Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 03/19/17

Area Forecast Discussion
National Weather Service Taunton MA
1000 PM EDT Sat Mar 18 2017 .SYNOPSIS... An ocean storm will pass far enough E of our region to prevent significant snowfall across SE New England through Sunday but it still will be very windy across the Cape and Islands. The highest risk is across SE MA, especially Cape Cod and the Islands. Drier and warming temperatures follow Monday and Tuesday with another arctic cool mid to late week. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... 10 pm update... This continues to be a very tough and challenging forecast. In brevity, evaluating low to mid level forcing especially within H85-7and in regards to vorticity and enhanced ascent. This coupled with H6-8 moisture availability and mesoscale lift in tandem with moisture trowaling and increasing deformation within the N/W quadrant of the developing offshore low with associated mesoscale snow banding seemingly remaining far enough E of our region. Continued signs of outcomes across the Cape and Islands, especially, developing after midnight and continuing through the morning hours. It would appear that only the 18.18z 3 km NAM and 18.21z SREF are handling present outcomes well enough. Latest WSR-88D reflectivitity shows the mid-level energy shooting through the lower Hudson Valley into CT likely to usher the deepening process in regions of more favorable baroclinicity offshore, enhancing energy already rotating N from the Mid- Atlantic within deep-layer column troughing pattern. So am confident the banding signature is going to begin developing and kick off. However still uncertain is the proximity to Cape Cod and the Islands as well as its magnitude. The HRRR is keeping a tight gradient along the I-95 corridor with impacts over Plymouth and Bristol Counties encompassing all of the Cape and Islands. However the 18.18z 3 km NAM and even the HRRR time-lagged ensemble is keeping outcomes mainly confined to the Cape and Islands, further offshore. Will keep with the going forecast for now, evaluate 19.0z guidance. If something really stands out then will make changes accordingly. Right now there is not much to work with given the continued spread even within the near-term high-res guidance. Light snow continues to impact mainly CT but will see this area transition S/E later evolving into the forecast NE-SW banding signature anticipated over Cape Cod and the Islands. Little if any impact with the initial light snow, only a coating of accumulation is expected with some minor reductions to visibility. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/... Highlights... * Snow potential has diminished across southeast New england very late tonight/Sunday with any impact likely to be low * Strong to locally damaging wind gusts still possible across the Cape/Islands on Sunday The vast majority of the 12z models guidance has trended further east with the developing ocean storm very late tonight into Sunday. The big outlier was the RGEM...which continues to indicate a significant wet snow event for the extreme southeast New England coast/Cape and Islands. Based on the rest of the model guidance...we consider the 12z RGEM a very low probability event and sided with the vast majority of the guidance. Diminished Snow Potential.... Appears the shortwave energy dropping south into the Mid Atlantic will not dig far enough to the west and south. This allows the developing ocean storm to escape further east and should spare the southeast New England coast heavy wet snow. While some light to briefly moderate snow may affect southeast MA and especially Cape/Islands on Sunday it probably results in low impact. Given the strongest forcing likely remaining offshore...coupled with a relatively mild boundary layer/increasing March sun angle it probably will be difficult for snow to accumulate particularly on paved surfaces. An inch or two of wet snow is certainly possible...but the bulk of that will probably be confined to grassy surfaces resulting in a low impact. Precipitation may also be mixed with light rain at times across portions of the Cape/Nantucket given mild boundary layer. We may also have some snow showers at times further inland across eastern MA/RI...but likely with little impact as surface temps should be above freezing. Winds... Despite a further offshore track...NNE winds and steep lapse rates from 950 mb to the surface will allow for some decent winds across the Cape and Islands. The strongest winds look to occur from late Sunday morning through Sunday afternoon. We went with a wind advisory for the Cape/Marthas Vineyard for expected 45 to 55 mph wind gusts. Opted to maintain the High Wind Watch for Nantucket as the potential exists for 50 to 60 mph wind gusts. Since this is not expected until the 2nd period...felt there was enough time for the next shift to examine and decide on a potential upgrade to a warning or to just go with an advisory. && .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/... Highlights... * Moderating temps Mon and Tue with 50 possible for some Tue! * Arctic blast with near record cold returns middle of next week * Moderate warming returns late week-weekend Overview and model preferences... Noting that differences from previous runs and all runs from 18.12Z are agree well. Therefore, will not be leaning too heavily on any given model with this update, save for maybe ensembles from both GEFs and ECEN to well represent the totality of difference solutions. Neutral/positive PNA with positive AO/NAO one might miss the downstream blocking which is fed by the sharp trof/cutoff moving E Mon. This allows for overall deepening of an arctic wave moving out of the NW Territories by mid week, which leads to another round of anomalous arctic cold for mid-late March. Therefore, the brief early week warm-up is short lived followed by another very cold outbreak similar to last weekend. Will need to watch a baroclinic zone stalled to the S as this upper shortwave settles across New England, while frontal wave energy looks to be weak and too far S for any impact on S New England, the one minor difference in latest models is a slight shift N of the precip shield. For now will continue with persistence in highlighting a mainly dry forecast. Details... Sun night into Mon... Deepening low pres shifts further E ending any remaining inland snows save for some ocean effect snows lingering for the Cape Mon night. Ocean enhancement is minimal as H85-SST delta-T values are generally around 10C or less, but still provide enough lingering lift to yield light SHSN and the continuation of clouds across the Cape/Islands into Mon. Pres gradient remains strong too across the SE, suggesting winds still gust 30-40 mph at times. Meanwhile inland regions clear such that Mon is a mainly sunny day. Min temps drop to 20s Sun night but max temps rebound into the 40s on Mon thanks to H85 temps warming to -2C or 0C. Tue... Arctic cold front will be making a late day passage (although cold advection aloft begins by afternoon). With H85 temps still near 0C or only as cold as -2C temps could make another run into the mid 40s with a few spots possibly reaching near 50. Timing of the cold advection and snowcover will play a role in this, therefore, the best chance for any one location reaching 50 will be SE MA and RI where snowpack is at a minimum to null. The FROPA is mainly dry as the column suggests little moisture but a brief sprinkle or flurry cannot be ruled out given the steepening of low-mid lvl lapse rates in response to the cold advection. Wed and Thu... Reinforcing arctic shortwave will need to be watched, mainly due to weak inverted trofing possible as frontal wave develops along the stalled arctic front to the S. For now, best F-gen and deformation remains well S of the 40 parallel, which suggests maintaining the dry forecast. Still a slight shift N is apparent with this set of runs which bears watching for early Wed AM. Confidence is very high however, that H85 temps will be dropping on their way to -20C (+2 std deviations below climatological normal as noted by the previous forecaster, and near or even below the CHH H85 temps for March 22-23). This will yield another round of temperatures well below seasonable normals with the risk for lows and low-max records to be reached or broken. Highs in the mid-upper 20s and low 30s each day with lows in the single digits are possible. More refined as we approach. Fri and Sat... Trof will shift to the E allowing gradual ridge building with connection to the Gulf of Mexico. Although an inside runner is currently suggested the wave may actually weaken as it interacts with the ridge. Will be watching for a some wet precipitation, but confidence in exact timing is low at this time. Once again, however, confidence in temps rising to near or above normal. H85 temps avg near +6C by late Fri and +8C by Sat amongst ensembles. This suggests highs in the 50s and even low 60s are in play. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Sunday/... 2z update... Overnight...Moderate confidence. VFR lowering to MVFR after midnight. Some -SN initially with some minor visibility impacts. Both linger into the early morning hours prior to -SN focusing across the Cape and Islands roughly 07Z-10Z where visibility occasionally drops to MVFR. Increasing E/NE winds with gusts up to 30 kts for KACK. Sunday...Moderate confidence. MVFR cigs and wet SN for the Cape and Islands mixing with -RA. Any accums probably confined to grassy surfaces. May also see some SHSN further northwest towards the I-95 corridor but with little impact. NNE winds should increase to between 35 and 45 knots across Cape/Islands by late morning and continue into the afternoon. A few gusts near 50 knots are possible across KACK. KBOS TAF...Moderate confidence in TAF. A few SHSN possible but expect runways to remain wet. KBDL TAF...Moderate confidence in TAF. SHSN ongoing, dissipating after midnight. Little to no impact. Wet runways. Outlook /Sunday Night through Thursday/... Sun night into Mon...High confidence. VFR develops inland, with MVFR and occasional IFR lingering Cape/Islands mainly due to low CIGS, but some lowered vsbys in light SN may linger as well. Winds inland drop yielding gusts mainly 20-30 kt. Meanwhile Cape/Island gusts may hold 30-45 kt into Mon morning. Tue and Wed...High confidence. Mainly VFR. W-NW wind gusts 20-35 kt mainly on Wed, but occasional gusts to this magnitude possible Tue as well. Thu...High confidence. VFR. Lighter winds. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Sunday/... Tonight and Sunday...Moderate confidence. Developing ocean storm coupled with high pressure across E MA will allow winds to increase very late tonight and especially Sunday. Strongest of these winds will be from mid morning Sunday into the afternoon. Therefore...left Storm Watches up for Cape Cod Bay / Nantucket sounds points S/E where its marginal for a period of gusts up to 50 knots. Across our other waters converted Gale Watches to Gale Warnings...except maintained Watches across Boston Harbor / Narragansett Bay. Outlook /Sunday Night through Thursday/... Sun night through Mon night...High confidence. Northerly gales continue with gusts 35-45 kt at times only dropping below 34 kt by late Mon morning. Small craft advisories will follow with gusts to 25 kt into Mon night. Seas peak late Sun night. 14-16 ft on the ocean waters, dropping below 10 ft by Mon afternoon. Seas will take until Tue to fully drop below small craft advisory thresholds. Tue...Moderate confidence. Westerly winds may approach 25 kt and allow seas on the ocean waters to hold near 5-6ft. Therefore Small Craft Advisories may be needed for at least a portion of the waters on Tue. Wed and Thu...Moderate confidence. NW winds once again gust 25-30 kt with seas around 5-7ft Wed. Small Craft Advisories may continued. Thu, winds and seas may finally drop below Small Craft Criteria for a bit by mid day. Otherwise, very cold temperatures could yield some light freezing spray at times Wed into Thu, but these will be dependent on final wind speeds. && .TIDES/COASTAL FLOODING... Coastal flooding appears unlikely from this storm. The main concern would be Cape Cod Bay with strong NNE wind gusts early Sunday evening with a 2 foot storm surge. However...relatively low astronomical high tides should prevent any problems. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...Wind Advisory from 10 AM to 8 PM EDT Sunday for MAZ022-023. High Wind Watch from Sunday morning through Sunday evening for MAZ024. RI...None. MARINE...Storm Watch from Sunday morning through Sunday evening for ANZ231-232-254-255. Gale Warning from 5 AM Sunday to 6 AM EDT Monday for ANZ233>235-237. Gale Watch from 5 AM EDT Sunday through Sunday evening for ANZ230-236. Gale Warning from 5 AM Sunday to 8 AM EDT Monday for ANZ250- 251-256. && $$ SYNOPSIS...Frank/Doody NEAR TERM...Frank/Doody/Sipprell SHORT TERM...Frank LONG TERM...Doody AVIATION...Frank/Doody/Sipprell MARINE...Frank/Doody/Sipprell TIDES/COASTAL FLOODING...WFO BOX Staff
Area Forecast Discussion
National Weather Service State College PA
1132 PM EDT Sat Mar 18 2017 .SYNOPSIS... A complex storm will continue to redevelop along the Mid Atlantic coast this evening and move out to sea overnight. High pressure will build in for Sunday and Monday. A moisture- starved cold front will pass through Monday night, making for a cool mid-week. Temperatures will warm up toward the end of the week. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... Latest meso-anal shows the surface low off the coast now, with an inverted trough hanging back over PA as the reflection of the upper low that is moving down over the area. The upper low is really the driver for the local weather and it will continue off to the southeast on a track that will have it near the mouth of the Chesapeake by sunrise Sunday. The forcing under the steadily falling heights aloft will keep periods of rain and snow, and eventually all snow moving through the region for at least the first half of the overnight before the low moves off to our south. Surface temps are still pretty mild so the snow so far which has finally begun to be observed at lower elevation locations is having a hard time sticking to much beyond grassy surfaces. The latest HRRR continues to show a stripe of enhanced QPF, mainly a quarter inch or less, developing ahead of the low and covering the eastern 1/3 to 1/2 of my CWA. The biggest question will be how much snow can accumulate under this stripe of slightly heavier precip. As of now it looks like the southern half of this area will stay warm enough to keep accums limited to mainly grassy surfaces. Over the norther half a fresh coating to perhaps an inch or two looks like a better bet with the expected colder surface temps. I downplayed the HPC snowfall guidance over the next 6 hours given that they put a 2-3 inch bullseye over my southern zones where temperatures are still closer to 40 than they are freezing. Lows tonight will dip into the mid/upper 20s across the northern and western mountains...and lower 30s in the southern valleys. One particular concern for late tonight and early Sunday will be the threat for freezing drizzle as the mid and higher level, seeder-feeder cloud layer peels away to the east...leaving low clouds with mean temps in the -3 to -5C range supporting cooled droplets. I downplayed this potential in the gridded forecast, but kept the mention in the Hazardous Weather Outlook. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/... Sunday will be partly to mostly cloudy with isolated light snow showers confined to mainly the Laurel Highlands. Little or no accum is expected. Temps will be several deg F below normal. Winds will be northwest and light-mdt in speed. && .LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/... A positively tilted ridge overhead will keep subsidence over the region which should help keep the region dry and also keep colder mid to upper level air over the region into Monday. A deepening upper level low over Hudson bay will extend a short wave through the mid Atlantic Monday night into Tuesday. The corresponding cold front will move in closer to Tuesday morning. The best moisture is out ahead of the front so have generally rain showers early Monday evening with a rain/snow mix possible through the northern half of Pennsylvania. There are only slight strength/timing differences between the EC/GFS operational models. Have blended using ensembles and adjusted POPS for timing. Waves of cold air behind the front will continue through Wednesday before moderating as a strong high center builds into Michigan and Ohio late Wednesday and slides into Central PA Thursday morning. ECMWF remains slower with movement of High, however this should bring a fair and dry day Thursday. Warm advection moves in by Friday ahead of the next rigorous system. There will be a chance for rain for the lower susq with a rain/snow mix possible elsewhere. The snow mix will hold on the longest throughout the northeast zones. && .AVIATION /04Z SUNDAY THROUGH THURSDAY/... Low pressure sliding southeast through central Pa will produce widespread IFR/LIFR CIGs and occasional light snow across much of the area overnight. IPT may be just east of the steadiest snow, but low MVFR CIGs still expected there. Latest near term model guidance, as well as earlier SREF, support the idea of drier air working into eastern Pa early Sun morning, resulting in a return to VFR conditions at IPT/MDT/LNS by around 12Z. Elsewhere, model soundings suggest IFR/LIFR CIGs are likely to persist into Sun morning, even though light snow should diminish late tonight. A drier northerly flow will overspread the region Sunday, as low pressure passes off the coast and high pressure builds in from the Grt Lks. Downsloping flow should yield VFR conditions at the lower elevation airfields of southeast Pa. However, model soundings and SREF probability charts indicate residual low level moisture ascending the mountains will cause MVFR stratocu to persist the rest of the day at BFD/JST and possibly even AOO/UNV/IPT. Outlook... Mon...Slight chance of early AM low CIGS BFD/JST, then a better chance of low CIGS BFD/JST Mon evening. Tue...AM Low CIGS possible BFD/JST. Slight chance of light snow southern Pa Tue evening. Wed-Thu...No sig wx expected. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte NEAR TERM...La Corte SHORT TERM...Lambert LONG TERM...Watson/Ceru/Steinbugl AVIATION...Fitzgerald
Area Forecast Discussion
National Weather Service Lincoln IL
900 PM CDT Sat Mar 18 2017 .UPDATE... Issued at 900 PM CDT Sat Mar 18 2017 Skies are slowly clearing from west to east across central Illinois this evening...with 02z/9pm IR satellite imagery indicating the back edge of the clouds along a Robinson line. Based on satellite trends, it appears the clouds will linger across the far NE KILX CWA around Rantoul and Danville until shortly after midnight. Overnight lows will mainly be in the lower 30s. Current forecast is right on track, so no major updates are needed at this time. && .SHORT TERM...(This evening through Sunday) ISSUED AT 305 PM CDT Sat Mar 18 2017 Western edge of the cloud shield has begun marching eastward this afternoon, and has made it about as far east as Monmouth and Springfield as of 2 pm. Temperatures up to around 50 degrees over west central Illinois in the clear area, but mainly holding in the lower 40s over the eastern CWA. High pressure area currently west of the Mississippi River will continue to edge eastward across the Mississippi Valley tonight. Eastern areas may take a good portion of the evening to fully clear out, but mostly clear skies will be the general rule overnight into early Sunday. Some increase in mid/high clouds can be expected later on Sunday, but temperatures should still be significantly milder than today, mainly mid to upper 50s. .LONG TERM...(Sunday night through Saturday) ISSUED AT 305 PM CDT Sat Mar 18 2017 A surface low will approach western IL Sunday night, as a cold front pushes toward NW Illinois at the same time. Rain chances will ramp up to likely after midnight, as the low reaches to near the western tip of Illinois by 12z/7am Monday. Thunderstorm chances will increase later Sunday night as well, due to an intensifying low level jet in combination with mid-level instability MUCAPE values around 1500 J/kg. SPC has maintained a Marginal Risk (5%) for severe storms west of I-55 for isolated severe hail reports. On Monday, the low pressure and cold front will push across Illinois, with the front stalling our south of the Ohio River Valley Monday night. Thunder chances will continue with the FROPA south of I-72, but no severe storms are expected on Monday. Rain chances by afternoon should be confined to east of I-55, and eventually south of I-70 Monday night. A shortwave progressing eastward across Illinois in concert with some mid-level frontogenesis, will trigger a period of showers Tuesday afternoon and Tuesday evening. That wave should quickly depart to the east, with dry conditions expected later Tuesday night through Wednesday night, under high pressure. A warm advection wing will advance toward Illinois from the SW Wed night, possibly producing a rain/snow mix for our SW counties toward Jacksonville early Thursday morning. Rapid warming at the surface and aloft will change any snow to rain by mid-morning on Thursday. It appears a band of rain will advance northeast across the remainder of central Illinois on Thursday, primarily in the vicinity of the warm front during its advance. Scattered rain showers could linger on and off Thursday night and Friday morning in the warm sector, but precip amounts would be light. Rain and storm chances will increase dramatically once the cold front finally pushes across Illinois. However, there are significant timing differences in the extended models. The GFS shows cold FROPA late Friday afternoon and evening. The ECMWF doesn`t have a clear FROPA, and actually pushes a low center across far southern IL instead. The Canadian GEM takes a surface low up the IL river valley on Saturday, with cold FROPA in the southern half of the state Saturday afternoon and evening. The extended blend ramped PoPs up to likely between midnight Friday night and Noon Saturday, but confidence is low on when likely PoPs will eventually be necessary. Friday looks to be the warmest day of the next week, as highs climb into the upper 60s in most areas. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 638 PM CDT Sat Mar 18 2017 Cloud shield continues to slowly erode and shift northeastward early this evening...with latest obs showing low VFR/high MVFR clouds along and east of a KPIA to KDEC line. Based on satellite trends and latest HRRR forecast, it appears the low clouds will scatter at all terminals over the next 1-2 hours. Winds will initially be northwesterly at around 10kt, but will become light/variable overnight as high pressure moves overhead. As the high shifts to the east, S/SE winds of around 10kt will develop from late Sunday morning through the afternoon. Mostly clear skies will eventually give way to increasing mid-level clouds after 21z: however, any lower clouds or precip will hold off until after the 00z TAF period. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Barnes SHORT TERM...Geelhart LONG TERM...Shimon AVIATION...Barnes
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
923 PM CDT Sat Mar 18 2017 .UPDATE... Issued at 923 PM CDT Sat Mar 18 2017 Updated to include 06Z aviation discussion below. && .SHORT TERM...(This evening through Sunday) Issued at 351 PM CDT Sat Mar 18 2017 Short term concern remains remaining low level clouds tonight and the chance of showers/isolated thunder developing east Sunday afternoon. Low clouds were tough to break but it does appears most will have dissipated with perhaps the exception of parts of west central Wisconsin and southeast MN. There is some threat of this lower level cloud cover to stall and then lift back to the northwest late tonight as the southerly flow develops/increases ahead of the next cold front. The HRRR has been pretty adamant on this occurring... with most other deterministic models ushering drier lower level humidity overnight. Will carry some of the mid level clouds east tonight as some of this higher level moisture rides over the western ridge. The next front moves into central MN by 18z Sunday. Models develop some instability ahead of the front...and the do saturate the lower levels by early afternoon into central MN. The GFS builds MUCAPEs to 500 J/kg and best LI`s to minus 3 ahead of the front across the eastern half. This could be enough to generate at least some isolated showers. Will include a slight chance pops for the afternoon...and move it east after 21z. Otherwise...other issue will be the temperatures. With at least some cloud cover expected...we may limit temperatures some...especially to the east...were dewpoints remain in the 30s. .LONG TERM...(Sunday night through Saturday) Issued at 351 PM CDT Sat Mar 18 2017 A couple dry cold fronts, one Sunday night, and another Monday night will keep the area in a northerly flow at the surface through early next week. High pressure near Lake Superior early Wednesday will slide to New England by Wednesday night which will begin a return flow over the Midwest. A warm front may bring some light snow Wednesday night, but accumulations would likely be rather minimal. Attention then turns to the large and slow moving cyclone late week. The GFS is faster and further north than all guidance and several ensemble members and thus was not considered. The GEM and ECMWF along with several of the GFS ensemble members are in better agreement with temporal and spatial details of the low center. As the Gulf opens and moisture begins increasing northward, a precipitation shield will develop from the central Plains to the Upper Midwest Thursday afternoon. With the system only making slow progress eastward across the central Plains and mid Mississippi Valley through Saturday, there will likely be several periods with precipitation and PoPs remain high later Thursday through Friday night. GEM and ECMWF have trended a bit tighter with the deformation band north of the system, favoring more Nebraska to southern Minnesota and central Wisconsin. Both models are advertising 2 to 3 inches of QPF during the two day event from northwest Iowa, across southeastern Minnesota into central Wisconsin, tapering to about a 1/4 inch near Alexandria, MN. The good news is a high probability of very warm air aloft with 850 mb temps of +5 to +10C will keep p-type liquid in the heavy precip swath. P-type may be a bit more questionable to the north where drier air may work in, and it could be more of sleet or freezing rain scenario depending on boundary layer temps. The system is still a ways off and things are likely to change, but did take out snow from the grids except near the onset and tail end of the precip. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 923 PM CDT Sat Mar 18 2017 Made no substantive changes to earlier forecast. Reasoning remains similar, with high pressure drifting east overnight we`ll see light winds. But, the winds will pick up from the southeast and eventually south on Sunday as a frontal boundary approaches from the west. Chances for showers still look best from near I-35 east during mid to late afternoon. A thunderstorm is possible, but best chance for that looks to be south of the forecast sites. Still don`t have enough confidence in coverage of activity to try and time in anything specific, so kept a mention of VCSH for now. Any ceilings still look to be VFR. KMSP...Primary uncertainty is with chances for showers Sunday afternoon, but not yet sold on there being enough coverage to go with more than VC at this point. /OUTLOOK FOR KMSP/ Monday...VFR. North wind 5 to 10 kt. Monday night...VFR. Variable wind 5 kt or less. Tuesday...VFR. North wind 5 to 15 kt. Tuesday night...VFR. Northeast wind around 5 kt. Wednesday...VFR. Southeast wind 5 to 10 kt. && .MPX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. && $$ UPDATE... SHORT TERM...DWE LONG TERM...BORGHOFF AVIATION...
Area Forecast Discussion
National Weather Service Pocatello ID
216 PM MDT Sat Mar 18 2017 .SHORT TERM...Tonight through Monday night. Active period of weather in store for SE Idaho through the next couple of days, which will signal an end to one of our longest stretches of dry weather in several months. A trough of low pressure is currently parked just of the Pacific Northwest coast, which is allowing for a continuation of moist and mild southwest flow over the region -- and this is resulting in an intrusion of moisture into our region. The first signs of this increasing moisture will be felt in the form of rain showers and mountain snow showers over the Sawtooths/Central Mountains as early as this evening. Snow levels initially start out high -- mainly above 7,500-8,000 feet elevation. As we progress through the evening and overnight hours, the expectation is for showers and isolated thunderstorms to develop over the Snake Plain and points east towards the Wyoming border while showers continue over the Sawtooths. Convective activity along/east of the I-15 corridor has the potential to produce gusty winds over 35 mph. Snow amounts at upper slopes are forecast generally in the 2-8 inch range. At this time, impacts appear minor with perhaps some slush on passes such as Galena and Willow Creek. Impacts through the next couple of days at this time appear limited enough to preclude a Winter Weather Advisory. Precipitation on Sunday is expected to be focused over the Sawtooths and Island Park/Divide region with gradually falling snow levels down towards 7,000 feet elevation as we progress through the day. This may mean a prolonged period of rainfall where snowpack remains up towards about 8,000 feet elevation, which may result in a quickened pace to the snowmelt and resultant runoff. On Monday, the main trough shifts overhead and thus anticipate widespread showers -- and even isolated afternoon/evening thunderstorms across SE Idaho. Southwesterly flow increases as a second trough advances towards the Pac NW coast, so this means an increase in snow levels back up towards 8,000 feet elevation by late in the day. On Tuesday, strong SW flow remains in place as a fairly significant surge of moisture and resultant precipitation begins to spread across the Sawtooths/Central mountains and eventually across the remainder of SE Idaho as we head later into Tuesday and Wednesday -- contributing to a continued rise in area creeks, streams and rivers. AD/DMH .LONG TERM...Tuesday night through Saturday. Shortwave feature still projected to eject from main Pacific trough inland Tuesday night. Frontal boundary crosses region with very little change in attendant temperatures but does help to focus precipitation as it moves through, as well as enhance thunderstorm threat in unstable air mass. Moist southwest flow continues threat for precipitation into Wednesday, but feature still appearing to split as main feature moves through Great Basin. GFS quite a bit faster with progression of southern feature as it continues east into the Plains, but slower with northern stream feature, keeping it along the coastal states Thursday. As a result, GFS remains wetter solution Thursday into Thursday night. Both models develop transitory ridge across the region late Thursday night into Friday, with ECMWF more amplified. However, both do swing next amplified trough, despite differences in depth and location of low center, toward the coast by Friday night. Given the greater amplification of the trough, ECMWF slightly slower in spreading precipitation across Idaho Saturday. Throughout extended, temperatures remain mild with continued snow melt. Snow levels are at their lowest Thursday/Friday, during periods of weakest precipitation chances, but snow could reach valley floors at least in the central and eastern mountains at this time. Periods of snow melt and flooding will continue. DMH && .AVIATION...Cloud cover spreading across the region but model trends have been to hold off precipitation onset until later this evening. Beginning to see isolated shower activity pushing into western edges of central mountains. Otherwise HRRR and RAP hold off on -SHRA until 03Z at KSUN, 05Z at KBYI, and 07Z for remaining stations. Will likely see VFR conditions continue with ceilings dropping to MVFR once the showers arrive. Precipitation appears to taper west to east after 06Z. Targeted KSUN and KDIJ for best chances at predominant shower activity and left VCSH at remaining stations. Winds have mixed quite well today and look to begin decoupling around 01Z. DMH && .HYDROLOGY...All flood products currently in effect will be allowed to continue -- with particular emphasis on the Bear Lake Basin as significant snowpack across this region continues to ripen and be converted to runoff. This on top of frozen topsoils is resulting in widespread low-land `sheet` flooding in addition to gradual rises in waterways. The Bear River may approach flood stage later this week, while the Portneuf at Pocatello approaches Moderate flood stage. The main stem Snake River is forecast to approach flood stage at Blackfoot and surrounding areas by mid- week. Depending upon the extent of snowmelt across the Salmon Basin including Stanley, we may have to consider adding these areas to our blanket of flood products. The most snowmelt and resultant runoff through mid-week is anticipated across the Bear Lake basin, Island Park/Divide region and northern Lincoln and Minidoka counties into the southern Wood River Valley. AD/DMH && .PIH WATCHES/WARNINGS/ADVISORIES... Flood Watch through Monday morning for IDZ017-019-021>025-031. && $$
Area Forecast Discussion
National Weather Service Raleigh NC
959 PM EDT Sat Mar 18 2017 .SYNOPSIS... An area of low pressure and cold front will cross central NC tonight. High pressure will build into the Carolinas from the west for the remainder of the weekend. && .NEAR TERM /THROUGH TONIGHT/... As of 1000 AM SATURDAY... Prefrontal convection loaded with numerous reports of pea size hail has just recently moved east of the CWA, as an amplifying upper trough and associated 120m height falls cross the area. The 00Z/19th raob at GSO shows a very dry atmosphere, one needing the strong dynamics and some weak instability to overcome for the earlier convection. The surface cold front currently stretches from southeast of RIC to west of RDU to near CLT. It doesn`t seem like there much chance of additional showers along the front, except in the northern coastal plain near the low and enhanced convergence through around midnight. The cold front will continue pushing east tho the coast tonight, with some wrap around showers possible northeast of Rocky Mount between 12z and 15z Sunday per CAM guidance. RAP soundings indicate an above freezing layer around 2500 ft deep at the surface and temps around 40s, so the precip should be all rain despite the rapidly cooling aloft tonight. Lows 37-41 with clear skies across most of central NC. && .SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/... As of 135 PM SATURDAY... Patchy frost or a light freeze is possible Sunday night across the northern tier counties... The upper low will be in the vicinity of Tidewater VA Sunday morning, having moved rapidly south southeast overnight. Model time sections show a surge of deeper moisture and potential for some showers accompanying the upper low, and this surge will graze our NE counties between 12 and 16 UTC. The cloud coverage and stronger cold air advection will also be slanted in that direction, resulting in a slower warmup with highs in the northeast stalling in the mid 50s, while upper 50s are expected elsewhere under mostly sunny skies. Northerly winds will gust to 20 mph, with gusts up to 25 mph along and east of I95. The pressure gradient will weaken rapidly Sunday night as high pressure builds quickly over the region, allowing winds to diminish to light and variable after sunset. Good radiational conditions will allow mins to fall to the low to mid 30s by sunrise Monday - which is about 10 degrees below normal. && .LONG TERM /MONDAY THROUGH SATURDAY/... As of 135 PM Saturday... Surface high pressure will quickly slip south of the area on Monday, with winds backing to southwest and setting up a warming trend Monday into Tuesday with highs Monday climbing to the mid 60s, and further into the low and mid 70s Tuesday. Tuesday will be a transition day despite the warm temperatures, however, as a cold front will be developing across the Ohio Valley and sinking slowly south into the area by Tuesday afternoon, accompanied by widespread showers and possibly some thunderstorms which will persist through Tuesday night as the front slowly edges south. The showers will be diminishing and should be ending across the southern tier counties by mid day Wednesday. Clearing will be rather slow, and may be delayed until Wednesday night, and the ensuing cold air advection will limit highs on Wednesday to the mid and upper 50s. The cool air mass settling down the Atlantic seaboard will push mins to the low and mid 30s Wednesday night, and highs Thursday will struggle to reach 50-55. The warming cycle begins anew on Friday as the high pressure moves offshore and southerly return flow begins raising our thicknesses and moisture levels ahead of our next cold front, tentatively scheduled to race across central NC on Saturday. Highs Friday will reach low to mid 60s, and further to the mid and upper 60s Saturday. We will see at least modest shower coverage in the prefrontal airmass early Saturday and probably a respectable line of convection accompanying the front later in the day. && .AVIATION /02Z SUNDAY THROUGH THURSDAY/... As of 800 PM SATURDAY... Scattered pre-frontal showers and storms will move E and affect RWI through around 01Z. Otherwise, initially mainly light Sly to Wly winds will veer abruptly and become gusty with the passage of a cold front between 01Z and 04Z, with continued breezy conditions, at least at times, overnight. Winds will become Nly, with some continued gustiness especially at Ern TAF sites, by mid to late Sunday morning. Outlook: The passage of another frontal zone late Tue or Tue night will result in a good chance of sub-VFR conditions and rain. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...MWS NEAR TERM...SMITH/VINCENT SHORT TERM...MLM LONG TERM...MLM AVIATION...MWS
Area Forecast Discussion
National Weather Service Blacksburg VA
1144 PM EDT Sat Mar 18 2017 .SYNOPSIS... An upper level area of low pressure will move across the area overnight. High pressure will then follow the front for Sunday and Monday. A series of cold fronts will drop south across the area Tuesday into Wednesday with additional rounds of precipitation likely. && .NEAR TERM /THROUGH SUNDAY/... As of 1125 PM EDT Saturday... Rain showers and thunder moved east earlier this evening, with next strong upstream shortwave and 80+ knot 5h jet sliding into the southern/central Appalachians just before midnight. As the center of the vort moves across the NC mtns around 200 am will see snow showers increase over the mountains of WV to NC. This wave along with some deformation on backside of exiting front may bring a few showers back toward Buckingham to Keysville after midnight. Snow accumulations in the west will range from as much as 2" over western Greenbrier, with around 1-1.5" higher terrain of Summers to Watauga and dusting or less elsewhere west of I-81. May see flurries as far east as the Blue Ridge. Otherwise, winds staying gusty but not as strong as earlier. With lows in the upper 20s to lower 30s west, to mid to upper 30s east, expect wind chills to drop into the teens at times. Previous early evening discussion... Forecast on track, had some thunderstorms with sub-severe hail across the piedmont/foothills, and even over portions of the Roanoke and New River valley since 3pm. The strongest convection has now exited Halifax County. Cold front now lined up near the Blue Ridge as evidenced by a northwest shift in winds at Roanoke with gusts to 34kts. Will still see some limited thunder/hail threat in the east til about 8pm, while in the mountains we start to see some cold air moving into the mountains with rain changing to snow showers across the Greenbrier/Bath county higher terrain by 8pm. Winds with this initial fropa surge may gust as high as 45 mph, mainly in the higher elevations/foothills, but overall stay below advisory levels except possibly in elevations above 4000 ft in NC. No advisory planned. Previous discussion from early afternoon... Cold front still just west of the mountains should finally push east across the area this evening before exiting overnight. Already seeing clusters of mainly small hail producing convection due to cold air aloft, and expect this coverage to increase/organize a bit more upon heading east of the mountains over the next few hours despite only weak surface based instability. This in line with the latest HRRR and Rap solutions so running with highest chance pops eastern half into early this evening. 850 mb front beneath the passing strong mid level shortwave trough will follow the surface front across the mountains by sunset and work through the rest of the area this evening. This will cause northwest winds to quickly increase as well as deeper cold advection as the nose of the jet aloft punches in. However latest local scheme numbers suggest that winds, other than for a surge with the front, will overall stay below advisory levels given a 40ish knot jet under a rather steep inversion without really cold air as seen in past events. Thus pushed gusts to just below criteria southern Blue Ridge where best subsidence will reside overnight. Otherwise should see clearing develop east of the mountains this evening/overnight while upslope snow showers kick in out west where an inch or two of snow looks possible through Sunday morning. Kept lows on the warmer side of guidance, mostly 30s, given mixing beneath a not overly cold airmass. Upper cold pool will be slow to depart on Sunday with the core of the mid level shortwave energy not exiting to the southeast until Sunday afternoon. This in conjunction with high pressure building in from the west may keep more of a northerly flow in place espcly east where clouds could linger piedmont from late tonight through midday Sunday. However this along with dry air/subsidence should also tend to shutoff the upslope snow showers by midday if not sooner, with mainly sunny skies in between early on. Expect all except the far northwest to finally clear out during Sunday afternoon with winds diminishing a bit as the pressure gradient starts to weaken, but still quite blustery. High temps under the cold pool likely to struggle in the 40s to near 50 mountains, while recovering into the mid/upper 50s east given aid of downslope drying and warming of dry air. && .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/... As of 230 PM EDT Saturday... High pressure builds overhead in the wake of the exiting upper cold pool Sunday night before sliding to the south Monday in advance of the next upstream cold front. This will make for another cold Sunday night with lows in the 20s to lower 30s under good radiational cooling. Warmer air quickly returns Monday under westerly flow aloft and 850 mb temps jumping to near +10C by the end of the day. This combined with sunshine and clouds not increasing until afternoon supports highs mostly in the upper 50s to mid 60s with any isolated showers holding off across the far northwest until late. Deepening moisture/clouds continue to increase Monday night with added shower bands arriving across the western sections espcly after midnight. Otherwise mainly dry out east under strong downsloping flow aloft and better moisture convergence stuck over the far west. Should be milder under warming aloft and mixing with lows mostly in the 40s. Front will drift into the area Tuesday and perhaps linger southern sections Tuesday night before finally getting shoved to the south via passing stronger shortwave energy to the north on Wednesday. This scenario remains uncertain with guidance showing a possible weak wave along the boundary by Tuesday night which could result in more widespread precip into early Wednesday. Exactly where/if low pressure develops key to pops Tuesday afternoon into Wednesday with some solutions farther south and others leaving moisture around with colder air bleeding in from the north at the end. For now will continue mostly chance pops except a period of likelys late Tuesday into Tuesday night mainly southern/eastern half including some light snow far northwest toward daybreak Wednesday as deeper cold advection arrives. Models also indicate quite a bit of instability over the far southern sections late Tuesday so including a thunder mention there as well. Should finally see decreasing clouds from north to south by Wednesday afternoon but cooler with highs mainly 40s north/west to 50s elsewhere after a rather mild Tuesday. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... As of 1245 PM EDT Saturday... Shortwave ridging will strengthen over the region later next week in the wake of a passing cold front to the south by Wednesday night. This will give rise to strong high pressure building southeast across the Great Lakes before wedging south down the Mid-Atlantic coast Thursday into Thursday night. However models remain uncertain in just how strong the wedge will be espcly in regards to low level moisture and subsequent low clouds. At this point appears the dry wedging wont be strong enough to scour out clouds along the southern Blue Ridge, but could see more clearing elsewhere given the closer proximity of the parent high just to the north. Otherwise will be chilly but dry into Thursday night. High then slides offshore later Thursday night allowing a weak warm front to shift north on Friday, in turn scouring the wedge under rebounding temps to more seasonal levels. Next round of shortwave energy heads out of the Rockies by the end of the week with an associated cold front approaching by next weekend. Timing of this boundary into the eastern ridging remains iffy but appears enough return of deep moisture to warrant a chance of showers mainly Saturday afternoon and overnight. Should also be all liquid with temps well above normal by Day7. && .AVIATION /04Z SUNDAY THROUGH THURSDAY/... As of 712 PM EDT Saturday... Looking at drying conditions east of the mountains this evening with cold front pushing across and out of the piedmont by 01z. Will see gusty winds across the mountains/foothills early on, with some gusts over 35 kts near TNB-HSP, but a little less at the taf sites. Should start to see some lower cigs working into BLF/LWB after 03z, with rain or snow showers starting up after 06z, changing to all snow showers by 09z. Appears most of the snow will be west or northwest of LWB/BLF so have no limited vsbys yet. Northerly flow will work in Sunday with cigs rising to VFR in the mountains by 12-15z. Not out of the question from LYH/DAN to have some mid/high clouds Sunday but nothing to affect aviation. Extended Aviation Discussion... High pressure building in on Monday should yield VFR all terminals to start the week. However moisture ahead of another cold front and associated weak low pressure may arrive by Monday night, with sub-VFR possible later Monday night mountains and all areas Tuesday into Tuesday night before improving conditions back to VFR take shape during Wednesday. By Thursday high pressure will wedge in from the northeast so will stay VFR though increasing clouds are expected by afternoon, but should stay VFR. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH/WP NEAR TERM...JH/WP SHORT TERM...JH LONG TERM...JH AVIATION...AMS/JH/WP
...Update to aviation forecast discussion...

.SHORT TERM...(This evening through Sunday) Issued at 338 PM CDT Sat Mar 18 2017 The 20Z afternoon surface analysis showed a high pressure axis extending down the central Missouri River basin, bisecting the eastern half of the CWA. Upper level ridging encompassed much of the western CONUS with high orographically-generated cirrus spilling southeastward across the Central Plains. As the high slides east tonight, return flow is expected to bring an increase in low-level moisture northward from the Southern Plains. Low level stratus should be the visual manifestation of this moisture, working its way northward this evening and persisting through the overnight. This H850 saturated nose in combination with a modest EML will create an unstable profile with MUCAPE values ranging from 1000-2000 by 12Z Sunday (though some of the NAM profiles look somewhat unrealistic with an exaggerated warm nose). With a 30 to 40 kt LLJ anchored just under this unstable layer, it would not take much of a perturbation to launch a parcel. However, given the weak effective shear profiles, little in the way of organized or long-lived convection is expected, with small hail being the only real threat from these elevated storms. The best threat for initiation based on the latest CAM consensus would be over the southern and eastern CWA, moving out of the area around 15Z. Kept POPs at slight chance to chance wording given the uncertainty in coverage and timing. Attention then turns to Sunday`s near record to record high temperatures as H850 temps surge to +15 to +20 C. How quickly the lingering stratus can clear will dictate the eastward extent of the 80+ degree readings tomorrow. Early indications from the RAP point toward the stratus being thin in nature and will burn off quickly as solar insolation increases during the early to mid morning hours. Thus leaned towards the more aggressively warm solutions for highs tomorrow, with highs in the 80s CWA-wide with upper 80s in the south and west. This would easily set record highs at Topeka (record high for tomorrow being 82 set in 1907) and Concordia (record high: 81 set in 1921). Also increased winds above 20 kts sustained in the south on Sunday with a modest pressure gradient in place, likewise increasing the fire danger over these same areas. .LONG TERM...(Sunday night through Saturday) Issued at 338 PM CDT Sat Mar 18 2017 Sunday night a shortwave moving east through the upper zonal flow across the Northern Plains will bring a frontal boundary southward into northeast Kansas by Monday morning. The front is forecast to gradually move to the southeast through the day as high pressure builds southward into the Central Plains. This present a challenge for high temperatures with areas behind the front in the 60s with mid to upper 70s ahead of the front. The next chance for precipitation looks to be Tuesday into Wednesday as a series of small waves move eastward across the area in the zonal to slightly northwest flow. Moisture will begin to return northward over the frontal boundary to the south Tuesday night into Wednesday. Thermal profiles suggest that parts north of I-70 may see a mix of rain and snow with parts of north central Kansas seeing some light west snow. The main focus for the forecast shifts to the main upper trough moving into the Plains for the end of the week. The medium range models continue to differ with the speed and depth of the upper low. That said have retained continuity for the end of the week leaning toward and ensemble mean solution. A warm front moving northward from southern Kansas Wednesday night along with an increasing low level jet will lead to elevated thunderstorms into Thursday morning. A rather dynamic upper low is expected to move out into the Plains by Friday. Given the differences in the models confidence in the placement of the surface synoptic features remains low at this time. Shear and instability along with moisture should be sufficient for strong to severe storms from Thursday through Friday evening. Temperatures will be cooler in the 50s Tuesday and Wednesday before warming back into the 60s Thursday. && .AVIATION...(For the 00Z TAFS through 00Z Sunday evening) Issued at 623 PM CDT Sat Mar 18 2017 VFR conditions are likely through the TAF period. Primary aviation impacts are potential for scattered TS between 09-13Z at TOP/FOE. Also expect winds around 35 kts at 1300 feet, and have not included LLWS at this point but conditions will be borderline for inclusion between 08-13Z. && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Skow LONG TERM...Wolters AVIATION...Barjenbruch