ALASKA EXTENDED FORECAST DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 251 PM EDT MON MAR 17 2014 VALID 12Z FRI MAR 21 2014 - 12Z TUE MAR 25 2014 ...THE MEGABLOCK IS COMING... THE MUCH-ADVERTISED CONVOLUTION OF THE FLOW ASTRIDE THE ARCTIC CIRCLE IS SOLIDLY WITHIN THIS MEDIUM-RANGE PERIOD. BY THE TIME THE FEATURES SETTLE OUT SOMETIME NEXT WEEK, A SPRAWLING UPPER HIGH IS PROGGED TO EXTEND FROM CHUKOTKA TO THE BEAUFORT SEA, WITH AN ATTENDANT VORTEX CENTERED ALONG THE ALASKAN GULF COAST. THE EUROPEAN CENTRE GUIDANCE HAS HANDLED THIS TRANSITION MOST CONSISTENTLY--AND MOST SKILLFULLY--SO CONTINUE TO RELY UP IT FOR THE MANUAL PRODUCT SUITE. THE LAST IN A SERIES OF MOIST CYCLONES SHOULD PASS SOUTH OF THE PANHANDLE DAY 4, WITH A MARKED DRYING AND COOLING TREND THEREAFTER. COOLING IS PUTTING IT MILDLY. THE STRENGTH OF THE SURFACE HIGH DISLODGED BY THE BURGEONING BLOCK SHOULD BLAST SOME FRIGID AIR SOUTHWESTWARD THROUGH THAT REGION BY THE WEEKEND. MEANWHILE, THE INTERIOR MAINLAND WILL BE MARKED BY VERY LOW MOISTURE DAYS 4 THROUGH 8, WITH 12-HOUR POPS NOT REACHING EVEN 5% ALONG THE ARCTIC COAST. THE BERING SEA AND WESTERN AND CENTRAL ALEUTIANS WILL BE MOST UNSETTLED FOR THE FIRST HALF OF THE PERIOD, BEFORE THINGS SETTLE DOWN THERE, AS WELL, ONCE THE BLOCK LOCKS AND SEALS OUT FRESH ADVECTIONS. CISCO