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Composite Map
Day 8-14
Experimental Probabilistic Outlooks
Valid Friday May 16, 2025 to Thursday May 22, 2025
US Hazards Outlook NWS 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 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
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Please consult local NWS Forecast Offices for short range forecasts and region-specific information.