095
FXUS02 KWBC 081900
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 PM EDT THU MAY 8 2025
VALID 12Z SUN MAY 11 2025 - 12Z THU MAY 15 2025
..MULTI-DAY SOUTHEAST U.S. HEAVY RAINFALL/FLOODING THREAT
..OVERVIEW
THE MAIN WEATHER HEADLINE REMAINS GENERALLY THE SAME WITH A CLOSED
LOW MEANDERING OVER THE LOWER MISSISSIPPI VALLEY/SOUTHEAST FOR
SEVERAL DAYS BEFORE FINALLY LIFTING OUT OF THE REGION AROUND NEXT
MIDWEEK. THIS WILL SUPPORT DEEPLY POOLED MOISTURE TO FUEL DAILY
AND LOCALLY HEAVY RAINFALL/CONVECTIVE THREATS INTO NEXT WEEK OVER
THE SOUTHEAST INCLUDING FLORIDA, WITH THE SPREADING OF HEAVY RAINS
UP THROUGH THE MID-ATLANTIC TO FAVORED TERRAIN OF THE APPALACHIANS
WITH SLOW SYSTEM EJECTION INTO NEXT THURSDAY. AMPLIFIED UPPER
TROUGHING AND SURFACE LOW GENESIS OFF THE WEST COAST WILL MOVE
INLAND BY SUNDAY, WITH WIDESPREAD ENHANCED PRECIPITATION EXTENDING
ACROSS THE WEST/NORTHWEST WELL INTO NEXT WEEK, INCLUDING MOUNTAIN
SPRING SNOWS FROM THE SIERRA TO THE NORTHERN ROCKIES. THIS LOOKS TO
EVENTUALLY SPIN UP A SURFACE LOW PRESSURE SYSTEM OVER THE NORTH-
CENTRAL U.S. BY THE MIDDLE OF NEXT WEEK, WITH MODERATE TO HEAVY
WRAPPING RAIN POTENTIAL AROUND THE LOW ACROSS THE NORTHERN PLAINS.
..GUIDANCE/PREDICTABILITY ASSESSMENT
LATEST MODEL AND ENSEMBLE GUIDANCE SEEMS REASONABLY WELL CLUSTERED
THROUGH MED-RANGE TIME SCALES AND A COMPOSITE SOLUTION SEEMS TO
PROVIDE A SOLID FORECAST BASIS.
..WEATHER/HAZARDS HIGHLIGHTS
A WAVY FRONTAL SYSTEM AND A CLOSED UPPER LOW MEANDERING OVER THE
SOUTHEAST WILL SUPPORT A MULTI-DAY HEAVY RAINFALL AND FLOODING
THREAT THROUGH NEXT MIDWEEK AS FUELED BY THE POOLING OF HIGHLY
ANOMALOUS MOISTURE. GIVEN THE INCREASED SIGNAL FOR HEAVY RAINS BY
SUNDAY (AND SOME HEAVY RAINFALL POTENTIAL STARTING ON SATURDAY),
A SLIGHT RISK FOR NORTHERN FLORIDA AND SOUTHERN GEORGIA REMAINS
DEPICTED ON THE WPC DAY 4 EXCESSIVE RAINFALL OUTLOOK (ERO). BY
MONDAY, THIS POTENTIAL EXPANDS SOUTHWARD INTO THE FLORIDA PENINSULA
AND NORTHWARD ACROSS MUCH OF THE SOUTHEAST AS STORMS MAY TRAIN
ALONG A SLOW MOVING COLD FRONT LIFTING THROUGH THE REGION. AS SUCH,
A SLIGHT RISK IS INCLUDED FOR MUCH OF THE SOUTHEAST ON THE DAY 5
ERO AS WELL. PROTRACTED ENHANCED RAINFALL SHOULD GRADUALLY LIFT
NORTHWARD WITH TIME INCREASING ACROSS THE MID-ATLANTIC AND UP THE
APPALACHIANS NEXT TUESDAY-THURSDAY BEFORE FINALLY LOSING INFLUENCE.
OUT WEST, RAIN AND HIGHER ELEVATIONS SNOWS WILL BECOME MORE
WIDESPREAD THROUGH THE WEEKEND AND INTO NEXT WEEK WITH MAIN
AMPLIFIED SYSTEM COOLING AND SLOW PROGRESSION INLAND THROUGH EARLY
AND MID NEXT WEEK. MODEST SNOWS ARE POSSIBLE IN THE HIGHER TERRAIN.
AS THE SYSTEM PROGRESSES EAST, MODERATE TO HEAVY RAINFALL MAY
DEVELOP ON THE NORTH AND WEST SIDE OF A SURFACE LOW OVER THE NORTH-
CENTRAL PLAINS.
UPPER TROUGHING OVER THE SOUTH WILL KEEP POST-FRONTAL TEMPERATURES
BELOW NORMAL THROUGH EARLY NEXT WEEK, ESPECIALLY DAYTIME MAXES
GIVEN WIDESPREAD AND PROTRACTED RAIN/CLOUD POTENTIAL AROUND THE
UPPER LOW. UPPER RIDGING FROM THE SOUTHWEST TO THE PLAINS WILL
SUPPORT MUCH ABOVE NORMAL TEMPERATURES ACROSS MUCH OF THE
INTERMOUNTAIN WEST AND NORTHERN U.S., WITH DAYTIME HIGHS 20-30
DEGREES ABOVE NORMAL POSSIBLE IN THE NORTHERN PLAINS WHERE RECORD
VALUES ARE IN REACH. PARTS OF THE SOUTHWEST SHOULD EXCEED 100
DEGREES WITH AT LEAST SOME LOCALIZED HEAT THREAT GIVEN EARLIER IN
THE SEASON TIMING SUNDAY AND MONDAY. ABOVE NORMAL HEAT WILL
MODERATE SOME AS IT PROGRESSES ACROSS THE REST OF THE PLAINS AND
INTO THE MIDWEST AND EAST NEXT WEEK. UPPER TROUGHING AND FRONTAL
SURGE OVER MUCH OF THE WEST WILL DROP AND MAINTAIN TEMPERATURES
BELOW NORMAL TUESDAY-NEXT THURSDAY IN UNSETTLED FLOW.
SANTORELLI/SCHICHTEL
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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