Area Forecast Discussion
Issued by NWS Albany, NY

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000 FXUS61 KALY 200238 AFDALY AREA FORECAST DISCUSSION National Weather Service Albany NY 1038 PM EDT Fri Apr 19 2019 .SYNOPSIS... Showers will become widespread overnight into Saturday morning. Heavy rain and scattered thunderstorms may result in flooding along rivers, streams, and in low lying poor drainage areas. The showers will taper off during the day Saturday with cloudy, damp weather and mild temperatures for the rest of the weekend. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... Flood watches remains in effect. A complex system will impact the region bringing widespread rain to the area with locally moderate and heavy rainfall along with scattered thunderstorms. An upper level low has cut off at the base of a deep trough over the Tennessee Valley and will gradually move to the Ohio Valley overnight. As of 10:38 PM EDT, Scattered showers across forecast area most numerous over southern Adirondacks, eastern Catskills, southern Berkshires and Litchfield Hills. Some showers developing on upglide over shallow cold front over southern Adirondacks and Lake George area have been small but high reflectivity indicates small heavy downpours. Most of heaviest rain remains west of our forecast area. Maximum rainfall totals so far 0.7 inches at Cold brook in herkimer County and 0.6 inches at Claryville in southwest Ulster County. Occluded front will approach from southwest over next couple of hours and rainfall should increase later tonight. Update based on ongoing trends in satellite, radar and observations. Previous... Southerly flow between the deep trough to our west and ridging over the Atlantic Ocean is transporting Gulf moisture northward into the region. Precipitable water values are expected to rise to around 1.50 inches tonight and a strong low level jet will move into the region. Guidance indicates convective elements move into and across the area which will result in locally heavy rainfall. If there is any training this will increase the threat of flooding. A nearly stationary boundary located across the eastern Great Lakes and far northern New York is expected shift southward some overnight. This boundary will provide a focus for heavier rainfall across the northern Country into the southern Adirondacks. It will be mild tonight with lows mainly in the 50s and 60s. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/... The upper low will only move gradually eastward from over the Ohio Valley to the mid-Atlantic over the weekend as the surface low weakens over the region. The focus for heavier rainfall shifts New England on Saturday as the low level jets shifts to our east. The steady rain will taper off as the day progresses holding on into late in the day across western New England. The bulk of the rainfall is expected during the morning with lighter amounts in the afternoon. We will be in the warm sector with breezy southerly winds and are expecting highs in the 60s to lower 70s. Lingering showers Saturday night with cloudy, damp and mild for the remainder of the weekend as the upper low passing just to our south. Chances for showers are expected to be back on the increase Sunday night as activity moves in from New England as the upper low begins to shift northeastward. && .LONG TERM /MONDAY THROUGH FRIDAY/... Our vertically stacked, mature cut-off low will continue to impact our region on Monday as an Omega Block in the western Atlantic will prevent it from progressing eastward. In fact, as the cut off low inches off the East Coast, we notice it deepens with moisture from the sub-tropical moisture feed from the Fri-Sat event getting re- entrained into it. We also notice a TROWAL developing on its northwest flank which when combined with deformation dynamics should enhance rainfall amounts in western New England into parts of eastern NY (especially east of the Hudson). Lapse rates in this region also steepen to near 6C/km so we added thunder. The ECMWF continues to be the most robust with QPF amounts showing over an inch along and west of the CT River Valley while the GFS and CMC trended wetter compared to previous runs but are not nearly as wet. For now, placed widespread chance POPs with the highest POPs in western New England. Further upstream, a northern stream shortwave trough Ontario digging towards the Upper Great Lakes should be the kicker needed to push our slow moving mature cut off low out to sea on Tuesday. Strong subsidence in the wake of the cut off should strength a shortwave ridge building inbetween our exiting low and approaching trough. This should lead to a warm and mainly dry Tuesday with 850mb isotherms climbing to +7C to +10C leading to high temperatures in the 70s up the Hudson Valley. Our northern stream trough will be on the leading edge of a large scale cool air mass associated with a Canadian high. As this surface cold front pushes southeastward towards the the Saint Lawrence River Valley, a weak surface low in the Midwest looks to ride along it. Model guidance has once again trended wetter than previous runs (again trending towards the ECMWF) and we followed suite, placing widespread shower chances across the region for Wednesday. The spread in model guidance then increases by Thursday/Friday. The ECMWF shows our cool Canadian high pushing in the wake of our exiting surface low and thus giving us a dry yet seasonably cool Thursday. On the other hand, the GFS and CMC-NH paint a much gloomier picture showing the warm front associated with our surface low getting stuck along the Greens/Berkshires and our Canadian high becoming positioned in eastern Quebec. This would be a textbook set- up for New England and eventually areas along and east of the Hudson River to get "back doored" with the much cooler, marine influence air mass. Favored this output and lowered temperatures on Thursday to be in the 50s with low 60s in the western Mohawk Valley and Schoharie Valley which typically stay mild in these situations. Also continued to show slight chance of showers. All members of the global guidance show another system from the Ohio Valley potentially impacting our region for the end of the work. Therefore, continued the slight chance POP mention but did not go any higher given this the day 8 forecast. && .AVIATION /03Z SATURDAY THROUGH WEDNESDAY/... Radar shows areas or rain moving south to north across the area. KGFL reporting light rain but still VFR. KALB has MVFR visibility in moderate rain but ceiling still VFR. VFR at KPOU and KPSF. Showers will start to increase in coverage across the region and spread from southwest to northeast across the area overnight. Flying conditions will lower to MVFR all TAF sites for both vsby/cigs within on and off showers. Some IFR conditions are possible overnight all TAF sites especially within any thunderstorms. The best timing window for any thunderstorms right now appears to be 02z-06z, but this may need to be refined in future updates. Winds overnight will continue to be southerly, generally around 10 to 15 kts with guts to 30 kts. Showers will start to decrease in coverage tomorrow morning, especially for KALB/KPOU. A return to VFR conditions may occur at KALB/KPOU by mid to late morning on Saturday, but not till late in the day at KGFL and KPSF. Winds on Saturday will be southeast at 5 to 10 kts at KGFL, but will probably remain southerly at the other sites at 10 to 15 kts with gusts to 25 kts. Outlook... Saturday Night: Moderate Operational Impact. Chance of SHRA. Sunday: Low Operational Impact. Slight Chance of SHRA. Sunday Night: Moderate Operational Impact. Chance of SHRA. Monday: Moderate Operational Impact. Chance of SHRA. Monday Night: Moderate Operational Impact. Chance of SHRA. Tuesday: Moderate Operational Impact. Chance of SHRA. Tuesday Night: Moderate Operational Impact. Chance of SHRA. Wednesday: Moderate Operational Impact. Chance of SHRA. && .FIRE WEATHER... Showers will become widespread this evening then continue through the overnight. The showers will taper off Saturday with cloudy, damp weather and mild temperatures for the rest of the weekend. && .HYDROLOGY... The flood watch for areas north of I-90 is in effect for this evening through Sunday morning. For the Berkshires and northwestern Connecticut a watch is in effect tonight into early Saturday afternoon. As for the rest of the area, a flash flood watch is in effect for overnight through Saturday. Showers will become widespread this evening then continue through the overnight into Saturday morning. Locally heavy rain and scattered thunderstorms may result flooding along rivers, streams, and in low lying poor drainage areas. In addition, a lingering snowpack at the highest elevations of the Adirondacks and southern Green Mountains will also be contributing to the runoff across the southern Adirondacks, Lake George Region and southern Vermont. The showers will taper off Saturday however chances for showers will linger through the weekend. Please visit our Advanced Hydrologic Prediction Service /AHPS/ web page for specific area rivers and lakes observations and forecasts. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...Flood Watch from 2 AM EDT Saturday through Saturday evening for CTZ001-013. NY...Flash Flood Watch through Saturday afternoon for NYZ047>054- 058>061-063>066. Flood Watch through Sunday morning for NYZ032-033-038>043- 082>084. MA...Flood Watch from 2 AM EDT Saturday through Saturday evening for MAZ001-025. VT...Flood Watch through Sunday morning for VTZ013>015. && $$ SYNOPSIS...IAA/SND NEAR TERM...IAA/SND SHORT TERM...IAA LONG TERM...Speciale AVIATION...SND FIRE WEATHER...IAA HYDROLOGY...IAA

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