881
FXUS02 KWBC 062025
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
424 PM EDT THU JUL 6 2023
VALID 12Z SUN JUL 9 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
THE MODEL BLEND FOR THIS AFTERNOON'S FORECAST REMAINS CONSISTENT
WITH THE OVERNIGHT FORECAST. A BLEND OF OPERATIONAL DETERMINISTIC
MODELS WAS USED FOR THE BEGINNING OF THE PERIOD, AND ENSEMBLE
MEANS WERE INTRODUCED TO THE BLEND FOR THE SECOND HALF OF THE
PERIOD. THIS BLEND CAPTURES THE LARGE SCALE PATTERN WELL, WITH
SOME UNCERTAINTY REMAINING SURROUNDING SMALLER SCALE FEATURES.
MODEL SOLUTIONS DO NOT AGREE ON TIMING/POSITIONS OF SHORTWAVES
ROUNDING THE BASE OF THE TROUGH IN THE EAST, WHICH WILL AFFECT
SURFACE FEATURES AND SENSIBLE WEATHER. 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
18Z UPDATE: MINOR CHANGES WERE MADE TO THE DAY 4 EXCESSIVE
RAINFALL OUTLOOK. THE SLIGHT RISK AREA OVER THE SOUTH WAS EXPANDED
A BIT WEST INTO CENTRAL OKLAHOMA WHERE HEAVY RAINFALL IN THE SHORT
TERM PERIOD COULD INCREASE THE SENSITIVITY TO FLOODING. THE SLIGHT
RISK AREA IN THE SOUTH WAS ALSO EXPANDED NORTHEAST INTO CENTRAL
TENNESSEE WHERE FORECAST RAINFALL HAS INCREASED SLIGHTLY. ANOTHER
MINOR CHANGE WAS MADE TO THE SLIGHT RISK AREA IN THE NORTHEAST,
EXPANDING IT SOUTHWARDS TO INCLUDE PARTS OF SOUTHERN MD AND
NORTHERN VA. IT IS POSSIBLE THIS AREA MAY NEED TO BE PULLED EVEN
FARTHER SOUTH INTO VA IN FUTURE UPDATES, BUT CONFIDENCE WAS NOT
HIGH ENOUGH TO EXPAND IT FURTHER AT THIS TIME. FOR THE DAY 5
EXCESSIVE RAINFALL OUTLOOK, THE SLIGHT RISK AREA IN THE SOUTH WAS
SHIFTED SOUTHEAST AND EXPANDED SLIGHTLY TO ACCOUNT FOR LATEST
MODEL TRENDS IN PRECIPITATION. THE SLIGHT RISK AREA NOW INCLUDES
EASTERN LOUISIANA, SOUTHERN MISSISSIPPI, SOUTHERN ALABAMA, AND
PART OF THE FLORIDA PANHANDLE.
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, AND THIS IS REFLECTED IN THE UPDATED EROS. 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 HIGH TEMPERATURE ANOMALIES OF 10-15F
ABOVE AVERAGE 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 AVERAGE ELSEWHERE, INCLUDING 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 AROUND 5-10F BELOW AVERAGE).
A COLD FRONT DROPPING SOUTH FROM CANADA SHOULD BRING TEMPERATURES
BACK DOWN TO 5-10F BELOW AVERAGE OVER THE NORTHERN INTO CENTRAL
PLAINS BY NEXT WEDNESDAY-THURSDAY. PARTS OF THE INTERIOR
NORTHWEST/FAR NORTHERN ROCKIES COULD ALSO SEE HIGHS UP TO 10-15F
ABOVE AVERAGE SUNDAY-MONDAY, THEN A MODERATING TREND IS EXPECTED
MID-WEEK. MUCH OF THE EASTERN HALF OF THE LOWER 48 SHOULD SEE NEAR
TO SOMEWHAT BELOW AVERAGE TEMPERATURES SUNDAY-MONDAY AND MORE
NEAR-AVERAGE TEMPERATURES THEREAFTER.
DOLAN/RAUSCH
HAZARDS:
- HEAVY RAIN ACROSS PORTIONS OF ARKANSAS AND THE TENNESSEE VALLEY,
SUN, JUL 9.
- HEAVY RAIN ACROSS PORTIONS OF THE DEEP SOUTH AND THE LOWER
MISSISSIPPI VALLEY, MON-TUE, JUL 10-JUL 11.
- HEAVY RAIN ACROSS PORTIONS OF THE MID-ATLANTIC AND THE
NORTHEAST, SUN-MON, JUL 9-JUL 10.
- FLOODING POSSIBLE ACROSS PORTIONS OF THE CENTRAL PLAINS.
- FLOODING LIKELY ACROSS PORTIONS OF THE NORTHERN PLAINS.
- HAZARDOUS HEAT ACROSS PORTIONS OF THE PACIFIC NORTHWEST, SUN,
JUL 9.
- HAZARDOUS HEAT ACROSS PORTIONS OF THE SOUTHERN PLAINS, THE LOWER
MISSISSIPPI VALLEY, CALIFORNIA,
AND THE SOUTHWEST, SUN-THU, JUL 9-JUL 13.
- HEAVY RAIN ACROSS PORTIONS OF WESTERN MAINLAND ALASKA, SUN, JUL
9.
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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