112
FXUS02 KWBC 160645
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
245 AM EDT TUE JUL 16 2024
VALID 12Z FRI JUL 19 2024 - 12Z TUE JUL 23 2024
...DANGEROUS HEAT AND WILDFIRE THREATS WILL BUILD OVER MUCH OF THE
WEST THIS WEEK AND INTO NEXT WEEK...
...MONSOONAL CONDITIONS CONTINUE FOR THE FOUR CORNERS STATES; AND
HEAVY RAINS FOR THE SOUTH, SOUTHEAST AND SOUTHERN MID- ATLANTIC...
..OVERVIEW
AN AMPLIFIED UPPER PATTERN WILL BE HIGHLIGHTED BY A STRONG RIDGE
ACROSS THE WESTERN U.S. AND A TROUGH OVER THE EAST-CENTRAL U.S.
THROUGH THE MEDIUM RANGE PERIOD. AN UPPER TROUGH WILL WORK TO THE
PACIFIC NORTHWEST BY EARLY NEXT WEEK, BUT PROGRESS WILL BE SLOW
DUE TO THE STRONG DOWNSTREAM RIDGE. DANGEROUS HEAT WILL DEVELOP
UNDERNEATH THE RIDGE, AND TEMPERATURES MAY REACH RECORD VALUES. IN
ADDITION TO DANGEROUS HEAT, LOW HUMIDITY/DRY FUELS AND BREEZY
WINDS WILL RESULT IN AN INCREASED THREAT OF WILDFIRES BY LATER
WEEK FOR PORTIONS OF THE PACIFIC NORTHWEST IN PARTICULAR. BETTER
MOISTURE WILL BE LOCATED FAR TO THE SOUTH WITH FOCUS ACROSS THE
SOUTHWEST/FOUR CORNERS REGION AND SOUTHERN ROCKIES WHERE MONSOONAL
CONDITIONS WILL LIKELY CONTINUE INTO NEXT WEEK.
UNDERNEATH THE TROUGH IN THE EAST-CENTRAL U.S., A SLOW MOVING
FRONTAL BOUNDARY WILL SAG INTO THE SOUTH-CENTRAL U.S., SOUTHEAST,
AND MID-ATLANTIC. THIS WAVY AND WELL DEFINED BOUNDARY IS FORECAST
TO STALL AND CREATE A PROLONGED PERIOD OF HEAVY RAIN THAT COULD
RESULT IN FLOODING CONCERNS GIVEN THE BROAD POOLED PLUME OF HIGH
PRECIPITATBLE WATER AIR. BROAD AREAS NORTH OF THE BOUNDARY WILL
SEE A BREAK IN THE HEAT AS COOLER AND DRIER AIR COMES FROM CANADA.
..GUIDANCE/PREDICTABILITY ASSESSMENT
GUIDANCE SPREAD THROUGH MEDIUM RANGE TIME SCALES AGAIN SEEMS LOWER
THAN NORMAL. A BLEND OF BEST CLUSTERED GUIDANCE FROM THE 18 UTC
GFS AND ESPECIALLY THE 12 UTC ECMWF/UKMET ALONG WITH THE 01 UTC
NATIONAL BLEND OF MODELS SEEMS TO OFFER A SOLID FORECAST BASIS
FRIDAY THROUGH THE WEEKEND WITH REASONABLE DETAIL CONSISTENT IN A
PATTERN WITH ABOVE NORMAL PREDICTABILITY. RECENT DIFFERENCES OVER
THE EAST/NORTHEAST PACIFIC HAVE EASED. OPTED TO ADD GEFS/ECMWF
ENSEMBLE MEAN DATA INTO THE BLEND TO REPLACE THE UKMET THAT IS NOT
AVAILABLE AT THESE LONGER TIME FRAMES. WPC PRODUCT CONTINUITY IS
WELL MAINTAINED AND IN LINE WITH NEWER 00 UTC GUIDANCE COMPOSITES.
..WEATHER/HAZARDS HIGHLIGHTS
A BIG WEATHER STORY WILL BE THE BUILDING AND PERSISTENCE OF A
MAJOR HEATWAVE OVER MUCH OF THE WEST THIS WEEK AND INTO NEXT WEEK.
THE NWS HEATRISK PRODUCT IS SHOWING WIDESPREAD MODERATE TO LOCALLY
MAJOR TO EXTREME HEATRISK VALUES DEVELOPING MID-WEEK AND
STRENGTHENING THIS WEEKEND, AND RECORD-SETTING TEMPERATURES WILL
BE POSSIBLE. THIS HEAT WAVE IS FORECAST TO CONTINUE INTO THE WEEK
TWO PERIOD, PER THE CLIMATE PREDICTION CENTER OUTLOOK, AND HOT
TEMPERATURES COULD RESULT IN A PROLONGED PERIOD OF ENHANCED
WILDFIRE DANGER AS WELL.
MEANWHILE, MONSOONAL MOISTURE WILL LINGER OVER THE FOUR CORNERS
REGION, WHICH WILL ALLOW FOR DAILY ROUNDS OF PRECIPITATION THAT
COULD RESULT IN FLASH FLOODING, ESPECIALLY NEAR STEEP TERRAIN AND
BURN SCARS. A MARGINAL RISK REMAINS IN THE EXCESSIVE RAINFALL
OUTLOOK (ERO) FOR DAY 4/FRIDAY AND DAY 5/SATURDAY FROM THE FOUR
CORNERS REGION TO THE SOUTH-CENTRAL ROCKIES/PLAINS WITH FAVORABLE
UPPER DIFFLUENCE, INSTABILITY, AND MOISTURE.
FAVORABLE UPPER LEVEL SUPPORT AND A WELL DEFINED/WAVY SURFACE
FRONT WILL SHIFT SOUTHWARD ACROSS THE CENTRAL AND EASTERN U.S.,
LEADING TO MULTIPLE ROUNDS OF HEAVY SHOWERS/THUNDERSTORMS. WITH
AMPLE MOISTURE AND INSTABILITY IN PLACE, LOCALLY HEAVY RAINFALL
WILL BE POSSIBLE AND MAY LEAD TO INSTANCES OF FLASH FLOODING. THE
DAY 4/FRIDAY AND DAY 5/SATURDAY EROS SHOW A SLOWLY SOUTHWARD
SHIFTING MARGINAL RISK AREA FROM EAST TEXAS TO THE SOUTH/SOUTHEAST
AND SOUTHERN MID-ATLANTIC. AN EMBEDDED SLIGHT RISK AREA INTRODUCED
FOR DAY 4/FRIDAY FOCUSES THE THREAT ACROSS THE EASTERN CAROLINAS
GIVEN POOLED HIGH PRECIPITABLE WATER VALUES IN A PATTERN WITH
HIGHLY FAVORABLE UPPER JET RIGHT ENTRANCE REGION SUPPORT. THERE IS
ALSO A RISK OF SHORT RANGE HEAVY RAINS TO PROVIDE LEAD WET SOILS. THE
WAVY BOUNDARY WILL MEANDER OVER THE REGION THIS WEEKEND INTO NEXT
WEEK, PROVIDING FOCUS FOR DAILY SUMMERTIME CONVECTION AND LOCAL
HEAVY RAIN FOR THE SOUTH/SOUTHEAST AND MID-ATLANTIC.
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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