276
FXUS02 KWBC 060700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 AM EDT SAT MAY 6 2023
VALID 12Z TUE MAY 9 2023 - 12Z SAT MAY 13 2023
..OVERVIEW
A QUASI-ZONAL UPPER LEVEL FLOW PATTERN WITH A BROAD UPPER RIDGE
OVER THE CENTRAL/NORTHERN PLAINS AND AN ARRIVING UPPER TROUGH
CENTERED OVER THE WEST COAST IS EXPECTED FOR TUESDAY. THIS TROUGH
IS FORECAST TO AMPLIFY FURTHER GOING INTO THE MIDDLE OF THE WEEK
ACROSS THE INTERMOUNTAIN WEST AND ROCKIES, AND THIS WILL TEND TO
BUILD THE RIDGE THAT WILL BE DOWNSTREAM FROM THE GULF COAST TO THE
MIDWEST, AND A TROUGH AXIS ACROSS THE NORTHEAST STATES THAT EXITS
ON THURSDAY. THE WESTERN U.S. TROUGH SHOULD THEN REACH THE
WESTERN HIGH PLAINS TO CLOSE OUT THE WORK WEEK WITH AN INCREASE IN
SHOWER AND THUNDERSTORM CHANCES ACROSS THE CENTRAL U.S., AND
GENERALLY ABOVE NORMAL TEMPERATURES EAST OF THE ROCKIES IN
RESPONSE TO THE UPPER RIDGE ALOFT.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE AGREES WELL ON THE OVERALL SYNOPTIC PATTERN
DESCRIBED ABOVE THROUGH ABOUT WEDNESDAY, AND A GENERAL MODEL BLEND
SUFFICES AS A STARTING POINT IN THE FORECAST PROCESS THROUGH THIS
TIME. MODEL UNCERTAINTY INCREASES SOME GOING INTO THE END OF THE
WEEK WITH THE CMC/ECMWF IN A SIMILAR LOCATION BUT THE GFS CENTERED
A BIT MORE TO THE NORTHEAST WITH THE MAIN UPPER LOW, BUT GREATER
DIFFERENCES IN REGARD TO EXPECTED MESOSCALE FEATURES THAT DEVELOP.
THERE IS A GENERAL CONSENSUS THAT THE RIDGE AXIS OVER THE
EAST-CENTRAL U.S. WILL TEND TO LIMIT THE EASTWARD PROGRESSION OF
THE FRONT. BY NEXT SATURDAY, THE CMC BECOMES STRONGER WITH AN
UPPER TROUGH JUST OFF THE EAST COAST. THE ENSEMBLE MEANS
ACCOUNTED FOR ABOUT HALF OF THE FORECAST BLEND BY THE SECOND HALF
OF THE WEEK.
..WEATHER/HAZARDS HIGHLIGHTS
SHOWERS AND STORMS ARE EXPECTED TO INCREASE IN COVERAGE ACROSS
MUCH OF THE PLAINS STATES GOING INTO THE TUESDAY-WEDNESDAY TIME
PERIOD AS MOISTURE ADVECTION FROM THE GULF OF MEXICO INCREASES
AHEAD OF THE ARRIVING COLD FRONT FROM THE ROCKIES. A MARGINAL
RISK FOR THE DAY 4 ERO IS PLANNED ACROSS PORTIONS OF NE/KS, AND
ALSO ACROSS MUCH OF CENTRAL AND SOUTHERN TEXAS. THE HEAVIEST
CONVECTION FOR DAY 5 IS CURRENTLY FAVORED ACROSS PORTIONS OF
EASTERN TEXAS AND THE ARKLATEX REGION AND THE NORTHERN PLAINS, AND
A MARGINAL RISK AREA IS PLANNED FOR BOTH OF THOSE AREAS. THE
POTENTIAL EXISTS FOR EVENTUAL SLIGHT RISKS IN FUTURE UPDATES ONCE
THE MAIN QPF AXIS BECOMES MORE APPARENT. LOOKING AHEAD TO
THURSDAY/FRIDAY, ADDITIONAL MODERATE TO LOCALLY HEAVY RAINFALL IS
EXPECTED ACROSS MAINLY THE SOUTHERN PLAINS, WITH THE POTENTIAL FOR
SEVERAL INCHES OF RAIN IN SOME AREAS OF TEXAS. THERE WILL LIKELY
BE ENOUGH COLD AIR ALOFT TO SUPPORT LOWERING SNOW LEVELS ACROSS
PORTIONS OF THE NORTHERN ROCKIES, AND LATE SEASON SNOW IS PROBABLE
FOR THE HIGHER ELEVATIONS OF WYOMING AND MONTANA DURING THIS TIME.
IN TERMS OF TEMPERATURES, HIGHS WILL LIKELY BE RUNNING 5 TO 15
DEGREES ABOVE EARLY MAY AVERAGES FROM THE CENTRAL/SOUTHERN PLAINS
TO THE OHIO VALLEY TO START THE WEEK, AND THEN REACHING INTO THE
MIDWEST STATES AND THE GREAT LAKES REGION GOING INTO THE MIDDLE OF
THE WEEK. WARMTH BUILDS ACROSS THE PACIFIC NORTHWEST BY FRIDAY
INTO SATURDAY WITH HIGHS POTENTIALLY UP TO 20 DEGREES ABOVE
MID-MAY AVERAGES. IT WILL LIKELY BE SLIGHTLY BELOW AVERAGE ACROSS
PORTIONS OF THE WEST COAST STATES AND THE INTERMOUNTAIN WEST IN
ASSOCIATION WITH THE UPPER TROUGH THROUGH WEDNESDAY BEFORE A
MODERATING TREND COMMENCES, BUT OVERNIGHT LOWS SHOULD BE CLOSER TO
AVERAGE HERE AND GENERALLY ABOVE AVERAGE EAST OF THE ROCKIES.
HAMRICK
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, EXPERIMENTAL EXCESSIVE RAINFALL
OUTLOOK, WINTER WEATHER OUTLOOK PROBABILITIES AND HEAT INDICES 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
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