Small Craft Advisory 79, NWS Fairbanks, AK

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
141 PM ADT THU SEP 6 2007

.SYNOPSIS...
THE UPPER LEVEL FLOW PATTERN NOW BEGINNING TO CHANGE INTO A MORE
TYPICAL FALL PATTERN WITH A DEEP TROUGH DEVELOPING IN THE BERING
SEA BY THE WEEKEND WITH A RESULTANT RIDGE DEVELOPING OVER EASTERN
ALASKA AND WESTERN CANADA. THIS WILL USHER THE FIRST BIG STORM OF
THE SEASON INTO THE EASTERN BERING SEA AND BE FOLLOWED BY A SERIES
OF LOWS NEXT WEEK. THIS WILL ALSO CAUSE MODERATE TO STRONG MOIST
SOUTHWEST FLOW TO DEVELOP OVER MOST OF NORTHERN ALASKA BY THIS
WEEKEND AND CONTINUE THROUGH NEXT WEEK EXCEPTING THE SOUTHEAST
INTERIOR WHERE THE FLOW WILL CAUSE PERIODIC CHINOOK WINDS.
THE BUILDING RIDGE WILL STABILIZE THE AIRMASS IN THE INTERIOR
THROUGH SAT.

A WEAK LOW SOUTH OF BARROW WILL MOVE EAST OF BARTER ISLAND FRI.
THIS IS CAUSING SCATTERED SHOWERS ALONG THE NORTH SLOPE THAT WILL
DECREASE FRI. A TROUGH NOW STRETCHING SOUTH FROM THAT LOW TO
DENALI WILL MOVE TO THE NORTHEAST INTERIOR THU NIGHT AND THEN DISSIPATE.
SHOWERS ALONG THIS TROUGH DIMINISH TO ISOLATED SHOWERS SOUTHWEST
OF IT. THERE WILL BE A THUNDERSTORMS THIS EVENING IN THE SUNNY
AREA NORTHEAST OF THIS TROUGH.

A STRONG SURFACE LOW NOW JUST NORTHEAST OF NEAR SHEMYA WILL MOVE
TO THE CENTRAL BERING SEA AS A 979 MB LOW FRI AFTERNOON AND TO THE
NORTHERN BERING SEA AS A 980 MB LOW SAT AFTERNOON AND THEN ROTATE
SLOWLY SOUTHWEST. THE ASSOCIATED WEATHER FRONT FROM THE LOW INTO
BRISTOL BAY WILL MOVE OVER NORTON SOUND AS A DISSIPATING FRONT FRI
AFTERNOON. EXPECT RAIN OVER THE NORTHERN BERING AND A CHANCE ALONG
THE WEST COAST WITH THIS FRONT, AND EAST WINDS TO 25KT.

A TRAILING BUT STRONGER FRONT WILL MOVE INTO BRISTOL BAY SAT
PM...TO NORTON SOUND BY 4AM SAT...AND TO THE SOUTHERN CHUKCHI SEA
AND WESTERN INTERIOR SAT AFTERNOON. RAIN WILL SPREAD NORTH ALONG
THE WEST COAST AND WESTERN INTERIOR JUST AHEAD OF THIS FRONT ALONG
WITH SOUTHEAST WINDS OF 25-35KT. THIS FRONT WILL SPREAD TO THE ARCTIC
COAST AND CENTRAL INTERIOR SAT NIGHT AND DISSIPATE ALONG THE
ALCAN BORDER SUN. FLOW WILL TURN SOUTH BEHIND THE FRONT SAT NIGHT
THROUGH MON AND AND COULD CAUSE HEAVY SURF SOUTH OF THE BERING STRAIT
ALONG SOUTH FACING SHORES SAT NIGHT THROUGH MON.

STRONG CHINOOK WINDS DEVELOPING OVER THE ALASKA RANGE FRI NIGHT
WILL CONTINUE THROUGH SAT NIGHT KEEPING RAIN AT BAY FOR THE
SOUTHEAST INTERIOR. THE CHINOOK WILL WEAKEN SUN AND RAIN IS
POSSIBLE THEN. THIS COULD CAUSE FIRE WEATHER HAZARDS SAT.

&&

.DISCUSSION...
MODELS INITIALIZE OK OVER NORTHERN ALASKA, BUT NAM IS WAY TO WEAK
ON LOW NEAR SHEMYA AT SURFACE AND ALOFT. GFS INITIALIZES MUCH
CLOSER BUT STILL A BIT TOO WEAK ON THIS FEATURE. SINCE THIS WILL
BE THE DOMINANT FEATURE AT THE SURFACE AND ALOFT FOR THE NEXT 3
DAYS WE ARE GOING WITH THE GFS SOLUTION WHICH MAINTAINS THIS LOW
DEEPER THAN THE NAM AND MOVES IT MUCH FASTER.

COASTAL HAZARD POTENTIAL DAYS 3 AND 4...
POTENTIAL HEAVY SURF ZONES 211, 213 AND 214 SAT NIGHT THROUGH MON.
FETCH APPEAR TOO SHORT FOR FLOODING AT THIS POINT.

&&

.FIRE WEATHER...
RHS OVER 80% TONIGHT...AND EXPECTED TO FALL TO 40-50% FRI EXCEPT
30-40% FRI IN ZONES 220-225.
WINDS WILL INCREASE ZONES 223 225 AND 226 FRI NIGHT WITH POSSIBLE
RED FLAGS FOR THOSE ZONES SAT AS THE RH DROPS. WINDS WILL DROP AND
HUMIDITIES RISE SUN IN THE INTERIOR.

&&

.HYDROLOGY...
NONE.

&&

.AFG WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY FOR PKZ200-PKZ210-PKZ240-PKZ245.
&&

JB SEP 07