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FXUS21 KWNC 141812

PMDTHR

US Hazards Outlook

NWS Climate Prediction Center College Park MD

300 PM EDT May 14 2024



SYNOPSIS: Mid-level high pressure is forecast to expand across the Southern 

Tier of the contiguous U.S. (CONUS) early in week-2. This favors increasing 

chances for anomalously warm temperatures, and excessive heat conditions 

possibly affecting parts of the Southern Plains, Lower Mississippi Valley, and 

the Florida Peninsula. Mid-level low pressure predicted across the northwestern 

and north-central CONUS early in the period could lead to a frontal passage and 

brief moderation of temperatures at the outset of the period, with this and 

additional shortwaves favoring increased chances for episodes of heavy 

precipitation across portions of the central and east-central CONUS. By the end 

of the period, models are in good agreement regarding weakening of the 

mid-level low allowing heights to increase over the western CONUS.



HAZARDS



Moderate risk for excessive heat across southern Texas, Thu-Fri, May 23-24.



Slight risk for excessive heat across portions of the Southern Plains and Lower 

Mississippi Valley, Wed-Tue, May 22-28.



Slight risk for excessive heat across the southern Florida Peninsula, Wed-Tue, 

May 22-28.



Slight risk for heavy precipitation across portions of the Great Plains, 

Mississippi, Tennessee, and Ohio Valleys, and Southeast, Wed-Sat, May 22-25.



Rapid onset drought risk across the southern Florida Peninsula.



DETAILED SUMMARY



FOR FRIDAY MAY 17 - TUESDAY MAY 21: 

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



FOR WEDNESDAY MAY 22 - TUESDAY MAY 28: Subtropical ridging is forecast to 

expand across portions of the south-central CONUS heading into the week-2 

period. This favors increasing chances for anomalously warm temperatures 

stretching from the Central and Southern Plains eastward to the southern 

Mid-Atlantic and Southeast coasts. Given the time of year, many areas away from 

the Gulf Coast are not expected to have temperatures reach excessive heat 

criteria. The strongest signals for excessive heat are across portions of Texas 

where the GEFS and ECMWF Probabilistic Extremes Tools (PETs) depict at least a 

20 percent chance for maximum temperatures exceeding the 85th climatological 

percentile and 90 deg F. The GEFS PET continues to show probabilities above 40 

percent across portions of southern and southwestern Texas, although the ECMWF 

PET generally depicts probabilities under 30 percent early in week-2. A passing 

frontal system may result in more northerly flow and decrease temperatures 

across the South compared to the late week-1 period, and given this possible 

scenario, day-8 (May 22) is removed from the moderate risk of excessive heat. 

The National Blend of Models (NBM) depicts a reduction in coverage of daily 

temperature records on day-8 as well, but increases coverage on days 9 and 10 

(May 23-24), with the ECMWF PET holding off on increasing probabilities for 

maximum temperatures above the 85th percentile until later in the period. Given 

the support from the NBM and the calibrated GEFS heat risk guidance, which 

indicates at least a 30 percent chance heat indices exceed the 95th 

climatological percentile across southern Texas, the moderate risk for 

excessive heat is maintained for May 23-24. Along with the heat, dry conditions 

could also elevate the potential for wildfires across parts of the Four Corners 

into Texas, with troughing upstream possibly elevating wind speeds across the 

region. 







A broader slight risk continues across much of the remainder of Texas 

(excluding the northern portion and the Panhandle), southeastern New Mexico, 

and the Lower Mississippi Valley for all of week-2. For the western side of the 

slight risk area, heat is likely to be temperature driven, but higher dewpoints 

favored across eastern Texas and the Lower Mississippi Valley may push heat 

indices above 105 deg F despite the relatively lower temperatures compared to 

those further west. The slight risk for excessive heat also includes the 

southern Florida Peninsula for all of week-2. The ECMWF PET is very robust 

bringing in hot temperatures across this region by the middle of week-2. The 

NBM also depict some parts of the Peninsula reaching the mid-90s, and combined 

with dewpoints above 70 deg F, would result in heat indices possibly greater 

than 105 deg F. While this would support a moderate risk for excessive heat 

over parts of Florida, pause is given due to the weaker signal in the GEFS. 

Decreasing soil moisture and a warm and dry pattern predicted in week-2 lead to 

increased rapid onset drought risk across parts of south Florida. 







Troughing forecast across the northwestern and north-central CONUS favors 

below-normal temperatures across much of the West, extending into parts of the 

Northern and Central Plains and Upper and Middle Mississippi Valley. The 

resulting temperature contrast is likely to lead to enhanced frontal activity 

across parts of the central and east-central CONUS during week-2, with a 

passing front late in week-1 into the outset of week-2, and possibly another 

shortwave ejecting out of the trough soon after. The ECMWF PET indicates at 

least a 20 percent chance 3-day precipitation totals exceed the 85th 

climatological percentile and 1-inch over portions of the Great Plains, 

Mississippi, Tennessee, and Ohio Valleys, and Southeast through the early and 

middle parts of the period, although the signal in the GEFS PET has decreased 

compared to yesterday. A slight risk for heavy precipitation remains posted 

across the aforementioned areas for 5/22-5/25. 







No hazards are issued for Alaska, with near- to slightly above/below-normal 

temperature probabilities favored for most of the state. Snowmelt season is 

underway and frozen rivers are beginning to break up, leading to the potential 

for river flooding related to ice-jams. However, there are no indications of 

impending major river break-ups or serious threat of ice-jamming so no 

flooding-related hazards are posted at this time. Caution will continue to be 

exercised as river break-up can be unpredictable and local conditions can 

change quickly. Anomalous ridging over the north-central Pacific favors an 

enhanced storm track into western Mainland Alaska, although precipitation 

amounts are expected to remain low and not reach hazards thresholds.



FORECASTER: Thomas Collow 



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