484
FXUS21 KWNC 101805
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JULY 10 2024
SYNOPSIS: MID-LEVEL HIGH PRESSURE IS FORECAST OVER MUCH OF THE CONTIGUOUS U.S.
(CONUS) FAVORING CONTINUED CHANCES OF EXCESSIVE HEAT CONDITIONS, PARTICULARLY
ACROSS NORTHERN PORTIONS OF THE INTERIOR WEST DURING WEEK-2 AND LINGERING
ACROSS THE MID-ATLANTIC AND SOUTHEAST AT THE BEGINNING OF THE PERIOD FROM THE
END OF WEEK-1. SOUTHERLY MOIST FLOW INTO THE SOUTHWEST RESULTS IN INCREASED
CHANCES FOR LOCALIZED PERIODS OF HEAVY PRECIPITATION ACROSS NEW MEXICO AND THE
UPPER RIO GRANDE. PERIODS OF POTENTIALLY HIGH WINDS ACROSS THE CASCADES,
SOUTHWESTERN OREGON, AND CENTRAL AND NORTHERN CALIFORNIA MAY INCREASE THE RISK
FOR WILDFIRES IN THE AREA.
HAZARDS
SLIGHT RISK OF EXCESSIVE HEAT ACROSS NORTHERN PORTIONS OF THE INTERIOR WEST,
THU-WED, JUL 18-24.
SLIGHT RISK OF EXCESSIVE HEAT FOR PORTIONS OF THE MID-ATLANTIC AND SOUTHEAST
U.S., THU, JUL 18.
SLIGHT RISK OF PERIODS OF HEAVY PRECIPITATION FOR PORTIONS OF NEW MEXICO AND
THE UPPER RIO GRANDE, THU-MON, JUL 18-22.
SLIGHT RISK OF EPISODIC HIGH WINDS FOR PORTIONS OF CALIFORNIA AND THE PACIFIC
NORTHWEST, THU-MON, JUL 18-22.
RAPID ONSET DROUGHT RISK FOR PORTIONS OF THE SOUTHEAST U.S., OHIO AND TENNESSEE
VALLEYS, AND NORTHERN PLAINS.
DETAILED SUMMARY
FOR SATURDAY JULY 13 - WEDNESDAY JULY 17:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR THURSDAY JULY 18 - WEDNESDAY JULY 24: AN AMPLIFIED MID-LEVEL RIDGE IS
FORECAST TO BE CENTERED OVER THE INTERIOR WEST AT THE BEGINNING OF WEEK-2,
GRADUALLY EXPANDING AND SHIFTING EASTWARD OVER TIME. MULTIPLE MODEL ENSEMBLE
MEANS INDICATE PERSISTENT WIDESPREAD POSITIVE 500 HPA HEIGHT DEPARTURES OVER
THE NORTHERN ROCKIES AND NORTHERN PLAINS AT THE START OF THE PERIOD, RESULTING
IN CONTINUED CHANCES FOR EXCESSIVE HEAT ACROSS THESE AREAS. THEREFORE, A SLIGHT
RISK OF EXCESSIVE HEAT IS POSTED ACROSS NORTHERN PORTIONS OF THE INTERIOR WEST
FOR THE ENTIRETY OF WEEK-2, WHERE THE ECMWF AND GEFS PROBABILISTIC EXTREMES
TOOLS (PETS) STILL INDICATE AT LEAST A 20% CHANCE OF MAXIMUM TEMPERATURES
EXCEEDING THE 85TH PERCENTILE AND 95F. A SLIGHT RISK OF EXCESSIVE HEAT REMAINS
HIGHLIGHTED FOR PARTS OF THE SOUTHEAST U.S. AND MID-ATLANTIC, JUL 18, WHERE
MULTIPLE MODELS HAVE THE GREATEST AGREEMENT OF TEMPERATURES EXCEEDING THE
AFOREMENTIONED THRESHOLDS.
POSSIBLE SURFACE LOW FORMATION WITH ADJACENT SURFACE HIGH PRESSURE OVER THE
NORTHERN PACIFIC MAY SUPPORT TIGHT PRESSURE GRADIENTS ACROSS THE NORTHWEST AND
CALIFORNIA, THUS A SLIGHT RISK OF EPISODIC HIGH WINDS IS MAINTAINED FOR THE
CASCADES AND NORTHERN AND CENTRAL CALIFORNIA, JUL 18-22. HOT, DRY, AND WINDY
CONDITIONS ARE LIKELY TO LEAD TO ENHANCED RISK OF WILDFIRES ACROSS WEST COAST
STATES AND INHIBIT EFFORTS TO CONTAIN ANY ACTIVE WILDFIRES.
THE INITIAL POSITION OF THE RIDGE AXIS NEAR THE DESERT SOUTHWEST FAVORS A MORE
ACTIVE MONSOON EARLY IN WEEK-2. MODEL SOLUTIONS FAVOR THE RIDGE ORIENTATION
FURTHER EAST IN THE FOUR CORNERS REGION COMPARED TO YESTERDAY, WHICH WOULD LEAD
TO GREATER CHANCES FOR HEAVY PRECIPITATION ACROSS EASTERN PORTIONS OF THE
REGION. THEREFORE TODAY’S SLIGHT RISK FOR PERIODS OF HEAVY PRECIPITATION IS
POSTED ACROSS NEW MEXICO AND THE UPPER BIG BEND, JUL 18-22. THE PETS INDICATE A
20-30% CHANCE OF 3-DAY PRECIPITATION TOTALS EXCEEDING THE 85TH CLIMATOLOGICAL
PERCENTILE AND 0.5 INCHES THROUGH THE MIDDLE OF THE PERIOD ACROSS THE
HIGHLIGHTED RISK AREA, WITH PETS INDICATING GREATER SPATIAL COVERAGE OF
INCREASED RISK AT THE BEGINNING OF THE PERIOD (JUL 18-20). LOCALIZED FLOODING
IS POSSIBLE ACROSS THIS AREA, ALTHOUGH THERE IS TOO MUCH UNCERTAINTY AT THIS
TIME TO DESIGNATE A FLOOD RISK. THE ECMWF PET ALSO CONTINUES TO INDICATE AT
LEAST A 20% CHANCE OF 3-DAY ACCUMULATED RAINFALL EXCEEDING THE 85TH PERCENTILE
OVER THE MID-ATLANTIC THROUGHOUT WEEK-2. HOWEVER THE HEAVIEST PRECIPITATION
TOTALS ARE PREDICTED TO REMAIN OVER THE OCEAN AND THE GEFS SIGNAL IS MUCH
WEAKER, SO NO ASSOCIATED HAZARD IS POSTED AT THIS TIME.
THE PERSISTENT WARMER AND DRIER THAN NORMAL CONDITIONS OVER AT LEAST THE PAST
MONTH HAVE LED TO A RISK FOR RAPID ONSET DROUGHT FOR PARTS OF THE NORTHERN
PLAINS, OHIO VALLEY (EASTERN CORN BELT), TENNESSEE VALLEY, AND SOUTHEAST U.S.
THE RECENT HEAT WAVES ACROSS THE EASTERN U.S. HAVE EXACERBATED THE ONGOING
DRYNESS ACROSS THIS AREA, AND HAS LED TO MODERATE DROUGHT (D1) FOR MANY AREAS
IN THE EAST. MUCH OF THE AREAS HIGHLIGHTED FOR RISK OF RAPID ONSET DROUGHT HAVE
SEEN LARGE PRECIPITATION DEFICITS OVER THE PAST TWO WEEKS TO A MONTH AND HAVE
SEEN LARGE REDUCTIONS IN AVAILABLE SOIL MOISTURE. THERE IS ADDITIONAL RISK FOR
HIGH EVAPOTRANSPIRATION RATES WITH ABOVE-NORMAL TEMPERATURES FORECAST ACROSS
MUCH OF THE EASTERN CONUS. PERIODIC, LOCALIZED HEAVY PRECIPITATION CANNOT BE
RULED OUT DUE TO FRONTAL AND/OR DAYTIME THUNDERSTORM ACTIVITY, BUT THIS IS
UNLIKELY TO RESULT IN ANY MEANINGFUL CHANGE IN THE POTENTIAL FOR CONTINUED
DEVELOPMENT OF DROUGHT CONDITIONS. DRY SOILS, STRESSED VEGETATION, AND REDUCED
WATER AVAILABILITY DUE TO LOW PONDS AND STREAMS MAY LEAD TO INCREASED IMPACTS
TO AGRICULTURE AND LIVESTOCK, WITH SEVERAL LOCATIONS ALREADY EXPERIENCING
IMPACTS.
FORECASTER: MELISSA OU
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