Prognostic Meteorological Discussion
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FXAK02 KWNH 231901
PMDAK

ALASKA EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
300 PM EDT SAT JUL 23 2016

VALID 12Z WED JUL 27 2016 - 12Z SUN JUL 31 2016

...HEAVY RAIN POTENTIAL FOR SRN/SERN AK MIDWEEK AND THE INTERIOR
MID-LATER NEXT WEEK...

...GUIDANCE/UNCERTAINTY ASSESSMENT AND WEATHER PATTERN
HIGHLIGHTS/THREATS...

THE WPC MEDIUM RANGE PRODUCT SUITE WAS PRIMARILY DERIVED FROM A
BLEND OF THE COMPATABLE 12 UTC GFS AND 00/12 UTC ECMWF RUNS ALONG
WITH 00 UTC NAEFS/ECMWF ENSEMBLES DAY4/WED BEFORE TRANSITIONING
DAY5/THU TO JUST THESE ENSEMBLE MEANS THEREAFTER CONSISTENT WITH
INCREASING FORECAST SPREAD. THIS SOLUTION MAINTAINS GOOD WPC
CONTINUITY.

AN AMPLIFIED CLOSED LOW/TROUGH IS EXPECTED TO TRACK NEWD OVER THE
GULF OF AK WED/THU IN A PATTERN WITH ABOVE NORMAL PREDICTABILITY
AND CONTINUITY. THIS WILL SUPPORT SIGNIFICANT LOWER ATMOSPHERIC
LOW/FRONTAL DEVELOPMENT TO PROVIDE FOCUS FOR HEAVY WIND/WAVES AND
LEAD/WRAPPED HEAVY RAINFALL WITH MAX POTENTIAL INLAND INTO FAVORED
COASTAL TERRAIN OF SRN/SERN AK AS FUELED BY A PRECIPITATBLE WATER
PLUME UPWARDS TO 1-1.25". THE SUBSEQUENT SRN TIER SYSTEM ENERGY
PATTERN IN THE WAKE OF THIS LOW SEEMS LESS AMPLIFIED/ORGANIZED IN
MORE PROGRESSIVE FLOW UNDERNEATH AN INCREASINGLY DOMINANT ARCTIC
TO WRN/NRN AK MID-UPPER LEVEL TROUGH. THIS AMPLIFYING NRN STREAM
SYSTEM WOULD SUPPORT AN ANOMOLOUSLY WELL DEFINED MID-SUMMER
FRONTAL PASSAGE GRADUALLY ACROSS THE INTERIOR. THIS WOULD LEAD TO
SOME POTENTIALLY HEAVY CONVECTION/RAINFALL AS FUELED BY DYNAMICS
ALOFT AND FAVORABLE SWRLY INFLOW WITH ABOUT 1" PRECIPIATBLE WATER
VALUES FROM THE BERING SEA IN ADDITION TO WIDESPREAD UNSETTLED
WEATHER/POST-FRONTAL COOLING WED THROUGH NEXT WEEKEND. FORECAST
SPREAD WITH THIS SYSTEM HAS DECREASED SOME IN RECENT GUIDANCE TO
BOLSTER PREDICTABILITY TO NEAR AVERAGE LEVELS.

SCHICHTEL

$$





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