Small Craft Advisory 38, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
200 PM AKST SAT JAN 12 2013

.MODEL DISCUSSION...
MODELS ARE DECENT WITH TIMING AND TRACK OF FEATURES THROUGH ABOUT 36
HOURS BEFORE SHOWING SOME SIGNIFICANT DIFFERENCES. GFS SEEMS TO HAVE
INITIALIZED THE BEST WITH THE TEMPERATURES THAT ARE CLOSEST TO
SURFACE OBSERVATIONS. ECMWF HAS DONE DECENTLY AS WELL ALTHOUGH THERE
ARE SOME LOCATIONS THAT ARE SEVERAL DEGREES COLDER OR WARMER THAN
WHAT THE MODEL SHOWS. THE NAM HAS BEEN RULED AN OUTLIER IN
TRACK/POSITION BUT ALSO WITH ITS TYPICAL COLD BIAS WITH TEMPERATURES.
THE GFS WILL BE USED FOR THE FIRST 36 HOURS AND THEN ECMWF IS
PREFERRED DURING THE TIME WITH MORE INCONSISTENCY.

.ANALYSIS AND UPPER LEVELS...
THE MAIN FEATURES ON THE AREA WEATHER MAP TODAY INCLUDE A LARGE UPPER
RIDGE OVER THE EASTERN PACIFIC THAT IS VERY SLOWLY MOVING
EASTWARD...AND A LARGE LOW SLIDING NORTHEASTWARD ALONG THE BACK SIDE
OF THE RIDGE. THIS LOW IS BRINGING WIDESPREAD PRECIPITATION AND MUCH
ABOVE NORMAL TEMPERATURES TO THE SOUTHERN HALF OF ALASKA THIS
WEEKEND. PRECIPITATION IS GENERALLY STARTING AS SNOW BUT CHANGING TO
RAIN AS WARM AIR SURGES IN. THERE HAVE BEEN PERIODS OF FREEZING RAIN
DURING THE TRANSITION TIME...AND THAT WILL CONTINUE AS THE LOW
CONTINUES NORTHEASTWARD.

.SHORT TERM FORECAST...
THE SURFACE LOW WILL CONTINUE MOVING NORTHWARD PAST THE BERING STRAIT
TONIGHT. A WEAKER LOW WILL MOVE NORTH ON THE FRONT INTO THE
NORTHWESTERN MAINLAND ON MONDAY. WARM AIR WILL CONTINUE TO SURGE
NORTHWARD INTO THE SOUTHERN MAINLAND AS A LONG FETCH OF MOISTURE FROM
ABOUT 30 DEGREES N LATITUDE GRADUALLY SHIFTS EASTWARD OVER THE NEXT
COUPLE DAYS. THE AMOUNT OF MOISTURE WITH THIS SYSTEM ALONG WITH THE
WARM TEMPERATURES WILL HAVE A GREAT AFFECT ON SNOW PACK ACROSS THE
AREA...AND WITH FROZEN GROUND AS WELL THE WATER WILL HAVE A HARD TIME
FINDING SOMEWHERE TO GO. THEREFORE THE FLOOD WATCHES IN EFFECT STILL
LOOK VERY REASONABLE AND WE WILL CONTINUE THEM.

CURRENT ADVISORIES ALSO APPEAR TO BE IN GOOD SHAPE. WARM AIR IS
ALREADY MOVING OVER THE SOUTHERN PART OF THE STATE AT THE
MID-LEVELS...BUT MANY SURFACE TEMPERATURES REMAIN BELOW FREEZING.
IT WILL NOT TAKE MUCH FREEZING RAIN AT ALL TO CAUSE TRAVEL
PROBLEMS...AND EVEN ONCE AIR TEMPERATURES CLIMB ABOVE
FREEZING...SURFACES WILL REMAIN BELOW FREEZING AND CAUSE THE RAIN TO
FREEZE ON THOSE SURFACES. SO ALL ADVISORIES WILL REMAIN AS-IS AT THIS
POINT AS WELL.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...FLOOD WATCH 101 111 121 125 131 135 145.
MARINE...GALE WARNING 120 130 132 138 150 155 160 165 170 171 172 180
         185 351 352 412 413 414.
         HEAVY FREEZING SPRAY 185.
FIRE WEATHER...NONE.