy
rainfall could result in isolated to scattered instances of flash
flooding. Flood Watches are in effect for portions of southeastern
Virginia and North Carolina. Precipitation chances will expand
northeastward into southern New England through the day Wednesday, though
intensity should begin to decrease overall, resulting in a lower threat
for flash flooding. Coastal flooding will also be a concern with a
prolonged period of onshore winds along the Mid-Atlantic coast. By
Thursday, this system will begin to shift offshore into the Atlantic and
high pressure will build behind it.
Meanwhile, a strong low pressure system moving across the Intermountain
West this afternoon will begin to emerge into the northern/central Plains
this evening, strengthening in the lee of the Rockies. Widespread showers
and thunderstorms are forecast with this system in the vicinity of the low
pressure center and along and ahead of the trailing cold front. Some
thunderstorms may become severe this evening in the northern and central
High Plains, and the Storm Prediction Center has highlighted this area
with a Slight Risk of severe thunderstorms (level 2/5) with an embedded
Enhanced Risk (level 3/5) over the central High Plains. Severe storm
hazards include significant damaging winds and isolated large hail.
Further north, anomalously moist, strong easterly upslope flow along the
northern Rockies will lead to thunderstorms and very heavy rainfall
tonight and especially on Wednesday. A Slight Risk of Excessive Rainfall
(level 2/4) covers portions of north-central Montana where several inches
of rain (2-4″+) are possible, leading to a heightened risk of flooding.
Winds are also expected to be rather gusty as the low strengthens,
prompting some high wind-related warnings and advisories for portions of
the northern High Plains. Gusts as high as 60 mph will be possible,
particularly along the Front Range of the Rockies. Additional isolated
thunderstorms are expected ahead of the eastward moving cold front through
the Plains on Wednesday and into the Upper Midwest by late Wednesday and
into Thursday. More favorable overlap of strong upper-level winds with an
accompanying trough and increased moisture/instability will lead to the
threat of some additional severe weather Thursday. There is a Slight Risk
over portions of eastern Minnesota, northwestern Wisconsin, and northern
Iowa for isolated large hail and damaging winds.
Another system approaching the Pacific Coast will bring some scattered
showers and storms to the coastal Pacific Northwest this evening,
spreading southward into northern California and the central Great Basin
on Wednesday. The rain will be relatively modest for most areas, with the
highest expected in the Sierras, where a bit of snow may mix in at the
higher elevations. Temperature-wise, much of the northern-tier of the
central/eastern U.S. as well as the Plains will remain much above average
Wednesday and Thursday. Highs will be into the mid- to upper 80s for
portions of northern New England and the Upper Midwest Wednesday, and a
handful of near record-tying/breaking highs approaching 100 will be
possible for portions of the southern Plains on Thursday. Meanwhile,
temperatures will be well below average across the West behind the strong
Plains system, with many highs in the 60s across the Great Basin and only
in the 80s for portions of the Desert Southwest. Highs will generally be
near average in the Southeast (80s-90s) and Mid-Atlantic (70s-80s) the
next couple of days.
Putnam/Dolan
Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php
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