581
FXUS21 KWNC 171800
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT April 17 2025

SYNOPSIS: An area of surface low pressure and stationary frontal system across
the central and eastern contiguous U.S. (CONUS) brings increased chances for
locally heavy precipitation with flooding possible centered near the Oklahoma
and Arkansas border region during week-2. Due to excessive precipitation
observed in the Mississippi and Ohio River Valleys during the past few weeks,
any above-normal precipitation received may trigger additional flooding in this
part of the country. Windy conditions are possible into parts of the
southwestern CONUS.

HAZARDS

Slight risk of heavy precipitation for portions of the Great Plains,
Mississippi, Tennessee, and Ohio Valleys, and Southeast, Fri-Sat, Apr 25-26.

Slight risk of high winds over the southwestern CONUS, Fri-Tue, Apr 25-29.

Flooding possible for the Middle and Lower Mississippi, and lower Ohio Rivers.

Flooding possible for parts of the Great Plains and Mississippi Valley.

DETAILED SUMMARY

FOR SUNDAY APRIL 20 - THURSDAY APRIL 24:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR FRIDAY APRIL 25 - THURSDAY MAY 01: Early in the week-2 period, a weak
trough is forecast to develop over the West. This may help to develop an area
of surface low pressure in the lee of the Rockies. A stationary front is also
forecast to be draped across the central and eastern CONUS at the onset of the
period. This pattern is suggestive of continued precipitation across portions
of the central and eastern CONUS, some of which may be heavy, due to likely
convective nature of precipitation at this time of year. Therefore, a broad
slight risk of heavy precipitation is forecast for portions of the Plains,
Mississippi, Ohio, and Tennessee Valleys and Southeast, for Apr 25-26.
Following this initial set-up, ensemble guidance has backed off higher
precipitation amounts into the middle and end of week-2. As such, the heavy
precipitation hazard is more limited temporally than prior forecasts.



With copious antecedent rainfall and recurring flooding concerns for portions
of the lower Ohio, Middle and Lower Mississippi Valleys, a flooding possible
hazard remains posted mainly along the Mississippi River given the potential
for new and renewed rises in levels during week-2. While main channels are
already very high, and thus are unlikely to have large responses to additional
precipitation, tributaries and streams will be more susceptible to renewed
flooding or flash flooding if additional rainfall occurs.



Due to heavy precipitation forecast for the coming days over parts of the
Southern and Central Plains and Middle Mississippi Valley, with little reprieve
favored before the heavy precipitation risk returns, a second flooding possible
hazard is posted for portions of these regions. Any locally heavy precipitation
into week-2 could cause new or renewed flooding or flash flooding over the
complex terrain of the Ozarks as well as bring renewed streamflow rises in the
highlighted region.



With good continuity in the models for the development of negative height
departures over the western CONUS, a slight risk of high winds remains posted
for Apr 25-29 and includes much of the Great Basin, Desert Southwest, Rockies,
and High Plains near the base of amplifying trough axis. This continues to be
supported by the ECMWF PET which depicts wind speeds exceeding the 85th
percentile across much of this region through the middle of week-2.



In the Southeast, the PETs from the GEFS and ECENS are highlighting this area
to see maximum temperatures exceeding the 85th climatological percentile for
much of the week-2 period. At this time, most guidance suggests temperatures in
the upper 80s to near 90 deg F, which while not particularly excessive, may
approach record highs, particularly across central Florida and is worth noting.



Outside the CONUS, above normal precipitation and temperatures are
predominately favored over the southern Alaska Mainland, with below normal
temperatures over northern Alaska and the Yukon of Canada tied to an anomalous
ridge center over the Chukchi Sea. This pattern is suggestive of seasonal river
ice breakup being delayed, though as temperatures continue to warm, the
eventual river ice breakup may lead to ice jams and associated flooding in the
coming weeks. Over the central Pacific, 500-hPa troughing is favored to develop
underneath a north Pacific ridge before deamplifying later in week-2. An
accompanying area of surface low pressure is expected to bring reduced trades
mainly north of the Hawaiian Island chain, which could result in locally heavy
precipitation to the northern windward islands.

FORECASTER: Ryan Bolt

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