EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
225 AM EDT SAT APR 21 2018

VALID 12Z TUE APR 24 2018 - 12Z SAT APR 28 2018

...OVERVIEW AND GUIDANCE PREFERENCES...

TROUGHING WILL BE REINFORCED IN THE EASTERN THIRD/HALF OF THE
LOWER 48 NEXT WEEK WHILE RIDGING OVER THE WEST HOLDS AN UPPER LOW
OFF THE COAST. THE MODELS HAVE STRUGGLED WITH THE TRACK OF THE
UPPER LOW AND NORTHERN STREAM FLOW OUT OF CANADA BUT SEEM TO BE
HONING IN ON A BETTER CONSENSUS COMPARED TO 24 HRS AGO. THIS WOULD
KEEP THE UPPER LOW OFF THE CALIFORNIA COAST THROUGH THE WEEK UNTIL
NEXT WEEKEND WHEN IT MAY LIFT NORTHEASTWARD TOWARD THE CA/OR
BORDER. A BLEND OF THE RECENT GUIDANCE OFFERED A GOOD STARTING
POINT DESPITE SOME DIFFERENCES IN STRENGTH/TIMING OF A FEW OF THE
EASTERN SYSTEMS IN THE LONGWAVE TROUGH PATTERN. COULD NOT
NECESSARILY RULE ANY ONE RUN OUT GIVEN THE MULTI-DAY SHUFFLINGS.


...WEATHER/THREATS HIGHLIGHTS...

EXITING LEAD UPPER/SFC LOW WILL SPREAD MODEST RAINS THROUGH THE
MID-ATLANTIC EARLY IN THE PERIOD WITH GENERALLY LIGHTER AMOUNTS
INTO NEW ENGLAND AS THE LOW RIDES UP I-95 INTO MAINE ON THURSDAY.
TRAILING SYSTEMS WILL SPREAD LIGHT RAIN OR MAYBE SOME WET SNOW
THROUGH THE GREAT LAKES AS WEAKER SHORTWAVES SLIP SOUTHEASTWARD IN
THE BROAD CYCLONIC FLOW. TEMPERATURES WILL BE BELOW AVERAGE WITH
THE EXCEPTION OF MAINE.

IN THE WEST, UPPER RIDGING WILL ENSURE WELL ABOVE AVERAGE
TEMPERATURES (+10 TO +20F ABOVE CLIMO) WITH SOME RECORDS POSSIBLE.
PRECIPITATION MAY HOLD OFFSHORE UNTIL NEXT WEEKEND (OR AT LEAST
LATE FRIDAY) WITH THE ENSEMBLE CONSENSUS MOSTLY INTO COASTAL
OREGON BUT ALSO INTO THE SIERRAS AS THE COLD FRONT SHOULD FINALLY
COME ASHORE.

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