746
FXUS21 KWNC 011933
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT June 01 2026

SYNOPSIS: Mid-level high pressure forecast over southern Canada is expected to
bring above-normal temperatures for much of the lower 48, with a lingering
potential for extreme heat conditions over parts of the Great Plains,
Mississippi and Ohio Valleys, and Great Lakes heading into next week.  The
combination of unseasonable late spring warmth and inadequate rainfall amounts
supports the continuation of a Rapid Onset Drought (ROD) risk over portions of
the Mississippi and Ohio Valleys and Great Lakes.

HAZARDS

Slight risk of extreme heat for portions of the Northern and Central Plains,
Upper and Middle Mississippi and Ohio Valleys, and Great Lakes region, Tue-Thu,
June 9-11.

Possible Rapid Onset Drought for parts of the Upper and Middle Mississippi
Valley, Ohio Valley, and Great Lakes region.

DETAILED SUMMARY

FOR THURSDAY JUNE 04 - MONDAY JUNE 08:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR TUESDAY JUNE 09 - MONDAY JUNE 15: By early next week, there continues to be
good model agreement featuring an amplifying 500-hPa ridge center positioned to
the south of Hudson Bay, with a broad coverage of positive height departures
overspreading much of the entire CONUS.  While some troughing is favored over
the eastern Pacific and West Coast, much of the anomalous ridging is expected
to promote widespread above-normal late spring temperatures with the potential
for the development of extreme heat conditions over portions of the Midwest in
proximity to the ridge center.  Based on both the GEFS and ECWMF ensembles, the
strength of the anomalous ridge center looks to peak on days 7 and 8 (Jun 8-9),
followed by a gradual deamplification of the anomalous ridge center to allay
any associated heat risks later next week.  However, it is at these leads where
the ECMWF and GEFS ensembles also diverge in regards to the evolution of the
pattern, leading to added uncertainty in the updated outlook. The ECMWF
ensemble continues to favor building a strong ridge center over the
northwestern CONUS, where the coupling of more troughing over the northern
Pacific and southeastern CONUS looks to become more consistent with a positive
Pacific North America (+PNA) pattern towards the middle of June.  By contrast,
the GEFS maintains much of the troughing (ridging) over the West Coast (central
CONUS), along with a fairly deep, but weak mean trough over much of eastern
North America later in week-2.



For temperatures, a slight risk of extreme heat remains posted for the
north-central CONUS where the GEFS and ECMWF Probabilistic Extreme Tools (PETs)
most agree in their depiction of increased chances (20-40%) for maximum
temperatures exceeding the 85th climatological percentile, and remains valid
through Jun 11 as the ridging aloft deamplifies. The highlighted slight risk
area captures the strongest positive temperature departures favored among the
dynamical models, with the heat index values potentially reaching 100 deg F.
Over time, the ECWMF PET features a split of the warm signals, with one maxima
in percentile space advancing eastward into the northeastern CONUS, and another
building across the West Coast and Interior West by days 9 and 10.  This
development is less supported by the GEFS PET which maintains increased heat
signals over the northern two thirds of the CONUS, likely tied to the
persistent, but weaker ridging favored.  Based on the GEFS AI and Canadian
ensembles which feature more troughing over the western CONUS, this better
aligns with the cooler GEFS guidance. Therefore, no additional temperature
hazards are posted but this potential will be closely monitored in upcoming
outlooks.



Over the past several weeks, precipitation has been quite limited over portions
of the Great Lakes region and Middle and Upper Mississippi Valley following a
wet spring in these regions. The U.S. Drought Monitor shows an expansion of
abnormally dry conditions into portions of Minnesota, Wisconsin, eastern Iowa,
northern Illinois, and adjacent Indiana in its latest update. Although near to
slightly above-normal precipitation is favored during week-2, the lack of total
precipitation forecast combined with favored above-normal temperatures to drive
increased evaporation rates supports the continuation of Rapid Onset Drought
(ROD) risk. This risk has been expanded to now include parts of northwestern
Indiana based on poor soil moisture percentiles forecast.



For precipitation, moist return flow from the Gulf is expected to keep much of
the southern tier of the U.S. above-normal during week-2.  While the
uncalibrated GEFS and ECMWF feature increased chances for 3-day amounts
exceeding an inch over the Florida peninsula through the middle of week-2,
these tools, as well as the PETs are at odds with the timing of a heavy
precipitation risk, prompting the removal of the slight risk of heavy
precipitation in the outlook. Moreover, the potential for enhanced rainfall may
serve to be more beneficial for parts of Florida and the Southeast which
continue to register severe to exceptional drought conditions. Any advection of
tropical moisture over the southern CONUS appears more likely to be sourced
from the eastern Pacific tied to potential tropical cyclone development. As of
11am PDT, the National Hurricane Center (NHC) is currently eyeing two areas for
formation in the eastern Pacific, with one located to the south of Mexico (30%
chances for development during the next seven days). Should any development
occur next week associated with the area south of Mexico, a northwestward track
nearing the Gulf of California could bring enhanced moisture and increased
precipitation into the lower Four Corners.



In Alaska, river ice breakup season is ending, but many rivers north of the
Brooks Range remain icebound. River breakup flooding can occur with little or
no notice as conditions on frozen rivers can change quickly, so please check
with the Alaska Pacific River Forecast Center for the latest conditions and
advisories. In addition, there is some model support for an influx of tropical
moisture over parts of coastal Gulf of Alaska during week-2 associated with the
recurving of tropical cyclone Jangmi (currently at Tropical Storm strength in
the western Pacific).  No hazards are issued at this time, but this potential
will continue to be monitored.

FORECASTER: Nick Novella

$$