351
FXUS02 KWBC 101903
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
303 PM EDT SUN MAR 10 2024
VALID 12Z WED MAR 13 2024 - 12Z SUN MAR 17 2024
..HEAVY RAINFALL POTENTIAL RETURNS TO THE SOUTH LATE NEXT WEEK
..OVERVIEW
A WEAK SHORTWAVE WILL BE MOVING THROUGH THE MID-MISSISSIPPI VALLEY
WEDNESDAY WHILE THE NEXT ONE AMPLIFIES OVER THE WESTERN STATES.
THE GENERAL FLOW ACROSS THE CONTIGUOUS STATES WILL TRANSITION TO
BEING MORE AMPLIFIED WITH UPPER RIDGING BUILDING OVER THE EAST
ALLOWING FOR THE TROUGH OVER THE WEST TO DIG SOUTHWARD INTO THE
SOUTHWEST. A DEEP CLOSED LOW DEVELOPING OVER THE SOUTHWEST/FOUR
CORNERS REGION ON THURSDAY, AND LINGERING INTO THE WEEKEND. THIS
WOULD PROMOTE A MULTI-DAY PERIOD OF HEAVY RAINFALL POTENTIAL
ACROSS PARTS OF THE SOUTHERN U.S. LATE THIS WEEK. ELSEWHERE,
NORTHERN STREAM ENERGY WILL AMPLIFY ACROSS THE UPPER MIDWEST/GREAT
LAKES NEXT WEEKEND, AS A STRONG RIDGE SHIFTS OVER THE WEST COAST.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE LATEST SUITE OF GUIDANCE DEPICT A GROWING SIGNAL FOR A DEEP,
CLOSED LOW TO DEVELOP ACROSS THE SOUTHWEST AND EXIT INTO THE
PLAINS AS THE WEEK PROGRESSES. SOME OF THE DETAILS REGARDING THIS
FEATURE VARY FROM ONE MODEL TO THE NEXT HOWEVER CONSENSUS SUGGESTS
IT SHOULD LINGER OR VERY SLOWLY DRIFT SOUTHWARD ACROSS THE
SOUTHWEST/FAR NORTHERN BAJA. THERE HAS BEEN A TREND TOWARDS LESS
SEPARATION BETWEEN THE NORTHERN STREAM AND THE SOUTHWEST UPPER
LOW, SHOWING THE NORTHERN STREAM SYSTEM FURTHER
DEEPENING/AMPLIFYING OVER THE MIDWEST/OHIO VALLEY NEXT SUNDAY AS
THE UPPER LOW MEANDERS/IS CUT OFF OVER THE SOUTHWEST/FAR NORTHERN
MEXICO AND A BLOCKY RIDGE OVER THE WEST COAST. WPC MAINTAINED A
SIMILAR FORECAST APPROACH AS THE PREVIOUS FOR CONTINUITY. THE WPC
BLEND UTILIZED 06/00Z GFS AND 00Z CMC/ECWMF/UKMET FOR THE DAYS
3-4, WITH A MAJORITY WEIGHTING TOWARDS THE GFS AND THE ECMWF. BY
DAY 5, REPLACED THE CMC AND THE UKMET (WHICH PHASES OFF AFTER DAY
5 ANYWAYS) WITH THE ENSEMBLE MEANS AND GRADUALLY INCREASED THEIR
INFLUENCE THROUGH DAY 7. THIS HELPS TO MITIGATE SOME OF THE LOW
CONFIDENCE SMALLER SCALE DETAILS LATE PERIOD.
..WEATHER/HAZARDS HIGHLIGHTS
EARLY WEEK PRECIPITATION OVER THE NORTHWEST WILL SHIFT INTO THE
ROCKIES BY WEDNESDAY, WITH POTENTIALLY HEAVY SNOWFALL ACROSS PARTS
OF THE COLORADO ROCKIES INTO THURSDAY, AND MORE UNCERTAIN
POTENTIAL FOR SNOWFALL ACROSS THE FRONT RANGE URBAN CORRIDOR AS
WELL. ACROSS THE HIGHER ELEVATIONS OF NEW MEXICO SNOW IS
ANTICIPATED TO PERSIST LATER IN THE WEEK. RAINFALL IS EXPECTED TO
BEGIN ACROSS PORTIONS OF THE NORTHERN/CENTRAL PLAINS AND THE
MISSISSIPPI VALLEY BY WEDNESDAY AS THE WESTERN TROUGH AMPLIFIES.
ALTHOUGH THERE WILL BE AMPLE MOISTURE AND INSTABILITY IN PROXIMITY
TO THE FRONTAL FOR EFFICIENT RAINFALL TO DEVELOP, THE RISK FOR
EXCESSIVE RAINFALL WILL MORE THAN LIKELY BE LESS THAN MARGINAL
GIVEN RECENT DRIER CONDITIONS. THE AREAL COVERAGE OF CONVECTION
WILL GREATLY INCREASE ACROSS THE GULF AND SURROUNDING LOCATIONS,
WHICH WILL HELP INCREASE SOIL MOISTURE ACROSS THE SOUTH. A SURGE
IN MOISTURE AHEAD OF THE APPROACHING LOW BY THURSDAY WILL BOLSTER
QPF RATES AND AMOUNTS OVER A VAST AREA AND SHOULD INCREASE THE
THREAT FOR HEAVY RAIN AND POTENTIALLY FLASH FLOODING ACROSS THE
LOWER MISSISSIPPI VALLEY/GULF COAST/SOUTHEAST. THERE IS STILL
PLENTY OF UNCERTAINTY IN EXACT PLACEMENT OF THE HEAVIEST RAINS,
BUT THERE IS SUPPORT IN THE DYNAMICS AND AREAL QPF COVERAGE TO
INTRODUCE A FAIRLY BROAD SLIGHT RISK AREA ON THE DAY 5/THURSDAY
EXCESSIVE RAINFALL OUTLOOK ACROSS ARKANSAS, LOUISIANA AND TEXAS
REGION INTO NORTHWEST MISSISSIPPI. THE HEAVY RAINFALL THREAT MAY
SHIFT SLIGHTLY EASTWARD MORE INTO THE GULF COAST STATES/SOUTHEAST
FRIDAY AND SATURDAY, WITH A LIKELY FLASH FLOOD THREAT GIVEN RECENT
HEAVY RAINS IN THIS REGION. SEVERE WEATHER IS ALSO A THREAT WITH
THIS CONVECTIVE ACTIVITY PER THE STORM PREDICTION CENTER WITH A
SEVERE WEATHER AREA DELINEATED FOR PARTS OF THE SOUTHERN PLAINS ON
THURSDAY.
MEAN RIDGING ALOFT OVER THE EAST-CENTRAL AND EASTERN U.S. WILL
SUPPORT AN EXPANSIVE AREA OF ABOVE NORMAL TEMPERATURES TO THE EAST
OF THE ROCKIES. THE CORE OF WARMEST ANOMALIES SHOULD COVER PARTS
OF THE UPPER MIDWEST AND UPPER GREAT LAKES ON WEDNESDAY, WITH
HIGHS POTENTIALLY REACHING 20-30 DEGREES ABOVE NORMAL.
TEMPERATURES WILL TREND WARMER INTO THE SOUTH AND EAST MID TO LATE
NEXT WEEK AS WELL WITH DAYTIME HIGHS WELL INTO THE 70S TO NEAR 80
FOR SOME. OVER THE WEST, MODERATELY BELOW AVERAGE HIGHS AND
NEAR/ABOVE AVERAGE LOWS WILL SHIFT FROM THE NORTHWEST ON WEDNESDAY
INTO THE GREAT BASIN/FOUR CORNERS THURSDAY AND BEYOND.
TEMPERATURES ALONG THE IMMEDIATE WEST COAST SHOULD BEGIN TO
REBOUND AGAIN BY NEXT FRIDAY-SATURDAY AS STRONG RIDGING BUILDS IN
ALOFT.
CAMPBELL/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, EXCESSIVE RAINFALL OUTLOOK,
WINTER WEATHER OUTLOOK PROBABILITIES, HEAT INDICES AND KEY
MESSAGES 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
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
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