Blizzard in Alaska, April 21, 2009

AREA FORECAST DISCUSSION...UPDATED
SOUTHCENTRAL AND SOUTHWEST ALASKA
200 PM AKDT TUE APR 21 2009

.MODEL DISCUSSION...MODELS HAVE INITIALIZED WELL THIS MORNING AND
CONTINUE TO AGREE ON THE PATTERN CHANGE OVER THE NEXT COUPLE DAYS.
BIG DISAGREEMENTS OCCUR WHEN THE PATTERN CHANGES AGAIN EARLY NEXT
WEEK. OVERALL...THE RIDGE OVER THE MAINLAND RIGHT NOW TO SLOWLY TRACK
EAST THROUGH THURSDAY ALLOWING A MOIST SOUTHWEST FLOW OVER THE
MAINLAND. THIS PROGRESSION WILL PUSH THE GULF LOW INTO CANADA AND THE
BERING LOW NORTH AND DISSIPATING TO AN OPEN WAVE OVER THE BERING
STRAIT BY FRIDAY. AN STRONG SHORT WAVE TO PUSH ACROSS THE MAINLAND
THURSDAY AND LEAVE A MOIST SOUTHWEST FLOW OVER THE STATE THROUGH
FRIDAY MORNING. ANOTHER LOW TO DEVELOP IN THE WESTERN BERING FRIDAY
WITH THE RIDGE RE-AMPLIFYING OVER THE MAINLAND AND GULF.
HOWEVER...THE RIDGE WILL REMAIN MOIST WITH SHOWERS. THE BERING LOW TO
SWING EAST THROUGH THE WEEKEND AND BRING CONTINUED MOISTURE AND A
STRONG JET AND VORT MAX TO THE AREA SATURDAY. CONTINUED SOUTHWEST
FLOW IS EXPECTED OVER THE MAINLAND WITH THE LOW IN THE CENTRAL AND
EASTERN BERING THROUGH EARLY NEXT WEEK.

ONCE AGAIN...THE TRIPLE POINT LOW THAT WAS EXPECTED TO DEVELOP IN
BRISTOL BAY TOMORROW. NOW...NONE OF THE MODELS HAVE IT DEVELOPING. I
STILL THINK THERE WILL BE A LOW THERE AT SOME POINT. IT SHOULD DEEPEN
SOME AS IT REACHES THE COLDER AIR IN THE KUSKOKWIM DELTA. FOR
NOW...THE FORECAST HAS DOWNPLAYED THE INTENSITY OF THIS LOW.

.ANALYSIS AND UPPER LEVELS...
THE TROUGH-RIDGE-TROUGH PATTERN OF THE LAST SEVERAL DAYS REMAINS IS
SLIDING EAST. A STRONG FRONT IS MOVING THROUGH THE CENTRAL ALEUTIANS
WITH AN ACCOMPANYING 110 KT JET. THIS IS BRINGING SOME VERY STRONG
GUSTINESS TO DUTCH HARBOR CURRENTLY. THE GULF LOW HAS MOVED TO THE
PANHANDLE WITH A GOOD PRESSURE GRADIENT OVER THE GULF. COMBINED WITH
A WEST NORTHWEST FLOW OVER THE AREA...STRONG GAP WINDS ARE PRESENT
TODAY. THE LOW WILL WEAKEN AS THE HIGH CENTERS OVER THE GULF TONIGHT.
THE FRONT TO MAKE ITS WAY TO THE COAST THIS EVENING.

.SHORT TERM FORECAST...
.EAST OF THE ALASKA RANGE...SUNNY CONDITIONS WILL PERSIST OVER THE
NEXT DAY AS THE HIGH PRESSURE MOVES OVER THE AREA. THE WEAKENING LOW
PRESSURE IN THE EASTERN GULF PRESERVING GAP WINDS DUE TO A MODERATE
TO STRONG NORTH TO NORTHWEST FLOW. THE LOW WILL WEAKEN TONIGHT AND
LESSEN THE GRADIENT AND GAP WINDS. HIGHER CLOUDS TO MOVE IN TOMORROW
AS THE RIDGE AXIS MOVES TO THE EAST OF ANCHORAGE. A SHORT WAVE MOVING
AROUND THE BERING LOW WILL BRING A CHANCE OF SHOWERS TO KODIAK
TOMORROW AFTERNOON AND THIS WILL SWING TO THE SUSITNA TOMORROW NIGHT.
A STRONGER WAVE TO PUSH THROUGH ON THURSDAY AFTERNOON AND EVENING
BRINGING A SHOT OF RAIN TO MOST OF THE AREA.

.WEST OF THE ALASKA RANGE...A STRONG FRONT IS MOVING THROUGH THE
CENTRAL ALEUTIANS TO THE AKPEN TODAY. VERY STRONG GUSTS ARE
ACCOMPANYING THIS FRONT AS IT TRACKS EASTWARD. THE FRONT WILL PUSH
INTO THE KUSKOKWIM DELTA AND WESTERN CAPES THIS EVENING AND SPREAD
FURTHER INLAND TOMORROW. THE FRONT WILL REMAIN ALONG THE COAST
THROUGH THURSDAY MORNING. A SECONDARY WAVE ROTATING AROUND THE BERING
LOW WILL PUSH THE FRONT ACROSS THE ALASKA RANGE THURSDAY AFTERNOON
AND EVENING. SHOWERS WILL PERSIST CLOSER TO THE LOW AND BEHIND IT.
MAY WANT TO GO WITH A BLIZZARD WARNING RIGHT ALONG THE KUSKOKWIM
COAST THIS EVENING AS THE FRONT ARRIVES. TEMPERATURES MAY NOT CHANGE
OVER THAT QUICKLY. FURTHER INLAND...CLEAR SKIES WILL GIVE WAY TO
HIGHER CLOUDS TOMORROW AND SOME SHOWERS BY WEDNESDAY NIGHT.

.LONG TERM FORECAST...WARM MOIST SOUTHWEST FLOW TO REMAIN OVER HE
MAINLAND THROUGH EARLY NEXT WEEK. THE BIG DAY LOOKS LIKE SATURDAY FOR
MOST OF THE MAINLAND. THE MORE ORGANIZED WEATHER WILL CONTINUE IN THE
GULF THROUGH SUNDAY. SHOWERS TO REMAIN WITH THE PARENT LOW IN THE
BERING AND BEHIND IT.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...NONE.
MARINE...GALE 155 160 165 172 176 179 180 185
FIRE WEATHER...NONE.

JN APR 09