Flash Flood Warning 1, NWS Anchorage, AK

AREA FORECAST DISCUSSION
SOUTHCENTRAL AND SOUTHWEST ALASKA
400 PM AKDT SUN MAR 22 2009

.ANALYSIS AND UPPER LEVELS...
IN THE UPPER LEVELS...BROAD CYCLONIC FLOW CONTINUES OVER MOST OF
ALASKA AND THE BERING SEA...WITH A LARGE UPPER LOW LOCATED OVER THE
SOUTHWEST MAINLAND. THE BLOCKING RIDGE OVER NORTHEAST SIBERIA REMAINS
FIRMLY ENTRENCHED.

AT THE SURFACE...THE LOW RESPONSIBLE FOR SPREADING SNOW ACROSS
SOUTHCENTRAL ALASKA YESTERDAY AND TODAY IS DISSIPATING OVER THE KENAI
PENINSULA. A MORE ROBUST 988 MB LOW IS EVIDENT ON SATELLITE AND WATER
VAPOR IMAGERY OVER THE CENTRAL GULF OF ALASKA. ELSEWHERE...HIGH
PRESSURE IS BUILDING INTO THE WESTERN ALEUTIANS AND BERING SEA.

.MODEL DISCUSSION...
MODELS CONTINUE TO BE IN GOOD AGREEMENT DESPITE A PATTERN THAT CAN
CAUSE GUIDANCE TROUBLES. MAIN DIFFERENCES ARISE REGARDING LOW
EVOLUTION AND POSITIONS AS USUAL...BUT THE GENERAL SOLUTION AMONGST
THE MODELS REMAINS THE SAME THROUGH WEDNESDAY.

.SHORT TERM FORECAST...
.SOUTHCENTRAL...
THE PRIMARY CONCERN OVER THE NEXT SEVERAL DAYS IS THE LOW OVER THE
GULF OF ALASKA. THIS LOW IS EXPECTED TO CURVE NORTH...AND BE JUST
EAST OF KODIAK ISLAND ON MONDAY. GIVEN THE MORE SOUTHERLY AND
EASTERLY TRACK THAN EARLIER ANTICIPATED...PRECIPITATION WILL BE
RESTRICTED PRIMARILY TO THE COAST. MOISTURE WILL BE OVERSPREADING
THESE AREAS THROUGH TONIGHT...WITH WIDESPREAD GALES OVER MARINE
WATERS. A WINTER WEATHER ADVISORY FOR SNOW HAS BEEN ISSUED FOR KODIAK
ISLAND...SINCE COLD AIR WILL BE IN PLACE AND ABUNDANT MOISTURE IS
ANTICIPATED. DEPENDING ON THE EXACT LOW TRACK THE POTENTIAL FOR
BLIZZARD CONDITIONS IN KODIAK WILL NEED TO BE MONITORED. AS THE LOW
PULLS EAST AND DISSIPATES ON TUESDAY...PRECIP WILL BE DIMINISHING
ALTHOUGH WINDS WILL REMAIN STRONG ON THE BACKSIDE. AT THIS TIME
EXPECT STORM FORCE WINDS OVER EASTERN PORTIONS OF THE GULF DUE TO
COLD AIR ADVECTION. ANOTHER NORTH PACIFIC LOW WILL BEGIN SPREADING
MOISTURE BACK INTO SOUTHCENTRAL BY TUESDAY NIGHT.

.SOUTHWEST...
THE AFOREMENTIONED GULF LOW WILL SPREAD MOISTURE OVER THE AREA
TONIGHT WITH SNOW SHOWERS MOST WIDESPREAD OVER THE AKPEN AND BRISTOL
BAY. NORTHERLY FLOW ON THE BACKSIDE OF THE LOW WILL KEEP WINDS BRISK
AND TEMPERATURES BELOW NORMAL. WARMER AIR AND ANOTHER SURGE OF
MOISTURE WILL MOVE IN LATE TUESDAY AS A NORTH PACIFIC LOW MOVES
NORTHEAST INTO THE GULF.

.BERING SEA AND ALEUTIANS...
BRISK NORTHERLY FLOW AND SCATTERED SNOW SHOWERS WILL CONTINUE OVER
THE ALEUTIANS AND PRIBILOFS THROUGH TUESDAY AS HIGH PRESSURE BUILDS
OVER THE WESTERN BERING SEA. THE PRESSURE GRADIENT WILL BE TIGHTENING
TUESDAY AS A NORTH PACIFIC LOW APPROACHES THE EASTERN ISLANDS. AS A
RESULT...PRECIPITATION AND WINDS WILL BE INCREASING MAINLY OVER THE
CENTRAL AND EASTERN ISLANDS THROUGHOUT THE DAY ON TUESDAY.

.LONG TERM FORECAST...
THE SIBERIAN BLOCK WILL RETROGRADE SLOWLY THROUGH THE LONG
TERM...ALTHOUGH IT WILL REMAIN IN TACT THROUGH THE PERIOD. THE LARGE
UPPER LOW WILL REMAIN OVER THE BRISTOL BAY AREA...WITH VARIOUS
IMBEDDED IMPULSES. AS A RESULT...EXPECT A SERIES OF SURFACE
DISTURBANCES TO AFFECT SOUTHERN ALASKA AS WE HEAD INTO NEXT WEEKEND.

.AER/ALU...WATCH/WARNING SUMMARY
PUBLIC...WINTER WEATHER ADVISORY 171
MARINE...GALE WARNING 120 130 132 140 150 351 352
         HEAVY FREEZING SPRAY 150 155 165 179 412 414
FIRE WEATHER...NONE

NRH MAR 09