Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/14/21

Area Forecast Discussion
National Weather Service Boston/Norton MA
928 PM EST Sat Feb 13 2021 .SYNOPSIS... Active weather starting tonight, with weather systems tonight and every day except Wednesday. Each weather system will bring a mix of weather types. Light amounts are expected tonight. Then another light wintry mix is possible on Monday before a more potent storm could bring significant ice accretion to much of Southern New England on Tuesday. We dry out briefly on Wednesday before another significant winter storm arrives late Thursday into Friday with all precipitation types possible. Below normal temperatures are expected through the end of the week. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... 925 PM Update: Expanded the Winter Weather Advisory northward to include all of Rhode Island and the remainder of Bristol and Plymouth Counties. Current radar shows the northern end of the precip shield from roughly Willimantic CT to Pawtucket RI eastward into Marshfield MA. Spotters and mPING reports indicate very light precip, either as snow, "snizzle", or freezing rain across parts of RI, with FZRA also being reported at TF Green Airport. Think the HRRR is presently handling the precipitation shield the best, which matches roughly where the Advisory was expanded into. Following this, light precipitation should continue into a good part of the overnight (about 08z). We do lose cloud ice after midnight following NBM cloud-ice probs so transition from frozen precipitating types (S/PL) to freezing drizzle appears on track. Any icing will not amount to anything more the a light glaze and on the whole be fairly spotty, but it doesn`t take much to cause slick roads and sidewalks. Further north into interior MA and into Greater Boston, precip may end up being very spotty if any develops at all. Previous discussion: BOX radar shows the leading precip shield moving into southern CT/RI with little making it to the surface thanks to a large dewpoint depression. But, as we head into the overnight hours that gab will close. We still anticipate that the majority of southern New England sees less than an inch of snow. Coastal areas are at the highest risk for ice accretion - up to a tenth of an inch. While it is still relatively quiet we only have to look just to our neighbors on Long Island - there freezing rain is being reported along the south central coast. Only changes that were made were to bump up POPs along the coastal areas of CT/MA/RI. Overall the messaging remains the same and you can read that in the prior discussion below. =============================================================== Low pressure along the Carolina coast moves northeast tonight to a point well south of Nantucket. A 130-kt upper jet feeds between the coastal system and the South Coast, providing some support of lift during the night. Snow and freezing rain observed over the DelMarVa area will move into Srn New England tonight. Warm air moves northeast into at least the coastal areas and possibly to the Mass Pike. This suggests a mix of precip across the region. If anyone stays all-snow, it would be Northern MA. Based on Bufkit GFS soundings northern CT/RI mix/change to sleet but not freezing rain. The NAM soundings are a little warmer with an hour or two of freezing rain at BDL. For now we will hold the freezing rain to our South Coast with snow/sleet farther north. Even this may be limited, as the soundings show dry air at the ice nucleation level, which may result in freezing drizzle rather than snow/sleet. Will add freezing drizzle to the list of forecast p-types. Expect QPF of up to 0.10 inches, maybe 0.15 on Cape/Islands. This suggests snow/sleet of a coating to an inch and South Coast FZRA of a few hundredths. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/... Sunday... The coastal system passes south of the 40N/70W benchmark and moves off well south of Nova Scotia. Expect drying in upper parts of the column, but lingering moisture in the low parts. This work against any snow/sleet, but may allow drizzle/freezing drizzle during late morning and early afternoon. Low level temps aloft suggest max sfc temps in the 30s, therefore the potential for both forms of drizzle. Sunday night... High pressure in the Plains and across Eastern Canada will maintain a north-to-south surface flow overnight. Plenty of moisture remains in the column for clouds, but jet dynamics are not favorable and IVT is still aimed over Georges Bank and farther offshore. Advection ahead of the next system will start approaching late at night, but remain offshore during the night. Expect min sfc temps ranging from the upper teens northwest to the lower 30s southeast. && .LONG TERM /MONDAY THROUGH SATURDAY/... Highlights... * Light wintry mix possible on Monday, followed by a more potent storm on Tuesday with significant ice accretion possible. * Dry and cold on Wednesday and possibly first part of Thursday with 1040 mb high over New England. * Another potent winter storm late Thursday into Friday with all precipitation types on the table. * Turning colder but dry on Saturday. Overall pattern... Overall, a very active weather pattern in the long term. The CPC 6- 10 day outlook gives a 30-40 percent chance of below normal temperatures and 40-50 percent chance of above normal precipitation. A deeply negative Arctic Oscillation (AO) is forecast to increase sharply over the upcoming week, turning neutral or even slightly positive. When a rapid change in the AO occurs, we typically get into a very active weather pattern here in Southern New England. Unfortunately, due to the thermal profiles, we will be dealing with a variety of wintry precipitation, instead of straight rain and/or snow. On the synoptic scale, we are in a persistent H5 ridge that promotes SW flow aloft but at the low levels, we have E/NE flow from an inverted trough axis which will result in considerable low level cold air drainage and moisture. So while we get into +5 and even +10C at 850 and 925mb, it remains sub-freezing near the surface. And per the CIPS analog threat guidance, this is a classic setup for freezing rain. If the sub-freezing layer near the surface is deeper, then we may get more sleet than ice. The details... The two main windows for significant ice accretion appears to be late Monday into Tuesday and late Thursday into Friday. It is also possible that we have to deal with a light wintry mix on Monday and all it takes is a glaze of ice to cause travel issues. But this will probably be the appetizer ahead of the main course, that is, the potential ice storm. It is quite concerning that both the NAEFS and EC ENS Situational Awareness Table show 99.5 percentile for QPF, PWAT and Integrated Water Vapor Transport (IVT) for our area on Tuesday and Friday. In other words, we will have a lot of moisture to deal. The timings are not set in stone at this time frame, but the threat for significant icing and consequently, hazardous travel conditions exist for this upcoming work week. People with travel plans will want to monitor the forecast closely. As for possible ice accretion amounts, that too is extremely challenging given observed amounts and impacts could vary greatly on the microscale level. The criteria for an Ice Storm Warning is half an inch of ice accretion and the initial thinking is that we could be pushing widespread quarter inch ice accretion with up to half inch possible. Again, if the low level cold air is deeper, it could be more sleet than ice especially for the interior. On the flip side, if the surface temperature warms a bit quicker to above freezing, then it could be a brief period of sleet and/or freezing rain before a transition to plain rain. This would be possible for areas along and near the South Coast. Headlines wise, we are not issuing any headlines right now for the long term due to the active weather in the near and short term. However, an Winter Storm Watch is certainly a possibility for these two events, which requires a 50 percent confidence of hitting criteria, in this case, half an inch of ice accretion. Of course, there is also the possibility of the warm nose aloft being not as stout and if that happens, we could be looking at a few inches of front-end thump snow. So we could also be hoisting Winter Storm Watches for the possibility of 6 inches of snow. Also of note is the risk for power outages due to a combination of heavy, wet snow/sleet and/or ice accretion. The good news is that Wednesday and Saturday look dry with surface high pressure in control. But overall, this week looks like an utter wintry mess with Wednesday and Saturday looking like windows of opportunity for clean ups. The forecast is extremely challenging and given the amount of uncertainty with timing and precipitation types, have opted to keep the discussion not overly specific. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... Forecaster Confidence Levels. Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Overnight... Ceilings lower from VFR evening to IFR late at night. Vsbys lower as a mix of precipitation arrives...generally 1 to 3 miles in NE CT, RI, SE MA and 4 to 6 miles farther north and west. Precip types favor snow/sleet from northern CT through Metro Boston, and snow changing to freezing rain along the south coast/islands. Precip starts around 9PM-Midnight and continues overnight. Amounts should be light. Sunday... Precipitation tapers off during the morning. Lingering drizzle or freezing drizzle through midday. Ceilings at IFR in the morning...improving to MVFR in the east and VFR in the west. Sunday night... Clouds linger, with VFR conditions most places and MVFR cigs over RI and SE Mass. KBOS TAF...High confidence in TAF. KBDL TAF...High confidence in TAF. Outlook /Monday through Thursday/... Washingtons Birthday: Mainly IFR, with areas MVFR possible. Chance RA, chance SN, chance PL, chance FZRA. Monday Night: Mainly IFR, with areas MVFR possible. Breezy. Chance RA, chance FZRA, chance SN, chance PL. Tuesday: MVFR/IFR conditions possible. Breezy. PL, RA, FZRA, chance SN. Tuesday Night: Mainly VFR, with local IFR possible. Breezy. Slight chance FZRA, slight chance SN. Wednesday: VFR. Breezy. Wednesday Night: VFR. Thursday: Mainly IFR, with local VFR possible. Breezy. SN likely, chance FZRA. && .MARINE... Short Term /Tonight through Sunday night/ East winds may become borderline for Small Craft Advisory on the outer waters south of RI, while remaining waters will be 20 kt or less. The steady east wind will build seas on the southern outer waters, with heights of 5-6 feet. Will issue a SCA for our ANZ254 to ANZ256 waters for Tonight through Sunday night. Periods of light wintry precip overspread tonight, then move off during Sunday morning. This could reduce visibilities down to 1-3 miles at times tonight. Outlook /Monday through Thursday/... Washingtons Birthday: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of rain, slight chance of freezing rain. Monday Night: Winds less than 25 kt. Seas up to 5 ft. Rain, freezing rain likely. Tuesday: Moderate risk for Small Craft Advisory winds with gusts up to 25 kt. Areas of rough seas. Rain, sleet, freezing rain. Local visibility 1 to 3 nm. Tuesday Night: Low risk for Small Craft Advisory winds with gusts up to 25 kt. Rough seas up to 8 ft. Slight chance of freezing rain, slight chance of snow. Local visibility 1 to 3 nm. Wednesday: Winds less than 25 kt. Areas of rough seas. Wednesday Night: Winds less than 25 kt. Areas of seas approaching 5 ft. Thursday: Winds less than 25 kt. Areas of seas approaching 5 ft. Chance of snow, rain likely, chance of freezing rain. Visibility 1 to 3 nm. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...Winter Weather Advisory until noon EST Sunday for MAZ017>024. RI...Winter Weather Advisory until noon EST Sunday for RIZ001>008. MARINE...Small Craft Advisory until 6 AM EST Monday for ANZ254>256. && $$ SYNOPSIS...WTB/Chai NEAR TERM...WTB/Chai/Gaucher SHORT TERM...WTB LONG TERM...Chai AVIATION...WTB/Chai/Gaucher MARINE...WTB/Chai
Area Forecast Discussion
National Weather Service Caribou ME
931 PM EST Sat Feb 13 2021 .SYNOPSIS... High pressure will move northeast of the region by Sunday, as weak low pressure tracks well south of the region. Another High is expected to cross the region Sunday night into early Monday followed by an upper level disturbance crossing the area later Monday into Monday night. Low pressure will approach from the southwest Tuesday and move south of the region Tuesday night. High pressure builds in on Wednesday and Wednesday night before another low pressure approaches from the southwest late Thursday. && .NEAR TERM /THROUGH SUNDAY/... 930 PM Update: The arrival of thicker hi cld cvr have result in temps not falling as fast into the late eve ovr Nrn areas as prev thought, so fcst lows were ovr this area were raised a few deg F, particularly ovr the colder vly areas. Otherwise, fcst hrly temps/dwpts were updated to erly ovrngt lows posted arnd 1 to 2 am from trends seen from latest avbl sfc obs. Prev Disc: High pres will ridge into the region tonight allowing for light winds and mostly clear skies intially, before clouds arrive later at night as low pres apchs from the sw. The ridge axis from that high will lift out to the ne overnight. High clouds were pressing ene per the latest satl imagery and will continue to advance and gradually lower and thicken up overnight. Temps will be allowed to drop off rather quickly after sunset. The high clouds are still rather thin to allow for some radiational cooling across the central and downeast areas w/overnight temps hitting the single numbers before leveling off after midnight. Across nrn and nwrn areas, clear skies will hang on longer to allow for good radiational cooling and some very cold temps. Inversion in place will allow for temps to hit well below zero before clouds arrive by early Sunday morning, especially in the low lying areas. Low pres is forecast to develop off the mid Atlc coast tonight and lift ne on Sunday passing well s of the region. As it does so, an inverted trof extending out from the low is shown by the model guidance to setup over western New England and push to the east. Two areas of precip are forecast to set up w/one area associated w/the low passing well s of the region and the other associated w/the inverted trof. The main focus will shift toward the inverted trof overnight into Sunday as some good llvl convergence and some mid leveling forcing will generate a period of light snow across the wrn and nnw areas by Sunday morning. The latest runs of the HRRR/NAM, RAP and even the GFS support this setup. Most of the forcing and weak advection associated w/the ocean low remains well offshore. So, just a grazing of some light snow by early Sunday morning. Confidence has increased to raise pops to 60% across the w and n areas for early Sunday as the best forcing pushes across those area. Given the DGZ below 15k ft and decent moisture up through 700 mbs as shown by the soundings, snow ratio could be 20:1 or higher across the nrn 1/2 of the region. Despite low QPF( Area Forecast Discussion...UPDATED
National Weather Service Austin/San Antonio TX
836 PM CST Sat Feb 13 2021 .UPDATE... Doppler radar is showing a series of light freezing bands moving across the San Antonio areas and to the north and east. We have gotten a few reports of sleet as expected with temperatures in the lower 20s. This trend is expected to persist for the next several hours. Then a break in the precipitation is forecast early Sunday morning before an upper level pulse of energy pushes across central Texas and aid the chances for more freezing rain and sleet over the Hill County including the north part of Travis County. Went ahead and adjusted ice accumulation amounts up to one tenth of an inch across the Williamson and northern Travis Counties. It is a dangerous situation and going to get worst on Sunday. && .PREV DISCUSSION... /ISSUED 608 PM CST Sat Feb 13 2021/ AVIATION... /00Z TAFS/ Doppler radar is showing light echoes across the San Antonio airports and soon reaching the KAUS terminal. With temperatures below freezing, expect freezing rain over the area if precipitation does fall to the surface. An upper level disturbance moving across the Rio Grande will provide the lift for precipitation to get going this evening into Sunday morning. MVFR cigs are expected to prevail overnight into Sunday morning. Can`t rule out a few hours of IFR around 10Z to 15Z . Another upper level disturbance is forecast to push across the area on Sunday afternoon and evening and continuing through Monday. During this time frame, we are expecting freezing rain and sleet first and then changing over to snow and MVFR and IFR cigs. Strong winds from the north are expected with gusts up to 30 knots throughout the night Sunday into Monday. PREV DISCUSSION... /ISSUED 233 PM CST Sat Feb 13 2021/ SHORT TERM (Tonight through Sunday Night)... The area of drizzle from earlier today has mostly come to an end across the area. The freezing line is currently located from a line from just north of Del Rio to Uvalde to Kenedy. Not expecting much more in the way of warming is anticipated across the area with the freezing line staying fairly constant. Some of the hi-res model guidance is progging another round of light drizzle or very light rain to develop around 6-7 PM this evening and impact portions of the I35 corridor through midnight or so before mostly ending with some patchy activity likely continuing through the night. The ice accumulation from the evening will be light, but as we have seen this morning, it will take just trace amounts to cause additional problems on the roadways this evening. Residents are urged to continue to remain off the roadways if at all possible. Temperatures will drop several degrees tonight with cold air advection continuing and the loss of the indirect heat from the sun. For tomorrow, most locations along and north of I10 will continue to remain below freezing with the remainder of the CWA perhaps warming into the middle 30s. A large trough axis will move into the Southern Plains by the early evening hours tomorrow and will send a very strong polar front into the region. Ahead of the front, models remain in good agreement that light rain/freezing rain/sleet and possible snow will develop in the mid to late afternoon across much of the area. This will be just the initial setup for the main event with the main forcing arriving overnight with a possible intense snow band moving through the area. The initial round of icing will stick immediately to all surfaces and the snow will likely be on top of that creating very hazardous traveling conditions tomorrow night. The deterministic runs of the ECMWF/GFS/Canadian remain consistent with 3-5 inches of snow over a large area of the CWA with some decent ice accumulations in the southeastern CWA. These totals may be overdone slightly but very cold air temperatures could lead to better rain to snow ratios. The NAM and some of the other high-res models remain dry outliers with much lower snow totals. However, the extended range of the HRRR shows similar totals to the global models. While there is some hesitance because of the NAM, one would think the setup of a long-wave trough and strong forcing would tend to support the global models being more accurate. In additional there is some signal of some frontogentical forcing that may lead to banding issues for somewhere in our CWA. This is especially true in the 18z HRRR. Our official forecast will for snow will show 3-4 inches with isolated higher amounts north of a Kerrville to Austin line and 2-3 inches north of a Rocksprings to Boerne to LaGrange Line. Less than 2 inches is expected for the remainder of the area. For ice, greater than a tenth of an inch is possible along and east of the I35/37 corridor. Have upgraded the watch to a warning for the remainder of the CWA except for Maverick and Dimmit County where an advisory is in effect with less accumulations expected there. In addition to the wintry precip concerns, temperatures behind the polar front will drop rapidly from already cold values. By Monday morning temperatures will be in the single digits in the Hill Country and in the teens for much of the remainder of the area. With strong north winds, wind chill values will be below 0 for much of the area. Any motorists that may become stranded, should be prepared for prolonged exposure in these conditions with hypothermia likely. Again, stay off the roadways if at all possible!! LONG TERM (Monday through Saturday)... Precipitation will end from west to east across the area Monday morning with a cold day expected. Highs Monday will top out in the teens and 20s for most of the area. Lows Tuesday night will likely be the coldest weather this area has seen since 1989! Lows will range from 3-9 degrees for locations north of Interstate 10 with teens across the other locations. Wind chills will be as low as -4 to 10 degrees. With the prolonged cold conditions, pipes will become an issue. Protect them as best as possible as bursts are almost all but guaranteed. A brief drying trend is expected Tuesday night, but our next system arrives Tuesday night. Models are in fairly good agreement that this will likely be mostly freezing rain with some possible sleet mixing in across the Hill Country. With 850 temps warming rapidly with the low-level lift ahead of a trough, surface temperatures will hopefully warm as well. Global models show all but the northern counties above freezing by noon and will show freezing rain transitioning to rain for the southern counties. However, a cold front with some wrap around moisture could transition the precipitation back to a snow/sleet mixture Wednesday night. Will try to show all of this in the grids, but confidence in the mid-week forecast remains low as we are still 5 days out. Regardless, this historical cold weather outbreak that will be talked about for years to come looks to give us another round of frozen precipitation mid-week. The good news is drier and slightly warmer weather look to return on Friday and Saturday. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 27 29 13 21 6 / 30 60 90 20 0 Austin Bergstrom Intl Airport 27 30 12 22 5 / 30 60 90 20 0 New Braunfels Muni Airport 28 31 14 24 7 / 30 60 90 10 0 Burnet Muni Airport 23 25 8 18 5 / 30 60 90 10 0 Del Rio Intl Airport 31 37 16 29 17 / 10 30 80 - 0 Georgetown Muni Airport 25 27 9 19 3 / 30 60 90 20 0 Hondo Muni Airport 29 34 14 27 10 / 20 40 80 - 0 San Marcos Muni Airport 27 31 13 22 6 / 30 60 90 20 0 La Grange - Fayette Regional 30 34 15 22 9 / 30 50 90 30 0 San Antonio Intl Airport 29 32 15 24 10 / 30 50 90 10 0 Stinson Muni Airport 29 33 16 26 11 / 30 50 90 10 0 && .EWX WATCHES/WARNINGS/ADVISORIES... Winter Storm Warning until noon CST Monday for Atascosa-Bandera- Bastrop-Bexar-Blanco-Burnet-Caldwell-Comal-De Witt-Edwards-Fayette- Frio-Gillespie-Gonzales-Guadalupe-Hays-Karnes-Kendall-Kerr-Kinney- Lavaca-Lee-Llano-Medina-Real-Travis-Uvalde-Val Verde-Williamson- Wilson-Zavala. Winter Weather Advisory from 3 PM Sunday to noon CST Monday for Dimmit-Maverick. && $$ Short-Term/Aviation...17 Long-Term...04
Area Forecast Discussion
National Weather Service Grand Rapids MI
1058 PM EST Sat Feb 13 2021 LATEST UPDATE... Update .SYNOPSIS... Issued at 300 PM EST Sat Feb 13 2021 - Lingering showers along lakeshore tonight - Snow showers and bitter cold for Monday Morning Commute - Snow with coldest temperatures this winter through mid week && .UPDATE... Issued at 1058 PM EST Sat Feb 13 2021 Main concerns tonight are lake effect snows towards the Lake Michigan shoreline and the threat of patchy dense fog across the area. As for the lake effect snow, a bit concerned that we may see higher totals than forecast along the shoreline tonight. HRRR surface wind fields show that convergence along the shoreline may hold in place through the night and focus accumulations there. This has already been going on this evening and it may continue overnight. We have likely pops in the forecast with accumulations of an inch or two. We will be keeping an eye on radar imagery through the night. Another concern is patchy dense fog that has been ephemeral here at the GRR airport this evening. An hour or so ago, we dropped to 1/4 of a mile in dense fog. It has since lifted considerably. The fog is radiational in nature due to some melting that went on during the mid afternoon hours. That melting added moisture to the boundary layer and when combined with clearing and a temperature drop this evening led to almost instant fog in spots. We still have some 1/4 mile fog being reported across the area. The expansion of stratocumulus off of the lake and an increase in winds in the lowest couple thousand feet should lead to the fog becoming very patchy or even eliminated. We will be watching this threat tonight as well. && .DISCUSSION...(This evening through next Saturday) Issued at 300 PM EST Sat Feb 13 2021 -- Lingering showers along lakeshore tonight -- Widespread light snow continues across the upper mid west with locally heavy bands embedded. The heaviest line is moving through the Ludington region and will continue to slowly drift eastward as the afternoon progresses. So far one to two inches have fallen out of these showers with another one to 3, mainly along the lakeshore, expected. These showers are stemming from moisture on the southern end of a large quasi stationary upper level low north of Minnesota and is slowly moving eastward. A short wave trough emanating from this low will cycle northward and, along with an upper level jet, will take the corresponding moisture with it. This will allow snow showers to end in most places as high pressure builds into the wake. Snow showers along the lakeshore will continue. Copious amounts of mid level clouds will signal that cloudiness will continue through Sunday. -- Snow showers and bitter cold for Monday Morning Commute -- The break in snow will be short lived as another wave of snow will move through Sunday night into Monday morning. The aforementioned upper level low will tilt positively and be caught up by an elongated long wave trough. This interaction will along for a moisture flow and boundary to form through the midwest and bring snow showers to Indiana, Ohio and the southern end of Michigan. This will also be bringing bitterly cold air. This cold air correlates with -15 at 850mb which will bring lows of -2 to 6 F Monday morning. Widespread subzero wind chills are expected Monday morning with temps continue to be low through late in the work week. -- Snow with coldest temperatures this winter through mid week -- Another round of snow showers will continue Tuesday as the cold and snow weather continues. The heaviest snow is expected in the southeastern counties. Have held off on an advisory for now but if the signal moves northward or an intensification of the bands then one may be needed. However, given latest guidance the heaviest snow will be to the southeast. The cold air will continue through mid week with wind chills near criteria though currently they are just above. So that will need to be monitored. The cold air mass will lift to the northeast through the latter half of the week with more moderate temperatures possible late in the week. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 724 PM EST Sat Feb 13 2021 Tried to write the 00Z TAFs a bit more optimistic than what model guidance would suggest. Model guidance would indicate we should continue to have widespread MVFR and even IFR conditions the next 24 hours. Indications are that may not be the case as the system related precipitation is peeling off to the east and dissipating rapidly as of 00z. A look at aviation conditions as compared to an hour or two ago shows a fairly big improvement from widespread IFR up to MVFR. My feeling is that this trend will continue and we will go VFR from KGRR and KAZO to the east overnight. The pattern overnight and into Sunday is one of northwest flow lake induced clouds, which tries to turn more northerly towards Sunday evening. Also of note is the flow is light, generally less than 20 knots below 10,000ft. Lake effect clouds/snow in a light wind regime such as this normally features clouds trending towards the shoreline of Lake Michigan with clearing inland. So, we have gone optimistic inland (VFR) as we head through the evening. The 06z set of TAFs may be even more optimistic as lake effect towards Lake Michigan looks light. Winds will generally be light northwest through the period at 5-15 knots. && .MARINE... Issued at 1115 AM EST Sat Feb 13 2021 Small craft advisory criteria will be met tonight through tomorrow. Winds will shift to the northwest and increase. With ice covering the nearshore south of Grand Haven the value in issuing a headline is very low. Waves will be 4 to 6 feet north of Grand Haven and have issued an advisory. Freezing spray should increase tonight and Sunday, further coating the piers and lighthouses that are near open water. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...Small Craft Advisory until 7 PM EST Sunday for LMZ847>849. && $$ UPDATE...Duke SYNOPSIS...Ceru DISCUSSION...Ceru AVIATION...Duke MARINE...Ceru
Area Forecast Discussion
National Weather Service Gray ME
1032 PM EST Sat Feb 13 2021 .SYNOPSIS... A weak weather system brings the chance for some light snow or even patchy freezing drizzle Sunday morning. That will begin what should be an active weather week...with another round of light snow possible late Monday before a more substantial system brings snow and possibly some mixed precipitation to the region Tuesday. Another storm system is expected by the end of the week. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... 1030 PM Update...We continue to be dry this evening as we`re in between two areas of relatively weak forcing for ascent. Much of the night will be cloudy and dry with light winds. However, it`s possible that we`ll see some very light snow or flurries Sunday morning, with perhaps a few pockets of freezing drizzle. Not big changes to the forecast at this hour except for adjust temperatures a little bit. 630 PM Update...Little change to the going forecast other than to lower PoPs a bit for tonight - more in line with the latest HRRR guidance. Otherwise, just a few minor adjustments to temperatures. Previously... Impacts: Very light snow possible early Sunday morning, especially for NH and far western portions of western ME. Could make for slick travel. It`s quiet out there at this hour as mid and high clouds continue to stream overhead. Conditions should remain quiet through the late evening as well with clouds thickening and lowering as we head into tonight. Low pressure will slide off the mid-Atlantic coast tonight and a shortwave will move across New England. These two features will provide just enough forcing to generate a coating of snow before sunrise, primarily in NH and portions of far western ME. Even a few tenths will be enough to make roads slick for travelers on Sunday morning, especially with temperatures in the single digits and teens and road temperatures expected to be near or below freezing. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/... Impacts: Very light snow continues into Sunday morning with slick roads expected. Will continue assessing the potential for freezing drizzle for late Sunday morning as the precipitation comes to an end. With the low pressure continuing to move east and the shortwave pulling off to the north, forcing for ascent will quickly wane late Sunday morning, but probably not before most of the region picks up another tenth or two of snowfall. Do want to mention the possibility of light freezing drizzle Sunday morning as well. A look at forecast soundings around the area shows a nearly saturated layer from the surface to between 700 and 800 mb, some weak upward vertical motion and a deep dry layer collocated with the DGZ above the saturated layer and inversion. Not confident enough to put it in the grids with this package as temperatures in the lower levels may still be just cold enough for snow to develop instead. Even light freezing drizzle could be impactful, especially on already lightly snow-covered roads, so will mention in the HWO now and let subsequent shifts continue to assess. Highs will range from the mid 20s north to the lower 30s south; some locations in southern NH may make a push to get above freezing. Any precipitation should be coming to an end by early afternoon, but clouds will persist over southern and western areas into the evening. Quiet conditions return Sunday night with partly to mostly cloudy skies and lows ranging from the positive single digits north to the upper teens south. && .LONG TERM /MONDAY THROUGH SATURDAY/... An active week is in store as we deal with two winter systems, one on Tuesday and another at the end of the week. This is mainly the result of strong ridging over the Atlantic colliding with remnant polar vortex cross Ontario and srn Quebec. This will great strong temp/gradient across New England, so any waves that pass thru at 500 MB will be able to produce strong thermal advection. An temps fluctuate a bit around these systems, although not too badly as low levels will mostly stay cooler, thanks to NW-NE flow. Monday could start off with some sun, but clouds will thicken as we see some weak mid-level FG and tightening of the temp gradient. Could see some SHSN or maybe some very light snow associated with this FG, but mostly looks light, and may have a tough time since it will likely falling from somewhere between 5-10k ft, and initially airmass near the sfc will be dry. Highs Monday will be in the mid 20s to low 30s. May see a little break before we start to see precip moving in from the coastal low, likely after midnight and closer to daybreak in central ME. P-type is one of the bigger questions, although it will all start as snow. Models have not instilled a lot of confidence regarding progression poleward of the warmer mid level, and the 12Z Euro has come in cooler, which would mean more snow. Still I think there`s a possibility of seeing some PL or FZRA mixing in on Tuesday across SE NH and the ME coast, but not confident on how much or how that will affect snow amts. Overall QPF still coming around 0.75." I don`t think anywhere will rise above freezing but some coastal areas and the MHT-ASH corridor could see temps of 30-32, with 20s elsewhere. Precip should wind down late afternoon to early evening, with colder air moving in and upslope SHSN Tue night. The 500 MB trough tamps down the ridging on Wed, and some cooler air will work in with high mainly in the 20s on Wed. Expect mountain clouds and mainly sunny skies S of the mtns. The next system approaches Thu and should impact the area Thu night into Friday. This wave is a little weaker, with not as cold air to the N than the Tuesday system, and should see the ridge, and the surge of warm air aloft to have a snow to mix to rain event in the srn areas. Of course this is day 6, so confidence is low attm. && .AVIATION /04Z SUNDAY THROUGH THURSDAY/... Short Term...VFR conditions expected at all terminals through this evening. Ceilings will begin to lower after midnight but should stay above MVFR levels until around 12Z. Chances for snow begin to ramp up between 06Z and 12Z, but at this time, the only places where confidence was high enough for me to put snow in the TAF was at HIE and LEB. Do think that MHT/CON/PSM/PWM have decent chances as well, but could also be FZDZ...and even if it does snow, it will likely be brief and very light or could just be flurries. Will let future TAF packages assess the possibility at those sites with additional data this evening. Long Term...Monday could start as mainly VFR, but should see MVFR cigs become predominant during the afternoon, with possible IFR vis in spotty -SN. Tuesday will likely be stuck in IFR or lower all day in mostly SN, although there is some potential for PL or FZRA at KMHT/KPSM/KPWM/KCON. Tue evening will start to see improvement with VFR returning by late Tue night. VFR is expected Wed-Thu. && .MARINE... Short Term...Seas will remain rather calm through the short term. Winds will become more northeasterly tonight as low pressure passes to the southeast of the waters, gusting to 15-20 kt at times. Winds then turn more northerly late Sunday into Sunday night but remain well below SCA criteria. Long Term...SCA will likely be needed late Mon night into Wed, and initially E flow develops ahead of coastal storm, then shifts to NW behind the storm Tue night and Wed. && .CLIMATE... We are in the midst of what is likely to be the longest continuous freeze of the season. While the most intense of the cold air is likely to remain well to our west, the sustained period of subfreezing temperatures is likely to be the longest observed in this region since the Great New Year`s Cold Snap of 2017-2018. The first subfreezing day in our current stretch was on February 7 and is ongoing. Current forecasts project subfreezing temperatures will last deep into next week, likely approaching or exceeding 10 straight days at or below freezing. At Portland, a stretch of 7+ days at or below 32 has occurred 118 times in 80 years of records. This averages out to about 3 times every two years. The last stretch of 7+ days at 32 or colder occurred from December 15 thru 21, 2020. This stretch of subfreezing temperatures is likely to be the longest since the stretch of 15 days observed from December 25, 2017 thru January 8, 2018. The longest stretch of subfreezing days was 23 days and occurred twice, from January 25 thru February 16, 2007 and from December 8 thru December 30, 1989. Temperature records at Portland began in 1940. At Concord, a stretch of 7+ days at or below 32 has occurred 228 times in 133 years of records. This averages out to about 5 times every 3 years. The last stretch of 7+ days at 32 or colder occurred from January 28 thru February 3, 2019. This stretch of subfreezing temperatures is likely to be the longest since the stretch of 15 days observed from December 25, 2017 thru January 8, 2018. The longest stretch of subfreezing days was 37 days from December 22, 1976 thru January 27, 1977. Temperature records at Concord began in 1868. At Augusta, a stretch of 7+ days at or below 32 has occurred 173 times in 73 years of records. This averages out to more than twice per year. The last stretch of 7+ days at 32 or colder occurred from December 15 thru 21, 2020. This stretch of subfreezing temperatures is expected to be the longest since the stretch of 15 days observed from December 25, 2017 thru January 8, 2018. The longest stretch of subfreezing days was 33 days and occurred twice, from January 20 thru February 21, 2015 and from January 4 thru February 5, 1955. Temperature records at Augusta began in 1948. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$ NEAR TERM...Ekster/Watson SHORT TERM...Watson LONG TERM...Cempa
Area Forecast Discussion
National Weather Service Jacksonville FL
903 PM EST Sat Feb 13 2021 .UPDATE... A quasi-stationary frontal boundary is draped across northeast Florida just south of I-10 and extends northeastward into the Atlantic waters while a weak low is southeast of Apalachicola, FL. The moist airmass over the area has mainly stabilized limiting thunderstorm development over our area. Waves of showers will continue to move northeastward up from the Gulf of Mexico and spread across southeast Georgia and northeast Florida. Have removed thunderstorm chances from our area except for our north- central FL zones which remain south of the boundary. Current thunderstorms off the coast of Tampa could move into our north- central Florida zones by midnight. A large temperature gradient continues with lows tonight ranging from the low 40s in southeast Georgia to the mid 60s in north-central Florida. && .PREV DISCUSSION [642 PM EST]... .NEAR TERM [Through Tonight]... 18Z regional surface analysis places a weak low just SW of Apalachicola, FL, with a quasi-stationary frontal boundary extending ENEward from it toward Fernandina Beach, FL and then curving NEward off into the Atlantic waters. Aloft, mostly SW flow is in place over the southeastern CONUS with weak upper level impulses periodically ejecting northeastward over us, bringing upper level support for occasionally stronger storms. Model guidance continues to be in general agreement that the front will lift slowly northward as the Gulf low moves eastward through tonight. This will keep most of NE FL in the warm sector, with a gradual increase in instability this afternoon as clouds from this morning continue to scatter out while SE GA stays in the cool, more stable airmass. Decent bulk shear near 40 kt is still in place. Clouds over N-central FL have just begun to scatter out over the last couple hours, leading to increasing instability in that region. HRRR is showing our next band moving into that area from the SW in the next few hours, which is still seeming plausible and could still bring a few heavier showers and pose a threat for isolated damaging wind gusts. Instability will wane again as we head into the overnight period, but we still expect to see a few rounds of showers along/near the frontal boundary overnight. A large temperature gradient is in place on either side of that stalled frontal boundary, with temperatures in the mid-upper 40s in inland SE GA and in the upper 70s in N-central FL. Overnight, temperatures won`t cool much under dense cloud cover, staying in the mid 40s in SE GA and dipping into the mid 60s in N-central FL. .SHORT TERM [Sunday Through Monday Night]... At the low levels on Sunday, we`ll remain sandwiched between an inverted coastal trough off SE GA`s Atlantic coastline and an area of surface low pressure in the NErn Gulf Waters south of Apalachicola, FL. A quasi-stationary frontal boundary will be stretching between these two features, draped across NE FL roughly along the I-10 corridor. At the upper levels, waves of energy continue to parade northeastward over the front, enhancing upper level divergence and leading to elevated instability along and S of the boundary. Model guidance shows the SW-NE oriented frontal boundary will pivot Sunday and become more SSW-NNE oriented,then lift northeastward Sunday night as a stronger +PV anomaly pulls that Gulf low away, then swing eastward late Monday night. The boundary is expected to remain in place near the FL-GA border Monday, but with less energy/enhancements aloft, not as much widespread rain is forecast. In terms of dynamics, we`ll have the greatest instability in the warm sector along and S of the I-10 corridor, with MLCAPE peaking around 400-600 J/kg on Sunday afternoon and 700-900 J/kg on Monday afternoon. Adequate deep layer shear of 40-60 kts will be in place across the region through the period. Juicy PWATs of 1.5-2" across our area on Sunday will mean plenty of moisture is on tap for storms through the day, but values will taper down to around 1.25-1.75" Monday after some of the energy aloft gets pulled away. The low level jet will increase to around 40-45 kts along and S of the boundary Sunday, then wane overnight only to surge to around 50 kts across SE GA on Monday afternoon/evening. Low level SRH right along the frontal boundary will be around 100-150 m2/s2 through the period means a brief tornado or two can`t be rule out for storms along or very near to the boundary, especially if storm-scale pressure/vorticity perturbations occur. Overall, the waves of energy will lead to on and off rounds of showers with embedded thunderstorms capable of producing heavy rain and strong to severe damaging wind gusts. As for temperatures, we`ll continue to see that strong temperature gradient across the area on Sunday with highs in the low 50s near the Altamaha River and highs near 80 around the Ocala area. Likewise, Sunday night temps will range from the upper 40s to mid 60s across the region. That gradient will shrink a little bit on Monday, with highs in the mid 60s near the Altamaha River and highs in the low 80s near Ocala and Flagler Beach. Lows Monday night will fall to the mid-upper 50s in SE GA and the upper Suwannee Valley, low-mid 60s in NE FL. .LONG TERM [Tuesday Through Saturday]... On Tuesday, the stalled frontal boundary should finally push eastward, giving the area a little break from all this rainfall. This break will be brief, however, with a much more potent +PV anomaly digging into the Srn Plains Wednesday, bringing that boundary back as a warm front by Wednesday night. A very energetic frontal system will then find its way across the SErn CONUS through the end of the work week. Some model disagreements on the exact timing for when this one will reach us at this point, but current thinking is Thursday night, with a much colder drier air mass pushing in Friday-Saturday. In fact, SE GA may even see a frost on Friday night/Saturday morning as this colder air mass moves in. .AVIATION... [Through 00Z Monday] Widespread IFR/LIFR ceilings persist over southeast Georgia and have returned to some of the northeast Florida sites. IFR/LIFR ceilings and visibilities will affect all sites overnight and linger into tomorrow morning. Showers continue to move northeastward from the Gulf of Mexico overnight affecting the TAF sites. Showers continue tomorrow with chances for thunderstorms for the northeast Florida sites. .MARINE... A stalled frontal boundary is draped across our coastal waters from near Fernandina beach northeastward. Multiple rounds of heavy rainfall and isolated thunderstorms are expected over the next several days for our coastal waters as this front shifts back and forth. Storms will be capable of producing damaging wind gusts. When it`s not raining, sea fog will develop as winds will remain relatively light, with the most dense fog developing in the overnight hours and hanging in through the late morning as we`ve seen the last several days. Rip Currents: NE FL and SE GA- Moderate Risk through Sunday .FIRE WEATHER... A wet pattern will remain in place through Monday night, with a brief break in the rain on Tuesday, then 20-30% chances for showers return again by Wednesday. A strong cold front is expected to move in towards the end of the work week. Transport and 20 ft winds may be elevated in north-central FL as a series of low pressure systems move through the area, but with such a wet pattern in place, no red flag conditions will develop. Along and north of the front, winds will be so light that daytime dispersions will be around 20 or less this afternoon and again on Sunday. Multiple rounds of heavy rain and isolated thunderstorms producing damaging winds will continue throughout most of the period. Fog is possible for the next few mornings. .HYDROLOGY... A flood watch is in effect for inland SE GA and the upper Suwannee Valley through Sunday. In this region, 2-4" of rainfall is forecast to occur over the 2 day period, with isolated higher totals anticipated which could lead to localized flooding. Further southeast, widespread rainfall totals should be around 1-2", but again, localized higher totals are anticipated which could lead to localized flooding. As for our rivers, minor flooding is already occurring at points along the Santa Fe and Little Satilla Rivers and additional rainfall this weekend is anticipated to further aggravate these basins as well as bring portions of the Altamaha River into minor flood stage early next week. && .PRELIMINARY POINT TEMPS/POPS... AMG 43 53 50 68 55 / 70 90 30 40 70 SSI 49 60 53 66 59 / 90 80 40 30 50 JAX 53 65 57 74 62 / 80 80 30 40 50 SGJ 57 70 60 76 63 / 60 60 30 40 40 GNV 60 73 61 78 62 / 80 80 30 40 60 OCF 63 77 63 81 63 / 50 80 20 40 60 && .JAX WATCHES/WARNINGS/ADVISORIES... FL...Flood Watch through Sunday evening for Hamilton-Suwannee. GA...Flood Watch through Sunday evening for Appling-Atkinson-Bacon- Clinch-Coffee-Echols-Jeff Davis-Northern Ware. AM...None. &&
Area Forecast Discussion
National Weather Service Key West FL
1045 PM EST Sat Feb 13 2021 .DISCUSSION... The 00z KEY sounding showed deep southerly flow and a Precipitable Water (PW) value well in excess of the 90th percentile for this time of year. Water vapor imagery showed a nice shortwave lifting northeast from the Yucatan into the southeast Gulf late this afternoon. It continues to ride northeast this evening, to the east of the strong but stationary front over the Central Gulf. The upper disturbance is contributing to the unsettled convective weather to our west and northwest this evening. Over our waters, have recently seen the first lightning of the evening just northeast of Dry Tortugas. The strongest convection should remain out over the deeper Gulf waters during the next few hours before lifting up toward Southwest Florida even later tonight. After that, may see a few stray showers develop over the Straits and lift north toward the Keys. && .MARINE... Satan Shoal and Pulley Ridge buoys are respectively reporting 3- and 4-foot seas this evening. Isolated thunder may be a concern for a few more hours over the deep southeast Gulf waters. Fast movement to the north could mean 30-knot gust potential. Otherwise, southerly winds across the open Straits have likely freshened to the point this evening for adding cautionary headlines for the overnight hours. These winds will decrease on Sunday morning. From synopsis...A front stalled across the Gulf of Mexico will dissipate Sunday and Sunday night. A new frontal zone will merge with the old frontal boundary Monday and Monday night, then stall over the extreme southeastern Gulf of Mexico on Tuesday. A potent low pressure system will develop over the western Gulf of Mexico on Wednesday, then race to the northeast to east Wednesday night and Thursday. Southeast breezes will freshen Wednesday and Wednesday night in advance of the deepening surface low in the Gulf of Mexico. Our confidence is increasing for a cold front to be nearing the Florida Keys late Thursday night or Friday morning. && .AVIATION... Recently added VCSH to the Marathon terminal due to a nearby shower on radar, as well as recent HRRR solutions which show some showers passing nearby overnight. EYW could miss out altogether, despite being closer to the deeper convection lifting north through the southeast Gulf waters. Deep southerly flow and somewhat deeper moisture will lend itself to rounds of mid-level clouds. All in all, VFR conditions will prevail for the next 24 hours. && .KEY WATCHES/WARNINGS/ADVISORIES... FL...None. GM...None. && $$ Public/Marine/Fire...Haner Aviation/Nowcasts....Haner Data Acquisition.....11 Visit us on the web at Follow us on Facebook and Twitter at:
...Updated Aviation Forecast Discussion...

.DISCUSSION... Issued at 250 PM CST Sat Feb 13 2021 The main forecast concerns are snow amounts in southeast NE tonight into Sunday and the very cold weather with wind chills of 20 below zero to 40 below zero tonight into Tuesday. We expect the coldest wind chills to be after midnight Sunday night into Monday morning, then again after midnight Monday night into Tuesday morning. Surface analysis this afternoon showed high pressure extending from southern Canada all the way down into Texas. There were variable amounts of cloud cover, and temperatures ranged mostly from around zero to 5 above. The 500 mb pattern today features a low with heights around 505 decameters over southwest Ontario and a trough from British Columbia down to Arizona. Expect that clouds will thicken over the area tonight as lift moves in from the west. A band of snow should develop from the west over western and southern NE tonight into Sunday morning, then fade out with time in the afternoon. Added a few counties and adjusted the end time of the Winter Weather Advisory for southeast NE to 6 pm Sunday. Also started the Wind Chill Advisory a bit earlier this evening in our northern and eastern counties. Felt amounts that snow amounts could reach upwards of 3 inches in the advisory. Inched the area with possible measurable snow northward a bit to Columbus, Fremont, Omaha/Council Bluffs closer to the northern edge shown by using a blend of 12Z runs of GFS, RAP and ECMWF. Amounts on the northern edge should be an inch or less. Look for lows tonight from about -5 to -12 or so, warmest south and coldest north/northeast parts of the forecast area. On Sunday, it now looks like the highest potential for measurable snow is in the morning. For now let the advisory go longer, but we may be able to end that earlier than 6 pm if trends continue. For highs, well we currently do not expect anyone to get above zero. Wind chill watch for Sunday night into Tuesday morning is still on track and will probably be converted to a wind chill warning at some point, for the times we expect the worst conditions. Very cold temperatures are forecast for Sunday night and again Monday night, so any wind at all will create a strong chill factor. Some model guidance suggests a weak system moving through the region for Tuesday afternoon into Tuesday night. For now will keep close to the POPs suggested by NBM and keep it dry, but we may need changes to that period as we get closer. Cold high pressure will slowly move off to the east later in the week, with a slow moderation of temperatures. The pattern will be wet or snowy to our south and east. Highs could reach the lower 20s in our western and southern counties by Thursday, and we should all see highs in the 20s to around 30 in eastern NE and southwest IA by Friday. We should rise above freezing Saturday, if the current forecast pattern holds. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 623 PM CST Sat Feb 13 2021 A few flurries have shown up in the area. Opted to include potential MVFR conditions at OMA as TQE had some reduced conditions with these flurries. Expect these flurries to die out with sunset. After 06z, some snow showers will move in, mainly affecting LNK and to much lesser extend OMA. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...Wind Chill Watch from late Sunday night through Tuesday morning for NEZ011-012-015>018-030>034-042>045-050>053-065>068-078- 088>093. Wind Chill Advisory until midnight CST Sunday night for NEZ011- 012-015>018-031>034-045. Winter Weather Advisory from midnight tonight to 6 PM CST Sunday for NEZ065-066-068-078-088>093. Wind Chill Advisory from midnight tonight to midnight CST Sunday night for NEZ030-042>044-050>053-065>068-078-088>093. IA...Wind Chill Watch from late Sunday night through Tuesday morning for IAZ043-055-056-069-079-080-090-091. Wind Chill Advisory until midnight CST Sunday night for IAZ043- 055-056-069-079-080-090-091. && $$ DISCUSSION...Miller AVIATION...Pearson
Area Forecast Discussion
National Weather Service Phoenix AZ
420 PM MST Sat Feb 13 2021 .UPDATE...Updated Aviation Discussion. && .SYNOPSIS... One weather system this weekend will bring showers mainly over higher terrain areas north and east of Phoenix, while locally windy conditions should provide the greatest impact this evening across the lower deserts. The disturbance for Tuesday will again mainly bring breezy to locally windy conditions with light precipitation over higher terrain areas. Temperatures through much of next week will be a few degrees below normal, before a warming trend looks likely by next weekend. && .DISCUSSION Latest streamline analysis depicts a well-defined shortwave trough across southern Utah and northern Arizona. To its west, an elongated swath of vorticity extends from central Arizona well upstream into the Great Basin. Consequently, strong vorticity and jet-forced ascent is resulting in thickening clouds across north- central Arizona. Further west across southeastern California, strong winds have persisted near Twenty-Nine Palms, which has produced areas of blowing dust (now evident on GOES-17) and reduced visibilities. Latest suite of model guidance continues to indicate winds will gradually strengthen across the lower deserts this afternoon, including the Phoenix area. Although gusts to 30 mph are most likely, latest HRRR and HREF ensemble max suggest an isolated gust to 40 mph cannot be ruled out. Consensus among the hi-res CAMs is that this system will pass through with little chance for rain. However, a handful of members including the NAM Nest do indicate a brief shower will be possible in the Valley this evening between 8 and 10 pm. Best chance for rain will be across the higher terrain north and east of Phoenix, though even the highest amounts will be less than a quarter of an inch, except across the highest peaks where lift will be maximized. Bigger impact will be the wind, though speeds will generally subside overnight behind the trough axis. Cooler conditions are anticipated Sunday in the wake of the trough. NBM continues to trend cooler with widespread high temperatures in the mid 60s across the lower deserts. Meanwhile, lingering moisture across Gila County will manage to squeeze out a few snow showers above 4500 ft, though accumulations are not expected. Further west, the pressure gradient will remain tight enough to support breezy conditions, particularly across portions of southeastern California and southwestern Arizona. && .PREVIOUS DISCUSSION... The deep trough situated across the central part of the country will keep heights aloft over our region fairly stable through the first half of next week, likely keeping temperatures near normal through at least Wednesday. Yet another progressive shortwave trough still looks to pass through our region on Tuesday, but it looks to be rather weak and again may only result in mostly high terrain showers. Gusty winds will likely again be the main impact with this early next week system with gusts potentially reaching near advisory level across our western deserts. An even drier air mass seems to settle in for the middle of next week, potentially helping to bring below normal overnight lows for a night or two later next week. However, even the coldest lower desert spots might struggle to get into the 30s given the air mass does not look very cold. Ensemble cluster analysis then points toward a high amplitude ridge well off the West Coast likely nudging more into our region at some point by next weekend. If this scenario were to play out, high temperatures over the lower deserts would likely be pushing 80 degrees by next Saturday. && .AVIATION...Updated at 2315Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Gusty westerly winds of 15-20 kts with gusts near 30 kts will persist for 1-2 additional hours and then weaken. Speeds of near 10 kts will continue through much of the day tomorrow and remain generally westerly or southwesterly. A few showers will be possible around the terminals, with the best chance towards KSDL and KDVT between 2 and 4Z this evening. SCT-BKN coverage will develop near 7-8 kft, and potentially briefly drop lower under any showers. A second cloud deck near 10 kft will thin out overnight with just high clouds tomorrow. Southeast California/Southwest Arizona including KIPL and KBLH: Strong westerly winds are gusting 20-30 kts at KBLH and 30-40 kts at KIPL. These strong winds will persist overnight and through tomorrow at KBLH but will gradually become more northerly. At KIPL winds will also gradually become northerly, but speeds will drop to 10-15 kts. A few areas of blowing dust may reduce visibility at times this evening, potentially down to a few miles briefly. Otherwise, high clouds will continue through the forecast period. && .FIRE WEATHER... Monday through Friday: Fairly dry conditions are anticipated through much if not all of the week with one weather system likely moving through on Tuesday, but mainly bringing wetting rain chances across the high terrain. Winds will also pick up again on Tuesday, lasting into Wednesday with gusts likely approaching 35 mph over the western deserts. Much lighter winds are expected for late in the period. Minimum relative humidities through Tuesday will mostly fall between 15-25% over the deserts and 25-35% across the high terrain, while beginning Wednesday falling mostly into the 10-15% range. && .SPOTTER INFORMATION STATEMENT... Spotters should follow standard reporting procedures. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...Blowing Dust Advisory until 10 PM MST this evening for AZZ530- 533. CA...Wind Advisory until 10 PM PST this evening for CAZ560>562-566- 570. Blowing Dust Advisory until 9 PM PST this evening for CAZ561- 568>570. Wind Advisory until 8 PM PST this evening for CAZ567. && $$ DISCUSSION...Hirsch PREVIOUS DISCUSSION...Hirsch AVIATION...Hodges FIRE WEATHER...Kuhlman
Area Forecast Discussion
National Weather Service Shreveport LA
1001 PM CST Sat Feb 13 2021 .UPDATE... Lowered temps across the far north and loaded in NAM00Z winds. && .SHORT TERM... Mostly cloudy skies with a few breaks and already low 20s north of I-30. So we did lower lows down into upper teens there. Elsewhere, our air temps are in the mid to upper 20s north of I-20 and low to mid 30s south. The water vapor shows the lead short wave energy now over S TX and moving our way. Mosaic radar coverage is picking up a bit of an increase in coverage and surface reports in S TX show a quite varied mix in progress. We pushed back our initiation of precip from midnight to closer to 2 to 3 am for parts of E TX. The new NAM has very spotty coverage of a mix, so icy patches will become likely near daybreak and keeps more of the coverage in E TX. The HRRR is similar to the NAM to start, but goes area wide for the spotty coverage by mid morning. The soil temp 4 inches down is 40 now in Shreveport, so some melt water will soon be freezing as the heat is used up, but roads should be good over one more night. A few overpasses will bear the brunt of any icing overnight. The winds seemed a little light and we have loaded in the new NAM for the overnight hours. No changes to anything else at this time. /24/ && .PREV DISCUSSION... /issued 624 PM CST Sat Feb 13 2021/ AVIATION... For the ArkLaTex terminals MVFR/VFR for much of the overnight with a lead short wave to the big event early Monday on the way. This little lead disturbance is moving over S TX attm and will move ovhd early on Sun. MVFR with some reduction in vsby with light fog as sn and/or frz ra will spread over the region after daybreak. The initial snow falling from the middeck will become more of a freezing ra to dz event during the aftn as warm air advects over the arctic air in the lowest levels ahead of the big trough. Sfc winds keep N/NE this cycle with SW flow aloft. /24/ PREV DISCUSSION... /issued 318 PM CST Sat Feb 13 2021/ SHORT TERM.../Tonight through Sunday/ Cloud cover across portions of the Ark-La-Tex is thinner today, compared to yesterday, allowing more insolation to affect surfaces and boosting afternoon highs in certain areas. A trend that hasn`t changed as much is cold air advection from shallow northerly flow, which still helps keeps the diurnal curve flatter regardless of any extra sunshine. By tonight, cloud cover should thicken once again in advance of our first round of wintry precipitation, which is currently evident in a trough axis proceeding across West Texas, gradually entering East Texas overnight into early Sunday. Our Winter Storm Warning is set to begin at midnight tonight due to the onset of wintry precipitation occurring in the forms of light freezing rain and sleet first in Deep East Texas, with light sleet and snow showers approaching the Red River Valley. That band of a wintry mix quickly fans out across the entire Ark-La- Tex by Sunday, evolving into snow showers for zones north of the I- 30 corridor, a mixture of sleet and freezing rain between the I-30 and I-20 corridors, and mainly a chance of more freezing rain south of the I-20 corridor. In the wintry precipitation process, evaporative cooling both keeps most afternoon highs below the freezing mark and gradually enhances cooling aloft for the change over to solid precipitation throughout the day. Accumulations and accretions expected through the afternoon include a few tenths of an inch in snow/sleet, and a few hundredths of an inch in ice respectively, both producing travel hazards upon cold, and/or elevated surfaces. /16/ LONG TERM.../Sunday Night through Friday Night/ Very little change in thinking for this first big wave of winter wx, which will be getting underway at the start of the long-term. Deep srn stream trof axis to push into the Southern Plains/W TX, bringing additional lift and a very cold airmass swd Sunday night. Wintry mix of precip is likely at the onset of the precip Sunday night, as the airmass will still be shallow, transitioning to snow from nw to se as temps aloft cool into Monday. Significant travel impacts continue to be expected with this event, with snow amounts generally in the 2-6 inch range, with isold higher amounts possible, for all areas except N Central LA, and ice accums areawide around a tenth to a quarter of an inch for all but our nwrn areas. Winter Storm Warning remains in effect from late tonight through Monday evening. In addition, wind chills will be very cold Sunday night through Monday /below zero into the single digits/, so have also issued a Wind Chill Advisory from midnight Sunday night through Monday evening. Very cold air will continue to filter swd Monday night, as the trof axis and precip shift ewd. Model output has continued to trend colder, with single digits now encompassing our entire region. Temp trends through the remainder of the week continue to run below NBM output as deterministic model output has trended colder. It is unlikely for any portion of our region to get above freezing until Wednesday and/or Thursday, and these "warmer" areas will likely be confined to the ern and sern portions of the region. Swly flow aloft will continue as another trof axis moves into TX Tuesday night into early Wednesday. Isentropic lift associated with this trof will again bring another significant winter wx episode. The setup appears similar to the event earlier in the week, with initial onset of precip mixed in nature, transitioning to snow as the air aloft cools with the approach of the trof axis Wednesday night. Highest snow/sleet accums will set up across the nwrn half of the region, with the sern half seeing more in the way of ice accums, likely similar to the early-week event. There continue to be some differences in model timing, but precip looks to move e of the region by Thursday evening/night. We should see a warming trend take hold Friday and beyond, as nwly flow aloft finally clears our clouds and the sun returns. /12/ && .PRELIMINARY POINT TEMPS/POPS... SHV 27 29 19 22 / 30 40 80 70 MLU 24 27 20 21 / 10 40 60 90 DEQ 19 26 12 20 / 10 70 90 40 TXK 24 27 17 20 / 20 60 80 50 ELD 22 24 16 21 / 10 60 80 80 TYR 25 28 11 16 / 40 50 90 50 GGG 27 28 16 19 / 30 50 90 60 LFK 29 33 18 23 / 30 20 90 70 && .SHV WATCHES/WARNINGS/ADVISORIES... AR...Hard Freeze Warning from midnight Sunday night to 6 PM CST Monday for ARZ050-051-059>061-070>073. Winter Storm Warning until 6 PM CST Monday for ARZ050-051- 059>061-070>073. Wind Chill Advisory from midnight Sunday night to 6 PM CST Monday for ARZ050-051-059>061-070>073. LA...Hard Freeze Warning from midnight Sunday night to 6 PM CST Monday for LAZ001>006-010>014-017>022. Winter Storm Warning until 6 PM CST Monday for LAZ001>006- 010>014-017>022. Wind Chill Advisory from midnight Sunday night to 6 PM CST Monday for LAZ001>006-010>014-017>022. OK...Hard Freeze Warning from midnight Sunday night to 6 PM CST Monday for OKZ077. Winter Storm Warning until 6 PM CST Monday for OKZ077. Wind Chill Advisory from midnight Sunday night to 6 PM CST Monday for OKZ077. TX...Hard Freeze Warning from midnight Sunday night to 6 PM CST Monday for TXZ096-097-108>112-124>126-136>138-149>153- 165>167. Winter Storm Warning until 6 PM CST Monday for TXZ096-097- 108>112-124>126-136>138-149>153-165>167. Wind Chill Advisory from midnight Sunday night to 6 PM CST Monday for TXZ096-097-108>112-124>126-136>138-149>153- 165>167. && $$ 24/16/12
Area Forecast Discussion
National Weather Service Tulsa OK
1004 PM CST Sat Feb 13 2021 .DISCUSSION... Have updated snowfall amounts for tonight in areas to the northwest of I-44, as most recent runs of the HRRR and HRW suite have continued to focus the initial frontogenetic band of snow in the 06-12z time frame more to the north. Mid-level radar echoes have been gradually expanding across SW-central OK likely in response to this increased forcing. An environment characterized by steep lapse rates above the cold air at the sfc may be supportive of CSI in the elevated front zone, and thus some heavy banding of snow may occur late tonight into Sunday morning. The overall message of the forecast remains the same tonight as a significant winter storm is shaping up for a large part of eastern OK and northwest AR. Dynamic upper level system located near the Four Corners, which has produced numerous CG lightning strikes across NM/AZ this evening, continues to move east, and will provide a prolonged period of strong forcing over much of the area. North winds have begun to increase over the past couple of hours in response to the approaching system, with gusts around 25 mph becoming common across northeast OK. Wind chills have fallen below -5 in parts of NE OK as a result and while this is technically wind chill advisory criteria, this will be covered by the winter storm warning beginning at midnight. Higher dew points depressions seem to have cut off the lake effect snow across eastern OK, however sfc reports indicate there is still some ongoing in the FYV have added flurries into the forecast for the remainder of the evening. Per satellite this appears to be mainly down wind from Beaver Lake. && .PREV DISCUSSION... /Issued 554 PM CST Sat Feb 13 2021/ AVIATION... CONCERNING TAF SITES KTUL/KRVS/KBVO/KMLC/KXNA/KFYV/KFSM/KROG. Bands of light to moderate snow are expected to develop across northeast Oklahoma late tonight with locally heavier bands possible across aforementioned area into the morning hours. Areas of snow will spread into southeast Oklahoma/northwest Arkansas by late morning with snow expected to continue at all TAF sites through the end of the forecast period. LIFR conditions will briefly be possible in the heavier snow bands, otherwise IFR conditions will likely prevail. Exact timing of the heavier bands will try to be resolved on subsequent forecasts. PREV DISCUSSION... /Issued 148 PM CST Sat Feb 13 2021/ DISCUSSION... The deepening and drying arctic air mass has resulted in an end to the flurries for the most part as well as the lake effect snow. There are reported sightings of the star about 92 million miles away from us. Some folks call it the sun. All I know is it`s nice to see. This appearance will be brief. We`re expecting the onset of the much talked about winter storm to be after midnight tonight. CAM guidance is keying in on a frontogenetic band setting up close to the I-44 corridor to the north of the 850mb frontal zone, where locally heavy snows are likely. The narrower and more intense nature of the band depicted in the CAMs suggest some CSI and maybe a rumble of thunder. This band will gradually shift east thru the day Sunday and weaken while another band along the 700mb frontal zone advances WNW to ESE across the entire region Sunday afternoon and night. The event comes to a rather quick end Monday. The upper system is expected to remain more of an open wave with the bulk of the forcing and QPF with the upper system itself to stay just to the south and east of the forecast area. This has resulted in an overall reduction in snow amounts over portions of northwest Arkansas and southeast Oklahoma. Nevertheless, expected amounts are at least close to warning criteria, then you combine that with the high impact to travel from blowing and drifting snow and the dangerous wind chills. The next system will follow quickly on its heels Tuesday night into Wednesday. There is still quite a bit of uncertainty regarding some important details. The GFS is painting the picture of an epic snowstorm for our area, while the EC is not. There are significant differences in the amount of QPF that will fall over our area. Will continue the theme of the previous forecast with the heavier snow potential south of I-40. Bottom line, this system has the potential to be a high impact to travel, but uncertainties in the details still exist so don`t get too hung up on amounts at this point. A warming trend will start in the wake of this system toward the end of the week on into next weekend, slowed initially by snow melt. Lacy && .PRELIMINARY POINT TEMPS/POPS... TUL 5 9 -2 5 / 80 90 80 10 FSM 16 20 7 14 / 0 80 90 20 MLC 11 16 0 9 / 40 90 90 10 BVO 3 7 -5 4 / 80 90 70 0 FYV 6 14 0 10 / 20 80 90 10 BYV 5 12 -1 8 / 10 80 90 20 MKO 9 12 -1 7 / 50 90 90 10 MIO 2 7 -5 5 / 40 90 80 10 F10 6 11 -2 7 / 70 90 80 10 HHW 18 22 5 14 / 0 70 90 20 && .TSA WATCHES/WARNINGS/ADVISORIES... OK...Winter Storm Warning until 6 PM CST Monday for OKZ049-053>076. AR...Winter Storm Warning from 6 AM Sunday to 6 PM CST Monday for ARZ001-002-010-011-019-020-029. Wind Chill Advisory until 6 AM CST Sunday for ARZ001-002-010-011. && $$ SHORT TERM...14