507
FXUS02 KWBC 071856
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
256 PM EDT FRI JUN 7 2024
VALID 12Z MON JUN 10 2024 - 12Z FRI JUN 14 2024
..HOT TEMPERATURES FOR THE WEST/SOUTHWEST PLOD INTO NEXT WEEK
..OVERVIEW
THERE IS SOME GENERAL AGREEMENT IN THE GUIDANCE THAT AN ELONGATED
UPPER LOW OVER SOUTHERN-EASTERN CANADA THIS WEEKEND WILL SPLIT BY
THE START OF THE MEDIUM RANGE PERIOD ON MONDAY, WITH A TROUGH
MOVING THROUGH THE NORTHEAST MONDAY-TUESDAY AND A COMPACT CLOSED
LOW GETTING LEFT BEHIND OVER SOUTH-CENTRAL CANADA (OR THE FAR
NORTHERN U.S.). THIS ENERGY SHOULD LINGER FOR A DAY OR TWO BEFORE
BECOMING ABSORBED BY AN ADDITIONAL SHORTWAVE FROM WESTERN CANADA.
THIS PROGRESSES EASTWARD MID-LATE WEEK WITH TROUGHING EXTENDING
SOUTHWARD THROUGH THE EAST. ADDITIONAL SOUTHERN STREAM ENERGY
EMBEDDED WITHIN WILL KEEP UNSETTLED CONDITIONS AND HEAVY RAINFALL
POTENTIAL ACROSS THE SOUTHERN ROCKIES-SOUTHERN PLAINS EARLY WEEK,
WITH AN INHERENT STRONGER THREAT SIGNAL FOR A MULTI-DAY WET PERIOD
ACROSS THE FLORIDA PENINSULA STARTING ON TUESDAY. BEHIND THIS,
UPPER RIDGING OVER THE WEST WILL SLIDE INTO THE CENTRAL U.S. WITH
CONTINUED HEAT, THOUGH LIKELY MODERATED A BIT COMPARED TO
CURRENTLY. STRONGER TROUGHING FROM AN UPPER LOW SOUTH OF THE GULF
OF ALASKA LOOKS TO ENTER THE WEST COAST LATER IN THE WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
OVERALL, GUIDANCE HAS COME INTO BETTER AGREEMENT ON THE LARGE
SCALE PATTERN PROGRESSION DURING THE MEDIUM RANGE PERIOD, BUT
CONTINUE TO STRUGGLE WITH THE DETAILS, SOME OF WHICH HAVE IMPORTANT
IMPLICATIONS ON SENSIBLE WEATHER. FOR THE CENTRAL-CANADA COMPACT
UPPER LOW, MODELS HAVE FLIP-FLOPPED THE PAST FEW DAYS BETWEEN
WHETHER THIS LINGERS OVER CANADA OR RATHER DROPS THROUGH THE UPPER
MIDWEST STATES, BUT THE LAST FEW RUNS OF GUIDANCE (INCLUDING THE
NEW 12Z GUIDANCE FOR TODAY) SEEMS TO SUPPORT THE FORMER. STILL
THOUGH, GIVEN THE SENSITIVITY OF THIS SMALL SCALE SYSTEM TO THE
STRENGTH OF A TROUGH IN THE EAST, IT REMAINS A LOW CONFIDENCE
FORECAST. ADDITIONAL SOUTHERN STREAM ENERGY THROUGH THE SOUTH-
CENTRAL PLAINS SHOWS UNCERTAINTY AND HOW THIS INTERACTS WITH THE
NORTHERN STREAM WILL AFFECT ELONGATED TROUGHING EVENTUALLY OVER THE
EAST LATER IN THE WEEK AND AVAILABILITY/EFFICIENCY OF MOISTURE
DIRECTED INTO FLORIDA AND INTERACTING WITH A STALLED FRONTAL
BOUNDARY. OTHERWISE, OUT WEST, THERE ARE STILL SOME TIMING
DIFFERENCES WITH RIDGE PROGRESSION INTO THE PLAINS RELATED TO
DIFFERENCES IN TROUGHING INTO THE NORTHWEST COAST.
WITH SUFFICIENT AGREEMENT, THE WPC FORECAST WAS ABLE TO USE A
MAJORITY BLEND OF THE DETERMINISTIC GUIDANCE FOR THE FIRST HALF OF
THE PERIOD, WITH SOME ADDITIONAL WEIGHTING GIVEN TO THE ECMWF SINCE
IT HAD A LITTLE BETTER RUN TO RUN CONTINUITY THAN OTHER MODELS.
AFTER THIS, RAMPED UP INCLUSION OF THE ENSEMBLE MEANS TO 70 PERCENT
OF THE BLEND TO HELP MITIGATE LATE PERIOD DIFFERENCES. MAINTAINED
SOME OF THE ECMWF THROUGH DAY 7 JUST FOR A LITTLE ADDED SYSTEM
DEFINITION. ON THE LARGE SCALE, THIS MAINTAINED GOOD AGREEMENT WITH
THE PREVIOUS WPC FORECAST.
..WEATHER/HAZARDS HIGHLIGHTS
AMPLE POOLED MOISTURE AND INSTABILITY WITH A WAVY FRONT THAT WILL
TEND TO STALL FROM THE CENTRAL ROCKIES TO SOUTHERN HIGH PLAINS AND
VICINITY MAY PRODUCE PERIODS WITH HEAVY CONVECTION WITH POTENTIAL
FOR HEAVY RAIN RATES, SO A MARGINAL RISK AREA IS DELINEATED FOR DAY
4/MONDAY. A WEAKENING FRONT LIFTING BACK INTO THE SOUTH-CENTRAL
PLAINS MAY CONTINUE A THREAT FOR HEAVY RAINFALL INTO DAY 5 ACROSS
VERY WATERLOGGED SOUTHEAST OKLAHOMA TO NORTHEAST TEXAS REGION.
ADDED A MARGINAL RISK ON THE DAY 5 ERO TO CAPTURE THIS. A MULTI-
DAY PERIOD FAVORABLE FOR SOME HEAVY RAINS IS THEN POSSIBLE TO
DEVELOP ACROSS THE FLORIDA PENINSULA STARTING TUESDAY AS WELL-ABOVE
MOISTURE POOLS ALONG THE STALLING FRONT WITH SOME AID FROM WEAK
UPPER LEVEL IMPULSES/ENERGY. THERE IS A LOT OF UNCERTAINTY IN THE
DETAILS AND MUCH OF THE STATE IS IN A DROUGHT. STILL, SOME THREAT
FOR HIGH RAIN RATES EXISTS, AND ITS POSSIBLE MUCH OF THE THREAT
REMAINS CONFINED TO URBANIZED AREAS. STILL, OPTED TO EXPAND THE
MARGINAL RISK ON DAY 5 TO INCLUDE MUCH OF THE CENTRAL AND SOUTHERN
PENINSULA TO ACCOUNT FOR THE UNCERTAINTY. THE BETTER MOISTURE AND
HEFTIER QPF SHOULD COME IN MID TO LATE WEEK ANYWAYS. ELSEWHERE,
MUCH OF THE COUNTRY SHOULD BE DRY EXCEPT FOR LATE WEEK SHOWERS
MOVING BACK IN TO THE ROCKIES-CENTRAL PLAINS ALONG A FRONTAL
BOUNDARY.
THE MEAN RIDGE IN THE WEST/SOUTHWEST WILL CONTINUE TO CAUSE MUCH
WARMER THAN AVERAGE TEMPERATURES, BUT SEEMINGLY NOT QUITE AS HOT AS
IN THE SHORT RANGE PERIOD. THE HIGHEST TEMPERATURE ANOMALIES OF
10-20F ABOVE NORMAL ARE FORECAST FOR THE GREAT BASIN, WARMING A BIT
AND EXPANDING EASTWARD AS THE WEEK PROGRESSES INTO THE NORTHERN
ROCKIES AND PLAINS. TEMPERATURES WILL ALSO RISE A FEW DEGREES IN
THE DESERT SOUTHWEST TO BRING SOME TEMPERATURES BACK ABOVE 110F,
WITH HEAT RISK THREAT LEVELS MOSTLY AT MODERATE TO MAJOR LEVELS.
HEAT SHOULD BUILD AGAIN ACROSS SOUTH TO SOUTHWEST TEXAS AS WELL,
WITH HEAT INDICES CREEPING BACK UP TO AROUND 110 BY THE END OF THE
WEEK.
SANTORELLI/SCHICHTEL
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 (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
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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