Heavy Freezing Spray Warning 162, NWS Anchorage, AK

SOUTHCENTRAL AND SOUTHWEST ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ANCHORAGE AK
1245 PM AKDT WED MAY 2 2012

.ANALYSIS AND UPPER LEVELS...COLD UPPER LEVEL LOW OVER INTERIOR
ALASKA IS BEGINNING TO RETROGRADE WESTWARD WHILE THE TROUGH AXIS
EXTENDING FROM THIS LOW LIFTS NORTHEASTWARD THROUGH THE COPPER
RIVER BASIN. SNOW CONTINUES OVER THE EASTERN PORTION OF THE BASIN...
BUT WILL BREAK UP INTO SHOWERS AS THE TROUGH EXITS THIS AFTERNOON.
CLEAR SKIES AND CHILLY TEMPERATURES DOMINATE SOUTHCENTRAL BEHIND
THE TROUGH. A SURFACE LOW OVER THE NORTHEAST GULF IS MAINTAINING
A TIGHT PRESSURE GRADIENT ALONG THE GULF COAST...SO GUSTY WINDS
CONTINUE THROUGH CHANNELED AREAS THIS MORNING. A NEARLY ZONAL
UPPER LEVEL JET EXTENDS FROM KAMCHATKA ACROSS THE BERING SEA
BEFORE BENDING SOUTHEASTWARD INTO THE NORTHEAST PACIFIC. MULTIPLE
WEAK UPPER WAVES ALONG WITH A COUPLE WEAK SURFACE LOWS ARE TRACKING
RAPIDLY EASTWARD ACROSS THE BERING REGION TO SOUTHWEST ALASKA
PRODUCING AREAS OF RAIN AND SNOW.

.MODEL DISCUSSION...MODELS ARE IN FAIRLY GOOD AGREEMENT WITH
SYNOPTIC SCALE FEATURES. THERE ARE MINOR DIFFERENCES IN SMALLER
SCALE FEATURES. NO SINGLE MODEL IS PARTICULARLY FAVORED OVER
ANOTHER. THE GUIDANCE WILL BE USED AS A WHOLE TO GUIDE MINOR
CHANGES TO THE EXISTING FORECAST.

.SHORT TERM FORECAST...

SOUTHCENTRAL ALASKA...UPPER LOW OVER INTERIOR ALASKA WILL CONTINUE
TO RETROGRADE WESTWARD TONIGHT AND THURSDAY AND THEN DIVE SOUTHWARD
ACROSS THE BERING SEA FRIDAY. WEAK UPPER WAVES CROSSING THE BERING
SEA IN THE STRONG WESTERLIES WILL PASS UNDERNEATH THIS LOW AND THEN
LIFT NORTHEASTWARD TOWARD SOUTHCENTRAL AS THE LOW MOVES SOUTH.
THEREFORE...EXPECT INCREASING MOISTURE ACROSS THE REGION THURSDAY
AND FRIDAY. LOW LEVELS WILL WARM UP AS SOUTHERLY FLOW DEVELOPS
WHILE UPPER LEVELS WILL REMAIN QUITE COLD. THEREFORE...INSTABILITY
WILL INCREASE AND LEAD TO DIURNAL SHOWERS FOCUSED OVER AND ALONG
THE MOUNTAINS. A SLIGHTLY STRONGER SHORT-WAVE COMBINED WITH A LOW
LEVEL FRONT WILL MOVE INTO THE WESTERN GULF THURSDAY AFTERNOON AND
TRACK TO THE NORTH GULF COAST FRIDAY AFTERNOON RESULTING IN STEADY
RAIN ALONG THE COAST. MODELS THEN INDICATE ANOTHER STRONGER FRONT
MOVING ACROSS THE GULF SATURDAY. ONCE AGAIN THE BULK OF RAIN SHOULD
REMAIN ALONG THE COAST. INLAND AREAS WILL LIKELY SEE A FEW BREAKS
OF SUN EACH DAY WHILE DIURNAL SHOWERS WILL BECOME A LITTLE MORE
WIDESPREAD AS WE HEAD INTO THE WEEKEND.

BERING SEA/SOUTHWEST ALASKA...A COUPLE UPPER WAVES OVER THE WESTERN
BERING WILL TRACK TO THE EASTERN BERING TONIGHT WHILE A SURFACE LOW
BECOMES A LITTLE MORE WELL DEFINED. THIS WILL BRING ANOTHER ROUND
OF PRECIP TO MUCH OF THE REGION. AS ALL OF THIS MOVES INTO THE GULF
ON THURSDAY THE UPPER LOW WILL BEGIN TO DIVE SOUTHWARD INTO THE
NORTHERN BERING. ARCTIC AIR WILL PLUNGE SOUTHWARD THURSDAY NIGHT
THROUGH FRIDAY NIGHT LEADING TO GUSTY NORTHERLIES AND SNOW SHOWERS.

.LONG TERM FORECAST...THE UPPER LOW WHICH DROPS SOUTHWARD ACROSS
THE BERING SEA WILL EVOLVE INTO A MUCH LARGER UPPER LEVEL CLOSED
LOW AS IT BOTTOMS OUT SOUTH OF KODIAK ISLAND OVER THE WEEKEND AND
THEN MOVES INTO THE GULF NEXT WEEK. MODELS CANNOT ADEQUATELY RESOLVE
INDIVIDUAL SHORT-WAVES WITHIN THE LARGER CYCLONIC CIRCULATION THIS
FAR OUT IN TIME. THEREFORE...FORECAST CONFIDENCE QUICKLY HEADS
DOWNHILL AS WE HEAD INTO NEXT WEEK. GENERALLY SPEAKING EXPECT A
COMBINATION OF THE UPPER LOW AND EMBEDDED FEATURES TO COMBINE WITH
ANYTHING THAT MAY BE PULLED NORTHWARD FROM THE EAST PACIFIC TO
PRODUCE A WET PATTERN ALONG THE GULF COAST AND ALASKA PENINSULA.
INLAND AREAS OF SOUTHCENTRAL AND SOUTHWEST ALASKA WILL LIKELY
SEE MORE OF A SHOWERY REGIME WITH INCREASED PROBABILITIES OF PRECIP
AS FEATURES MOVE THROUGH. RIDGING OUT AHEAD OF THE UPPER LOW WILL
BRING WARMER AIR UP ACROSS THE FAR EASTERN GULF AND THEN
NORTHWESTWARD INTO SOUTHCENTRAL. THUS...EXPECT ANY PRECIP THAT
DOES FALL TO BE PRIMARILY IN THE FORM OF RAIN. MEANWHILE...UPSTREAM
OF THE LOW CENTER COLD AIR WILL REMAIN IN PLACE ACROSS THE BERING
SEA. OTHER THAN A FEW SHOWERS AND GUSTY WINDS EXPECT BENIGN
CONDITIONS ACROSS MOST OF THE BERING AND ALEUTIANS AS A STRONG
RIDGE BUILDS OVER THE NORTHWEST PACIFIC AND WESTERN BERING.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...FLOOD ADVISORY 152 KUSKOKWIM RIVER AT SLEETMUTE.
MARINE...GALE WARNING...172.
FIRE WEATHER...NONE.

SEB MAY 12