Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/19/20

National Weather Service Wakefield VA
714 PM EST Tue Feb 18 2020 .SYNOPSIS... A cold front crosses the area late tonight, then stalls along the Gulf coast Thursday. Low pressure tracks northeast along this boundary Thursday night into Friday as arctic high pressure plunges into the nations mid section. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... As of 710 PM EST Tuesday... Early evening analysis reveals sfc low pressure over SErn Quebec/nrn NY. The associated sfc cold front extends SSW across east-central PA, wrn VA into the eastern TN Valley and the western Gulf coast. Forecast generally on track this evening. Did make minor changes to PoP to reflect CAMs, with HRRR and NMM handling scattered showers ahead of the front a bit better this evening. Front will push across the region late tonight/overnight, and will be south of the area into the Carolinas by sunrise. Scattered showers (NW) with a dry start across the coastal plain early this evening, with likely to categorical PoP overnight as moisture streams NE along and ahead of the advancing cool front. Nudged temps up a bit to reflect slightly slower timing, but overnight lows in the 40s for most still looking good. Previous discussion... As of 245 PM EST Tuesday... Has turned out to be a pretty decent day wx wise over the FA. Clouds will lower and thicken early this evening then rather large area of SHRAs will be moving into/across the FA (beginning by mid eve W/central areas then at the coast mainly after 00Z/19. QPF to avg one tenth to one quarter N and NW to 1/2 to 3/4 of an inch S and SE. Limited or no clearing before 12Z/18. A mild night w/ lows 40-45F (except u30s far NW). && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/... As of 310 PM EST Tuesday... SHRAs may linger far SE VA-NE NC in the morning (esp early)...otw the front continues to push S to the gulf coast. Clearing is expected through the day from NW to SE (late) as large cold sfc hi pres pushes SSE across the nrn Plains. N winds will remain a bit gusty...Mainly at the coast (before diminishing in the afternoon/evening). Highs from the u40s-l50s. Clear-partly cloudy and near seasonable wx Wed night w/ lows from the u20s N and NW to the m-u30s far SE. Yet another system will begin spreading moisture quickly into the region from the WSW Thu. Weak lo pres will be tracking E along the stalled frontal boundary INVOF gulf coast. Upper level confluence right over the FA and that will likely become the nrn fringe to any pcpn late Thu-Thu night. While lo pres tracks off the SE CONUS coast Thu...hi pres will continue to settle/spread out gradually from the Midwest to the nrn mid-Atlantic region. This is one of only a very few storms to track by to our S this Winter (so far) and offers the best chc at winter pcpn (SN) here (since Nov). Highs Thu in the l-m40s. Of course...there remain model differences. The NAM/GFS continue to be farther N (and aggressive w/ QPF) into the cold while the ECMWF remains consistent in keeping much of the system`s moisture S of most of the FA (outside of mainly NE NC). Would be more inclined to be more aggressive w/ pcpn (farther N) if the NAM/ECMWF were in sync. They are not (and have not been). Will the middle ground GFS win this battle? For now...its a RA to wet SN scenario from late Thu afternoon into Thu night. Have nudged/increased QPF (and corresponding SN accums) a bit N of the previous fcst (more in line w/ WPC)...but will let the models fight it out over the next 12-24 hrs before committing to a wetter or drier soln. So...accums aob 2" (little or nothing N of a FVX-RIC-WAL line)...highest across NE NC (by after midnight Thu night). Becoming breezy/windy...esp at the coast. Pcpn expected to end in SE VA-NE NC very late Thu night/early Fri. Lows in the l-m20s inland to the l30s right at the coast in SE VA-NE NC. Hi pres and clearing out for Fri...though chilly w/ highs in the u30s-l40s. Remaining breezy at the coast. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... As of 230 PM EST Tuesday... After a chilly night Fri night w/ the center of sfc hi pres arriving late...Sat will be dry w/ seasonable conditions. Hi pres moves off the coast Sat night-Sun as lo pres develops/tracks into the mid MS Valley. Return S flow behind the depart high will lead to milder wx Sun and expecting mainly high clouds to arrive from the W (esp in the afternoon). Lo pres tracks from near the OH river on to the ENE Mon then through the nrn mid- Atlantic region (late Mon night) and off the coast Tue. 12Z/20 GFS slightly slower than the 12Z/20 ECMWF w/ its movement E. Will have PoPs increase sharply by Mon afternoon/evening then begin to taper off (W-E early) Tue. Lows Fri night from the l-m20s inland to the u20s-around 30F at the coast. Highs Sat in the u40s-l50s. Lows Sat night in the u20s inland to the l-m30s at the coast. Highs Sun mainly in the m-u50s. Lows Sun night in the m-u30s inland to 40-45F at the coast. Highs Mon the m-u50s. Highs Tue from the m50s on the ern shore to the u50s-l60s elsewhere. && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... As of 710 PM EST Tuesday... VFR conditions across area terminals this evening will give way to thickening/lowering CIGs overnight ahead of a cold front. That front will approach and move through the area late tonight, quickly bringing widespread rain and IFR conditions for the area, with best rain chances between 02-10z across terminals. A period of IFR conditions is expected across all sites generally from 05z- 10z (expect until after 12z at ECG). However, after the cold frontal passage overnight, expect VFR conditions to rapidly return from NW to SE Wed morning. OUTLOOK... High pressure returns Wednesday aftn into Thursday morning. Low pressure tracks across the Sern Conus Thurs night. This will bring a chc of a brief rain/snow mix then all snow for far srn VA and NE NC along with degraded flight conditions. High pressure returns Friday into Saturday. && .MARINE... As of 350 PM EST Tuesday... High pressure over the area is moving offshore in advance of an approaching cold front associated with low pressure over southern Ontario. Winds are out of the south at 5-10 knots on the western periphery of the surface high. Waves in the bay are around 1 foot while seas offshore are running 2-4 ft. The aforementioned cold front crosses the region after 06Z tonight from north to south. Decent pressure rises coupled with CAA and dry continental air behind the cold front will lead to a period of enhanced NNW flow through early Wednesday afternoon. Winds increase to 20-25 knots with gusts to 30 knots for the Ches Bay, Currituck Sound and offshore zones. Opted to raise headlines for the Lower James River with this forecast package due to winds increasing to 20 knots with a gusts to 25 knots tonight. Winds will be a little slower to subside across the southern bay Wednesday morning so the SCA flags there are now in effect through 18Z. Left offshore headlines untouched with the region south of Parramore Island included in the SCA for seas building to 5 ft through Wednesday evening. The extended portion of the marine forecast remains uncertain with increasing potential for low pressure to form off the Southeast coast on Thursday as arctic high pressure over the central Plains builds southeast. How far north the low comes will have significant impacts on the wind/wave/seas forecast. Consensus of the models this afternoon suggests SCA conditions for all waters from late Thursday night through Friday with some potential for low-end Gale conditions across the southern coastal waters. && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory from 4 AM to 1 PM EST Wednesday for ANZ632-634-654. Small Craft Advisory from 4 AM to 6 PM EST Wednesday for ANZ633-656. Small Craft Advisory from 4 AM to 10 AM EST Wednesday for ANZ630-631-638. Small Craft Advisory from 4 AM to 10 PM EST Wednesday for ANZ658. && $$ SYNOPSIS...MAM NEAR TERM...ALB/MAM SHORT TERM...ALB LONG TERM...ALB AVIATION...MAM MARINE...RHR
Area Forecast Discussion
National Weather Service Amarillo TX
525 PM CST Tue Feb 18 2020 .AVIATION... For the 00z TAFs: VFR conditions to prevail throughout the majority of the TAF cycle, especially through the first half. Tomorrow afternoon we should see conditions deteriorate (approaching MVFR) as cloud cover increases through the afternoon and evening hours ahead of a cold front. Have not included any precipitation just yet, but KDHT and KGUY may see those chances increase in the next cycle as we are anticipating snowfall Wednesday night. Wind speeds will generally be light and go around the dial. Southerly winds will prevail tomorrow ahead of the front, but a wind shift will be expected in the next cycle as well. && .PREV DISCUSSION... /Issued 320 PM CST Tue Feb 18 2020/ SHORT TERM...Today through Tomorrow... Overcast skies today are keeping temperatures from rising above the 40s across the area. However, clouds are beginning to break across the southeast and west central Texas Panhandle with the chance for temperatures to rise up into the lower 50s. Winds remain out of the north today, but will begin to turn clockwise towards the south through tonight as a surface high pushes southeast across the Oklahoma and Texas Panhandle. Winds will remain from the south through tomorrow with gusty winds of 15-25 mph possible across the far northwest. Temperatures will drop into the 20s across the area tonight and cloud cover tomorrow will keep high temperatures similar to today in the mid 40s to lower 50s. There is a small window early tomorrow morning for a slight chance of snow flurries in the far northern part of the eastern Oklahoma Panhandle with little accumulation expected. RAP soundings are showing a saturated layer through the DGZ; however, the surface to 800mb remains dry. Therefore, the chance for moisture to reach the surface is minimal with recent guidance and will be short lived with little dynamical forcing. The next chance for moisture will tomorrow night and mentioned in detail in the long term discussion. Rutt LONG TERM...Tomorrow Night through Monday... Main story in the long term forecast occurs right at the beginning with the potential for snow Wednesday night into Thursday. Wednesday, as surface ridging builds across the Upper Midwest into the mid-Mississippi Valley and a weak southern stream disturbance translates over the big bend, resulting low level winds across the CWA will become southeasterly, moistening the low levels via upslope flow. Wednesday night, highly positively tilted trough will slide southeast from UT/WY, pushing a front south through the CWA and leading to large scale ascent, particularly across our northern zones. Given the decent low level moisture, this should lead to at least a little light precipitation for a large portion of the forecast area. Additionally, most guidance suggests an 850mb frontogenetic band may set up somewhere across our northwest, allowing for enhanced snowfall rates there. It should be noted that peak ascent associated with these potential frontogenetic zones looks to be displaced vertically from the dendritic growth zone - progged to be located in the 500-650mb layer - which would hold back peak snowfall rates despite the stronger ascent. Main forecast questions remaining are: 1) How quickly will cold air filter in and change the dominant precipitation type to snow? 2) Where exactly will transient areas of 850mb frontogenesis set up? and 3) Will ascent occur within a saturated dendritic growth zone? Trends in guidance continue to suggest that only an hour or two of rain will occur before a change over to snow, so confidence is high that snow will indeed be the dominant precipitation type. On the subject of frontogenetic banding, guidance is giving the usual discrepancies in exact placement, with the best chance for this setting up over our CWA across the western OK Panhandle. Finally, efficient snow production from the dendritic growth zone looks to be the major limiting factor for this snow event. For the southern half of the CWA, the DGZ looks to only be saturated for an hour or two. Across the northern half of the CWA, while broad ascent ahead of the wave and a few more hours of saturation should occur, stronger ascent associated with the previously discussed frontogenetic forcing looks to be displaced vertically from the DGZ, limiting snow production efficiency. For the reasons stated above, this looks to be a typical weak snow event for the Panhandles across all but potentially the western OK Panhandle. Have gone with minor snow amounts across the TX Panhandle and around 1-3 inches across the OK Panhandle, with highest totals across Cimarron County. Moving on in the extended to Friday, as elongated surface ridge builds from S TX into the OH Valley, winds at the surface across the Panhandles look to turn southwesterly. Have thus bumped highs up a bit over consensus blend, with a return into the upper 40s and lower 50s expected after a frigid Thursday. As a weak disturbance approaches the Sangre de Cristos Friday night, expect surface pressure gradient to be maintained overnight due to lee pressure falls. Have thus bumped lows up a bit over consensus as well in deference to continued southwesterly winds during the overnight hours. For Saturday and Sunday, fast moving upper low approaches from the west. Lead disturbances in the west-southwesterly flow aloft may lead to some rain Saturday afternoon and evening. Lee cyclogenesis looks to occur roughly overhead Saturday night with precipitation possible across the northwest quadrant of the resulting low Sunday as the upper low departs to our east. At this time, GFS/EC and all available GEFS members depict 850mb temperatures above freezing Sunday. Will thus keep all mentions of precipitation rain but, given potential for breezy conditions, will need to remain vigilant as even a small amount of snow may lead to deleterious visibility reductions. Next Monday looks to be relatively uneventful. With many different depictions of surface winds seen across operational guidance and ensembles, have stuck with blended guidance for all elements during this period. Ferguson AVIATION...18Z TAFs... VFR conditions are expected at all three TAF sites through the period. Skies are overcast across all sites, but will begin to break at AMA/GUY later this afternoon with high clouds still possible. DHT will likely hold the overcast skies through tomorrow morning before lifting. Winds are out of the north northeast for all three sites before turning clockwise overnight and becoming southerly by 12z tomorrow at DHT/GUY and 16z for AMA. Rutt && .AMA Watches/Warnings/Advisories... TX...None. OK...None. && $$
Area Forecast Discussion
National Weather Service Gray ME
934 PM EST Tue Feb 18 2020 .SYNOPSIS... Low pressure will pass north and east of the region tonight... bringing snow and rain to an end. After a relatively mild day Wednesday...much colder air will arrive Wednesday night through the end of the week. Dry weather will continue through this weekend with temperatures rebounding above seasonal norms. The next chance for widespread precipitation is not expected until at least early next week. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... 930 PM... Extended the WWA where it is in place through, midnight. The HRRR continues to show the precip just disintegrating across all but the mtns over the next hour so, There`s still a pretty decent cluster of precip to our west, and not sure it`ll all end in the next hour, but the trend will be downward through midnight. I so still think temps will surge a bit after midnight, as the flow shifts W, and there`s a deep enough mixing lyr to warm things up before the colder air moves in. Also temps in upstate NY in the upper 30s to around 40 right now, so there`s some support for this upstream. 8 PM...The atmosphere is keeping the mets busy tonight as several surges of precip have occurred and coastal front, which had pushed a little inland, got pushed back back the cold air, not all the way to the coast, but some places went abv freezing and then below. P-type continues to fluctuate, but the good news is that all precip should begin to wind down in the next few hours, at least according to HRRR. As drier air moves in, and when sfc wind shifts to W, will likely see temps rise in many spots for a few hours during the overnight, as the warmer mid- lvl air mixes down. 525 PM...Based on looks at current temps and obs, updated the forecast to try to time p-type changes a little better, although in some areas, especially closer to the coast, where temps have gone abv freezing p-type is fluctuating between rain and snow, as marine got a push from strong onshore flow, but surge backed off a bit and cold wedge between marine air just above the sfc and warmer coming from the S at and abv 850 MB is hanging on. Think by ~00Z these coastal areas should go to just rain. Across srn NH, the warm is progressing NWD, and seeing a short period of PL or FZRA before it warms up a bit there, and this zone will shift north thru the area as well. Timing of precip and amts were only tweaked a little and no change to advisories in store. Previously...Moderate to heavy snow continues for much of the forecast area at this time. These next few hours will be the window for best snowfall accumulation. KBOX 88D shows a well defined melting layer rapidly moving into Srn NH this hour as well. This is well timed to latest RAP guidance...which I leaned on for ptype forecast. So snow will mix with sleet...freezing rain...or rain across Srn NH over the next hour depending on surface temps. Above freezing surface air is moving inland from the Gulf of ME...along with creeping Nwd into NH. This will turn any precip to all rain once the warm air gets deep enough. That being said the main precip shield is becoming ragged on the SW side and so any mixed precip is expected to be very light. That may fill in the main trof axis has yet to cross our longitude...but again accumulation of any precip after about 7 pm should be light. What is clear is that model usual...was too quick to warm the boundary layer. Our forecast was on the colder side but was still too warm in many locations...especially interior. While it remains in the teens at IZG...LEW...AUG...and WVL...model guidance would have had them all well into the 20s by now on their way to freezing. This is going to limit the amount of straight rain likely tonight...but given that our forecast was already fairly snowy across Wrn ME I see no need for additional headlines. High temps are likely to be around midnight for most locations. Needless to say a non-diurnal temp trend was used for this period. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/... Wed will be a bit of a tricky temp forecast...with highs perhaps early and temps falling or steady during the day. CAA will be increasing thru the I blended in mixed down temps to capture that trend. Regardless the colder air moving in will help to mix down some gusty winds. With gusts reaching 30 to 35 mph at times it will feel colder than the thermometer readings. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... Summary: A cold start...but then moderating temperatures with an extended period of generally dry weather expected through at least Monday of next week. High Impact Weather Potential: * At this time...winds appear too light for wind chill headlines Wednesday and Thursday nights...but both nights will feature very cold temperatures. --Pattern and Implications-- A look at early afternoon water vapor imagery over and surrounding North America reveals a progressive flow with no downstream blocking over the western Atlantic /+NAO/ and a robust jet across the central Pacific /+EPO/ with a strong vortex near the pole /+AO/. Overall this pattern would favor ample Pacific /ie mild/ influence across the lower 48...with the progressive flow yielding only brief bouts of cold air. This is what we have experienced recently...and will continue through the long term forecast period. The only bit of amplification in the flow at the moment is a trough/ridge pair over the Gulf of Alaska that will initially help drive another bout of cold air into the northeast to begin the forecast period. Beyond this...deterministic and ensemble guidance is in good agreement that a relatively zonal flow pattern will continue through the remainder of the long term forecast. After the initial cold surge...this spells an extended period of generally dry weather with temperatures moderating to warmer than normal values for this time of year /in agreement with CPC 6-10 day outlook/. --Daily Details-- Wednesday night - Friday: Very large high pressure center will reside across the central United States through this period... pushing a -2 to -3 sigma airmass /T8s/ into the northeast. Thus...another relatively dry and cold period is expected with temperatures below normal. Outside of some mountain snow showers to open the period precipitation is expected. T9s in the mid minus teens Thursday will moderate a few degrees on Friday. This will result in highs on Thursday only in the single digits in the mountains with teens and lower 20s to the south...with highs warming 5-8F on Friday. Undercut model consensus temperatures both Wednesday and Thursday nights...following closer to colder statistical guidance values. On Thursday night this will result in lows falling well below -10 in the mountains /likely a few readings below -20/...with single digits above and below zero to the south of this. Saturday - Monday: High pressure settles into the southeastern United States during this period...with return flow bringing moderating temperatures aloft with a resulting moderating trend in our temperatures. Given the sprawling high to our south...and little in the way of shortwave energy to our north...the quiet weather will continue...with temperatures moving back above seasonal norms. The only precipitation potential will come in the form of snow showers in the mountains given upslope westerly flow...but significant accumulations are not expected. By Sunday...the moderating temperature trend will equate to highs in the upper 30s in the mountains with 40s to the south. Tuesday: By the end of this forecast period next Monday Night- Tuesday there is modest guidance agreement that a cutoff low over the southwestern states will eject north and east with the potential for a precipitation event in our area. Too early to think about details at this range...but the warm antecedent temperatures suggests that PTYPE may very well be in question. Ensemble precipitation probabilities at this range also suggest that significant precipitation amounts />0.5" liquid/ are unlikely...but we/ll watch this period as this forecast period becomes clearer. && .AVIATION /03Z WEDNESDAY THROUGH SUNDAY/... Short Term...Widespread LIFR in SN this hour...with some IFR where precip has changed to RASN. That will continue into the evening when rapid scattering out low clouds is expected from SW to NE as a front moves in. I do not expect MVFR CIGs to linger long before things go VFR late tonight. HIE will be the exception where downsloping winds will keep mainly MVFR conditions thru this evening...then upsloping winds do the same late tonight. Long Term... Mountain snow showers may bring restrictions to HIE Wednesday night. Otherwise, VFR conditions should dominate the Thursday-Sunday period. && .MARINE... Short Term...Winds will continue to increase ahead of low pressure lifting thru this evening. Gale warning remain for the outer waters and SCAs in the bays. CAA Wed will allow stronger wind gusts to mix down during the afternoon. A period of offshore gales is possible...again outside the bays. Long Term... Lingering SCA winds/waves through Thursday with quiet conditions Thursday night into Friday before strengthening westerly winds bring the potential for renewed SCAs Friday night into Saturday. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...Winter Weather Advisory until midnight EST tonight for MEZ007>009-012>014-019>021-024-025. NH...Winter Weather Advisory until midnight EST tonight for NHZ001. MARINE...Small Craft Advisory until 11 AM EST Wednesday for ANZ150>154. && $$ SYNOPSIS...Arnott NEAR TERM...Cempa/Legro SHORT TERM...Legro LONG TERM...Arnott AVIATION...Arnott/Legro MARINE...Arnott/Legro
Area Forecast Discussion
National Weather Service Medford OR
800 PM PST Tue Feb 18 2020 .DISCUSSION...19/00Z NAM in. 19/00Z GFS in through 69hr. Clear skies prevail across the Medford CWA this evening with dry easterly low level flow. The dry air and relatively cold air mass in place will make for a cold night, and a freeze warning is in effect along the north coast. The area will warm up quite a bit after the cold morning, and afternoon temperatures will be cool to mild. This is a typical pattern for low level offshore flow over the area, with a long wave ridge offshore flopping over an upper trough to the south. It will end tomorrow as the trough moves out and the ridge axis moves onshore, bringing southerly flow aloft to the area ahead of the upstream trough. So, expect clear skies to continue through tonight, but sometime later tonight into Wednesday, winds near the coast will turn southerly, and this will eventually allow low clouds to surge north along the coast. It will take a while for them to get to the CWA as there is nothing out there now...usually they lurk around Cape Mendocino before making the northward dash. The 19/00Z NAM boundary layer RH fields suggest that the stratus surge will reach the Brookings area sometime Wednesday evening. The RAP doesn`t go out far enough, but extrapolating that output also suggests a Wednesday evening arrival. Inland areas will remain clear for the next several days, except for scattered high clouds and patchy late night into early morning low clouds. Extended discussion from the Tuesday afternoon AFD...Fri 21 Feb through Tue 25 Feb 2020. A fairly weak upper trough will move through our forecast area Friday with a closed low moving into southern California Friday night and then Arizona by Saturday. Since the air mass preceding this trough is very dry, and the closed low is expected to move in far enough to our south, we are not expecting any precipitation during this time period. We`ll see varying amounts of mid and high clouds, but also some sunshine and temperatures near or a little above normal levels. Mornings will still be chilly, though less so compared to earlier in the week, especially east of the Cascades. The next system we`re watching is a short wave expected to move quickly east-southeastward from the Gulf of Alaska and then move onshore into the PacNW late Saturday night into Sunday. The latest trend in the guidance has been for less digging of this trough. The GFS and GEFS ensemble members have been deeper and colder, while the ECMWF and its ensembles have been more progressive and not as cold. If the trend is correct, it would ultimately result in a less cold, wet solution. But, since it`s still pretty far out, we`ll still need to iron out the details. Still expect a pretty good cold front to move through with snow levels rapidly lowering from around 5000 feet down to 1500-2500 feet behind it by Monday morning. By that time, however, most of the precipitation will have ended or only remain in the mountains. An upper ridge will build offshore Monday, so coverage of showers should diminish/end with drier air moving in Monday night/Tuesday. -Spilde && .AVIATION...For the 19/00Z TAF Cycle...VFR is expected to prevail nearly everywhere for the TAF Cycle across southern Oregon and northern California. The exceptions to this are in the Umpqua Valley as well as the northern portion of the Illinois Valley this morning. The low clouds will dissipate by late afternoon bringing VFR to these areas for a few hours. Freezing Fog and low CIGS will return to the Umpqua Basin tonight including at KRBG before lifting tomorrow. Additionally, guidance is suggesting reduced VSBYS and lower CIGS with a coastally trapped wind reversal developing overnight along the Northern California Coast and spreading northward up to Gold Beach by the end of the TAF period. -Schaaf && .MARINE...Updated 730 PM PST Tuesday, 18 Feb 2020...Gusty north winds and steep wind driven seas will gradually subside from north to south across the waters tonight through Wednesday morning. Relatively calm conditions under high pressure are expected Wednesday through the remainder of the week. More active weather is possible over the weekend in the form of a frontal system and larger long-period swell arriving Sunday. Latest forecast models have trended later and somewhat weaker with the arrival of the front. Swell is still expected to be large though, at 18 to 20 feet with 15 second period. -BPN/Keene && .MFR WATCHES/WARNINGS/ADVISORIES... OR...Freeze Warning from 11 PM this evening to 9 AM PST Wednesday for ORZ021. CA...None. Pacific Coastal Waters...Small Craft Advisory until 4 AM PST Wednesday for PZZ356-376. Small Craft Advisory until 10 PM PST this evening for PZZ350-370. $$ 15/15/03
Area Forecast Discussion
National Weather Service Marquette MI
647 PM EST Tue Feb 18 2020 .SHORT TERM...(This evening through Wednesday) Issued at 308 PM EST TUE FEB 18 2020 MSAS analysis shows a 1000 mb surface low near the Ontario/Quebec border this afternoon continuing to deepen as it moves away from the area. NW wind behind it has been gusty at times due to the combination of isallobaric winds from pressure rises as high as 6 mb/3 hr at times as steep surface lapse rates due to CAA aloft. Have seen gusts into the 30+ mph range even well inland with 40+ mph gusts along the Lake Superior shoreline. Expect these winds to subside slightly in the next few hours before picking back up in the about 00z-04z time frame when the next mid-level short wave on the leading edge of the Arctic air aloft drops southeastward across Lake Superior. The NAM and RAP indicate pressure rises once again approaching 6 mb/3 hr in this time period and with 30-35 kt winds as low as 900 mb in model soundings, should have no problem mixing down 30+ mph gusts again this evening. Therefore, manually inflated winds and gusts in the grids during this period before trending back towards the CONSRaw after 06z. With this cold NW flow the other main story will be lake-effect snow. LES is already ongoing over much of the NW wind snow belts but currently is mostly light - except for some heavier bands over the Keweenaw that have reduced vis at CMX to around 1/2 mile at times. Expect that these Keweenaw/western U.P. bands will relax a bit after midnight once moisture becomes shallower in the subsidence region behind the aforementioned short wave. Additional snow amounts out west of about 1-3" did not warrant a headline but the snow and blowing snow combination justified an SPS that runs through 05z to capture the period of strongest snow and gustiest winds. For the eastern half of the NW wind snow belts, the longer fetch will allow heavier snow bands to persist longer. Models continue to focus on one or two long axis convergence bands developing over eastern Lake Superior and pushing onshore near Grand Marais this evening before gradually shifting east through Luce County overnight and into Wednesday morning. This big band looks fairly transient, which will cut down on snow totals somewhat, but with such deep moisture and impressive lake-based instability we`ll still be looking at several inches of snow in these areas. Therefore have issued a Winter Weather Advisory for the normal cluster of Alger, Luce, and northern Schoolcraft counties through 00z Thursday. In addition to the new snowfall, blowing and drifting snow will continue to be a concern in these areas, especially this evening during the window of peak winds but really all the way through the day Wednesday. Wednesday morning temps should be nice and frosty with subzero reading likely over the interior west, but hedged towards the CONSRaw over anything statistical since temps are usually handled better by raw models when there are lake-effect clouds and gusty winds keeping the PBL mixed. Therefore wind chills only drop to as low as -20, and only briefly, so despite the cold no wind chill headlines will be needed. Temps tomorrow really won`t climb much over their morning lows, with highs only expected to reach the upper single digits west and mid teens east. .LONG TERM...(Wednesday night through Tuesday) Issued at 212 PM EST TUE FEB 18 2020 Upper air pattern consists of a 500 mb ridge in the western U.S. with a broad trough from the plains across the eastern U.S. 00z Thu. The ridge moves into the Rockies 00z Fri and into the plains 00z Sat. Fairly quiet weather this forecast period with lake effect snow ending Wed night. Overall, did not make too many changes to the going forecast. In the extended, the GFS and ECMWF show a broad 500 mb ridge across the southern plains with a trough off the east coast and another over southern CA and Baja CA 12z Sat. Upper flow along the Canadian/U.S. border is zonal on Sat. Upper troughing moves into the upper Great Lakes 12z Sun. Troughing then moves into the northern Rockies 12z Mon and into the central plains 12z Tue. Above normal temperatures will occur for this forecast period. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 638 PM EST TUE FEB 18 2020 LES ongoing this evening within the WNW wind belt regions will continue overnight, with some signs of partial clearing tomorrow. KCMX will bear the brunt of the worst of the snow bands that have set up, with improvement expected as the night progresses. Blowing snow will also hinder visibilities, with winds slackening slightly late tonight through the remainder of this TAF period. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 429 PM EST TUE FEB 18 2020 Two gale events will occur for this forecast period. The first is happening into this evening across eastern Lake Superior with a low pressure system off to the east. Heavy freezing spray will also continue across the lake through Thu. Next gale event with southwest gales up to 40 knots looks likely Thu afternoon into Fri. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... Winter Weather Advisory until 7 PM EST Wednesday for MIZ006-007- 085. Lake Superior... Heavy Freezing Spray Warning until 7 AM EST /6 AM CST/ Thursday for LSZ162-240>251-263>267. Gale Warning until 1 AM EST Wednesday for LSZ249>251-266-267. Lake Michigan... None. && $$ SHORT TERM...RJC LONG TERM...07 AVIATION...lg MARINE...07
Area Forecast Discussion
National Weather Service Pueblo CO
817 PM MST Tue Feb 18 2020 .UPDATE... Issued at 759 PM MST Tue Feb 18 2020 Updated forecast based on current trends. Areas of dense fog continue up in El Paso county per obs and CDOT cams. Also we have had light continuous freezing drizzle down here in Pueblo for the last few hours and have added freezing precip to the gridds for most of the greater I-25 corridor region. Quick glimpse of the new NAM and 36 hour HRRR shows brunt of precip tomorrow evening will be from the EL Paso/Pueblo county lines southward. Likewise see no need to change current hilites. /Hodanish UPDATE Issued at 553 PM MST Tue Feb 18 2020 Based on CDOT web cams and obs, along with fcst soundings, have issued a dense fog advisory for all of El Paso county. /Hodanish UPDATE Issued at 503 PM MST Tue Feb 18 2020 Based on fcst soundings, there is probably a good chance we are going to see areas of dense fog up in El Paso county this evening into tomorrow morning, especially in N El Paso county. KCOS has already dropped to 1/2sm FZFG for a short period, and are now up to 2sm. KFLY and KCWM are currently at or below 1/4 sm FZFG. If these trends continue, will issue a Dense Fog Advisory for the region in later updates. /Hodanish && .SHORT TERM...(This evening through Wednesday) Issued at 246 PM MST Tue Feb 18 2020 ...Cool and Unsettled Weather Continues... Current water vapor imagery and upper air analysis is indicating moderate to strong westerly flow continuing across the Rockies, with at broad upper trough digging across the Intermountain West at this time. Water vapor imagery is also indicating tail end of and embedded shortwave lifting out across the High Plains with another embedded wave translating across the Northern Great Basin and yet another translating across the Desert Southwest at this time. Tonight...Some lingering light snow/flurries can be expected tonight across the southeast Plains, especially in the Pikes Peak region, with continued mid level waa/upglide and moist southerly low level upslope impinging along the higher terrain. This will keep flurries ongoing across the Pikes Peak region with areas of fog expected to develop this evening and persist through through early Thursday morning. Model soundings are indicating moisture aloft shallowing out through the overnight hours, leading to the potential for light freezing drizzle, though will let the evening shift continue to evaluate the need for any winter weather highlights if light icing develops. Any additional snowfall is expected to be light and less than an inch. For tomorrow...Embedded energy continues to translate across the Rockies, with moisture and lift increasing across area through the day. In addition, another surge of cool air will move across eastern Colorado through the morning, with breezy north to northeast winds of 15-25 mph developing through the late morning and afternoon. With that said, there looks to be a brief break in precipitation across the area early Wednesday, though will see snow developing across the higher terrain through the late morning and afternoon, especially the along the Palmer Dvd and Southern mountains and immediate adjacent plains, with favored northeast low level flow. Snow accumulations through late tomorrow afternoon will be generally light, 1 to 3 inches, though with widespread snow continuing through the the evening, the Wednesday afternoon/evening commute will likely be affected. .LONG TERM...(Wednesday night through Tuesday) Issued at 246 PM MST Tue Feb 18 2020 Snowfall will spread eastward from the mountains and I-25 corridor onto the plains Wed evening, as post frontal upslope flow deepens and upper wave drops into northern Colorado. East slopes of the Sangres/Wets look most favored for heavier snow given moderate low/mid level upslope component, and with lack of strong nly downslope initially, Arkansas Valley in Fremont/Pueblo counties could see a window for heavier snow Wed evening. Forcing is slightly weaker farther east on the plains, though longer duration of snowfall will lead to at least modest accums by Wed morning. Snow ends quickly Thu morning as low/mid level flow weaken and upper trough slides east. Overall, expect 4-9 inches eastern mountains, 3-6 srn I-25 corridor and through Fremont county, perhaps slightly higher Walsenburg/Colorado City areas. Two to five inch range should catch most of the plains, with highest amounts likely south of the Arkansas River. Will hoist winter weather advisory for all the above areas beginning Wed afternoon along and west of I-25, then spreading east onto the plains after 00z. Mountains and interior valleys will see snow, but only light accumulations, while Colorado Springs will see an inch or two, with 2-4 in Teller County. Clearing but still cold weather expected Thu, then warmer Friday as brief upper ridge builds. Southern stream system then lifts out of the swrn U.S. Saturday and across Colorado Saturday night, bringing another round of moderate to heavy snow to the mountains before ending Sunday morning. Lower elevations will see precip as well, though rather warm low levels may lead to at least some rain initially Sat evening, especially across the eastern plains. System lifts out into the plains Sun, with rather mild and dry conditions Sun into Mon, before cold front races through the area late Mon and next upper trough slides southward through the Rockies. This system looks colder than the one over the weekend, though impacts still uncertain as upper low may close off too far north and east to bring heavy snow to the region. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 246 PM MST Tue Feb 18 2020 IFR/LIFR conditions expected at COS through at least 14Z with moist southerly low level upslope flow keeping flurries ongoing, as well as developing fog at the terminal through the evening and overnight hours. Low level flow goes more north to northeast aft 14Z, with MVFR and VFR conditions expected through the late morning and early afternoon. Another surge of cool air will move across the area, with breezy north to northeast winds of 15-20kts expected to develop aft 18Z, with showers in the VC of the terminal through the late afternoon. MVFR and IFR conditions expected at PUB with moist easterly flow keeping cigs low with patchy fog possible through at least 14Z. Low level flow goes more north to northeast aft 14Z, with MVFR and VFR conditions expected through the late morning and early afternoon. Another surge of cool air will move across the area, with breezy north to northeast winds of 15-20kts expected to develop aft 18Z, with showers in the VC of the terminal through the late afternoon. ALS will remain VFR over the next 24 hours with breezy westerly winds of 10-20kts developing tomorrow afternoon. && .PUB WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 5 PM Wednesday to 5 AM MST Thursday for COZ089-093>099. Winter Weather Advisory from 2 PM Wednesday to 5 AM MST Thursday for COZ072>080-083-086>088. Dense Fog Advisory until 8 AM MST Wednesday for COZ084-085. && $$ UPDATE...HODANISH SHORT TERM...MW LONG TERM...PETERSEN AVIATION...MW