507
FXUS02 KWBC 081850
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
150 PM EST FRI MAR 08 2024
VALID 12Z MON MAR 11 2024 - 12Z FRI MAR 15 2024
...STRONG STORM EXITING THE NORTHEAST ON MONDAY WILL CONTINUE A
THREAT FOR HIGH WINDS...
...UNSETTLED WEATHER ALONG THE NORTHERN-CENTRAL WEST COAST WILL
CONTINUE INTO EARLY NEXT WEEK...
..HEAVY RAINFALL POTENTIAL RETURNS TO THE SOUTH LATE NEXT WEEK
..OVERVIEW
A STRONG LOW PRESSURE SYSTEM WILL BE EXITING THE NORTHEAST BY THE
START OF THE PERIOD ON MONDAY, BUT THE THREAT FOR HIGH WINDS WILL
CONTINUE ON THE BACKSIDE OF THIS SYSTEM AT LEAST THROUGH MONDAY.
MEANWHILE, A COUPLE OF SHORTWAVES WILL MOVE THROUGH THE WEST
MONDAY-WEDNESDAY, BRINGING SOME UNSETTLED CONDITIONS ACROSS MUCH
OF THE REGION BEFORE A STRONG UPPER RIDGE BUILDS OVER THE COAST
NEXT THURSDAY-FRIDAY. THIS SHOULD ALLOW FOR AMPLIFICATION OF THE
SYSTEM OVER THE WEST LATE WEEK, WITH GUIDANCE ALL SUGGESTING AN
EVENTUAL DEEP UPPER CLOSED LOW OVER THE SOUTHWEST/FOUR CORNERS
REGION. THIS WOULD SUPPORT A POSSIBLY HEAVY RAINFALL THREAT BY
NEXT THURSDAY AND FRIDAY ACROSS PARTS OF SOUTHERN PLAINS/LOWER
MISSISSIPPI VALLEY. A MEAN UPPER RIDGE SHIFTING FROM THE CENTRAL
TO EASTERN U.S. NEXT WEEK WILL BRING AN EXPANDING AREA OF ABOVE
NORMAL TEMPERATURES, WITH THE GREATEST ANOMALIES LIKELY TO BE OVER
THE NORTHERN PLAINS/UPPER MIDWEST EARLY-MID WEEK.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODEL GUIDANCE CONTINUES TO SHOW GOOD AGREEMENT ON THE UPPER LEVEL
PATTERN THROUGH THE MEDIUM RANGE PERIOD, WITH A TYPICAL AMOUNT OF
SPREAD IN FORECAST DETAILS. ALL OPERATIONAL MODELS AGREE THAT
THERE WILL BE A DEEP UPPER LOW EXITING THE NORTHEAST WHILE A FEW
SHORTWAVES MOVE INTO THE WEST, THEN THE PATTERN WILL AMPLIFY LATER
IN THE WEEK, FORMING A DEEP UPPER LOW OVER THE SOUTHWEST AND A
STRONG RIDGE OVER THE NORTHERN WEST COAST. THE LARGEST UNCERTAINTY
IN THE FORECAST IS CONCERNING SHORTWAVE ENERGY THAT MOVES INTO THE
WEST EARLY IN THE PERIOD AND THEN TRANSITS THROUGH THE MEAN RIDGE
OVER THE EASTERN U.S. MID-WEEK. AGREEMENT HAS IMPROVED SINCE
YESTERDAY, BUT THERE ARE STILL CONSIDERABLE DIFFERENCES IN TIMING
AND LOCATION OF THIS FEATURE, WHICH STEM FROM SUBTLE DIFFERENCES
IN THE UPSTREAM AMPLIFICATION. THE LATEST TREND IN GUIDANCE HAS
BEEN TO PULL THE WAVE FURTHER NORTH OVER THE GREAT LAKES REGION
WHILE A TRAILING FRONTAL SYSTEM MOVES ACROSS THE CENTRAL U.S. AND
MIDWEST. EVEN WITH HIGH UNCERTAINTY, THE EFFECT ON SENSIBLE
WEATHER SHOULD BE MINIMAL SINCE THIS RELATIVELY WEAK WAVE SHOULD
ONLY PRODUCE LIGHT PRECIPITATION.
LATE IN THE MEDIUM RANGE PERIOD, MODEL GUIDANCE HAS BEEN SHOWING A
POTENT SHORTWAVE MOVING THROUGH THE DEEP TROUGH OVER THE SOUTHWEST
AND EJECTING ACROSS THE SOUTHERN U.S. LATE THURSDAY INTO FRIDAY.
ALL AVAILABLE MODEL GUIDANCE IS SHOWING AN AREA OF HEAVY
PRECIPITATION IN THE SOUTH THURSDAY NIGHT INTO FRIDAY AND SHIFTING
INTO THE SOUTHEAST LATE ON FRIDAY. MOST GUIDANCE IS SHOWING MAX
QPF VALUES OF 3-5 INCHES SOMEWHERE IN THE SOUTH, BUT THERE IS A
HIGH AMOUNT OF UNCERTAINTY CONCERNING THE EXACT LOCATION OF THE
HEAVIEST TOTALS, WHICH WILL BE BETTER RESOLVED AS WE GET CLOSER TO
THE EVENT. IF THIS FORECAST HOLDS AND MODELS MAINTAIN HIGH QPF
VALUES, THIS SYSTEM COULD POSE A THREAT FOR FLASH FLOODING.
SINCE MODELS ARE IN GOOD AGREEMENT, WPC USED A GENERAL
DETERMINISTIC BLEND FOR THE FIRST HALF OF THE PERIOD, AND
GRADUALLY ADDED ENSEMBLE MEANS TO SMOOTH OUT MINOR FORECAST
DIFFERENCES IN THE SECOND HALF OF THE PERIOD.
..WEATHER/HAZARDS HIGHLIGHTS
AS THE STRONG SURFACE LOW EXITS THE NORTHEAST, MUCH OF THE
PRECIPITATION WILL BE WELL OFFSHORE BY MONDAY, WITH THE EXCEPTION
OF SOME LIGHT TO MODERATE SNOW SHOWERS CONTINUING INTO THE DAY
ACROSS MAINE AND THE HIGHER TERRAIN ON THE BACKSIDE OF THE LOW.
GUSTY TO HIGH WINDS WILL ALSO CONTINUE INTO MONDAY AND MAYBE
TUESDAY ACROSS MUCH OF THE NORTHEAST. BEHIND THIS, WEATHER ACROSS
THE EASTERN AND CENTRAL U.S. SHOULD TREND QUIETER FOR THE FIRST
HALF OF THE WEEK, BUT THE WESTERN U.S. REMAINS UNSETTLED AS A
COUPLE OF SHORTWAVES BRING ROUNDS OF RAIN AND HIGHER ELEVATION
SNOW. THE DAY 4/MONDAY EXCESSIVE RAINFALL OUTLOOK HIGHLIGHTS A
MARGINAL RISK ALONG THE COAST FROM NORTHERN CALIFORNIA THROUGH
WASHINGTON. GUIDANCE CONTINUES TO SHOW SOME UNCERTAINTY FOR
DETAILS OF MAGNITUDE/DISTRIBUTION OF MOISTURE AND HIGHER RAIN
TOTALS, BUT WET GROUND CONDITIONS FOLLOWING HEAVY RAIN THE PRIOR
DAY (SUNDAY) MAY LOWER THE THRESHOLD FOR LOCALIZED RUNOFF ISSUES
IN SOME AREAS THAT SEE OVERLAPPING HEAVY RAIN/HIGH RATES.
AS THE FINAL UPPER SHORTWAVE IN THE SERIES AMPLIFIES AND MOVES
INLAND, THE BEST FOCUS FOR RAIN AND MOUNTAIN SNOW SHOULD SHIFT
INTO THE CENTRAL ROCKIES BY WEDNESDAY, WITH RAINFALL BEGINNING TO
INCREASE IN COVERAGE AND INTENSITY OVER THE PLAINS AND MISSISSIPPI
VALLEY AS WELL. MOISTURE STREAMING AHEAD OF A CLOSED LOW
DEVELOPING OVER THE SOUTHWEST SHOULD INCREASE THE THREAT FOR
ANOTHER ROUND OF HEAVY RAIN AND POTENTIALLY FLASH FLOODING ACROSS
THE LOWER MISSISSIPPI VALLEY AND VICINITY NEXT THURSDAY SHIFTING
MORE INTO THE GULF COAST/SOUTHEAST BY NEXT FRIDAY. AREAS IN THE
MID-SOUTH MAY BE MORE SUSCEPTIBLE TO FLOODING WITH THIS SYSTEM
CONSIDERING THE HEAVY RAINFALL FORECAST FOR THIS REGION IN THE
SHORT RANGE PERIOD. SOME THREAT FOR LOCALLY HEAVY RAIN/MOUNTAIN
SNOWS WILL EXIST ACROSS THE SOUTHWEST AS WELL IN ASSOCIATION WITH
THIS SYSTEM.
MEAN RIDGING ALOFT OVER THE CENTRAL/EAST-CENTRAL U.S. WILL SUPPORT
AN EXPANDING AREA OF ABOVE NORMAL TEMPERATURES TO THE EAST OF THE
ROCKIES. THE CORE OF WARMEST ANOMALIES SHOULD COVER PARTS OF THE
NORTHERN PLAINS AND UPPER MIDWEST MONDAY THROUGH WEDNESDAY, WITH
HIGHS POTENTIALLY REACHING 20-30 DEGREES ABOVE NORMAL. ABOVE
NORMAL TEMPERATURES WILL GRADUALLY EXPAND INTO THE SOUTH AND EAST
MID TO LATE NEXT WEEK WEEK. OVER THE WEST, THE WET/SNOWY PATTERN
OVER NORTHERN-CENTRAL WEST COAST AND EVENTUALLY INTO THE ROCKIES
WILL MAINTAIN MODERATELY BELOW AVERAGE HIGHS AND NEAR/ABOVE
AVERAGE LOWS THROUGH EARLY NEXT WEEK. UPPER TROUGHING THAT
AMPLIFIES INLAND BY WEDNESDAY-THURSDAY SHOULD SPREAD A BROADER
AREA OF COOL DAYTIME HIGHS ACROSS THE WEST WITH TEMPERATURES
BEGINNING TO REBOUND AGAIN ALONG THE IMMEDIATE COAST NEXT FRIDAY
AS STRONG RIDGING BUILDS IN ALOFT.
DOLAN/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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