Area Forecast Discussion
Issued by NWS Huntsville, AL
Issued by NWS Huntsville, AL
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115 FXUS64 KHUN 031730 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 1230 PM CDT Fri May 3 2024 ...New AVIATION... .NEAR TERM... (Rest of Today) Issued at 930 AM CDT Fri May 3 2024 The forecast this morning has already proved to be tricky. QPF amounts have already over preformed and CAMS have struggled to accurately depict morning rain and storms. This is not necessarily surprising as we have a summer like system moving through consisting of weakly forced shortwaves that CAMS notoriously struggle to grab on to. Based on the over performance of morning rain, this gives credence to higher QPF amounts likely seen through the weekend, however that will be further addressed in the afternoon forecast package. For the rest of today, current observations indicate an area of convergence extending NW to SE through the CWA. Weak showers will likely continue to develop along that axis over the next few hours ahead of the arrival of the next short wave. This afternoon into this evening, the next shortwave is forecast to move through the area but there is significant disagreement in the models as to the coverage of showers and storms associated with it. Right now the most likely scenario seems that pop up summer like convection will develop first from surface heating in the mid afternoon resulting in isolated showers and thunderstorms across the area. Later in the evening, higher coverage of showers and storms is expected with the arrival of the shortwave. Two scenarios seem possible with the second shortwave: 1.) most of the area seeing light to medium rain through the evening, or 2.) a band of showers setting up along one axis only impacting a limited area. With such poor model guidance so far, the solution may not be apparent until it begins to unfold. Fortunately, there is no severe threat associated with these shortwaves, frequent lightning and periods of heavy rainfall will however still pose a threat to outdoor activities. && .SHORT TERM... (Tonight through Sunday night) Issued at 433 AM CDT Fri May 3 2024 Fairly high POPs will remain warranted across the region overnight, as broad scale vertical motions will increase slightly with the passage of a weak mid-level shortwave trough to our northwest. The risk for thunderstorms will remain highest this evening (prior to the onset of the diurnal cooling cycle), with a gradual transition to light rain expected by early Saturday morning. Due to the abundance of moisture in the boundary layer and only light southerly winds, patchy fog will be possible for many locations as well. Present indications are that the general synoptic pattern across our region will change very little on either Saturday or Sunday, although with indications of low-amplitude shortwave ridging across the region on Saturday (in the wake of the shortwave trough), coverage of afternoon showers and storms will likely be somewhat lower compared to today. By late Sunday afternoon or Sunday evening, the marine warm front (discussed in the near term section) will begin to lift northeastward through the CWFA as a strong upper low tracking into the central Rockies induces surface pressure falls across the high Plains of eastern CO/WY. This will likely support a fairly high coverage of showers and thunderstorms Sunday evening. Highs will be in the u70s-l80s once again tomorrow, before warming into the l-m 80s Sunday, and lows should remain in the l-m 60s through Monday morning. && .LONG TERM... (Monday through Thursday) Issued at 433 AM CDT Fri May 3 2024 After warm frontal convection spreads northeastward and out of the region late Monday morning, the TN Valley will be solidly within a very warm/moist tropical airmass, with dewpoints expected to rise into the m-u 60s as southwesterly low-level flow strengthens. Although this will contribute to greater instability (especially during the afternoon hours), a mid-level ridge will shift across the region downstream from the central Rockies upper low as it begins to spread northeastward into the northern Plains, and this should yield a lower coverage of mainly afternoon thunderstorms from Monday-Wednesday. Overnight lows will steadily increase into the u60s-l70s through the middle of next week (due to both elevated SW winds and moisture advection), with highs also warming into the mid (to perhaps upper) 80s by Wednesday. Although details are unclear at this time range, conditions will become more favorable for convection at the end of the extended period (Wednesday night/Thursday), perhaps in the form of MCS activity that may initiate along a cold front to our northwest and propagate southeastward into the local area. Should this scenario materialize, conditions will be favorable for organized severe thunderstorms across our region, with boundary layer dewpoints in the u60s-l70s beneath a belt of mid-level WSW flow of 35-45 knots. && .AVIATION... (18Z TAFS) Issued at 1230 PM CDT Fri May 3 2024 Afternoon pop up convection will make for challenging TAFs. Scattered showers and thunderstorms are likely to develop through the afternoon from surface heating. Kept VCTS in the prevailing to account for uncertainty in storm coverage and intensity. Later this evening, just before 0Z, more widespread showers and storms will move in from the west. This will result in heavier showers with periods of MVFR to IFR possible as reflected in the tempo group. While strongest showers and storms will move out of the area during the early morning hours, MVFR ceilings will likely remain for the duration of the TAF period. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...None. TN...None. && $$ NEAR TERM...RAD SHORT TERM....70 LONG TERM....70 AVIATION...RAD