textproduct: Caribou

WHAT HAS CHANGED

Update 645 PM

- Updated aviation section to reflect 00Z TAFs

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-Increased precip chances for Saturday afternoon as the front moves in, possibly creating convective showers.

-Increased precip chances through Thursday with cold front passage early Thursday morning.

KEY MESSAGES

1) A strong cold front will bring rain and snow showers and strong gusty winds Saturday afternoon. Wind impacts and convective showers could reduce visibilities for afternoon travel.

2) Bitter cold Arctic air will surge into the region Saturday night into Sunday bringing frigid wind chills, the risk of hypothermia, and patches of black ice on roads.

3) Snow will continue to accumulate across the area into this evening, impacting the evening commute.

DISCUSSION

KEY MESSAGE 1...A strong cold front will bring rain and snow showers and strong gusty winds Saturday afternoon. Wind impacts and convective showers could reduce visibilities for afternoon travel.

KEY MESSAGE 1 DESCRIPTION... Low pressure tracking into Central Quebec combined with high pressure dropping south into the Plains will push a strong Arctic cold front toward the area on Saturday. There are a couple of parameters to discuss about this front. First, the warm front stretching well to the north will bring S flow and warm air into the region. Temps are expected to reach well above normal for Saturday causing some of the snow pack to melt. Second, the LLJ and tightening pressure gradients ahead of the front will create gusty S winds for the day. Third, ingredients for instability are becoming more prevalent as new models come into the forecast. Convective showers are expected in the afternoon with some decreasing visibility.

KEY MESSAGE 2...Bitter cold Arctic air will surge into the region Saturday night into Sunday bringing frigid wind chills, the risk of hypothermia, and patches of black ice on roads.

KEY MESSAGE 2 DESCRIPTION... Arctic air will surge into the area behind the cold front Saturday night into Sunday. Any rainfall or snow/ ice melt on roads from warmer temperature on Saturday could quickly freeze Saturday night as temperatures fall. By Sunday morning temperatures will have dropped to around zero in the northwest and 20 along the coast, only to rise into the mid teens north and near 30 Downeast Sunday afternoon. The coldest temperatures will come Sunday night as high pressure begins to build over the region. Lows by Monday morning will range from ten to twenty below in the northwest to near zero by the coast. A light westerly breeze Monday morning will combine with the frigid temperatures to produce wind chills down to the mid 20s below across the north Sunday morning and the teens below over parts of Downeast. This will be followed by highs Monday from the low teens over the far north to the upper teens by the coast, which will be about 15 degrees below normal.

KEY MESSAGE 3... Snow will continue to accumulate across the area into this evening, impacting the evening commute.

KEY MESSAGE 3 DESCRIPTION... As occluded low pressure south of the Hudson Bay continues to move northeast and pass north of the forecast area, a warm front will continue to lift across our forecast area late this afternoon through this evening. This warm front will continue to support snow throughout the forecast area, and may even lead to rain mixing in along the coast briefly before temperatures begin to drop once more and precip type switches back over to snow. Some instability exists this afternoon, with steep low level lapse rates of around 8 C/km and weak CAPE. That said, a strong inversion aloft will limit the full potential of any convection, and weaker upper level winds will limit any squall potential. However, briefly heavy snow showers are possible through this evening, which could rapidly drop visibilities with sudden brief whiteout conditions quite possible.

Snow showers could continue through the night tonight within the warm sector of the passing low pressure system, with the most likely area to see continued snow showers being the northern half of the forecast area. By daybreak on Thursday, the cold front will cross the forecast area, amplifying the snow shower threat across the forecast area, and another up to an inch of snow is possible with this frontal passage.

AVIATION /00Z THURSDAY THROUGH MONDAY/

Tonight...MVFR/IFR in sct -shsn. S wind around 5 kt. LLWS early this evening N.

Thursday...MVFR/IFR early, improving to VFR. W winds 5 to 10 kt with gusts to 20 kts.

Thursday night...VFR with SKC at all terminals. Winds gradually decreasing, eventually becoming light and variable.

Friday...VFR. W wind around 5 kt.

Friday night...VFR dropping to IFR south late, and dropping to MVFR over the north late. S wind 5 kt increasing to 5 to 10 kt late.

Saturday...MVFR becoming IFR in snow showers north. VFR south. S wind 10-15 kts with gusts up to 30 kts.

Saturday night...VFR. W wind 5 to 10 kt.

Sunday-Monday...VFR. NW wind around 10 kt.

MARINE

Small craft advisory conditions continue tonight through Thursday on the outerwaters, with winds gusting 25 to 30 kts and seas 5 to 7 ft. Conditions will further improve Thursday night, falling below advisory criteria across all marine zones. Light freezing spray may build in late Thursday night.

A SCA will be needed late Friday night into Saturday evening for S winds gusting up to 30 kt. A SCA and possibly a gale will likely be needed late Sunday through Sunday night for NW winds gusting up to 30 to 35 kt. Moderate freezing spray is likely Sunday night into Monday morning. Seas 5 ft Thursday night dropping to 4 ft Friday, then rising to 5 ft Friday night and 7 ft on Saturday in response to the southerly. Seas dropping back to 4 ft by early Sunday morning.

CAR WATCHES/WARNINGS/ADVISORIES

ME...None. MARINE...Small Craft Advisory until 7 PM EST Thursday for ANZ050-051.