Flood in Alaska, April 30, 2009

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
227 PM AKDT WED APR 29 2009

.DISCUSSION...

UPPER AIR: TWO MAJOR FEATURES ON THE MAP INCLUDE 575 DM HIGH WITH
CENTER ALONG THE ALCAN BORDER... NEAR BEAVER CREEK... AND 497 DM
LOW WELL NORTHWEST OF WRANGEL ISLAND... MOVING OFFSHORE FROM
SIBERIA. THE LOW WILL MOVE RAPIDLY NORTHEAST... ALLOWING RIDGING
TO EXPAND WESTWARD TO THE EASTERN BERING AND CHUKCHI SEAS ON FRI.
BY FRI AFTERNOON... THE LOW WILL BE 505 DM ABOUT 650 MILES NORTH
OF BARTER ISLAND AND THE CENTER OF THE HIGH WILL REMAIN LOCKED IN
PLACE NEAR BEAVER CREEK WITH RIDGING WESTWARD.

SURFACE: HIGH PRESSURE CENTERED OVER THE YUKON TERRITORY OF CANADA
WILL EXPAND WEST TO COVER MUCH OF NORTHERN ALASKA ON THU. BY FRI
AFTERNOON... A 1032 MB HIGH WILL BE CENTERED NORTHWEST OF BARROW.
THE HIGH WILL DRIFT AROUND IN THE ARCTIC NORTH OF BARROW... BUT
WILL BE GENERALLY A PERSISTENT FEATURE AT LEAST INTO EARLY NEXT
WEEK. A FRONTAL BOUNDARY WILL BE PUSHED WEST OF SAINT LAWRENCE
ISLAND FRI MORNING AND TO SIBERIA ON SAT BY THE BUILDING RIDGE.

NORTH SLOPE: SIGNIFICANT COOLING FROM THE NEAR RECORD HIGHS WILL
BEGIN IN ERNEST ON FRI. THE COOLER WEATHER WILL LIKELY PERSIST
UNTIL AT LEAST MID WEEK. OFFSHORE FLOW FROM BARROW EAST WILL BEGIN
A SLOW REVERSAL ON FRI AS HIGH PRESSURE CENTERED NEAR WRANGEL
ISLAND RIDGES SOUTHEAST. THE RESULTING ONSHORE FLOW WILL BE
FAVORABLE FOR FLURRIES AND FOG... FROM BARROW EAST... FOR FRI
THROUGH EARLY NEXT WEEK. WEST OF BARROW... THE FLOW MAY REMAIN
OFFSHORE. WINDS WILL BE GENERALLY LESS THAN 20 KT.

WEST COAST: AN INCREASINGLY DRY PATTERN WILL CONTINUE THROUGH
FRI. HIGH PRESSURE RIDGING WESTWARD WILL PUSH A FRONTAL BOUNDARY
WEST OF SAINT LAWRENCE ISLAND FRI MORNING WITH ALL ASSOCIATED
PRECIPITATION ALSO MOVING WEST OF THE ISLAND. THE DRY PATTERN WILL
EXTEND WELL INTO NEXT WEEK.

INTERIOR: RECORD HIGH TEMPERATURES FOR THE MONTH OF APRIL FOR THE
SOUTHEAST INTERIOR ARE LIKELY. THE RECORD HIGH TEMPERATURE FOR
FAIRBANKS FOR THE MONTH OF APRIL IS 74 SET IN 1960. FRIDAY WILL
BE THE PEAK OF OUR ONGOING WARM PATTERN FOR MOST OF THE
INTERIOR... THE SOUTHEAST SHOULD REMAIN NEAR PEAK ON SAT. A
SPECIAL REMARK HAS BEEN ADDED IN THE FIRE WEATHER PARAGRAPH FOR
WINDS ASSOCIATED WITH THE CHANGE.

MID RANGE: MODELS ARE COMING INTO GENERAL AGREEMENT WITH ENDING
THE WARM SPELL FOR MUCH OF THE NORTHERN PART OF THE FORECAST AREA
ON SAT AND FOR MOST OF THE REST OF NORTHERN ALASKA ON SUN... THE
EXCEPTION BEING THE SOUTHWEST TO WEST. A COOLER PATTERN MAY EXTEND
THROUGH THE MID RANGE... DAY 8/THU. WINDS THROUGH ALASKA RANGE
PASSES WILL DIMINISH THU NIGHT AND FRI AS RIDGE BUILDS WEST.

&&

.FIRE WEATHER...MODELS ARE COMING INTO AGREEMENT FOR THE WEEKEND
CONCERNING COLD AIR PUSH FROM THE NORTHEAST. THIS WOULD GIVE
INCREASING DRY NORTHEAST WINDS DURING THE WEEKEND WITH THE
INCREASED WINDS EXTENDING INTO MON.

&&

.HYDROLOGY...FLOOD WARNING FOR ICE JAM FLOODING FOR THE TANANA
RIVER IN SALCHA HAS BEEN EXTENDED UNTIL FRI AT 1130 AM. CONTINUED
RAPID MELTING IS EXPECTED THROUGH FRI... THEN RELIEF LIKELY
STARTING DURING THE WEEKEND AS COLDER AIR PUSHES INTO THE
INTERIOR.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
BRISK WIND ADVISORY FOR PKZ200-PKZ210-PKZ215-PKZ220-PKZ225-
PKZ230.
&&

DA APR 09