257
FXUS02 KWNH 030716
PREEPD
PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
315 AM EDT THU MAY 3 2018
VALID 12Z SUN MAY 6 2018 - 12Z THU MAY 10 2018
..PATTERN OVERVIEW
THE FORECAST PERIOD BEGINS ON SUNDAY WITH A BROAD UPPER LEVEL
TROUGH OVER EASTERN NORTH AMERICA, A RIDGE OVER THE INTERMOUNTAIN
WEST, AND A SMALLER SCALE TROUGH NEAR THE WEST COAST. THE FLOW
PATTERN BECOMES QUASI-ZONAL ACROSS MOST OF THE CONTINENTAL U.S.
GOING INTO THE FIRST HALF OF NEXT WEEK AS THE EASTERN U.S. TROUGH
LIFTS OUT SOME AND THE WESTERN U.S. RIDGE BECOMES LESS AMPLIFIED
WITH TIME. THE FASTER FLOW ALOFT SHOULD BE MOSTLY RELEGATED TO
CANADA AS THE POLAR JET STREAM LIFTS NORTH. BY THE END OF THE
FORECAST PERIOD WEDNESDAY NIGHT, A STRONGER TROUGH IS LIKELY TO
AFFECT THE WESTERN U.S.
..GUIDANCE AND UNCERTAINTY ASSESSMENT
MODEL GUIDANCE IS IN RELATIVELY DECENT AGREEMENT AT THE BEGINNING
OF THE FORECAST PERIOD. HOWEVER, GIVEN THE LOWER AMPLITUDE FLOW
ALOFT, THE TIMING AND MAGNITUDE OF INDIVIDUAL SHORTWAVE
DISTURBANCES AND SURFACE LOWS BECOMES LESS CERTAIN GOING INTO
EARLY NEXT WEEK. THE CMC BECOMES MORE AMPLIFIED WITH A TROUGH
OVER THE SOUTHEAST U.S. AND OVER THE NORTHERN PLAINS BY TUESDAY.
THE ECMWF IS STRONGER WITH THE NEXT PACIFIC STORM SYSTEM REACHING
THE WEST COAST BY THE MIDDLE OF THE WEEK, WITH THE GFS TRACKING IT
FARTHER NORTH. THE WPC FORECAST WAS BASED MAINLY ON THE
DETERMINISTIC GFS/ECMWF/UKMET ALONG WITH SOME PREVIOUS WPC
CONTINUITY THROUGH TUESDAY, AND THEN INCREASING PERCENTAGES OF THE
EC AND NAEFS MEANS FOR THE FINAL TWO DAYS.
..SENSIBLE WEATHER
SHOWERS AND STORMS ARE LIKELY FOR PORTIONS OF THE EAST COAST FOR
SUNDAY WITH THE FRONTAL BOUNDARY SLOWLY EXITING THE COAST. THE
HEAVIEST RAINFALL APPEARS LIKELY OFFSHORE FOR NOW, BUT ANY TREND
FARTHER TO THE WEST WILL NEED TO BE MONITORED. THE OTHER AREA
THAT WILL HAVE INCREASED CHANCES FOR RAIN AND THUNDERSTORM
ACTIVITY WILL BE THE NORTHERN PLAINS TO THE UPPER MIDWEST TOWARDS
THE MIDDLE OF NEXT WEEK AS A SURFACE LOW DEVELOPS AND TRACKS
ACROSS THE REGION. ELSEWHERE, PRECIPITATION APPEARS TO BE
ISOLATED TO SCATTERED AT BEST.
IN TERMS OF TEMPERATURES, EXPECT READINGS TO GENERALLY BE ABOVE
AVERAGE FOR THE PLAINS TO THE INTERMOUNTAIN WEST, INCLUDING THE
DESERT SOUTHWEST WHERE TRIPLE DIGIT HIGHS ARE LIKELY TO BE
REALIZED FOR THE LOWER ELEVATIONS. NEAR NORMAL TEMPERATURES ARE
EXPECTED TO RETURN TO THE EAST COAST REGION AFTER SEVERAL DAYS OF
UNSEASONABLY WARM CONDITIONS. SOME AREAS OF BELOW NORMAL
TEMPERATURES ARE LIKELY NEAR THE GREAT LAKES OWING TO THE TROUGH
OVER SOUTHEAST CANADA AND THE COLD LAKE TEMPERATURES.
D. HAMRICK
----------
ASSOCIATED WPC MEDIUM RANGE FORECASTS OF 500 MB HEIGHTS, SURFACE
SYSTEMS, WEATHER GRIDS, QUANTITATIVE PRECIPITATION FORECASTS, AND
WINTER WEATHER OUTLOOK SNOW/SLEET PROBABILITIES CAN BE FOUND AT...
HTTP://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF
HTTP://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF
HTTP://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML
HTTP://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML
HTTP://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page