…A convoluted pattern with embedded slow-moving systems is expected
across the Lower 48, leading to prolonged periods of unsettled weather
into early next week…
…Heavy precipitation is expected across the Northern Mid-Atlantic States
and from the Southern Rockies into the Great Basin…
Deep layer lows develop over the Ohio Valley and West Coast which will be
slow to move over the next few days. In the East, the first of the systems
is developing over the Ohio Valley. Its cold front makes slow progress
through the Central Gulf Coast and Southeast before stalling on Monday.
Showers and thunderstorms with heavy rainfall, with a few thunderstorms
being severe, are expected over portions of the Southeast and Mid-Atlantic
States with this system from Saturday evening through Monday. Rainfall
totals of 2 to 4 inches in and near portions of southeast New York of
Pennsylvania will foster a Marginal Risk of excessive rainfall/flash
flooding Saturday evening through Monday. Because of the persistent
humidity, record warm low temperatures are anticipated for portions of the
Mid-Atlantic States on Sunday.
A separate deep layer cyclone moves through the Southwest, bringing
showers and thunderstorms Saturday evening into Monday and higher
elevation snows in the Rockies/Intermountain West. A moist, upslope flow
along the southern Rockies should persist as a frontal boundary lingers
south of the region while unstable showers and thunderstorms form closer
to the cyclone during daytime heating. Isolated to scattered instances of
flash flooding will be possible across portions of eastern New Mexico,
particularly for terrain sensitive regions and area burn scars from
Saturday evening through Sunday. On Monday as the system moves towards
the Southern Plains, a scattered instances of flash flooding are expected
across portions of northwestern Texas. Accumulating snow is expected for
some of the higher elevations of regional mountain ranges, most notably
the Sierra Nevada Saturday evening and then portions of the northern
Rockies in Montana and the San Juans in Colorado on Sunday and Monday. Dry
antecedent conditions, gusty winds, and comparatively low relative
humidity over southwestern New Mexico, south of the unsettled weather
covering most of the West, has prompted a Critical Risk of fire weather
conditions from the Storm Prediction Center for Sunday.
Forecast highs under the eastern deep layer cyclone will be well below
average, particularly across portions of the Midwest/Ohio Valley, as
temperatures only reach into the 50s and 60s. Forecast highs under the
western deep layer cyclone will also be well below average,across the
Great Basin Sunday, with highs in the 50s and 60s, and into the Southwest,
with highs only into the 70s. In contrast, temperatures under a building
upper-level ridge between the lows will be well above average as highs
soar into the 70s and 80s across much of the northern/central Rockies and
into the northern Plains/Upper Great Lakes. Some locations along the
northern High Plains may reach the upper 80s on Sunday, upwards of 25-30
degrees above average.
Roth
Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php
