910
FXUS02 KWBC 271856
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
156 PM EST THU FEB 27 2025
VALID 12Z SUN MAR 02 2025 - 12Z THU MAR 06 2025
...SEVERE WEATHER AND HEAVY RAIN POTENTIAL LIKELY TO FOCUS IN
LOWER/MIDDLE MISSISSIPPI VALLEY AND MID-SOUTH ON TUESDAY AND
PERHAPS THE EAST ON WEDNESDAY...
..OVERVIEW
THE MEDIUM RANGE PERIOD WILL FEATURE A RATHER PROGRESSIVE UPPER
FLOW PATTERN ACROSS THE LOWER 48 STATES AS A COUPLE OF TROUGHS
TRAVERSE COAST TO COAST. WHILE TROUGHING EXITS THE EAST EARLY WEEK,
A SOUTHERN STREAM CUTOFF LOW OVER THE SOUTHERN HIGH PLAINS ON
SUNDAY WILL LIFT NORTH AND EAST AND GET ABSORBED INTO THE LARGER
SCALE FLOW INTO EARLY NEXT WEEK OVER THE SOUTH-CENTRAL U.S.
MEANWHILE UPSTREAM, A DEEP TROUGH/CLOSED LOW WILL MOVE INTO THE
WEST SUNDAY/MONDAY, SPREADING SOME MODEST PRECIPITATION AND WINDS
ACROSS THE REGION. AS THIS SYSTEM EMERGES, REASONABLY DEEP LOW
PRESSURE SYSTEM WILL FORM OVER THE CENTRAL PLAINS BY TUESDAY AND
TRACK NORTHEAST WEDNESDAY-THURSDAY. AHEAD OF ITS ASSOCIATED COLD
FRONT, SEVERE WEATHER AND HEAVY RAIN WITH FLOODING POTENTIAL ARE
POSSIBLE ACROSS THE SOUTH-CENTRAL INTO EAST-CENTRAL U.S. PEAKING ON
TUESDAY, WITH SOME PERHAPS CONTINUING INTO WEDNESDAY IN THE EAST.
ANOTHER AMPLIFIED TROUGH APPROACHES THE WEST COAST NEXT THURSDAY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MOST MODEL AND ENSEMBLE GUIDANCE IS REASONABLY AGREEABLE WITH THE
FIRST FEW SYSTEMS OF NOTE DURING THE MEDIUM RANGE PERIOD, NAMELY
WITH THE EAST TROUGH PULLING AWAY, THE SOUTHERN ROCKIES/HIGH PLAINS
SMALL SOUTHERN STREAM LOW GETTING ABSORBED, AND THE TROUGH MOVING
FROM THE EASTERN PACIFIC INTO THE WEST. WHILE SMALLER SCALE
DIFFERENCES EXIST, AND COULD IMPACT SENSIBLE WEATHER LIKE QPF, A
MULTI-MODEL BLEND OF DETERMINISTIC GUIDANCE COULD BE USED AS A
STARTING POINT, PARTICULARLY THE 00Z ECMWF, 00Z/06Z GFS, AND 00Z
CMC. THE MAIN OUTLIER WAS THE 00Z UKMET, WHICH WAS FARTHER
INLAND/FASTER WITH THE WEST TROUGH COMPARED TO OTHER GUIDANCE, SO
LEANED AWAY FROM THAT. THAT INITIALLY WEST TROUGH MAINTAINS
REASONABLE MODEL AGREEMENT FOR THE MID-LATE MEDIUM RANGE PERIOD AS
IT SHIFTS INTO THE PLAINS AND BEYOND AND CAUSES A SURFACE LOW TO
DEVELOP AND TRACK NORTHEAST.
THE UPPER TROUGH TRACKING TOWARD THE WEST BY MID-LATE WEEK SHOWS
MORE VARIABILITY IN MODEL GUIDANCE. OPERATIONAL GFS RUNS FROM
00Z/06Z AND NOW 12Z HAVE HELD THE UPPER LOW FARTHER BACK INTO THE
PACIFIC COMPARED TO OTHER GUIDANCE--INCLUDING THE GFS-BASED AI
MODELS THAT SHOWED A TROUGH AXIS FARTHER EAST. THIS GAVE CONFIDENCE
TO NOT PREFER THE DETERMINISTIC GFS SOLUTIONS. MEANWHILE THE ECMWF
RUNS ARE SLIGHTLY ON THE FASTER SIDE OF THE ENVELOPE. EC-BASED AI
MODELS ARE MIXED WITH SOME FASTER AND SOME SLOWER. THE ENSEMBLE
MEANS WERE RATHER AGREEABLE AND SHOWED AN IN BETWEEN SOLUTION (MORE
TOWARD THE EC THAN THE GFS THOUGH). THUS THE WPC FORECAST QUICKLY
RAMPED UP THE PROPORTION OF THE ENSEMBLE MEANS BY DAY 6 AND
ESPECIALLY 7 TO COMBAT THE INCREASING SPREAD WITH THE WEST TROUGH
IN PARTICULAR.
..WEATHER/HAZARDS HIGHLIGHTS
THE INITIAL SOUTHERN STREAM UPPER LOW MOVING INTO THE SOUTHERN
PLAINS ON SUNDAY COULD LEAD TO SOME MODEST RAINFALL ACROSS THAT
REGION. BEHIND IT, SOME HIGH WINDS ARE POSSIBLE ACROSS THE SOUTHERN
ROCKIES TO HIGH PLAINS. THE TROUGH COMING INTO THE WESTERN U.S.
EARLY NEXT WEEK WILL ALSO LEAD TO SOME PRECIPITATION SPREADING
ACROSS THE WEST COAST INTO THE GREAT BASIN AND ROCKIES, WITH LOWER
ELEVATION RAIN AND HIGHER ELEVATION SNOW AS WELL AS GUSTY WINDS. A
TRUE ATMOSPHERIC RIVER IS NOT EXPECTED AND THIS SHOULD LIMIT
PRECIPITATION TOTALS TO BE MODEST IN MOST AREAS. HOWEVER, AS THIS
TROUGH MOVES INTO THE CENTRAL U.S. BY TUESDAY, IT SHOULD TAP
MOISTURE FROM THE GULF TO FUEL MORE WIDESPREAD AND HEAVY RAINS FROM
THE SOUTHERN TO EASTERN U.S. THE HEAVIEST RAINFALL TOTALS ARE
CURRENTLY EXPECTED FROM THE LOWER/MIDDLE MISSISSIPPI VALLEY TO
SOUTHEAST AND TENNESSEE/OHIO VALLEYS ON TUESDAY. SOME AREAS HAVE
WET ANTECEDENT SOIL CONDITIONS, WHICH WOULD EXACERBATE FLOOD
POTENTIAL. SEVERE WEATHER IS ALSO A NOTABLE THREAT OVER THE SOUTH-
CENTRAL STATES PER SPC. PRECIPITATION SHOULD OVERSPREAD THE EAST ON
WEDNESDAY, AND SPC CONTINUES TO SHOW SEVERE POTENTIAL IN THE
SOUTHEAST TO SOUTHERN MID-ATLANTIC. AREAS OF HEAVY RAINFALL BECOME
EVEN MORE UNCERTAIN WITH PLACEMENT AT THAT TIME, BUT MAY BECOME
PROBLEMATIC IN TERMS OF FLOODING IF HEAVY RAIN FALLS ON SNOW-
COVERED AREAS OF THE NORTHEAST, PER THE NATIONAL WATER CENTER.
NORTHWEST OF THE LOW TRACK, IT MAY BE COLD ENOUGH TO SUPPORT SNOW
ACROSS THE NORTH-CENTRAL PLAINS INTO THE GREAT LAKES, BUT TOTALS
ARE UNCERTAIN. GUSTY WINDS ARE ALSO POSSIBLE DEPENDING ON HOW DEEP
THE SURFACE LOW GETS. ANOTHER ROUND OF MODERATE RAIN AND ELEVATION
SNOW SHOULD MOVE INTO CALIFORNIA WEDNESDAY-THURSDAY WITH THE NEXT
UPPER TROUGH.
MUCH ABOVE NORMAL TEMPERATURES OVER THE ROCKIES AND PLAINS STATES
ON SUNDAY WILL GRADUALLY PROGRESS EASTWARD WITH TIME AND MODERATE.
THE GREATEST ANOMALIES, 15 TO 25 DEGREES ABOVE NORMAL, WILL BE
ACROSS THE NORTHERN PLAINS THROUGH MONDAY. TEMPERATURES ACROSS MUCH
OF THE EAST WILL BE CONSIDERABLY COLDER THAN NORMAL ON SUNDAY, BUT
SHOULD MODERATE BACK TO NORMAL MONDAY-TUESDAY, AND WARMER THAN
NORMAL WEDNESDAY. BY NEXT THURSDAY, MUCH OF THE COUNTRY MAY BE NEAR
OR WITHIN A FEW DEGREES OF NORMAL.
TATE/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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