Area Forecast Discussion
Issued by NWS Albany, NY
Issued by NWS Albany, NY
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636 FXUS61 KALY 061535 AFDALY AREA FORECAST DISCUSSION National Weather Service Albany NY 1135 AM EDT Thu Jun 6 2024 .SYNOPSIS... Humid today with morning clouds breaking for some sun this afternoon as showers and thunderstorms track from west to east through early evening. Any thunderstorm can produce heavy downpours. Temperatures and humidity trend downwards with unsettled conditions tomorrow through the weekend, with a chance for showers and a few rumbles of thunder each afternoon and evening. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... As of 11am, expect quite the humid day today with our morning 12 UTC ALY sounding show a very moisture rich and tall/skinny CAPE profile including PWATs near 1.80" which is nearly 2.5 standard deviations above normal per the NAEFS. Also our freezing level is quite high at around 13kft. This environment will support efficient warm rain processes and potential for heavy downpours. Otherwise, a sfc warm front remain positioned to our south around the I-84 corridor with east-northeasterly winds along the interstate and southwesterly and even westerly winds to the south in NJ. While we should have break for mainly dry conditions through 17 UTC or so, a sharp wind shift boundary currently in western NY is quickly tracking eastward. Water vapor imagery in western/central NY shows a weak MCV signature along the boundary likely where a weak sfc low is developing along the triple point where the warm front, cold front, and occluded boundary meet. As this boundary and sfc low push eastward, an area of showers and thunderstorm will increase in coverage. While we have widespread cloud coverage in place this morning, any breaks of sun will easily contribute to increased instability thanks to high dew points in the 60s. Just how much sun occurs remains uncertain but high res guidance continues to indicate at least some breaks of sun should occur ahead of the wind shift boundary/triple point. The HREF and other CAMs suggest up to 1000 - 1500 J/kg of SB CAPE will develop ahead of the boundary thanks to breaks of sun with the best chance for breaks of sun mainly along and west of the Hudson River. While shear this morning remain paltry, as the boundary approaches, the kinematics should increase with 0-6km shear reaching around 30kts while 0-3km shear is limited to just 20-25kts. While low- level speed shear is weak with the stronger winds in the higher levels of the boundary layer, it is worth noting that the directional shear in the lowest levels is quite impressive as southeasterly winds abruptly shift to west- southwest behind the boundary late this afternoon into the early evening. This will provide strong low- level forcing to enhance lift/ascent for rain and embedded thunderstorms to develop. While thunderstorms will likely develop along the incoming wind shift boundary, the main question is whether or not they will become severe. Overall, instability and shear are rather weak and so are mid-level lapse rates which are around 5.5C/km but with a wedge of dry air in the wake of the incoming boundary, DCAPE values get a little interesting increasing to 500J/kg which could support damaging winds. However, the coverage of these higher DCAPE values look limited so overall confidence for severe weather is low. But, the impressive wind shift boundary and low-level forcing still makes us uneasy and we will maintain a close watch on radar trends through the afternoon and evening (3pm - 9pm) when the wind shift boundary swings through the region. Agree with the Marginal Risk from SPC given the environment parameters in place. Should we see more breaks of sun through early afternoon, there will be an increased risk for severe weather and we will collaborate with SPC and neighboring WFOs to evaluate if the convective outlook should be adjusted. The very moist environment today will also support heavy downpours from any storms as well. Storms should not train over a given area and should be progressive so not expecting widespread flooding. However, poor drainage flooding is certainly possible for quick heavy downpours producing a 0.50 - 1 inch of rain in a short period of time from the efficient warm rain processes. Previous discussion...One area of scattered showers will affect our region until mid morning. Another band of showers in western NY/PA will increase in coverage through the day as some instability and low level forcing along a surface to boundary layer wind shift and leading edge of weak cold advection track into our area. Instability will be marginal as will shear but the low level forcing should again, support an organized band of showers and scattered thunderstorms. Locally heavy rain and gusty winds are possible in the thunderstorms. There is a marginal risk for severe thunderstorms today with potential isolated damaging wind gusts. Highs today, with the mostly cloudy to cloudy sky, will be in the upper 70s to lower 80s and lower to mid 70s higher elevations. && .SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/... Upper cut off low slowly approaches tonight through Saturday night and there are disagreements in the timing and track of trailing upper energy merging with the upper cut off low, which would determine where the southern edge of the upper cold pool and associated surface based instability would enhance coverage of showers and isolated thunderstorms Friday and Saturday. In general, showers and thunderstorms diminish during the evenings to just isolated coverage of showers each night through daybreak tonight, Friday night and Saturday night. Breaks in the clouds each night as well. Upper dynamics and gradual cold advection Friday and Saturday with clouds and showers becoming more widespread from late morning through the afternoons Friday and Saturday. The best upper dynamics and instability associated with the upper cold pool should be in areas north of I-90, where the best coverage of showers and storms should be. Still, solid chances for showers and isolated storms south of I-90. So, with some peeks of sun potentially each morning before convective clouds form, producing a mostly cloudy to cloudy sky, temperatures will reach the 70s to near 80 Friday and around 70 to mid 70s Saturday, with some 60s higher terrain. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... We remain under the influence of the upper-low through the beginning of the work week before high pressure builds in from the west and forces the return to dry, warm weather... By the start of the long term forecast period, the upper-low will be located overhead, sprawled across the Ontario/Quebec border. Broad cyclonic flow will help to maintain a relatively moist airmass, leading to persistent clouds and additional rounds of showers and possibly some embedded rumbles of thunder Sunday and Monday as a weak wind shift boundary pushes through the region. Shower and thunderstorm activity looks to be relatively scattered in nature and will likely remain primarily diurnally driven with daytime heating will aid in increased instability. By Monday night, the upper-low looks to finally make its exit from our overhead as it continues to weaken and push further north and east. Guidance shows there could be an additional round of showers and possible embedded rumbles of thunder Tuesday afternoon as upper troughing looks to break away from the main low pressure core and linger across the Northeast but these would once again be relatively scattered and light in nature. The upper trough then looks to be forced eastward as upper-level heights increase in response to a mid/upper-level ridge building in across the region from the west. With surface high pressure advancing in tandem with the upper ridge, dry conditions will be returned to eastern New York and western New England for Tuesday night through at least Wednesday before a shortwave disturbance threatens to disturb the tranquility for Thursday. High temperatures Sunday and Monday will range primarily from the mid/upper 60s to mid 70s with pockets of upper 50s to low 60s above 1500 ft and upper 70s in the Hudson Valley. Tuesday begins the warming trend with temperatures increasing to the upper 60s to upper 70s before we rise back into the low 70s to low and possibly mid 80s Wednesday and Thursday. Low temperatures throughout the period will generally range from the upper 40s to low/mid 50s through Tuesday night with Wednesday increasing to the low to upper 50s. && .AVIATION /15Z THURSDAY THROUGH MONDAY/... Through 12z Friday...MVFR conditions prevail at all terminals with the exception of KPSF whose ceiling has dropped to IFR heights. Showers have not been as extensive thus far this morning as what was previously expected, so outside of a stray sprinkle or two, expect primarily dry conditions into this afternoon. There is some uncertainty with ceiling heights today as model soundings show some pockets of dry air cutting into the lower levels later this morning. However, generally ceiling heights should remain within MVFR thresholds with brief improvements to VFR possible throughout this morning. This afternoon, MVFR heights should steadily return as scattered thunderstorms develop. PROB30 groups were added to the TAF groups for expected convection between 21z-01z. Thunderstorms could drop ceilings to IFR heights with MVFR visibilities. However, IFR visibilities are also possible should a heavier downpour cross into the terminals. Once convection ceases shortly after sunset due to lack of daytime heating to drive instability, conditions will gradually improve possibly back up to VFR conditions. Winds throughout the 12z TAF period will be light and variable to start, then increasing to sustained speeds of 5-10 kt out of the southeast by this afternoon. By the end of the 12z cycle, winds will decrease to speeds of 2-5 kt at variable directions. Outlook... Friday Night: Low Operational Impact. NO SIG WX. Saturday: Moderate Operational Impact. Breezy. Chance of SHRA...TSRA. Saturday Night: Low Operational Impact. Slight Chance of SHRA...TSRA. Sunday: Moderate Operational Impact. Chance of SHRA...TSRA. Sunday Night: Low Operational Impact. Slight Chance of SHRA...TSRA. Monday: Moderate Operational Impact. Chance of SHRA...TSRA. Monday Night: No Operational Impact. NO SIG WX. Tuesday: Moderate Operational Impact. Chance of SHRA. && .HYDROLOGY... Showers and scattered thunderstorms are expected through Thursday. Rainfall amounts of around 1 inch are expected with localized amounts up to 2 inches. Some thunderstorms will contain heavy rain and could produce localized ponding of water on roadways, urban and small stream flooding and standing water in low lying areas. No flooding of main stem rivers is expected. Additional showers and thunderstorms will occur Friday through the weekend but less widespread and lighter, with additional amounts of perhaps up to a half inch of rain through the weekend. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. MA...None. VT...None. && $$ SYNOPSIS...NAS/Speciale NEAR TERM...NAS/Speciale SHORT TERM...NAS LONG TERM...Gant AVIATION...Gant HYDROLOGY...NAS