900
FXUS02 KWBC 091939
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
338 PM EDT WED AUG 09 2023
VALID 12Z SAT AUG 12 2023 - 12Z WED AUG 16 2023
...HEAT WAVE TO PREVAIL ACROSS THE SOUTH INTO THE SOUTHWEST
THROUGH AT LEAST THE MIDDLE OF NEXT WEEK...
..HAZARDOUS HEAT POSSIBLE OVER THE PACIFIC NORTHWEST NEXT WEEK
..OVERVIEW
THE HEATWAVE ACROSS THE SOUTHERN TIER WILL ENDURE THROUGH AT LEAST
NEXT WEEK AS RIDGING BUILDS WESTWARD. THIS EXPANSION WILL DISPLACE
AN UPPER LEVEL LOW ANTICIPATED OFFSHORE THE COAST OF CALIFORNIA
THROUGH THE WEEKEND. THE POTENTIAL REMAINS FOR THE FOR THE
NORTHWESTERN PART OF THIS RIDGE TO CONNECT WITH A SEPARATE RIDGE
BUILDING OVER THE NORTHEASTERN PACIFIC. THIS HEAT WILL LEAD TO
DAILY HIGH TEMPERATURE RECORDS, PARTICULARLY FOR TEXAS AND PARTS
OF THE CENTRAL GULF COAST. A SERIES OF EMBEDDED SHORTWAVES WITHIN
A BROAD CYCLONIC FLOW WILL WILL TRACK EAST OF THE ROCKIES ACROSS
THE NORTHERN TIER. MULTIPLE FRONTAL SYSTEMS WILL USHER LOCALLY
STRONG/HEAVY CONVECTION WITH THEM AS THEY PROGRESS EASTWARD. THESE
FEATURES HAVE VARYING DEGREES OF PREDICTABILITY, WITH GREATER
CONFIDENCE IN THE GENERAL PATTERN OF PROGRESSIVE SURFACE
WAVES/FRONTS THAN SOME OF THE FINER BUT IMPORTANT DETAILS.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
THE LATEST RUNS OF THE MODEL AND ENSEMBLE GUIDANCE CONTINUE TO
HAVE A DECENT HANDLE ON THE LARGE SCALE PATTERN BY KEEPING RIDGING
ACROSS THE SOUTH WHILE THE NORTHERN FLOW IS PROGRESSIVE WITH A
SERIES OF SURFACE LOWS/FRONTAL SYSTEMS. TYPICAL MODEL DIFFERENCES
PERSIST GIVEN THE SCALE OF THE SHORTWAVES, BUT ARE WITHIN REASON.
THE GFS ONCE AGAIN DEPICTED DISPLACED QPF FROM THE CLUSTER WITH
THE INITIAL SYSTEM OVER THE NORTHEAST AND CONTINUED TO BE AN
OUTLIER WITH THE NEXT ROUND MOVING ACROSS THE UPPER
MIDWEST/MIDWEST/GREAT LAKES REGION. THE ECWMF, CMC AND UKMET WHERE
BEST CLUSTERED AND MAINTAINED FEATURES THROUGH THE WEEK,
ESPECIALLY WITH ANOTHER SYSTEM THAT IS DEPICTED FOR THE NORTHEAST;
WHEREAS, THE GFS SUGGESTED A WEAK COASTAL WAVE. THE GEFS MEAN WAS
NOT AS REFLECTIVE AS ITS PARENT THE GFS AND LEANED TOWARD THE
ECWMF/CMC/UKMET ALTHOUGH A BIT MUTED.
FOLLOWED A SIMILAR FORECAST APPROACH FOR THIS ISSUANCE BY
UTILIZING 00Z ECWMF/CMC/UKMET WITH A SOME INCLUSION OF THE GEFS
MEAN THROUGH DAY 5 OF THE EXTENDED PERIOD. FOR THE LATTER PORTION
OF THE EXTENDED PERIOD THE UKMET WAS DROPPED AND REPLACED WITH THE
EC AND CMC ENSEMBLE MEANS. THIS APPROACH HELPED MAINTAIN FORECAST
CONTINUITY.
..WEATHER/HAZARDS HIGHLIGHTS
DURING THE SATURDAY-SUNDAY NIGHT PERIOD COVERED BY THE DAYS 4-5
EXCESSIVE RAINFALL OUTLOOKS, BOTH DAYS SHOULD SEE SOME POTENTIAL
FOR LOCALLY HEAVY CONVECTION OVER PARTS OF THE SOUTHERN
ROCKIES/SOUTH-CENTRAL HIGH PLAINS WITH SOME SHORTWAVE
ENERGY/MOISTURE LIFTING NORTHWARD BETWEEN THE UPPER LOW OVER THE
CALIFORNIA COAST AND RIDGE TO THE EAST, WHILE A COUPLE FRONTS MAY
DROP INTO THE CENTRAL HIGH PLAINS TO PROVIDE ADDED FOCUS. A
MARGINAL RISK AREA ACCOUNTS FOR THIS POTENTIAL. AREAS FROM THE
SOUTHEAST INTO PARTS OF THE MISSISSIPPI/TENNESSEE VALLEY AND
NORTHEASTWARD INTO THE AND NEAR THE EASTERN GREAT LAKES ARE ALSO
IN A MARGINAL RISK AREA FOR DAY 4, WITH A COUPLE FRONTAL SYSTEMS
INTERACTING WITH ABOVE NORMAL MOISTURE AND INSTABILITY. ONE OR
MORE EMBEDDED SLIGHT RISK AREAS COULD EVENTUALLY ARISE IF SHORTER
TERM GUIDANCE EVENTUALLY STARTS TO REFINE WHERE MORE PRONOUNCED
FOCUS MAY EXIST. THERE IS ALSO A DIFFUSE SIGNAL FOR LOCALLY HEAVY
CONVECTION OVER PARTS OF THE NORTH-CENTRAL PLAINS/MIDWEST ON DAY 4
BUT CLUSTERING DOES NOT APPEAR SUFFICIENT TO WARRANT A RISK AREA
AT THIS TIME. ON DAY 5, LEANING TOWARD THE MAJORITY ECMWF CLUSTER
FOR UPPER LEVEL AND SURFACE EVOLUTION OVER THE MIDWEST WOULD
SUPPORT A FAIRLY BROAD AREA OF LOCALLY HEAVY CONVECTIVE POTENTIAL
THAT COULD LINK BACK TO THE SOUTH-CENTRAL HIGH PLAINS. THUS PLAN
TO DEPICT A MARGINAL RISK AREA OVER THE MIDWEST AND CONNECTING
WITH THE AFOREMENTIONED SOUTHERN ROCKIES/HIGH PLAINS AREA.
FLORIDA MAY SEE SOME INCREASED RAINFALL DURING DAYS 4-5 AS
MOISTURE ANOMALIES INCREASE BUT COMPARED TO A COUPLE DAYS AGO THE
GUIDANCE HAS BECOME MORE DIVERSE REGARDING THE TIMING AND
MAGNITUDE OF MOISTURE ANOMALIES, SO WILL NOT DEPICT A RISK AREA
THERE AT THIS TIME.
MOISTURE AND SHORTWAVE ENERGY SHOULD PRODUCE SOME DIURNALLY
ENHANCED SHOWERS AND THUNDERSTORMS OVER OTHER PORTIONS OF THE WEST
DURING THE PERIOD, WITH CONFIDENCE TEMPERED BY GUIDANCE
DIFFERENCES IN SPECIFICS OF LOCATION/STRENGTH OF THE UPPER LEVEL
ENERGY AND MOISTURE DETAILS. MEANWHILE THE SYSTEM WHICH THE
GUIDANCE MAJORITY DEPICTS OVER THE GREAT LAKES BY MONDAY COULD
PRODUCE ANOTHER EPISODE OF CONVECTION THAT COULD BE STRONG/HEAVY
OVER SOME AREAS OF THE EASTERN U.S. CONTINUE TO MONITOR FORECASTS
AS GUIDANCE EVENTUALLY COMES INTO BETTER AGREEMENT ON SYSTEM
DETAILS. YET ANOTHER COLD SHOULD DROP INTO THE NORTHERN PLAINS BY
TUESDAY-WEDNESDAY, WITH SOME ASSOCIATED RAINFALL POSSIBLE.
THE HEAT ACROSS THE SOUTHERN TIER WILL LIKELY CONTINUE THROUGH AT
LEAST THE MIDDLE OF NEXT WEEK WITH THE GREATEST EMPHASIS OVER THE
SOUTHERN PLAINS THROUGH CENTRAL GULF COAST REGION WHERE HIGHS WILL
LIKELY BE 5-10F OR SO ABOVE NORMAL NEARLY EVERY DAY. SOME
LOCATIONS IN FLORIDA SHOULD SEE HIGHS SEVERAL DEGREES ABOVE NORMAL
AS WELL, WHILE WESTWARD EXPANSION OF THE UPPER RIDGE AS CURRENTLY
FORECAST WOULD ALSO RAISE TEMPERATURES IN THE SOUTHWEST UP TO
5-10F ABOVE NORMAL BY NEXT MONDAY-WEDNESDAY (LEADING TO SOME HIGHS
EXCEEDING 110F). DAILY RECORD HIGHS WILL BE MOST LIKELY OVER THE
SOUTHERN PLAINS, CENTRAL GULF COAST, AND FLORIDA. HIGH HUMIDITY
SHOULD LEAD TO MAXIMUM HEAT INDICES AT LEAST IN THE 110-115F RANGE
ALONG AND NEAR THE WESTERN-CENTRAL GULF COAST, OVER THE LOWER
MISSISSIPPI VALLEY, AND PERHAPS WITH SLIGHTLY LESS COVERAGE
FARTHER EAST. RECORD WARM LOWS WILL BE POSSIBLE ACROSS A BROAD
PORTION OF THE SOUTHERN TIER EACH NIGHT. MEANWHILE STRENGTHENING
UPPER RIDGING SHOULD BRING HIGHER TEMPERATURES TO THE PACIFIC
NORTHWEST DURING THE WEEKEND AND EARLY NEXT WEEK, WITH HIGHS
REACHING 10F OR MORE ABOVE NORMAL OVER SOME LOCATIONS FROM SUNDAY
ONWARD. VERY WARM TO HOT TEMPERATURES MAY EXTEND BEYOND THE
MEDIUM RANGE FORECAST PERIOD. RECORD WARM LOWS WILL BE POSSIBLE
BY EARLY-MID WEEK BUT FORECAST HIGHS ARE NOT YET REACHING DAILY
RECORD VALUES. AREAS FROM THE NORTHERN ROCKIES THROUGH
NORTHERN-CENTRAL PARTS OF THE EAST WILL SEE VARIABLE TEMPERATURES
UP TO 5-10F ON EITHER SIDE OF NORMAL, CORRESPONDING TO
SYSTEM/FRONTAL PROGRESSION. THE UPPER TROUGH/LOW NEAR CALIFORNIA
SHOULD KEEP HIGHS OVER THE SOUTHWEST SLIGHTLY BELOW NORMAL INTO
THE WEEKEND, FOLLOWED BY A WARMER TREND AS THE FEATURE DRIFTS
WESTWARD.
CAMPBELL/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
HAZARDS:
- SEVERE WEATHER ACROSS PORTIONS OF THE CENTRAL PLAINS, THE MIDDLE
MISSISSIPPI VALLEY, THE UPPER MISSISSIPPI VALLEY, AND THE NORTHERN
PLAINS, SUN, AUG 13.
- HAZARDOUS HEAT ACROSS PORTIONS OF CALIFORNIA, THE PACIFIC
NORTHWEST, AND THE NORTHERN GREAT BASIN, SUN-WED, AUG 13-AUG 16.
- HAZARDOUS HEAT ACROSS PORTIONS OF CALIFORNIA AND THE SOUTHWEST,
MON-WED, AUG 14-AUG 16.
- HAZARDOUS HEAT ACROSS PORTIONS OF THE SOUTHEAST, THE LOWER
MISSISSIPPI VALLEY, AND THE SOUTHERN PLAINS, SAT-WED, AUG 12-AUG
16.
- HAZARDOUS HEAT ACROSS PORTIONS OF THE LOWER MISSISSIPPI VALLEY,
THE TENNESSEE VALLEY, THE MID-ATLANTIC, THE SOUTHERN APPALACHIANS,
THE SOUTHEAST,AND THE SOUTHERN PLAINS, SAT-MON, AUG 12-AUG 14.
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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