Preliminary Forecasts
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000
FXUS02 KWNH 240703
PREEPD

PRELIMINARY EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
302 AM EDT TUE APR 24 2018

VALID 12Z FRI APR 27 2018 - 12Z TUE MAY 01 2018

...OVERVIEW AND GUIDANCE PREFERENCES...

UPPER PATTERN WILL TRANSITION IN THE MEDIUM RANGE PERIOD TO
WESTERN TROUGHING AND EASTERN RIDGING, BUT HOW IT GETS THERE
REMAINS OBFUSCATED IN ENSEMBLE RECALCITRANCE. THE GFS/GEFS REMAIN
OVERALL QUICKER WITH THE FLOW RIGHT FROM ~36HRS IN THE EAST AND
~48HRS OFF THE WEST COAST, AND AGAIN WAS NOT PREFERRED. THE UKMET
HAS TRENDED MORE TOWARD THE ONGOING PREFERENCE IN THE WEST BUT
STILL INSISTS ON PUSHING THE UPPER LOW WELL NORTH OF THE MULTI-DAY
CONSENSUS, LEAVING THE 12Z ECMWF/CANADIAN (AND ECMWF ENSEMBLE
MEAN) AS THE CHOICES OF LEAST REGRET OVER THE LOWER 48. THIS
ALLOWS FOR A SLOWER PROGRESSION OF THE UPPER LOW INTO NORTHERN
CALIFORNIA/NEVADA BEFORE WEAKENING AS HEIGHT FALLS SINK SOUTHWARD
ALONG THE BC/WA COAST SUN/MON, TUGGING THE TROUGH AXIS BACK TO THE
SOUTHWEST BY NEXT TUESDAY. BY THAT POINT, THE GFS/GEFS INTRODUCED
ANOTHER TROUGH FROM THE NORTH PACIFIC INTO THE WEST AT THE SAME
TIME AS THE ECMWF/CANADIAN, GIVING THE APPEARANCE OF AGREEMENT.
EITHER WAY, HEIGHTS ARE FORECAST TO RISE IN THE EAST NEXT WEEK
DOWNSTREAM OF THIS TROUGH.


...WEATHER/THREATS HIGHLIGHTS...

MILD TEMPERATURES INITIALLY IN THE WEST LATE THIS WEEK WILL SLIDE
EASTWARD INTO THE PLAINS BY SUNDAY AND INTO THE NORTHEAST NEXT
TUESDAY. 70S WILL BE FAIRLY WIDESPREAD BY NEXT TUESDAY FROM THE
OHIO VALLEY INTO PARTS OF NEW ENGLAND. CONVERSELY, THE WEST WILL
TREND COOLER WITH TIME AS THE UPPER TROUGH SETTLES IN, WITH
WIDESPREAD RAIN AND SOME HIGH MOUNTAIN SNOW TO WA/OR/ID/MT AND
ACROSS NORTHERN CA/NV/UT. FARTHER EAST, RETURN FLOW FROM THE
WESTERN GULF SHOULD BE SUFFICIENT TO SUPPORT MOSTLY
LIGHT/SCATTERED RAIN OVER THE SOUTHERN ROCKIES INTO THE HIGH
PLAINS BY THE WEEKEND/NEXT MONDAY. AREAS THAT STAND TO SEE THE
MOST PRECIPITATION LIE ACROSS SOUTHERN OREGON INTO SOUTHERN
CENTRAL MONTANA JUST TO THE NORTH OF THE UPPER LOW`S TRACK.

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


FRACASSO


$$





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