539
FXUS02 KWBC 100701
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 AM EDT MON JUL 10 2023
VALID 12Z THU JUL 13 2023 - 12Z MON JUL 17 2023
...HAZARDOUS TO EXTREME HEAT WILL BUILD ACROSS MUCH OF THE
SOUTHERN U.S. AND INTO THE WEST COAST STATES THROUGH THIS WEEK AND
BEYOND...
...HEAVY RAIN CONCERNS LIKELY TO FOCUS OVER PARTS OF THE MIDWEST
AND MID-MISSISSIPPI VALLEY...
..OVERVIEW
THE UPPER LEVEL PATTERN OVER THE CONUS LATE THIS WEEK AND INTO THE
WEEKEND MAY TREND MORE AMPLIFIED WITH TIME AS TROUGHING IS
MAINTAINED ACROSS THE EASTERN U.S. AND AND UPPER LEVEL RIDGING
BUILDS INTO THE WEST. THE EASTERN TROUGH WILL BE ANCHORED BY A
DEEP UPPER LOW NEAR HUDSON BAY WITH MULTIPLE WAVES OF ENERGY
ROTATING THROUGH THE BASE DRIVING ROUNDS OF SHOWERS AND STORMS
ACROSS THE MIDWEST AND INTO THE NORTHEAST. HAZARDOUS TO EXTREME
HEAT WILL BE ONGOING AS THE PERIOD BEGINS THURSDAY ACROSS MUCH OF
THE SOUTHERN TIER OF THE U.S. AND BACK INTO THE SOUTHWEST AND
CALIFORNIA THROUGH THE WEEKEND AND WELL INTO NEXT WEEK, AS PER THE
LATEST INFORMATION FROM THE CLIMATE PREDICTION CENTER. THERE IS
INCREASING CONFIDENCE THIS COULD BE A LONG DURATION AND POSSIBLY
INTENSE HEAT WAVE FOR PORTIONS OF THE WEST AND SOUTHERN U.S..
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
THE LATEST GUIDANCE CONTINUES TO CAPTURE THE OVERALL SYNOPTIC
EVOLUTION REASONABLY WELL, WITH PLENTY OF UNCERTAINTIES IN THE
DETAILS, ESPECIALLY SMALLER SCALE SHORTWAVES AROUND THE SOUTHERN
PERIPHERY OF THE HUDSON BAY LOW WHICH HAS SOME SIGNIFICANT
IMPLICATIONS FOR FRONTAL STRUCTURE AND SENSIBLE WEATHER INCLUDING
POTENTIAL FLASH FLOOD RISK AREAS ACROSS PARTS THE MID-MISSISSIPPI
VALLEY AND MIDWEST. THERE'S SOME DISAGREEMENT TOO WITH PLACEMENT
AND EVENTUAL EVOLUTION OF THE UPPER LOW. 12Z (JUL 9) ECMWF IS
DISPLACED WELL WEST OF THE BETTER CONSENSUS AND BY DAY 7/MONDAY,
TRIES TO SPLIT THE CORE ENERGY WHILE THE GFS/CMC AND ENSEMBLE
MEANS SUPPORT ONE MAIN FEATURE SLIDING EAST. THE NEW 00Z RUN FOR
TODAY (WHICH CAME IN AFTER THE WPC FORECAST) SEEMS MUCH MORE
REASONABLE AND IN LINE WITH CURRENT GUIDANCE. THE WPC FORECAST FOR
TONIGHT USED A BLEND OF THE DETERMINISTIC GUIDANCE THROUGH DAY 5,
WITH INCREASING CONTRIBUTIONS FROM THE ENSEMBLE MEANS ON DAYS 6
AND 7 TO MITIGATE THE SMALLER SCALE DIFFERENCES AND UNCERTAINTIES.
..WEATHER/HAZARDS HIGHLIGHTS
A FRONTAL BOUNDARY SETTLING FROM THE CENTRAL PLAINS INTO THE
MIDWEST/OHIO VALLEY SHOULD PROVIDE THE BEST FOCUS FOR DAILY ROUNDS
OF SHOWERS AND STORMS THURSDAY AND FRIDAY. GIVEN AVAILABLE
MOISTURE AND INSTABILITY, HEAVY RAINFALL SEEMS A GOOD BET FOR
PORTIONS OF THE MID-MISSISSIPPI VALLEY INTO THE MIDWEST, BUT EXACT
LOCATION REMAINS RATHER UNCERTAIN STILL. THE BEST OVERLAP IN THE
CURRENT AVAILABLE GUIDANCE POINTS TO THE SOUTHERN MISSOURI TO
KENTUCKY REGION, WHERE A SLIGHT RISK WAS PLACED ON BOTH THE DAYS 4
AND 5 EXCESSIVE RAINFALL OUTLOOKS. IT'S LIKELY THOUGH THIS WILL
SHIFT AND NEED TO BE ADJUSTED IN FUTURE UPDATES. THE NORTHERN
PORTION OF THIS FRONT WILL MOVE INTO THE NORTHEAST WITH ROUNDS OF
ADDITIONAL RAINFALL, AND GIVEN HOW SUSCEPTIBLE THIS REGION IS, A
SLIGHT RISK WAS ADDED TO THE DAY 5 ERO FOR EASTERN PORTIONS OF NEW
ENGLAND. BY NEXT WEEKEND, RAINFALL SHOULD DRIFT SOUTH WITH THE
FRONT MORE INTO PARTS OF THE SOUTH-CENTRAL PLAINS WITH LINGERING
SHOWERS ACROSS THE NORTHEAST.
HAZARDOUS HEAT IS EXPECTED TO EXPAND ACROSS THE SOUTHERN TIER
THROUGH AT LEAST NEXT WEEKEND (AND LIKELY BEYOND PER LATEST CPC
FORECASTS) AS THE UPPER RIDGE STRENGTHENS OVER THE SOUTH AND INTO
PARTS OF THE WEST. MUCH ABOVE NORMAL TEMPERATURES WILL EXPAND FROM
THE SOUTHERN HIGH PLAINS INTO THE SOUTHWEST AND CALIFORNIA, WITH
POTENTIAL FOR NUMEROUS RECORD DAILY DAYTIME HIGHS AND WARM
OVERNIGHT LOWS POSSIBLE. FARTHER EAST, AIR TEMPERATURES SHOULD BE
MORE NEAR NORMAL, BUT THE REAL STORY WILL BE OPPRESSIVE HUMIDITY
LEADING TO HEAT INDICES OF 105-115 FOR A LARGE PORTION THE SOUTH
FROM EASTERN TEXAS INTO THE SOUTHEAST AND FLORIDA. AGAIN, SOME
DAILY TEMPERATURE RECORDS ARE POSSIBLE. TEMPERATURES INTO THE 90S
TO NEAR 100 ARE POSSIBLE THURSDAY FARTHER NORTH INTO THE
SOUTH-CENTRAL PLAINS BUT SHOULD COOL OFF BY THE WEEKEND AS UPPER
LEVEL TROUGHING MOVES ACROSS THE REGION. ELSEWHERE, A COLD FRONT
DROPPING SOUTH FROM CANADA SHOULD BRING TEMPERATURES DOWN TO 5-15F
BELOW AVERAGE OVER PARTS OF THE NORTHERN AND CENTRAL PLAINS
THROUGH SUNDAY WITH SOME MODERATION EARLY NEXT WEEK AS UPPER
RIDGING TRIES TO BUILD IN.
SANTORELLI
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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