001
FXUS21 KWNC 181916
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT June 18 2024

SYNOPSIS: A brief respite from excessive heat is favored for much of the
northern contiguous states (CONUS) during the early part of week-2, as several
areas of mid-level low pressure progress across the country. During the second
half of week-2, high heat and humidity are favored to return to the Ohio
Valley, southern Great Lakes, northern and central Appalachians, and
Mid-Atlantic region. Across the western Gulf Coast region, there is an
increased risk of heavy precipitation with flooding possible, though much
depends on the possible formation of another tropical cyclone over the Bay of
Campeche.

HAZARDS

Slight risk of excessive heat for much of the south-central and southeastern
CONUS, Wed-Tue, Jun 26- Jul 2.

Slight risk of excessive heat for the Ohio Valley, portions of the southern
Great Lakes region, the northern and central Appalachians, and the
Mid-Atlantic, Sat-Tue, Jun 29-Jul 2.

Slight risk of heavy precipitation over the western Gulf Coast region, Wed-Tue,
Jun 26- Jul 2.

Flooding possible over much of the western Gulf Coast region.

Slight risk of heavy precipitation for southern Florida, Wed-Tue, Jun 26-Jul 2.

Slight risk of heavy precipitation in the vicinity of the Upper Mississippi
Valley, Wed-Fri, Jun 26-28.

Flooding possible in the vicinity of central and southern Minnesota.

Slight risk of high winds for the High Plains region, Wed-Fri, Jun 26-28.

Rapid Onset Drought risk for much of the Mid-Atlantic and interior Carolinas.

Rapid Onset Drought risk for the Ohio Valley.

DETAILED SUMMARY

FOR FRIDAY JUNE 21 - TUESDAY JUNE 25:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR WEDNESDAY JUNE 26 - TUESDAY JULY 02: One or two cold fronts are forecast to
move across much of the northern one-third to one-half of the CONUS during the
early portion of the week-2 period, accompanied by cooler temperatures and
reduced humidity. The break from the heat, however, is favored to be
short-lived, as another mid-level ridge is expected to develop and strengthen
over northeastern parts of the Lower 48 states during the second half of
week-2, with a return to high heat and humidity. This is supported by the three
ensemble mean model solutions (GEFS, ECENS, and Canadian (CMCE)). The 0z ECENS
solution predicts seasonal or slightly above-normal temperatures across New
York and New England, with high temperatures ranging from the 70s near the
Canadian border to mostly 80s for southern parts of this region. Temperatures
could approach 90 deg F in a few interior portions of the Northeast. The ECENS
and CMCE ensemble means predict the mid-level ridge axis to be near the central
Great Lakes region, which allows for back-door fronts and cooler marine air to
influence the northern Atlantic coastal plain.



Over much of the south-central CONUS, little to no relief of the heat and
humidity is anticipated. Accordingly, there is a slight risk of excessive heat
for this broad area for the duration of week-2. A skill weighted hybrid
excessive heat tool (that considers forecast values of both actual air
temperature and the effect of humidity) depicts much of this region (east of
the Rockies) experiencing heat index values of 105 deg F or greater. West of
the Rockies, where humidity is often less of a factor, actual air temperatures
in the lower elevations of Utah are predicted to reach the mid-upper 90s
during the period. A storm system from the Gulf of Alaska is predicted to move
into the Pacific Northwest early in week-2, gradually reducing daytime high
temperatures across a significant portion of the northwestern CONUS.



For precipitation, there is a slight chance for heavy precipitation across the
vicinity of the Upper Mississippi Valley, Jun 26-28. Precipitation guidance
from the Probabilistic Extremes Tools (PETs), the uncalibrated ECENS, and the
synoptic pattern are generally consistent with this feature. Flooding is also
possible in much of this area, as precipitation has been occurring frequently,
and soil moisture values remain high. A slight risk for heavy precipitation has
also been posted for the western Gulf Coast region and southern Florida based
on objective precipitation guidance, with the PETs favoring at least one-inch
over a 3-day period. The PETs extended the slight risk as far west as the upper
Texas coast, but this risk area was subjectively extended southward to the
Mexican border due to concerns of an additional tropical cyclone potentially
developing in the week-2 period across the Bay of Campeche and tracking north
or northwestward.



Flooding is also possible for coastal areas of Texas and Louisiana, in large
part due to a combination of very heavy rainfall amounts anticipated during the
earlier week-1 period and the possible follow-up with another tropical cyclone
in week-2.



Two areas of Rapid Onset Drought (ROD) are highlighted on todays Hazards map.
One area includes much of the Mid-Atlantic region and interior Carolinas, and
the other area includes much of the Ohio Valley. Much of these areas have
below-normal soil moisture values, and are experiencing 1-4 inch 30-day
precipitation deficits at this time. The expectation of high heat and high
evapotranspiration (ET) rates for the next 2 weeks make this region vulnerable
to rapid onset drought.



The various PET tools agree on high winds (20-25 mph) across the High Plains
during the first three days of the Outlook period. This is attributed to
enhanced downslope flow over the eastern foothills of the northern and central
Rockies and adjacent High Plains.



In the Southwest, the mid-level atmospheric circulation is gradually moving
toward its climatological monsoon circulation, but is not quite there yet. The
expected presence of a mid-level trough across the Northwest, and the lack of a
well-defined subtropical ridge centered over the Four Corners region, support
this idea that the monsoon circulation is still not in place. However,
dynamical models forecast increases in regional dew point temperatures over the
next two weeks, with places like Phoenix and Tucsons values reaching the upper
50s and low 60s deg F. Typically at the beginning of the climatological
monsoon season, the air over the Southwest is still very dry and initial
moisture surges into that region often result in precipitation that falls aloft
but doesnt reach the ground (i.e., virga). This is also a time that is ripe
for dry thunderstorms accompanied by frequent lightning, and locally strong
downburst winds, both of which could increase/exacerbate wildfire activity.

FORECASTER: Anthony Artusa

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