Dense Fog Advisory 21, NWS Anchorage, AK

661 
WWAK71 PAFC 112233
NPWAER

URGENT - WEATHER MESSAGE
NATIONAL WEATHER SERVICE ANCHORAGE AK
133 PM AKST THU DEC 11 2014


AKZ101-120300-
/O.EXT.PAFC.FG.Y.0021.000000T0000Z-141212T0300Z/
ANCHORAGE-
INCLUDING THE CITIES OF...ANCHORAGE...EAGLE RIVER...INDIAN...
EKLUTNA
133 PM AKST THU DEC 11 2014

...DENSE FOG ADVISORY NOW IN EFFECT UNTIL 6 PM AKST THIS
EVENING...

* VISIBILITY...ONE QUARTER MILE OR LESS AT TIMES.

* TIMING...THROUGH THE AFTERNOON.

* IMPACTS...VERY LOW VISIBILITIES CAN CAUSE VERY DIFFICULT 
  DRIVING CONDITIONS. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A DENSE FOG ADVISORY MEANS VISIBILITIES WILL FREQUENTLY BE
REDUCED TO LESS THAN ONE QUARTER MILE. IF DRIVING...SLOW DOWN...
USE YOUR HEADLIGHTS...AND LEAVE PLENTY OF DISTANCE AHEAD OF YOU.

&&

$$

207 
WWAK71 PAFC 112233 CCA
NPWAER

URGENT - WEATHER MESSAGE...CORRECTED
NATIONAL WEATHER SERVICE ANCHORAGE AK
133 PM AKST THU DEC 11 2014


AKZ101-120300-
/O.COR.PAFC.FG.Y.0021.000000T0000Z-141212T0300Z/
ANCHORAGE-
INCLUDING THE CITIES OF...ANCHORAGE...EAGLE RIVER...INDIAN...
EKLUTNA
133 PM AKST THU DEC 11 2014

...DENSE FOG ADVISORY NOW IN EFFECT UNTIL 6 PM AKST THIS
EVENING MAINLY ALONG THE INLET AND KNIK ARM...

* LOCATION...MAINLY ALONG THE INLET AND KNIK ARM.

* VISIBILITY...ONE QUARTER MILE OR LESS AT TIMES.

* TIMING...THROUGH THE AFTERNOON.

* IMPACTS...VERY LOW VISIBILITIES CAN CAUSE VERY DIFFICULT 
  DRIVING CONDITIONS. 

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A DENSE FOG ADVISORY MEANS VISIBILITIES WILL FREQUENTLY BE
REDUCED TO LESS THAN ONE QUARTER MILE. IF DRIVING...SLOW DOWN...
USE YOUR HEADLIGHTS...AND LEAVE PLENTY OF DISTANCE AHEAD OF YOU.

&&

$$

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
325 AM AKST THU DEC 11 2014

.ANALYSIS AND UPPER LEVELS...
THERE IS AN UPPER LEVEL LOW CENTERED NEAR THE ALASKA PENINSULA
AND ANOTHER OVER THE SOUTHEASTERN GULF WITH WEAK CYCLONIC FLOW IN
BETWEEN OVER BASICALLY THE ENTIRE GULF. WEAK SURFACE FLOW AND
CLEARING SKIES ALOFT OVER PARTS OF THE SOUTHCENTRAL MAINLAND HAVE
LED TO FOGGY CONDITIONS SETTING UP OVER THESE AREAS OVERNIGHT...AND
PERSISTED THROUGH THE EARLY MORNING. SHOWERY CONDITIONS OVER THE
BRISTOL BAY AREA HAVE STARTED TO SLOWLY TAPER OFF THIS
MORNING...WITH THE UPPER LOW OVER THE ALASKA PENINSULA WEAKENING
AND DRIFTING FURTHER SOUTH. A RIDGE OVER THE CENTRAL BERING SEA
HAS KEPT GUSTY NORTHWEST FLOW OVER PARTS OF THE EASTERN ALEUTIANS
AND ALASKA PENINSULA...AS WELL AS PRODUCE RAIN AND SNOW SHOWERS
OVER THE AREA.

&&

.MODEL DISCUSSION...
MODELS ARE IN GOOD AGREEMENT WITH THE OVERALL PATTERN THROUGH
SATURDAY AFTERNOON...WHERE THEY BEGIN TO DIVERGE SLIGHTLY FROM A
COMMON SOLUTION. THE FIRST DIFFERENCE WORTH MENTIONING IS THE
TIMING AND STRENGTH DIFFERENCES OF THE LOW SOUTH OF THE GULF
SATURDAY. THE GLOBAL MODELS SEEM TO HAVE A BETTER HANDLE ON THIS
SYSTEM CURRENTLY...WHERE THE SLOWER 00Z NAM BECOMES THE OUTLIER BY
KEEPING THE SYSTEM OVER THE NORTH PACIFIC LONGER. ANOTHER
DIFFERENCE WORTH MENTIONING WOULD BE THE SLIGHT TIMING DIFFERENCE
OF THE FRONT PUSHING INTO THE WESTERN BERING/ALEUTIANS ON
FRIDAY...WITH THE ECMWF BEING SLIGHTLY FASTER (~3HRS) THAN THE
OTHER MODELS. WITH OVERALL GOOD MODEL AGREEMENT THROUGH
SATURDAY...FORECAST CONFIDENCE REMAINS GENERALLY HIGHER THAN
NORMAL FOR THIS TIME PERIOD.

&&

.SHORT TERM FORECAST SOUTHCENTRAL ALASKA (DAYS 1 AND 2)...
MOIST CONDITIONS AND CLEARING SKIES HAVE LED TO FOG AND STRATUS
FORMATION THROUGHOUT MUCH OF THE SOUTHCENTRAL. THERE IS ALSO AN
OVERALL LACK OF A LARGE PRESSURE GRADIENT AND NO MAJOR FEATURES
THAT WOULD CAUSE STRONG WINDS TO MIX OUT THE FOG.
HOWEVER...THROUGHOUT THE DAY A WEAK DISTURBANCE WILL MOVE THROUGH
FROM THE WEST WHICH WILL DESTABILIZE THE AREA AND MIX OUT SOME OF
THE FOG. ANOTHER WEAK WAVE WILL PUSH INTO THE NORTH GULF COAST
TONIGHT AND THEN OVER THE COPPER RIVER BASIN BRINGING BACK
PRECIPITATION TO THOSE AREAS TOMORROW.

&&

.SHORT TERM FORECAST SOUTHWEST ALASKA (DAYS 1 AND 2)...
THE REMNANTS OF THE DISSIPATING LOW OVER CHIGNIK WILL BRING
WINTRY SHOWERY PRECIPITATION TO THE BRISTOL BAY REGION. THERE WILL
BE ISOLATED POCKETS OF LIGHT FREEZING RAIN NEAR THE KING SALMON
AREA EXTENDING SOUTH TOWARDS EGEGIK DURING THE EVENING. BY
THURSDAY MORNING AN UPPER LEVEL WEAK RIDGE OF HIGH PRESSURE WILL
BUILD INTO THE SOUTHWEST ALASKA AREA. BY LATE THURSDAY AFTERNOON A
WEAK SHORTWAVE WILL PUSH THROUGH THE SOUTHWEST ALASKA REGION
BRINGING A BRIEF PERIOD OF SHOWERY PRECIPITATION WITH THE
TEMPERATURES REMAINING BELOW FREEZING. THE WINDS WILL REMAIN
NORTHEASTERLY BEFORE SHIFTING TO NORTHWESTERLY ALONG THE SOUTHWEST
ALASKA COAST BY THURSDAY. THE MODELS WERE IN GOOD SYNOPTIC
AGREEMENT WITH THE NAM AND THE GEM-REG BEING THE PREFERRED MODELS
OF CHOICE. THE FORECAST CONFIDENCE REMAINS ABOVE AVERAGE.

&&

.SHORT TERM FORECAST BERING SEA/ALEUTIANS (DAYS 1 AND 2)...
THE EASTERN SIBERIAN HIGH REMAINS STATIONARY WHICH WILL KEEP THE
NORTHERLY WINDS THROUGH THE BERING SEA/ALEUTIANS THROUGH
THURSDAY. THE EASTERN ALEUTIANS WILL HAVE SOME GAP WINDS WITH THE
NORTHWESTERLY FLOW BEFORE DIMINISHING BY THURSDAY AFTERNOON. THIS
WILL BRING SHOWERY PRECIPITATION THROUGHOUT THE BERING SEA AND
ALEUTIAN CHAIN THROUGH THURSDAY. THE TEMPERATURES WILL REMAIN
BELOW FREEZING THROUGHOUT THE BERING WITH THE COLD AIR FILTERING
IN WITH THE NORTHERLY FLOW. THE MODELS CONTINUE TO BE IN GOOD
AGREEMENT WITH ABOVE AVERAGE FORECAST CONFIDENCE.

&&

.LONG TERM FORECAST (SATURDAY THROUGH WEDNESDAY)...

AN ACTIVE AND COMPLEX WEATHER PATTERN IS IN STORE THIS WEEKEND
THROUGH THE MIDDLE OF NEXT WEEK. THE EXTENDED FORECAST BEGINS WITH
A LOW PRESSURE SYSTEM ENTERING THE NORTHERN GULF OF ALASKA LATE
SUNDAY FROM THE NORTH PACIFIC. MODELS ARE STRUGGLING WITH THE
PLACEMENT OF THE LOW CENTER (OR MULTIPLE CENTERS) WHICH WILL
GREATLY IMPACT THE OVERALL PRECIPITATION AND WIND REGIME. AS IT
STANDS NOW...IT APPEARS A POTENT BARRIER JET WILL SITUATE ALONG
THE NORTHERN GULF COAST LATE SATURDAY AND LINGER THROUGH SUNDAY.
WHILE SOME GUIDANCE IS HINTING AT A STORM FORCE BARRIER JET...IT
WAS DECIDED TO TREND UPWARD FROM THE PREVIOUS FORECAST TO MAX
GALES (45 KNOT WINDS) FOR THE TIME BEING AS THERE IS PLENTY OF
TIME AVAILABLE TO IRON OUT DETAILS. MOST OF THE PRECIPITATION
ASSOCIATED WITH THIS LOW WILL BE CONFINED TO THE GULF COAST AND
IMMEDIATE INLAND AREAS...BUT SHOWERS SPREADING INTO INTERIOR
PORTIONS OF SOUTHCENTRAL ALASKA CANNOT BE RULED OUT. ONE OTHER
AREA OF CONCERN THAT WILL NEED TO BE MONITORED WILL BE THE
POTENTIAL FOR SOME FREEZING RAIN FOR INLAND AREAS OF SOUTHCENTRAL
ALASKA LATE SATURDAY AND AGAIN ON SUNDAY. OVERNIGHT TEMPERATURES
ARE EXPECTED TO BE BELOW FREEZING WITH HIGH TEMPERATURES WARMING
TO JUST ABOVE FREEZING. WITH THE TRACK OF THE LOW...WARMER AIR
ALOFT WILL BE ADVECTED NORTHWARD FROM THE NORTH PACIFIC AND
POTENTIALLY CREATE A "WARM NOSE" WITH 925 MB TEMPERATURES ABOVE
FREEZING. THIS WOULD POTENTIALLY LEAD TO A BRIEF PERIOD OF FREEZING
RAIN BEFORE THE ATMOSPHERE "WET BULBS" AND PRECIPITATION CHANGES
OVER TO SNOW. AS MENTIONED EARLIER...THIS IS ONLY SPECULATIVE AND
SUBJECT TO CHANGE AS MORE INFORMATION BECOMES AVAILABLE IN THE
COMING DAYS.

OVER THE BERING SEA AND ALEUTIAN ISLANDS...A FRONT ASSOCIATED WITH
AN AREA OF LOW PRESSURE JUST OFF THE COAST OF KAMCHATKA WILL PUSH
ACROSS THE BERING SEA OVER THE WEEKEND. AN AREA OF LOW PRESSURE
WILL DEVELOP ALONG THIS FRONT (TRIPLE POINT LOW) AND PUSH INTO THE
CENTRAL BERING SEAS ON SUNDAY. BY THIS POINT...A VERY BROAD TROUGH
OF LOW PRESSURE WILL ENCOMPASS THE BERING SEA AND MUCH OF
SOUTHCENTRAL ALASKA. MULTIPLE LOW CENTERS WILL BE EMBEDDED WITHIN
THIS TROUGH BUT IT IS JUST TOO FAR OUT TO EVEN ATTEMPT TO GUESS
WHERE THESE CENTERS MIGHT DEVELOP/TRACK. REGARDLESS...AN UNSETTLED
PERIOD OF WEATHER WITH SCATTERED RAIN AND SNOW SHOWERS SHOULD
CONTINUE INTO NEXT WEEK.

ONE LAST THING OF NOTE...THE BLOCKING HIGH OVER THE ARCTIC APPEARS
TO FINALLY START SHOWING SIGNS OF WEAKENING AND SHIFTING WESTWARD
BY TUESDAY OF NEXT WEEK. THIS COULD BE THE FIRST INDICATION OF A
MUCH DESIRED PATTERN CHANGE. STAY TUNED IN THE COMING DAYS FOR
MORE DETAILS.

&&

.AFC WATCHES/WARNINGS/ADVISORIES...
PUBLIC...DENSE FOG ADVISORY...101 111.
MARINE...GALE...177 178.
FIRE WEATHER...NONE.

&&

SYNOPSIS AND MODEL DISCUSSION...TP
SOUTHCENTRAL ALASKA...DK
SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...DEK
LONG TERM...MMC