740
FXUS21 KWNC 051911
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT June 05 2025

SYNOPSIS: Mid-level high pressure is favored over the eastern half of the
Contiguous U.S. (CONUS) throughout week-2, leading to the development of
potentially hazardous heat over portions of the Midwest, Ohio Valley, and
Mid-Atlantic. Strong surface high pressure over the North Atlantic favors
abundant Gulf moisture to move over the Great Plains, leading to elevated heat
indices and also fueling potentially heavy rainfall along the Gulf coast and
also over portions of the Great Plains and Mississippi Valley. Mid-level low
pressure over the Pacific Northwest at the outset of week-2 has the potential
to bring periods of high winds to much of the northwestern CONUS through the
middle of the forecast period.

HAZARDS

Slight risk of extreme heat for the Mid-Atlantic, Sat-Mon, Jun 14-16.

Slight risk of extreme heat for portions of the Central Great Plains, Middle
Mississippi and Ohio Valleys, Sat-Thu, Jun 14-19.

Slight risk of episodic high winds for the northwestern CONUS, Fri-Mon, Jun
13-16.

Slight risk of heavy precipitation for much of the eastern Great Plains and
Mississippi Valley, and the Gulf and South Atlantic coasts, Fri-Sun, Jun 13-15.

Possible flooding for much of the Middle to Lower Mississippi Valley and
eastern Central and Southern Plains.

DETAILED SUMMARY

FOR SUNDAY JUNE 08 - THURSDAY JUNE 12:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR FRIDAY JUNE 13 - THURSDAY JUNE 19: Ensemble means from the GEFS, ECENS, and
CMCE for 500-hPa height anomalies depict an amplified trough situated over the
West Coast during week-2, although this feature is favored to weaken throughout
the forecast period. Associated with this is weak surface low pressure over the
Great Basin, which along with strong surface high pressure over the North
Pacific sets up a tight pressure gradient and resultant enhanced surface winds
across the northwestern CONUS. This is supported by the Probabilistic Extremes
Tools (PETs) from the ECMWF, which broad-brushes at least a 20% probability of
3-day maximum wind speeds exceeding the 85th climatological percentile for the
first half of the outlook period over this region. The CMCE and GEFS PETs are
less bullish but still show some signal over these areas for at least a portion
of the forecast period. Solutions for mean sea level pressure (MSLP) from the
aforementioned model ensembles are quite consistent with regard to the position
and duration of the tightest pressure gradients over the region despite the
mixed signals from the PETs, with agreement regarding decreasing likelihood for
high winds over the week. Therefore a slight risk of high winds is posted for
the Pacific Northwest, Great Basin, and Northern California for Jun 13-16.



A strong Bermuda high is favored by the ensembles throughout week-2, setting up
moist southeasterly flow off the Gulf and into the central CONUS. The models
also indicate weak troughing east of the Rockies which is anticipated to pair
up with the Gulf moisture and lead to significant daytime heating and
potentially heavy precipitation for much of the eastern Great Plains,
Mississippi Valley, and the Gulf and South Atlantic Coasts. This enhanced
rainfall signal is well-supported by the ECMWF and GEFS PETs, which both
indicate at least a 20% chance of 3-day precipitation totals exceeding the 85th
percentile and at least 1 inch of precipitation for at least part of week-2.
The ECMWF is especially bullish, suggesting this potential throughout the
forecast period, while the GEFS only reaches the above thresholds early in
week-2. Given this, a slight risk of heavy rain is posted for the Eastern
Plains, Mississippi Valley, and the Gulf and South Atlantic coasts for Jun
13-15. Additionally, the Middle Mississippi Valley has been plagued by surplus
precipitation and subsequent flooding during the spring and the ground has not
had time to drain much, so new or renewed flooding is a concern, warranting the
posting of a possible flood hazard for the region. Just north of the primary
flood region of the Middle to Lower Mississippi Valley and eastern portions of
the Central and Southern Plains is a relatively dry region (Iowa, northern
Illinois, and far northern Missouri), which has reported low soil moisture
(lowest one-third of the historical distribution) over the past 30-days. This
region of relatively dry soils is being monitored for a potential ROD (Rapid
Onset Drought) designation.



Model ensembles are in fairly good agreement with regard to a persistent
mid-level ridge over areas east of the Rockies, with widespread 6-12 dm
positive 500-hPa height anomalies throughout the week and heights as much as
593 dm at the ridge axis. This favors anomalously warm temperatures which, when
combined with high humidities due to advection of Gulf moisture, results in
potentially hazardous heat for much of the middle of the CONUS. Heat index
values near 100 deg F fall just a bit short of hazardous thresholds for
mid-June, but this is offset slightly by the longer (expected) duration of this
event. The PETs indicate at least a 20% chance of maximum temperatures
exceeding the 85th percentile and at least 90 deg F for much of the Central
Plains eastward across the Middle Mississippi and Ohio Valleys beginning on
June 14th and extending through the end of the forecast period. Similar
thresholds are reached for the Mid-Atlantic for Jun 14-16, therefore a slight
risk of extreme heat is posted for these regions for the respective time
periods indicated. The Mid-Atlantic heat is predicted to wane after the 16th of
June, as the Midwestern ridge shifts westward and 500-hPa heights fall over the
Northeast and Mid-Atlantic regions. Though slight risks of extreme heat are
posted for both areas, even though air temperatures may fall a bit short of
hazardous thresholds for mid-June, this heat event is expected to be the first
of the season, last at least several days, and be accompanied by high levels of
humidity. Temperatures are likely to be quite hot across the southern CONUS but
hazard criteria are not likely to be met outside the regions discussed above.



Ice-bound rivers are slow to break up in the North Slope of Alaska. There is no
associated hazard posted at this time but this situation will be closely
monitored in the coming days and weeks as conditions can quickly change,
leading to the potential for ice jams, aufeis (a sheet-like mass of layered ice
that forms from successive flows of ground or river water during freezing
temperatures), and associated flooding.

FORECASTER: Anthony Artusa

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