231
FXUS02 KWBC 130637
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
137 AM EST FRI DEC 13 2024
VALID 12Z MON DEC 16 2024 - 12Z FRI DEC 20 2024
..OVERVIEW
THE LATEST MEDIUM RANGE FORECAST CONTINUE TO SHOW A SIGNIFICANT
PATTERN SHIFT NEXT WEEK, TRANSITIONING FROM A SERIES OF PROGRESSIVE
AND WEAKER SHORTWAVES TO AMPLIFIED WESTERN U.S. RIDGING AND
AMPLIFIED MEAN TROUGHING OVER THE CENTRAL-EASTERN STATES. A
SHORTWAVE INTO THE WEST EARLY WEEK SHOULD BRING SOME ADDITIONAL
PRECIPITATION, BUT CONDITIONS SHOULD TREND DRIER AND WARMER MID TO
LATE WEEK. A COUPLE OF COLD FRONTS WILL MARCH EASTWARD FROM THE
CENTRAL U.S. TO THE EAST COAST, WITH SOME POTENTIALLY HEAVY
PRECIPITATION TO ACCOMPANY AND NOTICEABLY COOLER TEMPERATURES BY
THE SECOND HALF OF THE WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
BESIDES SOME RELATIVELY MINOR TIMING/SURFACE DETAIL DIFFERENCES,
THE MODELS ARE STILL IN GOOD AGREEMENT THE FIRST HALF OF NEXT WEEK
AS A SHORTWAVE MOVES THROUGH THE MIDWEST INTO THE NORTHEAST, AND
ANOTHER SHORTWAVE ENTERS THE WEST. THE UKMET WAS SLOWER WITH THE
WESTERN FEATURE AND WAS NOT USED IN TONIGHT'S BLEND, ALTHOUGH THE
NEW 00Z RUN DID TREND FASTER. BY NEXT WEDNESDAY, THE TROUGH OVER
THE WEST WILL AMPLIFY AND THERE IS QUITE A BIT OF UNCERTAINTY ON
STREAM SEPARATIONS AND AMPLIFICATION ACROSS THE SOUTHEAST LATE
WEEK. THERE SEEMS TO BE BETTER SUPPORT FOR A MORE PROGRESSIVE
TROUGH INTO THE EAST, INCLUDING THE ENSEMBLE MEANS, BUT SOME
GUIDANCE, LIKE THE ECMWF CONTINUES TO SHOW A CUT OFF CLOSED LOW
LIFTING FROM THE SOUTHEAST U.S. NEXT THURSDAY-FRIDAY. AT THIS TIME,
THIS SOLUTION IS A STRONG OUTLIER AND IS NOT PREFERRED. THE CMC
DOES SHOW SOME AMPLIFICATION OF THE SOUTHERN STREAM AS WELL, BUT
NOT NEARLY TO THE DEGREE OF THE ECMWF. THE WPC FORECAST TRENDED
MORE TOWARDS THE PROGRESSIVE AND LESS SEPARATED GFS AND CMC, ALONG
WITH THE ENSEMBLE MEANS FOR THE SECOND HALF OF THE PERIOD.
..WEATHER/HAZARDS HIGHLIGHTS
A COLD FRONT INTO THE OHIO VALLEY AND EAST MONDAY-TUESDAY SHOULD
BE ACCOMPANIED BY SOME MODEST PRECIPITATION. THERE IS POTENTIAL FOR
HEAVIER RAIN AND 1+ INCH TOTALS IN SPOTS, BUT GIVEN THE
PROGRESSIVE NATURE OF THE FRONT AND RELATIVELY DRY ANTECEDENT
CONDITIONS, IT DOES NOT APPEAR AT THIS POINT TO WARRANT EVEN A
MARGINAL RISK ON THE DAY 4 (MONDAY) EXCESSIVE RAINFALL OUTLOOK.
HOWEVER, SOME RAINFALL EXPECTED IN THE SHORT TERM MAY TEMPER THE
INITIAL DRYNESS AND IMPROVED CLUSTERING TOWARD HEAVIER RAINFALL
WOULD INCREASE THE POTENTIAL FOR RUNOFF ISSUES.
THE NORTHERN HALF OF THE WEST COAST SHOULD SEE ANOTHER EPISODE OF
RAIN AND HIGHER ELEVATION SNOW ON MONDAY, WITH MOISTURE EXTENDING
EAST THROUGH THE ROCKIES BY TUESDAY. DETAILS OF THE SURFACE PATTERN
AND CORRESPONDING PRECIPITATION COVERAGE AND AMOUNTS OVER THE
CENTRAL/EASTERN U.S. BECOME INCREASINGLY UNCERTAIN BY NEXT MID NEXT
WEEK, BUT THERE IS SOME SIGNAL FOR ANOTHER ROUND OF MODERATE TO
HEAVY RAINFALL FROM THE MID-SOUTH INTO THE EAST, WITH SOME WINTRY
WEATHER POSSIBLE ON THE NORTH SIDE OF WHEREVER THE LOW PRESSURE
ACTUALLY TRACKS.
WITHIN AN INITIAL GENERALLY MILD PATTERN ACROSS THE LOWER 48,
WARMEST ANOMALIES SHOULD EXTEND FROM THE EASTERN SLOPES OF THE
ROCKIES TO THE EAST. 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-EAST WITH SOME BELOW NORMAL READINGS
POSSIBLE ACROSS THE NORTHERN PLAINS AS ARCTIC HIGH PRESSURE NUDGES
INTO THE REGION. OUT WEST, EXPECT TEMPERATURES TO TREND WARMER
UNDERNEATH PERSISTENT AMPLIFIED RIDGING.
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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