Sugar Mountain

Forecast Discussion

Summary

SYNOPSIS

... Cool high pressure will build in from the north today, settling along the East Coast through Wednesday. The high will shift east on Thursday, allowing a gradual warming trend through the end of the work week. The next cold front is expected to push into the area late this weekend.

NEAR TERM /THROUGH TONIGHT/... As of 1035 AM EDT Tuesday: Tricky forecast this morning with cloudy and cool conditions across portions of the area and breaks in the clouds with warmer conditions elsewhere. Expect clouds to move in across all the area but breaks to develop across the piedmont as drier air works in for the afternoon. Temps should overall be warmer across the southwest where early breaks and some sun were seen then cooler across the northeast with the early clouds and lower thickness values. Expect some light showers to develop along the escarpment in the lingering low level moisture and easterly flow. Scattered showers expected this afternoon over the southwestern mountains where some low level convergence develops along or near the wedge boundary.

Otherwise, the shortwave that brought the rain yesterday pushed through overnight, but a secondary shortwave diving down the MO Valley this morning will drop into the Southeast tonight. Surface moisture leftover from the rain has allowed some patches of fog to form, and have seen some improvement in visibilities in the mountain valleys, but the Piedmont is still seeing some patchy dense fog. Will re-issue the SPS, but adjust the wording to concentrate on the Piedmont.

Strong (1033+mb) surface high over the Great Lakes will continue to slide east, and already seeing signs of the damming onset as the wedge front drops through VA toward NC. This will continue through the morning hours, and with the onset of damming will come some gusty NE winds. Low-level moisture will continue this morning, but should see some peeks of sunshine into the afternoon. Nevertheless, the CAA will be pretty strong, and high temperatures today are expected to be 10-15 degrees cooler than those yesterday. Some bust potential especially across the Upstate and NE GA depending on if the wedge front's progress stalls or more breaks develop in the clouds, but by and large pretty constant mid to upper 50s. The secondary shortwave combined with the upslope low-level flow from the damming will allow showery activity to persist across the mountains, diminishing from north to south during the day as the shortwave pushes further southeast toward FL.

Cool northeasterly low-level flow will continue tonight, though no longer really damming just based on the progression of the surface high and unfavorable upper pattern. Clearing will be slow over the SW mountains, but plenty of stars coming out elsewhere tonight, and lows will drop a good 5-7 degrees below normal, with a hard freeze in the mountains and flirting with freezing across the NW NC Piedmont.

SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/... As of 300 AM Tuesday: The short term period will be quiet, with a relatively cool and dry high pressure sprawling along the eastern seaboard under a flat upper ridge. This will keep a persistent, dry NE flow atop the CWFA on Wednesday, weakening and turning out of the SW on Thursday. Temps will start out about 5-10 deg below normal Wednesday and Wednesday night, and warm to near normal Thursday thru Thursday night. Skies should be clear or mostly clear, with some increase in cirrus on Thursday. Low dewpts and moderating temps will combine to produce critical RH values Wed aftn, and possibly in spots Thu aftn, as well. This may be a concern for fire wx. Winds are expected to be light.

LONG TERM /FRIDAY THROUGH MONDAY/... As of 315 AM Tuesday: Quiet weather will continue into the extended period with a nice warming trend. Sfc high pres will shift east of the area, bringing a strengthening return flow atop the CWFA for Friday and Saturday. There will also be an increase in clouds, but precip chances don't really start ramping up until late Saturday, as a low pressure system organizes over the Plains. Temps will be about 5 deg above normal Friday, and 5-10 deg above normal Saturday.

The 00z medium range guidance still in disagreement on the handling of energy that breaks off from a digging upper trough over the Upper Midwest. The orphaned energy is expected to close into an upper low over the Four Corners region, then get picked up within the northern stream westerlies late in the weekend. The initial trough will bring a cold front thru the area, most likely during the day on Sunday. The 00z EC continues to show this as a clean fropa, with dry high pres building in by early Monday. The 00z GFS shows much more moisture and energy with the southern stream wave, bringing upglide and precip atop a hybrid CAD Sunday night thru Monday. The air mass might even be cold enough for p-type concerns in the northern mountains, but most other guidance doesn't have this. So I opted not to make much change from previous fcst, with PoPs ramping up Saturday night, peaking Sunday, then slowly decreasing to slight chc to low-end chc Monday. With the passage of the front, whether or not we have CAD, temps should cool back to slightly below normal to start next week.