The Nation’s Weather

…Moderate to heavy rainfall and localized flash flooding continues into
this evening for interior New England…

…Showers and thunderstorms expected to reach the Desert Southwest Sunday
night and then the Four Corners Monday morning with a risk for flash
flooding…

…A round of rain expected for the northern Rockies/High Plains Sunday
night into Monday morning with gusty winds…

…Storm chances shift from the southern Plains Sunday to the
central/northern Plains Monday…

An anomalously deep low pressure system for late May continues to churn
northward through New England this afternoon (Saturday) accompanied by
widespread showers and thunderstorms. Plentiful moisture leading to
locally heavy downpours (rain rates of 1″/hr) and repeated rounds of
storms focused through portions of Vermont and New Hampshire may lead to
some scattered instances of flash flooding, with a Slight Risk of
Excessive Rainfall (level 2/4) in effect. Storms will lift northeastward
from central New England into Maine through this evening and should come
to an end for all locations by Sunday morning. Forecast high temperatures
Sunday more broadly across the Northeast and into the Mid-Atlantic, Lower
Great Lakes, and Ohio Valley will remain below average Sunday under an
associated upper-low and following a cold front passage, ranging from the
50s and 60s in the Interior Northeast and 60s and 70s elsewhere. Highs
will climb closer to average and be in the 70s for most by Monday as the
upper-low departs the region.

The upper-ridge bringing very hot, Summer-like and record heat to the West
Saturday will begin to shift eastward on Sunday, with well above average
temperatures into the 80s and 90s stretching from the Interior West into
the northern Plains. The heat will shift into the Upper Midwest on Monday
while an upper trough/accompanying surface cold front moving south through
the interior West brings much cooler temperatures to the northern
Rockies/High plains (highs in the 60s) and more seasonable temperatures
elsewhere in the Great Basin and along the West Coast (70s and 80s).
Showers and thunderstorms, along with some gusty winds, will accompany the
cold front passing through the northern Rockies/High Plains Sunday night
into Monday. Meanwhile, further south, moisture associated with the
remnants of Alvin will flow northward into the Southwest Sunday bringing
showers and thunderstorms capable of locally heavy rainfall. Some
scattered instances of flash flooding will be possible, especially across
southeastern Arizona where a Slight Risk of Excessive Rainfall is in
place. The storms will shift northward into the Four Corners region Monday
with moderate to locally heavy rainfall and additional isolated instances
of flash flooding possible. Below average highs are expected, with 80s to
low 90s in the Desert Southwest Sunday and 60s across the Four Corners
region by Monday.

An upper-level shortwave and accompanying surface cold front moving
southward over the central/southern Plains will trigger a round of storms
this evening. Some storms may be severe across portions of southern Kansas
and central Oklahoma, with a Slight Risk from the Storm Prediction Center
(level 2/5) for the threat of large hail and damaging winds. The front
will continue southward into central/eastern Texas Sunday, with another
Slight Risk of severe weather in effect for the threat of very large hail
and some damaging winds. Then, on Monday, anomalously high moisture will
return northward ahead of the approaching upper-trough/cold front passing
through the northern Rockies and into the central/northern Plains and
Upper Midwest. Thunderstorm development is expected to focus along the
cold front, with Slight Risks in effect for both severe weather and
Excessive Rainfall/flash flooding, generally from eastern South Dakota
southwest through central/western Nebraska and into southeastern
Wyoming/northeastern Colorado. Forecast highs across the central/southern
Plains and into the Mississippi Valley will be around to above average the
next couple of days, with 80s and 90s forecast.

Elsewhere, daily shower and thunderstorm chances continue for Florida. An
upper-level shortwave passing over the Southeast will lead to some
scattered storm chances Sunday. Forecast highs Sunday and Monday are
generally around average, with mostly 80s expected.

Putnam

Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php