Flood in Alaska, May 1, 2009

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
435 AM AKDT THU APR 30 2009

.DISCUSSION...
...NEAR RECORD TO RECORD TEMPS ACROSS THE INTERIOR THROUGH SATURDAY...

A VERY STRONG 500 MB CLOSED HIGH IS CENTERED IN THE WESTERN YUKON
THIS MORNING. THE MODELS ARE IN GOOD AGREEMENT ON THE PATTERN BOTH
ALOFT AND AT THE SURFACE DURING THE NEXT 60 HOURS.  THE UPPER RIDGE
WILL GRADUALLY ELONGATE OUT TAKING ON MORE OF AN EAST TO WEST
ORIENTATION BY SATURDAY.

INTERIOR...THE VERY WARM WEATHER WILL CONTINUE THROUGH SATURDAY WITH
NEAR RECORD TO RECORD WARM TEMPERATURES.  THE FREEZING LEVEL ON THE
00Z AND 12Z PAFA SOUNDINGS WERE REMARKABLY HIGH AT NEAR 11K FT
ASL WITH A 500 MB HEIGHTS OF 576 DAM. THE 500 MB HEIGHTS WERE
ABOUT 20 METERS HIGHER THAN ANY OF THE MODELS AT 12Z. THE 850 MB
TEMPS ON THIS MORNINGS SOUNDING OF +9.0C WAS JUST 0.25C SHY OF THE
ALL TIME RECORD FOR APRIL.

THE HIGH YESTERDAY AT THE FAIRBANKS INTERNATIONAL AIRPORT WAS 74F
WHICH NOT ONLY BROKE THE PREVIOUS RECORD BUT ALSO TIED FOR THE
WARMEST TEMPERATURE EVER OBSERVED DURING THE MONTH OF APRIL. GIVEN
THAT THERE WILL BE LITTLE CHANGE IN THE AIRMASS TODAY AND FRIDAY
TEMPERATURES SHOULD BE JUST AS TOASTY WITH WIDEPREAD HIGHS IN THE
70S IN THE VALLEYS. THE MAIN CONCERNS THE NEXT COUPLE OF DAYS
WILL BE HYDRO AND FIRE WEATHER RELATED (PLEASE SEE APPROPRIATE
SECTIONS BELOW). THERE WILL CONTINUE TO BE SOME WIND IN THE PASSES
OF THE AK RANGE...BUT GIVEN THE LACK OF GOOD UPPER LEVEL SUPPORT
EXPECT THAT THE WIND REMAINS BELOW ADVISORY LEVELS...BUT WILL
CONTINUE TO NEED TO KEEP A CLOSE EYE ON THIS AS THE WIND AT ANTLER
CREEK HAS BEEN GUSTING TO 35 TO 45 MPH MUCH OF THE NIGHT.

NORTH SLOPE...CONTINUED NEAR RECORD TO RECORD WARMTH TODAY. IN FACT
TEMPS COULD COME CLOSE TO THE ALL-TIME RECORD FOR THE MONTH OF
APRIL AT BARROW WHICH IS 42F. FRIDAY INTO SATURDAY THE HEIGHTS
BEGINS TO GRADUALLY FALL AS THE UPPER RIDGE TAKES ON A MORE EAST
TO WEST ORIENTATION. THERE WILL ALSO BE A SURFACE RIDGE THAT
GRADUALLY BUILDS IN AND CAUSES THE WINDS TO TURN MORE ONSHORE.
TEMPS WILL STILL REMAIN A LITTLE ABOVE AVERAGE...BUT MOST OF THE
ARCTIC COAST WILL HAVE HIGHS BELOW FREEZING BY SATURDAY.

WEST COAST...THE DRYING TREND WITH INCREASING AMOUNTS OF SUNSHINE
WILL CONTINUE THROUGH FRIDAY. THERE WILL STILL BE A FEW SHOWERS ALONG
THE IMMEDIATE WEST COAST TODAY AND TONIGHT...WITH PERHAPS SOME
STEADIER RAIN OR WET SNOW THIS EVENING ON SAINT LAWRENCE ISLAND...
BUT THEN AS THE UPPER RIDGE BUILDS IN THE FROM THE EAST THE
CLOUDS SHOULD CLEAR OUT TO SAINT LAWRENCE ISLAND BY FRIDAY...WITH
THE MAINLY SUNNY WEATHER WITH ABOVE AVERAGE TEMPS LASTING INTO THE
WEEKEND.

MID-RANGE...THE PATTERN WILL BE UNDERGOING CHANGES WITH THE RIDGE
THAT WILL COVER MOST OF THE STATE TO BE REPLACED BY SOME
TROUGHIENESS. HEIGHTS AND THICKNESS VALUES RETURN TO SEASONABLE
LEVELS BY NEXT WEEK WHICH WILL LEAD TO A GRADUAL COOL DOWN SUNDAY
THROUGH TUESDAY.

&&

.FIRE WEATHER...RHS IN ZONES 221 THROUGH 226 DROPPED BELOW 20
PCT YESTERDAY AFTERNOON IN MOST AREAS...AND SEVERAL SPOTS HAD MIN
RHS BELOW 15 PCT. SIMILAIR CONDITIONS ARE EXPECTED TODAY AND
FRIDAY AND WILL NECESITATE STRONG HEADLINES AND/OR RED FLAG
WARNINGS FOR LOW RHS TODAY AND FRIDAY. THE FUELS ARE CONTINUING
TO DRY OUT...BUT MAY REMAIN THE ONLY LIMITING FACTOR FOR A WARNING
FOR THE LOW RHS.

&&

.HYDROLOGY...THE FLOOD WARNING FOR ICE JAM FLOODING FOR THE
TANANA RIVER IN SALCHA REMAIN IN EFFECT THROUGH FRI MORNING...WITH
ADDITIONAL ICE JAMS A CONCERN DOWN RIVER THE NEXT FEW DAYS AS
CONTINUED RAPID MELTING AND WARM TEMPS ARE EXPECTED THROUGH
SAT...THEN SLOW COOLING EXPECTED SUNDAY THROUGH EARLY NEXT WEEK
AS MORE SEASONABLY TEMPS RETURN TO THE INTERIOR.

&&

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

CB APR 09