676
FXUS02 KWBC 141900
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
200 PM EST SAT DEC 14 2024
VALID 12Z TUE DEC 17 2024 - 12Z SAT DEC 21 2024
..OVERVIEW
THE MEDIUM RANGE PERIOD BEGINS TUESDAY WITH A SHORTWAVE SHIFTING
THROUGH THE NORTHEAST AS ANOTHER ENTERS THE WEST COAST. THE LATTER
WILL BE RESPONSIBLE FOR A SIGNIFICANT PATTERN SHIFT AS IT AMPLIFIES
ACROSS THE CENTRAL-EASTERN U.S. MID TO LATE WEEK AND RIDGING
DEVELOPS UPSTREAM OVER THE WEST. THIS SHOULD PROMOTE WARMER AND
DRIER CONDITIONS ACROSS THE WEST, AND COOLING TEMPERATURES AND
PRECIPITATION FOR THE EAST, WITH A POTENTIAL EMERGING NOR'EASTER
THREAT LATE WEEK, BUT WITH LOW CONFIDENCE.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE OVERALL SYNOPTIC TREND IS FOR A SINGULAR AMPLIFIED TROUGH TO
TRAVERSE THE CONUS DURING THE MEDIUM RANGE PERIOD. THE GFS/GEFS
SUITE TRENDED CLOSER TO A SLOWER PATTERN WITH A CUTOFF LOW
DEVELOPING OVER THE FOUR CORNERS REGION. OTHERWISE, THERE'S A
GENERAL CONSENSUS FOR A CERTAIN THE AFOREMENTIONED SYNOPTIC TREND.
A GENERAL MODEL BLEND CONSISTING OF THE DETERMINISTIC 00Z
EC/CMC/UKMET AND 06 GFS WERE USED THROUGH DAY 4. THE ENSEMBLE MEANS
WERE INTRODUCED ON DAY 5 AND INCREASED IN WEIGHTING THROUGH DAY 7.
..WEATHER/HAZARDS HIGHLIGHTS
A LINGERING SURFACE FRONT ACROSS THE MID-SOUTH SHOULD BE
ACCOMPANIED BY SOME MODEST PRECIPITATION, BUT DOESN'T AT THIS TIME
APPEAR HAZARDOUS. DETAILS OF THE SURFACE PATTERN AND CORRESPONDING
PRECIPITATION COVERAGE, AMOUNTS, AND TIMING OVER THE
CENTRAL/EASTERN U.S. BECOME INCREASINGLY UNCERTAIN BY WEDNESDAY
THOUGH, BUT MODELS DO CONTINUE TO INDICATE ANOTHER ROUND OF
MODERATE TO HEAVY RAINFALL EMERGING IN THE SOUTH-CENTRAL U.S. TO
MID-SOUTH. THERE REMAINS ENOUGH UNCERTAINTY TO PRECLUDE ANY SORT OF
RISK AREAS ON THE DAY 5/WEDNESDAY EXCESSIVE RAINFALL OUTLOOK AT
THIS TIME, BUT THERE IS SOME GENERAL AGREEMENT ON ENHANCED RAINFALL
ACROSS PORTIONS OF THE SOUTHERN-CENTRAL APPALACHIANS WHERE SOIL
MOISTURE IS ABOVE NORMAL. PRECIPITATION MAY SPREAD ACROSS THE
EASTERN SEABOARD ON THURSDAY- FRIDAY, WITH SOME WINTRY WEATHER
POSSIBLE ON THE NORTHWESTERN SIDE OF THE LOW TRACK. THIS FORECAST
INDICATES SOME 10-30 PERCENT PROBABILITIES OF 0.25" QPF IN THE FORM
OF SNOW IN THE INTERIOR NORTHEAST ESPECIALLY IN HIGHER ELEVATIONS,
BUT CONTINUE TO MONITOR FORECASTS BECAUSE SNOW AMOUNTS AND
PLACEMENT WILL BE QUITE SENSITIVE TO THE UNCERTAIN EVENTUAL LOW
TRACK.
THE NORTHERN HALF OF THE WEST COAST AND INTO THE NORTHWEST SHOULD
SEE ANOTHER EPISODE OF RAIN AND HIGHER ELEVATION SNOW LASTING INTO
TUESDAY. AFTER THAT, THE WEST SHOULD SEE DRIER CONDITIONS
UNDERNEATH RIDGING, OTHER THAN PERHAPS SOME MOISTURE INTO WESTERN
WASHINGTON ROUNDING THE RIDGE.
WITHIN AN INITIAL GENERALLY MILD PATTERN ACROSS THE LOWER 48,
WARMEST ANOMALIES SHOULD EXTEND FROM THE SOUTHWEST/ROCKIES INTO TO
THE EAST ON TUESDAY. EXPECT A DECENT AREA OF HIGHS 10-15 DEGREES
ABOVE NORMAL AND ANOMALIES UP TO PLUS 15-25 DEGREES IN PLACES FOR
MORNING LOWS. AFTER WEDNESDAY, TEMPERATURES SHOULD TREND BACK TO
NORMAL ACROSS THE CENTRAL- EASTERN U.S. WITH A WARMING TREND OUT
WEST. AS TROUGHING GETS ESTABLISHED ACROSS THE EAST LATE WEEK, AN
ARCTIC HIGH WILL SPREAD BELOW NORMAL TEMPERATURES FROM THE NORTHERN
PLAINS/UPPER MIDWEST INTO MUCH OF THE EAST BY NEXT WEEKEND.
KEBEDE/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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