748
FXUS02 KWBC 270719
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
319 AM EDT WED MAY 27 2026
VALID 12Z SAT MAY 30 2026 - 12Z WED JUN 03 2026
..HEAVY RAIN/THUNDERSTORMS FOR PARTS OF THE SOUTHERN U.S
..OVERVIEW
A BLOCKY UPPER FLOW PATTERN WILL BE IN PLACE TO START THE PERIOD
ON SATURDAY FEATURING TROUGHING OVER BOTH THE WEST AND EAST, WITH
RIDGING IN BETWEEN OVER THE CENTRAL U.S.. THE TROUGH OVER THE WEST
WILL WEAKEN AS IT LIFTS NORTHEASTWARD BRINGING HEAVY RAIN POTENTIAL
TO PARTS OF THE NORTHERN ROCKIES/HIGH PLAINS THIS WEEKEND. ANOTHER
SHORTWAVE WILL MOVE INTO THE PACIFIC NORTHWEST EARLY NEXT WEEK.
TROUGHING OVER THE EAST WILL BE REINFORCED THROUGH THE PERIOD, WITH
A FRONTAL BOUNDARY DRAPED ACROSS THE SOUTHERN EDGE OF IT ACROSS
THE SOUTH. THIS, COMBINED WITH FORCING FROM SOUTHERN STREAM ENERGY
IN THE REGION, WILL ALLOW FOR A GENERALLY CONTINUED WET PATTERN
ACROSS MUCH OF THE SOUTH WHERE THINGS HAVE BEEN VERY WET AS OF
LATE, AND WILL CONTINUE TO BE IN THE SHORT RANGE PERIOD AS WELL.
..GUIDANCE/PREDICTABILITY ASSESSMENT
MODELS SHOW GOOD AGREEMENT ON THE OVERALL LARGE SCALE PATTERN
EVOLUTION THROUGH THE PERIOD, BUT WITH PLENTY OF VARIABILITY IN THE
SMALLER SCALE DETAILS. OUT WEST, THE GUIDANCE SHOWS GOOD TIMING
CONSENSUS WITH THE UPPER LOW/TROUGH LIFTING NORTHEASTWARD OUT OF
THE GREAT BASIN BY THE WEEKEND, BUT A LOT OF UNCERTAINTY ON
SUBSEQUENT ENERGIES INTO THE OVERALL TROUGH. OVERALL THOUGH, THE
PATTERN SHOULD BECOME LESS AMPLIFIED OVER THIS REGION WITH TIME. IN
THE EAST, LOTS OF UNCERTAINTY STILL WITH A VARIETY OF SHORTWAVES
AS THEY DROP DOWN THE WESTERN SIDE OF THE TROUGH TO REINFORCE AND
DEEPEN MEAN TROUGHING OVER THE EAST. THERE IS SOME INDICATION IS
GUIDANCE FOR A POSSIBLE CUT OFF LOW OVER THE EAST BY THE MIDDLE OF
NEXT WEEK TOO, BUT PLENTY OF RUN TO RUN VARIABILITY ON THIS
EVOLUTION TO BUY INTO ANY ONE SOLUTION AT THIS POINT.
THE WPC FORECAST FOR TONIGHT USED A MAJORITY BLEND OF THE
DETERMINISTIC GUIDANCE FOR THE FIRST HALF OF THE PERIOD, INCREASING
WEIGHTING OF THE ENSEMBLES TO 60 PERCENT OF THE BLEND BY DAYS 6
AND 7 GIVEN INCREASING PATTERN VARIABILITY AND UNCERTAINTY.
..WEATHER/HAZARDS HIGHLIGHTS
IT GENERALLY REMAINS THE CASE THAT PERSISTENT SHORTWAVE ENERGIES
AND A COUPLE OF WAVY FRONTAL BOUNDARIES WILL CONTINUE TO KEEP MUCH
OF THE SOUTH ACTIVE AND UNSETTLED INTO THE WEEKEND WITHIN A MOIST
AND UNSTABLE ENVIRONMENT AND DAILY THUNDERSTORM CHANCES. COMBINED
WITH WHAT HAS ALREADY BEEN A WET PATTERN ACROSS THIS REGION,
ISOLATED FLOODING COULD BE A CONCERN. FOR DAY 4/SATURDAY, DID
MAINTAIN A MARGINAL RISK FOR PARTS OF THE SOUTHEAST ALONG THE
FRONTAL BOUNDARY. PREVIOUS MARGINAL RISKS FOR CENTRAL TEXAS AND
SOUTH FLORIDA WERE REMOVED FOR DAY 4 BECAUSE THE QPF SUPPORT SEEMED
TO HAVE DIMINISHED WITH RECENT MODEL RUNS. SHOWERS AND STORMS WILL
CONTINUE INTO SUNDAY AS WELL ACROSS THE SOUTHERN PLAINS AND GULF
COAST/FLORIDA, BUT A LACK OF APPRECIABLE QPF PRECLUDED ANY MARGINAL
RISK AREAS YET FOR THE DAY 5 ERO. HOWEVER, GIVEN HOW WET ITS BEEN
IN MANY AREAS ACROSS THE SOUTH, LOCALIZED FLOODING IS NOT OUT OF
THE QUESTION AND SO ITS POSSIBLE RISK AREAS MAY BE NEEDED IN FUTURE
UPDATES IF THE SIGNAL FOR HEAVY RAINFALL INCREASES.
TO THE NORTH OVER THE NORTHEAST, A VIGOROUS VORT MOVING THROUGH
LATE THIS WEEK MAY RESULT IN A PERIOD OF MODERATE TO HEAVIER
RAINFALL FOR PARTS OF NEW ENGLAND GIVEN WINDY OFFSHORE LOW GENESIS
WHICH MAY LAST INTO SATURDAY.
OUT WEST...UPPER TROUGHING LIFTING OUT OF THE GREAT BASIN WITH A
WAVY FRONTAL SYSTEM AHEAD OF IT WILL ALLOW FOR INCREASED
PRECIPITATION ACROSS THE INTERMOUNTAIN WEST FOR THE END OF THIS
WEEK. SNOW IS POSSIBLE ACROSS THE HIGHEST ELEVATIONS, THOUGH WITH
MINIMAL ACCUMULATION. THE SIGNAL FOR HEAVY RAINFALL HAS INCREASED
OVER PARTS OF WESTERN MONTANA AND VICINITY SO A MARGINAL RISK WAS
ADDED TO THE DAY 4/SATURDAY ERO TONIGHT. RAIN WILL CONTINUE INTO
SUNDAY, BUT WITH LESS INTENSITY, SO NO RISK AREAS ARE DEPICTED AT
THIS TIME FOR THIS REGION. RAINFALL CHANCES ALSO INCREASE THIS
WEEKEND AND INTO NEXT WEEK FOR PARTS OF THE NORTHERN AND CENTRAL
PLAINS AHEAD OF GENERAL WEAK TROUGHING OVER THE WEST.
WITH THE CLOSED UPPER LOW OVER THE WEST DURING THE SHORT RANGE
WORKING TO LIFT OUT BY THIS WEEKEND, BELOW NORMAL TEMPERATURES
SHOULD MODERATE BACK TOWARDS NORMAL. SOME RIDGING BUILDING BACK
INTO THE REGION LATE IN THE PERIOD MAY BRING TEMPERATURES ABOVE
AVERAGE BY THEN. THE UPPER RIDGE TO ITS EAST WILL ALLOW FOR WARMER
THAN AVERAGE TEMPERATURES ACROSS THE NORTH- CENTRAL U.S. THROUGH
MUCH OF NEXT WEEK, WITH DAYTIME HIGHS 10-20 DEGREES ABOVE NORMAL,
WITH GREATEST ANOMALIES EARLY IN THE PERIOD. PERSISTENT TROUGHING
OVER THE EAST MAY BRING SLIGHTLY BELOW NORMAL TEMPERATURES THROUGH
THE PERIOD, WHICH MAY EXTEND WESTWARD WITH TIME INTO THE SOUTHERN
PLAINS.
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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