556
FXUS02 KWBC 170700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 AM EDT WED APR 17 2024
VALID 12Z SAT APR 20 2024 - 12Z WED APR 24 2024
..OVERVIEW
THE PATTERN DURING THE MEDIUM RANGE PERIOD WILL CONTINUE TO
TRANSITION TO MORE PROGRESSIVE FLOW BY THIS WEEKEND AS AN OMEGA
BLOCK OVER THE NORTHEAST PACIFIC INTO WESTERN NORTH AMERICA AND
THE NORTHERN U.S. TIER BEGINS TO BREAK DOWN. ENERGY FROM THE WEST
SIDE OF A DEEP UPPER LOW INITIALLY OVER SOUTHEAST CANADA ON
SATURDAY WILL INTERACT WITH ANOTHER SHORTWAVE INTO THE SOUTHERN
PLAINS, INCREASING THE HEAVY RAIN THREAT ACROSS MUCH OF TEXAS ON
SATURDAY, CONTINUING INTO SUNDAY ACROSS THE SOUTHEAST AS THE
FRONTAL BOUNDARY IS SLOW TO MOVE THROUGH THE REGION. SECONDARY
ENERGY EJECTING FROM AN UPPER LOW/TROUGH OVER THE NORTHEAST PACIFIC
WILL SKIRT THE NORTHERN TIER AND MOVE THROUGH THE GREAT LAKES INTO
THE NORTHEAST EARLY NEXT WEEK. TROUGHING GENERALLY WILL GET
REESTABLISHED OVER THE WEST COAST BY NEXT TUESDAY-WEDNESDAY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST GUIDANCE SHOWS VERY GOOD AGREEMENT ACROSS THE CONUS
THROUGH MUCH OF THE PERIOD (SATURDAY-WEDNESDAY). THERE ARE SOME
TIMING DIFFERENCES WITH SHORTWAVE TROUGHING THROUGH THE SOUTHEAST
SUNDAY-MONDAY AND AGAIN WITH THE NEXT SHORTWAVE THROUGH THE GREAT
LAKES/NORTHEAST TUESDAY-WEDNESDAY. THESE DETAILS CREATE SOME
UNCERTAINTY IN THE EVENTUALLY (GENERALLY LIGHT) PRECIPITATION
PATTERN ACROSS THE SOUTHEAST AND NORTHEAST EARLY NEXT WEEK. LOTS
OF UNCERTAINTY LATE PERIOD AS WELL WITH THE EVOLUTION OF A DEEP
CLOSED LOW OVER THE GULF OF ALASKA WHICH LOOKS TO SEND SOME
ENERGY/TROUGHING TOWARDS THE WEST COAST.
THE WPC FORECAST FOR TONIGHT USED AN EQUAL BLEND OF THE LATEST
GFS, ECMWF, AND CMC FOR DAYS 3-5 (SATURDAY-MONDAY). FOR DAYS 6 AND
7, REPLACED THE CMC WITH THE GEFS MEAN GIVEN GREATER CMC
DIFFERENCES OFF THE WEST COAST. THE UKMET AND ECENS DATA CONTINUE
TO BE UNAVAILABLE DUE TO ONGOING IT ISSUES AT WPC/COLLEGE PARK, MD.
..WEATHER/HAZARDS HIGHLIGHTS
SHORTWAVE ENERGY INTO THE SOUTHERN PLAINS INTERACTING WITH A SLOW
MOVING FRONTAL BOUNDARY AND ANOMALOUS MOISTURE AND INSTABILITY WILL
INCREASE THE THREAT FOR HEAVY TO EXCESSIVE RAINFALL ACROSS MUCH OF
THE SOUTHERN PLAINS INTO THE LOWER MISSISSIPPI VALLEY ON SATURDAY.
A SLIGHT RISK CONTINUES ON TONIGHTS DAY 4 EXCESSIVE RAINFALL
OUTLOOK (SAT-SUN MORNING) ACROSS CENTRAL TO NORTHEAST TEXAS.
RAINFALL WILL CONTINUE INTO THE SOUTHEAST/CAROLINAS ON SUNDAY AS
THE FRONT SLOWLY SINKS THROUGH THAT REGION, AND THIS IS COVERED BY
A MARGINAL RISK ON THE DAY 5 ERO. THE NEXT SHORTWAVE THROUGH THE
NORTHERN PLAINS-GREAT LAKES-NORTHEAST WILL BE ACCOMPANIED BY SOME
GENERALLY LIGHT PRECIPITATION AS WELL EARLY NEXT WEEK.
THE UPPER TROUGH OVER THE NORTHERN TIER STATES AND EVENTUALLY INTO
THE EAST WILL SUPPORT BELOW NORMAL TEMPERATURES (WITH GREATER
ANOMALIES FOR HIGHS THAN LOWS) FOR MOST EAST OF THE ROCKIES BUT
FLORIDA BY NEXT WEEKEND. ABOVE NORMAL TEMPERATURES ACROSS THE
SOUTHWEST SHOULD GRADUALLY EXPAND NORTHWARD UNDERNEATH A BUILDING
WESTERN U.S. RIDGE AND PROGRESS EASTWARD INTO THE ROCKIES EARLY
NEXT WEEK. NORTHERN PARTS OF THE WEST MAY STAY NEAR NORMAL DUE TO
THE UPPER SHORTWAVE/COLD FRONT CROSSING THE REGION NEXT WEEK.
SANTORELLI
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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