…Multi-day flash flooding and severe weather threat across the Southern
Plains into the Lower Mississippi Valley Monday-Tuesday…
…Best chances for clear viewing of Monday’s total eclipse across the
path of totality expected in northern New England, clearer skies possible
but more uncertain from Arkansas northeast to Indiana…
…Lingering snow showers over the Northern High Plains will taper off
into Monday with scattered rain showers expected over the Upper Midwest…
…Critical Fire Weather Risk continues over portions of the Southern High
Plains Monday…
While tomorrow’s total eclipse will be occupying a lot of attention, areas
of active weather will also be present, including in the path of totality.
An upper-level low/accompanying surface frontal system over the central
U.S. Sunday evening will continue to progress eastward during the day on
Monday, bringing shower and thunderstorm chances to portions of the
Southern Plains and Lower Mississippi Valley, as well as some rain showers
to the Upper-Midwest and a wintry mix in the Northern Plains. To the
south, moist Gulf return flow over the Southern Plains/Lower Mississippi
Valley along and ahead of a lingering frontal boundary will lead to
increasing shower and thunderstorm chances through the day. The presence
of moderate to strong buoyancy and sufficient deep layer shear is expected
to lead to several more robust, severe thunderstorms, with an Enhanced
Risk of Severe Weather (level 3/5) from the Storm Prediction Center over
northwest Texas where the greatest potential for instances of large to
very large hail exists. A broader Slight Risk is in place across portions
over central and northern Texas/southern Oklahoma east into the ArkLaTex
where some large hail, damaging winds, and tornadoes can be expected.
Additionally, as thunderstorms begin to increase in coverage Monday
evening into Monday night across the ArkLaTex, heavy downpours are
expected to lead to locally heavy rainfall totals and a few instances of
flash flooding, with a Slight Risk of Excessive Rainfall (level 2/4) in
place. To the north, some light to moderate rain showers will continue in
the Upper Midwest in the vicinity of the surface cyclone and under the
influence of the upper-low. A transition into a wintry mix/snow showers to
the west will also continue over portions of the Northern High Plains
after a very windy and snowy Sunday. A few inches of additional snow will
be possible into Monday morning, before conditions improve into the day as
the system weakens. Some additional showers and storms will be possible
through early Monday arcing south from the Lower Great Lakes into the Ohio
Valley/Appalachians and then west into the Tennessee Valley, though these
should taper off into the day as well.
As far as eclipse viewing in the path of totality, sky cover forecasts
continue to show that the most likely locations to see clearer skies are
in northern New England. Clearer skies may also be possible from Arkansas
northeast through central Indiana, however there is more uncertainty due
to the potential for some higher clouds. Unfortunately, conditions look
cloudier over Texas and from Ohio northeast through northwest Pennsylvania
and New York. However, the timing, location, and height of potential cloud
cover during the eclipse even in these areas may change or could work
favorably and not impede viewing as much as expected.
Heading into Tuesday, additional shortwave energy wrapping around the
upper-low as well as a second upper-level system approaching the Southern
Plains from the west will help to reinvigorate the surface frontal system,
reinforcing a frontal boundary from the Upper Great Lakes southwestward
through the Middle Mississippi Valley and into the Southern Plains.
Another day of enhancing southerly moist Gulf flow will help to continue
shower and thunderstorm chances along and ahead of the quasi-stationary
boundary. The combination of additional moisture as well as better
upper-level support with the approaching system from the west will lead to
areas of potentially significant heavy rainfall. Forecast areal average
rainfall is over 3 inches from northeastern Texas into northern Louisiana,
southern Arkansas, and northwestern Mississippi late Monday into the day
Tuesday, with locally heavier totals of 4-6 inches possible. This rainfall
on top of increasingly wet antecedent conditions has prompted a Moderate
Risk of Excessive Rainfall (level 3/4) for the threat of scattered to
numerous instances of flash flooding. A broader slight risk exists from
north Texas east into the Lower Mississippi Valley where additional
locally heavy rainfall and scattered flash flooding will also be possible.
Unfortunately, the threat for heavy rainfall and flash flooding will
likely continue into the day Wednesday eastward into the Southeastern
U.S., just beyond the current forecast period. Another round of severe
thunderstorms is also expected in the region, with a Slight Risk of
severe weather stretching from the Lower Mississippi Valley further
westward into northwest and central Texas. Both individual and clusters of
more vigorous thunderstorms may lead to more instances of large hail and
damaging winds, with some tornado potential most likely from southeast
Texas into western Louisiana.
Elsewhere, dry, windy conditions are expected to continue west of the
storms across the Southern High Plains, prompting another Critical Risk of
Fire Weather (level 2/3) from the Storm Prediction center, with conditions
expected to gradually improve Tuesday. Showers and thunderstorms will
begin to spread further to the northeast ahead of the cold front into the
Ohio Valley/Lower Great Lakes, Appalachians, and Mid-Atlantic during the
day Tuesday. A frontal system moving into the Pacific Northwest will bring
increasing lower elevation/coastal rain and higher elevation mountain snow
to the Cascades by Monday evening, with snow chances spreading into
portions of the northern Rockies Tuesday. Forecast high temperatures will
tend to be at or above average and mild to warm over much of the
central/eastern U.S. Monday ahead of the system over the Midwest/Plains.
The greatest anomalies will be in the Lower Great Lakes vicinity, where
temperatures into the 60s and 70s are upwards of 15-20 degrees above
normal. The frontal boundary sagging southward and increasing coverage of
precipitation chances will bring cooler temperatures from the Tennessee
Valley west through the ArkLaTex and into portions of the Southern
Plains/Rockies Tuesday. Temperatures are forecast to warm up by 10-15
degrees over the Northern Plains Tuesday following one more chilly day on
Monday. An expanding area of warm, above average temperatures will spread
inland from California into the Great Basin Tuesday as an upper-level
ridge builds in.
Putnam
Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php