401
FXUS02 KWBC 160654
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
254 AM EDT SAT MAR 16 2024
VALID 12Z TUE MAR 19 2024 - 12Z SAT MAR 23 2024
..GENERAL OVERVIEW
AN AMPLIFIED UPPER LEVEL PATTERN IS EXPECTED TO BE IN PLACE ACROSS
THE CONTINENTAL U.S. FOR THE BEGINNING OF NEXT WEEK, FEATURING A
DEEP UPPER TROUGH ACROSS THE EASTERN U.S., AND A REX BLOCK OVER
THE WESTERN U.S. WITH A CLOSED UPPER HIGH OVER THE PACIFIC
NORTHWEST AND A LOITERING UPPER LOW OVER THE DESERT SOUTHWEST. THE
TROUGH OVER THE EAST SLOWLY LIFTS OUT SOME BY MIDWEEK WITH MORE
BROAD CYCLONIC FLOW ALOFT. THE SOUTHWEST UPPER LOW EVOLVES INTO AN
OPEN WAVE AND THEN EJECTS EASTWARD ACROSS THE SOUTHERN PLAINS
GOING INTO THURSDAY, AND REACHING THE SOUTHEAST U.S. BY NEXT
SATURDAY WITH A POTENTIAL NOR'EASTER DEVELOPING. THE UPPER RIDGE
BREAKING DOWN ACROSS THE NORTHWESTERN U.S. WILL ALLOW FOR A PACIFIC
TROUGH TO MOVE IN WITH A RETURN TO RAIN AND MOUNTAIN SNOW BY FRIDAY
AND INTO SATURDAY.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE 00Z GUIDANCE SUITE REMAINS IN REASONABLE AGREEMENT WITH THE
FLOW PATTERN INTO EARLY NEXT WEEK, WITH SOME UNCERTAINTY IN THE
DETAILS AND TIMING OF INDIVIDUAL SHORTWAVES ACROSS THE EASTERN U.S.
WITHIN THE LARGER SCALE UPPER TROUGH. GREATER MODEL UNCERTAINTIES
ARE INTRODUCED WHEN THE REX BLOCK BREAKS DOWN ACROSS THE WESTERN
U.S. AND A TROUGH FROM THE EASTERN PACIFIC EVENTUALLY DEVELOPS NEAR
THE WEST COAST. THIS RESULTS IN BELOW AVERAGE CONFIDENCE ACROSS THE
NORTHERN TIER OF THE U.S. AS SHORTWAVE PERTURBATIONS TRACK
EASTWARD IN NORTHERN STREAM FLOW. CONFIDENCE IS BETTER ACROSS THE
SOUTHERN TIER OF THE U.S. WITH THE UPPER TROUGH EJECTING FROM THE
DESERT SOUTHWEST ACROSS THE SOUTHERN PLAINS, EVEN THOUGH THERE ARE
SOME TIMING DIFFERENCES WITH THE ECMWF DEPICTING A FASTER SOLUTION,
AND THE CMC SLOWER, AND THE GFS BETWEEN THESE SOLUTIONS.
THE WPC FORECAST INCORPORATED A GENERAL DETERMINISTIC MODEL BLEND
FOR TUESDAY AND WEDNESDAY, WITH MORE WEIGHTING APPLIED TO THE GFS
AND ECMWF. AFTER THAT, THERE WAS A GRADUAL INCREASE IN THE USE OF
THE ENSEMBLE MEANS TO ABOUT 50-60 PERCENT OF THE BLEND BY NEXT
SATURDAY, ALONG WITH SOME OF THE GFS AND ECMWF AND SOME PREVIOUS
WPC CONTINUITY THROUGH FRIDAY.
..WEATHER/HAZARDS HIGHLIGHTS
AFTER MULTIPLE DAYS OF HEAVY RAINFALL ACROSS THE GULF COAST REGION
THIS WEEKEND, THERE WILL BE A WELCOMED ABATEMENT IN BOTH RAINFALL
COVERAGE AND INTENSITY GOING INTO EARLY-MID NEXT WEEK. THERE WILL
NOT BE MUCH IN THE WAY OF ORGANIZED RAINFALL ON TUESDAY ACROSS THE
CONTINENTAL U.S., EXCEPT FOR SOME AREAS OF LIGHT RAIN ACROSS
PORTIONS OF TEXAS AND THE FOUR CORNERS REGION. GOING INTO
WEDNESDAY, THERE MAY BE ENOUGH RETURN FLOW AND INSTABILITY FROM
THE WESTERN GULF TO FUEL A GREATER COVERAGE OF SHOWERS AND
THUNDERSTORMS ACROSS SOUTHERN TEXAS, BUT CURRENTLY BELOW THE
THRESHOLD OF NEEDING A MARGINAL RISK AREA AT THIS TIME.
TO THE NORTH, A SECONDARY COLD FRONT COMBINED WITH AN UPPER LEVEL
DISTURBANCE CROSSING THE GREAT LAKES/NORTHEAST SHOULD BRING SOME
GENERALLY LIGHT PRECIPITATION ACROSS THE REGION. SUFFICIENT COLD
AIR AND LOW LEVEL MOISTURE MAY COMBINE TO PRODUCE SOME ACCUMULATING
SNOWS FOR PORTIONS OF THE CENTRAL APPALACHIANS AND DOWNSTREAM OF
LAKE ERIE AND LAKE ONTARIO ON TUESDAY. LOOKING AHEAD TO THE END OF
THE WEEK, SHOWERS AND THUNDERSTORMS ARE EXPECTED TO INCREASE IN
COVERAGE ACROSS THE GULF COAST REGION AS GULF MOISTURE ADVECTS
NORTHWARD AHEAD OF A DEVELOPING SURFACE LOW, WITH THE GREATEST
RAINFALL LIKELY REMAINING OFFSHORE OVER THE NORTHERN GULF BASED ON
LATEST MODEL TRENDS. THERE IS ALSO INCREASING MODEL SIGNAL FOR A
POTENTIAL NOR'EASTER TO DEVELOP OFF THE COAST OF NORTH CAROLINA BY
EARLY SATURDAY AS THE GULF LOW CROSSES FLORIDA, AND IF THIS COMES
TO PASS, HEAVY RAIN AND GUSTY WINDS COULD DEVELOP FOR COASTAL
PORTIONS OF THE CAROLINAS. SNOW WILL LIKELY MAKE A RETURN TO THE
NORTHERN ROCKIES LATE IN THE WEEK AS WELL.
TEMPERATURES ACROSS THE EAST COAST ARE FORECAST TO BE UP TO 10 DEGREES
BELOW AVERAGE ON TUESDAY AS A CANADIAN SURFACE HIGH WILL BE IN
PLACE. THERE WILL LIKELY BE SOME FROST/FREEZE CONCERNS FOR ANY
AREAS WHERE SPRING GREEN-UP HAS STARTED AS TEMPERATURES DIP WELL
INTO THE 30S TO NEAR FREEZING, ESPECIALLY TUESDAY MORNING ACROSS
MUCH OF THE SOUTHEAST STATES. MEANWHILE, IT WILL BE PLEASANTLY
MILD FROM THE PACIFIC NORTHWEST TO THE CENTRAL PLAINS THROUGH
MIDWEEK, FOLLOWED BY A GRADUAL COOLING TREND TO CLOSE OUT THE WORK
WEEK. IT WILL REMAIN COLD ACROSS NORTH DAKOTA AND INTO NORTHERN
MINNESOTA WITH HIGHS IN THE 20S AND LOW 30S FOR THE END OF THE
WEEK.
HAMRICK
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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