... Seasonably cool conditions are expected early this week. A couple of minor disturbances may bring light precipitation to some areas as they pass through. Temperatures will gradually warm Wednesday and Thursday ahead of the next cold front expected late in the week.
NEAR TERM /THROUGH MONDAY/... As of 650 PM: Main update for the 00Z TAF issuance along with minor adjustments made to temperatures/sky/winds to coincide with latest trends, as the rest of the near term forecast remains on track. Quiet conditions persist across the area attm, with temperatures in the mid 50s to low 60s and passing high clouds, beginning to infiltrate in from the west as seen from latest IR.
Previous discussion: The pattern becomes more progressive tonight and Monday as a strong short wave comes in from the w/nw to kick out the old upper low off the NC coast. The sensible weather will be fair and dry this evening as high pressure ridges down from the northeast, however, its influence will diminish as the short wave moves in toward daybreak Monday. Remaining low level moisture will be trapped under the persistent subsidence inversion, thus it is likely we will cloud up again overnight. What remains to be seen is if the wave, which will acquire a negative tilt, will have enough moisture to go along with the mid/upper forcing to bring some light precip to the area in the early/middle part of the morning. Not really buying the extent of precip in the operational models and prefer the lower probs seen in blended guidance, mainly because whatever falls is unlikely to be more than a trace. Temps will be borderline concerning the small potential that a few snow flakes could fall at the high elevations. Think this is not worth mentioning at this point because it is highly unlikely to cause any problems. Low temps will be close to normal. On Monday, the short wave quickly pivots on past and we end up in a fast cyclonic flow at the bottom of the upper trof in the afternoon, so we can look forward to clearing in the afternoon with temps rising a few degrees warmer than today because of the strong downslope flow east of the mtns.
SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/... As of 1:30pm EST Sunday: Monday night, area will be on the back side of the mostly dry upper system that passed through on Monday. Upper trough will continue to makes its way up the east coast with northwesterly flow aloft over the GSP region as well as northwesterly flow behind the frontal system at the surface. This flow pattern will keep moisture out of the area through Wednesday, with upper pattern progressing and flattening ahead of next system due later in the week. Temperatures will be at or slightly above seasonal normals Tuesday and Wednesday with mild northerly to northwesterly surface winds. Strong drying from NW flow will producing mostly clear conditions on Tuesday, with clear skies on Wednesday.
LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... As of 2pm EST Sunday: Next chance for significant precipitation lies in the Friday to Saturday time period where both the EC and GFS models are in fairly good agreement on timing of next system, a complicated longwave trough with a large piece of energy entering the Great Lakes Region Thursday night connected with a second piece over the 4-Corners region. This system shoves flattening ridge over the GSP region eastward Thursday morning, and manifests at the surface as a well-defined significant front that reaches the TN state line area Friday afternoon, progressing across the GSP area on Friday. Timing errors in this forecast, of course, are at least a half day this far out in the forecast. The Friday FROPA is preceded by a shift in winds from northerly to southwesterly on Thursday, along with a strong advance in moisture/dewpoints with dewpoints rising 5 to 10 degrees on Friday. Passage of front and upper system gives a good chance from rain in the Friday-Saturday period, with GFS and EC both suggesting amounts around a tenth to a half inch of moistly rain. 850mb temps are cold enough behind the front for a chance for some snow at the highest elevations Friday night.
Behind the front Saturday and Sunday, models diverge significantly, with EC showing southern stream shortwaves causing a continued chance for precipitation, while the GFS scours moisture out of the area. Temperatures will remain just above normal ahead of the cold FROPA on Friday, dropping 5 to 10 degrees on Saturday behind it. Windiest period in the forecast will be ahead of Front on Friday, with southwesterly winds of 10 to 20 mph.