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FXUS21 KWNC 301839

PMDTHR

US Hazards Outlook

NWS Climate Prediction Center College Park MD

300 PM EDT April 30 2024



SYNOPSIS: Multiple models continue to indicate mid-level high pressure across 

the south-central and southeastern contiguous U.S. (CONUS) from the beginning 

to middle of week-2, supporting increased chances for excessive heat across 

these regions. However, there continues to be significant model uncertainty 

regarding the details of the mid-level pattern, with the ECENS ensemble mean 

favoring higher amplitude and more expansive mid-level high pressure than the 

GEFS. Mid-level low pressure upstream across the western and north-central 

CONUS supports increased chances for episodes of heavy precipitation across 

parts of the Mississippi, Ohio, and Tennessee Valleys, and Southern 

Appalachians and enhancing flood risk in some of these areas.



HAZARDS



Moderate risk of excessive heat for parts of the Southeast and Lower 

Mississippi Valley, Wed-Fri, May 8-10.



Slight risk of excessive heat for parts of the Southern Plains, Lower 

Mississippi Valley, and Southeast, Wed-Sat, May 8-11.



Slight risk of periods of heavy precipitation across parts of the Mississippi, 

Ohio, and Tennessee Valleys, and Southern Appalachians, Wed-Sun, May 8-12.



Slight risk of episodes of high winds for parts of the Interior West, Wed-Fri, 

May 8-10.



Possible flooding over parts of the Mississippi Valley.



DETAILED SUMMARY



FOR FRIDAY MAY 03 - TUESDAY MAY 07: 

https://www.wpc.ncep.noaa.gov/threats/threats.php



FOR WEDNESDAY MAY 08 - TUESDAY MAY 14: The week-2 forecast mean mid-level 

height pattern favors more expansive positive 500-hPa height anomalies across 

the Gulf Coast compared to yesterday. This translates to increasing signals for 

excessive heat across the region. A slight risk of excessive heat is 

highlighted across parts of the Southern Plains, Lower Mississippi Valley, and 

Southeast, May 8 to 11, where the GEFS and ECENS probabilistic extremes tools 

(PETs) show at least a 20% chance of maximum temperatures exceeding the 90th 

percentile, climatologically, and 90 Deg F (95 Deg F across western and 

southern Texas). An embedded area is designated with a moderate risk (40 to 60% 

chance) of excessive heat due to increasing heat signals, both in dry air 

temperature and heat index tools. The ECENS (GEFS) PET shows at least a 50% 

(40%) chance of maximum temperatures exceeding the 85th percentile across the 

Lower Mississippi and Tennessee Valleys, and Southeast during the 8 to 10 day 

period (May 8-10).  The National Blend of Models (NBM) forecasts record high 

temperatures in the low to mid 90s across the Lower Mississippi Valley, Florida 

and Southern Carolina and triple digits in the Big Bend area in Texas.  







Upstream, mid-level troughing continues to be predicted, although there 

continues to be significant model differences. The ECENS ensemble mean 

continues to favor mid-level troughing over the northwestern CONUS, whereas the 

GEFS counterpart is further east over the north-central CONUS. Despite these 

differences, this pattern would favor surface low formation over the central 

CONUS, shifting northeastward from the beginning to middle of week-2. A slight 

risk of heavy precipitation is posted for periods of heavy precipitation across 

parts of the Mississippi, Ohio, and Tennessee Valleys, and Southern 

Apppalachians, May 8 to 12, where the ECENS PET indicates at least a 20% chance 

of 3-day precipitation totals exceeding the 85th percentile and one inch and 

where positive precipitation anomalies are indicated in the GEFS daily ensemble 

means. A broad period is designated for the risk due to uncertainty in timing 

of heavy precipitation, rather than the expectation for heavy rain to last 

multiple consecutive days. Recent deterministic GFS runs show enhanced 

convective available potential energy (CAPE) that could be conducive for 

thunderstorms in the highlighted risk area.







Saturated soils in addition to expected antecedent heavy rainfall during week-1 

and predicted week-2 heavy rainfall supports increased likelihood for flooding 

for portions of the Mississippi Valley. This highlighted flood risk area is 

based on where the National Water Center’s experimental flood outlook shows 

possible flooding in the 4-7 day period and where there is a slight risk of 

heavy precipitation during week-2.







Aforementioned surface low pressure in the lee of the Rockies paired with 

surface high pressure over the North Pacific supports a broad area of tight 

pressure gradient across the Interior West and resultant increased chances for 

high winds. A slight risk of episodic high winds is designated across parts of 

the Mississippi, Ohio, and Tennessee Valleys, and Southern Appalachians, May 8 

to 10. The ECENS PET shows at least a 20% chance of wind speeds exceeding the 

85th percentile and 20 mph across the highlighted risk area. Anticipated 

increased potential for high winds combined with dry soils and antecedent and 

expected dry conditions supports enhanced risk for wildfires, especially across 

the Big Bend of Texas, New Mexico, and Arizona, where the National Interagency 

Fire Center (NIFC) shows moderate risk of significant fire potential by day 7.







In the Southeast, above-normal temperatures and near- to below-normal 

precipitation is forecast during weeks-1 and 2. In parts of the central Florida 

peninsula soil moisture levels are declining due to limited precipitation in 

recent weeks and months. Recent weeks have seen areas of abnormal dryness (D0) 

developing and expanding across both of these regions. As we approach the 

middle of May, increasing sun angles and temperatures in the 80-90 Deg F could 

lead to further drying of soils and potentially lead to drought conditions 

across this region. Therefore, an area of rapid onset drought (ROD) is posted 

for portions of central Florida.







In Alaska, as we move into the middle of May snowmelt season is underway and 

frozen rivers will begin to break up in the near future.This leads to the 

potential for river flooding related to ice-jams. We continue to monitor the 

situation but currently there are no indications of impending major river 

break-ups so no flooding-related hazards are posted at this time.



FORECASTER: Melissa Ou 



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