040 FXAK69 PAFG 192014 AFDAFG NORTHERN ALASKA FORECAST DISCUSSION NATIONAL WEATHER SERVICE FAIRBANKS AK 1214 PM AKDT WED JUN 19 2013 .DISCUSSION... TEMPORARY RELIEF IN THE EXCESSIVE HEAT ACROSS NORTHERN ALASKA IS ON THE WAY BUT AT THE EXPENSE OF INCREASED THUNDERSTORM ACTIVITY AND NEW FIRE STARTS. THE LARGE HIGH PRESSURE RIDGE CURRENTLY OVER THE STATE WILL RETREAT EAST AND WEAKEN SLIGHTLY AS A BROAD AREA OF LOW PRESSURE MOVES NORTHWARD THROUGH THE BERING SEA. THIS WILL ALLOW SOME SLIGHTLY COOLER MARITIME AIR MOVE NORTH...WITH THE MOST PRONOUNCED COOLING IN THE WESTERN HALF OF THE STATE. INCREASED SOUTHEAST FLOW ALOFT BEGINNING TONIGHT WILL SPREAD MOISTURE NORTHWARD INTO THE FORECAST AREA. THIS COMBINED WITH INCREASING INSTABILITY WILL RESULT IN THUNDERSTORM ACTIVITY WHICH WILL PERSIST OVER PORTIONS OF NORTHERN ALASKA THROUGH THE UPCOMING WEEKEND. ISOLATED THUNDERSTORMS ARE POSSIBLE IN THE LOWER YUKON VALLEY THIS EVENING...WITH THE AXIS OF INSTABILITY SHIFTING NORTH ON THURSDAY AND EXTENDING FROM THE NORTHWEST ARCTIC TO THE SOUTHEAST INTERIOR. THE AREA OF INSTABILITY WILL EXPAND ON THE WEEKEND WITH THUNDERSTORMS POSSIBLE FROM THE NORTH SLOPES OF THE BROOKS RANGE SOUTH TO THE ALASKA RANGE. FORECAST MODELS BEGIN TO SHOW SOME DIFFERENCES EARLY NEXT WEEK BUT THEY ALL AGREE ON A THE HIGH PRESSURE RIDGE OVER CANADA REBUILDING INTO THE INTERIOR WITH TEMPERATURES WARMING AGAIN. THE RIDGE IS NOT AS PRONOUNCED THOUGH AND IT IS LIKELY THERE WILL BE A FEW MORE CLOUDS AND SOME SHOWERS DEVELOPING IN THE AFTERNOON AND EVENING. COASTAL HAZARD POTENTIAL DAYS 3 AND 4...NONE && .FIRE WEATHER...THE DEVELOPMENT OF THUNDERSTORMS OVER NEXT FEW DAYS WILL LIKELY INCREASE FIRE STARTS DUE TO THE EXTREMELY DRY CONDITIONS CAUSED BY THE LACK OF RAIN AND RECENT HEAT WAVE. && .HYDROLOGY...FREEZING LEVELS ABOVE 10000 FEET OVER THE PAST WEEK CONTINUE TO CAUSE GLACIALLY FED RIVERS DRAINING THE ALASKA RANGE TO RISE. TEMPERATURES ARE GOING TO COOL SLIGHTLY BUT GLACIAL RIVERS ARE EXPECTED TO CONTINUE TO SLOWLY RISE AND POSSIBLY APPROACH BANKFULL IN SOME LOW LOCATIONS ON THE WEEKEND. && .AFG WATCHES/WARNINGS/ADVISORIES... RED FLAG WARNING FOR AKZ208-AKZ210-AKZ212-AKZ214-AKZ215-AKZ216- AKZ217-AKZ218-AKZ219-AKZ220-AKZ221-AKZ222-AKZ223-AKZ224-AKZ225- AKZ226-AKZ227. && $$ EWP JUN 13 |