Area Forecast Discussion
Issued by NWS Anchorage, AK

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
000
FXAK68 PAFC 230147
AFDAFC

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
447 PM AKST MON DEC 22 2014

.ANALYSIS AND UPPER LEVELS...
A BROAD SURFACE LOW OVER THE WESTERN GULF OF ALASKA CONTINUES TO
WRAP SNOW SHOWERS AROUND THE GULF LOCATIONS. COMBINED WITH AN
UPPER LEVEL DISTURBANCE...MORE CONCENTRATED SNOW ACTIVITY IS
OCCURRING OVER THE WESTERN KENAI PENINSULA. IN ADDITION...MORE
CONCENTRATED SNOW SHOWER ACTIVITY IS HITTING THE NORTHERN GULF
COAST WITH THE SOUTH TO SOUTHEAST ONSHORE FLOW. THE UPPER LEVEL
DISTURBANCE WILL LIFT NORTH THROUGH SOUTH CENTRAL ALASKA TONIGHT.
IT WILL LIFT THROUGH THE AREA TOMORROW BUT ENOUGH INSTABILITY WILL
REMAIN FOR SNOW SHOWERS ACROSS SOUTH CENTRAL.

OUT WEST...A FRONT IS WEAKENING OVER THE CENTRAL BERING SEA.
MEANWHILE...A LARGE LOW IS DEVELOPING SOUTH OF THE WESTERN
ALEUTIANS. THE LOW IS BEING STRENGTHENED DUE TO A 170 KT JET
MOVING OUT OF THE NORTHWEST PACIFIC. THIS LOW IS ANTICIPATED TO
DEEPEN INTO THE 950S BY TUESDAY MORNING WITH STORM TO HURRICANE
FORCE WINDS TUESDAY ACROSS THE WESTERN BERING AND ALEUTIANS. AN
ASSOCIATED WARM FRONT MOVES OUT INTO THE CENTRAL BERING BRINGING
RAIN AND SNOW THROUGHOUT THE ALEUTIANS AND BERING SEA. THE FRONT
WILL REACH THE WEST COAST WEDNESDAY MORNING.

&&

.MODEL DISCUSSION...

MODELS ARE IN FAIRLY GOOD AGREEMENT IN THE BIG PATTERN THROUGH
WEDNESDAY. HOWEVER...THE EXACT PLACEMENT OF LOW CENTERS OVER THE
GULF OF ALASKA AND WESTERN BERING IS A BIT OFF. THE FRONT THAT
MOVES THROUGH THE BERING SEA TUESDAY AND WEDNESDAY...DEVELOPS A
LOW OVER THE WESTERN GULF OF ALASKA. TIMING OF FRONTS WILL ALSO BE
AFFECTED BY THE PLACEMENT OF THE LOWS. THE ENERGIES ASSOCIATED
AROUND THE LOW IS WHERE THE DISCREPANCIES CREEP INTO THE WEATHER
SCENARIOS. THE TIMING OF EACH OF THESE SYSTEMS ROTATING AROUND THE
MAJOR LOW IN THE WESTERN BERING SEA FROM WEDNESDAY THROUGH
SATURDAY WILL BE NARROWED DOWN AS THE GUIDANCE GETS AHOLD OF THE
EXACT PLACEMENT OF THE MAJOR LOW. FURTHER OUT IN TIME...MODEL
GUIDANCE CONSOLIDATES ON A STRONG LOW IN THE EASTERN BERING WITH
SOUTHERLY FLOW OVER THE MAINLAND FRIDAY INTO SUNDAY.
THEREFORE...CONFIDENCE IS LOW ON THE EXACT TIMING OF FEATURES BUT
THERE WILL BE TWO FRONTS TO MOVE THROUGH THE BERING SEA OVER THE
NEXT FEW DAYS AND CONTINUE THROUGH THE MAINLAND. WITH A SERIES OF
DISTURBANCES ROTATING AROUND THE DOMINANT LOW IN THE WESTERN
BERING...EVENTUALLY THE LOW SETS UP IN THE EASTERN BERING SEA
OVER THE WEEKEND.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
THE LAST BATCH OF SHOWERS IN THIS UNSTABLE PATTERN IS MOVING
INLAND THIS EVENING. THE MAJORITY OF THE SHOWERS WILL BE IN THE
EVENING FOR MOST LOCATIONS...LINGERING THE LONGEST IN THE SUSITNA
VALLEY THROUGH THE MORNING HOURS. THE LAST DISTURBANCE WITH THIS
SYSTEM WILL MOVE FROM WEST TO EAST TOMORROW MORNING BRINGING LIGHT
SNOW TO THE NORTHERN COOK INLET REGION BEFORE DRYING OUT IN THE
AFTERNOON. WEDNESDAY MORNING WILL BRING BRIEF DRY AND CLEAR
CONDITIONS BEFORE A FRONT APPROACHES FROM THE SOUTHWEST GULF
RETURNING A CHANCE OF SNOW FOR MOST AREAS...ESPECIALLY ALONG THE
NORTH GULF COAST.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
WEAK LOW PRESSURE OVER THE WESTERN GULF...ALONG WITH A SERIES OF
WEAK WAVES MOVING THROUGH THE SOUTHWEST MAINLAND THROUGH TOMORROW
NIGHT WILL KEEP SOME ISOLATED SNOW SHOWERS AROUND THE AREA INTO
MID WEEK. A WEATHER FRONT ASSOCIATED WITH A STRONG LOW WEST OF
SHEMYA WILL PUSH INTO THE SOUTHWEST COAST OVERNIGHT
TUESDAY...SHIFTING THE LIGHT OFFSHORE FLOW TO AN ONSHORE FLOW AS
THE FRONT MOVES INLAND THROUGH WEDNESDAY. THIS WILL USHER IN SOME
WARMER TEMPERATURES OVER SOUTHWEST ALASKA...WITH THE WARMEST
TEMPERATURES MAINLY ALONG THE COASTLINE AND BELOW FREEZING
TEMPERATURES OVER MUCH OF THE INTERIOR. PRECIPITATION WILL
PREDOMINANTLY BE SNOW DUE TO COLD TEMPERATURES ALREADY IN PLACE IN
THE REGION. HOWEVER THERE IS A SLIGHT CHANCE FOR LIGHT FREEZING
RAIN OVER THE INTERIOR PORTIONS OF THE BRISTOL BAY ZONE...WITH
THE WARMER AIR ALOFT MOVING IN OVER THE COLDER TEMPERATURES AT THE
SURFACE ON WEDNESDAY.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
A STRONG LOW PRESSURE SYSTEM WILL TRACK THROUGH THE WESTERN
ALEUTIANS TUESDAY MORNING...BRINGING A MIXTURE OF RAIN AND SNOW TO
THE AREA ALONG WITH VERY GUSTY WINDS. A HIGH WIND WARNING HAS BEEN
ISSUED FOR THE WESTERN ALEUTIANS...WITH COLDER AIR WRAPPING BACK
INTO THE SYSTEM AND HELPING STRONGER WINDS FROM ALOFT TO MIX DOWN
TO THE SURFACE. THE INITIAL FRONTAL SYSTEM ASSOCIATED WITH THIS
LOW WILL BRING WARMER TEMPERATURES ALONG WITH PRECIPITATION AND
GUSTY WINDS TO THE WESTERN AND CENTRAL ALEUTIANS THIS EVENING.
THIS FRONT WILL THEN SPREAD THE GUSTY WINDS AND PRECIPITATION TO
THE NORTH AND EAST...REACHING THE ALASKA PENINSULA AND SOUTHWEST
COAST BY WEDNESDAY MORNING. A SECONDARY SURFACE CIRCULATION WILL
DEVELOP SOUTH OF THE WESTERN ALEUTIANS...AS AN UPPER LEVEL
DISTURBANCE OVER THE NORTH PACIFIC TRACKS OVER THE WESTERN
ALEUTIANS TOMORROW NIGHT. THIS WILL BRING IN ANOTHER ROUND OF
STEADY PRECIPITATION AND GUSTY WINDS TO THE WESTERN AND CENTRAL
ALEUTIANS THROUGH WEDNESDAY AFTERNOON.

&&

.LONG TERM FORECAST (DAYS 3 THROUGH 7)...

MODEL SOLUTIONS ARE COMING IN BETTER AGREEMENT WITH THE UPPER LOW
OVER THE WESTERN BERING WEDNESDAY INTO THE WEEKEND. THIS LOW
PRESSURE SYSTEM WILL SEND MULTIPLE SHORTWAVES EASTWARD AS IT
WOBBLES NEAR THE KAMCHATKA PENINSULA. THIS KEEPS A SHOWERY
PATTERN ACROSS THE SOUTHERN MAINLAND AND SURROUNDING WATERS THROUGH
THE EXTENDED FORECAST. A CHANGE FOR THE WEEKEND TAKES PLACE ON
SATURDAY AS A RIDGE AMPLIFIES AHEAD OF THIS SYSTEM OVER THE GULF
AND SOUTHCENTRAL. THE RIDGE SHIFTS EAST THROUGH THE WEEKEND WITH
SOUTHERLY FLOW ALLOWING A WARMER AIR MASS TO SURGE ACROSS THE GULF
AND MAINLAND.

&&


.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...NONE.
MARINE...GALES 150 155 165 170 171 172 173 174 175 176 179 180
         STORM 177 178 185
         HEAVY FREEZING SPRAY 180 181 185
FIRE WEATHER...NONE.

&&

$$

SYNOPSIS AND MODEL DISCUSSION...JN
SOUTHCENTRAL ALASKA...ML
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...TP
LONG TERM...KH


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.