Area Forecast Discussion (AFD)
Issued by Huntsville, AL (HUN)
000 FXUS64 KHUN 151112 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 612 AM CDT Mon Oct 15 2018 .UPDATE... For 12Z TAFS. && .NEAR TERM...(Today) Issued at 347 AM CDT Mon Oct 15 2018 The forecast area is in between a building ridge centered across FL, and an amplified, positively tilted trough moving into the Great Lakes. A lingering boundary to our northwest will continue to bring showers this morning, with higher POPs across NW AL and Southern Middle TN (much like yesterday). As the sfc low scoots east of the Great Lakes, it will pull the associated cold front southeast into the region later this afternoon. Ahead of the front, there will be some isentropic lift and winds will become southerly, increasing showers to become scattered areawide with the increase of moisture and temps. Cannot rule out a rumble of thunder so included isolated thunder chances in for this afternoon. Daytime highs reaching the upper 70s (maybe 80 degrees), will be the warmest in the forecast package. The front will move through fairly quick and behind the front, winds will become northwesterly and increase to ~10mph with gusts ~15mph. .SHORT TERM...(Tonight through Wednesday Night) Issued at 347 AM CDT Mon Oct 15 2018 Northwesterly winds will filter in cooler air behind the front, getting overnight lows down into the lower 50s across NW AL and Southern Middle TN and into the upper 50s across NE AL. Precip chances will linger into tonight, but become more isolated later tonight. On Tuesday, the front will be south of the forecast area but we will still be in between the ridge to our southeast and a trough to our north. The southwesterly flow aloft will stream disturbances into the TN Valley and combined with isentropic lift, precip chances will increase through the day. Kept a slight chance of rain going in early Wednesday to accommodate the discrepancy between the GFS that clears out the precip faster than the ECMWF. Conditions will be dry, and cooler, by Wednesday afternoon with decreasing cloud cover. Daytime highs will be in the mid 60s and overnight lows will dip into the upper 40s as skies become mostly clear. .LONG TERM...(Thursday through Sunday) Issued at 347 AM CDT Mon Oct 15 2018 Upper level ridging will in place over the SE North American domain on Thursday. This ridge will weaken somewhat during the course of the remainder of the week, as troughing in the northern stream begins to sharpen during the weekend. The amplification of the trough in part will be caused by an upper disturbance/speed max moving across British Columbia Wed/Thu, merging with energy ejected from an upper low over the Intermountain West. There was reasonable inter-model agreement from the GFS, ECMWF, Canadian into next Sunday regarding their respective forecasts of the 500mb level. At the surface, high pressure layered over the Ohio Valley will move eastward, resulting in NE winds on Thursday becoming east, then SE on Friday. This will gradually bring additional lower level moisture across the southeast CONUS and rain chances - just in time for the weekend. The deterministic models were good agreement with rain chances late Friday and on Saturday. Following them, have lower end rain chances starting Friday afternoon for our Tennessee counties and along the far northern Alabama border region. Better chances for showers are expected Friday night and Saturday morning, as a cold front pushes in a NW-SE manner across the forecast area. Post frontal showers occurring north of the boundary will gradually end from north to south as colder and drier air slowly filters in. Although there was shear preceding/accompanying the front, not enough instability was present, therefore kept thunder out of the forecast. Daily high temperatures in the extended will trend below seasonable norms. Highs on Thu/Fri will range in the upper 60s to around 70, below average highs of around 74. Highs in the mid 60s Saturday will cool to around 60 on Sunday. Night time lows above normal Thursday and Friday nights (around 50) will cool into the mid 40s for Saturday night. Lows nearing 40 look possible Sunday night, with a few upper 30s in those normally colder spots. && .AVIATION...(For the 12Z TAFS through 12Z Tuesday morning) Issued at 612 AM CDT Mon Oct 15 2018 VFR conditions will start off the TAF period. As a cold front pushes into the area, ~18/19Z CIGS will fall into lower MVFR category (1500-2000ft) and VCSH begins. Northerly winds will increase behind the front ~10kts, showers taper off, and CIGS remain in MVFR, however will not rule out the chance they fall into IFR temporarily. Most models agree that CIGS will remain low-end MVFR til the end of the TAF period, but they do not agree on timing for rainfall to return so kept a mention of rain returning out for this TAF issuance. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...JMS SHORT TERM...JMS LONG TERM...RSB AVIATION...JMS For more information please visit our website at weather.gov/huntsville.