U.S. Day 3-7 Hazards Outlook
For the most up to date information on the flooding areas, please refer to the National Flood Outlook
US Day 3-7 Hazards Outlook
NWS Weather Prediction Center College Park MD
405 PM EDT Wed Jun 21 2023
Valid Saturday June 24 2023 - Wednesday June 28 2023
Hazards:
- Heavy rain across portions of the Northern Plains and Upper Midwest, Sat, Jun 24.
- Heavy rain across portions of the Mid-South, Sun, Jun 25.
- Heavy rain across portions of the Mid-Atlantic and the Northeast, Tue-Wed, Jun 27-Jun 28.
- Severe weather across portions of the Middle Mississippi Valley, Sat, Jun 24.
- Flooding possible across portions of the Central Plains and the Northern Plains.
- Flooding occurring or imminent across portions of the Northern Rockies and the Northern Great
Basin.
- Flooding likely across portions of the Southeast and the Northern Plains.
- Excessive heat across portions of Texas and Lower Mississippi Valley, Sat-Wed, Jun 24-Jun 28.
- Excessive heat across portions of the Southern Plains and Lower Mississippi Valley, Sat-Sun, Jun
24-Jun 25 and Wed, Jun 28.
- Heavy rain across portions of the Alaska Panhandle and mainland Alaska, Sat-Sun, Jun 24-Jun 25.
- High winds across portions of mainland Alaska, Sun, Jun 25.
Detailed Summary:
...CONUS...
The main focus during the day 3-7 hazards period (Saturday June, 24 - Wednesday June, 28) will be
the ongoing excessive heat over portions of the south-central U.S., with the epicenter being Texas.
A stagnant upper-level ridge has been in place for days over the region and looks to remain in
place through the forecast period, with small adjustments in placement and influence of passing
troughs to the north dictating the exact coverage of excessive heat each day. High temperatures
across portions of the Southern Plains into the Mid-South will cool a bit following a passing
trough to the north before warming back up towards the end of the period. In addition, temperatures
will also start to warm in portions of the Southwest as the ridge builds westward, and an expansion
of the excessive heat area may be required in subsequent outlooks. Of particular note is that the
source of excessive heat is not equal across the region. For eastern portions of the outlook area,
southeasterly onshore flow from the Gulf will keep dewpoints in the upper 60s to mid-70s, which
when combined with temperatures in the upper 90s to low 100s will lead to heat indices in the
105-110 degree range for northern portions of the outlook area and 110-115, locally as high as 120,
in southeastern portions of the outlook area near the Gulf Coast. To the West, while dewpoints will
not be as high, very hot temperatures in the 105-110 degree range, locally 110+, will still pose a
major risk to the public, especially for those without access to adequate air conditioning.
Numerous daily near-record and record breaking highs are possible across the outlook area.
Overnight lows will also be abnormally warm, at or above record levels, providing no relief from
the excessive heat overnight. The long-term outlook continues to indicate that this heat wave will
likely last beyond the current forecast period.
To the north, a shortwave will round the northern edge of the ridge over the Northern Plains and
Upper Midwest. At the same time, an accompanying low pressure/frontal system will consolidate and
organize over the Plains, moving northeastward through the same region. Strong low-level flow
accented by an evening low-level jet will advect a stream of deep moisture northward ahead of an
eastward moving cold front and over a northward moving warm front, providing the fuel and focusing
mechanisms for the development of widespread, organized convection with the potential to produce
very heavy rain over portions of the Northern Plains and Upper Midwest on Saturday (June 24). The
model guidance indicates moderate to high probabilities of areal average rainfall over 1" with the
potential for locally heavy totals of 2-4". In addition to heavy rainfall, the Storm Prediction
Center has highlighted the risk for severe weather as moderate to strong deep-layer and low-level
shear will lead to some organized supercell thunderstorms with the potential to produce large hail,
damaging winds, and tornadoes. As the upper-level shortwave deepens over the eastern U.S. and the
frontal system presses eastward, additional areas of heavy rainfall look likely through the
remainder of the forecast period. Southerly flow ahead of the eastward moving cold front will
advect a second surge of Gulf moisture northward across the Mid-South on Sunday (June 25). Vigorous
thunderstorm development Sunday afternoon and evening supported by moderate to high CAPE values may
lead to some locally heavy downpours, with guidance indicating amounts of 2-3" possible.
Southeastward moving convection may also organize overnight leading to more widespread heavy
rainfall.
Several days of moderate to locally heavy rainfall are expected to continue along the East Coast as
one lingering frontal system dissipates and the next upper-level trough/frontal system approaches
from the west. Portions of the Southeast into the Mid-Atlantic may see locally heavy rainfall on
Monday (June 26), but the lack of a specific focus area given a widespread warm-sector currently
makes it difficult to pin down any specific threat area. However, it appears likely that at least
one area of heavy rainfall will eventually be needed given the model signal for widespread showers
and storms. Continual anomalously moist, southerly flow over portions of the Northeast/New England
following the departure of the initial frontal system and subsequent approach of the next system
will keep rainfall chances up over this region in particular through the forecast period. The
upper-level trough and accompanying surface frontal system are forecast to slow and stall over the
region next Tuesday/Wednesday, leading to the potential for more focused rounds of training showers
and storms increasing to the risk for locally heavy rainfall totals. The model guidance reflects
this potential with moderate probabilities of areal average rainfall over 1", with the potential
for locally heavy totals of 2-3"+.
...Alaska...
Over Alaska, the pattern looks to remain rather stagnant as an upper low parks itself over the
southern Bering Sea allowing a couple of shortwaves to send surface systems into the Gulf of
Alaska. A fetch of Pacific moisture will move towards the coast and contribute to the potential for
some heavy rainfall Saturday and particularly Sunday for Kodiak Island and the southern Coast
region. There is the potential this rainfall may continue further into the week, but there is
currently not enough consistency in the forecast in the model guidance to be confident in this
scenario. Strong, gusty winds will also be possible on Sunday as the approach of the frontal system
and deepening low pressure in the Gulf locally tighten the pressure gradient along portions of the
southern Coast.
Putnam
