Area Forecast Discussion (AFD)
Issued by Huntsville, AL (HUN)
390 FXUS64 KHUN 211759 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 1159 AM CST Tue Nov 21 2017 .UPDATE... For 18Z TAFS. && .NEAR TERM...(Rest of Today) Issued at 1159 AM CST Tue Nov 21 2017 Despite light winds, temperatures across the region have risen into the mid and upper 50s. Will make adjustments here too and send out another update shortly. Previous 10 AM issuance.... If you prefer dry/mild weather, today should be shaping up like that. An area of high pressure that brought the chilly conditions to the region yesterday morning (and not as cool this morning) has continued building eastward. It was now situated off of the east coast and north of Bermuda. An anticyclonic flow around it has firmly placed the Tennessee Valley in a light southerly flow. Somewhat deeper moisture, and a few light showers were in progress along parts of the Gulf coast. These showers, and more clouds were moving NNE from the western Florida panhandle to across eastern Alabama and much of Georgia. In fact, the lower clouds have spread westward over Ft Payne. West of here, periods of more high clouds were spreading to the east as a surge of high altitude moisture heads eastward, rounding large scale troughing extending southward along the Mississippi Valley region. The lower clouds should remain across parts of NE Alabama, and even retrogress west of the Cumberland Plateau; or across Winchester during some of the afternoon. The remainder of the region should experience more sun - and somewhat warmer high temperatures. The sun and light southerly flow should help high temperatures rise into the lower 60s. .SHORT TERM...(Today through Thursday) Issued at 330 AM CST Tue Nov 21 2017 Our gradual warming trend will continue today as deeper southerly flow develops ahead of an approaching cold front, progged to pass through the region early Wednesday. Regardless of the warmer temps and slight moisture return from the south, ridging through around H7 along with a decent subsidence inversion in place will keep rain chances minimal. It is worth noting that a few global and regional models were hinting at a possibility of some showers today for parts of DeKalb and eastern Jackson associated with a surge of moisture from the Gulf. However, expect that feature to remain east of the CWA as the mid/upper level trough will swing through the area during the afternoon hours. Late Tuesday/early Wednesday timeframe will feature a dry cold front quickly shifting through the area, helping to reinforce some cooler than average temps. Thanks to the cold air advection, temps on Wednesday will likely only push into the upper 40, maybe mid 50s for our southern zones. Expect temps to fall into the upper 20s by early Thursday. This cold air mass will gradually moderate by Thursday. Low level flow will start to lose its northern component as the ridge shifts east, however mid/upper level winds will keep N/NW flow in place. So while temps will be warmer Thursday and Friday morning compared to the previous day, we will still trend below average for mid/late Nov. temps. .LONG TERM...(Friday through Monday) Issued at 330 AM CST Tue Nov 21 2017 On Day 4 (Fri) an upper shortwave axis will be dropping southeast through the TN valley into the existing trough position over the central Gulf Coast and Gulf of Mexico. This will produce little more than a few high clouds with the baroclinic zone/surface low will be developing/moving northeast across the FL peninsula and east of the Carolinas. A sprawling high pressure ridge will follow behind from the central Appalachians through the western Gulf Coast on Friday. Then, another shortwave and fast moving cold front will drop southeast Friday night into Saturday morning (GFS) and Saturday during the day (ECMWF). The suggested blends yield high temps in the upper 50s/lower 60s Saturday, followed by about a 10 degree drop for highs on Sunday. With the surface high on the GFS dropping right over the TN valley (and the ECMWF ridge over the area as well) ideal conditions for radiational cooling are expected. This means another widespread hard freeze is likely again on Monday morning with raw model dew points suggesting lows could drop into the 20s areawide. The models depict a rather quick airmass modification on Days 7-8 as a mid to upper level ridge shift east into the southeast U.S. && .AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon) Issued at 1159 AM CST Tue Nov 21 2017 VFR conditions should continue across the TAF sites. An area of stratus moving northward from the Gulf across eastern Alabama should remain east of the KHSV terminal into the evening. Otherwise periods of high clouds will continue. A dry cold front arcing from north and central Indiana, to near St Louis and Amarillo will move to the southeast, moving across the region tonight. No weather of consequence is expected, except that S-SW winds will become NW after the front passes. Northwest winds should increase into the 10-20 kt by late Wednesday morning. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...RSB SHORT TERM...Barron LONG TERM...17 AVIATION...RSB For more information please visit our website at weather.gov/huntsville.