Area Forecast Discussion - Northern


FXAK69 PAFG 201038
AFDAFG

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
238 AM AKDT SAT SEP 20 2014
.DISCUSSION...
MODELS INITIALIZED WELL AND REMAIN IN GOOD AGREEMENT THROUGH THE
SHORT TERM BUT THE MODELS BEGIN TO DISPLAY CONSIDERABLE DIFFERENCES
IN STRENGTH AND POSITION OF A LOW MOVING NORTHEAST OUT OF THE
SOUTHERN CHUKCHI SEA MONDAY AFTERNOON. THE 00Z NAM AND GFS ARE
WITHIN A COUPLE MB OF EACH OTHER AND VERY CLOSE ON TRACK TAKING
THE LOW NORTHEAST ALONG THE NORTHWEST COAST ON A TRACK ABOUT 75 NM
OFF SHORE AS A 992 TO 994 MB LOW WHILE THE ECMWF TRACKS A LOW THAT
IS SLOWER TO DEEPEN BUT ULTIMATELY IS AROUND 988 MB BUT TRACKS
PARALLEL TO THE NAM AND GFS TRACKS BUT 150 NM TO THE NORTHWEST.
SIMILAR TRACK DIFFERENCES ARE NOTED AT 700 HPA AND 500 HPA. TIGHT
GRADIENTS AROUND THE LOW WILL LIKELY PRODUCE GALE FORCE WEST TO
NORTHWEST WINDS ALONG THE NORTHWEST COAST MONDAY. THE MODEL
SPREAD CONTINUES TO INCREASE THROUGH THE MID TERM AND LONG TERM.

ALOFT AT 500 HPA A 530 DAM CLOSED LOW CENTERED NEAR WRANGELL ISLAND
WILL CONTINUE TO SPIN SHORT WAVES SOUTH AND EAST INTO A LONG WAVE
TROUGH CENTERED OVER WESTERN ALASKA AS A RIDGE BUILDS IN THE
BERING SEA. A 540 DAM LOW CURRENTLY CENTERED OVER KODIAK ISLAND
WILL DEEPEN AS IT DIGS SOUTH SATURDAY NIGHT AND THEN MOVES
NORTHEAST INTO THE NORTHEAST GULF OF ALASKA AS A 538 DAM LOW. THIS
COMBINED WITH FAVORABLE UPPER LEVEL DYNAMICS PRODUCES DEEP
CYCLOGENISIS IN THE NORTHEASTERN GULF SUNDAY MORNING. AGAIN THE
MODELS DISPLAY CONSIDERABLE SPREAD WITH SURFACE LOW POSITION
DIFFERING BY OVER 200 NM AND LOW DEPTH VARYING FROM 976 MB TO 992
MB IN THE NORTHEASTERN GULF OF ALASKA SUNDAY MORNING. THE
CONSENSUS FROM THE MODEL GUIDANCE MOVES THE LOW RAPIDLY NORTH
WITH LANDFALL NEAR YAKUTAT SUNDAY NIGHT INTO MONDAY MORNING.
MOISTURE FROM THIS LOW SPREADS NORTHWEST INTO THE SOUTHEAST
INTERIOR MONDAY MORNING AND CONTINUES TO MOVE NORTH ALONG THE
ALCAN BORDER INTO TUESDAY.

ON THE SURFACE A WEAK LOW CONTINUES TO MOVE NORTH INTO THE
SOUTHERN INTERIOR ATTM AND WILL CONTINUE TO MOVE NORTH AND EAST AS
A STRONG COLD FRONT PLOWS EASTWARD OUT OF THE WESTERN INTERIOR
SATURDAY INTO THE CENTRAL INTERIOR SUNDAY AND STALLS OVER THE
SOUTHEAST INTERIOR MONDAY AS IT INTERACTS WITH THE REMNANTS OF THE
LOW MOVING NORTH OUT OF THE GULF OF ALASKA.

ARCTIC COAST AND PLAIN...LIGHT SNOW...FOG AND LOW CEILINGS
CONTINUE OVER MUCH OF THE NORTH SLOPE WITH GENERALLY LESS THAN 1
INCH EXPECTED THROUGH SATURDAY AFTERNOON. TIGHT GRADIENT CONTINUES
OVER THE EASTERN NORTH SLOPE THROUGH THIS MORNING WITH STRONG WIND
HEADLINES FOR ZONES 203 AND 204. WINDS ARE EXPECTED TO DIMINISH BY
EARLY AFTERNOON.

WEST COAST AND WESTERN INTERIOR...RAIN SHOWERS ASSOCIATED WITH
THE LOW MOVING NORTH OUT OF SOUTH CENTRAL ALASKA WILL DIMINISH AS
THE COLD FRONT MOVES EAST OUT OF THE WESTERN INTERIOR INTO THE
CENTRAL INTERIOR AND AS THE HIGH PRESSURE RIDGE BUILDS OVER THE
BERING SEA.

INTERIOR...SCATTERED SHOWERS THIS MORNING WILL INCREASE IN
COVERAGE TODAY AS MOISTURE FROM THE WEAK LOW THAT MOVED OUT OF
SOUTH CENTRAL INTERIOR IS PULL NORTHWARD AHEAD OF THE COLD FRONT
MOVING EAST OUT OF WESTERN ALASKA. EXPECT PERIODS OF RAIN TODAY TO
TRANSITION TO SHOWERS TONIGHT AND SUNDAY. GAP FLOW AHEAD OF THE
FRONT IN THE EASTERN ALASKA RANGE CONTINUES WITH WIND ADVISORY
HOISTED FOR PASSES IN ZONE 226. WINDS ARE EXPECTED TO DIMINISH BY
LATE SATURDAY MORNING.

COASTAL HAZARD POTENTIAL DAYS 3 AND 4...NONE

&&
.HYDROLOGY...
NONE

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY FOR AKZ226.

SMALL CRAFT ADVISORY FOR PKZ210-PKZ220-PKZ235.

GALE WARNING FOR PKZ240-PKZ245.
&&

$$

CCC SEP 14