Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 10/03/18


Area Forecast Discussion
National Weather Service Bismarck ND
854 PM CDT Tue Oct 2 2018 .UPDATE... Issued at 852 PM CDT Tue Oct 2 2018 Based on NDDOT webcam and surface observation trends, issued a Dense Fog Advisory through 12 UTC for northwest and far north central North Dakota. An advisory may be needed later tonight for south central North Dakota and the James River Valley. UPDATE Issued at 634 PM CDT Tue Oct 2 2018 Fog potential tonight, precipitation tonight and Wednesday, and strong winds on Wednesday highlight this update. Fog and drizzle continue to develop across south central North Dakota as of 00 UTC. The HRRR/NBM/RAP/GFSLamp through their 22 UTC iterations maintain the stratus and expand the fog through the night across the south central and James River Valley, and possibly towards the Dickinson and Hettinger areas. This seems likely given the observed trends with light southerly surface winds maintaining the low level moisture with dew points in the upper 40s and lower 50s. A Dense Fog Advisory may be needed. As of 00 UTC, a quasi-stationary front across western into far north central North Dakota will begin to propagate southeast as a cold front tonight, and clear the James River Valley by mid day Wednesday. Precipitation will increase on the cool side of this boundary late tonight into Wednesday morning with the arrival of the leading impulses ahead of the potent shortwave. Precipitation should be in the form of rain tonight across the north, transitioning to snow Wednesday morning along and north of US Highway 2. Across the southwest and south central, scattered rain showers are possible late tonight into Wednesday morning, with a thunderstorm not out of the question given the steep mid level lapse rates. Regarding winds for Wednesday, the 22 UTC RAP and 18 UTC NAM low level wind fields are stronger than the 18 UTC GFS in strong cold air advection and pressure rises behind the cold front. The NAM/RAP would support a Wind Advisory, especially south of US Highway 2. Will continue to monitor trends in the guidance through the evening. High temperatures on Wednesday are likely to be reached overnight, with falling temperatures through the day. && .SHORT TERM...(This evening through Wednesday) Issued at 111 PM CDT Tue Oct 2 2018 Concerns for this forecast period involve accumulating snow across northwest North Dakota late tonight and Wednesday morning, then gusty winds across much of central and southwest North Dakota Wednesday afternoon. First, the h500 flow is setting up to bring a shortwave trough from the northwest CONUS through the northern plains by Wednesday afternoon. This will set up broad lift across the region tonight and Wednesday morning. As the baroclinic zone slides south through the region tonight, we expect a brief period of enhanced vertical motion as isentropic lift and frontogenetic forcing briefly line up. Temperatures will be around the critical threshold for snow across the north central and northwest, where we expect one to two inches of accumulation across the far northern tier of counties from divide through Bottineau Wednesday morning. Second, subsidence behind the shortwave will enhance momentum transfer resulting in increasing northwest winds Wednesday afternoon. The NAM in particular indicates this, with potential wind gusts to 45 mph for one to 3 hours. However the GFS is more subdued, suggesting 25 to 35 mph winds. Will hold off on wind advisory for now. .LONG TERM...(Wednesday night through Tuesday) Issued at 111 PM CDT Tue Oct 2 2018 The extended forecast will encompass two periods of concern for early winter weather events. First, a negatively tilted h500 trough will migrate northeast into the northern plains from southern California on Thursday night and Friday, spreading precipitation across the region. Temperatures again will be near the critical threshold for rain and snow, with the possibility of accumulations mainly across the north and east central. The difference of one or two degrees in temperatures here will dictate more or less snow, so uncertainty remains high for how far south the snow will reach. The remainder of the long range will be dominated by a large slow moving upper low across the western CONUS. Much uncertainty remains with this feature, as models have been increasing the strength of a ridge over the east coast, which may hold up the progression of this low, per the European. If this becomes the favored solution then warmer air can be expected across the northern plains. If not, then the possibility of more accumulating snow exists per the GFS. Either way, the QPF from this storm will be rather substantial for this time of the year. Will continue to highlight the uncertainty in the weather messaging. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 852 PM CDT Tue Oct 2 2018 IFR stratus and fog this evening will expand across south central North Dakota and the James River Valley tonight, with LIFR/VLIFR visibility in fog developing. This includes KBIS and KJMS. The stratus and fog may approach KDIK late tonight into early Wednesday morning, however, this is somewhat uncertain. A stationary front across western through north central North Dakota as of 00 UTC will move southeast as a cold front overnight into Wednesday morning. LIFR/VLIFR stratus and fog will expand tonight behind this front across the northwest and north central impacting KISN/KMOT. Rain will develop across northern North Dakota tonight, changing to snow Wednesday morning with IFR conditions. Scattered rain showers, and perhaps a thunderstorm, are possible tonight into Wednesday morning southwest and south central. Strong northwest winds with gusts of 30-40 kts will develop Wednesday across most of western and central North Dakota. && .BIS WATCHES/WARNINGS/ADVISORIES... Dense Fog Advisory until 7 AM CDT Wednesday for NDZ001>003- 009>011. && $$ UPDATE...PA SHORT TERM...WAA LONG TERM...WAA AVIATION...PA
Area Forecast Discussion
National Weather Service Boston/Norton MA
1045 PM EDT Tue Oct 2 2018 .SYNOPSIS... Low pressure over the Eastern Great Lakes will cross New England tonight, bringing showers and a few thunderstorms along with some heavy rainfall. Clouds may linger Wednesday morning, but high pressure will build in with dry and seasonable temperatures weather the rest of the day. An unseasonably warm afternoon is on tap for Thursday ahead of an approaching cold front. Dry but seasonably cool weather follows Friday and Saturday. Well above normal temperatures are expected at times next week and in fact some record highs may be challenged. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... No major changes to the forecast this evening. Tried to time out rainfall chances based on observed radar trends. Last few runs of the HRRR appear to have the correct idea on placement, but the timing is off by a couple of hours on the slow side. Latest surface observations indicate a low pressure near Syracuse, NY, moving east along a front draped across southern New England. A mesolow was also noted near Boston. This low pressure will continue to move east overnight. Still expecting drier weather to develop after midnight, but it may be closer to daybreak before threat of rainfall ends across the western half of southern New England. Not anticipating much change to temperatures, which should remain within a few degrees of where they are this evening. Previous Discussion... Main action through early this evening has been across the southern portion of Hartford and Tolland counties. Some locations picked up a quick 1.50 to 2 inches of rain in an hour...leading to some street flooding. Currently...mainly heavy showers moving across RI and SE MA but there remain a few embedded t-storms. Overall...heavy showers and embedded t-storms will continue to track across the region overnight with a strong shortwave/forcing. The greatest risk for flash flooding/severe weather will remain southwest of our region where the better instability resides. We still need to monitor the risk for localized flooding and a low probability for isolated severe weather overnight across our CT/RI and SE MA zones. However...confidence in our region is not high enough for any SVR/FFA headlines at this point but will continue to monitor. Otherwise...models have been too aggressive in lifting warm front northward. The front currently runs along a line from BDL..to SFZ...to near OWD. The front should lift a bit further north over the next several hours...but some high resolution guidance especially the 4 km NAM shows a meso-low shifting the winds back to the northeast across northeast MA and possibly further southwest. In fact...parts of northeast MA may never see the warm front cross the region. Will have to watch for areas of fog in this region...especially in areas where cooler air works back into the region. Temps will be in the 50s north of the front and 60s south of the front. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/... Leftover convection over Cape Cod and Islands Wednesday morning during the commute, but this will move offshore. Weak high pressure trails the shortwave and crosses our area during the afternoon/evening. Expect a dry day with increasing sunshine. Temps at the top of the mixed layer would support max temps in the low to mid 70s. Light winds will support local sea breezes in the usual locations. Dry weather continues into Wednesday night, although light south flow will bring increased moisture and may support some fog and low clouds overnight. && .LONG TERM /THURSDAY THROUGH TUESDAY/... Highlights... * Unseasonable warmth expected Thu afternoon * Dry and cooler with seasonable temps Fri/Sat * Near record high temperatures possible at times next week Details... Thursday... Approaching cold front will result in anomalous mid level warmth overspreading southern New England. 850T rise to between +16C and +18C by Thu afternoon along with southwest surface winds. This should result in afternoon high temperatures in the upper 70s to around 80 in many locations. The cold front will cross the region late Thu into Thu night. There is not much instability/forcing ahead of this front...so not expecting much more than the risk for a few brief showers. Friday and Saturday... Canadian high pressure will build south behind the cold front Fri into Sat. This will result in the return of cooler/seasonable temperatures along with dry weather. High temperatures both days will mainly be in the 60s, with the cooler day being Friday especially along the coast. Next Week... Anomalous upper level ridge will build north into southern New England. This will result in above to well above normal temperatures at times. Given this setup...the potential for afternoon highs reaching into the 80s for a couple days is a pretty good bet. In fact...we could be looking at near record high temperatures for a day or two. The one fly in the ointment is a potential backdoor cold front that could cool us down a bit. Timing is highly uncertain...but most guidance is indicating the best chance for these briefly cooler temps would be Mon. Dry weather looks to dominate for the first half of next week given upper level ridging in control. We can not rule out a few showers on Monday with the backdoor cold front...but does not look like much at this time. && .AVIATION /03Z WEDNESDAY THROUGH SUNDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday Night/... Tonight...High confidence. IFR to LIFR conditions in showers and isolated t-storms in most locations early this evening will persist overnight. MVFR-VFR conditions across the Cape/Islands will deteriorate to IFR-LIFR thresholds overnight. Wednesday...Moderate confidence. IFR to even LIFR conditions may persist for at least part of the morning...especially across eastern New England. Improvement occurs from west to east...but timing uncertain Wednesday night...High confidence. VFR, with IFR possible in patchy BR. KBOS Terminal...Moderate confidence. KBDL Terminal...Moderate confidence. Outlook /Thursday through Sunday/...Moderate to High Confidence. Thursday: Mainly VFR, with local MVFR possible. Breezy. Thursday Night: Mainly VFR, with areas MVFR possible. A slight chance of rain showers. Friday through Friday Night: VFR. Breezy. Saturday through Sunday: VFR. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Wednesday Night/... Tonight...Low pressure moves east across New England tonight, pulling a cold front across the waters later tonight. Clouds and fog may linger through the early night, with best chance for showers and scattered thunder during the mid and late night. Poor visibility during the night. South to southwest winds gust to 25 knots, with 5-6 foot seas on the outer waters. A Small Craft Advisory continues for all waters. Wednesday...The cold front and showers move offshore and out to sea on Wednesday morning. High pressure moves over the waters with dry weather.Winds turn out of the north with diminishing speeds, but with sea breezes near the coast. Seas 5-6 feet on the outer waters will subside during the afternoon. Wednesday night...Winds remain less than 25 kt and most seas will be less than 5 feet. Parts of the outer waters may have seas near 5 feet. Developing fog may lower vsbys to 1 to 3 miles. Outlook /Thursday through Sunday/...Moderate to High Confidence. Thursday: Winds less than 25 kt. Seas up to 5 ft. Thursday Night: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Seas up to 5 ft. Slight chance of rain showers. Friday: Moderate risk for Small Craft Advisory winds with gusts up to 30 kt. Rough seas up to 9 ft. Friday Night: Winds less than 25 kt. Rough seas up to 9 ft. Saturday: Winds less than 25 kt. Areas of rough seas. Saturday Night through Sunday: Winds less than 25 kt. Local rough seas. && .HYDROLOGY... As noted, precipitable water values build through the evening, then top out around 1.75 inches tonight before diminishing toward morning. The combination of deep moisture and strong lift is expected to bring local downpours that could cause 1-2 inch/hour rain rates in spots, which could cause some urban/small stream/poor drainage flooding. Previous rain has been substantial, but it has also had some time to drain off. Sufficient uncertainty on amounts and coverage to hold off on a watch, but we will continue to monitor this rainfall. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...None. RI...None. MARINE...Small Craft Advisory until 9 AM EDT Wednesday for ANZ231>234. Small Craft Advisory until 4 AM EDT Wednesday for ANZ230-236- 251. Small Craft Advisory until 10 AM EDT Wednesday for ANZ235-237. Small Craft Advisory until 4 AM EDT Thursday for ANZ250- 254>256. && $$ SYNOPSIS...WTB/Frank NEAR TERM...Belk/Frank SHORT TERM...WTB LONG TERM...Frank AVIATION...WTB/Belk/Frank MARINE...WTB/Frank HYDROLOGY...
Area Forecast Discussion
National Weather Service Cheyenne WY
946 PM MDT Tue Oct 2 2018 .UPDATE... Issued at 932 PM MDT Tue Oct 2 2018 The main near-term concern for tonight is the potential for strong winds in the wind prone areas of southeast Wyoming. Uncertainty is high for the Bordeaux area, as several high-resolution models have trended toward showing minimal eastward progression of the surface trough. This would limit potential for 50+ knot gusts. However, we have seen an up-tick in low-level gradients along/w of the Laramie Range. The H85 CAG-CPR gradient could approach 60 meters by around 15z Wed. Despite fairly modest H7/H85 flow over ARL, mountain wave activity may be sufficient for a few 60 MPH wind gusts as the HRRR has suggested over the last several runs. In addition, a 2 to 3 mb pressure gradient over the I80 summit could also lead to a few 55- 60 MPH wind gusts near Vedauwoo/Buford. Issued a High Wind Warning for ARL/VDW, as well as BRX despite the uncertainty. The peak wind gusts should occur around 15z Wednesday. Updates have been sent. && .SHORT TERM...(This evening through Thursday) Issued at 145 PM MDT Tue Oct 2 2018 Mid-to-high level moisture continues to stream into the region ahead of Rosa`s remnants. Showers can be seen on radar across western Colorado; these showers will reach portions of Carbon and Albany Counties later this afternoon, with only denser areas of cloud cover noted elsewhere. Behind Rosa, an upper-level zonal flow will set in overnight. Under this pattern, the area of concern will be the I-25 "wind" corridor between Chugwater and Wheatland. A deep, shallow inversion will set up on the lee side of the northern Laramie Range overnight, prohibiting the stronger flow aloft from mixing down to the surface. However, the inversion looks like it`ll break in the early morning hours which will allow for mixing down to the surface. Additionally, a lee surface low will develop shortly after the inversion breaks. This set up, along with funneling through the local terrain, will bring strong and gusty winds from the west and southwest across the I-25 corridor near Bordeaux from about 0300 to 0900 MDT. A high wind watch is out for this period and will continue to be accessed as the event approaches. Moving into Wednesday afternoon, cloudy and windy conditions will prevail as the next upper level low pressure system moves in from the west. A mid-level vorticity maximum will be ejected from the flow and move across the region through the day Thursday. This will aid in the continuation of windy conditions across the whole of the region, in addition to rain showers, for the duration of the day. .LONG TERM...(Thursday night through Tuesday) Issued at 145 PM MDT Tue Oct 2 2018 Long term forecast continues to be tricky with respect to an amplified flow pattern. Hemispheric water vapor continues to show a favorable regime for the development of a progressive amplified mid level flow regime. An amplifying downstream subtropical ridge and large west coast trough will be key in the placement of individual features. Friday, a shortwave trough is progged to eject over the front range bringing showers and possible storms. WInds aloft will be increasing thanks to a mid level jet of 55 to 60 kts. Some concerns for high winds along and behind a cold front were noted. Winds were increased in the grids. Multiple rounds of precipitation are likely as a weak lee side low moves through south central Wyoming and into the plains. Showers and possible high elevation snow will develop Friday and continue through Saturday. This appears to be the first chance of the season for significant high elevation snow. This does however depend on the placement, the timing, and the strength of the colder air from a canadian maritime high. Sunday, potential exists for a very strong lee low to move close to the area brining heavy precipitation. A large 500 mb trough with strong DPVA and an attendant 90kt jet streak is expected to move into the Great Plains Sunday morning. Should the strong low develop in northern colorado, upslope flow with showers and embedded thunderstorms will be likely. Currently, models are split. The Canadian and the ECMWF show a low developing much further south, while the GFS and the new FV3 continue to show a very deep sub thousand millibar low in northern/central Colorado. GFS Ensembles show good clustering of the lows in this region, lending some confidence to the GFS solution. EPS solutions are a bit broader and weaker with the surface low but overall deeper and more closed off with the trough. While exact confidence is not high, both models show very strong lift over the front range with ample moisture for precipitation. A strong artic cold front will also bring the cold air necessary for winter weather Sunday night through tuesday. Should the timing of the cold air and the strong lift coincide, mountains may see heavy snowfall for the first time this season. This will need to be watched closely over the next few forecast cycles. Regardless, both solutions favor a wet and cooler regime than the warm september temperatures we have seen. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 613 PM MDT Tue Oct 2 2018 VFR prevails. Rain showers will likely become more widespread this evening/overnight, mainly across Carbon county as remnant moisture from Rosa continues to stream northward. Ceilings at KRWL may fall to near 3000 feet at times. Otherwise, expect SCT to BKN sky cover between 5k and 15k feet AGL for most terminals. Gusty winds likely to develop across much of the region on Wednesday, with gusts over 30 knots common. && .FIRE WEATHER... Issued at 145 PM MDT Tue Oct 2 2018 Critical conditions no longer as moisture streams in from the south and west today and cloud cover increases and lowers across the region. Rain showers and a slight chance for thunderstorms expected nearly each afternoon/evening through the extended. Windy conditions are expected overnight tonight and through the day Wednesday and Thursday. Snow possible as early as Friday across the higher elevations. Snow levels will lower as we move into next week. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...High Wind Warning from 6 AM to noon MDT Wednesday for WYZ106-110- 116. NE...None. && $$ UPDATE...CLH SHORT TERM...AB LONG TERM...AL AVIATION...CLH FIRE WEATHER...AB
Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
801 PM PDT Tue Oct 2 2018 .SYNOPSIS...02/731 PM. Light to moderate rain will fall across the region tomorrow with a slight chance of thunderstorms. Showers may linger into Thursday morning. Temperatures will remain below normal into next week though with some warming on Friday and Saturday. && .SHORT TERM (TUE-FRI)...02/801 PM. ***UPDATE*** Overall, the weather looks to be behaving as forecast. Latest radar shows some showers off the Central Coast which should start to move onshore later this evening. Elsewhere, will expect continued cloudy skies this evening with some isolated showers or sprinkles as atmosphere continues to moisten up. Current look at latest high-resolution model data as well as QPF analysis indicates current forecast looks very much on track. Steady rain will develop over the Central Coast tonight then across Ventura/LA counties during the day on Wednesday. Current QPF numbers, as stated below, still look good. Models are still indicating a decent amount of instability as the front moves through. So, the slight chance of thunderstorms late tonight and Wednesday looks good. No significant updates to the forecast are planned at this time. ***From Previous Discussion*** Upper low sliding south now which has effectively shut off any eastward propagation of the frontal band, the leading edge of which remains about 60-90 miles west of the Central Coast. There were a few showers out ahead of it that brought a few drops of rain to parts of SB/SLO Counties earlier today. Not much since then and probably not much more until at least this evening. Models have been consistent showing the low levels moistening up this evening under light to moderate southerly flow while the frontal band remains offshore. The HRRR and NBM are the only models showing precip over land this evening and this is a reasonable scenario assuming the low levels moisten up as both the GFS and NAM expect. Best chances this evening will be south of Pt Conception, especially upslope areas, with amounts generally under a tenth of an inch. The main action expected later tonight into Wednesday once the upper low finally starts moving east again and that main frontal band moves towards the coast. Upper level diffluence along with some vorts moving around the low will provide a favorable environment for thunderstorm formation along that band which will progress slowly east through the day. Models continue to advertise small pockets of heavier precip developing later tonight, likely with thunderstorms. Don`t have much confidence in the precise locations of these but it does provide evidence that convection will be a factor. Outside of convection rainfall amounts and rates should be well below critical levels. However, brief heavy rain is possible with thunderstorms and while most convective rates should top out around a half inch per hour there`s a non-zero risk of a storm forming over the recently burned area with rates reaching critical levels. For SB/Ventura counties the most likely period of time would from mid to late morning Wednesday through mid afternoon and from noon to 8 pm for LA County. Previous rainfall forecast still looks on track, generally a half inch or less for most lower elevation locations and up to an inch in the foothills/mountains. And obviously higher amounts possible where thunderstorms develop. Showers expected to taper off Wednesday evening but could still be some lingering light showers into early Thursday. After that dry and warmer Thu/Fri under mostly clear skies. Likely some locally gusty north to northwest winds developing across SB/SLO counties and adjacent coastal Friday and Friday evening. .LONG TERM (SAT-TUE)...02/134 PM. Models have been consistent the last few days showing a cold upper level trough setting up across the western third of the US this weekend through early next week while a monster ridge develops along the east coast. This combined with a strong onshore trend Saturday will bring cooling to most of the area. Then Sunday through Tuesday the GFS is indicating a huge eddy circulation developing that will rapidly spin up the marine layer to over 5000` deep south of Pt Conception (especially Ventura and LA Counties) and it even generates some light rain. The ECMWF is a little farther east with the trough and not nearly as cold and gloomy. For now have trended towards the colder/cloudier GFS solution with highs mostly in the 60s to lower 70s for coast/valleys. Areas north of Pt Conception would be a little warmer and generally cloud free in this scenario. && .AVIATION...02/2216Z. At 2130z, the marine inversion at KLAX was based at 800 feet. The top of the inversion was 1700 feet with a temperature of 20 degrees Celsius. Overall, low to moderate confidence in 00Z TAF package. Moderate confidence through early Wednesday in VFR conditions for all sites. Main concern will be cold front forecast move through on Wednesday. All sites should receive steady rain, but confidence in timing is low. There will be a 20% chance of thunderstorms on Wednesday for all sites. KLAX...Overall, moderate confidence in 00Z TAF. There is a 20% chance of MVFR CIGs 02Z-16Z. High confidence in rain with MVFR conditions on Wednesday, but low confidence in timing. There is a 30% chance of east winds 8-10 knots 14Z-20Z. KBUR...Overall, moderate confidence in 00Z TAF. There is a 20% chance of MVFR CIGs 02Z-16Z. High confidence in rain with MVFR conditions on Wednesday, but low confidence in timing. && .MARINE...02/800 PM. For the Outer Waters, moderate confidence in current forecast. There is 30% chance of Small Craft Advisory (SCA) level southeast winds tonight and Wednesday. High confidence in SCA level northwest winds Friday through Sunday with a 30% chance of Gale force winds. For the Inner Waters north of Point Sal, high confidence in current forecast. There is a 70% chance of SCA level northwest winds during the afternoon/evening hours on Saturday and Sunday. For the Inner Waters south of Point Conception, moderate confidence in current forecast. There is a 50% chance of SCA level winds across western sections Friday through Sunday during the afternoon and evening hours. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && .HAZARD POTENTIAL OUTLOOK (FRI-TUE). Gusty northerly winds possible across SLO/SB Counties Friday and Saturday. && $$ PUBLIC...MW/RAT AVIATION...RAT MARINE...RAT SYNOPSIS...Kj weather.gov/losangeles
Area Forecast Discussion
National Weather Service Blacksburg VA
836 PM EDT Tue Oct 2 2018 .SYNOPSIS... High pressure across the region will maintain overall dry and warm weather through late in the week. A cold front will sag southeast into the area later Friday resulting in a chance of showers and storms. High pressure then returns to the region for the weekend. && .NEAR TERM /THROUGH WEDNESDAY/... As of 830 PM EDT Tuesday... Weak moisture convergence zone/surface trough along the southern Blue Ridge has resulted in a few showers developing just after sunset as dewpoints maxed out at dark. However given lack of much instability and support aloft, expect these to fade soon so only carrying an isolated shower during the next hour or so over the southwest. Also appears band of convection over northern West Va, well ahead of the front to the northwest, will also fade with loss of heating and supported by the latest HRRR which keeps most of the showers to the north overnight. Cant totally rule out a shower far northwest sections late within the trailing northwest flow, so keeping in a low pop in part of the I-64 corridor. Otherwise appears enough clearing to promote at least patchy fog development valleys, and where earlier showers occurred with perhaps dense fog in spots over the west. Nudged lows up slightly mainly east in response to higher dewpoints although should still see readings in the upper 50s-mid 60s given radiational cooling again overnight. Previous discussion as of 215 PM EDT Tuesday... Weak cold front approaching from the northwest is helping to generate scattered showers/thunder across the Appalachians and central mid Atlantic region early this afternoon. The front will wash out across the region tonight then lift back northward tomorrow. Surface winds look to remain light/variable while the low level flow becomes predominately northwest. Expect this will keep clouds and some showers at the higher terrain in light upslope flow. Fog potential is challenging overnight since some upslope clouds west of the ridge will impede cooling, but if clouds become scattered there will be windows of time when fog can develop, even moreso if cloud coverage is less than anticipated. Any fog/stratus/lingering upslope showers will dissipate Wednesday morning. Guidance is hinting at some development of showers/thunder along the southern Blue Ridge into the mountains of NC tomorrow afternoon with weak upslope flow coupled with some short wave energy and isentropic lift. Temperatures will remain well able normal with lows tonight in the low/mid 60s and highs Wednesday in the low/mid 80s east of the Ridge to mid/upper 70s to the west. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/... As of 235 PM EDT Tuesday... Large ridge aloft centered over the mid-Mississippi Valley will build northeast through Friday night. This ridge will reach the southern Appalachians by Friday. Any isolated showers or thunderstorms Wednesday afternoon will diminish quickly Wednesday evening with the loss of solar heating. The best chance will be in the northwest mountains of North Carolina. It will remain warm and humid Wednesday night with low temperatures ranging from the mid 50s in the mountains to the mid 60s in the piedmont. With 850 mb temperatures from 14 to 17 Celsius combined with partly sunny skies Thursday will warm high temperatures to the mid 70s in the mountains to the mid 80s in the piedmont. Scattered showers and isolated thunderstorms will form ahead and along the cold front as it drop southeast Thursday. Thursday night into Friday, the cold front will reach northern portions of the Mid-Atlantic region. The challenge of the forecast is how far south the surface boundary progresses. The best chance of clouds and a few rain showers will occur Thursday night across northwestern portions of the forecast area. Low temperatures Thursday night will remain mild with readings from around 60 degrees in the west to the mid 60s in the east. Northerly flow associated with a strong Canadian surface high over the St. Lawrence River Valley should propel the backdoor front and wedge southward Friday into Friday night. High temperatures Friday are tricky with wedge and clouds. It will still be mild but cooler from around 70 degrees in the north to the lower 80s in the south. Utilizing the Superblend for pops on Friday. Clouds and the potential for showers will continue Friday night into Saturday morning. Low temperatures Friday night will vary from near 60 degrees in the mountains to the upper 60s in the piedmont. Overall forecast confidence is moderate. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As of 235 PM EDT Tuesday... A broad upper ridge across the Southeast will amplified to the northeast into the weekend, then shifts east into the Atlantic early next week. The zonal flow across the northern tier of the county will keep the deeper convection to our north. Shortwave troughs rotating in the westerly upper flow may enhance convection across the west. The question remains on how long the ridge will keep the best chances of showers or thunderstorms well to our northwest. As we head into the weekend and early next week, isolated to scattered diurnal convection will be possible mainly across the high terrain. Temperatures will average around 10 to 19 degrees above normal with highs in the 70s to the mid 80s and lows in the mid 50s to mid 60s. Forecast Confidence Levels: Moderate && .AVIATION /00Z WEDNESDAY THROUGH SUNDAY/... As of 650 PM EDT Tuesday... Isolated showers continue to fade across the region this evening and expect most will have dissipated after sunset. This should lead to mainly VFR this evening with perhaps a few spots seeing enough strato-cu for MVFR cigs at times over the mountains. Any showers or storms closer to the front to the north should weaken with perhaps an isolated shower making it to the KLWB vicinity after dark. Otherwise weak cold front to the north will stall out overnight before lifting back north on Wednesday. Flow should become light northwest later tonight making for weak upslope flow into early Wednesday. Expect this will keep clouds around at the higher terrain in light upslope flow espcly KBLF/KLWB later tonight. Fog potential remains uncertain given drying in spots today but also isolated heavier downpours from earlier. Appears may see some stratus across the mountains evolve into sub-VFR vsbys in fog. However question remains with residual cloud cover elsewhere as more canopy could reduce radiation cooling aspects late. Does appear that KBCB may see enough clearing to drop to IFR/LIFR after earlier showers with KLWB possibly seeing the same. Fog should be a bit more patchy out east with overall MVFR expected although KLYH could go lower right before daybreak where clouds look even less. Any fog/stratus will dissipate by mid morning Wednesday. However lingering upslope flow could keep sub-VFR cigs lingering around KBLF until afternoon. Otherwise expect diurnal heating to generate some MVFR cumulus mid morning that will lift to VFR during Wednesday afternoon. Any shower threat appears quite isolated so wont include mention as well. Winds will generally be light westerly with no significant impact to aircraft operations. Average confidence most elements, below average for IFR vsby/cigs overnight. Extended Discussion... High pressure at the surface and aloft will dominate the area into late this week. A front approaching the Mid Atlantic region on Friday may generate scattered MVFR showers and thunderstorms. High pressure will build in from the north in the wake of this boundary resulting in mostly VFR outside of isolated showers Saturday, and perhaps low clouds within a developing wedge by Sunday. There will also be potential for for late night/early morning fog in the valleys each morning. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH/MBS NEAR TERM...JH/MBS SHORT TERM...KK LONG TERM...KK AVIATION...JH/MBS
Area Forecast Discussion
National Weather Service Topeka KS
1100 PM CDT Tue Oct 2 2018 ...AVIATION UPDATE... .SHORT TERM...(This evening through Wednesday) Issued at 351 PM CDT Tue Oct 2 2018 Warm front has mixed north with gusty SSW winds at most locations and temps in the 80s. Isolated showers were fairly persistent over southeast Kansas and could see one or two reach east central Kansas before sunset as ML CAPE lingers but a lack of near-surface ascent should allow for a dry evening. Models are consistent with modest isentropic upglide developing from 310 to 315 K as the low- level jet increases overnight in response to surface cyclogenesis moving across the Dakotas as the strong upper wave over southern British Columbia this afternoon pushes east. Neither moisture profiles nor instability aloft are impressive however. A weak wave in the west-southwest flow aloft could pass through and aid in ascent, but at this point am not expecting anything more than very isolated activity in the 6Z-15Z window. The low-level jet should allow for fairly steady overnight temps and increasing surface winds, with a very warm and breezy to windy Wednesday before the front associated with the aforementioned wave enters from the north-northwest late in the afternoon. Models continue to be rather dry with this front through the afternoon though ML CIN values do drop to around 50 J/kg. With current dewpoints in a well-mixed boundary layer to the south around 70 F, will err on the side of caution with a less-capped atmosphere and add a small chance for thunderstorms late in the afternoon. ML CAPE around 1500 J/kg and 25 kts of deep-layer shear suggest a small severe weather potential in wind and hail until early evening when instability diminishes. .LONG TERM...(Wednesday night through Tuesday) Issued at 351 PM CDT Tue Oct 2 2018 The front becomes more zonal into the evening with more coverage expected as moisture convergence increases. Nearly zonal flow aloft could lead to some training and some locally heavy rainfall though some continued southerly movement to the boundary is anticipated. East to northeast surface winds behind the front and the approach of the weakening upper wave off southern California coast this afternoon leads to a better isentropic lift scenario for decent precip chances Thursday into Thursday night. The next upper wave brings the front north late Thursday night with steady to rising temp potential and another front in the vicinity Friday into Friday night. Discrepancies in the front`s position Friday continue to vary considerably but severe weather potential could develop in some solutions. The front likely will be to the southeast by Saturday though southwest flow aloft downstream of a developing Four Corners low keeps some potential for elevated precip in place for much of the weekend. Much of the area should be back in the warm sector for Monday with another frontal passage possible Monday night into Tuesday as a wave ejects northeast from the southwest trough. There are many questions for where and when the best excessive rain potential will be through these periods, but several rounds of moderate to heavy rainfall appear possible. && .AVIATION...(For the 06Z TAFS through 06Z Thursday) Issued at 1100 PM CDT Tue Oct 2 2018 Not a lot of change in forecast thinking. With the RAP and NAM showing the pressure gradient increasing through sunrise and surface winds already gusting, think it is less likely the boundary layer would decouple causing LLWS. Otherwise models continue to show a stratus deck developing by sunrise. Confidence in CIGS being below 3 KFT is marginal so will keep a VFR forecast. Although is is not impossible the status could come in between 2 and 3 KFT. Some of the 00Z guidance suggests convection along the front may hold off until it is south of the terminals. Think there is some potential for TS in the evening, so will include a VCTS. && .TOP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...65 LONG TERM...65 AVIATION...Wolters