593
FXUS02 KWBC 111853
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
153 PM EST MON NOV 11 2024
VALID 12Z THU NOV 14 2024 - 12Z MON NOV 18 2024
19Z UPDATE: OVERALL, THE 12Z MODEL GUIDANCE IS IN EXCELLENT
AGREEMENT ACROSS THE CONTINENTAL U.S. FOR BOTH THURSDAY AND FRIDAY,
AND THEREFORE A MULTI-DETERMINISTIC MODEL BLEND WORKS WELL AS A
STARTING POINT IN THE FORECAST PROCESS. THE UKMET IS HEAVIER WITH
QPF ACROSS PORTIONS OF THE CAROLINAS THAT DOES NOT HAVE MUCH
SUPPORT FROM THE MODEL CONSENSUS, BUT OTHERWISE IT MATCHED UP WELL
ELSEWHERE. BEGINNING LATE SATURDAY, THE CMC BECOMES MORE
PROGRESSIVE WITH THE TROUGH ACROSS THE DESERT SOUTHWEST AND THEN
EJECTS IT ACROSS THE SOUTHERN PLAINS, WHEREAS THE GFS/ECMWF FAVOR A
CLOSED LOW THAT IS SLOWER TO LIFT OUT. EVEN GREATER DIFFERENCES
EMERGE OVER THE PACIFIC NORTHWEST BY NEXT MONDAY, AND THIS IS WHERE
AN ENSEMBLE MEAN APPROACH WORKS BEST, AND ENSEMBLE MEANS ACCOUNTED
FOR ABOUT 40-50% OF THE FORECAST BY THAT TIME. NO CHANGES WERE
NEEDED FOR THE DAY 4 AND 5 EROS, WHICH REMAIN VOID OF ANY EXCESSIVE
RAINFALL AREAS GIVEN THE RELATIVELY UNEVENTFUL QPF THAT IS
EXPECTED. THE PREVIOUS FORECAST DISCUSSION IS APPENDED BELOW FOR
REFERENCE. /HAMRICK
-----------------------
..OVERVIEW
A SHORTWAVE INTO THE EAST AS THE PERIOD BEGINS THURSDAY WILL BRING
LIGHT TO MODERATE MUCH-NEEDED PRECIPITATION TO PARTS OF THE OHIO
VALLEY/MID-ATLANTIC/NORTHEAST ON THURSDAY. THIS ENERGY WILL EXIT
THE COAST BY FRIDAY, COMBINING WITH AN UPPER LOW NEAR MAINE THAT
LINGERS FOR A FEW DAYS. UPPER RIDGING WILL PROGRESS FROM THE
CENTRAL TO EASTERN U.S. BRINGING A RETURN TO SEASONABLY WARM
TEMPERATURES. MEANWHILE, A TROUGH ENTERING THE WEST ON THURSDAY
WILL DEEPEN AS IT SLOWLY SHIFTS EAST NEXT WEEKEND AND INTO EARLY
NEXT WEEK. ANOTHER SHORTWAVE INTO THE PACIFIC NORTHWEST WILL BRING
A CHANCE FOR ENHANCED PRECIPITATION TO THAT REGION.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE GUIDANCE CONTINUES TO SHOW GOOD AGREEMENT ON THE OVERALL LARGE
SCALE PATTERN ACROSS THE CONUS FOR THE UPCOMING MEDIUM RANGE
PERIOD, BUT PLENTY OF UNCERTAINTY IN THE DETAILS AND EVOLUTION OF
INDIVIDUAL SYSTEMS. MODELS HAVE TRENDED BETTER IN TERMS OF
TIMING/AMPLITUDE OF THE SHORTWAVE INTO THE EAST, THOUGH SOME
QUESTION ON ENERGY AS IT GETS WRAPPED INTO THE UPPER LOW PARKED OFF
THE NORTHEAST COAST. THE TROUGH INTO THE WEST ALSO SHOWS GOOD
AGREEMENT THE FIRST HALF OF THE PERIOD, BUT BY SUNDAY AND MONDAY
DETAILS GET HIGHLY UNCERTAIN. THERE IS SOME SUGGESTION THAT AN
UPPER LOW MAY BREAK OFF OVER/NEAR SOUTHERN CALIFORNIA AROUND SUNDAY
AND THE TIMING/EVOLUTION OF THIS PROGRESSING EASTWARD INTO MONDAY
HAS BIG IMPLICATIONS FOR THE LATE WEEKEND PRECIPITATION PATTERN
ACROSS THE SOUTH-CENTRAL PLAINS. THE ECMWF IS MUCH QUICKER TO
WEAKEN THE LOW AND MOVE IT EAST, BUT THE NEW 00Z RUN (AVAILABLE
AFTER FORECAST GENERATION TIME) DID SLOW DOWN. THE GFS REMAINS THE
STRONGEST AND SLOWEST. WPC PREFERS A MIDDLE GROUND SOLUTION CLOSEST
TO THE CMC AND ENSEMBLE MEANS.
THE WPC FORECAST BLEND FOR TONIGHT USED AN EQUAL BLEND OF THE
DETERMINISTIC GUIDANCE (MINUS THE UKMET WHICH WAS SLOWER WITH THE
EASTERN SHORTWAVE) FOR THE FIRST HALF OF THE PERIOD. AFTER THIS,
INCREASED THE ENSEMBLE MEANS TO 70 PERCENT OF THE BLEND BY DAY
7/MONDAY TO ACCOUNT FOR RAPIDLY LOWER CONFIDENCE IN THE FLOW
SPECIFICS ESPECIALLY OUT WEST.
..WEATHER/HAZARDS HIGHLIGHTS
A SHORTWAVE INTO THE PACIFIC NORTHWEST ON THURSDAY WILL CONTINUE
TO BRING SOME ADDITIONAL RAINFALL AND HIGHER ELEVATIONS SNOWS, BUT
THE HEAVIEST AND MOST IMPACTFUL PRECIPITATION SHOULD BE IN THE
SHORT RANGE PERIOD. PRECIPITATION ACROSS THE NORTHWEST SHOULD TREND
LIGHTER THURSDAY-FRIDAY WITH MODERATE MOUNTAIN SNOWS CONTINUING
ACROSS THE NORTHERN ROCKIES AND INTO THE SIERRA NEVADA RANGE.
ACROSS THE EAST, MODEST RAINFALL SHOULD ACCOMPANY A COLD FRONT AS
IT PASSES THROUGH THE EAST ON THURSDAY, BUT GIVEN MUCH OF THIS
REGION REMAINS IN A DROUGHT, RAINFALL SHOULD BE MORE BENEFICIAL
THAN HAZARDOUS. AS SUCH, THE DAYS 4 AND 5 (THURSDAY-FRIDAY)
EXCESSIVE RAINFALL OUTLOOKS ARE BLANK ACROSS THE CONUS.
AFTER FRIDAY, MOISTURE ON THE NORTH SIDE OF A SURFACE LOW EJECTING
INTO THE NORTHERN PLAINS MAY BRING SOME LIGHT RAIN OR SNOW FROM
EASTERN MONTANA TO THE UPPER MIDWEST. AS THE WESTERN TROUGH
DEEPENS, IT MAY BEGIN TO TAP MOISTURE TO INCREASE PRECIPITATION
CHANCES ACROSS THE SOUTH-CENTRAL PLAINS. HOWEVER, EXTENT AND
AMOUNTS OF THIS RAINFALL REMAINS UNKNOWN GIVEN THE UNCERTAINTIES IN
THE EVOLUTION OF THIS TROUGH OVER THE SOUTHWEST. A NORTHERN STREAM
SHORTWAVE INTO THE PACIFIC NORTHWEST SHOULD BRING ANOTHER ROUND OF
MODEST RAIN AND MOUNTAIN SNOWS TO WESTERN WASHINGTON/OREGON AND
THE CASCADES NEXT WEEKEND.
ABOVE NORMAL TEMPERATURES WILL PROGRESS EASTWARD WITH TIME FROM
THE NORTHERN PLAINS/MIDWEST THURSDAY-FRIDAY, ENVELOPING THE EAST BY
SUNDAY INTO MONDAY. DAYTIME HIGHS COULD BE 10-15 DEGREES ABOVE
NORMAL IN SOME SPOTS. OUT WEST, TEMPERATURES WILL TREND MUCH COOLER
WITH TIME AS UPPER TROUGHING AMPLIFIES OVER THE REGION AND
PERSISTS INTO EARLY 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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