845
FXUS02 KWBC 040700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 AM EDT SUN JUN 04 2023
VALID 12Z WED JUN 07 2023 - 12Z SUN JUN 11 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
THE UPPER LEVEL PATTERN DURING THE MEDIUM RANGE PERIOD NEXT WEEK
WILL REMAIN STAGNANT AND BLOCKY AS AN ANOMALOUSLY STRONG UPPER
RIDGE IS SANDWICHED BETWEEN TROUGHING ALONG THE WEST COAST AND
ALSO IN THE NORTHEAST. THIS PATTERN SUPPORTS DAILY SHOWERS AND
STORMS FROM THE SOUTHERN PLAINS INTO THE NORTHERN ROCKIES AND
PARTS OF THE GREAT BASIN, AN AREA WHICH HAS BEEN QUITE WET AS OF
LATE. THIS KEEPS ABOVE NORMAL TEMPERATURES FROM THE NORTHWEST INTO
THE CENTRAL U.S. WHILE THE SOUTHWEST AND NORTHEAST REMAIN COOL.
..GUIDANCE EVALUATION/PREDICTABILITY ASSESSMENT
THE LATEST GUIDANCE REMAINS IN GOOD AGREEMENT REGARDING THE
OVERALL BLOCKINESS OF THE SYNOPTIC PATTERN DURING THE MEDIUM RANGE
PERIOD. THERE REMAINS SOME DIFFERENCES IN THE DETAILS OF BOTH THE
WESTERN AND NORTHEAST TROUGHS, BUT MODELS AND ENSEMBLES
UNANIMOUSLY SUGGEST THE CENTRAL RIDGE COULD HOLD STRONG THROUGH AT
LEAST NEXT WEEKEND. IN THE NORTHEAST, WAVES OF ENERGY SHOULD HELP
REINFORCE TROUGHING ACROSS THE NORTHEAST THROUGH FRIDAY, BUT A
SHORTWAVE DROPPING IN TOWARDS THE UPPER GREAT LAKES FROM CANADA
COULD TRY TO PUSH THE NEW ENGLAND UPPER LOW UP TO THE NORTH AND
NEW TROUGHING BECOMING ESTABLISHED NEXT WEEKEND ACROSS THE GREAT
LAKES AND MIDWEST. THE GFS IS A LOT MORE AGGRESSIVE WITH THIS
SCENARIO BRINGING A DEEP CLOSED LOW TO JUST NORTH OF LAKE SUPERIOR
NEXT SUNDAY/DAY 7. THE ECMWF SHOWS AN OPEN SHORTWAVE, BUT SPREAD
IN THE ENSEMBLES SUGGEST EITHER SOLUTION IS PLAUSIBLE AND WORTH
WATCHING. THE WPC DAY 7 FORECAST LEANED MORE ON THE ENSEMBLE MEANS
WHICH IS IN BEST AGREEMENT WITH THE ECMWF (ALBEIT A BIT SLOWER).
THE CMC CONTINUES TO BE ALONE IN SUGGESTING A DIPOLE APPROACH TO
THE UPPER LOW OVER NEW ENGLAND RATHER THAN ONE CONSOLIDATED LOW
LIKE THE REST OF THE GUIDANCE SHOWS SO IT WAS NOT INCLUDED IN THE
BLEND AFTER DAY 4. THE UPPER LOW OVER CALIFORNIA CONTINUES TO
EXHIBIT SOME MINOR DIFFERENCES IN STRENGTH AND HOW QUICKLY IT
BECOMES ERODED BY TROUGHING TO THE NORTH, BUT A GENERAL MODEL
BLEND SEEMS SUFFICIENT.
THE WPC BLEND FOR TONIGHT USED A GENERAL DETERMINISTIC MODEL BLEND
FOR DAYS 3 AND 4, TRANSITIONING TO MOSTLY ENSEMBLE MEANS BY DAY 7.
FAVORED THE ECMWF LATE PERIOD OVER THE GFS GIVEN THE GFS ISSUES
OVER THE GREAT LAKES AND ITS BETTER RUN-TO-RUN CONSISTENCY OUT
WEST. THIS APPROACH ALSO MAINTAINED GOOD CONTINUITY WITH THE
PREVIOUS WPC FORECAST.
..WEATHER/HAZARDS HIGHLIGHTS
A DAILY DIURNAL RISK FOR HEAVY SHOWERS AND THUNDERSTORMS WILL BE
MAINTAINED THROUGH THE PERIOD FROM THE SOUTHERN PLAINS TO THE
NORTHERN ROCKIES AND WESTWARD INTO THE GREAT BASIN AS TROPICAL
PACIFIC MOISTURE IS FUNNELED NORTHWARD IN BETWEEN A STRONG CENTRAL
U.S. RIDGE AND AN UPPER LOW PARKED OVER CALIFORNIA. FOR NOW, THE
DAY 4 EXCESSIVE RAINFALL OUTLOOK CONTINUES TO DEPICT JUST ONE
LARGE MARGINAL RISK AREA FOR THIS REGION, HOWEVER EMBEDDED SLIGHT
RISK AREAS MAY BECOME NECESSARY IF HEAVY RAINS FOCUS OVER
ANTECEDENT WET AREAS. BY DAY 5, THE MARGINAL RISK REGION IS
LARGELY THE SAME AS DAY 4, BUT DID ADD A SLIGHT RISK FOR PARTS OF
CENTRAL/EASTERN MONTANA GIVEN MORE FAVORABLE MOISTURE AND DYNAMICS
AND CONSIDERING ANTECEDENT CONDITIONS IN THIS REGION. THE RISK MAY
EXTEND PAST DAY 5 AS WELL AS A FRONTAL BOUNDARY BECOMES
ESTABLISHED OVER THE REGION.
ELSEWHERE, A FRONT THROUGH THE GREAT LAKES/UPPER MIDWEST SHOULD
FOCUS SHOWERS AND STORMS AHEAD OF IT ACROSS THE NORTHERN
PLAINS/UPPER MISSISSIPPI VALLEY EARLY TO MID WEEK. IN THE
NORTHEAST, THE DEEPENING UPPER TROUGH/LOWS SHOULD FAVOR POCKETS OF
RAINFALL INTO FRIDAY AS MOISTURE GETS WRAPPED BACK INTO ESPECIALLY
NORTHERN MAINE FROM A LINGERING LOW PRESSURE SYSTEM NEAR THE
COAST. IN FLORIDA, A LINGERING WEAK FRONT SHOULD SUPPORT UNSETTLED
CONDITIONS OVER THE SUNSHINE STATE WITH BETTER HEAVY RAIN CHANCES
IN SOUTHERN FLORIDA LATE WEEK AS DEEPER MOISTURE GETS PULLED NORTH.
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 5-10F ANOMALIES FOR HIGHS POSSIBLE MOST DAYS.
MODERATION BACK TOWARDS NORMAL IS EXPECTED NEXT WEEKEND AS
LOWERING HEIGHTS MOVES INTO THE REGION. THE NORTHWEST WILL BE THE
OTHER FOCUS FOR VERY WARM TEMPERATURES, WITH HIGHS 10-20F OR SO
ABOVE NORMAL WEDNESDAY AND THURSDAY. EXPECT NEAR TO BELOW NORMAL
TEMPERATURES OVER THE NORTHEAST AND AT TIMES INTO THE MID-ATLANTIC
BENEATH UPPER TROUGHING. 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. 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, 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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