171
FXUS21 KWNC 312035
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JULY 31 2023
SYNOPSIS: WHILE THE DEVELOPMENT OF MID-LEVEL LOW PRESSURE IS FAVORED TO BRING
COOLER THAN NORMAL TEMPERATURES FOR THE NORTHERN HALF OF THE CONTIGUOUS U.S.
(CONUS), RESIDUAL MID-LEVEL HIGH PRESSURE TO THE SOUTH SUSTAINS AN INCREASED
RISK OF EXCESSIVE HEAT ACROSS THE SOUTHERN TIER DURING THE PERIOD. ANTECEDENT
DRYNESS COUPLED WITH LITTLE TO NO RAINFALL AND ABOVE-NORMAL TEMPERATURES
SUPPORTS A RAPID ONSET DROUGHT RISK ACROSS PARTS OF THE LOWER MISSISSIPPI
VALLEY, SOUTHERN GREAT PLAINS, RIO GRANDE VALLEY, AND NEW MEXICO.
HAZARDS
MODERATE RISK OF EXCESSIVE HEAT FROM THE LOWER FOUR CORNERS TO THE LOWER
MISSISSIPPI VALLEY, TUE-FRI, AUG 8-11.
SLIGHT RISK OF EXCESSIVE HEAT FOR MUCH OF THE SOUTHERN U.S., TUE-MON, AUG 8-14.
SLIGHT RISK OF HIGH WINDS FOR THE PORTIONS OF THE LOWER FOUR CORNERS, TUE-SAT,
AUG 8-12.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PARTS OF THE GREAT PLAINS, MISSISSIPPI,
TENNESSEE AND OHIO VALLEYS, TUE-THU, AUG 8-10.
SLIGHT RISK OF MUCH ABOVE-NORMAL TEMPERATURES FOR NORTHERN ALASKA, TUE-THU, AUG
8-10.
RAPID ONSET DROUGHT RISK ACROSS PORTIONS OF THE LOWER MISSISSIPPI VALLEY,
SOUTHERN PLAINS, AND SOUTHWEST.
DETAILED SUMMARY
FOR THURSDAY AUGUST 03 - MONDAY AUGUST 07:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR TUESDAY AUGUST 08 - MONDAY AUGUST 14: HEADING INTO EARLY NEXT WEEK,
DYNAMICAL MODELS HAVE BEEN CONSISTENT IN FAVORING A COOLER PATTERN EMERGING
WITH ANOMALOUS 500-HPA TROUGHING ENVELOPING THE NORTHERN HALF OF THE CONUS.
ALTHOUGH DECREASING MID-LEVEL HEIGHTS ARE CONCURRENTLY FAVORED ACROSS THE
SOUTHERN TIER OF THE U.S., ABOVE-NORMAL TEMPERATURES REMAIN FAVORED TO PERSIST,
AS WELL AS THE POTENTIAL FOR EXCESSIVE HEAT DURING THE PERIOD. LATER IN THE
PERIOD, THERE ARE INDICATIONS IN THE ENSEMBLES FOR ANOMALOUS MID-LEVEL RIDGING
TO REBUILD ACROSS THE EASTERN U.S., THOUGH ANY RENEWED RISK OF EXCESSIVE HEAT
REMAINS UNCLEAR GIVEN MODEL DISPARITIES IN THE EVOLUTION AND STRENGTH OF THE
HEIGHT PATTERN AT THIS LEAD.
A MODERATE RISK OF EXCESSIVE HEAT IS ISSUED FROM THE LOWER FOUR CORNERS TO THE
SOUTHERN PLAINS, WHERE BOTH THE GEFS AND ECMWF PROBABILISTIC EXTREMES TOOLS
(PETS) INDICATE AT LEAST A 40% CHANCE OF MAXIMUM TEMPERATURES EXCEEDING THE
85TH PERCENTILE. A HIGH RISK OF EXCESSIVE HEAT WAS CONSIDERED GIVEN STRONGER
HEAT SIGNALS IN THE ECMWF PET (TIED TO >597-DM HEIGHTS IN THE ECMWF ENSEMBLE
ALONG THE U.S/MEXICO BORDER ON DAY 8), THOUGH THE GEFS AND CANADIAN ARE LESS
SUPPORTIVE OF THIS RISK DESIGNATION BASED ON UNCALIBRATED TEMPERATURE GUIDANCE
AND THE POTENTIAL FOR COOLER AIR TO MIX INTO THE REGION. IN THE HIGHLIGHTED
MODERATE RISK AREA, THERE ARE INCREASED CHANCES FOR DAYTIME TEMPERATURES
EXCEEDING 110 DEGREES F FOR THE SONORAN DESERT, 100 DEG F EASTWARD OVER THE
LOWER ELEVATIONS INTO TEXAS, AND 95 DEG F IN THE HIGHER ELEVATIONS FURTHER
NORTH. A BROAD SLIGHT RISK AREA OF EXCESSIVE HEAT (AUG 8-14). IS POSTED FOR
MUCH OF THE SOUTHERN CONUS AND IN THE FLORIDA PENINSULA, WHERE PETS MAINTAIN AT
LEAST A 20% CHANCE OF MAXIMUM TEMPERATURES EXCEEDING THE 85TH PERCENTILE. WITH
ABOVE-NORMAL TEMPERATURES ESTABLISHED, A SLIGHT RISK OF EPISODES OF HIGH WINDS
IS ISSUED (AUG 8-12) FOR THE LOWER FOUR CORNERS WHERE PETS INDICATE AT LEAST A
20% CHANCE OF WIND SPEEDS EXCEEDING THE 85TH PERCENTILE. WITHIN THE SLIGHT RISK
AREA, CONTINUED DRY AND WARM CONDITIONS ARE LIKELY TO FUEL MANY AREAS CURRENTLY
EXPERIENCING ACTIVE WILDFIRES.
WITH RETURN FLOW FROM THE GULF OF MEXICO FAVORED TO BECOME ESTABLISHED EARLY IN
WEEK-2, DECREASING MID-LEVEL HEIGHTS AND DEEPENING MEAN SURFACE PRESSURE
SUPPORT THE POTENTIAL FOR HEAVY PRECIPITATION OVER THE CENTRAL CONUS. ALTHOUGH
THE GEFS IS COMPARABLY WEAKER THAN THE ECMWF IN REGARDS TO PRECIPITATION TOTALS
EARLY IN THE PERIOD, BOTH PETS SHOW AT LEAST A 20% OF 3-DAY ACCUMULATIONS
EXCEEDING THE 85TH PERCENTILE FOCUSED OVER THE CENTRAL PLAINS AND MIDDLE
MISSISSIPPI VALLEY. THEREFORE, A SLIGHT RISK OF HEAVY PRECIPITATION IS POSTED
FOR AUG 8-10. WITHIN THE SLIGHT RISK AREA, ANY SLOW-MOVING THUNDERSTORMS WITH
LOCALLY HEAVY RAINFALL MAY CAUSE FLASH FLOODING.
A RAPID ONSET DROUGHT (ROD) RISK REMAINS POSTED ACROSS PARTS OF THE LOWER
MISSISSIPPI VALLEY, TEXAS, AND SOUTHERN NEW MEXICO DUE TO THE COMBINATION OF
INCREASING 30-DAY PRECIPITATION DEFICITS, LITTLE TO NO RAINFALL DURING THE NEXT
TWO WEEKS, AND LIKELIHOOD FOR A PROLONGED PERIOD OF HIGH EVAPOTRANSPIRATION
RATES ASSOCIATED WITH MUCH ABOVE-NORMAL TEMPERATURES. FURTHER NORTH, THE ROD
RISK IS DISCONTINUED IN TODAY'S OUTLOOK FOR PARTS OF NORTH DAKOTA WHERE
PRECIPITATION GUIDANCE HAS TRENDED WETTER AND COOLER, AND INCREASED RAINFALL
WAS RECENTLY RECEIVED.
ACCOMPANYING THE ABOVE-NORMAL TEMPERATURES EXPECTED THROUGHOUT THE SOUTHWESTERN
CONUS, BELOW-NORMAL PRECIPITATION IS PREDOMINATELY FAVORED, SUGGESTIVE OF A
WEAKENED MONSOON CIRCULATION. HOWEVER, PROBABILISTIC TROPICAL CYCLONE (TC)
GENESIS TOOLS AND ENSEMBLE SOLUTIONS FAVOR AN UPTICK IN TC ACTIVITY IN THE
EASTERN PACIFIC, WHERE ANY NORTHWARD TRACK NEARING THE GULF OF CALIFORNIA COULD
INITIATE A MOISTURE SURGE EVENT, AND MAY LEAD TO LOCALLY HEAVY PRECIPITATION
ACROSS PARTS OF THE DESERT SOUTHWEST.
OVER ALASKA, MID-LEVEL TROUGHING FORECAST OVER THE ALEUTIANS IS EXPECTED TO
PROMOTE ENHANCED ONSHORE FLOW AND ABOVE-NORMAL PRECIPITATION FOR PARTS OF THE
SOUTHERN MAINLAND AND SOUTHEAST. HOWEVER, AMOUNTS ARE EXPECTED TO REMAIN BELOW
HAZARD THRESHOLDS AND NO CORRESPONDING HAZARDS ARE ISSUED. FOR TEMPERATURES,
STRONG RIDGING FAVORED OVER THE NORTHERN SLOPE IS EXPECTED TO LEAD TO MUCH
ABOVE-NORMAL TEMPERATURES WHERE MANY LOCATIONS NORTH OF THE BROOKS RANGE COULD
SEE DAYTIME TEMPERATURE REACH WELL ABOVE 70 DEGREES F (10 TO 15 DEGREES ABOVE
NORMAL) WHICH MAY BE POTENTIALLY HAZARDOUS TO OUTDOOR WORKERS WEARING HEAVY
EQUIPMENT. THE WARM SIGNAL IS REFLECTED IN THE PETS FOR DAYTIME TEMPERATURES
EXCEEDING THE 85TH PERCENTILE, AND A SLIGHT RISK OF MUCH ABOVE-NORMAL
TEMPERATURES IS ISSUED (AUG 8-10).
FORECASTER: NICK NOVELLA
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page