Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/03/20

National Weather Service Albany NY
943 PM EST Sun Feb 2 2020 .SYNOPSIS... Some light snow showers and flurries will continue overnight ahead of a warm front. The best chance for a light accumulation of snow will be over the Catskills. Dry and milder weather will follow behind this system on Monday into Tuesday. A frontal system will bring a chance for a few rain showers on Tuesday, followed by colder, but dry weather on Wednesday. Unsettled weather looks likely late in the week. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... As of 943 PM EST...A warm front continues to lift north/northeast toward the southern reaches of the forecast area early tonight with some patchy light snow showers and flurries impacting the Mohawk Valley and the Capital Region south. The latest radar trends and 3-km NAM and 3-km HRRR shows the diminishing activity, except west of the Hudson River Valley. This is likely due to the weak forcing and a slightly drier air mass over the ALY forecast area. The KALY sounding has a PWAT of 0.34" some dry air below H700. Overall, the snow will continue to weaken, as it approaches the northern portion of the forecast area. The low-level baroclinic zone is not as strong this far north and east. Lows tonight will be mainly in the 20s to around 30F. Scattered light snow showers or flurries will end in the early morning hours. The greatest accumulations will be over the eastern Catskills and possibly the western Mohawk Valley with a half an inch to an inch. Expect a coating to a few tenths in most other locations. && .SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/... Any scattered, light snow flurries will end early Monday. A much warmer air mass over the Ohio Valley with current temperatures above 50 as close as southwestern Pa will try to push east- northeast toward the area Monday afternoon, but the flow pattern does not look to support a really strong push of warm air. Certainly Monday will be warmer than today with highs well above normal, but at this point highs Monday afternoon look to be mostly in the 40s. Much of the area could see at least partial sunshine. A frontal zone will organize from the northeast southwest to the Tennessee Valley Monday night and Tuesday, as arctic high pressure builds southeast from central Canada while warm ridging holds over the southeast U.S. Scattered, light showers will become increasingly likely along this boundary Tuesday and Tuesday night. Temperatures will remain well above normal for our area through Tuesday night with highs Tuesday once again into the 40s and lows Tuesday night only near freezing. Ultimately, the arctic high pressure area will manage to push southeastward far enough to push the frontal zone south of the area on Wednesday. Temperatures will be colder on Wednesday, although still just near to even slightly above normal. The chance of showers will decrease as cold, dry air will filter in from the north. The location of this frontal zone along with details regarding the track of a series of waves moving along the front will make for a very difficult extended forecast through the second half of the week. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... Active weather appears increasingly likely during the long term with the potential for rain, snow, and mixed precipitation. Predictability continues to be rather poor, particularly in the specific details, although confidence is moderate to high for moderate to locally heavy amounts of QPF for Thursday into Friday. The flow pattern will be characterized by a positively tilted, deep midlevel trough over the Desert Southwest early in the period. The trough will shift eastward across the CONUS during the rest of the week, becoming increasingly negatively tilted with time and inducing cyclogenesis. The attendant cyclone will develop northeastward Wednesday night into Friday, but it is uncertain which side of the Appalachians it will track. Models have trended slightly farther south and east with the overall track, although the 12Z/02 ECMWF remains farther west with the midlevel trough axis and resulting surface low track from the Ohio Valley to the central/eastern NY, while the 12Z/02 GFS deterministic model and GEFS mean have the low track closer to the I-95 corridor (although the GEFS mean is farther north/west than the GFS, suggesting there are several other members with a track more north and west). Background larger-scale atmospheric indices would seem to favor a more inland track, given a strongly +AO/NAO persisting and MJO remaining or entering within a weak phase 6. The most impactful period appears to be late Wednesday night into Friday associated with the negatively tilted trough and surface cyclone. Model consensus supports the local forecast area being on the cold side of the front Wednesday night. So, as isentropic lift across the strong front ramps up late Wednesday night into Thursday morning, there is increasing confidence in a period of accumulating snow for at least the onset late Wednesday night into Thursday morning. Thereafter, uncertainty arising from differences in the low track (as discussed above) increases. Will work a trend of snow to mix to rain from south to north into the forecast for Thursday afternoon into Thursday night. The ECMWF camp is warmer with the more westerly low track and would generally support a quicker transition compared with the GFS/GEFS mean. Timing differences arise for Friday, with the GFS prolonging steady precip into Friday afternoon while the ECMWF works drier air in. Some concern for icing due to a prolonged period of freezing rain across portions of the upper Hudson River Valley, eastern/central Mohawk Valley, southeast Adirondacks, and portions of southern VT, as there is some potential for shallow cold air to remain entrenched longer in some of these areas. So to summarize possible hazards: A widespread/prolonged event is likely late Wednesday night into Friday, with low confidence in precip types. There is increasing confidence for a period of accumulating snow late Wednesday night into Thursday morning. The snow is expected to turn to a wintry mix (sleet/freezing rain) and plain rain over some/all of the forecast area Thursday afternoon through Friday, with low confidence in timing/location of changeover at this time. Precipitation may change back to snow or snow showers Friday afternoon along with gusty west to northwest winds in the wake of the storm system. Early indications for Saturday are for a cooler and drier airmass arriving, but possibly some lingering high terrain snow showers. However, another fast moving low pressure system could bring some snow to the region by next Sunday. && .AVIATION /03Z MONDAY THROUGH FRIDAY/... A warm front will lift northward across the region tonight with some light snow overspreading the region. The light snow should taper in the early morning to flurries as weak high pressure builds in from the south and west on Monday. VFR conditions will lower to MVFR or spotty IFR as the light snow moves in. The greatest threat for IFR conditions will be KPOU in terms of cigs, and possibly KPSF between 02Z-06Z. KALB/KGFL will have cigs lower to MVFR levels with the light snow also moving in between 02Z-06Z/MON. The light snow will taper to flurries between 06Z-10Z with mainly MVFR or low VFR cigs. The cigs will gradually improve to VFR levels in the late morning at all the TAF sites. After 17Z/MON, expect some scattered stratocumulus and scattered to broken cirrus to be around at all the TAF sites. The winds will be light to calm tonight. They will increase from the west to southwest at 4-8 kts prior to 12Z, and expect a shift to the west to northwest at 8-15 kts with some gusts 20-25 kts at KALB/KPSF by the afternoon. Outlook... Monday Night: No Operational Impact. NO SIG WX. Tuesday: Moderate Operational Impact. Chance of RA...FZRA. Tuesday Night: Moderate Operational Impact. Chance of RA...SN. Wednesday: Low Operational Impact. Slight Chance of RA...SN. Wednesday Night: High Operational Impact. Likely SN. Thursday: High Operational Impact. Definite SN...SLEET. Thursday Night: High Operational Impact. Definite FZRA...SLEET. Friday: High Operational Impact. Breezy. Likely SHRA...SHSN...RA...SLEET. && .HYDROLOGY... No hydro issues are expected through the first half of the week. We continue to monitor trends for the later half of the week as significant amounts of precipitation appear to be possible, although precipitation type remains quite uncertain. Some precipitation will occur tonight, with mainly light snow showers or flurries. Total QPF will range from a mere few hundredths to maybe just over a tenth of an inch in the Catskills, where an inch or two of snow could accumulate. A dry stretch of weather is then likely Monday into early Tuesday before more unsettled weather returns mid week. For details on specific area rivers and lakes, including observed and forecast river stages and lake elevations, please visit the Advanced Hydrologic Prediction Service /AHPS/ graphs on our website. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. MA...None. VT...None. && $$ SYNOPSIS...MSE/Wasula NEAR TERM...Wasula SHORT TERM...MSE LONG TERM...KL/Thompson AVIATION...Wasula HYDROLOGY...MSE
Area Forecast Discussion
National Weather Service Amarillo TX
600 PM CST Sun Feb 2 2020 .AVIATION...00z TAF Cycle... VFR conditions are expected through the period. However, a cold front is expected to move through the northern terminals after 12z and may produce some low ST. Confidence is not high enough to include as of this TAF issuance, but if the trends continue MVFR/IFR cigs may need to be introduced at KGUY for a few hours starting around 15z Monday. The front will switch winds from southwesterly to northerly at 10 to 20 knots, and may stall before arriving at KAMA late Monday. Southwest winds could become gusty ahead of the front, which would include KAMA Monday afternoon. Ward && .PREV DISCUSSION... /Issued 334 PM CST Sun Feb 2 2020/ SHORT TERM...Tonight through Wednesday Night... High pressure remains over the Panhandles today and for most of tomorrow, with the next big system moving in tomorrow night. Highs across the Panhandles on Monday should still be very mild, in the 60s to 70s across the south, and in the 50s to the north. There is the potential that this could change but even the high resolution HRRR model suggests that the front will stall just south of the OK Panhandle, until after sunset and then push further through Monday night. In the past this much cold air typically would struggle to stop, but there is a weak shortwave trof expected to swing through under the southwest flow and that might be just enough to help the front stall. Monday evening the front will continue through the Panhandles and winds will be out of the north, with a rapid drop in temperature along with wind chill values around 0 in the north and in the upper teens to the south. While moisture will be limited in the west and northwest, there will be some moving in with the positively tilted trof and we could see light accumulations in the 1 to 2 inch range. The upper level trof will stall and deepen over the southern NM/AZ border by Tuesday evening, and this will provide enhanced moisture across the southern and southeastern Panhandles. The main swath of moisture looks to bullseye over the Lubbock area, but there`s a decent amount that could provide impacts to the southern Panhandles. SREF/GEFS plumes as well as the EC and Canadian model suggest quite a bit of snow potential for the south and southeast, but if the system dips further south, it could dry slot us and then we get nothing. Right now the consistency in the deterministic EC/Canadian/NAM models suggest it will snow quite a bit Tuesday afternoon through Wednesday morning across the southern Panhandles. Current forecast is 1 to 3 inches with the southeast getting the most. This is a very conservative amount, as we have quite a bit of moisture from the Gulf overrunning the cold air, and we are saturated up to 300mb. In addition we have decent lift, and a 700mb warm nose. The warm nose has no significance for precipitation type however it does pose the potential for steep lapse rates aloft and possibly convective precipitation. Yes this would include isolated thunder, or just heavy bursts of snow. Now onto the snowfall rates. This is another challenge as we could have very high snow to liquid rates with surface wetbulbs in the teens to low 20s. Our current rate is run at 18:1(1 inch of liquid equals 18 inches of snow), typical Panhandle rates are closer to 10:1. We could very well be too low and have rates in the 25:1 - 30:1 range. So we could have some very high snowfall amounts with future updates, and watch/warning level highlights could be needed. Keep up with the latest forecast as changes are likely. Weber LONG TERM...Thursday through Saturday Night... Between 00Z and 06Z Thursday, southwest flow aloft will quickly turn to northwest flow aloft as the H5 trough moves east out of the area. This will bring forth a gradual warming trend going into next weekend. During the overnight hours Wednesday night into Thursday morning the combined Panhandles will experience one more night of below normal temperatures in the teens. Highs will make it into the upper 40s on Thursday. Friday morning lows will be near normal for the FA, with daytime highs may be 5 degrees above normal with highs in the mid to upper 50s. Saturday will be similar with slightly warmer lows in the southeast Texas Panhandle. Winds are looking to be relatively light for Panhandle standards during this extended forecast period. A leeside surface low could develop in the northwest Saturday night. If this pans outs winds could be a bit breezy Saturday evening into overnight. Mostly clear skies until Saturday when the H5 flow becomes more zonal and the FA could see some high clouds develop. Hoffeditz AVIATION...18Z TAFS... VFR conditions will prevail at all TAF sites with winds out of the west southwest for the majority of the TAF period. Winds in the 10 to 15kt range expected with gusts up to 25 kts possible. Winds may shift more westerly as we head into the end of the TAF period. Scattered mid and high clouds possible. Cold front expected tomorrow, but for now frontal timing looks to be after 18z. However, would not rule out the front speeding up and wind shifts out of the north coming sooner. Weber FIRE WEATHER... Critical Fire Weather conditions expected to continue for a few more hours across Cimarron County as winds around 20 mph and RH values in the single digits should start to recover after sunset. RFTI`s look to be in the 3 to 5 range for a few more hours. No other Fire Weather concerns for the remainder of the forecast period. Weber && .AMA Watches/Warnings/Advisories... TX...None. OK...Red Flag Warning until 7 PM CST this evening for the following zones: Cimarron. && $$ 7/89
Area Forecast Discussion
National Weather Service Green Bay WI
543 PM CST Sun Feb 2 2020 Updated aviation portion for 00Z TAF issuance .SHORT TERM...Tonight and Monday Issued at 154 PM CST Sun Feb 2 2020 The latest RAP analysis and satellite/radar imagery show an area of low pressure over eastern Lake Superior and a cold front extending west from the low across central Minnesota. Relatively shallow cold air across northern WI into Minnesota along this front has contributed to a large area of low stratus which had been slowly moving to the southeast earlier today. Ample dry air on the 12z GRB and MPX soundings have halted the forward progress of this stratus. Where sunshine has occurred for most of the day (generally south of HWY 29), temps are close or have surpassed records for the date. Winds have behaved themselves so far, with only a few gusts above 30 kts. As the cold front gradually drops south, forecast concerns may revolve around cloud cover and temps. Tonight...The cold front will move across most of northern WI in the evening and settle south of the area overnight. Not expecting much further progress south of the low clouds. But in general, think low clouds will be retreating northeast. Mid and high clouds will likely push in from the west through the night, but a large dry wedge between the two cloud layers will keep precip from reaching the ground. With winds diminishing and cloud cover, stayed close to the national blends for temps. Monday...Mid and high clouds will continue to move overhead and provide filtered sunshine at times. Winds will shift around from the northwest to the northeast with weak cold advection continuing through the day. Temps will be much cooler than today, although with less wind, with highs ranging from the upper 20s to middle 30s. .LONG TERM...Monday Night Through Sunday Issued at 154 PM CST Sun Feb 2 2020 Surface and upper air patterns favor quiet weather across northern and central Wisconsin for the rest of the week. The upper flow remains split with the stronger shortwaves in southern stream forecast to stay far enough away to keep significant snow to the south. With the storm track to our south, Gulf moisture will not be able to get this far north. A few shortwaves in the northern stream could bring enough Pacific moisture to produce a very small amount of snow at times but nothing significant is expected at this point. Thickness values and 925 mb temperatures suggest that it will be above normal temperature wise except for a brief cool down Wednesday. && .AVIATION...for 00Z TAF Issuance Issued at 535 PM CST Sun Feb 2 2020 Strong west-northwest winds aloft will linger into the early evening at the eastern TAF sites, then diminish. Surface winds will also diminish early this evening. Stratus, with ceilings from 2000-3500 feet AGL, will persist across northern WI this evening, but RH timesections show moisture shallowing out later this evening or overnight. Will hold onto MVFR ceilings at RHI until the early overnight hours. Mid and high level clouds should prevail through the rest of the TAF period, along with light northwest winds veering north to northeast by Monday afternoon. && .MARINE... Issued at 154 PM CST Sun Feb 2 2020 Lapse rates have been unable to become steep enough to tap into the stronger winds aloft. Additionally, the strongest winds have remained over southern WI. As a result, wind gusts have remained below 30 kts through the day. Will therefore downgrade the gale warning into a small craft advisory. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM.....MPC LONG TERM......RDM AVIATION.......Kieckbusch MARINE.........MPC
Area Forecast Discussion...UPDATED
National Weather Service Chicago/Romeoville, IL
925 PM CST Sun Feb 2 2020 .UPDATE... 924 PM CST No notable changes for the forecast into Monday. There is a low chance for patchy shallow fog tonight over the edge of the snow cover area and the periphery of it where temperature-dew point spreads are the lowest. The sky looks to remain mainly clear over this area through the rest of tonight, apart from gradually thickening cirrus near daybreak. The 00Z DVN sounding showed substantial dry air all the way through the boundary layer and RAP soundings basically continue this apart from the immediate surface, so any fog should be very shallow. Not expecting a big deal if any were to develop. For tomorrow, northeast winds will gradually be on the increase as the pressure gradient strengthens. High temperatures may end up being a little cooler than initially forecast, depending on the thickness of the clouds, and could see afternoon readings not climbing much at all north of I-80. The potential for drizzle Monday night continues to look decent in incoming guidance, namely the 00Z NAM and its preceding 21Z SREF. Any drizzle that would have more coverage and overlap with temperatures below freezing is still looking to be overnight and in northern locations, especially those inland away from locations downstream of the slightly warmer lake. MTF && .SHORT TERM... 210 PM CST Tonight and Monday... Today`s record high at ORD that late this morning looked so poised to fall has instead been nicely protected by a well timed arc of opaque cirrus. Cold advection off the snowpack also has not helped warming at ORD, but this did not seem to be a problem at nearby Palwaukee which did reach 51 earlier. Quite a few locations, including ORD, did at least crack the 50s. And there is still time for a rebound at ORD where around 2pm the temperature had briefly recovered to 50 and even touched the record of 51 after a dip back into the 40s. So we will keep watching to see if it can indeed be broken. Breezy west winds also underperformed just a bit today which could be yet another reason that low level mixing and warming was not more pronounced. These winds will veer northwesterly this evening behind a weak front that moved through today, then flip easterly Monday morning ahead of the next boundary approaching from the south as a warm front. With cool and dry advection to the north of this boundary, most of the area will be several degrees cooler than today but should remain dry at least until early evening when precip chances increase slightly toward the WI line. Farther south, mainly along and south of US-24 nearer the front itself, temperatures still should be able to climb into the 50s again Monday. Lenning && .LONG TERM... 330 PM CST Monday Night through Sunday... A few bouts of wintry precipitation are possible this week, but confidence is unfortunately on the lower end. There are three primary time windows of concern in this regard. On Monday night into Tuesday morning, there is a risk for freezing drizzle in parts of north central and far northern Illinois. On Tuesday evening and night, an active baroclinic zone setting up near or just south of the CWA could bring a threat for light snow and minor accums to portions of the southeast CWA Then on Wednesday evening and overnight, there is a chance for accumulating snow for more of the area depending on evolution of a southern stream wave. Finally, with a bout of a long duration of strong northerly winds Monday night through Tuesday night, concern is increasing for lakeshore flooding. On Monday evening and night, an inverted trough axis will stretch northeast across the region, with expansive dry high pressure over the northern Plains. A tight low level thermal gradient will be in place, with gradual cooling of the column oozing from the north. This gradient will set up good lower level frontogenesis. In addition, in broad southwest flow aloft, we`ll be positioned favorably in strong upper jet dynamics. These factors would argue for the possibility of precipitation development. However, the big question mark is the magnitude of moisture in the column. There is strong consensus among the guidance of dry air in the ice nucleation layer, favoring drizzle and maybe light rain if enough collision coalescence and precip is occurring. The main uncertainty pertains to lower level saturation, especially during the evening hours, as there is high variance between the much more moist NAM/WRF guidance and the ECMWF, which is much drier, owing to a slightly farther south inverted trough axis and dry advection from the high pressure. Given the uncertainty, we have a low chance for drizzle mentioned during the evening hours. Confidence increases a bit more, but still on the lower side, overnight into early Tuesday for an increase in saturation depth supportive of drizzle/light rain. During this period, have higher chance PoPs. This is when surface temperatures become critical, as they will be gradually cooling through the night. Portions of far northern and north central Illinois, including Rockford and the far north and northwest Chicago suburbs, could have risk for a light glaze from freezing drizzle. Another uncertainty, if freezing drizzle occurs in the aforementioned risk area, is how pavement temperatures respond after being well above freezing, which will dictate if there`s any travel impacts. The cold and dry advection from the north will likely mostly end any light wintry precip during Tuesday morning for northern areas. Active baroclinic zone will remain draped near or south of the CWA into Tuesday night. Additional short-wave energy rippling along the brisk southwest mid and upper flow and interacting with the baroclinic zone could bring additional light precipitation to portions of the area. By them, DGZ will be sufficiently saturated and temps cold enough for snow as p-type. At this time, guidance consensus favors our southeast CWA for best chance of getting into this precip. Certainly possible the light snow could stay south of the CWA counties altogether, however. After a likely dry period area wide into the daytime Wednesday, we we turn to the next timeframe to watch, later Wednesday PM and night. Sensible weather impacts, if any, depend on the evolution of a southern stream wave and track of associated surface low southeast of our area. This southern stream energy rounding the long wave trough emerging from the Plains region could eventually force the trough to become more neutrally tilted, with surface cyclogenesis along the western or central Gulf Coast on Wednesday. The ECMWF suite shifted southeast from the 00z and 06z cycles, but remained the farthest west of the global guidance with the surface low track across the Ohio Valley Wednesday night. Meanwhile the rest of the globals kept the trough positively tilted for longer, resulting in a farther east/southeast surface low track. Since there has been high run to run variability during the Wednesday PM into Thursday period, maintained NBM PoPs ranging from mid to high chance to low likely from northwest to southeast. Thermal profile would be supportive of snow. Temperatures through the week will be generally seasonable, with active flow pattern continuing into next weekend, so have some periodic low PoPs. LAKESHORE FLOODING Monday Night through Tuesday Night... Expansive high pressure around 1030 mb centered over the northern Plains and low pressure troughing draped south of the area will set up a tight northerly pressure gradient. A long duration of brisk northerly winds will result, peaking on late Monday night into Tuesday morning, when speeds/gusts over the lake could get up to 35 mph if not higher. Winds will stay elevated, but gradually come down in speed later Tuesday through Tuesday night as the surface high approaches and the low pressure trough sinks southeast. At this time, have forecast peak waves in the 8 to 11 foot range along the Cook, Lake IN and Porter County shore. This is close for exacerbated lakeshore flooding impacts for the hardest hit areas from the near record lake levels. We`re headed for needing at least a Lakeshore Flood Advisory, and if confidence increases in a bit higher wind speeds and wave heights, a Lakeshore Flood Watch to Warning may be needed. Castro && .AVIATION... For the 00Z TAFs... Occasionally gusty west winds will continue to abate early this evening. The next feature of interest is a cold front to our north which is slated to bring a gradual northeast wind shift to the area terminals later tonight. Winds look to slowly swing through the northwest, north, and eventually northeast, and so have indicated the most likely arrival of the more persistent northeasterly winds in the latest TAFs. As this boundary passes, some additional low-level moisture will start to drift northward and, as it encounters the cooling surface, may result in the development of some light BR. Signal for BR is not overly impressive, but warranting of a TEMPO mention for 5sm at RFD and DPA, and 6sm at ORD and MDW. Could also envision some splotchy MVFR cigs developing late tonight. Any vsby reductions and lower cigs should scatter out through the morning hours on Monday, but do look to return during the afternoon and evening as the lower-levels incrementally saturate ahead of a sharpening surface trough. For the ORD/MDW extended: there is some signal that some light precipitation/drizzle may develop towards the late-evening hours, but confidence on this timing is too low to warrant a TEMPO or a PROB30 mention right now. Do think this potential will increase after 04.06z but with winds prevailing off the relatively warm lake, current expectation is for any -DZ to fall into above-freezing air at the surface. This potential will be addressed in future TAF issuances, however. Carlaw && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ Visit us at Follow us on Facebook, Twitter, and YouTube at:
Area Forecast Discussion
National Weather Service Marquette MI
651 PM EST Sun Feb 2 2020 .SHORT TERM...(This evening through Monday) Issued at 323 PM EST SUN FEB 2 2020 What a difference an extra day of models makes as today`s winds are much lighter, temperatures cooler, and skies...well still gloomy. A low stratus deck remains across all of the forecast area and extends in northern WI as well as slightly colder air aloft has helped these stratus stick around. Latest guidance continues to show weaker winds aloft as RAP soundings suggest the boundary layer is still mixing through about 3000 feet. The northern portion of Upper Michigan is still seeing some -SHSNDZ this afternoon along a line from roughly Grand Marais, MN through Manistique. Models suggest weak warm air advection ongoing ahead of these showers, as the UP also remains on the fringe an approaching broad mid-level ridge which is creating some PVA and divergence aloft as well. As this ridge continues to move east this afternoon, any PoPs will slowly depart from west to east as RAP soundings show deep moisture comes to an end and inversions falling to near 3500 feet. Tonight, with drier air aloft moving into the region there will be a chance for some clouds to scatter out, but generally expecting mostly clouds skies. Winds will remain elevated through the first half of the evening which should help keep temperatures in check. Lows will remain in the 20s with low 20s across the western interior and mid to upper 20s elsewhere. Winds relax through the evening and into tomorrow morning as 850mb temps fall to near -12C. These temps are cold enough for LES to begin to develop...but inversion remain low with a bit of dry air near the sfc. Winds will remain from the NW through the day as colder air aloft continues to work its way into the region. Near the end of the day, we may start to see some LES in the NW wind snow belts across the west, with the eastern half remaining a touch too warm. High temperatures remain a touch above normal with upper 20s in the west and low 30s east and along the Great Lakes. .LONG TERM...(Monday night through Sunday) Issued at 433 PM EST SUN FEB 2 2020 Models suggest that a mainly split flow pattern will persist. An incursion of colder air is expected Tuesday into Wednesday as a slightly more amplified northern stream brings a batch of arctic air through northern Ontario. Although a mid/upper level trough will move into the central CONUS by Thursday, with a trend toward little or weak phasing of the positive tilt system with the southern stream, chances for any significant snowfall remains low. Monday night, weak shortwaves moving into northern Ontario will help drop an arctic cold front into the northern Great Lakes as the northern stream trough sags into the area. CAA with 850 mb temps dropping from -12C to -15C will provide just enough instability to support nw TO nnw flow LES. However, only chance POPs mentioned with any accumulations remaining at or below an inch. Tue-Wed, With only shallow cold air (inversion heights of 3k-5k ft) and 850 mb temps to around -20C developing anticyclonic low level flow, nw flow LES that develops should be light. However, lake induced CAPE increases enough with the convective layer through the DGZ for a few inches of fluffy snow. Winds backing to west and sw Wed should bring an end to the LES after some additional SHSN over the Keweenaw in the morning. Thu-Sun, the models, including the ECMWF have trended away from the potential of any significant system snow into Upper Michigan, closer to the drier GFS/GEFS/GEM. The pattern is expected to amplify toward the end of the week so that an additional batch of arctic air brushes the northern Great Lakes. 850 mb temps down to around -15C may bring some light LES from Friday into Saturday. There is low confidence that additional shrtwvs will bring any significant snow through the weekend. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 650 PM EST SUN FEB 2 2020 While MVFR cigs will mostly prevail at KIWD/KCMX/KSAW tonight/Mon, there will be periods of VFR conditions. Gusty winds to around 25kt are expected at KCMX thru the fcst period. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 323 PM EST SUN FEB 2 2020 NW winds with gusts up to 30 knots will develop this evening into tomorrow morning before calming down through the day on Monday. NW winds pick up again on Tuesday afternoon with a few gusts up to 30 knots before calming down by Wednesday morning. SW winds then pick up Wednesday evening into Thursday with a few gusts approaching 30 knots. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...JAW LONG TERM...JLB AVIATION...Rolfson MARINE...JAW
Area Forecast Discussion
National Weather Service Portland OR
325 PM PST Sun Feb 2 2020 .SYNOPSIS...Showers will increase along the coast this afternoon as a weak trough of low pressure moves onshore. Scattered showers will spread inland this evening, but should generally decrease in coverage overnight. Snow levels will approach the lowest elevations this evening, so it is not out of the question that some coastal or valley floor locations could get a dusting of snow overnight. Chilly weather and a few showers will linger through Monday. A warm front Tuesday will bring a return to milder weather pattern with occasional rain for the middle to latter portion of the upcoming week, especially north. && .SHORT TERM...Tonight through Wednesday...Visible satellite imagery shows a loosely organized cluster of showers near the Pac NW coast this afternoon. These are associated with a lobe of cold air aloft, modeled at -37 to -38 deg C at 500 mb. Despite the fairly steep lapse rates from the surface up to 500 mb, it appears lightning has mostly come to an end over the coastal waters. That said, cannot completely rule out a stray clap of thunder or two along the coast or over the adjacent waters. The band of showers is making slow eastward progress, but the best dynamic forcing appears to be aimed to our south, toward Del Norte and Humboldt Counties in California. The showers off the OR/WA coast may hold together enough to produce scattered snow accumulations in the Coast Range above 500 feet by later this evening, but generally only a dusting to an inch. Aside from this band of showers, there are several small showers scattered around SW Washington/NW Oregon this afternoon, mostly driven by daytime surface heating and the resulting steep or even super-adiabatic lapse rates given the much colder air just above the surface. These showers seem to be producing mainly small graupel for the lowlands, briefly accumulating on grassy surfaces but otherwise not producing much of an impact. Some higher resolution models such as the 18z NAM 4km Nest and HRRR hint that another band of showers may form over the Willamette Valley overnight. With the loss of daytime heating and temps beginning to warm aloft this evening, it is difficult to see enough instability remaining in place for convective showers east of the Coast Range much later than 6 or 7 PM. We generally undercut model PoPs after 06z tonight, but left a slight chance just in case the above-mentioned models are correct in generating just enough synoptic lift to overcome an increasingly stable environment. If this were to occur, most of the precipitation would fall as snow, but any accumulations would probably be light and spotty. High pressure moves into the area Monday, but lingering moisture and onshore flow will provide a slight chance for showers, mainly across the higher terrain. The airmass remains cool with snow levels 800-1200 feet. Showers will end Monday night, and any clearing could lead to freezing fog in the interior valleys through early Tuesday morning. A warm front is expected to bring rain and rising snow levels Tuesday evening. The snow levels may remain low with the light rain ahead of the front Tuesday afternoon, but rise when the steadier rain arrives Tuesday night. The rain will persist into Wednesday night with the snow levels up to 3500-5000 feet early Wednesday. The Willapa hills and the north Oregon coast range could get up to 2 inches of rain Tuesday night through Wednesday afternoon. The south Washington Cascades may see 5 to 10 inches of snow. Weagle/TJ .LONG TERM...Wednesday night through Saturday...Models vary with the finer details, but the overall consensus is for a very wet pattern across western Washington for the latter half of the upcoming week, while western Oregon sees rain at times but not nearly as much as their neighbors to the north. A flat upper level ridge may keep the southern portion of the forecast area mostly dry and mild Thursday and Friday, but there is fairly good consensus that the upper ridge will erode enough to allow a cold front to press southward across western Oregon Fri night/Sat. Models and ensembles generally agree on a return to seasonably cool weather behind this front next weekend. Will need to keep a close eye on the Willapa Hills as the Grays River has been rather sensitive to rainfall much more than 1.00 to 1.50 inch over a 24-hour period. It appears many basins are saturated from all the rain we have received over the past month, but hopefully the 24-48 hour break from significant rainfall will raise the bar a bit in terms of the rainfall required to push our more sensitive small streams and rivers to flood stage. Weagle && .AVIATION...VFR conditions continue to persist through much of the area with a veil of MVFR cigs over the northern Willamette Valley and coast. Convective showers continue this afternoon with some reports of small graupel or hail near the Portland- Metro. A shortwave will move over the area Sun night after 02Z Mon. While very isolated, the convective rain showers will persist overnight. Cigs will also drop to MVFR, especially along the coast, and the central and northern valley. VFR cigs return Mon morning around 20Z. The challenge tonight will be whether or not fog develops again. The dewpoint depression in many places inland are within 2 degrees F and near freezing. There is also a chance for frost development, similar to the Sun morning. Temperatures inland will float right around freezing, but snow is not expected. At this time, will put some localized fog into some TAFs. KPDX AND APPROACHES...Cumulus and showers through the afternoon ahead of a shortwave. In some of the showers, graupel has been reported. Frost/fog is possible again tonight with temps around freezing. VFR cigs will become MVFR overnight which may keep fog at bay. Cigs should lift again to VFR Mon around 18Z. -Muessle && .MARINE...Fairly consistent conditions through the next week with seas ranging from 11 to 14 ft with a 13 second period. Winds will be 10 to 20 kt through Mon then fall below 15 kt Mon afternoon. At that time seas will also fall below 10 ft allowing for the small craft advisory to expire for a period. High pressure over the Pacific will remain anchored Mon afternoon through Wed. Overtime, this high has flattened out slightly making the flow mostly westerly, however typical weather associated with high pressure will remain. By Wed night, confidence dwindles as there is a chance for a closed low pressure system to move south from the Gulf of Alaska. At this point, models are fairly inconsistent. A majority of solutions are showing a less robust low moving along the coast line, while some international models show a true closed low moving over the state. At this time, stayed conservative with the overall flow and thus kept seas around 15-16 ft with a 16 second period Wed night through Thu. -Muessle && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory until 10 PM PST Monday for coastal waters from Cape Shoalwater WA to Florence OR out 60 NM. Small Craft Advisory until 1 AM PST Monday for Columbia River Bar. Small Craft Advisory from 8 AM to 3 PM PST Monday for Columbia River Bar. && $$ Interact with us via social media: This discussion is for Northwest oregon and Southwest Washington from the Cascade crest to 60 nm offshore. This area is commonly referred to as the forecast area.