069
FXUS21 KWNC 301823
PMDTHR
US HAZARDS OUTLOOK
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
300 PM EDT JUNE 30 2023
SYNOPSIS: FOLLOWING A PERIOD OF COOLER TEMPERATURES FAVORED OVER THE GREAT
PLAINS AND MISSISSIPPI VALLEY LATE NEXT WEEK, THERE ARE GREATER CHANCES FOR THE
EXCESSIVE HEAT THREAT TO RETURN ACROSS PARTS OF THE SOUTHERN U.S. TIED TO A
REBUILDING OF MID-LEVEL HIGH PRESSURE. A PAIR OF SURFACE LOWS ARE EXPECTED TO
PROMOTE AN INCREASED RISK OF HEAVY PRECIPITATION OVER THE MIDWEST AND THE
EASTERN U.S EARLY IN WEEK-2. SNOWMELT SEASON CONTINUES FOR AREAS ALONG AND NEAR
THE SIERRA NEVADA MOUNTAINS AFTER EXCEPTIONAL SNOWFALL ACCUMULATIONS, LEADING
TO THE CONTINUED POTENTIAL FOR FLOODING, WHILE ABNORMALLY DRY CONDITIONS OVER
LOUISIANA AND TEXAS RESULT IN THE POTENTIAL FOR RAPID ONSET DROUGHT (ROD).
HAZARDS
MODERATE RISK OF EXCESSIVE HEAT FOR PORTIONS OF THE LOWER FOUR CORNERS AND
SOUTHERN PLAINS, SUN-WED, JUL 9-12.
SLIGHT RISK OF EXCESSIVE HEAT FOR PORTIONS OF THE SOUTHWEST, GREAT BASIN,
SOUTHERN PLAINS, LOWER MISSISSIPPI VALLEY, AND SOUTHEAST, SAT-THU, JUL 8-14.
SLIGHT RISK OF EXCESSIVE HEAT FOR PARTS OF THE PACIFIC NORTHWEST, SAT-MON, JUL
8-10.
SLIGHT RISK OF EPISODES OF HIGH WINDS FOR THE SOUTHWESTERN CONUS, SAT-FRI, JUL
8-14.
SLIGHT RISK OF HEAVY PRECIPITATION FOR MANY PORTIONS OF THE MIDWEST, SAT-MON,
JUL 8-10.
SLIGHT RISK OF HEAVY PRECIPITATION FOR PARTS OF THE MID-ATLANTIC, APPALACHIANS,
GREAT LAKES, AND THE NORTHEAST, SAT-SUN, JUL 8-9.
POSSIBLE FLOODING FOR PORTIONS OF CALIFORNIA AND NEVADA.
RAPID ONSET DROUGHT RISK ACROSS PORTIONS OF LOUISIANA AND EASTERN TEXAS.
DETAILED SUMMARY
FOR MONDAY JULY 03 - FRIDAY JULY 07:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
FOR SATURDAY JULY 08 - FRIDAY JULY 14: DYNAMICAL MODELS HAVE BEEN CONSISTENT ON
THE DEVELOPMENT OF 500-HPA SHORTWAVE TROUGHING LATE NEXT WEEK TO HELP BRING A
SHOT OF ANOMALOUSLY COLD AIR INTO MANY PARTS OF THE GREAT PLAINS AND
MISSISSIPPI VALLEY. THE WEATHER PREDICTION CENTER'S (WPC) DAY 7 SURFACE
ANALYSIS SHOWS A LARGE FRONTAL BOUNDARY EXTENDING SOUTHWARD INTO THE SOUTHERN
PLAINS AND LOWER MISSISSIPPI VALLEY WHICH SHOULD HELP BRING NEEDED RELIEF TO
THE ONGOING HEAT WAVE AND STIFLING TEMPERATURES AFFECTING THE SOUTHERN TIER OF
THE U.S. DURING JUNE. HOWEVER, THESE COOLER CONDITIONS APPEAR TO BE A
SHORT-LIVED REPRIEVE, AS ENSEMBLES CONTINUE TO ADVERTISE REBUILDING 500-HPA
HEIGHTS AND WARMING TEMPERATURES TO RENEW THE RISK OF EXCESSIVE HEAT THROUGHOUT
THE SOUTHWESTERN AND SOUTH-CENTRAL CONUS HEADING INTO WEEK-2.
IN THE PAST FEW DAYS, THE GEFS ENSEMBLE HAS COME INTO BETTER AGREEMENT WITH THE
ECMWF AND CANADIAN IN REGARDS TO THE DEVELOPMENT OF 500-HPA HEIGHTS EXCEEDING
594 DAM NEXT WEEKEND. THIS TREND IS REFLECTED IN THE GEFS PROBABILISTIC
EXTREMES TOOL (PET), WHICH SHOWS HIGHER CHANCES (40-50%) FOR TEMPERATURES
EXCEEDING HAZARD CRITERIA RELATIVE TO PREVIOUS GUIDANCE OVER THE LOWER FOUR
CORNERS REGION. THE ECMWF PET OFFERS A MORE EASTERLY AND MORE PERSISTENT
SOLUTION OF THE HEAT SIGNALS, DEPICTING AT LEAST A 40% CHANCE OF MAXIMUM
TEMPERATURES EXCEEDING THE 85TH PERCENTILE AND 100 DEGREES F EXTENDING INTO
CENTRAL TEXAS THROUGH THE MIDDLE OF THE PERIOD. ALTHOUGH SLIGHTLY LOWER
CHANCES ARE EVIDENT IN THE GEFS PET OVER THE SOUTHERN PLAINS, THE GROWING HEAT
SIGNALS SUPPORT THE CONTINUATION OF A MODERATE RISK OF EXCESSIVE HEAT IN
TODAY'S OUTLOOK. THE HIGHLIGHTED AREA IS EXPANDED EASTWARD AND EXTENDED THROUGH
DAY 12 (JUL 12) TO ALIGN WITH THE PEAK DURATION OF THE SUBTROPICAL RIDGING
FAVORED IN THE MID-LEVEL GUIDANCE. A BROAD SLIGHT RISK AREA OF EXCESSIVE HEAT
ALSO REMAINS POSTED FOR THE ENTIRETY OF WEEK-2 FROM THE FOUR CORNERS EASTWARD
TO THE SOUTHEAST, WHERE PETS SUGGEST HEAT POTENTIAL MAY BECOME MORE PRONOUNCED
ALONG THE GULF COAST LATER IN THE PERIOD. OVER THE SOUTHWESTERN CONUS, THE
COMBINATION OF THE INCREASING HEAT SIGNALS AND PREDICTED DRIER THAN NORMAL
PRECIPITATION IS ALSO EXPECTED TO BE CONDUCIVE FOR AN INCREASED RISK OF FIRE
WEATHER ACROSS THE PORTIONS OF THE GREAT BASIN, FOUR CORNERS AND SOUTHERN
PLAINS. WHILE LESS SUPPORTED IN THE GEFS, THE ECMWF AND CANADIAN PET SHOW AT
LEAST A 20% CHANCE FOR WIND SPEEDS EXCEEDING THE 85TH PERCENTILE, AND A BROAD
SLIGHT RISK AREA OF HIGH WINDS IS POSTED FOR JUL 8-14.
OVER THE GULF OF ALASKA AND WESTERN NORTH AMERICA, AMPLIFIED MID-LEVEL RIDGING
REMAINS FAVORED TO PROMOTE ABOVE-NORMAL TEMPERATURES OVER THE PACIFIC
NORTHWEST. THE GEFS PET HAS BECOME MORE BULLISH WITH EXCESSIVE HEAT SIGNALS,
NOW INDICATING ELEVATED CHANCES (40%) FOR TEMPERATURES EXCEEDING THE 85TH
PERCENTILE OVER PARTS OF WASHINGTON, OREGON AND IDAHO, SUPPORTIVE OF A MODERATE
RISK DESIGNATION EARLY IN THE PERIOD. HOWEVER, THE ECMWF PET TEMPERS THIS
POTENTIAL, WHICH IS MOST LIKELY TIED TO INCREASED MID-LEVEL TROUGHING OVER THE
WEST COAST WHICH IS ABSENT IN THE GEFS ON DAYS 8 AND 9. THE CANADIAN ALSO
FAVORS MORE ANOMALOUS TROUGHING EARLY IN THE PERIOD, AND GIVEN THE POTENTIAL
FOR MORE NORTHWESTERLY FLOW ACROSS THE WEST, A SLIGHT RISK OF EXCESSIVE HEAT
REMAINS ISSUED (JUL 8-10).
FOR PRECIPITATION, THE AFOREMENTIONED FRONTAL SYSTEM IS FAVORED TO TRACK OVER
THE EASTERN CONUS WHERE SCATTERED CONVECTION AND LOCALLY HEAVY RAINFALL REMAINS
POSSIBLE ALONG THE FRONTAL BOUNDARY EARLY IN THE PERIOD. MEANWHILE, A SECONDARY
AREA OF LOW PRESSURE HAS COME INTO BETTER FOCUS IN THE DAILY ENSEMBLE MEANS
UPSTREAM, WHICH MAY BRING ANOTHER ROUND OF HEAVY PRECIPITATION TO PARTS OF THE
GREAT PLAINS AND MISSISSIPPI VALLEY. THESE TWO AREAS HAVE BECOME MORE
DISCERNIBLE IN BOTH THE GEFS AND ECWMF PETS, SHOWING AT LEAST A 20% CHANCE OF
3-DAY PRECIPITATION AMOUNTS EXCEEDING AN INCH OVER THE MIDWEST AND NORTHEASTERN
CONUS AND A PAIR OF SLIGHT RISK AREAS FOR HEAVY PRECIPITATION ARE POSTED, VALID
FOR JUL 8-10 AND JUL 8-9, RESPECTIVELY.
ACROSS THE DESERT SOUTHWEST, BELOW-NORMAL PRECIPITATION REMAINS PREDOMINANTLY
FAVORED DURING WEEK-2. HOWEVER, SOME OF THE ENSEMBLES AND PETS ARE BEGINNING TO
SHOW SIGNS OF INCREASED MOISTURE AND PRECIPITATION LATE IN THE PERIOD, POSSIBLY
TIED TO GULF OF CALIFORNIA SURGE ACTIVITY. THE POTENTIAL INCREASE IN MOISTURE
IS EXPECTED TO BE BENEFICIAL FOLLOWING A SLUGGISH START TO THE NORTH AMERICA
MONSOON.
ANTECEDENT DRYNESS ALONG WITH A CONTINUED DRY PATTERN THROUGH THE NEXT WEEK AND
THE ONGOING HEAT WAVE INCREASES THE RISK FOR RAPID ONSET DROUGHT (ROD) ACROSS
PARTS OF LOUISIANA AND EASTERN TEXAS. MANY LOCATIONS IN THE HIGHLIGHTED ROD
AREA HAVE REGISTERED LESS THAN HALF OF THEIR NORMAL RAINFALL ACCUMULATION IN
THE LAST 30 DAYS. WITH THE WEEK-2 OUTLOOK FAVORING NEAR TO BELOW-NORMAL
PRECIPITATION, LOW RAINFALL AMOUNTS DURING THE NEXT WEEK, AND AN ELEVATED
EXCESSIVE HEAT RISK TO INDUCE HIGH EVAPOTRANSPIRATION RATES, A ROD RISK REMAINS
ISSUED FOR THIS REGION.
THE LONG SNOWMELT SEASON CONTINUES ACROSS THE WESTERN CONUS AFTER ACCUMULATING
A VERY LARGE AND IN SOME CASES RECORD-BREAKING SNOWPACK, INDUCING RIVER
FLOODING ESPECIALLY ACROSS HIGHER ELEVATIONS FOR SOME AREAS IN THE WEST. AS
SNOWMELT CONTINUES IN PARTS OF THE SIERRA NEVADA MOUNTAINS, FLOODING MAY
CONTINUE TO OCCUR ALONG SOME RIVERS, AND IN AREAS ADJACENT TO THE HIGHER
ELEVATIONS.
NO HAZARDS ARE POSTED FOR ALASKA AS THE COOLER AND WETTER THAN NORMAL
CONDITIONS REMAIN FAVORED PARTICULARLY FOR SOUTHERN ALASKA. THESE CONDITIONS
ARE EXPECTED TO MAINTAIN A REDUCED RISK OF WILDFIRE POTENTIAL THROUGHOUT MUCH
OF THE STATE. LESS THAN 1500 ACRES HAVE BURNED STATEWIDE SO FAR THIS YEAR WHICH
CURRENTLY REGISTERS AS THE LOWEST ACREAGE TOTAL ON RECORD FOR LATE JUNE.
FORECASTER: NICK NOVELLA
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