929
FXUS02 KWBC 210812
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
412 AM EDT TUE JUL 21 2026
VALID 12Z FRI JUL 24 2026 - 12Z TUE JUL 28 2026
..TROPICAL STORM BERTHA IMPACTS CENTRAL TO WESTERN GULF COAST
..HEAVY RAINFALL/FLOODING THREAT FOR COASTAL SOUTHEAST U.S.
...HAZARDOUS HEAT TO BUILD BROADLY ACROSS THE WEST-CENTRAL U.S. AS
ONGOING MONSOONAL RAINS TEND TO EASE LATE WEEK INTO NEXT WEEK...
..OVERVIEW
HOT AND MOIST CONDITIONS WILL LINGER OVER THE SOUTH-CENTRAL U.S.
THIS WEEK OUTSIDE OF THE UNSETTLING INFLUENCE OF TROPICAL STORM
BERTHA. NORTHERN STREAM SHORTWAVES WORKING INTO AN UPPER TROUGH
POSITION OVER THE EAST AND MODERATING SURFACE FRONTS WILL BRING
FOCUS FOR ROUNDS OF LOCALLY HEAVY RAINS LATER THIS WEEK DOWN OVER
THE COASTAL SOUTHEAST U.S. WITH A SLOW MOVING AND MOISTURE POOLING
FRONT. ACTIVE STORMY CONDITIONS WILL MEANWHILE WORK WESTWARD OVER
THE GULF COAST AND INTO TEXAS AS FUELED BY TROPICAL STORM BERTHA
TRACK AND DEEP MOISTURE. MONSOONAL MOISTURE NOW STREAMING OVER THE
SOUTHWEST AND INTERMOUNTAIN WEST/ROCKIES AND AFFECTING THE CENTRAL
U.S. DOWNSTREAM WILL FUEL ENHANCED SHOWERS AND THUNDERSTORMS. HIGH
HEAT/UPPER RIDGING FOCUS OVER THE SOUTH-CENTRAL U.S. WILL SHIFT
NORTHWARD OVER THE PLAINS AND INTO THE SOUTHWEST/INTERMOUTAIN
WEST/ROCKIES. MONSOONAL FLOW EASES LATER PERIOD WITH TRANSITION.
..GUIDANCE/PREDICTABILITY ASSESSMENT
LATEST GUIDANCE CONTINUES TO SHOW GOOD AGREEMENT AND FORECAST
CONFIDENCE ON THE DEVELOPING LARGE SCALE PATTERN TO FEATURE A
LARGE WARMING UPPER RIDGE THAT BUILDS OVER THE INTERMOUNTAIN
WEST/SOUTHWEST/ROCKIES/PLAINS AS SANDWICHED BETWEEN AMPLIFIED UPPER
TROUGHS UPSTREAM JUST OFF THE WEST COAST AND DOWNSTREAM OVER THE
EAST. THERE ARE UNCERTAINTIES WITH INDIVIDUAL SYSTEMS WORKING
THROUGH THE FLOW AND ASSOCIATED SENSIBLE LOCAL WEATHER IMPACTS.
DIFFERENCES SEEM PARTIALLY MITIGATED BY A FAVORED GUIDANCE BLEND AS
CONSISTENT WITH INDIVIDUAL PREDICTABILITY. THE MOST SIGNIFICANT
FORECAST ISSUE CONCERNS THE TRACK AND IMPACT FOCUS FROM NORTHERN
GULF TROPICAL STORM BERTHA. BERTHA IS FORECAST BY THE NATIONAL
HURRICANE CENTER (NHC) TO TRACK WESTWARD NEAR THE CENTRAL GULF
COAST THEN TEXAS AND SLOWLY WEAKEN LATE WEEK TO MONITOR. PLEASE
SEE THE LATEST ADVISORIES FROM THE NHC AND YOUR LOCAL WEATHER
OFFICE FOR UPDATED INFORMATION. GUIDANCE SEEMS DEFICIENT WITH
HEAVY RAINFALL POTENTIAL ONSHORE GIVEN DEEP POOLED TROPICAL
MOISTURE AND TRACK VICINITY, SO THIS WAS MANUALLY ADJUSTED AT WPC.
..WEATHER/HAZARDS HIGHLIGHTS
FLOW AROUND A MAIN UPPER RIDGE WILL CONTINUE TO DRAW SIGNIFICANT
MONSOONAL MOISTURE INTO THE SOUTHWEST AND INTERMOUNTAIN
WEST/ROCKIES THIS WEEK, BUT MAY EASE THIS WEEKEND/EARLY NEXT WEEK.
MOISTURE WILL FUEL SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS
WITH POTENTIAL TO PRODUCE HEAVY RAINFALL AND LOCALIZED FLASH
FLOODING. SENSITIVE PLACES SUCH AS BURN SCARS, STEEP TERRAIN, ETC.,
WOULD BE THE MOST VULNERABLE TO POSSIBLE FLOODING CONCERNS.
MARGINAL RISKS OF EXCESSIVE RAINFALL SPAN THE SOUTHWEST AND
INTERMOUNTAIN WEST/ROCKIES AND JUMPS TO THE MID-MISSISSIPPI VALLEY
FRIDAY INTO SATURDAY, WITH A SMALL EMBEDDED SLIGHT RISK AREAS FOR
THE MID-MISSISSIPPI VALLEY FRIDAY WHERE CONVECTION MAY FOCUS/TRAIN.
UPPER RIDGE/CLOSED HIGH INFLUENCE OVER THE SOUTH-CENTRAL U.S.
OFFERS AT LEAST MAJOR HEATRISKS THIS WEEK AS TEMPERATURES UP TO
5-10F ABOVE ALREADY HOT AVERAGES COMBINE WITH HIGH HUMIDITY. EXPECT
SPOTTY RECORD HIGHS AND MORE WIDESPREAD RECORD OVERNIGHT LOWS TO
LIMIT RELIEF. HEAT INDICES RISE RISE UPWARDS TO 105-110+F IN SOME
SPOTS. HEAT FOCUS WILL EXPAND UP THROUGH THE PLAINS AND INTO THE
SOUTHWEST/INTERMOUNTAIN WEST/ROCKIES THIS WEEKEND/EARLY NEXT WEEK.
ELSEWHERE, REPEAT HEAVY RAINS/CONVECTION ARE FORECAST TO FOCUS
OVER THE EASTERN CAROLINAS/SOUTHEAST LATER WEEK/WEEKEND GIVEN
SUPPORT ALOFT AND SLOWED FRONTAL PUSH. WPC EXCESSIVE RAINFALL
MARGINAL RISKS FRIDAY AND SATURDAY ALSO HAS AN EMBEDDED EASTERN
CAROLINAS SLIGHT RISK AREA ON FRIDAY.
MEANWHILE TO THE SOUTH, TROPICAL STORM BERTHA IS FORECAST TO
TRACK WESTWARD NEAR THE CENTRAL AND WESTERN GULF COASTS TO TEXAS
INTO LATER THIS WEEK. DEEP TROPICAL MOISTURE ASSOCIATED WITH THIS
SYSTEM MAY FUEL A LOCALIZED THREAT FOR HEAVY RAIN/RUNOFF ISSUES. A
MARGINAL RISK AREA IS IN PLACE FOR THE CENTRAL TO WESTERN GULF
COAST FRIDAY INTO SATURDAY TO MONITOR.
UPSTREAM, PERSISTENT UPPER TROUGHING AND EMBEDDED MOISTURE FEED
OFFERS MULTI-DAY MID-SUMMER LIGHT-MODERATE RAIN CHANCES THIS PERIOD
WORKING ONSHORE INTO THE PACIFIC NORTHWEST.
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, 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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