Rain Chances Decrease for Saturday; Increases Wednesday

Written by on December 18, 2014 in Local Forecast Discussion, Severe Weather

Update: Light rain and some ice pellets have been reported across the state this morning. Moisture is more abundant than previous models had indicated and have adjusted forecast to reflect this change. Expect rain for the next couple of hours as the system to the south moves offshore.

High temperatures for today reached low 50s with mostly sunny skies throughout. Mid-level clouds are moving in this evening and will continue to roll through that area tonight. Temperatures expected to drop into the low 30s tonight despite increasing clouds.

Mid-level clouds moving into the region from the west this evening and should increase in coverage through tonight.

Mid-level clouds moving into the region from the west this evening and should increase in coverage through tonight.

Mid-levels dry out some in the early morning and will lead to mostly sunny skies for Friday. High pressure over the Great Lakes will slowly move eastward during the day. This will lead to high pressure ridges southeastward east of the mountains. This should allow high temperatures to reach the mid 50s by afternoon.

Saturday will be the beginning of active weather as we kick off with a surface low that will travel over the Gulf Coast states during the day. Previous model runs had a strengthening low as it pushed off the southeastern coast. The most recent model runs have backed off considerably showing a much weaker low which is forecast to push farther offshore than originally expected. Mid-level moisture will filter over the region on Saturday which will lead to mostly overcast skies across the area with a potential for rain mainly over the ENC early Saturday and coastal sections Saturday night. Forecast rainfall totals should be less than 0.10″. HPC has potential rainfall totals slightly higher along the NC/SC border though I don’t see these areas reaching over 0.10″ given the weak surface low. Low temperatures Saturday night expected to be in the upper 40s.

NAM forecast model shows very light, scattered rain across southern sections of ENC on Saturday.

NAM forecast model shows very light, scattered rain across southern sections of ENC on Saturday.

The weakening system will be pulling away from ENC Sunday with skies becoming mostly cloudy. Highs should top out in the mid 50s with lows in the mid 30s.

Upper-level trough and associated mid-level energy will interact with the stalled surface front off the southeast coast Sunday night leading to cyclogenesis over the Gulf of Mexico. This will produce a surface low that will track up the southeast coast Sunday night into Monday morning. Models showing bulk of precipitation reaching the area early Monday morning and exiting the region Monday night as lift associated with the low pushes farther away from the region.

There should be a small lull in the precipitation on Tuesday though isolated showers are not out of the question.

An upper-level trough will deepen across the central CONUS with a surface low developing over South Dakota/Nebraska on Monday night and move towards the Great Lakes region Tuesday. The upper-level trough becomes negatively tilted as the low becomes vertically stacked and stall. Mid-level energy will rotate through the base of the trough and induce a secondary surface low along the front. As the trough deepens even further on Tuesday, conditions ahead of the trough will become favorable for strong to potentially severe thunderstorms. Tuesday night as the upper-level trough approaches, instability will increase as CAPE values increase somewhat as well as increased low-level helicity and strong low-level jet. The main threat of storms will be late Tuesday night into early Wednesday morning.

Forecast 850mb winds (low level jet height) for Wednesday morning.

Forecast 850mb winds (low level jet height) for Wednesday morning.

Forecast CAPE values for Wednesday morning.

Forecast CAPE values for Wednesday morning.

Helicity values for Wednesday morning.

Helicity values for Wednesday morning.

The severe threat will diminish quickly after the passing of the cold front during Wednesay afternoon. Cold air comes crashing into the area with significant height falls as the upper-level trough crosses over the region. Temperatures will drop during the day Wednesday to the mid 40s during the day and dropping to the mid 30s overnight. Christmas day will be dry and cold as the upper-level trough and associated cold front move away from the region.

7 day forecast for ENC.

7 day forecast for ENC.

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