520
FXUS02 KWBC 160714
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
313 AM EDT FRI JUN 16 2023
VALID 12Z MON JUN 19 2023 - 12Z FRI JUN 23 2023
...HAZARDOUS HEAT IS LIKELY ACROSS TEXAS AND LOUISIANA WITH SOME
RECORD TEMPERATURES POSSIBLE THROUGH NEXT WEEK...
..OVERVIEW
A FAIRLY STAGNANT PATTERN WILL ONCE AGAIN BE IN PLACE FOR THE
MEDIUM RANGE PERIOD NEXT WEEK, WITH AN UPPER RIDGE/HIGH NEAR THE
RIO GRANDE THAT WILL PRODUCE EXCESSIVE HEAT ACROSS THE
SOUTH-CENTRAL CONUS. THE UPPER RIDGE SHOULD EXTEND TO THE
NORTHEAST NEAR THE MIDWEST/GREAT LAKES, WHILE AN UPPER LOW LOOKS
TO BE ATOP THE SOUTHEAST/TENNESSEE VALLEY FOR A POTENTIAL REX
BLOCK PATTERN. THE UPPER LOW ALONG WITH AMPLE MOISTURE IS LIKELY
TO PRODUCE HEAVY TO EXCESSIVE RAIN ACROSS THOSE REGIONS. MEANWHILE
IN THE WEST, PERSISTENT TROUGHING WILL LEAD TO COOLER THAN NORMAL
TEMPERATURES AND SOME PRECIPITATION IN THE NORTHWEST SHIFTING INTO
THE PLAINS WITH TIME.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
THE 12/18Z MODEL CYCLE WAS IN GENERALLY GOOD AGREEMENT WITH THE
OVERALL PATTERN DESCRIBED ABOVE. A DETERMINISTIC MODEL BLEND WAS
ABLE TO BE USED EARLY IN THE PERIOD WITH THE 12Z ECMWF/UKMET/CMC
AND 18Z GFS, AS THERE WAS GOOD AGREEMENT WITH THE ANOMALOUSLY DEEP
UPPER LOW ACROSS THE NORTHWEST, THE RIDGE TO THE EAST, AND THE
DEVELOPING LOW IN THE SOUTHEAST. THE GUIDANCE DIVERGES SOMEWHAT
WITH THESE FEATURES BY MIDWEEK AND BEYOND. IN THE EAST, THE
INTERFACE OF THE RIDGE AND THE UPPER LOW SHOW SOME DIFFERENCES
THAT AFFECT THE PATH OF THE UPPER LOW BY THE LATTER PART OF NEXT
WEEK. THE 12/18Z MODEL GUIDANCE AT LEAST GENERALLY INDICATED A
DRIFT NORTH OF THE UPPER LOW WITH TIME. HOWEVER, THE NEWER 00Z
MODEL CYCLE SHOWS SOME DIVERGENCE IN THE POTENTIAL PATH OF THE
UPPER LOW. THE 00Z GFS AND ECMWF BOTH CAME IN WITH THE UPPER LOW
SPLITTING OFF FARTHER SOUTH, ALL THE WAY TO THE CENTRAL GULF COAST
THURSDAY-FRIDAY, WHILE RIDGING STILL BUILDS IN TO ITS NORTH, BUT
FARTHER SOUTH OF THE PREVIOUS MODEL CONSENSUS. MEANWHILE THE 00Z
CMC ACTUALLY HAD A FARTHER NORTH TRACK THAN ITS PREVIOUS RUN AND
BRINGS THE UPPER LOW INTO THE OHIO VALLEY THURSDAY-FRIDAY, TOTALLY
OUT OF PHASE WITH THE 00Z GFS/ECMWF. THE BLEND OF 12/18Z MODELS
AND ENSEMBLES THAT THE WPC FORECAST USED IS AT LEAST SORT OF IN
BETWEEN THESE TYPES OF SOLUTIONS WITH THE LOW'S AND HIGH'S PATH,
SO THIS MAY BE A REASONABLE PLACE TO BE FOR NOW, BUT THIS
INDICATES THE CONTINUED UNCERTAINTY WITH THE PATTERN.
AT LEAST MODEL GUIDANCE FROM MULTIPLE CYCLES AGREES THAT UPPER
RIDGING WILL BE IN PLACE ACROSS THE SOUTH-CENTRAL U.S. THROUGH THE
PERIOD. THE WESTERN LOW/TROUGH BEGINS WITH GOOD AGREEMENT BUT GFS
RUNS SEEMED TO BE OUTLIERS IN THE EVOLUTION BY LATER NEXT WEEK,
BRINGING RIDGING INTO THE CENTRAL GREAT BASIN OR SO AS SOME OF THE
ENERGY FROM THE TROUGHING SPLIT INTO THE PACIFIC. THE 00Z GFS AND
GEFS MEAN DO NOT SHOW THIS PATTERN ANYMORE. A NON-NCEP BLEND OF
THE 12/18Z MODELS SEEMED TO WORK WELL ACROSS THE WEST.
..WEATHER/HAZARDS HIGHLIGHTS
THE UPPER LOW MEANDERING OVER THE TENNESSEE VALLEY OR SO, ALONG
WITH A FRONTAL SYSTEM AND AMPLE GULF MOISTURE, WILL PROVIDE
SUPPORT FOR MULTIPLE ROUNDS OF RAIN AND THUNDERSTORMS FOR THE
SOUTHEASTERN QUADRANT OF THE COUNTRY THROUGH MUCH OF NEXT WEEK.
SLIGHT RISKS OF EXCESSIVE RAINFALL ARE IN PLACE FOR BOTH MONDAY
AND TUESDAY IN THE SOUTHEAST TO SOUTHERN APPALACHIANS (WITH A
SLIGHT SHIFT EASTWARD TUESDAY) GIVEN THE POTENTIAL FOR WIDESPREAD
1-3" TOTALS PER DAY WITH LOCALLY HIGHER AMOUNTS. PORTIONS OF THIS
REGION HAVE OR WILL LIKELY HAVE BY THAT TIME WET ANTECEDENT
CONDITIONS GIVEN RECENT OR UPCOMING EPISODES OF HEAVY RAINFALL. IN
FACT THE SLIGHT RISK EROS WERE EXPANDED INTO THE FLORIDA PANHANDLE
WITH ONE REASON BEING THE EXTREME RAINFALL AMOUNTS UNFOLDING
CURRENTLY OVERNIGHT ACROSS PENSACOLA AND THE VICINITY. AS NEXT
WEEK PROGRESSES, THE TRACK OF THE UPPER LOW WILL AFFECT WHERE
RAINFALL SPREADS. THIS FORECAST CYCLE ENDED UP WITH LESS QPF FOR
THE MID-ATLANTIC REGION COMPARED TO THE PREVIOUS FORECAST GIVEN
MODEL TRENDS, MAINTAINING THE HIGHER QPF FARTHER SOUTH ACROSS THE
CAROLINAS AND SOUTH THROUGH THE LATTER PART OF NEXT WEEK, BUT THIS
IS STILL AN UNCERTAIN ASPECT OF THE FORECAST. MEANWHILE
TEMPERATURES ACROSS THE REGION ARE LIKELY TO BE BELOW AVERAGE WITH
THE CLOSED LOW OVERHEAD, INFLUENCE OF CLOUDS/PRECIPITATION, AND
COLD-AIR DAMMING SETTING UP ALONG THE APPALACHIANS.
AS ANOTHER UPPER LOW COMES INTO THE NORTHWEST AND PIVOTS NEXT
WEEK, PRECIPITATION CHANCES WILL INCREASE THERE NEAR AND BEHIND A
FRONTAL SYSTEM MONDAY-TUESDAY. GIVEN THE BELOW NORMAL HEIGHTS AND
THUS TEMPERATURES, THE HIGHEST ELEVATIONS COULD SEE SOME SNOW.
FARTHER EAST INTO THE NORTHERN ROCKIES/HIGH PLAINS, THERE MAY BE
SOME INSTABILITY TO WORK WITH AND PRODUCE STORMS, LEADING TO SOME
POSSIBLY LOCALLY HEAVY RAIN OVER AREAS THAT COULD BE SENSITIVE DUE
TO WELL ABOVE NORMAL RAINFALL OVER THE PAST FEW WEEKS. INTO
TUESDAY AND BEYOND, RAIN AND THUNDERSTORM CHANCES SHOULD BE
INCREASINGLY COMMON THE PLAINS AS THE LOW PRESSURE/FRONTAL SYSTEM
STALLS AND FOCUSES MOISTURE. THE TROUGHING IN THE WEST WILL ALSO
LEAD TO WELL BELOW NORMAL TEMPERATURES PARTICULARLY FOR HIGHS.
HIGH TEMPERATURES OF 15-25F BELOW AVERAGE IN THE GREAT BASIN COULD
CHALLENGE DAILY RECORDS FOR COOL HIGHS ON MONDAY AND TUESDAY, WITH
LOWS AROUND 10F BELOW NORMAL. TEMPERATURES LOOK TO GRADUALLY
MODERATE CLOSER TO, BUT STILL REMAINING BELOW, NORMAL FOR THE
LATTER HALF OF THE WEEK ACROSS THE WEST.
THE EXCESSIVE HEAT WILL CONTINUE INTO NEXT WEEK ACROSS MUCH OF
TEXAS AND INTO PORTIONS OF LOUISIANA AND NEW MEXICO, WITH
WIDESPREAD 100S AND EVEN SOME 110S ACROSS CENTRAL AND SOUTHERN
PORTIONS OF TEXAS, AND 90S COVERING MUCH OF THE LOWER MISSISSIPPI
VALLEY AND THE CENTRAL PLAINS. MANY DAILY RECORD HIGH TEMPERATURES
ARE POSSIBLE, AND SOME MONTHLY RECORDS MAY EVEN BE CHALLENGED.
HEAT INDICES AS HIGH AS 115-120 DEGREES ARE POSSIBLE FOR PARTS OF
SOUTHERN AND SOUTHEASTERN TEXAS WHERE THE GREATEST COMBINATION OF
HIGH DEWPOINTS AND TEMPERATURES WILL LIKELY EXIST. AS MEAN RIDGING
EXPANDS FURTHER NORTH, ADDITIONAL MUCH ABOVE AVERAGE TEMPERATURES
ARE FORECAST FOR PORTIONS OF THE NORTHERN PLAINS, PARTICULARLY ON
MONDAY-TUESDAY, WITH HIGHS REACHING INTO THE MID- TO UPPER 90S.
THEN THE UPPER MIDWEST CAN EXPECT 80S TO LOW 90S FOR HIGHS FOR THE
LATTER HALF OF THE WEEK, ABOUT 10F ABOVE AVERAGE.
TATE
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, EXPERIMENTAL EXCESSIVE RAINFALL
OUTLOOK, WINTER WEATHER OUTLOOK PROBABILITIES AND HEAT INDICES 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
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page