textproduct: Fairbanks

SYNOPSIS

Cool and rainy conditons are expected to continue for the next couple of days over Western Alaska. Southerly flow will continue to result in more seasonable temperatures across the Interior through Thursday. The extent of the southerly flow reaches north of the Brooks Range, resulting in a Heat Advisory for the Arctic Plains that will be in effect through Thursday afternoon. Thunderstorm chances look to return across the Eastern Interior and Central Brooks Range on Thursday. Another low is expected to move out of Siberia and move toward the Aleutians by the start of the weekend. This could bring another round of showers for the southern portions of the West Coast through the end of the weekend.

KEY WEATHER MESSAGES

Central and Eastern Interior... - Warm and dry conditions expected to continue across the Interior today and Thursday with highs in the upper 70s. This will be followed by a slight and brief cooling trend before temperatures warm back to the mid to upper 70s by the end of the weekend.

- Isolated to scattered thunderstorms possible across the Eastern Interior Thursday and Friday. Better chance and coverage expected on Thursday.

- Showers from the West Coast shift east over the Central Interior on Thursday and Friday. Heaviest amounts expected on the south side of the Central Brooks Range.

West Coast and Western Interior... - Gusty southerly winds slowly diminish Wednesday night into Thursday.

- Widespread showers continuing across the West Coast and Western Interior with additional totals between 0.15" and 0.5" through Thursday night.

- Heavier rainfall amounts, up to 1", possible along southern portions of the western Brooks Range, Nulato Hills, and northern Norton Sound coast.

- Slight warming trend possible over the Western Interior by the start of the weekend ahead of another low potentially moving into the Bering Sea bringing more rain showers and cooler temperatures across the region.

North Slope and Brooks Range.. - Above seasonable normal temperatures will continue across the North Slope as the Arctic Plains will be in the mid 70s and even near 80 on Thursday. The Arctic Coastline will be in the upper 50s to low 60s.

- Rain showers expected to continue across the western Brooks Range tonight into Thursday. Isolated thunderstorm chances return Thursday afternoon.

- Cooler and wetter conditions expected to continue through he end of the week into the start of the weekend.

FORECAST ANALYSIS AND DISCUSSION

Satellite imagery from this afternoon shows the 545 decameter low continuing to spin over the western portion of the Seward Peninsula. The associated front with this system has provided a good portion of the West Coast and Western Interior with wetting rains between 1" and 3" over the past couple of days. The heaviest amounts have been seen in and around the Norton Sound as well as the YK-Delta. Meanwhile, ridging continues along the Al-Can boarder. Both this and the trough out west helps to set up southerly flow across the state.

The low over the Seward Peninsula is not expected to progress much over the next day or so, which will allow for rainy conditions to continue across Western Alaska. With the southerly flow, downsloping conditions are expected across the Interior and central portions of the Arctic Plains. This will result in temperatures around the seasonal normal for the Interior, and temperatures above normal for the Arctic Plains. A heat advisory has been issued for the Arctic Plains for temperatures as high as 80 degrees through Thursday afternoon. As Thursday rolls around, a shortwave will be riding up the southerly flow along the Al-Can boarder. This will bring back the thunderstorm chances across the Eastern Interior. Latest guidance is showing the best potential for thunderstorms to be between Eagle and Fort Yukon. However, a few strikes cannot be ruled out over the Fortymile Country, the Upper Tanana, and the Central/Eastern Brooks Range.

Thursday night into Friday, another low will begin to shift E/SE out of Siberia. This will shift the low over the Seward Peninsula to shift to the NE. This will allow for the scattered rain showers to shift east, bringing back more mild temperatures along with it. Some thunderstorms may also be possible along the Al-Can Boarder Friday afternoon. This will also allow for upslope showers to continue along the southern portions of the Brooks Range through the end of the week. There are some discrepancies seen amongst the models with the positioning of the upper-level low. The GFS is the outlier, having the low situated over the central Brooks Range by Friday afternoon while the others have it over the Central Arctic coastline. While this isn't expected to have much of an impact on the short-term forecast, it could lead to various outcomes in the long-term.

By the start of the weekend, the low from Siberia will continue to move south along the Bering, tracking towards the Aleutians. This is expected to bring another round of widespread precipitation across the southern portions of Western Alaska. There is still some uncertainty on where the heaviest precipitation occurs as some subtle ridge out ahead of the low could keep it farther west.

FIRE WEATHER

Ridging continues over eastern Alaska as a low slowly weakens in the Bering Strait. As a result, winds are generally southerly across the West Coast and over the Brooks Range with showers in the West and warm and dry weather in the Interior and North Slope. Max temperatures in the Interior will be in the mid to upper 70s through Thursday afternoon. Relative humidity will bottom out in the 30 to 40 percent range for most of the Interior, except in the upper Tanana Valley where it will get as low as the 20s. Focus has been on the southeast Interior, but the central Arctic Plains also has a few days of warm and dry weather as well until this pattern shifts.

This pattern will begin to break down on Thursday. While it will continue to be warmer and drier east and cooler and wetter out west, isolated thunderstorms will develop in the Interior and North Slope as the ridge over eastern Alaska erodes. Thunderstorms are most likely to develop in the higher terrain north of the Tanana valley and up along the AlCan border, as well as in the Central and Eastern Brooks Range. An area of scattered thunderstorms is expected from Eagle towards Fort Yukon. Although storms should stay north of the Tanana Valley, the recent stretch of warm and dry weather in most of the Interior and North Slope provides some cause for concern. After Thursday, thunderstorm coverage shifts east placing the best area for development along or across the AlCan Border.

Friday, conditions will cool slightly in the Central Interior as low pressure moves to the northeast over the area, providing cloud cover and light showers. The Upper Tanana Valley and Fortymile Country will continue to see similar hot and dry weather. This weekend, more potential rain for West Coast, although smaller amounts than the recent downpour and it likely won't reach as far inland.

HYDROLOGY

The heavy rainfall expected over the southern portions of the western Brooks Range have resulted in accumulations equivalent to a 2 to 5 year return interval. While flooding is not expected at this time, there will be significant rises in smaller streams and rivers and a slow to moderate rise on the Kobuk River.

EXTENDED FORECAST DAYS 4-7

Starting off with the low moving toward the Aleutians, the GFS is the outlier amongst the models having the system farther west and slightly weaker. If this were to pan out, it could lead to lighter rainfall amounts across the West Coast through the end of the weekend. Drawing our attention back to the low over NE Alaska, various outcomes are possible with the various patterns seen between the models. As previously mentioned, the GFS keeps the low further south. This would allow for some energy from the Arctic to wrap into the low, resulting in broad troughing across Eastern Alaska. Meanwhile, the ECMWF and CMC have the low shifted farther to the NE, which would allow for higher pressure to build back in across the Interior which could lead to another warming/drying trend. While the forecast right now favors more toward the solution being shown by the ECMWF and CMC, this will be watched closely over the next several days to see the pattern transpires.

Coastal Hazard Potential...None

AFG WATCHES/WARNINGS/ADVISORIES

AK...Heat Advisory for AKZ806-808. PK...Small Craft Advisory for PKZ804-805-807>810-852-855-856.