125
FXUS02 KWBC 012024
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
423 PM EDT THU JUN 01 2023
VALID 12Z SUN JUN 04 2023 - 12Z THU JUN 08 2023
...BROAD MULTI-DAY THUNDERSTORM AND LOCAL HEAVY RAIN THREAT FROM
THE NORTHERN ROCKIES TO THE SOUTHERN GREAT PLAINS CONTINUES WELL
INTO NEXT WEEK...
..OVERVIEW
A STRONG/BLOCKING UPPER RIDGE/HIGH BUILDS OVER THE NORTHERN
PLAINS/MANITOBA THIS WEEKEND AND PERSISTS WELL INTO NEXT WEEK,
SUPPORTING PROLONGED ABOVE NORMAL TEMPERATURES FROM THE NORTHERN
PLAINS INTO MIDDLE/UPPER MISSISSIPPI VALLEY THROUGH AT LEAST NEXT
THURSDAY. WEAKENING SHORTWAVE/UPPER LOW ENERGY LINGERING OVER THE
NORTHERN ROCKIES ALONG WITH A FOLLOWING SOUTHERN STREAM PACIFIC
LOW THAT REACHES SOUTHERN CALIFORNIA MONDAY WILL MAINTAIN PERIODS
OF CONVECTION OVER THE ROCKIES AND PARTS OF THE CENTRAL/SOUTHERN
PLAINS, SIERRA NEVADA AND GREAT BASIN/SOUTHERN CASCADES THROUGH
MUCH OF NEXT WEEK. ABOVE NORMAL TEMPERATURES WILL PREVAIL OVER THE
NORTHWESTERN AND NORTH-CENTRAL STATES THROUGH AT LEAST MIDWEEK.
CONFIDENCE INCREASES FOR TROUGHING AND CLOSED LOWS TO PERSIST OVER
THE NORTHEAST FOR MUCH IF NOT ALL OF NEXT WEEK IN THIS BLOCKED
PATTERN. THIS ANOMALOUS LOW AND ASSOCIATED TROUGH WILL BRING COOL
CONDITIONS TO THE EASTERN SEABOARD THROUGH THE PERIOD WITH WETTER
CONDITIONS FOR AT LEAST NEW ENGLAND.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
CONFIDENCE HAS INCREASED ON A PAIR OF LOWS AFFECTING THE NORTHEAST
THROUGH THE MEDIUM RANGE FORECAST PERIOD. THE FIRST DEVELOPS OVER
THE CANADIAN MARITIMES SATURDAY AND PERSISTS EAST OF MAINE THROUGH
SUNDAY NIGHT WHEN A REINFORCING WAVE FROM QUEBEC CLOSES INTO AN
UPPER LOW AS IT TRACKS SOUTHEAST OVER THE NORTHEASTERN STATES
MONDAY BEFORE STALLING/OCCLUDING (PER THE 00Z ECMWF/12Z GFS) AND
EXPANDING OVER THE NORTHEAST INTO OR THROUGH THURSDAY. THE 12Z CMC
PRODUCES A WEAKER WESTERN WAVE THAT FAILS TO CLOSE AS WELL OVER
THE NORTHEAST (IT HAS AN OPEN WAVE OVER THE NORTHEAST ON TUESDAY
FOR EXAMPLE). THE 12Z GFS/GEFS IS DEEPER AND FARTHER SOUTH WITH
THE UPPER LOW POSITION THAN THE 00Z ECMWF WHICH IS LIKELY DUE TO
FURTHER REINFORCING SHORTWAVE TROUGHS FROM CANADA WHICH ARE
UNDERSTANDABLY LOW CONFIDENCE IN POSITION/STRENGTH BY DAY 5/6.
FARTHER WEST A KEY FEATURE IS THE LOW CURRENTLY SOUTH OF THE GULF
OF ALASKA THAT MERELY DRIFTS EAST TO NORTHERN BC THROUGH EARLY
NEXT WEEK IN THE BLOCKED PATTERN. THE CONCERN FOR THE CONUS IS HOW
FAR SOUTH THE ASSOCIATED TROUGH GETS OVER THE PACIFIC NORTHWEST
AND NORTHERN ROCKIES. 12Z GUIDANCE IS IN GREAT AGREEMENT FOR THE
TROUGH AXIS TO DIP SOUTH OF CANADA WHICH SHOULD HAVE LITTLE EFFECT
ON THE PACIFIC NORTHWEST AND BE A FACTOR IN ALLOWING SUB-TROPICAL
MOISTURE TO BE DRAWN NORTH OVER THE NORTHERN ROCKIES. 12Z GUIDANCE
REMAINS CONSISTENT/SIMILAR FOR THE UPPER LOW REACHING SOUTHERN
CALIFORNIA MONDAY AND LINGERING OVER CALIFORNIA INTO THE MIDDLE OF
NEXT WEEK.
DECENT AGREEMENT AMONG GUIDANCE AVAILABLE THIS MORNING (00Z/06Z)
ALLOWED MOSTLY DETERMINISTIC SOURCES THROUGH DAY 5 WITH A FOCUS
TOWARD THE 00Z ECENS/06Z GEFS FOR DAYS 6/7.
..WEATHER/HAZARDS HIGHLIGHTS
A CENTRAL CONTINENTAL RIDGE WITH WEAK TROUGHING OVER THE
INTERMOUNTAIN WEST KEEPS A MAINLY DIURNAL RISK FOR HEAVY SHOWERS
AND THUNDERSTORMS OVER MUCH OF THE ROCKIES/HIGH PLAINS THROUGH
TEXAS AND THE SIERRA NEVADA/GREAT BASIN INTO OR THROUGH NEXT WEEK.
LOCALIZED FLASH FLOOD POTENTIAL CONTINUES THROUGH AT LEAST MONDAY
NIGHT GIVEN WET GROUND CONDITIONS FROM RECENT AND SOON TO OCCUR
RAINFALL. THE DAYS 4-5 EXCESSIVE RAINFALL OUTLOOKS (COVERING
SUNDAY THROUGH MONDAY NIGHT) DEPICT MARGINAL RISK AREAS SPANNING
THE ROCKIES/PORTIONS OF THE HIGH PLAINS THROUGH MUCH OF THE
SOUTHERN PLAINS WHERE THE COMBINATION OF BROAD FLOW FROM THE WEST
GULF OF MEXICO UP THE GREAT PLAINS ALONG WITH SOME INSTABILITY.
INCREASING TROPICAL PACIFIC MOISTURE FROM THE UPPER LOW REACHING
SOUTHERN CALIFORNIA MONDAY ALLOWS DIURNAL HEAVY RAIN THREATS FOR
THE SIERRA NEVADA FOR DAY 4, EXPANDING OVER THE GREAT BASIN FOR
DAY 5. EMBEDDED SLIGHT RISK AREAS MAY BECOME NECESSARY,
PARTICULARLY IF THE HEAVY RAIN FOCUS IS OVER ANTECEDENT WET AREAS.
THE DEEPENING UPPER TROUGH/LOWS SHOULD FAVOR DIURNALLY FAVORED
POCKETS OF RAINFALL OVER AND NEAR THE NORTHEAST THROUGH THURSDAY.
12Z GUIDANCE IS IN DECENT AGREEMENT FOR THE NHC MONITORED FEATURE
IN THE EASTERN GULF ON IT TRACKING SOUTH, THOUGH LINGERING
TROUGHING OVER THE FLORIDA PENINSULA SHOULD ALLOW FOR WETTER
CONDITIONS TO CONTINUE THERE INTO EARLY NEXT WEEK.
CENTRAL U.S. RIDGING ALOFT WILL MAINTAIN AN AXIS OF ABOVE NORMAL
TEMPERATURES FROM THE NORTHERN PLAINS SOUTH-SOUTHEAST TO THE
MID-SOUTH, WITH PLUS 10-15F ANOMALIES FOR HIGHS LIKELY EACH DAY.
INITIAL WARMTH OVER THE GREAT LAKES WILL MODERATE EARLY NEXT WEEK
AFTER A COLD FRONT PUSHES THROUGH FROM THE NORTHEAST. THE
NORTHWEST WILL BE THE OTHER FOCUS FOR VERY WARM TEMPERATURES, WITH
HIGHS 10-20F OR SO ABOVE NORMAL THROUGH AT LEAST MIDWEEK. EXPECT
BELOW NORMAL TEMPERATURES OVER THE NORTHEAST AND AT TIMES INTO THE
MID-ATLANTIC AS UPPER TROUGHING BECOMES ESTABLISHED. CLOUDS AND
PERIODS OF RAINFALL SHOULD KEEP HIGHS 5-10F OR SO BELOW NORMAL
OVER THE SOUTHERN HALF OF THE ROCKIES/HIGH PLAINS FOR MOST OF THE
PERIOD AND THE UPPER LOW REACHING SOUTHERN CALIFORNIA MONDAY WILL
ALSO BRING A COOLING TREND INTO THE SOUTHWESTERN U.S. FOR THE
EARLY-MIDDLE PART OF NEXT WEEK.
JACKSON
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
HAZARDS:
- FLOODING POSSIBLE ACROSS PORTIONS OF THE NORTHERN PLAINS.
- FLOODING OCCURRING OR IMMINENT ACROSS PORTIONS OF THE NORTHERN
ROCKIES AND THE NORTHERN GREAT BASIN.
- FLOODING LIKELY ACROSS PORTIONS OF THE CENTRAL ROCKIES, THE
CENTRAL GREAT BASIN, AND THE NORTHERN GREAT BASIN.
- MUCH ABOVE NORMAL TEMPERATURES ACROSS PORTIONS OF THE PACIFIC
NORTHWEST AND THE NORTHERN GREAT BASIN, MON-WED, JUN 5-JUN 7.
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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