Valid Wednesday April 30, 2025 to Tuesday May 06, 2025
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM
EDT April 22 2025
Synopsis: At the outset of week-2 surface low
pressure is forecast to be departing across the Great Lakes and southeastern
Canada, with a trailing cold front extending across the central and
east-central contiguous U.S. (CONUS). This favors enhanced chances of heavy
precipitation and thunderstorms continuing into the early part of week-2 across
the Central and Southern Plains and Middle and Lower Mississippi, Tennessee,
and Ohio Valleys. Broad mid-level high pressure is forecast to develop across
the CONUS later in week-2, favoring increased chances for above-normal
temperatures over many areas.
Hazards - Slight risk of
heavy precipitation for portions of the Central and Southern Plains and the
Middle and Lower Mississippi, Tennessee, and Ohio Valleys, Wed, Apr 30.
- Possible flooding for the Lower Mississippi River.
Detailed
SummaryFor Friday April 25 - Tuesday April 29:
WPC Days 3-7 U.S.
Hazards For Wednesday April 30 - Tuesday
May 06: Late in week-1, surface low pressure is forecast to track across
the Northern Plains and Upper Midwest. As this system departs, a trailing cold
front is predicted to remain across parts of the Great Plains and Mississippi
Valley early in week-2 serving as a focus for continued increased chances of
heavy precipitation and thunderstorms. The uncalibrated 0z ECENS continues to
depict a swath of heavy precipitation stretching from northeastern Texas into
the Tennessee Valley on day-8 (Apr 30), with the 0z GEFS also showing a wetter
solution over these areas compared to yesterday. The ECENS and GEFS
Probabilistic Extremes Tools (PETs) depict these areas having at least a 20
percent chance precipitation totals exceed the 85th climatological percentile
and 1-inch. As a result, a slight risk of heavy precipitation is posted across
portions of the Central and Southern Plains and the Middle and Lower
Mississippi, Tennessee, and Ohio Valleys, Apr 30. Thereafter, enhanced
precipitation chances are forecast to shift into Texas and along the Gulf
Coast. However, daily precipitation totals are generally low in the GEFS and
ECENS ensembles (less than 0.5 inches), and the isolated, convective nature of
the precipitation precludes extending the hazard.
The convective and sporadic nature of the precipitation during week-2 leads
to less confidence in determining exact areas most at risk of additional
flooding, although localized flooding is a concern over portions of the Central
and Southern Plains that do receive heavy rainfall. A possible flooding hazard
remains posted across the Lower Mississippi River given the potential for new
and renewed rises in water levels during week-2 tied to any additional rainfall
over the region as well as runoff from rainfall upstream. Main channels are
already very high, and thus are unlikely to have large responses to additional
precipitation. Regardless, tributaries and streams will continue to be
susceptible to renewed flooding or flash flooding if additional rainfall
occurs.
As the aforementioned surface low and associated mid-level trough exit the
region early in week-2, there is some potential for elevated wind speeds across
the northern CONUS. However, the signal in the PETs has diminished compared to
yesterday, with much of the enhanced threat over the Northern Plains timing
off. Probabilities in the GEFS and ECENS uncalibrated guidance for wind speeds
exceeding 20-mph are generally weak (less than 20 percent) and confined to the
Great Lakes and adjacent areas on day-8 (Apr 30). As a result, a slight risk
for high winds is no longer indicated, but some higher wind gusts still cannot
be ruled out, particularly across the Great Lakes in the wake of the frontal
passage.
Anomalous ridging is forecast across the eastern CONUS at the beginning of
the period. This favors a period of unseasonably warm temperatures over much of
the East during the first half of week-2, with models trending warmer across
the region compared to yesterday. The ECENS PET depicts parts of the
Mid-Atlantic and Northeast having at least a 40 percent chance maximum
temperatures exceed the 95th climatological percentile on day-8 (Apr 30), with
daily records a possibility based on the National Blend of Models (NBM). This
translates into actual temperatures potentially well into the 80s deg F over
parts of the Mid-Atlantic, with relatively cooler temperatures (70s deg F)
favored across the Northeast and Ohio Valley. While these temperatures are
noteworthy by late-April and early-May standards, and for some areas could be
the warmest temperatures of the year thus far, no heat related hazards are
issued due to the time of year and lack of adverse impacts. A general trend
toward more broad ridging and a pattern typical of late-Spring is forecast to
emerge over much of the CONUS later in week-2.
Troughing forecast across Alaska favors increased chances for above-normal
precipitation over the southeastern part of the state, with actual
precipitation amounts not expected to reach hazards thresholds. Below-normal
temperatures forecast over many areas favor a delay in seasonal river ice
breakup. However, as temperatures continue to warm, the eventual river ice
breakup may lead to ice jams and associated flooding in the coming weeks.
Forecaster: Thomas Collow
$$
Please consult local NWS Forecast Offices for short range forecasts and region-specific information.
Resources
Week-2 Probabilistic Extremes Tool
GFS Ensemble Forecasts