452
FXUS02 KWBC 132114
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
513 PM EDT THU JUL 13 2023
VALID 12Z SUN JUL 16 2023 - 12Z THU JUL 20 2023
...HAZARDOUS TO EXTREME HEAT IS FORECAST FOR THE ENTIRE SOUTHERN
TIER OF THE U.S. THROUGH EARLY NEXT WEEK AND BEYOND...
..ADDITIONAL HEAVY RAIN THREATS FOR THE NORTHEAST ON SUNDAY
..OVERVIEW
BROAD TROUGHING WILL BE MAINTAINED ACROSS THE EASTERN U.S. DURING
THE MEDIUM RANGE PERIOD AS AN UPPER LOW INITIALLY NEAR HUDSON BAY
DROPS SOUTH AND EAST SKIRTING THE UPPER GREAT LAKES BEFORE IT
LIFTS INTO SOUTHEAST CANADA, AND MULTIPLE SHORTWAVES ROTATE
THROUGH THE BASE OF THIS TROUGH ACROSS THE MIDWEST AND NORTHEAST.
THIS SHOULD TEND TO FOCUS SHOWERS AND STORMS ACROSS THESE REGIONS,
WITH AGAIN POTENTIAL FOR HEAVY RAINFALL IN AN ALREADY SOAKED
NORTHEAST. INITIAL RIDGING OUT WEST WILL SHIFT EAST INTO THE
NORTHERN PLAINS AS AN UPPER LOW/SHORTWAVE MOVES INTO THE NORTHWEST
EARLY NEXT WEEK. UPPER RIDGING MAY BUILD BRIEFLY AGAIN BEHIND IT
MID NEXT WEEK AHEAD OF A DEEP LOW DROPPING OUT OF THE GULF OF
ALASKA. MEANWHILE, AN ANOMALOUSLY STRONG UPPER RIDGE WILL BE
MAINTAINED OVER THE SOUTHERN TIER OF THE U.S. BRINGING HAZARDOUS
TO DANGEROUS HEAT FROM THE SOUTHWEST/CALIFORNIA EASTWARD TO THE
SOUTHERN PLAINS, SOUTHEAST, AND FLORIDA.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
GUIDANCE IS WELL CLUSTERED AROUND A SINGLE EVOLUTION OF THE
SYNOPTIC PATTERN DURING THE MEDIUM RANGE PERIOD. THE MODELS
SUGGEST THAT THE BUBBLE HIGH IN THE SOUTHWEST WILL EXPAND EASTWARD
INTO THE GULF COAST, WHILE SHORTWAVE ENERGY SWINGS THROUGH THE
MIDWEST AND NORTHEAST BENEATH AN UPPER TROUGH ANCHORED OVER JAMES
BAY. A NON-UKMET BLEND WAS USED THROUGHOUT THE PERIOD, IN PART,
BECAUSE IT STRUGGLED WITH DEPICTING THE HIGH OVER THE SOUTHWEST ON
DAY 3. THEREFORE, A GENERAL MODEL BLEND CONSISTING OF THE 00Z
EC/CMC AND 06Z GFS WERE USED THROUGH DAY 5. THE DETERMINISTIC
MODELS WERE IN BETTER AGREEMENT THAN USUAL. THE 00Z ECE AND 06Z
GEFS WERE INTRODUCED ON DAY 6 AND CONTINUED THROUGH THE END OF THE
PERIOD WITH THE INCLUSION OF THE 00Z CMCE ON DAY 7 AND THE REMOVAL
OF THE 06Z GFS. SOME UNCERTAINTY REMAINS WITH RESPECT TO THE
TIMING AND STRENGTH OF SHORTWAVE ENERGY PROPAGATING THROUGH THE
MIDWEST DURING THE MEDIUM RANGE, WHICH IS REFLECTED IN AN OBSCURE
QPF.
..WEATHER/HAZARDS HIGHLIGHTS
A FRONT MOVING INTO THE MIDWEST AND OHIO VALLEY AND EVENTUALLY
STALLING EARLY NEXT WEEK WILL BE THE FOCUS FOR SHOWERS AND STORMS
THROUGH MUCH OF THE PERIOD. LOCALLY HEAVY RAIN IS LIKELY IN SPOTS,
BUT STILL ENOUGH UNCERTAINTY TO PRECLUDE ANYTHING MORE THAN A
BROAD MARGINAL RISK ON THE DAYS 4 AND 5 EROS. A SURFACE LOW
LIFTING THROUGH THE NORTHEAST WILL BRING YET ANOTHER ROUND OF
HEAVY RAINFALL AS ANOMALOUS PRECIPITABLE WATER VALUES STREAM
NORTHWARD AHEAD OF A COLD FRONT. SLIGHT RISK HOLDS ON THE DAY 4
ERO ACROSS MUCH OF NEW ENGLAND, WHERE SOME LOCATIONS ARE EXTREMELY
SUSCEPTIBLE TO FLOODING DUE TO RECENT SIGNIFICANT HEAVY RAINFALL.
IT IS POSSIBLE A MODERATE RISK UPGRADE MAY BE NEEDED AS WE GET
CLOSER IN TIME, BUT RIGHT NOW THE MODELS KEEP THE HEAVIEST AXIS
JUST EAST OF THE MORE SUSCEPTIBLE AREAS OF NEW HAMPSHIRE AND
VERMONT. ELSEWHERE, SHOWERS AND STORMS LINGER NEAR THE GULF COAST
AND FLORIDA THROUGH EARLY NEXT WEEK, WITH MONSOONAL MOISTURE
RETURNING TO THE SOUTHWEST. DID OPT TO PLACE A MARGINAL RISK IN
THE AREA ON THE DAY 5 ERO WHERE THE BETTER SIGNAL FOR RAINFALL,
LOCALLY HEAVY, WAS LOCATED. THIS THREAT SHOULD CONTINUE INTO MID
NEXT WEEK AS WELL.
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, INCLUDING THE ALL-TIME HIGH TEMPERATURE IN LAS
VEGAS, NV, AND WARM OVERNIGHT LOW RECORDS ARE THREATENED THIS
WEEKEND 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 OF 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 ON SUNDAY SHOULD MODERATE
AND SHIFT EAST AS HEIGHTS LOWER EARLY NEXT WEEK OVER THIS REGION.
ABOVE NORMAL TEMPERATURES MAY EXPAND NORTHWARD INTO PARTS OF THE
CENTRAL PLAINS AND MISSISSIPPI VALLEY AND POINTS EAST EARLY NEXT
WEEK.
KEBEDE/SANTORELLI
HAZARDS:
- HEAVY RAIN ACROSS PORTIONS OF THE NORTHEAST, SUN, JUL 16.
- FLOODING POSSIBLE ACROSS PORTIONS OF THE NORTHERN PLAINS.
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE NORTHEAST.
- FLOODING LIKELY ACROSS PORTIONS OF THE NORTHEAST.
- HAZARDOUS HEAT ACROSS PORTIONS OF THE CENTRAL PLAINS, THE
CENTRAL ROCKIES, THE LOWER MISSISSIPPI VALLEY, THE CENTRAL GREAT
BASIN, THE TENNESSEE VALLEY, THE SOUTHERN ROCKIES, THE MIDDLE
MISSISSIPPI VALLEY, THE SOUTHERN MID-ATLANTIC, CALIFORNIA, THE
SOUTHEAST, THE SOUTHERN APPALACHIANS, THE SOUTHERN PLAINS, THE
SOUTHERN OHIO VALLEY, AND THE SOUTHWEST, SUN-THU, JUL 16-JUL 20.
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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