326
FXUS02 KWBC 100700
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
159 AM EST 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
THE MEDIUM RANGE PERIOD STARTS WEDNESDAY WITH A WEAK SHORTWAVE
MOVING THROUGH THE MID-MISSISSIPPI VALLEY AS ANOTHER ONE AMPLIFIES
OVER THE WEST. BY THURSDAY, THE PATTERN WILL TREND MUCH MORE
AMPLIFIED WITH UPPER RIDGING BUILDING OVER THE EAST ALLOWING FOR
THE TROUGH OVER THE WEST TO DIG SOUTHWARD INTO THE SOUTHWEST.
GUIDANCE HAS BEEN VERY CONSISTENT FOR A FEW DAYS NOW SHOWING 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
MODEL GUIDANCE CONTINUES TO SHOW GENERAL AGREEMENT ON THE LARGER
SCALE PATTERN THROUGH NEXT WEEKEND, WITH SOME TYPICAL DIFFERENCES
IN THE DETAILS THAT TEND TO INCREASE WITH LEAD TIME. EXACT
PLACEMENT DIFFERENCES WITH THE UPPER LOW OVER THE SOUTHWEST BECOME
MORE APPARENT WITH TIME, BUT THERE IS GOOD AGREEMENT IT SHOULD
LINGER OR VERY SLOWLY DRIFT SOUTHWARD ACROSS THE SOUTHWEST/FAR
NORTHERN BAJA. THE GREATEST REGION OF UNCERTAINTY TONIGHT WAS
ACROSS FROM THE NORTHERN PLAINS INTO THE UPPER MIDWEST/GREAT LAKES
AS A NORTHERN STREAM SYSTEM DROPPING SOUTH OUT OF CANADA AMPLIFIES
NEXT WEEKEND. THE CMC WAS THE BIGGEST OUTLIER SUGGESTING A MUCH
WEAKER INITIAL SHORTWAVE BECOMING MORE DOMINANT AND A COMPACT
CLOSED LOW OVER THE NORTHERN PLAINS AS EARLY AS FRIDAY. THE REST
OF THE GUIDANCE (WITH SUPPORT FROM THE AI MODELS AND ENSEMBLE
MEANS) SHOW A SECOND SHORTWAVE AND CLOSED LOW DEVELOPMENT NEAR THE
UPPER LAKES NOT UNTIL SATURDAY. THERE HAS BEEN A TREND TOWARDS
LESS SEPARATION BETWEEN THIS 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.
THE WPC BLEND FOR TONIGHT USED A BLEND OF THE DETERMINISTIC
SOLUTIONS 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.
GENERALLY, THIS MAINTAINED GOOD CONTINUITY WITH THE PREVIOUS WPC
FORECAST AS WELL.
..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. SNOW SHOULD CONTINUE INTO THE HIGHER ELEVATIONS OF NEW
MEXICO FROM THE LATTER PART OF THE WEEK. FARTHER EAST, RAINFALL
WILL BEGIN TO INCREASE IN COVERAGE AND INTENSITY OVER
NORTH-CENTRAL PARTS OF THE PLAINS AND MISSISSIPPI VALLEY BY
WEDNESDAY AS TROUGHING AMPLIFIES OVER THE WEST. THERE IS SOME
ANOMALOUS MOISTURE/INSTABILITY PRESENT ACROSS THE REGION ALONG A
FRONTAL BOUNDARY, BUT OVERALL QPF IS NOT TOO IMPRESSIVE AND
ANTECEDENT CONDITIONS ARE QUITE DRY, SO ANY EXCESSIVE RAINFALL
THREAT THERE LOOKS TO BE AT SUB-MARGINAL LEVELS. ON WEDNESDAY,
CONSIDERABLE CONVECTION IS LIKELY OVER THE GULF OF MEXICO, WHICH
MAY SNEAK INTO THE WEST COAST OF FLORIDA BY WEDNESDAY, BUT MODEL
DIFFERENCES IN AMOUNTS AND PLACEMENT PRECLUDE ANY AREA IN THE
EXCESSIVE RAINFALL OUTLOOK AT THIS POINT. BY THURSDAY, MOISTURE
STREAMING AHEAD OF THE CLOSED LOW DEVELOPING OVER THE SOUTHWEST
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 ERO ACROSS THE ARKLATEX 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.
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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