Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/29/18

Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
857 PM EST Sun Jan 28 2018 .UPDATE... Radar returns have slowly been increasing across SW Lower Mi over the last hour. There is still a good deal of dry air in the column, thus there have been no reports of snow in the sfc obs over the west side of the state just yet. As the larger scale forcing increases tonight, there will be a notable increase in ascent along the 280-290 deg isentropic surfaces, focused across Se Mi between 08Z and 16Z Mon. A narrow plume of moisture (2-3 g/kg specific humidities) will be transported into the mid level frontal feature. This combined with steepening mid level lapse rates and ascent focused within the dendritic growth layer will support accumulating snow late tonight into Monday. Recent hi res solutions are suggesting the forcing will be a littler farther up the frontal slope late tonight into early Mon morning, impacting locations from the far northern Detroit suburbs possibly up to Saginaw. Will therefore update to increase pops and snowfall accums across the north. Model solutions are also trending stronger with the trailing mid level deformation as the system exits east on Monday. This suggests a little better snowfall across the eastern half of the forecast area, possibly into Monday afternoon. For this reason, an update will be issued to increase pops on Monday and bump snow accums upward slightly from metro Detroit up through Port Huron. Overall, snowfall totals from midnight tonight through early Mon afternoon are still expected to fall in the 1 to 2 inch range, with lessor amounts across the Saginaw Valley and northern thumb. There is some concern for some locally higher amounts wherever a pivot point in the mid level frontal forcing sets up. At this point, this looks to be somewhere between Pontiac/Howell and Flint/Owosso. && .PREV DISCUSSION... Issued at 549 PM EST Sun Jan 28 2018 AVIATION... The region of light snow now over southeast Wisconsin will track into Se Mi late this evening and persist through a good portion of Monday morning. There will be an intensification in the larger scale forcing driving this snow late tonight (after 07 or 08Z), with the forcing persisting through daybreak. The snow is then forecast to slowly decrease as it slides off to the east late Mon morning/early Mon afternoon. Recent model guidance with some support by current radar trends are suggesting the forcing may extend a little farther north toward FNT. Total snow for the 12-hour period from midnight through noon Monday may reach 2 inches at PTK and FNT, with lessor amounts north toward MBS. For DTW...Current indications suggest the higher intensity snow will develop north of metro tonight, possibly not extending across the airport until 10 or 11Z. The snow will then persist through the morning before gradually tapering off during the afternoon. Peak intensity of the snow is expected in the 11 to 15Z time period. Up to an inch total accumulation is forecast. /DTW THRESHOLD PROBABILITIES... * High in ceilings below 5000 ft overnight through Mon afternoon. * High in precip type being all snow tonight and Monday. PREV DISCUSSION... Issued at 246 PM EST Sun Jan 28 2018 Discussion... Weak mid level low pressure associated with shortwave shearing out across the central Great Lakes will basically provide a pivot point for stronger dynamics sweeping into the area with strong shortwave that came onshore over British Columbia late Saturday and has since dug sharply into the central Great Plains into base of mean upper trough over the eastern CONUS. This feature, and its interaction with the aforementioned lead shortwave, is depicted very well on low and mid level GOES16 water vapor imagery. It is also most pronounced near the 400 mb level in model forecasts. Most notable is the 80-100 knot jet streak around this lower level that will be reaching the base of mean upper trough this afternoon and evening and then lift up its east side into Monday. Height falls associated with this system will lead to weak cyclogenesis over the Ohio Valley with a well defined inverted low level trough extending back to weakness associated with lead system over Lake Michigan and SW lower Michigan. The interaction of these systems basically leads to notably stronger low-mid level forcing than what previous model solutions suggested which will extend from this evening into Monday morning. As noted in the previous discussion, forecast soundings remain strong in the depiction of supersaturation with respect to ice up to the low level (now nearer 10kft -vs- 8kft from 00z model cycle). This encompasses a majority of the -10C to -20C layer, and with lift in this region also notably stronger, anticipate slightly higher snowfall totals over parts of the region (on the order of an inch or two). Recent HRRR runs suggest best forcing, and most widespread light snow accumulation, will set up between I-96/I-696 and I-69 with RAP focused just a bit further north than that. Will adjust snowfall forecast to this basic idea with sub-inch totals on either side. At this time, upper level pattern appears progressive enough to shift this deepening system east of area by midday Monday and allow area to dodge a period of deformation snowfall as central plains wave lifts up east side of upper trough. If there remains a wild card in this scenario, deformation positioned a bit further west/northwest into area would be something to watch. Much colder weather settled back into area in the wake of this system as NOAM upper trough amplifies and the first in a series of arctic air masses dives south/southeast into the region. This colder airmass will lead to high temperatures in the 20s early next this upcoming week with lows in the teens (and perhaps down to around 10 above for some locations early Tuesday morning). An approaching upper-level trough with embedded shortwaves and an associated surface low pressure clipper system will bring the chance for precipitation throughout Wednesday afternoon and evening. The center of the clipper system will stay well north of SE MI, traveling east across the southern Canadian provinces throughout Wednesday, however, the low will transport enough moisture from the south and will produce enough forcing to bring precipitation chances to MI. The GFS/NAM/GEM produce a swath of precipitation that moves NW to SE through the Wed 18Z to Thu 06Z time frame, while the ECMWF run continues to restrict precipitation chances north of the CWA, with slight chances to see snow across the thumb. If precipitation does pan out, precipitation type remains to be the second forecasting challenge. Top-down methodology produce a rain to wintry mix solution for the Metro region, with a wintry mix to snow solution possible closer to Flint and Tri-Cities, with the thumb having the best chance to see purely snow. Upper-level troughing will amplify Thursday into Friday as a strong cold front starts to move in across Michigan. This will cause winds to shift from the west to the northwest and in turn take Thursday forecasted highs in the lower 30s down to the low to mid 20s for a high by Friday. Holding off on putting lake-effect chances across SE MI for now, but it is certainly possible with the colder W/NW air funneling over the relatively warm lake that we will be able to produce lake effect snow bands that reach the CWA. Lastly, long range models are starting to resolve a low pressure system that will bring the potential to see snow late Saturday through Sunday across Michigan. MARINE... Light northerly winds becoming northeast 10 to 15 knots over Lake Huron tonight will persist tomorrow, generating waves of 4 feet or greater over the southern lake Huron basin. There higher waves will persist into Tuesday, as northerly winds around 15 knots persist. A quick flip of winds from northerly to southerly will then occur Tuesday night into Wednesday ahead of the next low pressure system. This strong low passing through Ontario will bring the potential for Gale force winds over much of the open waters of Lake Huron on Wednesday. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ UPDATE.......SC AVIATION.....SC DISCUSSION...DG/AM MARINE.......SF You can obtain your latest National Weather Service forecasts online at
Area Forecast Discussion
National Weather Service Green Bay WI
546 PM CST Sun Jan 28 2018 Updated aviation portion for 00Z TAF issuance .SHORT TERM...Tonight and Monday Issued at 258 PM CST Sun Jan 28 2018 The latest RAP analysis and satellite/radar imagery show a compact shortwave exiting southeast WI early this afternoon. Light snow showers should also depart east-central WI over the next hour or two. Meanwhile, cold advection is occurring behind a diffuse cold front positioned over northern WI. Scattered snow showers have been falling for most of the day north of highway 8, and flurries elsewhere. Think these flurries will persist through around sunset. Though there are some breaks, mostly cloudy conditions prevail from northern Minnesota to northern Illinois. As high pressure over the northern Plains moves towards the region over the next 24 hours, light snow and cloud trends are the main the forecast concerns. Tonight...Flattened upper troughing will remain in place across the western Great Lakes. Enhanced moisture along low level trough will gradually shift southeast through the evening and exit overnight. With light north flow off Lake Superior, will therefore expect mostly cloudy/overcast conditions to persist through the evening, before some breaks open up overnight. Some lake effect snow showers will also graze the NE WI shoreline into the overnight. Trajectories do not favor much accumulations, as bands should remain mostly offshore. Temps will be colder tonight, and range from near zero at Land O Lakes to the middle teens over the southern Fox Valley. Monday...Surface high pressure will be gradually building across the northern Mississippi Valley and into the western Great Lakes. Slow clearing will continue to take place during the morning with more clouds lingering over central and north-central WI than further east. May see a secondary surge of low clouds southeast in the afternoon as weak shortwave energy arrives from southeast Saskatchewan. But progged soundings suggest that clouds will not be deep enough for snow. Colder highs in the mid teens north to mid 20s south. .LONG TERM...Monday Night Through Sunday Issued at 258 PM CST Sun Jan 28 2018 Northwest upper flow will produce dry and seasonable weather Monday night through Tuesday. An upper trough swings through the Great Lakes Tuesday night and early Wednesday. Very little moisture is available, but strong low level warm advection and decent upper dynamics suggest that an inch or two of snow may fall across the north with an inch or less elsewhere. Much colder air will follow for the remainder of the week, with the potential for wind chill advisories Thursday and Friday nights across at least central and northcentral Wisconsin. An inverted trough is forecast to form from eastern Colorado to the northern Ohio Valley Friday night and Saturday. Some light snow is likely north of the trough, but the latest model runs are further south with this feature, so snowfall here should be light. && .AVIATION...for 00Z TAF Issuance Issued at 536 PM CST Sun Jan 28 2018 Light snow in east central WI and flurries elsewhere will taper off this evening. MVFR to low end VFR ceilings will likely persist through late tonight, followed by partial clearing as weak high pressure arrives. Most of the region will see BKN mid to high level clouds on Monday, through stratocumulus may linger over parts of northern WI. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM.....MPC LONG TERM......RDM AVIATION.......Kieckbusch
Area Forecast Discussion...Updated
National Weather Service Saint Louis MO
908 PM CST Sun Jan 28 2018 .UPDATE... Issued at 907 PM CST Sun Jan 28 2018 Regional radars are showing light precipitation moving east across northern Missouri associated with weak shortwave trough. 00Z upper air analysis indicated that this system is working with limited moisture, so there will be some sublimation as the snow falls through the atmosphere. In addition, the RAP is showing weakening ascent as the shortwave trough moves east across Missouri and Illinois tonight. So will maintain low PoPs through the overnight hours with any snow accumulations staying below a half inch. Low temperatures still look on track to fall into the 20s by morning. Britt && .SHORT TERM... (Through Late Monday Afternoon) Issued at 259 PM CST Sun Jan 28 2018 Upper level shortwave to drop southeast through region. So clipper system to bring in a chance of light snow tonight. Each successive model run has been a bit drier. For now kept low chance pops and accumulations still will be hit and miss. So anywhere from a dusting to a couple of tenths of an inch of snow is possible before daybreak on Monday. With colder air filtering in behind arctic cold front, highs will struggle to rise on Monday despite clearing skies. Will have highs only in the 30s. Byrd .LONG TERM... (Monday Night through Next Sunday) Issued at 259 PM CST Sun Jan 28 2018 Surface ridge to build in Monday night with clear skies and light winds. So lows will dip down into the 15 to 20 degree range. By Tuesday, surface ridge begins to move off to the east allowing southerly winds to return once again. Temps to moderate through mid week with highs by Wednesday back in the upper 40s to upper 50s. Beyond that, extended models still have a cold front slide through region beginning late Wednesday afternoon and into Wednesday night. Low level moisture and dynamics will be limited, so it will be a dry frontal passage. Broad based upper TROF still to setup over region for last half of work week, but with a stronger ridge at surface building in. The chances of precipitation with an upper level shortwave moving through on Thursday is looking less and less likely, with better chances further south, closer to frontal boundary that will have moved through our area Wednesday night. 12z GFS is now completely dry for our area, while 12z ECMWF still has some qpf for areas south of I70. Even the ensembles only have a few members with pcpn over area during this period. Blend came in trending lower with pops which looks reasonable. So backed off mention in social media products as it is looking less and less likely to snow substantially. Beyond Thursday, surface ridge in place through Friday before moving off to our east for the weekend. Extended models hinting at another system moving through region Saturday night/Sunday, but definite differences in timing and strength among the models. So will need to keep eye on future model runs. For now have just rain changing to snow for the last half of next weekend. Byrd && .AVIATION... (For the 00z TAFs through 00z Monday Evening) Issued at 606 PM CST Sun Jan 28 2018 A weak storm system will move across the area tonight bringing a chance of light rain or snow. Visibilities in the snow are expected to stay VFR or MVFR. Any snow accumulations are expected to be less than half of an inch. Some MVFR ceilings are expected late tonight into Monday morning. Then dry and VFR conditions are expected at the terminals after 18Z. Winds will remain out of the north to northwest. SPECIFICS FOR KSTL: A weak storm system will move across the terminal tonight bringing a chance of light snow between 06-10Z. Visibilities in the snow are expected to stay VFR or MVFR. Any snow accumulations are expected to be less than half of an inch. MVFR ceilings are expected late tonight into midday Monday. Then dry and VFR conditions are expected at the terminal after 18Z. Winds will remain out of the north to northwest. Britt && .LSX WATCHES/WARNINGS/ADVISORIES... MO...None. IL...None. && $$ WFO LSX
Area Forecast Discussion
National Weather Service Blacksburg VA
715 PM EST Sun Jan 28 2018 .SYNOPSIS... A cold front will move slowly east across the area this evening, exiting the piedmont overnight. An Arctic front will cross the area later Monday into Monday night. Cold high pressure builds in with drier weather for the middle of next week. && .NEAR TERM /THROUGH MONDAY/... As of 215 PM EST Sunday... Surface front still remains on the northwest fringe of the area but should begin to edge east across the region this evening as shortwave energy to the southwest shears across ahead of the upstream Arctic front. This upstream boundary with the digging 5h trough looks to finally boot the axis of deep moisture ahead of the initial front east of the region late tonight or Monday morning. However low pressure developing off the southeast coast by early Monday may again tend to slow up exodus as models hint at a residual leftover deformation zone to the northwest lingering along the back of this surface wave. Otherwise appears another several hours of steadier showers/rain to persist through the evening with the heaviest along/east of the Blue Ridge as the wave aloft currently to the southwest shears through. Gradual drying to then take shape over the northwest this evening as the front starts to edge east. Thus keeping likelys northwest to categorical southeast half before seeing better drying at least aloft head east of the mountains after midnight per latest HRRR. This could spell another half inch of rain south and a tenth to a third north/west before tapering to spotty drizzle late. Cold advection filtering in may also catch some of the exiting moisture far northwest toward daybreak, but since slower only left in a mention. Kept lows on the warmer side of Mos given current trends and slowness of the boundary to head east later. Lots of uncertainty on Monday as the area slides in between the low offshore and ahead of the Arctic front still west of the mountains. Some solutions continue to try and hang back a lobe of shallow moisture across the region with low level moisture perhaps getting trapped in a leftover weakness across the far west as deepening north/northeast flow develops out east in the wake of the low. This could result in spotty light snow/rain west of the Blue Ridge into early afternoon with some patchy rain lingering east, but quite iffy and light if it occurs at all. Otherwise looks like mainly cloudy despite good drying aloft and even a drier boundary layer in the afternoon before precip ahead of the Arctic boundary arrives late with a rain/snow mix western ridges after sunset. Under weak cold advection, keeping highs in the middle of guidance which results in mostly 40s, except perhaps around 50 far south, and only in the 30s on the western ridges. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY NIGHT/... As of 200 PM EST Sunday... The arctic front with its surge of cold air will barrel into the region early Monday night. Good dynamic support from the upper jet and vigorous short wave energy will combine with good low level moisture with some influence from the Great Lakes to develop snow showers west of the Blue Ridge. Expect a couple of inches of accumulation at the preferred higher elevation locations along with some snow bands bringing localized accumulations a bit further to the east. There are also hints that the front will be able to couple with some lingering synoptic deformation to produce some snow east of the Ridge, possibly with some embedded mesoscale banding. All of this would impact the morning commute Tuesday east of the Ridge so a winter weather advisory may be needed if the situations continues as advertised in later model runs. Winds will be increasing significantly Monday night into Tuesday as the low level wind field amplifies and a well mixed boundary layer allows for good downward momentum transfer. Bufkit soundings also show a lowering inversion that will help squeeze the flow and generate strong, gusty winds. These winds will combine with the cold temperatures in the advancing arctic airmass to create single digit wind chill values west of the Blue Ridge by Tuesday morning. With the combination of strong gusty winds and a couple inches of snow, will issue a winter weather advisory for the higher elevations west of the Blue Ridge Monday evening into Tuesday morning. A more widespread wind advisory may also be needed for other locations with strong winds but less snow. Will see how the situation develops and allow later shifts flexibility to issue the necessary headlines. Snow showers will gradually diminish to lingering flurries west of the Ridge during the day on Tuesday as a large area of high pressure settles over the region and brings fair but chilly weather to the region through Wednesday. Wednesday morning looks to be the coldest point during this cold spell with temperatures generally in the teens with some single digits west of the Blue Ridge. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 200 PM EST Sunday... The progressive upper pattern will keep systems zipping along and allow for a brief break in the action through midweek with a trend for temperatures retuning at or above normal levels by Thursday. The next frontal system with developing low pressure will then begin to affect the region late Thursday into Friday. The latest guidance is not as enthusiastic with QPF as previous runs, but, there still appears to be enough associated cold air and precipitation to allow for some accumulating snow to develop later Thursday through Friday, though timing and location of any snow remains uncertain. Will be watching upcoming model runs closely to see how the situation develops. High pressure will then bring fair weather with below normal temperatures into next weekend before the next frontal system pushes precipitation into the region from the west on Sunday. && .AVIATION /00Z MONDAY THROUGH FRIDAY/... As of 700 PM EST Sunday... Poor aviation conditions expected through the TAF valid period, with potential for improvement across the Piedmont during the later portion of the TAF valid period, mainly after 16Z Monday. Ceilings and visibilities will remain mostly IFR-LIFR throughout the night in low clouds, fog, light rain, and drizzle. While the main synoptic wave is moving east of the area this evening, low pressure moving through the Southeast U.S. will spread rain back into the area during the night. A deformation zone will also bring rain back from the north/northeast later in the night across the New/Roanoke/and Shenandoah Valleys. When not raining, feel that drizzle and fog will be an issue, per most BUFKIT soundings from most models. HRRR really hits fog concerns early and continues throughout the night, which so do the NAM and GFS. A Dense Fog Advisory may be needed later. For now will issue an SPS concerning such. Worst conditions are along the Blue Ridge and western mountains where the ceilings are down on the ridge tops with 1/2SM or less visibility common in those areas. As drier air continues to work into the region from the north/northwest Monday afternoon, look for some improvement east of the Blue Ridge with MVFR-VFR possibly by mid or late afternoon. IFR improving to MVFR conditions will likely evolve across the western upslope areas. Winds will be mostly light and variable overnight, favoring a north to northeast direction in most areas with speeds 5kts or less at most sites. Winds will tend to back to the north- northwest with time Monday, but speeds will remain mostly 7kts or less. Medium confidence in ceilings and visibilities throughout the TAF valid period. Medium confidence in wind direction, high confidence in wind speed throughout the TAF valid period. Extended Discussion... Lingering upslope northwest flow in the mountains brings more MVFR/IFR clouds and scattered to numerous snow showers Monday night into Tuesday. Northwest winds will also increase behind the front Monday night and Tuesday with strong gusts possible. VFR then returns to all sites mid- week as high pressure builds in from the west. Increasing amounts of polar air will spread into the eastern U.S. during the later half of the week. Moisture will be limited, but a reinforcing surge of Arctic air will arrive late in the week and by next weekend. Each of these systems will be accompanied by some potential for winter precipitation, mainly in the form of snow as it appears right now. Periods of sub-VFR ceilings will certainly be possible throughout the week, with more lengthy periods of such across the western mountain and upslope areas. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...Winter Weather Advisory from 7 PM Monday to 10 AM EST Tuesday for VAZ007-009-015. NC...Winter Weather Advisory from 7 PM Monday to 10 AM EST Tuesday for NCZ001-018. WV...Winter Weather Advisory from 7 PM Monday to 10 AM EST Tuesday for WVZ042-043-508. && $$ SYNOPSIS...JH NEAR TERM...JH SHORT TERM...MBS LONG TERM...MBS AVIATION...JH/RAB
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
814 PM EST Sun Jan 28 2018 .UPDATE... Things have shaped up to be a very wet day across west central and southwest Florida. The area of low pressure is now located just off the west coast of Florida and will continue to track east over Florida for the next 12 hours. Some reporting stations and radar rainfall estimates are reporting anywhere from an inch of rain south of Tampa Bay to 1.5 - 2.5 inches of rain with some local areas approaching 3 inches. Rainfall amounts from Tampa Bay northward will begin to taper off in the next 2-3 hours, while over southwest Florida from Sarasota County southward will see increasing amounts of rain over the next 2-3 hours. As the area of low pressure and associated front moves off the east coast later tonight into early Monday morning, rain chances will continue to decrease by mid- morning on Monday, with all rain clearing the area by Monday afternoon. Even with the rainfall moving out, cloudy skies will be slow to clear out until late Monday into early Tuesday morning. I have made some adjustments to the POPs based on latest radar and HRRR guidance through the early morning hours. Will send out updated zones shortly. && .AVIATION... Moderate to heavy showers are streaming in from the gulf producing region wide MVFR conditions at all terminals. Over the next 6-9 hours, brief periods of IFR and LIFR can be expected in the heavier showers. A stray thunderstorm may be possible over the next hour, but will be so sporadic that I did not mention them in the TAF. Winds will remain generally less than 10 knots with some gusts near 15 knots in heavier showers. The majority of the inclement weather will have moved through the terminals by 14-16Z, but some lingering low clouds and BR will be possible through late morning. && .MARINE... The area of low pressure is continuing to push through the gulf coast waters with showers and a stray storm possible for the overnight hours. Sea fog will also continue to be possible over the coastal waters through the night as well. As the low moves eastward out of the area on Monday, gradual clearing conditions can be expected. High pressure behind the front settles into the southeastern states by midweek. Winds will be veering around to the north on Monday with likely small craft conditions possible by late Monday into early Tuesday morning and continuing until Wednesday. At that time, high pressure moves off the east coast allowing for the winds to veer easterly and decrease below advisory level. No other marine hazards expected through the period. && .Preliminary Point Temps/PoPs... TPA 65 72 49 63 / 80 40 0 0 FMY 66 76 53 68 / 70 50 10 0 GIF 65 74 48 64 / 90 50 10 0 SRQ 64 71 51 64 / 90 40 0 0 BKV 64 71 43 62 / 90 50 0 0 SPG 64 70 50 62 / 80 40 0 0 && .TBW WATCHES/WARNINGS/ADVISORIES... FL...None. Gulf waters...None. && $$ UPDATE/AVIATION/MARINE...74/Wynn UPPER AIR...27/Shiveley DECISION SUPPORT...05/Carlisle