Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
411 PM EDT Tue Jul 26 2022

Valid 00Z Wed Jul 27 2022 - 00Z Fri Jul 29 2022

...Moderate Risks of flash flooding are in place with numerous flash
floods likely across the Ohio Valley/Central Appalachians over the next
few days...

...Monsoonal moisture to cause daily rounds of excessive rainfall and
flash flooding across portions of the Southwest and southern/central
Rockies and High Plains with Slight to Moderate Risks of excessive
rainfall...

...Dangerous heat to bake the Pacific Northwest and portions of the
south-central U.S. through midweek...

An upper-level low is forecast to spin across south-central Canada with
troughing extending into the north-central and northeastern U.S. over the
next few days. This trough/jet stream will be active with shortwave
energy, while at the surface a generally west to east oriented
quasi-stationary front will extend across central parts of the Plains and
Mississippi Valley into the Ohio Valley and Mid-Atlantic, with another
couple of cold fronts coming in behind it. Additionally, a Bermuda High
and troughing in the Southwest will direct both Gulf of Mexico moisture
and ample monsoonal moisture into these regions, providing an environment
favorable for multiple rounds of rain and thunderstorms through the end of
the workweek. While some strong to severe thunderstorms are possible, the
bigger threat will likely be additional flash flooding, given that high
rain rates are expected and because rain is likely to fall in the same
areas on multiple days on increasingly sensitive/saturated ground
conditions in this stagnant pattern with bountiful moisture. A Moderate
Risk (level 3/4) of excessive rainfall is in effect through tonight across
much of the Lower Ohio Valley and Central Appalachians, meaning numerous
flash floods are likely, shown by Flood Watches as well. This risk
persists through Wednesday and Thursday over much of West Virginia into
eastern Kentucky. Broad Slight Risks extend farther west and south into
portions of the Middle/Lower Mississippi Valley and Tennessee Valley as
well, where flash flooding is also possible.

Additionally, anomalously moist inflow is likely to continue across the
Southwest for the next few days, where the monsoon began earlier than
usual and has been persistent. This will lead to daily development of
heavy showers and thunderstorms throughout the Four Corners states in
particular but also into southern Nevada and southeastern California.
Areas most vulnerable to flash flooding remain areas near burn scars, in
slot canyons, in locations that have overly saturated soils, and in more
heavily urbanized areas of the Southwest. For this afternoon/evening into
tonight, a Moderate Risk of excessive rainfall is in place across
northwestern Arizona where there could be an enhanced chance of flash
flooding effects, embedded within a broad Slight Risk that could also see
flooding issues. Another sizable Slight Risk persists through Wednesday.
The core of the moisture is forecast to move eastward by around Thursday
and focus likely heavy rainfall across eastern Colorado, where a Moderate
Risk has been added within a Slight over central parts of the Rockies and
High Plains.

Meanwhile, another threat over the next couple of days will be the heat
underneath upper level ridges stretching from the southern tier of the
U.S. up into the Northwest. Excessive Heat Warnings and Heat Advisories
remain in place today across parts of the Southern Plains and Lower/Middle
Mississippi Valley, where oppressively higher dew points lead to sultry
heat indices as high as 110 degrees. The Southern Plains and Lower
Mississippi Valley are to remain mired in stifling heat until late week
when a cold front brings much needed relief in the form of cooler
temperatures positioned in the Midwest. The ridging atop the Southeast
will keep hot and humid conditions in the forecast with temperatures
growing increasingly hotter up and down the East Coast by Thursday. The
northwestern U.S. can also expect anomalously hot conditions, with another
section of Excessive Heat Warnings and Heat Advisories. Some daily records
could be set as highs soar into the triple digits in the Columbia Basin
and central Oregon, while the Portland metro area nears 100 degrees with
Seattle in the 90s through Friday. The coolest temperatures will be found
in the Great Lakes, Midwest, and Southwest.


Tate/Mullinax


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