Area Forecast Discussion
Issued by NWS Huntsville, AL
Issued by NWS Huntsville, AL
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203 FXUS64 KHUN 010157 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 857 PM CDT Tue Apr 30 2024 ...New NEAR TERM... .NEAR TERM... (Tonight) Issued at 857 PM CDT Tue Apr 30 2024 Under the influence of upper level ridging, dry weather remains in place overnight as lows drop into the mid to upper 50s. With calm winds and clear skies in place, our biggest talking point tonight is fog formation. Current dew point depressions are between one to ten degrees through the TN Valley. As we continue into the morning hours, we have medium confidence in fog formation through at least the rivers/valleys of northern AL and southern middle TN. Elsewhere, we have a low chance of patchy fog formation. Visibilities will be monitored closely and any widespread fog formation will be treated with a subsequent SPS or Dense Fog Advisory. If fog does form, it should dissipate shortly after sunrise during the late morning hours. && .SHORT TERM... (Wednesday through Thursday night) Issued at 151 PM CDT Tue Apr 30 2024 High pressure will become established across the Tennessee Valley Wednesday and Thursday, promoting mostly sunny and dry conditions both days. In fact, a pronounced warm-up will take place, especially by Thursday as the mid/upper ridge axis begins to amplify and winds veer to a southerly direction. In response, highs will climb into the mid 80s on Wednesday and the mid to upper 80s again on Thursday. It`s not completely out of the realm of possibility that a couple of sites reach the 90 degree mark (ensembles hint at about a 10% chance of exceeding that value at both MSL and HSV). Cloud cover will begin to increase by Thursday evening and especially late Thursday night as another mid/upper trough swings into the Great Lakes -- with its associated cold front shifting through the mid/lower Mississippi Valley. Low to medium (20-40%) chances for rain showers (and a few elevated storms) are forecast late Thursday night into Friday morning ahead of the front. QPF amounts are expected to be light, however, as a bulk of the precipitation (and higher rain chances) will move in after 12z Friday. More on this in the section below. && .LONG TERM... (Friday through Monday) Issued at 208 AM CDT Tue Apr 30 2024 The latest suite of global model guidance suggests that the TN Valley will remain beneath a region of light and generally unamplified WSW flow aloft throughout the duration of the extended forecast period, featuring mid-level wind speeds of 25-30 knots at most. In the low-levels a warm/moist airmass will reside across the region, with dewpoints expected to be in the l-m 60s on Friday/Saturday, before perhaps rising into the m-u 60s on Sunday/Monday. This will yield seasonably high values of CAPE (particularly during the afternoon hours, when boundary layer temperatures should rise into the l-m 80s). At this point, it appears as if coverage of showers and thunderstorms will be highest on Friday afternoon/evening, which is the timeframe when a weak cold front may drift southeastward into the CWFA prior to stalling. The front may indeed remain in the region for much of the day on Saturday (warranting a continuation of low-medium chances for showers and storms), before returning northward on Sunday as an amplified trough in the northern stream induces cyclogenesis in the lee of the northern Rockies. Although the atmosphere will be moderately unstable each day, vertical wind shear will not be conducive for the development of organized convection and lightning/locally heavy rainfall should be the primary storm impacts. && .AVIATION... (00Z TAFS) Issued at 608 PM CDT Tue Apr 30 2024 VFR conditions will continue at KMSL and KHSV through the TAF period, however, a low chance of fog exists in the early morning hours Wednesday. If this occurs, MVFR conditions are possible at both KMSL and KHSV. Any fog that does form should dissipate shortly after sunrise, in the late morning hours. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...None. TN...None. && $$ NEAR TERM...HC SHORT TERM....AMP LONG TERM....70 AVIATION...HC