Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 02/28/18

National Weather Service Kansas City/Pleasant Hill MO
630 PM CST Tue Feb 27 2018 .Discussion... Issued at 253 PM CST TUE FEB 27 2018 Large-scale upper low seen very well on water vapor imagery this afternoon, with strong southwest winds allowing for ample warm air advection further downstream across the Nation`s midsection. 70 degrees is currently being reported at MCI, the warmest temperature since December 4th! Meanwhile, cloud cover associated with shower activity across the Southern Plains is starting to lift north this afternoon, but fortunately not in time to prevent an otherwise stealer day temperature-wise across the lower Missouri Valley. Heading into tonight, expect cloud cover to increase, with showers and isolated storms gradually lifting north with time from southern Missouri. Quick look at several BUFKIT soundings reveals a few hundred joules of elevated CAPE rooted above the 850-hPa layer, so a few claps of thunder and flashes of lightning (especially south and east of KC) will be possible through the late evening and overnight hours. Latest high-res solutions to include the HRRR and NAMNest suggest precip will lift up towards the I-70 corridor before quickly shifting east as main cold front starts to sink south with time. As a result, northward extent of overnight precip remains in question right now, especially for northwest Missouri with these locations standing a lower chance of seeing much rainfall. In any event, limited instability and overall lack of forcing in general will curtail the severe weather threat from any convection that does impact the area. Shifting to tomorrow, available guidance suggests low clouds will hang around for a good portion of the morning and possibly into the afternoon hours, which should limit the diurnal heating cycle and instability development. Despite this, models still indicate a narrow sliver of instability will develop primarily east of Route 65 and south of Route 50 by late afternoon, which may be enough to support thunderstorm development Wednesday evening out in advance of the main cold front expected to move through tomorrow night. Instability will again be low so widespread severe weather is not expected at this time. Following FROPA, deformation band precip will overspread the area early Thursday which may lead to a wintry mix, especially north of KC. For now however, major impacts are not expected. Beyond this, high pressure will build into the region on Thursday with winds gradually decreasing through the afternoon. Southerly winds will quickly return to the region by late week which should lead to another warm up heading into the weekend with upper 50s possible both Saturday and Sunday. Next chance for precip set to arrive Sunday night/early Monday when the next cold front is slotted to move into the region. Severe chances look low at this point due to timing (early morning), but trends will be monitored. && .Aviation...(For the 00Z TAFS through 00Z Wednesday Evening) Issued at 605 PM CST TUE FEB 27 2018 Clouds have been steadily building into the area and are expected to continue to thicken and lower throughout the evening. Overnight, look for low-level stratus to build in, dropping ceilings, and most likely visbys along with it. Showers are anticipated to increase in coverage through the period, with some thunderstorms in the area possible tomorrow afternoon. Generally southerly winds tonight will become variable as a front approaches, transitioning to out of the north toward the end of the TAF period. && .EAX WATCHES/WARNINGS/ADVISORIES... KS...NONE. MO...NONE. && $$ Discussion...32 Aviation...lg
Area Forecast Discussion
National Weather Service Huntsville AL
901 PM CST Tue Feb 27 2018 .NEAR TERM...(Tonight) Issued at 900 PM CST Tue Feb 27 2018 Showers have moved towards the area a bit quicker than originally forecast and are currently located across northern MS. However, there is still a good deal of dry air to overcome, which is very apparent in the 00z BMX/OHX soundings and surface obs. Temps have remained on the warmer side with winds staying up and clouds moving in. Think that as rain begins to fall into the dry layer we`ll see some evaporative cooling and temps may tumble to the low to mid 50s based on current dewpoint depressions. They should remain there for much of night before gradually warming towards sunrise as winds become more southerly and the warm front moves over the area. Models with the exception of the 01z HRRR appear to be about 3-4 hours too slow with the onset but they all do narrow in on the warm front stalling just across border in TN. The result would be a gradient in precip with the overrunning showers continuing in TN and more isolated showers south of the front. Lapse rates and sounding profiles don`t support thunderstorm potential until near the warm front and have gradually introduced those into the forecast. PWATs near the front jump up to around 1.5 inches and could see some brief heavy downpours early Wednesday morning. Now any minor changes in the frontal position could be a longer duration of showers Wednesday morning a quicker end before the next batch arrives later in the day. Something we`ll be keeping an eye on. The rest of the forecast is in good shape. .SHORT TERM...(Wednesday through Thursday) Issued at 303 PM CST Tue Feb 27 2018 A very wet period continues Wednesday and Thursday with the potential for flash and areal flooding initially on Wednesday and eventually river flooding Thursday into the weekend. The aforementioned boundary is progged to stall across or just north of the WFO HUN forecast area. Generally, the ECMWF, GFS, Canadian, and some of the newer mesoscale guidance is trending this way. This scenario would result in a widespread heavy rainfall event of 2 to 4 inches, with higher amounts of 5 inches possible. The Canadian and ECMWF have trended even higher in their 12z runs, showing a few localized amounts up to 6" in far Northwest Alabama. The one outlier is the NAM which stalls the boundary further to the north across portions of Middle Tennessee. Should this play out, rainfall totals (and thus the flooding threat) will be much less. However, most trends (as mentioned) have honed in on this boundary stalling roughly along the Alabama/Tennessee state border and the heaviest rainfall occurring across Northwest Alabama and areas along and north of the Tennessee River. There may well be a sharp precipitation gradient, with portions of Marshall, Cullman, and DeKalb Counties likely seeing less rainfall (perhaps closer to 1.5 to 2"). Regardless, things are trending toward a widespread flooding event across much of the region. As one might imagine, parameters are very favorable for flooding and heavy rainfall as these showers and storms will be efficient rain producers. There will be a deep warm cloud layer, with some modest CAPE favorable for some organized, deeper convection at times. Additionally, PWATs will increase to around 1.5" Wednesday afternoon/night and into Thursday morning, around 300% above the norm. A low-level jet will enhance lift and shower/storm coverage during the Wednesday evening/night and a warm front will help to focus this activity, resulting in training. The best window (as alluded to earlier) will be Wednesday afternoon/evening through early Thursday morning in response to the low-level jet feature. A cold front will sweep across the region on Thursday, bringing an end to the precipitation from west to east by the afternoon. Even after the flash/areal flood threat has ended, river flooding will likely be an issue well into the weekend. In short, we`ll be dealing with these hydro issues (potentially) for awhile. .LONG TERM...(Thursday night through Monday) Issued at 303 PM CST Tue Feb 27 2018 The large upper low that is poised to bring heavy rainfall to the Tennessee Valley Wednesday/Thursday will slowly exit off the northeast US coastal waters Friday into Saturday. At the same time another strong Pacific system will be coming onshore across the northwest corner of the United States. Between these two notable systems, a rather high amplitude ridge will be building across the nation`s midsection. This feature will bring dry weather, generally clear skies and rather large diurnal temperature ranges in the Day 3-5 time period. Will trend toward the higher end of the guidance envelope for max temperatures during this period. Morning temperatures could be rather chilly (well relative to recent weeks) with patchy frost possible on Saturday morning. The ridge will begin to break down/slide east on Monday as the aforementioned west coast trough advances into the Plains. This will help drag a frontal system toward the Tennessee Valley. At this time, the front looks to be rather fast moving with a narrow window for rainfall from late Monday through early Tuesday. Low level moisture return with this system looks very meager so despite adequate upper level support expect primary a non convective rain event. The 12z guidance supports a faster clearing trend behind this system on Tuesday and will trend this direction with the afternoon package. However, the current forecast may even be on the slow side if this trend continues to hold with most of the day Tuesday being rain free. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 520 PM CST Tue Feb 27 2018 VFR conditions will continue through the evening hours before gradually dropping towards MVFR as showers spread into the area. Some lingering dry air may help to limit the onset of the showers and low clouds for an hour or so but expect cigs around 5,000ft initially. Then down to as low as 1,000-1,500ft by 12z Wednesday. An embedded thunderstorm is possible after midnight but confidence is too low to add these to the current TAF package. Could see vsbys drop down to 1SM at times under the heaviest showers, otherwise vsbys should stay around 3SM. Winds become gusty out of the S/SE during the day Wednesday with gusts of 15-20kts possible at times. The frontal boundary bringing these showers may stall either over the area or just to the north and result in continued moderate to possibly heavy rainfall through much of Wednesday and into Thursday. && .HYDROLOGY... Issued at 900 PM CST Tue Feb 27 2018 Various forecasts concerning some of the main streams that feed the Tennessee River, namely the Big Nance, Flint and Paint Rock rivers are forecast to rise in response to rainfall runoff during Wednesday and Thursday. Rainfall totals across the Tennessee Valley into Thursday should range between 2 and 4 inches, with locally higher amounts possible. The water levels in these rivers will exceed bankfull stage during Wednesday night and early Thursday, and likely rise above flood stage during Thursday and Friday. Other area rivers and streams will also rise to higher than normal levels. Water levels on the Tennessee River will also rise late this week, with river levels nearing or exceeding flood stage this weekend and possibly continuing into early next week. Those with activities in or near areas rivers and streams should stay abreast of the latest forecasts from the National Weather Service. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...Flood Watch from 6 AM CST Wednesday through Thursday afternoon for ALZ001>010-016. TN...Flood Watch from 6 AM CST Wednesday through Thursday afternoon for TNZ076-096-097. && $$ NEAR TERM...Stumpf SHORT TERM...AMP.24 LONG TERM...15 AVIATION...Stumpf HYDROLOGY...RSB For more information please visit our website at
Area Forecast Discussion
National Weather Service Louisville KY
955 PM EST Tue Feb 27 2018 .Forecast Update... Issued at 955 PM EST Tue Feb 27 2018 SREF and RAP are verifying well, and the GFS is decent, with the placement of the widespread rain over Arkansas and adjacent states this evening. These models support a southward leaning of the heaviest precipitation late tonight into Wednesday, with the highest QPF amounts over Tennessee. However, they also support a lesser, secondary maximum spreading from southern Indiana into northern Kentucky as isentropic lift and column moisture increase late tonight into Wednesday. 6hr FFG numbers are up around two inches and OHRFC forecasts don`t show much response on the rivers from the expected rainfall. Right now it looks like amounts from southern Indiana into northern Kentucky Wednesday morning look to be on the order of one-half to two-thirds of an inch. Thunder looks unlikely until perhaps a few rumbles Wednesday afternoon and evening. So, given this and after chatting with IND, will continue the current forecast without a headline north of the Flood Watch already out for southern Kentucky. However, will issue an SPS since we could still see some minor ponding in poor drainage areas, and the rain will be coming through during the morning rush. QPF numbers are actually not very impressive in southern Kentucky through Wednesday evening, but there is a large mass of rain taking shape upstream in area of strong moisture transport and 850mb theta- e ridging. There is a chance that heavier precipitation amounts could fall both north and south of the current watch, but after talking with JKL and considering the QPF that is expected Wednesday night, will keep the watch going. && .Short Term...(Tonight through Wednesday night) Issued at 245 PM EST Wed Feb 27 2018 ...More Flooding Possible Wednesday and Thursday... As of mid afternoon, clear skies and light winds were found across the lower Ohio Valley thanks to surface high pressure centered over the Commonwealth of Virginia. Nice late February temperatures as readings have warmed into the lower to middle 60s. The focus in the short term is on the rainfall forecast, totals, and potential impacts starting late tonight through Thursday as a couple rounds of showers and perhaps a thunderstorm cross through the region. First round of showers comes late tonight into early Wednesday on the nose of increasing 850 mb moisture transport. This will bring in higher PWATs on the order of 1 to 1.2 inches. While not record, it is anomalously high for late February. Onset is expected to be after midnight along/west of I-65 and closer to 4-6 am EST across the I-75 corridor. A look at the latest hi-res models show 2 possible areas of concentrated rainfall. The first, across south central Indiana and north central Kentucky, and the other across mid TN into southern KY. Lighter precipitation may fall in between and it`s possible there could be a gap across portions of central Kentucky. Through early Wednesday afternoon, between 1/4 and 1/2 of an inch of rain is expected broadly brushed across the area. There may be locally higher amounts up to 3/4 or even 1 inch across the north and south, but intense rainfall isn`t expected overnight into Wednesday morning. There will be a break in the rainfall Wednesday afternoon and evening for pretty much the entire area. Then as the surface low tracks to lower Michigan Wednesday night and Thursday, another round of showers and perhaps a thunderstorm will be possible. PWATs climb further to around 1.3 inches across much of central KY and southern IN. The heaviest axis of rain is expected to fall across southern Kentucky and along the KY/TN border. The 27.12z NAM continues to be a heavier and more northerly outlier with a swath of heavier rain impacting the extreme south-central KY counties. The last few frames of the hi-res ARW and NMM also show a northern band across parts of central Kentucky, so this is something will need to be watched. Rainfall Wednesday night and Thursday will total 3/4 to 1 inch, so total rainfall over the next 48-60 hours ranges from 1 to 1.5 inches across southern Indiana and north central Kentucky to 1.5 to 2 inches across southern Kentucky. With this in mind, and the antecedent conditions, high water, and swollen rivers still in place, a Flood Watch will be issued for the greatest risk area for flooding concerns across southern Kentucky for Wednesday and Thursday. This might need to be expanded northward into north central KY or even parts of southern IN if it looks like higher rainfall amounts will fall but the watch was placed where the greatest risk area is and confidence for flooding based on the highest rainfall totals forecast. && .Long Term...(Thursday through Tuesday) Issued at 245 PM EST Tue Feb 27 2018 Upper level ridging through the weekend will provide near normal temperatures for early March with highs in the 50s and lows in the 20s to 30s. By early next week, a strong storm system will move from the central Plains to the Upper Midwest, eventually pushing a cold front through the lower Ohio Valley in the Monday night and Tuesday time frame. Moisture return is not impressive (dewpoints only climb up to the mid/upper 40s) and the current timing (overnight / early Tues) really dampens instability potential, so stronger storms don`t look likely at this point. Nonetheless, a blended model approach puts in 60-70 percent chances during this period. && .Aviation...(00Z TAF Issuance) Issued at 637 PM EST Tue Feb 27 2018 We can expect a mostly quiet night with increasing mid and high clouds ahead of an approaching storm system. Borderline LLWS will develop late as winds increase off the surface ahead of that system. On Wednesday low pressure will cross Kansas and Missouri while a couple of upper level disturbances eject eastward out of the southern Plains. Showers will quickly become widespread early Wednesday morning and continue into early afternoon before coverage starts to decrease. Ceilings will go below VFR as the showers establish themselves, and will fall into IFR in the afternoon and evening as high 0-1km RH sweeps northward from the western Gulf of Mexico. && .Hydrology... Updated at 230 PM EST Tue Feb 27 2018 Many of the area rivers have crested and are now receding but still remain above flood stage. Rainfall amounts of 1 to 2 inches are possible Wednesday through Thursday evening across the region. For a complete listing with forecast hydrographs, please visit our website at: The forecast rainfall through Thursday is not expected to result in any new river flooding. However, it will slow the fall on some rivers and will likely result in minor rises on the flashier basins. Smaller creeks, streams, and rivers will be most at risk along with areal flooding of low lying areas. Many locations are still recovering from the recent heavy rainfall and while 2 days of drying helped, the soils remain very saturated and soft. With the antecedent conditions, river flooding, and saturated soils, a Flood Watch has been issued for parts of central Kentucky. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...Flood Watch from 7 AM EST /6 AM CST/ Wednesday through Thursday evening for KYZ053-054-062>067-071>078-081-082. && $$ Update...13 Short Term...ZT Long Term...ZT Aviation...13 Hydrology...ZT
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
612 PM CST Tue Feb 27 2018 .SHORT TERM...(This evening through Wednesday) Issued at 210 PM CST Tue Feb 27 2018 A cold front moved into far southern Minnesota this afternoon, with a weak surface low in south central Minnesota as of 2 pm. Temperatures this afternoon, and the effect of the snowpack and albedo, shows a sharp contrast along the Minnesota River Valley, vs. the Twin Cities Metro area, and more forested areas of east central Minnesota, and west central Wisconsin. Where the albedo is much higher due to the terrain/lack of vegetation in west central Minnesota, temperatures have only managed to rise into the low to mid 30s. Where the albedo is lower, like the Metro area and more trees in east central Minnesota, and west central Wisconsin, temperatures were in the 40s. The deeper snowpack across southeast Minnesota has also had a major impact on temperatures. Around Rochester, Winona and La Crosse, temperatures have managed to rise into the 50s this afternoon. The forecast tonight is based on a weak upslope flow (northeast winds) across southwest/west central Minnesota where fog/stratus is likely to form. Elsewhere, patchy fog is likely, especially considering the amount of melting this afternoon and the moist boundary layer. Wednesday afternoon will have a weak short wave moving across Minnesota by late in the day. Due to the weak short wave, and the lack of phasing from the southern jet stream, anything that develops will be light, and affect areas from south central Minnesota, northeast to west central Wisconsin. Wednesday afternoon temperatures will be cooler than today, but still above normal for late February. .LONG TERM...(Wednesday night through Tuesday) Issued at 230 PM CST Tue Feb 27 2018 The weak short wave will exit the Upper Midwest Wednesday night. Some residual sprinkles, flurries or freezing drizzle is possible along and east of this short wave, but most areas will remain dry. The extended period can be characterized as mild and uneventful through most of the upcoming weekend. This is mainly due to an upper ridge building across the Plains, and Upper Midwest. Plus, a strong and blocking ridge will remain centered across southern Greenland. Over the past several runs of both the EC/GFS, and their ensembles, indicated that the upper ridge will hold longer across the Upper Midwest for the first half of the weekend. Thus, precipitation chances have been lowered, especially Saturday, and most of Sunday. In addition, and due to the prolonged milder air moving northward as the upper ridge holds, the chance of more rain vs. snow is increasing for the onset of the precipitation Sunday. Once the upper ridge finally begins to break down over the Upper Midwest/Great Lakes region, does our weather begin to become more unsettled. There remains differences with both the EC/GFS by early next week on the strength of the storm system, but there is enough consistence that the milder air will be replace with much cooler conditions by Monday. The conflict between the mild air, and the cooler air mass, a strong storm system will likely form. It is too early to tell on how it will affect the Upper Midwest, but anytime there is a significant change in the air mass, a major storm is likely near the gradient. Please check back for further updates on the potential of a winter storm early next week. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 612 PM CST Tue Feb 27 2018 Like last night, we will likely see patches of dense fog develop in valleys and other low lying areas late tonight, though that will be dependent on trends in mid level clouds. HRRR and other high res models continue to highlight greatest fog potential out along the SD/MN border, then down the upper MN River Valley. Confidence in dense fog occurring at any of the terminals is pretty low, so soft played the fog potential with some prevailing MVFR vsbys. Question then for Wednesday turns to when does the stratus move in. Majority of the guidance says it really starts advancing NW out of IA/SE MN during the afternoon, so delayed arrival of MVFR several hours from the 18z TAF to get the timing in line with the LAV. KMSP...Like this morning, we will likely see reduced visibilities from 9z to 16z. For the most part, it will be a VFR haze, but we could see an MVFR vis around sunrise. For stratus Wednesday, went with a later LAV timing, though we could really see it set in at any point during the day when looking forecast soundings. /OUTLOOK FOR KMSP/ Thu...MVFR with -SN possible early. Wind NW 5-10 kts. Fri...VFR. Winds SE 5-10 kts. Sat...VFR. Winds SE 10-15 kts. && .MPX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. && $$ SHORT TERM...JLT LONG TERM...JLT AVIATION...MPG
Area Forecast Discussion
National Weather Service Marquette MI
719 PM EST Tue Feb 27 2018 .SHORT TERM...(This evening through Wednesday) Issued at 317 PM EST TUE FEB 27 2018 All the attention in the short term is on Fgen forced precip on the N side of a surface trough axis nosing into the region. Models have significantly increased QPF over the S-central to eastern U.P. and have followed that trend in the forecast. Low-mid level temps will be cooling dynamically as the precip develops, which will push the rain/snow line farther south to southern Menominee County. Where rain is expected, surface temps should be above freezing. Elsewhere, 0.5-1.0 inch of snow is forecast from Stephenson to Escanaba, Manistique, and Newberry. There is a possibility for greater amounts as the HRRR shows total QPF around 0.50 inches, but that seems overdone and definitely on the high side of guidance. Did not issue any headlines or SPSs given limited amounts. .LONG TERM...(Wednesday night through Tuesday) Issued at 317 PM EST TUE FEB 27 2018 Overall, through the extended the weather looks to remain fairly quiet across the Upper Great Lakes region. Zonal flow will break down towards the end of the work week as a lead shortwave tracks eastward across the central and eastern CONUS, allowing a deepening low pressure system to track across the southern Great Lakes on Thursday. Given the southern track of the system and models still showing most, if not all of the precipitation remaining south of the area, do not expect much if any precipitation to reach southern portions of Upper Michigan. We could see some light wintry precipitation off of Lake Superior as the system continues to move over the eastern Great Lakes region on Friday, but with 850mb temperatures being very marginal and high pressure quickly moving into the region any precipitation should remain light. For the up and coming weekend, we will be sandwiched in between two systems with upper-level ridging slowly moving eastward across the Upper Great Lakes region. As a result, high pressure will give way a pleasant weekend with mild conditions and dry weather. Cloud cover will be on the increase, along with winds, towards the end of the weekend into early next week as deep, longwave trough slowly ejects out across the Plains. This upper-level trough is progged to slowly track across the Upper Great Lakes region through early next week allowing for better chances for widespread precipitation and cooler temperatures. Precipitation type as this system tracks across the region will be highly dependent on the track of the system, which models continue to diverge on. Temperatures following the system will also depend on the strength and track of the system. If temperatures are able to cool down enough aloft to support any lake effect precipitation, it will depend highly on the ice coverage over Lake Superior. && .AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon) Issued at 1238 PM EST TUE FEB 27 2018 VFR conditions are expected at all TAF sites. However, there is potential for lowered conditions at KSAW late this evening and early tonight as an area of snow and showers passes just to the SE. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 317 PM EST TUE FEB 27 2018 Today through the end of the week, winds are expected to remain below 25 knots. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...Titus LONG TERM...Ritzman AVIATION...Titus MARINE...Titus
Area Forecast Discussion...UPDATED
National Weather Service Morristown TN
1008 PM EST Tue Feb 27 2018 .DISCUSSION... The forecast appears on track this evening as rain spreading E-NE across MS and western AL is expected to reach our area near or after 06Z. Regional 00Z raobs show a very dry layer between 850-700 mb that precip aloft will have to saturate before measureable precip is likely at the ground. The latest HRRR supports the onset timing near or after 06Z. No changes are planned at this time. && .MRX WATCHES/WARNINGS/ADVISORIES... NC...Flood Watch from Wednesday afternoon through Thursday evening for Cherokee-Clay. TN...Flood Watch from Wednesday afternoon through Thursday evening for Anderson-Bledsoe-Blount Smoky Mountains-Bradley- Campbell-Claiborne-Cocke Smoky Mountains-East Polk-Grainger- Hamblen-Hamilton-Jefferson-Knox-Loudon-Marion-McMinn-Meigs- Morgan-NW Blount-North Sevier-Northwest Cocke-Northwest Monroe-Rhea-Roane-Scott TN-Sequatchie-Sevier Smoky Mountains-Southeast Monroe-Union-West Polk. VA...None. && $$ DGS
Area Forecast Discussion
National Weather Service Nashville TN
802 PM CST Tue Feb 27 2018 .UPDATE... FOR EVENING DISCUSSION. && .DISCUSSION... Mostly mid and upper level cloudiness is on the increase across the mid state this evening. A few breaks are noted in the Plateau areas where temps are running a couple degrees below guidance. Otw, we should see the increasing cloudiness trend continue. As for the onset of the shower activity, so far the showers are reaching the ground over northwest MS. Reflectivity returns are well in advance of that. Latest Hrrr data suggests that measurable rainfall will reach into our southwestern counties just after 11 pm. This seems reasonable. Thus, will opt to make no changes to the current fcst which of course, ramps up pops after midnight. Will keep an eye on those Plateau temps, although they should begin to level off as well. && .AVIATION... 00Z TAF DISCUSSION. BNA/CKV/MQY/CSV...Previous forecast/forecast reasoning continues to hold true for the vast majority of the upcoming terminal forecast period. VFR conditions still look like they will continue thru late tonight. A trend toward MVFR ceilings is still likely after 28/10Z, as it continues to look like an area of shwrs will move in from the southwest resulting in lower ceilings and visibilities. Believe MVFR ceilings will persist also thru 28/24Z, but vsbys could fall into IFR thresholds after 28/20Z. Enhancement in sfc pressure gradient influences could result in sly sustained winds generally around 10kts gusting to 14kts-18kts at times. && .OHX WATCHES/WARNINGS/ADVISORIES... Flood Watch from Wednesday afternoon through Thursday morning for Bedford-Cannon-Cheatham-Clay-Coffee-Cumberland-Davidson-De Kalb-Dickson-Fentress-Giles-Grundy-Hickman-Houston-Humphreys- Jackson-Lawrence-Lewis-Macon-Marshall-Maury-Montgomery-Overton- Perry-Pickett-Putnam-Robertson-Rutherford-Smith-Stewart-Sumner- Trousdale-Van Buren-Warren-Wayne-White-Williamson-Wilson. && $$ DISCUSSION......21 AVIATION........31
Area Forecast Discussion
National Weather Service Pocatello ID
120 PM MST Tue Feb 27 2018 .SHORT TERM...Tonight through Friday. The latest satellite imagery was showing a weak disturbance embedded in the NW flow digging rapidly SE through the Canadian Rockies which will likely bring some light snow to the ERN mountains tonight and to a lesser extent Wednesday. Further upstream, the next stronger storm system was noted advancing into the Gulf of Alaska and will push into the NW coastal waters Wednesday night and then south along the Washington and Oregon coast Thursday and Friday. As the low shifts south along the coast, a very moist SW flow will impinge upon the CNTRL mountains with moderate to heavy snow expected Thursday and Thursday night. Hence, a Winter Storm Watch has been issued for the CNTRL mountain zones during this time frame. By early Friday morning, a frontal boundary and associated precipitation will spread east into the Snake River Plain and ERN mountains. I fully anticipate additional highlights for these ERN zones as the event continues to take shape. Temperatures ramp up toward climatological norms ahead of the low in deep southerly flow Thursday. The current forecast is warmer than the GFS statistical guidance in this regard and may be too cool yet. Temps should cool Friday behind the front and have generally followed guidance here. Huston .LONG TERM...Friday night through next Tuesday. Upper low will dominate the PAC NW with unsettled weather expected through much of Saturday and into Sunday. Models drive through a series of shortwaves through the upper low over the weekend. Not yet enough confidence to tie sensible weather to the individual waves, but keeping PoPs tied to higher elevation through the extended periods. ECMWF is the drier solution for Sunday evening through Tuesday. Both GFS and ECMWF pull the upper low out of the region starting Sunday while developing another upper low off the California coast by Tuesday. Southeast Idaho will lie between systems, and under a transient upper ridge heading into Tuesday. Hinsberger && .AVIATION...GOES Snow/Fog RGB imagery is quite revealing today. A large area of stratus is barreling across the Magic Valley and has overcome KBYI as of 17Z. Ceilings are around 2000 ft, but may drop below as seen upstream at KTWF and KJER. While one patch of stratus clears KPIH around noon, this next one will show up around 20Z, taking the terminal back to MVFR, possibly IFR. RAP soundings in BUFKIT are starting to pick up on this low-level moisture. The same field of stratus will likely hit KSUN as diurnal wind changes bring that moisture up the Big Wood River Valley. A little less certainty for KIDA and KDIJ though as models show mixed solutions to the ceilings, particularly for KIDA in the overnight hours. Hinsberger && .PIH WATCHES/WARNINGS/ADVISORIES... Winter Storm Watch Thursday through Thursday night for IDZ018-031- 032. && $$