700
FXUS21 KWNC 261931
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT June 26 2024

SYNOPSIS: Mid-level high pressure across the eastern contiguous U.S. (CONUS) is
forecast for much of the week-2 period and expanding west across the Northern
Plains by the end of the week. Increased chances for excessive heat continue
across much of the eastern CONUS throughout week-2, including the Fourth of
July. The mid-level high is anticipated to suppress precipitation and bring
above-normal temperatures, increasing chances for Rapid Onset Drought across
many parts of the south-central and eastern CONUS. Weak mid-level low pressure
forecast across the north-central CONUS is expected to help limit the northward
extent of any hazardous heat early in the period. Meanwhile, a surge of
moisture is forecast to build into the Southwest at the end of week-1 and into
early week-2, leading to chances of locally heavy rainfall and flooding.



HAZARDS

Moderate risk for excessive heat for portions of the Southeast, Lower
Mississippi and Tennessee Valleys, Southern Plains, and southern Mid-Atlantic,
Thu-Sat, Jul 4-6.

Slight risk of excessive heat for portions of the eastern and central
CONUS,Thu-Wed, Jul 4-10.

Slight risk of excessive heat for portions of the Central and Northern Plains,
Sat-Wed, Jul 6-10.

Moderate risk of heavy precipitation for parts of extreme southern Arizona and
New Mexico, Thu, Jul 4.

Slight risk of periods of heavy precipitation for parts of the Southwest and
Southern Rockies, Thu-Mon, Jul 4-8.

Possible flooding for portions of the Northern and Central Plains, Upper and
Middle Mississippi Valley.

Possible flooding for portions of southern Arizona and New Mexico.

Rapid Onset Drought risk extending from New Jersey and Pennsylvania southward
through western Alabama and northern Florida.

Rapid Onset Drought risk across the eastern Corn Belt.

Rapid Onset Drought risk across portions of eastern Oklahoma, northeastern
Texas, and the surrounding areas.

DETAILED SUMMARY

FOR SATURDAY JUNE 29 - WEDNESDAY JULY 03:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR THURSDAY JULY 04 - WEDNESDAY JULY 10: Excessive heat is possible across the
eastern CONUS throughout much of the week-2 period. The 0z GEFS, ECENS, and
CMCE ensemble means indicate a broad area of mid-level ridging across much of
the central and eastern CONUS early in week-2, before expanding westward by the
end of the period. The GEFS Probabilistic Extremes Tool (PET) depicts some
parts of the Central and Southern Plains, Lower and Middle Mississippi and
Tennessee Valleys and Mid-Atlantic having at least a 40 percent chance of
maximum temperatures exceeding the 85th climatological percentile early in the
week-2 period. Temperatures in the uncalibrated guidance are near 100 deg F
across the Southeast, Mid-Atlantic, and Mississippi Valley, with 105 deg F a
possibility over the Southern Plains. Confidence is highest in these forecast
temperatures early in week-2 but models maintain strong positive temperature
anomalies through much of the period. Dewpoints are also forecast by the GEFS
and ECENS to rise by the end of week-1 and into week-2 across the southern
tier. This is reflected in the National Blend of Models (NBM) which predicts
many minimum temperatures nearing or breaking record high values by the warm
spell, thus limiting any night time relief. As such, a moderate risk of
excessive heat is posted for parts of the southern Mid-Atlantic, Southeast,
Tennessee and Lower Mississippi Valleys and Southern Plains for Jul 4-6. A
broader area of slight risk is maintained for the entire week-2 period. By the
middle to end of the period, the GEFS and ECENS are in agreement regarding a
strengthening mid-level ridge building over the Northern Plains. This feature
may bring increasing temperatures to the Northern Plains by the end of week-2,
approaching excessive heat thresholds. Therefore, a slight risk of excessive
heat is posted for Jul 6-10 across parts of the Central and Northern Plains.



The 0z GEFS and ECMWF ensembles depict multiple shortwave 500-hPa troughs
progressing east from the western to the north-central CONUS overtop the
expanding mid-level ridge. This longwave pattern along with uncalibrated
24-hour precipitation amounts from the GEFS and ECENS support some additional
precipitation across the Northern Plains, Upper Mississippi Valley, and Great
Lakes region during week-2. However, the guidance today is relatively weaker
than prior forecasts resulting in the slight risk of heavy precipitation being
discontinued today. Possible heavy precipitation may continue the enhanced risk
for flooding across the Upper-Mississippi Valley especially across areas
already experiencing flooding, especially across southern Minnesota supporting
the maintenance of a Possible Flood risk centered over Iowa and the surrounding
areas.



Several surges of moisture forecast across the Southwest may support increased
chances for heavy precipitation and flooding across parts of Arizona and New
Mexico. Dewpoints in the 60s are forecast across much of the region through
much of the week-2 period.  Multiple model ensemble solutions indicate the
heaviest precipitation for the end of week-1 into day 8, Jul 4. By day 9,
ensembles have greater dispersion and indicate decreased precipitation amounts
compared to prior forecasts. Therefore, a moderate risk remains posted for
extreme southern Arizona and New Mexico for only Jul 4. A broader slight risk
of heavy precipitation is posted for parts of eastern Arizona and New Mexico
through day 12, Jul 8. Dynamical tools continue to show scattered localized
heavy precipitation across much of the highlighted slight risk region but there
is less confidence relative to prior forecasts. Finally, risk for possible
flooding is designated for southern parts of Arizona and New Mexico where
stronger precipitation signals are depicted in multiple models. Precipitation
is expected to be isolated and not all locations will experience heavy
rainfall. However, flash flooding is possible both where precipitation occurs
and in downstream valleys, particularly in and around burn scars where debris
flows can be triggered by heavy rainfall.



Persistent warmer and drier than normal conditions over at least the past month
have led to a risk for Rapid Onset Drought for parts of the Ohio Valley
(eastern Corn Belt), Mid-Atlantic, Southeast, Southern Plains, and southern
Central Plains. The recent heat waves across the eastern U.S. have exacerbated
the ongoing dryness across many of these areas. Much of the areas highlighted
for risk of Rapid Onset Drought have seen large precipitation deficits over the
past two weeks to a month and have seen large reductions in available soil
moisture. There is additional risk for high evapotranspiration rates with
above-normal temperatures forecast across much of the eastern CONUS. Although
periodic, localized heavy precipitation cannot be ruled out due to frontal
and/or daytime thunderstorm activity. Hot and dry weather is likely to continue
into early July, with a moderate risk (40-60% chance) of excessive heat for
portions of the eastern CONUS. Dry soils, stressed vegetation, and reduced
water availability due to low ponds and streams may lead to increased impacts
to agriculture and livestock, with several locations already experiencing
impacts.

FORECASTER: Ryan Bolt

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