FORECAST DISCUSSION: FRIDAY, OCTOBER 20TH, 2017

SECTION 1: A WARM AND DRY WEEKEND

Conditions should remain warm and sunny during the days and clear and crisp at night for at least Friday and Saturday as high pressure remains in the vicinity. Southwest flow will begin Saturday afternoon as high pressure slowly begins to exit the area. High temperatures will be in the middle and upper 70s, with a few areas reaching the lower 80s, while lows will remain in the 40s. By Sunday, an upper-level cut-off low will begin to develop over the central United States, which will be the source of our next significant weather disturbance. 

SECTION 2: SIGNIFICANT RAIN POSSIBLE EARLY NEXT WEEK

As was mentioned in the previous section, a cut-off low will develop on Sunday and move toward our area as we head into the day on Monday. In advance of this slow-moving synoptic-scale feature, a strong moist flow will develop out of the south and southwest. This moist flow combined with an incoming frontal disturbance will provide the mechanism for creating significant amounts of precipitation. Eventually, this area of upper-level low pressure will be absorbed into the larger synoptic-scale flow, allowing the precipitation to move off the East Coast. If the cut-off low is absorbed into the synoptic-scale trough sooner, the heavy precipitation axis will occur to the west, leaving us with only moderate precipitation amounts. If the cut-off low is absorbed into the broader flow later, the heavy precipitation axis may impact us as well as areas in Central and Eastern North Carolina. As of Friday morning, most mid-range forecast models are anticipating somewhere between 1.5 and 3.5 inches for our area between Monday morning and Wednesday morning.

European Model (ECMWF) Forecast of 500-mb Geopotential Height (contours) and anomalies (shading) for Monday, October 23rd, 2017 at 1200 UTC (8 a.m. ET). The most important things to notice are the location of the small area of low heights (denoted in blue) and the positioning of the green arrow indicating moist flow. Image courtesy of Accuweather Professional

European Model (ECMWF) Forecast of 500-mb Geopotential Height (contours) and anomalies (shading) for Monday, October 23rd, 2017 at 1200 UTC (8 a.m. ET). The most important things to notice are the location of the small area of low heights (denoted in blue) and the positioning of the green arrow indicating moist flow. Image courtesy of Accuweather Professional

ECMWF Model Forecasted 925-mb Meridional Wind Anomaly for Monday, October 23rd at 1800 UTC (2 p.m. ET). Meridional Wind is the North-South component of the wind. Orange and Red shading represents an area of strong southerly flow, indicating the region where the most Gulf moisture may be pulled northward. This is similar to the area of the green arrow on the previous slide. Image courtesy of Accuweather Professional

ECMWF Model Forecasted 925-mb Meridional Wind Anomaly for Monday, October 23rd at 1800 UTC (2 p.m. ET). Meridional Wind is the North-South component of the wind. Orange and Red shading represents an area of strong southerly flow, indicating the region where the most Gulf moisture may be pulled northward. This is similar to the area of the green arrow on the previous slide. Image courtesy of Accuweather Professional

GFS Model (American) Forecasted Precipitation amounts through Wednesday, October 25th, at 1200 UTC (8:00 a.m. ET). This model indicates 2-3" of rain for our area. Image courtesy of Pivotal Weather

GFS Model (American) Forecasted Precipitation amounts through Wednesday, October 25th, at 1200 UTC (8:00 a.m. ET). This model indicates 2-3" of rain for our area. Image courtesy of Pivotal Weather

ECMWF Model Forecasted Precipitation amounts from Monday morning through Wednesday morning. This model is showing amounts of 1.5-3" in our area, with some mountain locations possibly seeing 3-5" of rain. Image courtesy of Accuweather Professional

ECMWF Model Forecasted Precipitation amounts from Monday morning through Wednesday morning. This model is showing amounts of 1.5-3" in our area, with some mountain locations possibly seeing 3-5" of rain. Image courtesy of Accuweather Professional

SECTION 3: ANOTHER SHOT OF COLD AIR LATER NEXT WEEK

Once the rain that will impact our area Monday and Tuesday moves off to the east, it will be replaced by cool and dry air coming down from Canada. Temperatures in the middle and latter half of next week should fall considerably, with some high elevations possibly recording their first sub-freezing low temperature.

ECMWF Model Forecasted 500 mb Geopotential Height (contours) and Anomalies (shading) for Wednesday, October 25th at 1200 UTC (8 a.m. ET). The wording indicates the location of warm and cool air. Image courtesy of Accuweather Professional

ECMWF Model Forecasted 500 mb Geopotential Height (contours) and Anomalies (shading) for Wednesday, October 25th at 1200 UTC (8 a.m. ET). The wording indicates the location of warm and cool air. Image courtesy of Accuweather Professional

Have a great Friday!

Chase Scott Graham