Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/13/18

Area Forecast Discussion
National Weather Service Bismarck ND
954 PM CDT Thu Apr 12 2018 .UPDATE... Issued at 948 PM CDT Thu Apr 12 2018 Will maintain the current winter weather headlines across southwest and south central North Dakota without changes. Did add a mention of fog across the southwest per NDDOT webcam trends through 0240 UTC depicting areas of dense fog with easterly upslope flow prior to the onset of moderate to heavy snowfall. Patchy freezing drizzle is possible. UPDATE Issued at 715 PM CDT Thu Apr 12 2018 No changes to ongoing headlines at this time. Light to moderate snowfall will continue this evening across southwest North Dakota with easterly upslope flow and a shortwave across southeast Montana. Precipitation intensity will increase late tonight into Friday morning with increasing upper level diffluence and the impacts of a jet streak. With near freezing surface temperatures and strong easterly winds, compaction of snowfall will likely play a significant role impacting snow ratios. Widespread 4-6 inch totals across the Winter Storm Warning area are reasonable by late Friday morning, with pockets around 8 inches. This is generally depicted by the Cobb snowfall technique applied to the RAP and HRRR through their 23 UTC iterations, but, lower than a thickness approach. The most likely upgrade would be Dunn county from an Advisory to a Winter Storm Warning. This will continue to be evaluated through the evening. && .SHORT TERM...(This evening through Friday) Issued at 305 PM CDT Thu Apr 12 2018 Current headlines look reasonable with no changes to current warnings and advisories from previous forecast. The snow amount forecasts continue to show a sharp delineation due primarily to the forecast qpf which generally follows the H700 mb flow/low. We continue to expect 6 to 8 inches of snowfall across the southwest with 1 to 2 inches east of the Missouri river. Strong winds continue to be a concern Friday as the storm wraps up and moves east. Went with CONSMOS for wind guidance tonight through Friday. Without much snowfall there appears to be a limited blowing snow potential, although this was considered for the southern James River Valley. Rain will change to a rain/snow mix late this afternoon southwest, then to all snow tonight. Looks like there will be a potential for freezing rain/drizzle across the south central, east of the Missouri River Valley late tonight and Friday as there appears to be a lack of ice crystals in the soundings across this area. .LONG TERM...(Friday night through Thursday) Issued at 305 PM CDT Thu Apr 12 2018 By Friday evening the stacked storm system is forecast to be centered over NE/KS/IA area, with the precipitation envelope surrounding the storm system essentially south of our area, still affecting central and eastern South Dakota, southern Minnesota and southward. Gusty north winds will linger across south central North Dakota Friday night, with some drifting snow lingering in southwest and far south central North Dakota. Saturday through Monday: Upper level ridging builds into the Dakotas in the wake of the departing storm system. Mainly dry weather, with a slow warm-up. Highs Saturday in the 30s rising to highs Monday in mainly in the 40s. Monday night through Tuesday night: The next storm system moves into the Pacific Northwest Sunday, strengthening as it progresses across the Rockies, and emerging into the Front Range and western Plains Monday. The models then split this system: The northern stream lifts northeastward into Alberta/Saskatchewan Monday night/Tuesday and into northern Manitoba Wednesday...and the southern portion of the system emerges out of the base of the main trough near the 4-corners, moving east across the central Plains around Nebraska before lifting northeastward towards the Great Lakes on Wednesday. For North Dakota, the consensus of the models suggests mainly a glancing blow, with chances of rain or snow Monday night through Tuesday night. The best CAPE with this system remains associated with the southern stream, but the GFS is depicting a short window Monday night over western North Dakota, and we will continue to monitor this for thunderstorm potential. Still below average temperatures with highs in the 40s with lows in the 20s and 30s. Wednesday and Thursday: Broad upper level ridging builds into the region, allowing mainly dry conditions. Below average temperatures remain with highs in the 40s to lower 50s...and lows in the 20s to lower 30s. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 948 PM CDT Thu Apr 12 2018 Widespread IFR/LIFR conditions this evening in fog, stratus, and snow across southwest North Dakota becoming LIFR/VLIFR tonight into Friday morning in snow and blowing snow. MVFR/IFR stratus northwest and south central will continue through the night, with increasing ceilings possible northwest by Friday morning. Strong northeast winds gusting around 35 kts across the James River Valley and far south central North Dakota Friday. Improving ceilings and visibility area wide Friday afternoon and evening. && .BIS WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 7 PM CDT /6 PM MDT/ Friday for NDZ017-018-034-042-045. Winter Storm Warning until 6 PM MDT Friday for NDZ031>033-040- 041-043-044. && $$ UPDATE...PA SHORT TERM...WAA LONG TERM...JV AVIATION...PA
Area Forecast Discussion...Updated
National Weather Service Billings MT
911 PM MDT Thu Apr 12 2018 .UPDATE... Drier air working into the area from the south at the mid levels and low level moisture transport from the east is beginning to get tapped out a bit as thunderstorm activity develops over the Western Dakotas and northeast Wyoming. Net result is best band of precipitation is currently over the northern tier of the region and circulation which had been over the area is beginning to shear apart and window for heavy snowfall is beginning to taper off. Latest run total snow from RAP model shows an inch or less accumulation along and south of the Yellowstone until one gets east into Treasure county. Along with this temperatures are remaining steady in the mid to upper 30s tonight in the Billings area which will have a limiting effect on snow ratios. Have dropped some of the advisories including Yellowstone County. borsum && .SHORT TERM...valid for Fri and Sat... Upper trough moving through Idaho this afternoon. There is a good deal of induced forcing due to height falls, upper diffluence and isentropic lift out ahead of it. This is producing widespread moderate precipitation across portions of the CWA this afternoon. The mountains and foothills have seen a mix of rain and snow turn to mostly snow already. Models agree the upper low will track east into southern Montana tonight before shifting southeast into the central plains on Friday. This will result in a relative dry slot over the southeast zones of our CWA tonight (mainly easter Sheridan County to Powder River) before it fills in early Friday morning. Our central and western zones will be the focus of the main wrap around moisture and isentropic lift as the surface low develops right over the southeast corner of Montana overnight. The position of the surface low along with a weak trowal feature will create very brisk northerly winds over the northern and central sections of our forecast area. Despite the wet nature of the snow overnight, this will probably result in blowing snow and some drifting. As such, we will increase the areal coverage of blowing snow overnight. Road surface temps drop after sunset of course so the chance of accumulations on the roads increase after 8 PM. Some areas though may not see much accumulate on roads until after midnight. Look for a slick and/or slushy morning commute Friday for many locations. Precipitation will gradually wind down on Friday, with little if any additional accumulations for most areas in the afternoon. Highs will be in the 30s to lower 40s, except for the southeast corner where 20s will prevail as clouds and precip linger there most of the day. Models suggest road temps in most areas will warm into the 50s and 60s Friday, so we do expect most snow/slush covered roads to melt off through the day. Some modest ridge building is progged for Saturday, but there is a weak perturbation in the flow that may produce a few showers over the mountains and nearby areas. BT .LONG TERM...valid for Sun...Mon...Tue...Wed...Thu... Models are in fairly good agreement this weekend into the middle of next week. High pressure ridging will be in place early Sunday then gets shifted east into the northern high plains in response to a large upper low and trough that will move onto the Pacific northwest coast. A southwest flow aloft will prevail from late Sunday into Monday. The trough moves across the forecast area Monday and Tuesday with both the GFS and ECMWF keeping the upper low north of our forecast area across Southern Canada. At this time, this scenario will result in scattered showers and no major precipitation event. However, this upper low may bring some very strong west/northwest winds across the forecast area on Tuesday. Ridging then builds across the forecast area Wednesday. Models bring another low onto the west coast Thursday but this one drops southeast into the Four Corners region keeping a split flow aloft across our area. Overall, no major storm systems at this time with temperatures seasonal Sunday, above normal Monday and possibly Tuesday, before cooling below normal Wednesday into Thursday. Hooley && .AVIATION... Most of the rain showers have switched to snow at this point. Most locations, even if they don`t see snow, well see stubborn MVFR/IFR cigs through the night. LIFR conditions possible in the heavier snow showers generally north and east of KBIL. Conditions slowly improve late Friday as the storm system moves out of the region, but mountain obscurations are likely through the TAF period. Dobbs && .PRELIMINARY POINT TEMP/POPS... Fri Sat Sun Mon Tue Wed Thu ----------------------------------------------------------- BIL 029/039 026/051 033/059 035/059 036/048 030/049 028/050 78/O 01/B 11/B 11/B 42/W 11/N 11/B LVM 028/042 025/051 032/061 035/060 032/047 026/048 025/049 74/O 02/W 22/W 13/W 64/W 22/W 12/W HDN 029/039 023/052 030/058 033/060 034/048 027/047 025/050 79/O 00/B 11/B 10/B 32/W 11/B 11/B MLS 027/035 019/045 029/055 032/055 035/046 029/044 026/049 +9/S 01/B 10/U 10/U 22/W 11/N 11/B 4BQ 027/034 019/046 028/057 033/058 036/047 027/045 026/049 79/S 00/U 00/U 00/U 12/W 11/N 01/B BHK 024/032 012/039 023/045 027/045 031/045 027/041 023/044 98/S 00/U 10/U 00/N 12/W 11/N 01/B SHR 028/036 022/051 029/063 032/063 035/050 027/049 025/051 78/S 20/B 11/B 00/U 22/W 10/B 01/B && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...Winter Storm Warning in effect until 6 PM MDT Friday FOR ZONES 28>33-37-42-63-67-68. Winter Weather Advisory in effect until 6 PM MDT Friday FOR ZONES 36-38-40-41-56-58-64>66. WY...Winter Weather Advisory in effect until 6 PM MDT Friday FOR ZONES 98-99. && $$
Area Forecast Discussion
National Weather Service Columbia SC
743 PM EDT Thu Apr 12 2018 .SYNOPSIS... High pressure centered off the coast will continue ridging into the southeastern states through Saturday. This will produce southerly flow over the region along with a warming trend. A cold front will cross the area Sunday into Sunday night bringing showers and thunderstorms. Dry weather and cooler temperatures will arrive Monday with moderating temperatures through the middle of next week. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... Fair. The center of surface high pressure will remain just to our east. Low level air still fairly dry, but some patchy fog possible around sunrise mainly in fog prone locations. Overnight lows will be low to mid 50s. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/... An upper ridge and increasing southerly flow ahead of an approaching storm system and associated cold front will yield generally dry and warm weather during this period. Increasing low level moisture from southerly flow around the surface high centered offshore will support the possibility of some morning stratus or fog (though stratus is favored with a 30 knot low level jet). However, any low clouds should dissipate quickly with surface heating and mixing and transition to a diurnal induced cumulus field as temperatures rise into the lower 80s. Continued southerly winds through the overnight hours Friday night along with general airmass modification will result in above normal lows in the upper 50s. Atmospheric moisture will continue to increase over the area with persistent southerly flow off the Gulf of Mexico as precipitable water values rise over an inch by Saturday afternoon with some weak instability developing due to solar insolation. Forecast soundings show a substantial subsidence capping inversion around 700mb that may inhibit any convection that may try to develop so will continue with our current forecast of only slight chance pops in the western Midlands and upper CSRA where moisture is a bit better. Temperatures on Saturday will again be warm in the 80s but how warm will depend on amount of cloud cover that is present. The approaching cold front will stall to our west over the TN/MS Valleys briefly late Saturday into Saturday night as the upper trough amplifies a bit more and this will keep most of the precipitation to our west. Will continue to carry chance pops in the western portion of the forecast area after 06z Sunday though as the system approaches. && .LONG TERM /SUNDAY THROUGH THURSDAY/... Active weather with the threat of severe weather and heavy rain expected on Sunday to start the extended forecast period but then a return to seasonable temperatures and relatively quiet weather expected for the remainder of the forecast period. Strong upper low over the Upper Midwest will move into the Ohio Valley on Sunday pushing a cold front into the forecast area late Sunday into Sunday evening. Ahead of the front, several ingredients for possible severe weather or heavy rainfall will come together. Strong moisture transport off the Gulf of Mexico will support precipitable water values rising to over 1.5 inches with dewpoints pushing into 60s. Increasing shear with a southerly 850mb low level jet of 50-60 knots will allow for organized convection to develop and the region will fall in the favorable right entrance region of the upper jet during peak heating while the upper trough also becomes negatively tilted. SPC has outlooked the area in a 15% risk for severe weather and we have been mentioning this threat for a few days now. Late afternoon into early evening still appears to be the timing for most significant weather and possible severe storms but instability remains one of the ingredients that may or may not develop depending on cloud cover. Will continue categorical pops across the region on Sunday with a decrease in pops Sunday night as the front crosses and a dry slot beneath the upper low moves overhead. Generally fair weather expected the remainder of the forecast period with surface high pressure over the region and northwesterly 500mb flow on Monday supporting below normal temperatures followed by a transition to more zonal flow and temperatures warming back to near normal. Breezy conditions will exist on Monday due to an increased pressure gradient and may linger into Tuesday. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... VFR conditions most of the period although patchy fog expected late tonight at fog prone terminals...AGS/OGB. High pressure will remain off the Carolina coast through the period with resulting increasing south flow. The air mass at the present time is quite dry. The models suggest a shallow low- level jet overnight which may limit fog potential. Will continue forecast of a brief period of MVFR fog around dawn at AGS and OGB due to model blend suggesting a threat in the CSRA. However there is little support from the latest HRRR and lamp guidance. South to southwest winds increasing to around 10 knots mid morning Friday with scattered cumulus in the afternoon. EXTENDED AVIATION OUTLOOK...Restrictions expected Sunday and Sunday night as a cold front crosses the region along with showers and thunderstorms. Strong and gusty winds expected Sunday through Monday. && .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. && $$
Area Forecast Discussion
National Weather Service Caribou ME
1021 PM EDT Thu Apr 12 2018 .SYNOPSIS... Low pressure will track eastward from the Great Lakes region overnight. A cold front from northern Canada will approach Friday and cross the region Friday night. && .NEAR TERM /THROUGH FRIDAY/... 1010 PM Update... Rain is moving in from the sw per the latest radar loop with either some sleet or snow in the southern sections of Piscataquis County such as Greenville. Temperatures in that region were in the low to mid 30s. Elsewhere, temps were in the 40s but were slowly cooling down. Given the low dewpoints across the northern areas, expecting the rain to go to snow w/some accumulation. Decided to stay close withe current forecast for 1-2 inches of wet snow by morning mainly across northern Aroostook County. Attm, the radar does show some enhanced returns across southern Maine. Ltg detection did show some strikes moving across eastern NYS. This activity looks like it will dampen as it moves east overnight. 00z ua showed upper jet of 100+ kts moving out of western NYS and is shown by the RAP and NAM12 to move across the southern portion of the region overnight. This feature is helping to fuel the tstms in eastern NYS and could very will enhance precip for a few hrs overnight. Decided to adjust the QPF to account for terrain and this embedded convection. Previous Discussion... Low pressure will track out of Quebec into northern Maine tonight. The expected path is from Somerset County towards southern Aroostook County. This track will be conducive to snow north of the low...after evaporative cooling of the boundary layer...and rain to the south. The surface low will line up with a compact H500 shortwave and the LFQ of a strong upper jet. There is some elevated instability coinciding with this jet...currently in Ontario. This instability will weaken, but still poses a risk towards coastal Hancock later tonight and will have to be watched. QPF with the system looks to be mostly in the quarter to half inch range. Snow is a threat north of a line Greenville eastward towards Houlton. The snow will be dependent on elevation, evaporative cooling, and intensity. In general, most of the lower elevations under 1000ft will see one to two inches and a lot of that will come within a couple of hours when snowfall rates could hit an inch an hour...wiping out the warm boundary layer. This could pose some brief travel difficulty in the northern zones, but with lows around 33F, it should be short-lived. There will be a strong LLJ to help enhance this heavier burst of precip. By late tonight, this fast-moving low will already be in New Brunswick. In general, the air behind the low will be milder and moister with highs tomorrow another couple of degrees warmer than today. Dew points will also be considerably higher. However, there will be sufficient H850 for a lot of cumulus fields on Friday...and higher clouds will increase with overrunning later in the day. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/... Expect strong high pressure to build to the north of the region across Canada Saturday and Sunday. At the same time a front will remain stationary across to the south. Expect the front to start to move to the north later Sunday along with precipitation. Expect the precipitation to start as snow and mixed in the north and central areas Sunday Night then change to all rain by Early Monday. Have used the thickness tool run on a 50/50 blend of the Nam and Gfs for precipitation type. Used snow ratio for snow amounts. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Intensifying low pressure will track to the west of New England Monday. Expect heavy QPF amounts Monday and Monday Night as it does so. Rapid snow melt is possible. The upper level low pressure system is expected to move across the region Tuesday bring showers Tuesday into Wednesday. Showers are expected to continue Thursday as upper level low pressure remains over the northeast. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... NEAR TERM: All sites will deteriorate from VFR towards IFR or LIFR tonight. The LIFR will occur in snow north of a line from GNR to HUL. South of that line, rain will be accompanied by IFR cigs. There is a slight chance of an embedded thunderstorm towards BHB later tonight. LLWS will be an issue late this evening into the overnight hours for all sites. Conditions improve quickly towards VFR Friday morning. SHORT TERM: Expect VFR/MVFR conditions Saturday. MVFR/IFR conditions are expected Sunday. IFR conditions are expected Monday and Tuesday. && .MARINE... NEAR TERM: Winds and seas will increase quickly tonight with some gusts over 35 kts after midnight...especially further from the coast. There is a slight risk of a thunderstorm tonight. The rain ends later tonight and winds will decrease for Friday, but seas will continue to build Friday morning in a southerly swell up to 10 feet. Seas gradually decrease in the afternoon, but the SCA will remain in place. SHORT TERM: Have used a 50/50 blend of the Nam and Gfs for sustained winds. For Waves: Expect southerly long period swell 3-4 feet/8 seconds to be the primary wave system Saturday and Sunday with a secondary northeasterly wind wave 2-3 feet/4-5 seconds. A strong east to southeasterly fetch will develop across the Gulf of Maine Sunday Night into early Tuesday with waves build to around 9 feet/9 seconds by late Monday Night. Will use NWPS for wave heights. && .CAR WATCHES/WARNINGS/ADVISORIES... ME...None. MARINE...Small Craft Advisory until 2 AM EDT Saturday for ANZ050>052. && $$ Near Term...Hewitt Short Term... Long Term... Aviation...Hewitt/ Marine...Hewitt/
Area Forecast Discussion
National Weather Service Charleston SC
1011 PM EDT Thu Apr 12 2018 .SYNOPSIS... High pressure will prevail through Saturday. A strong cold front will affect the area Sunday, followed by dry high pressure Sunday night through mid week. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... On average our temperatures are running about 3-6F warmer than 24 hours ago, and this trend will persist through the overnight as it provides us with our "warmest" night of the past several. We`ll continue to keep watch on the development of patchy stratocumulus from off the ocean late as weak isentropic ascent and low level moisture advection occurs. Still no indications of significant fog formation as per the bulk of the Hi-Res model guidance since condensation pressure deficits are more than 10 or 20 mb and geostrophic winds are 10-15 kt. We`ll maintain mention of "patchy" fog late, generally in the form of ground fog. Previous discussion... For the early evening update we have adjusted sky cover to reduce coverage early tonight based on satellite trends, but also to increase it a little late due to some isentropic ascent and an increase in boundary layer moisture from off the Atlantic. This will lead to some late night stratocumulus, as skies transition from clear/mostly clear to partly cloudy closer to daybreak. Meanwhile, the fog potential is not extremely high, with the NARRE-TL, SREF and HRRR all showing little if any chance. However, since dew points are higher and since "patchy" fog is already mentioned in the forecast, we will leave it there. Suspect that most of it will be shallow ground fog though. Weak warm air advection within a southerly low level flow and the dew points in the 40s and 50s will prevent temps from getting as cool as last night. We did lower some places in the Francis Marion and along our NW tier for minimum temps, but elsewhere we maintained the previous forecast of lows from earlier. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/... Overview: A relatively quite pattern will hold on for Friday and most of Saturday, but then more active weather is expected to return ahead of a strong cold front on Sunday. Friday and Saturday: A deep layer ridge, centered over the Atlantic waters, will gradually push eastward through the period. Low level southeast flow will prevail with only a slight chance for showers by Saturday/Saturday afternoon, mainly extreme coastal/eastern locations. Temperatures will be above normal, with highs both days in the upper 70s to around 80, and lows Friday night in the upper 50s to lower 60s. Given the prevailing low level southeast flow, temperatures will be cooler each afternoon closer to the coast. Saturday night and Sunday: The pattern becomes more active as a deep, full latitude upper trough approaches from the west. Moisture will continue to increase from west to east, with a slight/low end chance for showers after midnight Saturday night into early Sunday morning. All models are in close agreement with the timing of the deepest moisture, upper forcing and highest chances for showers/thunderstorms for generally 18z Sunday to 00z Monday. Have gone likely to categorical PoPs by Sunday afternoon. This would coincide with peak heating, which could maximize CAPE. As has been typical, instability/CAPE seems to be the limiting factor, with more than sufficient deep layer shear/winds. However, latest global models now nudge CAPE values near 1000 J/Kg, which would likely be enough to support isolated severe storms. Given the unidirectional wind profiles in the model soundings, if there are any strong/severe storms, the main threat would likely be strong, straight line wind gusts. It`s too soon to mention severe potential in the grids/forecast, but will continue to highlight in the HWO. All models also indicating breezy to windy low level conditions Sunday, and have continued breezy mention in the forecast. Sustained southerly winds of 15-25 mph with gusts 30-35 mph would not be out of the question. High temperatures will be very mild/warm, in the mid to upper 70s. With surface dewpoint temperatures expected to be the mid to upper 60s, it will also feel more humid. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Precip associated with the cold front should be offshore by midnight Sunday night. A brief cooldown will occur Monday into Tuesday before the surface high shifts offshore with a quick warm-up by mid to late week. It will be breezy during the daytime hours each day due to a relatively strong gradient. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... Ground fog is expected overnight into Friday morning, and although there could be occasional flight restrictions, most of the 00Z TAF cycle will be VFR at both KCHS and KSAV. SE to S winds will become gusty Friday late morning and afternoon, possibly stronger than now in the forecast, since we are showing more in the way of average conditions. Extended Aviation Outlook: Friday through Saturday: VFR expected to prevail. Saturday night: Brief flight restrictions/lower ceilings will be possible late ahead of an approaching cold front and increasing chances for showers. Sunday: All models continue to show an increasing threat for severe storms as a deep upper trough and associated surface cold front move in from the west. Timing for the highest chances for showers/thunderstorms and the potential for isolated severe storms looks to be 18z Sunday to 00z Monday. Therefore, periods of flight restrictions will be possible much of the day and into early evening Sunday. Breezy southerly winds also look likely Sunday and into Monday at both sites. Sunday night through Tuesday: VFR expected. && .MARINE... Tonight: Sprawling high pressure that covers much of the western Atlantic and Gulf of Mexico will persist, with its associated ridge axis to extend over or just south of the local waters. This will produce veering winds around to the SE and S at speeds generally 10 kt or less, except for 10-15 kt on the outermost Georgia waters. Seas will hold steady around 2-3 ft within 20 nm, and 3-4 ft further out. Friday and Saturday: No highlights as high pressure centered just east of the waters continues to slowly push further east into the Atlantic. Expect southeast winds of 15 knots or less and seas 3 to 4 feet. Saturday night: Winds increase from the southeast then south ahead of an approaching strong cold front and deep upper level trough. Expect winds of 15 to 20 knots with gusts near 25 knots by late night. Seas building to 4 to 6 feet, highest offshore GA waters. Therefore, marginal Small Craft Conditions possible, especially offshore waters by late night. Sunday through Monday: A strong cold front and the potential for strong to severe storms will move across the waters later Sunday afternoon and Sunday evening. Winds and seas are expected to increase into the Small Craft Advisory level, with sustained winds of 20-25 knots and gusts near/around 30 knots possible, especially ahead of the front Sunday and Sunday evening. Seas could build as high as 7 to 9 feet offshore/beyond 20 nm offshore, and 5 to 7 feet within 20 nm. Small Craft conditions could linger through much of Monday behind the cold front, before gradually decreasing as high pressure builds into the area from the west. By Tuesday, High pressure is expected to be over the region with lighter winds/lower seas below highlight levels. Rip Currents...Increasing southerly flow late Saturday night and through Sunday ahead of a strong cold front is expected to increase the threat for rip currents. A moderate to possibly high risk for rip currents will be possible by Sunday. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM... SHORT TERM... LONG TERM...JRL AVIATION... MARINE...
Area Forecast Discussion
National Weather Service Gray ME
900 PM EDT Thu Apr 12 2018 .SYNOPSIS... Fast-moving low pressure will move eastward across northern New England overnight, spreading mainly light rain across the area. Thereafter, a frontal boundary will remain nearly stationary to the south of the forecast area and bring the threat for mixed precipitation to NH and ME late Saturday through Sunday night. A more substantial rain event may arrive Monday and Tuesday. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... 900 01z a 1002 millibar low was vicinity of Kingston, ON /CYGK/ with a trailing cold front through the lower Great Lakes and a warm front through eastern New York state. NWS Doppler Radar mosaic showed an area of precipitation in advance of the surface low and occluding warm sector. Precipitation was largely falling as rain with some snow across the higher terrain. For this ESTF update...I made minor adjustments to near term grids that reflect radar trends as well as the latest mesonet. Prev disc... Clouds continue to increase across the forecast area this afternoon as low pressure approaches from the west. This low will bring a widespread light rain to the region this evening into the overnight hours. Followed an ensemble of the latest several HRRR runs for PoPs as it appears to have a good handle on the timing and coverage of rain. Portions of the western ME mountains may pick up a little bit of snow tonight as it should be just cold enough at higher elevations for some wet snow. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... Much of Friday should end up being a partly sunny to variably cloudy as we will be between two fast-moving systems. This will likely be the last warm-ish day in awhile with highs in the 50s and 60s...except for those in the far north. However, some light rain may begin to fall late in the afternoon - mainly across southern and western zones as the next burst of WAA approaches. Mainly light rain is expected Friday night across most of the forecast area as we will be right in or near the stationary frontal zone. Across far northern zones, we expect a transition to sleet/snow later Friday night as the depth of cold air deepens. && .LONG TERM /SATURDAY THROUGH THURSDAY/... Highly amplified flow will impact the region throughout the long term period. At the surface, low pressure system over the central Plains will be in the process of filling by Saturday. An associated warm front will try to push warm and moist air in from the southwest over the weekend. strong high pressure in Canada (1045+ mb) will push a backdoor front into the region from the north. These two air masses will interact and bring a wintry mix of precipitation for most of NH and Maine through the weekend. Models and model members disagree on the timing of the backdoor front, which will be crucial as far as to how far south the cold air gets during this event. Dense high pressure will help in this case, so we are expecting a chance of freezing rain, at least in pockets, across the area. Precipitation will start as rain and gradually change to a wintry mix late Saturday night into Sunday morning. Amounts of snow will be higher in the north and may touch advisory range in certain areas. Roads at this time of year are generally warm enough to handle light freezing rain, but trees and walkways will accrete ice and become slippery. Freezing/frozen precipitation could reach as far south as the coasts. QPF amounts with this system will range from 0.5" in the north to and inch or more for central and southern sections. This is about 150-200% of normal for this time of year. Runoff will mix with snowmelt and will likely cause flooding at multiple points on area rivers. Finally, winds will whip up Sunday night into Monday with a strong LLJ in place. Early next week the large trough axis will swing negatively as it moves towards New England, with secondary cyclogenesis occurring along the coast. Colder air will retreat north from the mountains and foothills by Monday as warm air advection begins. This looks like a straight rain/snow event in the Tuesday/Wednesday time frame. Again QPF amounts look elevated. Cyclonic flow remains in the region through midweek with scattered showers in the forecast. && .AVIATION /01Z FRIDAY THROUGH TUESDAY/... Short Term...Low pressure moving across the forecast area tonight will bring a period of light rain and MVFR cigs/vsbys at most terminals - except perhaps KMHT. VFR conditions are expected to return late tonight and last through much of Friday before lowering to IFR Friday evening and night. Long Term...MVFR ceilings and lower are expected Saturday into Sunday in mixed precipitation. Freezing/frozen precip will being across northern terminals and will gradually shift south, changing rain into SN/-IP/-FZRA at times. Also expecting gusty winds in the late Saturday to early Sunday time frame, with a period of LLWS before the LLJ mixes down. Freezing precip will change over to -SHRA most sites Monday into Tuesday. && .MARINE... Short Term...SCA remains in effect for all waters for tonight and Friday. There will likely be some gusts around 35 kt... especially off the mid coast but we are thinking widespread gales will remain aloft and not likely mix down to the water for a prolonged period of time. Long Term...Small craft conditions continue Saturday into Sunday with gales developing Sunday night into Monday. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...Small Craft Advisory until 8 PM EDT Friday for ANZ150>154. && $$ ES
Area Forecast Discussion
National Weather Service Spokane WA
446 PM PDT Thu Apr 12 2018 .SYNOPSIS... Breezy and gusty conditions along with some potential for thunderstorms will linger this afternoon and early evening. Periods of showers will continue Friday into Saturday with another wet front bringing valley rain and mountain snow on Sunday into Monday. Temperatures will remain generally cooler than normal through the next week with showery and occasionally breezy conditions continuing. && .DISCUSSION... Tonight and tomorrow: Cold conditionally unstable airmass coupled with abundant low level moisture left from recent and ongoing rainfall as a negatively tilted disturbance rounds through the outer edges/base of the trof pushing through Eastern Washington and North Idaho will keep a portion of the evening unsettled with the potential for some thunderstorms. If they do form they would be the weak pulse variety moving with a storm motion to the east/northeast at 15 to 20 mph. Infrequent lightning, gusty wind, and brief downpours would be the primary nuisances associated with any thunderstorms that develop. Otherwise decreasing precipitation segue to a generally dry forecast marks most of the remainder of the overnight into tomorrow morning period. Clouds invade sky from the west and thicken and lower tomorrow morning signaling the approach of the next weather system to bring rain to most locations tomorrow. The breezy/gusty winds will linger into the early evening then decrease. /Pelatti Friday night through Thursday... Another weather system begins to set up position off the west coast. There will be flat shortwave ridging but a slow moving cold front will keep baroclinic band precipitation active over the flat ridge. Generally light precipitation will be in the forecast for Friday night into Saturday with best chances Cascades, northern mountains of Washington and the Idaho Panhandle. As the low slowly digs off the west coast Saturday and Saturday night the flow will turn more southerly ahead of the cold front but surges of moisture continue as the warm sector establishes itself over the eastern third of WA and ID Panhandle. During this time precipitation moves away from the Panhandle and continues over the Cascades. Being in the warm sector, much of the region will enjoy warmer temperatures even into Sunday but moist southerly flow continues so light precipitation or sprinkles in overcast sky will still be possible as well as the slight potential for thunderstorms northeast mountains Saturday. Sunday afternoon and night the cold front begins it`s slow trek inward. We will need to look out for isolated thunderstorm activity in this potentially active frontal passage. There will also be widespread showers moving across the region persisting into Monday. Monday, expect cooler temperatures after the cold front with lingering rain and snow showers as convective showers will artificially lower snow levels and some valley locations will see the white stuff. However this time of year snow does not stick around long even if it accumulates a little in the lower valleys. There are some impressive precipitation totals for this storm system especially for northeast mountains and north Idaho Panhandle. This will continue to help swell creeks, streams and rivers however no flooding is forecast. Debris/Rock slides are still a concern as several have been reported this Spring during and after heavy precipitation events like this. With yet more minor disturbances in the overall weak westerly flow we can expect on an off again showers Tuesday into Thursday especially in the mountains. However temperatures will be on the rebound to more normal values in the 50s (near 60 south) during the day Wednesday and Thursday. TC && .AVIATION... 00Z TAFS: Upper trough pivots through the region while satellite shows a weak circulation over the Columbia Basin. Convection is blooming east of the circulation over Adams, Lincoln and Whitman counties with showers, some of which with graupel and a threat of lightning. The HRRR shows the convective activity skirting pass the KGEG-KCOE corridor and toward KPUW through 03z with gusty winds, and then dissipating through the evening. KMWH-KEAT should stay dry and windy this evening. Clearing anticipated overnight with lighter winds. Clouds increase 16-18z as winds become southeast. Light rain anticipated after 18-21z with an approaching front with local MVFR cigs possible. /rfox. && .PRELIMINARY POINT TEMPS/POPS... Spokane 31 49 40 55 40 56 / 20 40 50 30 30 60 Coeur d`Alene 30 48 39 53 39 55 / 20 30 70 40 30 60 Pullman 32 49 40 55 40 57 / 20 30 60 20 20 60 Lewiston 35 57 44 62 44 63 / 20 10 40 20 20 50 Colville 30 51 40 55 39 54 / 20 40 60 60 60 60 Sandpoint 30 45 38 49 37 51 / 30 30 80 60 40 70 Kellogg 29 45 35 50 36 53 / 20 20 70 40 30 70 Moses Lake 33 57 42 62 41 60 / 20 30 20 20 30 60 Wenatchee 36 56 41 58 41 54 / 10 40 20 40 50 60 Omak 34 55 41 58 41 55 / 0 50 30 50 40 80 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$