Flood Watch 4, NWS Fairbanks, AK

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
423 AM AKDT TUE AUG 25 2015

.SYNOPSIS...
ALOFT...
THE LONG WAVE PATTERN CONSISTS OF A DEEP TROUGH STRETCHING FROM
WRANGEL ISLAND ACROSS THE WESTER BERING SEA TO THE NW PACIFIC AND
A RIDGE OVER THE WESTERN GULF OF ALASKA OVER MAINLAND AK. THIS IS
CAUSING A VERY WET SW FLOW PATTERN AS A FORMER TROPICAL STORM IN
THE N PACIFIC IS FEEDING HIGH MOISTURE AIR NORTHEAST ACROSS THE
BERING SEA AND INTO A SERIES OF STRONG SHORT WAVES AND THEIR
ASSOCIATED SURFACE LOWS MOVING EAST ACROSS AK THE NEXT SEVERAL
DAYS. BY THU SEVERAL OF THE SHORT WAVES WILL MERGE TO FORM A LONG
WAVE TROUGH OVER MAINLAND AK WHICH WILL PERSIST INTO THE WEEKEND.
THIS MEANS NORTHERN ALASKA IS IN FOR SIGNIFICANT RAIN THROUGH WED
AND THEN MUCH COOLER TEMPERATURES THU INTO THE WEEKEND.

850 MB TEMPERATURES RANGE FROM 2C ALONG THE ALCAN BORDER TO 10C
ALONG THE WEST COAST. WILL SEE TEMPERATURES INCREASING 2-4C OVER
THE INTERIOR AND ARCTIC COAST TODAY. STRONG COLD ADVECTION WILL
PUSH 850 TEMPS BELOW 0C IN NW ALASKA WED AND ACROSS THE BROOKS
RANGE AND ARCTIC AND WEST COASTS WED NIGHT AND THU.

SURFACE...
A 990 MB LOW 200 NM WEST OF POINT LAY WILL MOVE TO 300 NM WEST OF
BARROW AS A 990 MB LOW BY 4PM TUE...TO 300 NM NORTHWEST OF BARROW
AS A 986 MB LOW BY 4PM WED...AND TO 400 NM NORTH OF BARROW AS A
990 MB LOW BY 4PM THU. GALE FORCE EAST WINDS NE OF THIS LOW. WILL
SEE SW 20-30KT WINDS SOUTH OF THE LOW. WILL SEE NW GALES SW OF
THE LOW WED THROUGH THU.

AN OCCLUDED FRONT STRETCHING FROM THE LOW TO WAINWRIGHT WITH A
WARM FRONT FROM WAINWRIGHT TO MCGRATH AND A COLD/STATIONARY FRONT
FROM WAINWRIGHT A WAVE IN THE CENTRAL BERING SEA. BY 4PM TUE THE
STATIONARY FRONT WILL MOVE TO BARROW TO A WAVE NEAR KOTZEBUE TO
THE YUKON DELTA WITH THE WARM FRONT FROM DEADHORSE TO FAIRBANKS.
BY 4AM SAT STATIONARY FRONT BECOMES A COLD FRONT FROM DEADHORSE TO
A FRONTAL WAVE NEAR THE BERING STRAIT TO THE YUKON DELTA WITH A
WARM FRONT FROM BARTER ISLAND TO NORTHWAY. BY 4PM WED A COLD FRONT
WILL LIE FROM BARTER ISLAND TO BETTLES TO MCGRATH WITH AN ARCTIC
FRONT MOVING EAST TO BARROW TO THE BERING STRAIT. BY 4AM THU COLD
FRONT FROM OLD CROW TO FAIRBANKS TO DENALI WITH THE ARCTIC FRONT
FROM BARTER ISLAND TO AMBLER TO GAMBELL. BY 4PM THU THE COLD FRONT
WILL LIE FROM DAWSON TO TOK WITH THE ARCTIC FRONT FROM OLD CROW TO
FAIRBANKS TO DENALI. EXPECT HEAVY RAIN BETWEEN THE WARM FRONT AND
COLD/STATIONARY FRONT WITH 1-3 INCHES OVER THE WEST COAST AND
WESTERN INTERIOR THROUGH WED. THE HEAVIEST RAIN WILL BE IN SW
FACING SLOPES OF ZONES 208 218 AND 212. WILL SEE 1-2 INCHES OF
RAIN IN THE CENTRAL AND EASTERN INTERIOR TONIGHT THROUGH THU.
THERE WILL BE SW WINDS 25-35KT ALONG THE STATIONARY/COLD FRONT.

WILL SEE RAIN CHANGE TO SNOW ALONG THE ARCTIC COLD FRONT FROM THE
BROOKS RANGE NORTH. COULD SEE 3-6 INCHES OF SNOW FROM THE BROOKS
RANGE NORTH WED NIGHT AND THU. WILL SEE NW WINDS 20-30 KT WITH
THIS FRONT WITH THE STRONGEST WINDS IN NE PART OF THE STATE.

WILL CHANGE FLASH FLOOD FOR ZONES 208 212 TO SMALL STREAM FLOOD
ADVISORIES AND ADD ZONE 217. AT THIS TIME DO NOT EXPECT FLOODING
OF LARGER RIVERS BUT WILL KEEP AN EYE ON THIS. ALL RIVERS ACROSS
NORTHERN ALASKA WILL BE RISING SIGNIFICANTLY THROUGH THE WEEK.

&&

.DISCUSSION...
MODELS INITIALIZE WELL AND SHOW SIMILAR SOLUTIONS THROUGH 4PM
WED. AFTER THAT MODELS DIFFER ON TIMING AND STRENGTH OF SHORT
WAVES ALOFT WITH DIFFERENCES BECOMING LARGE BY THE WEEKEND. THE
GFS SHOWS HIGHER PRECIPITATION AMOUNTS THAN THE NAM AND ECMF
TODAY...BUT THE GFS PRECIPITATION AMOUNTS INITIALIZE BETTER AT
06Z. SINCE SATELLITE PICS SHOW MOISTURE FROM A FORMER TROPICAL
STORM FEEDING INTO THE MOISTURE FEED OVER THE BERING SEA THE
HIGHER AMOUNTS SHOWN ON THE GFS SEEM REASONABLE.

COASTAL HAZARD POTENTIAL DAYS 3 AND 4...
HIGH SURF ZONES 211 212 213 AND 214 TODAY THROUGH WED BUT
DIMINISHING FROM THE WEST. POSSIBLE HEAVY SURF ZONES 201 AND 202
WED NIGHT AND THU.

&&

.FIRE WEATHER...
NONE.

&&

.HYDROLOGY...
WILL CHANGE FLASH FLOOD FOR ZONES 208 212 TO FLOOD WATCH AND ADD
ZONE 217. AT THIS TIME SMALL STREAMS HAVE A CHANCE OF FLOODING.
DO NOT EXPECT FLOODING OF LARGER RIVERS BUT WILL KEEP AN EYE ON
THIS. ALL RIVERS ACROSS NORTHERN ALASKA WILL BE RISING
SIGNIFICANTLY THROUGH THE WEEK.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
HIGH SURF ADVISORY FOR AKZ211-AKZ212-AKZ213-AKZ214.

FLOOD WATCH FOR AKZ208-AKZ212-AKZ217.

SMALL CRAFT ADVISORY FOR PKZ200-PKZ210-PKZ215-PKZ220-PKZ225-
PKZ230-PKZ235-PKZ240-PKZ245.

GALE WARNING FOR PKZ210.
&&

AUG 15