604
FXUS02 KWBC 060701
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 AM EDT THU JUL 06 2023
VALID 12Z SUN JUL 09 2023 - 12Z THU JUL 13 2023
...HEAT EXPECTED TO REBUILD FROM THE SOUTHWEST TO THE CENTRAL GULF
COAST THIS WEEKEND INTO NEXT WEEK...
...HEAVY RAIN/RUNOFF CONCERNS LIKELY TO FOCUS OVER PORTIONS OF THE
SOUTH-CENTRAL MISSISSIPPI/TENNESSEE VALLEY REGION AND
MID-ATLANTIC/NORTHEAST SUNDAY INTO MONDAY...
..OVERVIEW
MOST GUIDANCE SHOWS THE LARGE SCALE FLOW SETTLING INTO A FAIRLY
PERSISTENT PATTERN FROM LATE WEEKEND THROUGH NEXT WEEK. THIS
CONFIGURATION WILL CONSIST OF AN EASTERN U.S. MEAN TROUGH ANCHORED
BY A DEEP UPPER LOW TRACKING FROM THE WESTERN SHORE OF HUDSON BAY
INTO NORTHERN ONTARIO, A STRENGTHENING ROCKIES/HIGH PLAINS UPPER
HIGH THAT SHOULD DRIFT A BIT WESTWARD TO AROUND THE ARIZONA/NEW
MEXICO BORDER ALONG WITH A RIDGE EXTENDING TO ITS NORTH-NORTHWEST,
AND MEAN TROUGHING OFFSHORE THE PACIFIC NORTHWEST. SHORTWAVES
WITHIN THE UPPER TROUGH EAST OF THE ROCKIES AND ASSOCIATED
WAVES/FRONTS WILL LIKELY PROVIDE A FOCUS FOR MULTIPLE EPISODES OF
SHOWERS AND THUNDERSTORMS WITH AREAS OF HEAVY RAINFALL POSSIBLE.
MEANWHILE THE UPPER RIDGE WILL SUPPORT AN EXPANDING AREA OF
HAZARDOUS HEAT BETWEEN THE SOUTHWEST U.S. AND CENTRAL GULF COAST
REGION, LIKELY PERSISTING INTO THE WEEK TWO TIME FRAME PER CLIMATE
PREDICTION CENTER FORECASTS.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
A 12Z/18Z OPERATIONAL MODEL COMPOSITE EARLY IN THE PERIOD FOLLOWED
BY PHASING IN UP TO 30-40 PERCENT TOTAL 18Z GEFS/12Z ECMWF MEAN
INPUT BY DAYS 6-7 WEDNESDAY-THURSDAY CONTINUES TO REPRESENT THE
CONSENSUS IDEAS OF THE LARGE SCALE PATTERN EVOLUTION WHILE
REDUCING THE INFLUENCE OF SMALLER SCALE DETAILS THAT HAVE LOWER
PREDICTABILITY AND CONFIDENCE. THE MODELS HAVE STILL NOT COME INTO
AGREEMENT REGARDING REGIONALLY IMPORTANT SHORTWAVE SPECIFICS
WITHIN THE OVERALL EASTERN U.S. UPPER TROUGH SUNDAY-TUESDAY,
LEADING TO SOME ONGOING SPREAD AND RUN-TO-RUN VARIABILITY FOR
SURFACE WAVE/FRONT AND QPF DETAILS FROM THE MISSISSIPPI VALLEY TO
THE EAST COAST. RELATIVE DISCREPANCIES OF THE CMC AND UKMET (MORE
AND LESS AMPLIFIED VERSUS CONSENSUS, RESPECTIVELY) CANCEL OUT
AMONG THE MINORITY COMPONENTS OF THEIR SOLUTIONS OVER THE EAST. AT
LEAST THEIR QPF PATTERNS OVER THE NORTHEAST EARLY IN THE PERIOD
HAVE TRENDED CLOSER TO THE GFS-GEFS/ECMWF-ECENS THAT HAVE HELD UP
WELL OVER THE PAST 24 HOURS ASIDE FROM A LITTLE EAST-WEST
VARIABILITY. FARTHER WEST THERE IS DECENT CLUSTERING FOR THE
NORTHERN ONTARIO UPPER LOW, WITH TYPICAL SPREAD IN TRACK FOR
FORECASTS SEVERAL DAYS OUT IN TIME. SPECIFICS OF POSITION/EMBEDDED
WAVES FOR THE LEADING COLD FRONT THAT DROPS INTO THE NORTHERN TIER
BY MONDAY AND CONTINUES SOUTH/EAST THEREAFTER WILL DEPEND ON LOWER
PREDICTABILITY SHORTWAVE DETAILS SO EXPECT SOME CONTINUED
VARIABILITY WITH THAT ASPECT OF THE FORECAST. THE MEAN TROUGH OFF
THE PACIFIC NORTHWEST COAST SHOULD CONTAIN MULTIPLE EMBEDDED
FEATURES, WITH THE AXIS OF THE OVERALL TROUGH LIKELY BECOMING
ALIGNED SOMEWHAT FARTHER WEST LATE IN THE PERIOD IN RESPONSE TO AN
UPPER RIDGE THAT AMPLIFIES NEAR 160W LONGITUDE.
..WEATHER/HAZARDS HIGHLIGHTS
DURING THE DAYS 4-5 PERIOD COVERING SUNDAY THROUGH MONDAY NIGHT,
THERE WILL BE TWO AREAS OF GREATEST FOCUS FOR HEAVY RAINFALL
POTENTIAL. ONE SHOULD EXTEND FROM AROUND OKLAHOMA EASTWARD INTO
THE TENNESSEE VALLEY AND SOUTHEAST TOWARD THE EAST-CENTRAL GULF
COAST, WHICH WILL LIKELY BE THE CONTINUATION OF A MULTI-DAY PERIOD
OF CONVECTION STARTING OUT OVER THE CENTRAL PLAINS IN THE SHORTER
TERM. GUIDANCE HAS ON AVERAGE SHIFTED SOUTHWARD WITH THIS AREA OF
RAINFALL, SO THE DAY 4 EXCESSIVE RAINFALL OUTLOOK HAS MADE SOME
CORRESPONDING ADJUSTMENTS FOR THE SLIGHT RISK AREA COMPARED TO THE
PREVIOUS DAY 5 OUTLOOK. BY DAY 5 THERE ARE SIGNALS FOR A POSSIBLE
BAND OF CONVECTION EXTENDING BACK NORTHWEST INTO THE CENTRAL
PLAINS WITHIN AN AXIS OF FAVORABLE MOISTURE AND INSTABILITY, TO
THE NORTH OF A FRONT THAT BEGINS LIFTING NORTH AS A WARM FRONT.
HOWEVER GUIDANCE IS SUFFICIENTLY DIVERGENT TO RECOMMEND ONLY A
MARGINAL RISK OVER THAT AREA FOR NOW. THE OTHER SIGNIFICANT REGION
OF FOCUS WILL BE THE NORTHERN MID-ATLANTIC INTO THE NORTHEAST ON
DAY 4, WITH GOOD CONTINUITY FOR THE SLIGHT RISK AREA FROM RECENT
OUTLOOKS. MOST GUIDANCE SUGGESTS ANOMALOUS MOISTURE WILL PERSIST
OVER THE NORTHEAST INTO DAY 5 BUT THE FULL RANGE OF GUIDANCE
PROVIDES MIXED MESSAGES FOR RAINFALL SPECIFICS, FAVORING A
MARGINAL RISK AS A STARTING POINT. CONTINUE TO EXPECT SOME BANDS
OF RAINFALL ACROSS THE FAR NORTHERN TIER WITH AN INITIAL WEAKENING
FRONT AND A STRONGER FRONT PUSHING SOUTH FROM CANADA. SOME
EAST-WEST TRAINING OF THIS ACTIVITY COULD BE POSSIBLE BUT
RELATIVELY MODEST MOISTURE ANOMALIES AND MODERATELY DRY ANTECEDENT
CONDITIONS STILL FAVOR NO RISK AREA FOR NOW. BY TUESDAY-THURSDAY
THE EAST SHOULD SEE AT LEAST A BRIEF DRIER TREND WHILE MORE
SHOWERS/THUNDERSTORMS DEVELOP OVER PARTS OF THE CENTRAL U.S. INTO
THE MISSISSIPPI VALLEY/GREAT LAKES AS THE FRONT REACHING THE
NORTHERN TIER EARLY IN THE WEEK CONTINUES PUSHING SOUTH AND EAST.
SOME OF THIS RAINFALL COULD BE LOCALLY HEAVY, WITH LOCATION AND
MAGNITUDE DETAILS GRADUALLY BECOMING BETTER DEFINED OVER THE
COMING DAYS. MOST OF THE WEST SHOULD REMAIN DRY THROUGH THE
PERIOD.
STRENGTHENING OF THE INITIAL SOUTHERN ROCKIES/HIGH PLAINS RIDGE
AND A SLIGHT WESTWARD DRIFT WITH TIME WILL LIKELY EXPAND COVERAGE
OF HAZARDOUS HEAT ACROSS THE SOUTHERN TIER DURING THE FORECAST
PERIOD. EXPECT THE GREATEST TEMPERATURE ANOMALIES OF PLUS 10-15F
FOR HIGHS TO BE NEAR THE UPPER HIGH CENTER (WESTERN TEXAS AND
PARTS OF NEW MEXICO) WITH A BROADENING AREA OF HIGHS AT LEAST A
FEW DEGREES ABOVE NORMAL ELSEWHERE, INCLUDING INTO THE SOUTHWEST
BY THE START OF NEXT WEEK. LIKEWISE, EXPECT MORE COVERAGE OF
MAXIMUM HEAT INDEX VALUES REACHING 110F OR GREATER OVER
SOUTHERN/EASTERN TEXAS INTO THE LOWER MISSISSIPPI VALLEY, WHILE
LOWER HUMIDITY WILL LEAD TO MAXIMUM HEAT INDEX VALUES OVER THE
SOUTHWEST NEAR OR SLIGHTLY BELOW THE EXPECTED AIR TEMPERATURES
REACHING UP TO 110-115F OR SO FROM LATE WEEKEND ONWARD. LOW
TEMPERATURES IN THE UPPER 70S TO LOW 80S WILL NOT PROVIDE MUCH
RELIEF OVERNIGHT AND COULD EXACERBATE HEAT STRESS AS WELL AS YIELD
SOME DAILY RECORDS FOR WARM MINIMUM TEMPERATURES. THERE MAY BE A
FEW DAILY RECORDS FOR HIGH TEMPERATURES AS WELL. CLIMATE
PREDICTION CENTER FORECASTS INDICATE THIS HEAT SHOULD EXTEND
BEYOND NEXT THURSDAY. THE CENTRAL PLAINS SHOULD SEE TEMPERATURES
REBOUND TO NEAR NORMAL FOR A COUPLE DAYS OR SO AFTER A COOL SUNDAY
(HIGHS UP TO 5-10F OR SO BELOW NORMAL). A COLD FRONT DROPPING
SOUTH FROM CANADA SHOULD BRING TEMPERATURES BACK DOWN TO 5-10F
BELOW NORMAL OVER THE NORTHERN INTO CENTRAL PLAINS BY NEXT
WEDNESDAY-THURSDAY. PARTS OF THE INTERIOR NORTHWEST/FAR NORTHERN
ROCKIES SHOULD SEE HIGHS UP TO 10-15F ABOVE NORMAL SUNDAY-MONDAY
AND THEN A MODERATING TREND. MUCH OF THE EASTERN HALF OF THE LOWER
48 SHOULD SEE NEAR TO SOMEWHAT BELOW NORMAL READINGS SUNDAY-MONDAY
AND MORE NEAR-NORMAL READINGS THEREAFTER.
RAUSCH
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC
MEDIUM RANGE HAZARDS OUTLOOK CHART AT:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,
QUANTITATIVE PRECIPITATION FORECAST, EXCESSIVE RAINFALL OUTLOOK,
WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY
MESSAGES ARE AT:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=ERO
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
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