Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/09/18

Area Forecast Discussion
National Weather Service Binghamton NY
1007 PM EST Thu Mar 8 2018 .SYNOPSIS... A slow moving storm system over Northern New England will keep snow showers over Central NY through at least Friday night. A few inches of accumulation will be possible, especially in the higher terrain surrounding the Cortland, Syracuse and Norwich area. Temperatures will remain seasonably cool, with highs in the 30s and overnight lows in the 20s. && .NEAR TERM /THROUGH FRIDAY NIGHT/... 945 PM update... Water vapor channels show two upper level features that will affect NY and PA into the overnight hours. The first is an upper level low that will cross east of PA overnight. This feature will bring scattered snow showers and flurries mainly to northeast Pa and south central NY overnight and then depart east of these areas by 09z with a deep west to northwest flow of fairly chilly and moist air becoming established across all of central NY / northeast Pa. The other feature was the remnants of an upper level low over Maine earlier today that will track westward into Quebec late tonight and become an inverted upper level trough. The water vapor channels show that moisture with this feature will work from north to south into central NY and northern PA overnight. Looking at the thermal fields, our area will see remnant cold conveyor belt moisture from this upper feature as the low and mid levels will actually be warm advecting. Soundings show that moisture increases in the column overnight and sure enough the hi resolution models bring light simulated radar echoes south overnight to central NY and northern PA by 12z Friday. So for the overnight have mainly scattered flurries and snow showers with likely to categorical snow showers farther north across north central NY late tonight. Believe lake enhancement combined with synoptic moisture will lead to higher POPs for light snow showers up there. Snow accumulations will be around 1-2" overnight in our far northern counties rest of area sees less than 1" overnight with many areas see almost no accumulations. Then for Friday, with cold air aloft under this broad upper level low/trough and the stronger March sun, we actually see some instability generated by afternoon. This will combine with decent amount of lake enhanced synoptic moisture to lead to scattered to numerous snow showers. Model mixed layer CAPEs reach around 40-80 J/KG which isn`t that bad for snow showers. The shear in the lowest 0-1 km layer was only 15-20 knots which suggests a more celluar pattern of snow showers which lessons the likelihood of banded heavy snow showers and potential snow squalls. Looking at a local study this jives well as we would need 0-1 km shear to be 30 knots or more for linear convective structures. The NAMnest and latest HRRR both suggest celluar convection breaks out with insolation in the afternoon. The WRF_ARW and WRF_NMM both suggest linear convection. Based on local study we will follow NAMnest and HRRR for this which reduces the chances for major snow squalls. We will still have higher POPs for snow showers especially in central NY. Previous discussion is below. 300 PM update... A broad upper level trough remains in place over the Northeast this afternoon. A large upper level low continues to spin off the Maine coast, and another upper level disturbance is evident in the latest GOES-E imagery over Lake Huron. Plenty of strato- cumulus cloud cover has develop under the unstable atmosphere this afternoon, along with a few flurries/snow showers. Temperatures have reached the upper 20s to mid-30s as expected. The latter disturbance mentioned above will slowly rotate toward the region later this evening. Behind this system a moist northwest flow will become established, with snow showers becoming likely late tonight in all of our NY zones, and also the far N. Tier of PA. There will be a chance of snow showers further south toward Towanda--Scranton and Wilkes-Barre. Snow showers persist through the day on Friday as a well aligned flow of lower and mid-level moisture continues to wrap around a nearly stationary mid-level low center near Montreal. Forecast model soundings indicate steep low level lapse rates below about 700mb...along with some surface based instability (up to 50 J/Kg). This should allow some heavier, convective like snow showers and squalls to form over much of the area late Friday morning and into the afternoon hours. These squalls could be locally heavy at times, reducing visibility to under 1/2 mile and creating hazardous travel conditions. Surface temperatures will hold in the lower to mid-30s Friday afternoon, except some upper 20s in the higher elevations of Central NY. Most locations along and south of Rte-17/I-86 can expect 1 inch or less of snow accumulation through the day Friday. Further north, snow amounts will range from 1 to 3 inches...especially in the higher elevations. Gusty northwest winds between 10-20 mph, with gusts up to 25-30 mph can also be expected Friday. By late Friday afternoon, evening and into Friday night indications are that a well developed lake effect/enhanced snow band will form along a 290-300 flow. This band should initially form along a line from about Penn Yan to Marathon and Walton NY late Friday afternoon. Latest model guidance is indicating a good upstream moisture connection with Georgian Bay...which should allow the snow band to extend a long distance off of Lake Ontario. By Friday evening, the band should slowly drift north, along a line from about Auburn/Geneva to Cortland,Norwich, Oneonta and Delhi. The northern end of the band may be near Syracuse at this time. The snow band could potentially produce snowfall rates up to 1 inch per hour at times. The snow band is forecast to continue drifting north Friday night, eventually impacting the NYS Thruway corridor from Weedsport to Syracuse and Utica/Rome. Overnight lows Friday night will be in the 20s areawide. Outside of the main snow band, expect some scattered snow showers/flurries across the NY Southern Tier and N. tier of PA...meanwhile the Wyoming Valley region should be mostly cloudy but generally dry. Forecast snow accumulations Friday night look to range from 2 to 4 inches across the northern Susquehanna Region, Northern Finger Lakes and the NY Thruway corridor. 1 to 3 inches could fall in the western Catskills (Delaware/Otsego Counties)...with an inch or less from the NY Southern Tier and points south into Northeast PA. Decided to hold off on any winter weather advisories at this time and let the evening shift and/or midnight shift take another look at possible accumulations. Main uncertainties continue to be just how much snow will actually accumulate during the day on Friday with the marginal temperatures and stronger March sun angle now in place. Gut feeling is that most of the accumulations will be above 1500 feet during the day Friday, with more widespread accumulations into the lower elevations Friday night. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... Deep northwest flow continues bringing moisture into the area. Cold pool aloft and late winter sun will add to the instability so snow showers will increase through the day over much of the area. Exception might be the downslope area of the extreme south and southeast parts of the forecast area. Snow showers taper off and end Saturday night as we lose heating and the flow relaxes. On Sunday, still some instability but we get some surface ridging so any activity will be light and very widespread. High pressure builds in bringing a dry weather for Sunday night. && .LONG TERM /MONDAY THROUGH THURSDAY/... Closed 500mb low drops into the area on Monday bringing moisture and widespread snow showers as heating reacts with the cold pool aloft. Surface flow remains northerly so there will be some lake input, but main effect will be the additional lift provide as the flow hits the higher terrain of central NY. Slow moving system is still directly overhead on Wednesday so there`s little reason to think the activity will taper off or end before midweek. Temperatures during the day will be near normal, in the 30s but nights will be mild with the clouds and moisture. && .AVIATION /03Z FRIDAY THROUGH TUESDAY/... Mainly lower VFR ceilings are present across all terminals. A brief drop to IFR has occurred as of this writing at KAVP from a localized snow shower. This should end quickly as per radar trends so no amendment. We expect VFR most terminals through 06z with a few snow showers restricting ceilings and visibilities to MVFR at KRME, KSYR between 01z and 04z at times and KITH / KELM / KBGM between 07z and 12z with KBGM likely seeing brief IFR conditions in this time period. For KBGM we also expect MVFR ceilings and visibilities in snow showers by 12z. Then for all terminals by late morning Friday we have ceilings between 2500 feet and 4500 feet with occasional snow showers dropping conditions to LIFR at KSYR, KRME, KITH and KBGM and IFR at KELM and MVFR at KAVP between 18z and 22z with the afternoon heating, combined with cold air aloft and moisture. Westerly winds be generally 5-12 kts tonight and West to northwest winds 10-15 kts, with gusts 20-25 kts Friday during the day. Outlook... Friday Night through Saturday...Occasional restrictions from ceiling bases/snow showers, especially CNY terminals. Saturday Night/Sunday...Primarily VFR. Monday/Tuesday...Chance of restrictions in snow showers. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...None. NY...None. && $$ SYNOPSIS...DJN/MJM NEAR TERM...DJN/MJM SHORT TERM...DGM LONG TERM...DGM AVIATION...DJN
Area Forecast Discussion
National Weather Service Bismarck ND
920 PM CST Thu Mar 8 2018 .UPDATE... Issued at 915 PM CST Thu Mar 8 2018 Some fog is expanding across the James River Valley north into the Devils Lake Basin so have expended the fog further north. Once again min temperatures are difficult to judge as they are rapidly falling across the north central where the remnants of the surface high remain. So dropped temperatures there 5 to 10 degrees. UPDATE Issued at 556 PM CST Thu Mar 8 2018 Current radar trends show a large area of snow extending from Glasgow MT southeast through Wolf Point to near Glendive MT. Bowman radar shows virga but not much reaching the ground yet. Web cams still look dry southwest. So will keep the POP trends going for the evening as is. Current forecast looks ok so far. && .SHORT TERM...(This evening through Friday) Issued at 116 PM CST Thu Mar 8 2018 For tonight, an initial surge of warm air advection could produce some light snow across western North Dakota after 00z and into central North Dakota overnight. Any snow that does fall will be light and amount to general a tenth of an inch or less. A moist boundary layer, and light upslope winds may lead to fog once again for the southern James and Missouri River Valleys. The HRRR and SREF are hinting at perhaps even more widespread fog than what is currently forecast, but confidence in fog developing further north and west is not as high and therefore kept the mention of fog isolated to the southern river valleys. .LONG TERM...(Friday night through Thursday) Issued at 116 PM CST Thu Mar 8 2018 A cold front will follow for Friday night/Saturday. With a lack of moisture aloft leading to a lack of ice crystals, soundings indicate the potential for periods of light freezing rain to mix in with snow. Any periods of light freezing rain should be brief, and with little moisture/lift to work with accumulation and therefore impacts should be minimal. Breezy northwest winds 15 to 25 mph will develop behind the cold front Saturday. There should be enough of a crust on the snowpack to limit drifting or blowing snow, thus only patchy blowing snow seems reasonable at this time with minimal or low impacts. Highs Saturday will reach the lower to mid 30s. An upper level ridge takes control from the Northern Rockies into the Northern High Plains Sunday through Wednesday. Expect dry weather with a moderating trend, as highs will reach into the 30s and 40s Tuesday and Wednesday. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 556 PM CST Thu Mar 8 2018 Low pressure centered across southwest Alberta Thursday evening with an associated warm front through Montana is forecast to lift northeast tonight and Friday. The warm front will be the focus for snow across southwest and south central North Dakota tonight. Fog is expected to form across the James river valley tonight an possibly extend into KBIS-KMOT in moist southeast wind flow. Expect deteriorating conditions to MVFR late this evening and overnight with IFR conditions in FZFG at KJMS after 06z. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...WAA SHORT TERM...AJ LONG TERM...AJ AVIATION...WAA