Prognostic Meteorological Discussion
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FXAK02 KWNH 242028
PMDAK

ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
427 PM EDT MON APR 24 2017

VALID 12Z FRI APR 28 2017 - 12Z TUE MAY 02 2017

THE MOST PERSISTENT AND CONSISTENT FEATURE FOR THE MEDIUM RANGE
PERIOD FOR AK IS THE UPPER RIDGE EXTENDING FROM NORTHWEST/YUKON
TERRITORIES INTO AK. WHAT REMAINS UNCERTAIN DURING THE FORECAST
PERIOD IS A COUPLE OF PAC SYSTEMS THAT UNDERCUT UNDERNEATH THE
RIDGE FROM THE ALEUTIANS INTO THE GULF OF AK/NERN PAC. THE FIRST
SHORT WAVE SYSTEM WITH POTENTIAL CLOSED MID TO UPPER LOW NEAR THE
ALEUTIANS INTO THE BERING SEA ON FRI WILL SHEAR OFF TO THE SOUTH
AND EAST AND MESH WITH A PAC SYSTEM TO STREAM INTO BRITISH
COLUMBIA SAT/SUN. THE NEXT LARGE LOW PRESSURE SYSTEM WILL SLIDE
FROM RUSSIA THROUGH THE BERING SEA AND REACH THE ALEUTIAN CHAIN.
THIS IS BASED ON THE GEFS/ECMWF/NAEFS MEANS, AS THE OPERATIONAL
GUIDANCE SHOWS CONSIDERABLE SPREAD AND RUN TO RUN INCONSISTENCIES.
WPC STARTED OFF WITH A LARGE PERCENTAGE OF THE BLEND BASED ON
OPERATIONAL GUIDANCE BUT BY NEXT MON AND TUES, THIS SHIFTS TOWARD
ALL MEANS.

GEFS AND ECMWF MEAN STANDARDIZED ANOMALIES FOR 850 MB TEMPS
SUGGEST TEMPS BEING SLIGHTLY ABOVE AVG, .5 TO 1 DEVIATION ABOVE
AVG. MEANWHILE PRECIPITATION AMOUNTS WILL MOSTLY BE CONCENTRATED
ACROSS THE SRN TIER OF THE STATE, ESPECIALLY THE ALEUTIAN CHAIN
AND PANHANDLE AREA.

MUSHER

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