Prognostic Meteorological Discussion
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000
FXUS02 KWBC 250654
PMDEPD

EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
254 AM EDT WED APR 25 2018

VALID 12Z SAT APR 28 2018 - 12Z WED MAY 02 2018

TREND TOWARD WESTERN TROUGHING AND EASTERN RIDGING WILL BE
UNDERWAY BY THE WEEKEND AS AN UPPER LOW SLIDES INTO NORTHERN
CALIFORNIA AND A TROUGH IN THE EAST STARTS TO LIFT OUT. THE
MODELS/ENSEMBLES HAVE COME INTO A BIT BETTER AGREEMENT BUT THE
GFS/GEFS REMAIN QUICKER AND TO THE NORTH OF THE ECMWF/CMC/UKMET
CONSENSUS IN THE WEST, AND WAS GIVEN ONLY A SMALL MINORITY
WEIGHTING. THE 00Z ECMWF ENSEMBLE MEAN OFFERED THE MOST REASONABLE
FORECAST (SEVERAL DAYS RUNNING NOW) INTO THE START OF NEXT WEEK.
DESPITE THE DIFFERENCES IN THE DAYS 3-5 TIME FRAME, THERE BECOMES
RATHER REMARKABLE AGREEMENT BY NEXT TUE/WED WITH A TRAILING
SHORTWAVE TUGGING BACK THE TROUGH AXIS INTO THE SOUTHWEST STATES
AS THE LEAD FORMER UPPER LOW WEAKENS THROUGH THE HIGH PLAINS.
ENSEMBLE AGREEMENT IS STRONG IN A RATHER AMPLIFIED TROUGH/RIDGE
PATTERN THAT WILL BRING MUCH ABOVE AVERAGE TEMPERATURES TO THE
EAST FOR THE FIRST COUPLE DAYS OF MAY. THE WEST WILL SEE UNSETTLED
WEATHER WITH MOSTLY LIGHT TO MODERATE RAIN AND HIGH ELEVATION SNOW
BUT LOWERING SNOW LEVELS WITH TIME AS HEIGHTS FALL AND COOLER
TEMPERATURES FILTER IN. AREAS TO THE NORTH OF THE UPPER LOW TRACK
(OREGON TO IDAHO TO MONTANA) STAND TO SEE THE MOST PRECIPITATION
THIS WEEKEND INTO EARLY NEXT WEEK. HIGH PRESSURE TO THE EAST WILL
ALLOW MOISTURE TO FLOW NORTHWARD FROM THE WESTERN GULF THROUGH THE
SOUTHERN PLAINS WHERE CONVECTION WILL BE LIKELY ONCE THE FRONT
GETS EAST OF THE FOOTHILLS. THE EAST WILL THEN DRY OUT NEXT WEEK
WITH HARDLY ANY PRECIPITATION EAST OF ABOUT I-65 (INDIANA TO
ALABAMA).


FRACASSO


ASSOCIATED WPC MEDIUM RANGE FORECASTS OF 500 MB HEIGHTS...SURFACE
SYSTEMS...WEATHER GRIDS...QUANTITATIVE PRECIPITATION FORECASTS
(QPF)...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


$$





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