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000
FXUS21 KWNC 151940
PMDTHR
US Hazards Outlook
NWS Climate Prediction Center College Park MD
300 PM EDT April 15 2024

SYNOPSIS: Overall, the week-2 period looks fairly quiet with mid-level ridging
forecast across the contiguous U.S. (CONUS) east of the Rocky Mountains.
Surface high pressure over the eastern CONUS from week-1 will bring slight
chances for a frost or freeze to areas that may damage sensitive vegetation in
portions of the East. This area of high pressure is forecast to progress
eastward into the western Atlantic which will help to bring return flow off the
Gulf of Mexico into the Mississippi Valley and the surrounding areas. This
increases chances for heavy precipitation into these regions. Following the
initial return flow, a trough progressing eastward out of the West may bring
increased chances for heavy rain and thunderstorms into the Central and
Southern Plains. In parts of the Lower-Mississippi flooding remains a concern,
particularly if additional rain falls in this area.

HAZARDS

Slight risk of much below normal temperatures for portions of the Central
Plains, Mississippi, Tennessee, and Ohio Valleys, Great Lakes, and
Mid-Atlantic, Tue, Apr 23.

Slight risk of heavy precipitation across portions of the Central and Southern
Plains, Middle and Lower Mississippi, the Ohio and Tennessee Valleys, Wed-Mon,
Apr 24-29.

Possible flooding across portions of northeastern Texas, extreme southeastern
Oklahoma, and much of the Lower Mississippi Valley.



DETAILED SUMMARY

During week-2, the 500-hPa height pattern remains progressive with a mid-level ridge building into the eastern CONUS early in the period with weak troughing along the West Coast. The trough will progress east during the period where it will eventually eject out of the Rocky Mountains late in week-2.

At the end of week-1 into early week-2, a quick intrusion of below-normal temperatures is forecast into the eastern CONUS. The surface high pressure associated with the cold air may linger into the morning of Day 8. This could bring chances for frost and freezes over parts of the eastern CONUS where vegetation may be susceptible due to relatively early spring warmth across much of the country. The Probabilistic Extremes Tools (PETs) from the GEFS and ECENS are in good agreement for at least a 20% chances of temperatures to fall below 40 deg F. across portions of the Tennessee, Ohio, and Middle-Mississippi Valleys, along with portions of the Mid-Atlantic and southern Great Lakes where the Midwest Regional Climate Center (MRCC) indicates susceptible vegetation. Therefore, a slight risk of much below normal temperatures is indicated for these areas for Day 8, April 23.

As this high pressure progresses eastward over the western Atlantic Ocean, it will help to bring enhanced return flow off the Gulf of Mexico. The PETs from the GEFS and ECENS forecast a large portion of the center of the country to see 3-day precipitation amounts exceed the 85th percentile and 1 inch over the middle and end of the week-2 period. Late in week-2 a trough across the Rockies will progress east into the Plains. This may trigger broad thunderstorm activity with return flow ahead of the trough. This is supported by many of the raw and reforecast tools. Therefore a broad slight risk of heavy precipitation is posted for Central and Southern Plains, the Middle and Lower Mississippi Valley, and the Ohio and Tennessee Valleys, Apr 24-29 which will be monitored going forward.

The Lower Mississippi and Southern Plains region has seen a significant amount of precipitation over the past few weeks and is forecast to receive more precipitation late in week-1. Soils remain quite saturated and any additional precipitation during week-2 would likely induce at least minor flooding. Therefore, a flooding possible shape remains in place across parts of eastern Texas, Louisiana and southern Arkansas.

Across Alaska, troughing early in the period may help to bring increased onshore flow into south-central and Southeast Alaska. However, 3-day precipitation amounts from the PETs remain below 2 inches and it is one of the drier times of year in Alaska, so no corresponding hazard is posted at this time. The trough may also bring below-normal temperatures early in the period to portions of western Alaska.

FOR THURSDAY APRIL 18 - MONDAY APRIL 22:
https://www.wpc.ncep.noaa.gov/threats/threats.php

FOR TUESDAY APRIL 23 - MONDAY APRIL 29:

FORECASTER: Ryan Bolt

$$