Area Forecast Discussion
Issued by NWS Fairbanks, AK

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FXAK69 PAFG 302322
AFDAFG

NORTHERN ALASKA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE FAIRBANKS AK
322 PM AKDT TUE JUN 30 2015


.DISCUSSION...

THE MAIN EVENT FOR THIS FORECAST CYCLE WILL BE THE IMMINENT HEAVY
RAIN EPISODE OVER PARTS OF THE SOUTHEAST INTERIOR AND THE ALASKA
RANGE. THIS WILL BE DRIVEN BY A SHORT WAVE TROUGH EMERGING FROM A
LARGE SCALE CIRCULATION OVER THE GULF OF ALASKA. THE TROUGH
INITIALLY WILL EXPAND NORTHEASTWARD INTO THE SOUTHERN YUKON
TERRITORY TONIGHT...THEN SWING TOWARDS THE ALCAN BORDER IN ZONES
224-226 BY LATE WEDNESDAY NIGHT. THE MAIN UPPER LOW CENTER WILL
MOVE INTO THE SOUTHERN YUKON TERRITORY WED AFTERNOON...THEN
CONTINUE ON EASTWARD INTO NORTHWEST CANADA.

IN A RATHER BROAD SENSE...THE 12Z RUNS OF THE GFS AND NAM
CONTINUE TO BE IN REASONABLE AGREEMENT ON THE AREAS
OF HEAVY RAINFALL WHILE THE ECMWF PLACES THE HEAVIEST RAINFALL
MAXIMUM FARTHER TO THE WEST. WE PREFER THE GFS/NAM CONSENSUS
BASED ON ITS BETTER PERFORMANCE IN THE PREVIOUS RAINFALL
EVENT...AND REASONABLY GOOD AGREEMENT BETWEEN THE TWO MODELS AND
REASONABLY GOOD RUN TO RUN CONTINUITY. THERE ARE DIFFERENCES
BETWEEN THE TWO MODELS FOR RAINFALL AMOUNTS OVER ANY GIVEN AREA
FOR ANY GIVEN TIME PERIOD.

THE HEAVIEST 48 HOUR RAINFALL TOTALS THROUGH THURSDAY ARE EXPECTED
TO BE OVER THE UPPER YUKON VALLEY AND FORTYMILE COUNTRY NORTHWEST
OF THE TAYLOR HIGHWAY...MOST OF THE DELTANA ZONE...THE WESTERN
HALF OF THE EASTERN ALASKA RANGE/ZONE 226...AND FROM THE RAILBELT
AREA EASTWARD IN DENALI/ZONE 225. RAINFALL AMOUNTS IN THESE AREAS
ARE EXPECTED TO RANGE FROM 1 TO 2 INCHES...WITH LOCAL AMOUNTS UP
TO 3 INCHES IN ZONES 224 AND 226. LESSER RAINFALL AMOUNTS ARE
EXPECTED OVER THE REMAINDER OF ZONES 223-224-225-226. IN ZONE
222...RAINFALL TOTALS COULD RANGE FROM ABOUT 0.25 INCH JUST
SOUTHEAST OF EIELSON TO AROUND 1 INCH IN AREAS NEAR THE LOWER
SALCHA RIVER. LESSER RAINFALL AMOUNTS ARE EXPECTED OVER THE
REMAINDER OF ZONE 222. A SIGNIFICANT RISE IS EXPECTED TO OCCUR ON
THE SALCHA RIVER BUT WE ARE NOT EXPECTING IT TO REACH FLOOD STAGE
AT THIS TIME.

WE WILL ISSUE A FLOOD WATCH FOR THE GOODPASTER RIVER AND SMALL
STREAM FLOOD ADVISORIES FOR THE HEAVY RAIN AREAS IN ZONES
223-224-226 AND THE RAILBELT AREA EASTWARD IN ZONE 225.

ISOLATED THUNDERSTORMS ARE EXPECTED OVER MOST OF THE EASTERN
INTERIOR...EASTERN BROOKS RANGE...EASTERN INTERIOR ARCTIC
SLOPE...AND IN ZONE 227 THIS AFTERNOON AND EVENING.

FOR WEDNESDAY AFTERNOON AND EVENING...ISOLATED THUNDERSTORMS ARE
EXPECTED IN NORTHERN ZONE 224...EASTERN ZONE 222...AND EXTREME
EASTERN ZONE 220.

A SHORT WAVE TROUGH WILL MOVE EASTWARD ACROSS THE NORTHERN
ALASKA MAINLAND THURSDAY THROUGH FRIDAY...KEEPING TEMPERATURES
NEAR SEASONAL NORMALS. RAINFALL ASSOCIATED WITH THE SHORT
WAVE TROUGH WILL LIKELY BE LIMITED MAINLY TO AREAS NORTH OF
THE BROOKS RANGE CREST.

RECENT EXTENDED MODEL FORECASTS HAVE BEEN CHARACTERIZED BY LARGE
DIFFERENCES BETWEEN THE GFS AND ECMWF RUNS AND GENERALLY POOR RUN
TO RUN CONTINUITY. THIS BEING SAID...THE ENSEMBLE MEANS ARE
PREFERRED FOR THE LONGER RANGE PORTION OF THE FORECASTS.
A PERIOD OF VERY WARM WEATHER OVER MOST AREAS IS EXPECTED
SATURDAY THROUGH TUESDAY...WITH TEMPERATURES FALLING BACK TO
NEAR SEASONAL NORMALS TOWARD THE END OF NEXT WEEK.


COASTAL HAZARD POTENTIAL DAYS 3 AND 4...NONE

&&

.FIRE WEATHER...
NO RED FLAG CONDITIONS ARE EXPECTED. WIDESPREAD WETTING RAINS
ARE EXPECTED OVER MUCH OF THE SOUTHERN AND EASTERN INTERIOR
AND THE ALASKA RANGE.


&&

.HYDROLOGY...
SEE MAIN DISCUSSION.


&&

.AFG WATCHES/WARNINGS/ADVISORIES...

DENSE SMOKE ADVISORY FOR AKZ221.

SMALL CRAFT ADVISORY FOR PKZ210.

SMALL STREAM FLOOD ADVISORY FOR AKZ223-AKZ224-AKZ225-AKZ226.

FLOOD WATCH FOR THE GOODPASTER RIVER IN AKZ223-AKZ224.

&&

$$

RF JUN 15



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