808
FXUS02 KWBC 120545
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
145 AM EDT WED JUL 12 2023
VALID 12Z SAT JUL 15 2023 - 12Z WED JUL 19 2023
...HAZARDOUS TO EXTREME HEAT IS FORECAST FOR MUCH OF THE SOUTHERN
U.S. AND INTO THE SOUTHWEST INTO NEXT WEEK AND BEYOND...
...HEAVY RAIN CONCERNS LIKELY TO FOCUS FROM THE CENTRAL PLAINS AND
GULF COAST INTO PORTIONS OF THE NORTHEAST...
..OVERVIEW
THE PATTERN OVER THE CONUS DURING THE MEDIUM RANGE PERIOD SHOULD
TREND SLIGHTLY LESS AMPLIFIED WITH TIME. A DEEP UPPER LOW ANCHORED
NEAR HUDSON BAY ON SATURDAY SHOULD EVENTUALLY DROP SOUTH AND EAST
SKIRTING THE UPPER GREAT LAKES EARLY NEXT WEEK BEFORE IT MOVES
INTO SOUTHEAST CANADA. SMALL SCALE ENERGIES ROUNDING THE BASE OF
THE TROUGH THROUGH THE CENTRAL PLAINS AND MID-SOUTH WILL HELP TO
MAINTAIN GENERAL TROUGHING ACROSS THE MIDWEST AND NORTHEAST WITH
ADDITIONAL ROUNDS OF RAIN EXPECTED ACROSS THESE REGIONS AS WELL.
RIDGING WILL PROGRESS FROM THE NORTHWEST INTO THE NORTH-CENTRAL
U.S. AS AN UPPER LOW MOVES INTO BRITISH COLUMBIA WITH LOWER
HEIGHTS ACROSS THE NORTHWEST NEXT WEEK. MEANWHILE, TO THE SOUTH, A
POTENTIALLY DANGEROUS HEAT WAVE IS FORECAST TO OVERSPREAD THE
ENTIRE SOUTHERN TIER OF THE U.S. AND ESPECIALLY THE
SOUTHWEST/CALIFORNIA THROUGH THE WEEKEND AND EVEN WELL INTO NEXT
WEEK.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
OVERALL, THE LATEST GUIDANCE REMAINS IN EXCELLENT AGREEMENT ON THE
OVERALL SYNOPTIC PATTERN THROUGH THE PERIOD, THOUGH CONTINUES TO
OFFER TYPICAL DIFFERENCES IN THE SMALLER SCALE DETAILS. SOME
UNCERTAINTIES SURROUNDING IMPULSES ROUNDING THROUGH THE MIDWEST,
WHICH HAVE SIGNIFICANT IMPLICATIONS FOR SURFACE FEATURES AND
SENSIBLE WEATHER, INCLUDING POTENTIAL HEAVY RAINFALL/FLOODING,
ESPECIALLY ACROSS PARTS OF THE MID-MISSISSIPPI VALLEY AND MIDWEST,
AND INTO THE NORTHEAST. BETTER AGREEMENT TONIGHT ON THE UPPER LOW
INTO BRITISH COLUMBIA, BUT SOME QUESTION ON ANOTHER POTENTIAL LOW
BY DAY 7 JUST OFF THE COAST. OTHERWISE, EVEN LATE IN THE PERIOD,
THERE IS VERY GOOD AGREEMENT ON AN ANOMALOUSLY STRONG UPPER HIGH
BUILDING AND HOLDING STRONG OVER THE SOUTHWEST U.S. THROUGH
TUESDAY, AND THEN LIKELY SHIFTING BACK TO THE EAST NEXT WEDNESDAY.
THE WPC FORECASTS TONIGHT WERE BASED ON A COMPOSITE BLEND OF THE
DETERMINISTIC SOLUTIONS THROUGH DAY 5, WITH SOME INCLUSION OF THE
ENSEMBLE MEANS DAYS 6 AND 7 WITH THE GFS/ECMWF. THIS MAINTAINS
GOOD CONTINUITY WITH THE PREVIOUS WPC FORECAST AS WELL.
..WEATHER/HAZARDS HIGHLIGHTS
SHOWERS AND STORMS SHOULD INITIALLY FOCUS SATURDAY FROM THE
SOUTH-CENTRAL PLAINS INTO THE MID-SOUTH, OHIO VALLEY, AND THE
MID-ATLANTIC/NORTHEAST. GIVEN AVAILABLE MOISTURE AND INSTABILITY,
AT LEAST LOCALLY HEAVY RAINFALL SEEMS A GOOD BET FOR MANY
LOCATIONS, BUT STILL A LOT OF UNCERTAINTY EXACTLY WHERE. THE BEST
OVERLAP THOUGH IN THE CURRENT AVAILABLE GUIDANCE POINTS TO THE
TEXAS PANHANDLE INTO WESTERN OKLAHOMA WHERE A SMALL SLIGHT RISK
WAS MAINTAINED ON THE DAY 4 ERO GIVEN VERY WET ANTECEDENT
CONDITIONS. RAINFALL SHOULD SHIFT SOUTH AND EAST BY DAY 5/SUNDAY
AND ONCE AGAIN THE NORTHEAST IS LOOKING AT YET ANOTHER ROUND OF
HEAVY RAIN AS ANOMALOUS PRECIPITABLE WATER VALUES STREAM NORTHWARD
ALONG A COLD FRONT. A SLIGHT RISK WAS ADDED TO THE DAY 5 ERO FOR
EASTERN PORTIONS OF NEW ENGLAND GIVEN HOW SUSCEPTIBLE PARTS OF
THIS REGION IS RIGHT NOW DUE TO RECENT VERY HEAVY RAINFALL.
FARTHER SOUTH, ALSO INCLUDED A SLIGHT RISK ON THE DAY 5 ERO ACROSS
PARTS OF THE GULF COAST AND LOWER MISSISSIPPI VALLEY WITH A BROAD
MARGINAL RISK SURROUNDING THESE AREAS INCLUDING THE SOUTHEAST INTO
THE MID-ATLANTIC. ANOTHER COLD FRONT INTO THE CENTRAL
PLAINS/MIDWEST EARLY NEXT WEEK MAY BRING ADDITIONAL ROUNDS OF RAIN
AND STORMS ACROSS THE MID-MISSISSIPPI VALLEY/MIDWEST/OHIO VALLEY.
SHOWERS MAY LINGER THROUGH AT LEAST TUESDAY AS WELL ACROSS PARTS
OF THE MID-ATLANTIC AND THE NORTHEAST.
HAZARDOUS TO POTENTIALLY DANGEROUS HEAT WILL IMPACT MUCH OF THE
SOUTHWEST/CALIFORNIA EASTWARD INTO THE SOUTHERN STATES (AND LIKELY
BEYOND PER LATEST CPC FORECASTS). NUMEROUS DAILY HIGH TEMPERATURES
AND WARM OVERNIGHT LOW RECORDS ARE THREATENED THIS WEEKEND AND
EARLY NEXT WEEK ACROSS THIS REGION. FARTHER EAST, THE MAIN STORY
WILL BE OPPRESSIVE HUMIDITY LEADING TO HEAT INDICES OF 105-115
(LOCALLY HIGHER) FOR A LARGE PORTION THE SOUTH FROM EASTERN TEXAS
INTO THE SOUTHEAST AND FLORIDA. AGAIN, SOME DAILY TEMPERATURE
RECORDS ARE POSSIBLE. SEE KEY MESSAGES ISSUED BY WPC FOR
ADDITIONAL INFORMATION AND GRAPHICS RELATED TO THIS HEAT WAVE.
MUCH ABOVE NORMAL TEMPERATURES ACROSS THE NORTHWEST THIS WEEKEND
SHOULD MODERATE AND SHIFT EAST AS HEIGHTS LOWER EARLY NEXT WEEK
OVER THIS REGION. HEAT MAY EXPAND NORTHWARD INTO PARTS OF THE
CENTRAL PLAINS AND MISSISSIPPI VALLEY AND POINTS EAST EARLY NEXT
WEEK.
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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