072
FXUS02 KWBC 221856 AAC
PMDEPD
EXTENDED FORECAST DISCUSSION...UPDATED
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
256 PM EDT FRI MAR 22 2024
VALID 12Z MON MAR 25 2024 - 12Z FRI MAR 29 2024
...HEAVY SNOW LIKELY TO CONTINUE INTO MONDAY FOR PARTS OF THE
NORTH-CENTRAL PLAINS AND UPPER MIDWEST...
...HEAVY RAIN THREAT ACROSS THE LOWER MISSISSIPPI VALLEY TO
SOUTHEAST EARLY TO MIDWEEK...
..OVERVIEW
A STRONG LOW PRESSURE SYSTEM FORECAST TO INTENSIFY AND TRACK
ACROSS THE CENTRAL PLAINS TO THE UPPER MIDWEST MONDAY-TUESDAY
SHOULD BRING HEAVY SNOW TO THE NORTH-CENTRAL U.S., NORTH AND WEST
OF THE LOW TRACK. EXPECT STRONG WINDS AND VERY COLD TEMPERATURES
WITH THIS SYSTEM AS WELL. ON THE WARM SIDE OF THE SYSTEM, HEAVY
RAIN ASSOCIATED WITH STRONG THUNDERSTORMS AHEAD OF A RELATIVELY
POTENT COLD FRONT WILL LIKELY LEAD TO FLOODING ISSUES ACROSS THE
LOWER MISSISSIPPI VALLEY AND SOUTHEAST MONDAY-TUESDAY, WITH SOME
UNCERTAINTY BEYOND THAT IN HOW MUCH RAIN MAY FALL ALONG THE EAST
COAST. MEANWHILE, ONE OR MORE PACIFIC SYSTEMS SHOULD BRING
INCREASING TOTALS OF RAIN AND MOUNTAIN SNOW TO THE NORTHWEST AND
THEN INTO THE ROCKIES MID-LATE WEEK. SOME OF THIS MOISTURE MAY
REACH THE NORTHERN PLAINS BY NEXT FRIDAY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
LATEST GUIDANCE SHOWS BETTER THAN AVERAGE CLUSTERING FOR THE STRONG
PLAINS THROUGH UPPER MIDWEST STORM DURING THE FIRST HALF OF THE
WEEK. THERE ARE STILL SOME DETAIL QUESTIONS ALONG AND AHEAD OF
THIS STORM'S COLD FRONT, WITH ONE OR MORE POSSIBLE LOW-
PREDICTABILITY WAVES FOR WHICH MOST GUIDANCE SHOWS A REASONABLE
SIGNAL IN PRINCIPLE. AS THE OVERALL UPPER TROUGH CONTINUES EASTWARD
LATER IN THE WEEK, THE PRIMARY FORECAST PROBLEM IS HOW MUCH FLOW
SEPARATION MAY OCCUR AND AT WHAT LONGITUDE--AFFECTING SURFACE LOW
POSITION AND DEPTH. ECMWF RUNS HAVE BEEN SHOWING MORE SEPARATION
AND FARTHER WESTWARD POSITION, WITH ECENS RUNS UNDERSTANDABLY LESS
SEPARATED ALOFT BUT LIKEWISE SOMEWHAT WEST. 00Z ECMWF/06Z GFS-GEFS
RUNS HAVE ATTEMPTED SOME CONVERGENCE THOUGH, WITH THE ECMWF
SHIFTING A LITTLE EAST AND GFS/GEFS SOMEWHAT WEST. 00Z ECMWF-
INITIALIZED MACHINE LEARNING (ML) MODELS SHOW SOME SCATTER WITH
THEIR MEAN APPEARING TO SUPPORT A SOLUTION CLOSE TO AN AVERAGE
AMONG THE 06Z GFS/GEFS AND 00Z ECMWF/ECENS. THE 00Z CMC BECOMES A
SLOW EXTREME AFTER MIDWEEK, NOT JUST OVER THE EAST BUT FOR THE REST
OF THE LOWER 48 AND VICINITY AS WELL.
FARTHER WEST, THE 00Z UKMET WAS INITIALLY THE ODD MODEL OUT WITH A
MORE SUPPRESSED PACIFIC LOW TRACK BY WEDNESDAY. BY NEXT FRIDAY
RECENT GFS RUNS HAVE LEANED A LITTLE SOUTH WITH THE NEXT POTENTIAL
SYSTEM NEARING THE PACIFIC NORTHWEST. WHILE THERE IS DECENT
MODEL/ENSEMBLE CLUSTERING FOR THIS FRIDAY SYSTEM, THERE IS MORE
DIVERSITY AMONG THE ML MODELS FOR WHAT THE UPPER DETAILS WILL LOOK
LIKE AND HOW THEY WILL REFLECT AT THE SURFACE. THEREFORE WILL
MONITOR THE POTENTIAL FOR ADJUSTMENTS IN THE DYNAMICAL GUIDANCE.
BASED ON THE COMPARISONS AMONG LATEST GUIDANCE, THE FIRST PART OF
THE UPDATED FORECAST STARTED WITH MOSTLY THE 06Z GFS/00Z ECMWF WITH
A LITTLE 00Z CMC. THEN THE FORECAST PHASED OUT THE CMC WHILE
INCREASING 06Z GEFS/00Z ECENS INPUT TO 60 PERCENT BY LATE IN THE
PERIOD.
..WEATHER/HAZARDS HIGHLIGHTS
THE DEEP SURFACE LOW TRACKING FROM THE CENTRAL PLAINS TO UPPER
MIDWEST (AND ITS UPPER LEVEL SUPPORT) WILL PRODUCE AN IMPACTFUL
MULTI-HAZARD WEATHER EVENT FOR EARLY-MID NEXT WEEK. A WIDESPREAD
LATE SEASON WINTER STORM SHOULD BE ONGOING MONDAY WITH HEAVY SNOW
ACCUMULATION (8+") LIKELY FROM NORTHEASTERN NEBRASKA INTO EASTERN
PARTS OF THE DAKOTAS, MUCH OF MINNESOTA, AND FAR NORTHWESTERN
WISCONSIN, AS THIS REGION WILL BE ON THE COLDER SIDE OF THE LOW
WITH A DEFORMATION ZONE DEVELOPING. HIGH WINDS DUE TO THE DEEP
SURFACE LOW COULD LEAD TO BLIZZARD CONDITIONS IN SOME AREAS.
TIMING/TRACK UNCERTAINTY MAY CHANGE THE EVENTUAL LOCATION OF THE
IMPACTFUL WINTER WEATHER, BUT THE RISK FOR DISRUPTIONS TO DAILY
LIFE AND HAZARDOUS TRAVEL IS LIKELY. HIGH WINDS ARE ALSO POSSIBLE
SOUTHWARD ACROSS THE PLAINS ON MONDAY BEHIND THE COLD FRONT, THOUGH
WITH DRIER WEATHER.
FARTHER SOUTH AHEAD OF THE COLD FRONT, AMPLE MOISTURE STREAMING IN
AND A STRONG JET ALOFT WILL SUPPORT HEAVY RAIN AND POTENTIALLY
SEVERE THUNDERSTORMS FOR THE LOWER MISSISSIPPI VALLEY MONDAY,
SHIFTING INTO THE SOUTHEAST ON TUESDAY. SLIGHT RISK AREAS ARE IN
PLACE IN THE DAYS 4-5 EXCESSIVE RAINFALL OUTLOOKS DUE TO THE
POTENTIAL OF A LIKELY SQUALL LINE CAUSING RAIN RATES OF 2+" PER
HOUR. MOST GUIDANCE SUGGESTS THE AREAL COVERAGE OF HEAVY QPF AND
LOCALIZED MAXIMA SHOULD BE SOMEWHAT LOWER ON TUESDAY COMPARED TO
MONDAY, BUT STILL HAVE A SLIGHT RISK GIVEN SUFFICIENT GUIDANCE
SIGNAL THAT THE SQUALL LINE WILL LIKELY LAST INTO TUESDAY OVER
MISSISSIPPI/ALABAMA, WITH SIGNIFICANT RAINFALL POSSIBLY EXTENDING
INTO PARTS OF TENNESSEE AS WELL. LATEST GUIDANCE THEMES FAVORED A
LITTLE EASTWARD/NORTHEASTWARD EXPANSION OF THIS DAY 5 SLIGHT RISK
AREA FOR THE AFTERNOON UPDATE. BY MID-LATE WEEK, THE STORMY
WEATHER CROSSES THE FLORIDA PANHANDLE NORTH INTO THE CAROLINAS AND
EVENTUALLY UP THE EASTERN SEABOARD, BUT WITH CONSIDERABLE
UNCERTAINTY IN RAINFALL COVERAGE/AMOUNTS FROM THE MID-ATLANTIC
NORTHWARD AFTER MIDWEEK.
SOME LINGERING MODERATE SNOW IS POSSIBLE ACROSS PARTS OF THE
SOUTH-CENTRAL ROCKIES ON MONDAY, WITH LIGHT AMOUNTS ELSEWHERE
ACROSS THE INTERMOUNTAIN WEST. THE PACIFIC NORTHWEST COULD SEE SOME
MODERATE LOWER ELEVATION RAIN AND HIGHER ELEVATION SNOW AMOUNTS
MONDAY, WITH INCREASING TOTALS BY TUESDAY-WEDNESDAY AND EXPANDING
INTO CALIFORNIA AS UPPER TROUGHING AND LOW PRESSURE APPROACH. SOME
MODERATE TO HEAVY PRECIPITATION SHOULD EXPAND INTO THE
INTERMOUNTAIN WEST BY MID-LATE WEEK, AND WILL CONTINUE TO MONITOR
THE POTENTIAL FOR FURTHER EXPANSION OF THE PRECIPITATION POSSIBLY
IN THE FORM OF SNOW TO AFFECT THE NORTH-CENTRAL PLAINS ONCE AGAIN
BY THURSDAY OR FRIDAY.
MUCH COLDER THAN AVERAGE TEMPERATURES (MORE COMPARABLE TO JANUARY)
ARE LIKELY FOR THE NORTHERN AND CENTRAL HIGH PLAINS IN THE WAKE OF
THE STRONG PLAINS/MIDWEST STORM. HIGHS WILL ONLY BE IN THE 20S AND
30S FOR THESE AREAS ON MONDAY. THE CENTRAL U.S. WILL SEE A WARMING
TREND GOING INTO THE MIDDLE AND LATE PART OF NEXT WEEK, THOUGH
MONTANA AND THE DAKOTAS WILL STILL REMAIN CHILLY BY LATE MARCH
STANDARDS. THE WEST SHOULD SEE GENERALLY COOLER THAN AVERAGE HIGHS
AND NEAR AVERAGE LOWS NEXT WEEK. MEANWHILE THE EAST SHOULD SEE A
WARMING TREND EARLY-MID WEEK AHEAD OF THE MIDWEST STORM'S COLD
FRONT AND THEN NEAR TO SLIGHTLY BELOW AVERAGE TEMPERATURES
CENTRAL/SOUTH AFTER FRONTAL PASSAGE. THE NORTHEAST MAY REMAIN A
LITTLE ABOVE AVERAGE, ESPECIALLY FOR MORNING LOWS.
RAUSCH/TATE
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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