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U.S. Week-2 Hazards Outlook - Made May 08, 2025 | About the Hazards Outlook
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| Composite Map Day 8-14 |
Experimental Probabilistic Outlooks |
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Valid Friday May 16, 2025 to Thursday May 22, 2025
US Hazards OutlookNWS Climate Prediction Center College Park MD
300 PM EDT May 08 2025
Synopsis: An area of mid-level low pressure over the western Contiguous U.S. (CONUS) at the outset of week-2 is favored to shift eastward, leading to increased potential for heavy precipitation and new or renewed flooding to portions of the Southern Plains and Lower Mississippi Valley and the surrounding regions. Multiple days of anomalously warm temperatures may reach hazardous thresholds at times across parts of the Rio Grande Valley.
Hazards
- Slight risk of heavy precipitation for portions of Southern Plains, Lower and Middle Mississippi, Lower Ohio, and Tennessee Valleys, Fri-Mon, May 16-19.
- Slight risk of excessive heat for portions of the Rio Grande Valley, Fri-Sun, May 16-18.
- Flooding Possible for portions of the Southern Plains and Lower Mississippi Valley.
For Sunday May 11 - Thursday May 15: WPC Days 3-7 U.S. Hazards
For Friday May 16 - Thursday May 22: Ensemble means from the GEFS, ECENS, and CMCE for 500-hPa heights depict an amplified trough coming ashore over the West Coast during week-1 and spreading over the western CONUS by the outset of week-2, along with vigorous lee cyclogenesis and a deep surface low over the Great Plains. This synoptic setup favors moist southerly flow off the Gulf and into the Southern Plains and Mississippi Valley, increasing the potential for heavy precipitation across a region already impacted by repeated rounds of excessive rainfall. The GEFS, ECMWF, and CMCE Probabilistic Extremes Tools (PETs) for heavy precipitation all indicate at least a 20% chance of 3-day precipitation totals exceeding the 85th climatological percentile and at least 1 inch for much of the forecast period across some portion of the Southern and Central Plains and into the Lower and Middle Mississippi Valley. There is better agreement among the tools today for the area of heaviest precipitation to be centered across the ArkLaTex region but with precipitation chances extending through much of the middle Mississippi Valley for the beginning and middle of week-2. Therefore, a slight risk of heavy precipitation is posted for this region for May 16-19.
The southern portions of the highlighted slight risk of heavy precipitation have had widespread amounts of four or more inches of rain in the past seven days and eight or more in the last 30. The current 7 day QPF shows a dry period for the week-1 period which may allow time for soils to recover but another significant round of precipitation could once again lead to increased chances for flooding. Therefore, a flooding possible risk is forecast for parts of the Southern Plains and Lower Mississippi Valley.
As this system evolves, enhanced southerly flow is anticipated to develop over the Great Plains. There are indications of this from the GEFS and ECMWF PETs where the forecast maximum wind speed, particularly over the Southern Plains, indicate at least a 20% chance of 3-day maximum wind speeds exceeding the 85th percentile through the middle of the forecast period. However, absolute wind speeds depicted in these tools do not reach hazardous thresholds so no associated hazard is posted at this time.
Positive 500-hPa height departures are favored over much of the southwestern CONUS during the week-1 period, prior to the development of the previously discussed amplified trough, which may bring excessive heat to parts of the Southwest. These positive height anomalies are forecast to spread into the Southern Plains by late week-1 and into week-2. Anomalously warm temperatures are indicated by multiple models for the lower Rio Grande Valley late in week-1 and extending into early week-2 as a result of this upper-level ridge. The PETs for maximum temperature show a strong signal for anomalous warmth in percentile space and show 20-40% chances for temperatures to exceed 100 degF and approach 105. The NWS heat risk tool indicates major heat risk developing along the Rio Grande at the end of week-1. Multiple days of temperatures near excessive heat thresholds may result in expanded heat risk by the beginning of week 2. Therefore, a slight risk of excessive heat is highlighted for portions of the Rio Grande Valley, May 16-18. Models are showing elevated dew points along the Gulf Coast in addition to the building heat which may lead to elevated apparent temperatures in the area, although tools have lower support for reaching hazardous thresholds at this time. Southern Texas will need to be monitored throughout week-2 as the ECENS is forecasting normalized positive 500-hPa height anomalies persisting or even increasing in magnitude by the end of week-2 which could prolong enhanced chances for excessive heat across the region.
As spring continues and daily incoming solar radiation flux totals increase, ice-bound rivers are beginning to break up in Alaska. There is no associated hazard posted at this time but this situation will be closely monitored in the coming days and weeks as conditions can quickly change, leading to the potential for ice jams and associated flooding.
Forecaster: Ryan Bolt
$$ Please consult local NWS Forecast Offices for short range forecasts and region-specific information.
Resources
Week-2 Probabilistic Extremes Tool
GFS Ensemble Forecasts