Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/18/21

Area Forecast Discussion
National Weather Service State College PA
1132 PM EDT Fri Sep 17 2021 .SYNOPSIS... Mostly cloudy and relatively cooler late-week conditions will break for an unseasonably warm start to the weekend. There may be a shower or thunderstorm in spots, but most of the time will be dry. Rain-free conditions are expected Sunday through Tuesday with comfortable humidity. Rainfall is probable for the start of fall, followed by a noticeable cool down into the end of next week. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... A weakening mid level vort max lifting across western NY state will prolong the chance of an isolated shower through late tonight across northern Pa. HREF and latest HRRR both target Mckean, Potter, Elk and Cameron counties for the best chance of a shower overnight. For most of the region, expect a warm and tranquil night under surface ridge axis. Mostly clear skies, a calm wind and relative high soil moisture will promote areas of valley fog. Latest guidance continues to support lows in the 60s, some 10-15F above normal. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... A weak cold front will push southeast across the forecast area Saturday afternoon and evening. The parent shortwave is progged to pass well north of Pa, so large scale forcing should be weak. Thus, expect only widely scattered afternoon showers along thin ribbon of higher precipitable water values coincident with the front. So, while an isolated brief downpour is possible, the warm air aloft will make it difficult to generate deep convection and thunder. This looks especially so across the southern part of Pa, where capping inversion in model soundings looks strong enough to suppress any convection. Will still leave in the mention of thunder for the northeast quadrant of the forecast area per SPC outlook, but the threat is pretty weak. Mixing to 850mb, where progged temps are around 15C, should support highs of 75-80F over the Allegheny Plateau and 80-85F elsewhere. Surface ridging building across Lake Erie will lead to drying Saturday night, dropping dewpoints into the low 50s near BFD, and nudging them down into the low 60s in the SE piedmont. && .LONG TERM /SUNDAY THROUGH FRIDAY/... High pressure sliding across New York will lead to a pleasant Sunday as high temperatures warm into the low 70s. Upper ridging across the Atlantic coast should ensure dry and warm weather early next week. However, an easterly flow circulating around high pressure over New England should result in slightly cooler conditions than this weekend and could result in patchy late night stratus over the central mountains. An examination of latest ensemble output suggests the operational GFS is likely too fast with approaching upper trough and cold front during midweek. Based on ECENS and GEFS timing, have undercut NBM POPs a bit on Wednesday and focused the best chance Wed night into early Thursday. Models support an anafront structure, with the bulk of the rain falling behind the front in region of fgen forcing beneath right entrance of upper jet streak. Med range guidance all supports cool and mainly dry conditions late next week, as Canadian high pressure builds southeast into the area. && .AVIATION /04Z SATURDAY THROUGH WEDNESDAY/... For the late evening, backed off on low clouds and fog a bit, given current trends. IPT has a low CIG so far, but no fog. Western areas may just have enough breeze above the ground to limit low CIGS and fog. Isolated thunder across southwestern NY state, but these are lifting northeast, away from BFD. Thus just minor changes at this point. Earlier discussion below. For the 00Z TAF package, looking at mainly VFR conditions this evening. Expect low clouds and fog later tonight into Saturday morning, before conditions improve by the afternoon, much like today. Less chance of fog and low clouds Sunday and Monday mornings, as the airmass dries out some. Outlook... Sun-Mon...Mainly VFR conditions. Tues..SHRA/TSRA possible, mainly late. Wed...Showers likely. && .CLIMATE... Fall Equinox 2021 will be at 3:20 PM (1920 UTC) on Wednesday, September 22. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Steinbugl NEAR TERM...Fitzgerald SHORT TERM...Fitzgerald/Steinbugl LONG TERM...Guseman/Fitzgerald AVIATION...Martin CLIMATE...Steinbugl
Area Forecast Discussion
National Weather Service Indianapolis IN
1110 PM EDT Fri Sep 17 2021 ...Updated Aviation Discussion... .Forecast Update... Issued at 934 PM EDT Fri Sep 17 2021 Had lower temperatures several degrees at the onset, but with dew points in the middle to upper 60s and with stagnant airmass, overnight lows in the 60s still look good. Also, patchy shallow fog still looks like a good bet with mostly clear skies, very light to calm winds and shallow moisture per HRRR soundings. && .Short Term...(This evening through Saturday night) Issued at 259 PM EDT Fri Sep 17 2021 A warm and humid final weekend of astronomical summer is expected across central Indiana as a fairly stagnant pattern remains in place across the area. This afternoon, some slightly congested cumulus is noted on satellite imagery, while weak convective plumes occasionally show up on radar and quickly die off in the weakly unstable and somewhat capped airmass. In the absence of any substantial additional support, expect this to continue through the few hours after peak heating, but chances that anything sustains itself are low. Will carry an unmentionable 14 pop through 00Z and then go dry overnight. Expect that the weak scattered showers/isolated storms to our south associated with a weak impulse on the periphery of the Nicholas remnants over the southern Plains/western Gulf states will weaken significantly and at least partially dissipate diurnally before making progress into the area. Saturday looks to be a repeat of today, with weak convective plumes attempting to fire and failing, especially given that heights rise a bit which may be enough to suppress even these weak plumes in the marginally unstable airmass. Cannot entirely rule out possibility that a very isolated shower sustains itself briefly over some portion of the area, but even a 20 pop seems like overkill given the vast majority of the area is a solid bet to remain dry. Highs tomorrow should be not that dissimilar from today, in the mid to upper 80s, as despite the slight rise in low level thicknesses and temps, surface flow will become more northeasterly Saturday as broad surface high pressure passes through the Great Lakes. Tonight, in the stagnant and humid airmass, with winds likely to go calm in many areas, and skies looking to be mostly clear, with just a bit of high cloud, expect some patchy fog formation again, particularly in favored rural and low lying areas. Will carry a mention in the grids. Some shallow dense fog isn`t entirely out of the question, but confidence is low at this time, and will likely depend on just how clear skies get. && .Long Term...(Sunday through Friday) Issued at 259 PM EDT Fri Sep 17 2021 Remnants of Nicholas followed by a seasonably strong cold front will be primary concerns for the long term forecast. Sunday will begin warm and rather humid for mid September with afternoon temps reaching mid to upper 80s along with surface Tds in the mid 60s. Water vapor shows upper circulation over east Texas this afternoon with deep moisture across the south. This moisture will finally advect north and begin to arrive across central Indiana late Sunday afternoon and expand northward Sunday night and Monday. Models still trying to generate some isolated convection on northern periphery of Theta E axis Sunday afternoon so will continue a slight chance PoP for now over the far southwest before expanding pops to entire area Sunday night. PWATs will climb to over 2 inches by Monday as this tropical moisture surge and upper low drifts north. These values are near or above climatological records for mid September. Sharp short wave trough and DPVA to move through the area Sunday night and Monday which will likely make for a dreary and soggy start to the work week. Efficient rain processes in this tropical airmass could lead to 1 to possibly 2 inches of rainfall over south central Indiana Right now models are focusing heaviest rain axis south of our area but much uncertainty remains. Fortunately our recent dry spell and low water levels on area streams and rivers should keep flood threat in the low probability range. Deeper moisture from Nicholas remnants will begin to lift northeast as a strong cold front associated with a deepening mid level trough approaches on Tuesday. Details on timing between these two systems and rain chances between them still to be worked out but break in rain possible Monday night into Tuesday before cold front moves through later Tuesday. This front has potential for severe weather and locally heavy rainfall given lingering PWATs in the 1.5-2" range and strong dynamics/kinematics indicated along with favorable afternoon peak heating timing. However, lingering cloud cover may lead to a conditional threat within a low cape modest shear environment. Much too early for any confidence or actionable details but certainly worth watching and noting at this projection time. A taste of Fall follows this front for the remainder of next week as high pressure, dry weather and seasonable temperatures settle in. && .Aviation...(06Z TAF Issuance) Issued at 1109 PM EDT Fri Sep 17 2021 IMPACTS: - MVFR and worse conditions in fog 06z-12z, especially at KBMG. DISCUSSION: Mostly clear skies, very light to calm wind and dew points in the middle to upper 60s support MVFR and worse fog potential overnight over at least KHUF and certainly KBMG as has been the case the last few nights. That said, soundings showing the low level moisture to be very shallow and thus fog will lift quickly around sunrise. After the fog threat is over, should only see at best scattered diurnal cu this afternoon. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ Update...MK Short Term...Nield Long Term...Lashley Aviation...MK
Area Forecast Discussion
National Weather Service Phoenix AZ
410 PM MST Fri Sep 17 2021 .UPDATE... Updated Aviation && .SYNOPSIS... A weak weather system will move through the region today into Saturday bringing increased cloud cover, somewhat cooler temperatures, and scattered showers and thunderstorms. Although many locations may not see measurable rainfall, gusty winds will be possible with any thunderstorm. Starting Sunday, dry conditions with temperatures hovering near to slightly above average should be common through at least the first half of next week. && .DISCUSSION... An upper low just off the SoCal coast shows well on RAP mesoanalysis and water vapor imagery. Southerly flow ahead of the low continues to draw tropical moisture northward into the Southwest leading to more clouds and chances for scattered showers. Moisture has noticeably increased since this time yesterday with surface dew points up by 30 to 40 degrees in Yuma and up 5-10 degrees in Phoenix. Comparison between the 17/12z and 16/12z soundings shows the moistening trend is not limited just to the lowest levels as PWATs increased from 0.73" to 1.22" in the last 24-hours. Current radar suggests the next uptick in activity is underway in southwest AZ and should continue through this afternoon and evening as atmospheric moisture increases. Isolated embedded storms will occur this afternoon, especially south and west of Phoenix, and along the Colorado River, where instability is amplified by daytime heating and colder air aloft. Today`s K1Y7 soundings, objective analysis trends, and hi-res guidance all indicate an axis of 500- 1000 j/kg of CAPE developing along the lower Colorado River area and over mostly open desert of western AZ between I-10 and I-8. This kind of instability will be more suitable for producing storms capable of producing localized 40-55 mph wind gusts and higher precipitation rates of 1.00 in/hr. Blowing dust cannot be ruled out either with any stronger wind gusts in the aforementioned areas IVO Gila Bend through Quartzsite. Chances for blowing dust are 30% in that area and less than 10% elsewhere. Activity will shift eastward through tomorrow with additional periods of showers/storms as the upper low ejects towards into the southern Great Basin. Timing and location of these later rounds is uncertain but latest HREF indicates a round of showers and storms to develop very late tonight-early Saturday morning between Phoenix and the Colorado River, and then again Saturday afternoon and evening across most of south-central Arizona. Any convection will retain mentioned threats for wind gusts and rain rates. However, moisture and dynamics are not still not supportive for widespread high PoPs or heavy rain. PoPs oscillate between 10-25% this afternoon through Saturday for most areas with isolated pockets of 30-35% PoPs. NBM 24-hr QPF probabilities are equally unimpressive with only a 25-35% chance for 0.01 inches and a 15% chance for 0.20 inches or more at nearly any point in the forecast area. Many places will miss the rain entirely. Decreasing heights, moisture, and clouds will keep temperatures 4 to 7 degrees cooler compared to recent days. Highs are forecast to reach 98-102 degrees today and hover around 100 degrees through the weekend. Temps will undergo a very modest warming trend of a few degrees by the end of next week. && .AVIATION...Updated at 2310Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: Showers and storms should remain well removed southwest of the Phoenix area this evening such that even chances for outflow winds are less than 10-20%. There may be substantial variability in wind directions overnight as the tendency for east winds battles the pressure gradient. In addition, late night/early morning elevates showers in western AZ could create an early shift to westerly winds mid morning. Models still suggest a 20% chance of showers and storms approaching the metro Saturday afternoon, however confidence in extent of TSRA still precludes any mention yet. Maintained a VCSH mention with gusty winds as the most likely impact on operations. Southeast California/Southwest Arizona including KIPL and KBLH: Thunderstorms passing near KBLH through early evening will be the greatest weather threat with erratic gusty winds. While a south component is favored, highly variable directions are possible. Otherwise, SCT mid/high clouds will be common through Saturday as shower chances diminish this evening. Any further SHRA/TSRA overnight should remain east of the terminal footprint. More tranquil conditions at KIPL with winds likely following diurnal trends experienced the past 24 hours. && .FIRE WEATHER... Sunday through Thursday: Lingering moisture across eastern Arizona on Sunday may lead to some isolated showers and storms across the high terrain, but drying conditions will be seen elsewhere. This drier air will then dominate through at least the middle of next week as high pressure strengthens across the region. High temperatures through the period will be near to slightly above normal. Afternoon RH values will start off mainly between 20-25% on Sunday from south-central Arizona and areas east before lowering to 10-15% starting Monday. Overnight RH recoveries will generally range from 25-40% through most of the period. Winds will be fairly breezy on Sunday, but generally will remain light while directions favor local diurnal/terrain influences through the rest of the period. && .SPOTTER INFORMATION STATEMENT... Spotters should follow standard reporting procedures. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ DISCUSSION...12 AVIATION...18 FIRE WEATHER...Kuhlman
Area Forecast Discussion
National Weather Service Riverton WY
519 PM MDT Fri Sep 17 2021 .SHORT TERM...(This evening through Saturday night) Issued at 210 PM MDT Fri Sep 17 2021 Mostly clear skies with some high clouds pushing into northern Wyoming today. Weak upper-level high pressure with mid-level zonal flow will keep things dry through early Saturday morning. The surface pressure gradient due to recently departed system and low pressure in NW Montana has added in strong south winds late this morning for northern Johnson County and some locations in the Bighorn Basin. The winds in these location should decrease this afternoon, while flow becomes more southwesterly with gusts over 30 mph from southwest WY into central WY and in the higher elevations. Combined with low afternoon humidities, critical fire weather conditions continue for much of the state. High resolution models such as the HRRR are showing that portions of the Wind River Basin and Bighorn Basin may not mix out though this afternoon due to the remaining cool air, or that it may take until 8 to 9 pm for west winds to mix down. Mid-level flow becomes more southwesterly overnight as the west coast trough digs and the upper-level high over southern CO continues. This pattern will actually bring moisture with weak instability from Utah into western WY Saturday, increasing clouds and bringing a chance of showers to far SW WY by noon. Southwest wind will increase also around noon Saturday with areas from southern into central WY seeing winds 20 to 25 mph with gusts over 30 mph. Low humidities will push northeast so that critical fire weather area should shift more toward Natrona into Johnson County, and elevated conditions across the Bighorn Basin. Much of western WY will have a chance of showers and thunderstorms Saturday afternoon and early evening, with some showers possibly also moving from Dubois area to the northeast. Latest model trends show that some areas could see around 0.25" of rain, especially in the Wind River Mountains. At this time, just expecting typical thunderstorms with brief heavy rain, small hail, and gusty winds. Interesting how this area of showers and thunderstorms has increased over the past couple of days as the forecast time frame comes closer. Expecting lingering showers through midnight across central WY. Early Sunday morning will see clouds increasing across northwest WY as the PacNW trough starts moving eastward. Saturday night may see some breezy wind overnight, and combined with residual cloud covers, overnight temperatures could be more mild than has occurred with the clear skies the past few nights. .LONG TERM...(Sunday through Friday) Issued at 201 PM MDT Fri Sep 17 2021 Sunday will bring the NW trough into the region, with a significant cold front sweeping through during the day Sunday. The trough will bring a season-changing from across the state, starting Sunday morning across the NW Parks, before briefly stalling. The main push then sweeps through Sunday evening and night, bringing much colder temperatures. The front will bring a good chance for precipitation to the region, bringing rainfall to most areas. Midlevel temps still show good cold air moving through Sunday night, so some precip will be snowfall for the higher elevations of the western mountains and the Parks. Some accumulation is possible for the highest peaks, but that will still be limited by amount of time of precip and somewhat warm grounds still. The cold pool then settles across WY, bringing the coldest night in a long time, with most areas near or below freezing. The trough sweeps east quickly Monday, with ridging taking back over for midweek. Temperatures recover quickly, reaching back into the 60s and 70s by Wednesday. A weak shortwave looking a bit more likely from the north on Thursday will bring temps down just a bit, but will otherwise be a dry and tranquil passage. && .AVIATION...(For the 00Z TAFS through 00Z Sunday) Issued at 519 PM MDT Fri Sep 17 2021 VFR conditions look to continue throughout the TAF period. Gusty winds at KBPI, KCPR and KRKS should diminish between 01Z-02Z. Gusty winds look to be around again tomorrow starting between 17Z-19Z for several locations. KCPR may see gusty winds as early as 14Z. Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for the latest information on smoke, icing, and turbulence forecasts. && .FIRE WEATHER... Issued AT 205 PM MDT Fri Sep 17 2021 Dry south-southwest flow with mostly clear skies continues the red flag warnings over much of western and central Wyoming today. Some areas are marginal with elevated conditions due to uncertainty of winds, such as parts of the Wind River and Bighorn Basins. Higher elevations will see RH values drop below 20 percent along with gusty winds. Dry air remains in the higher elevations overnight as the winds decrease for poor humidity recovery. Clouds and mid-level moisture will increase over southwest WY Saturday morning, bringing a slight chance of showers to far SW WY by noon Saturday. As the moisture moves to the northeast during the day, showers and thunderstorms are expected over much of western WY, especially from the Wyoming Range toward the Wind Rivers. Some areas may see more than 0.25" of precipitation by Saturday evening. Latest models are showing areas of showers moving across Sweetwater County during the early evening hours. This activity should keep RH values above critical, thus moving the drier areas to the northeast. Critical fire weather conditions then are only expected from Natrona County into Johnson County Saturday afternoon, with elevated conditions around the Bighorn Basin. Showers will linger through midnight across central WY. Winds will remain breezy Saturday night into Sunday morning as a strong storm system approaches from the west-northwest. Expect a strong cold front moving northwest to southeast Sunday afternoon through late Sunday, bringing more showers and some mountain snow into Monday. && .RIW WATCHES/WARNINGS/ADVISORIES... Red Flag Warning until 8 PM MDT this evening for WYZ277>279-285- 286-288-289-300-414-416. Red Flag Warning until 8 PM MDT Saturday for WYZ280-281. && $$ SHORT TERM...McDonald LONG TERM...Straub AVIATION...Clayton FIRE WEATHER...McDonald
Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
700 PM MDT Fri Sep 17 2021 .UPDATE... Issued at 651 PM MDT Fri Sep 17 2021 Forecast remains mostly on track. Did add areas smoke in the short term as a wildfire near Crawford NE has reduced visibility in southwestern SD and the Black Hills region. HRRR near surface smoke model keeps some smoke in the region at least through Saturday evening. May have to reassess for Sunday as southwesterly flow continues until around Sunday evening. && .DISCUSSION...(This Evening Through Friday) Issued at 144 PM MDT Fri Sep 17 2021 Latest analysis shows a low amplitude upper ridge building over the region. At the surface, a tight pressure gradient between high pressure to the southeast of the forecast area and a strengthening lee side trough over Montana is producing gusty southerly winds across northeastern Wyoming and western South Dakota. The winds will diminish a bit this evening, however areas of breezy southerly winds will continue overnight. Low temperatures tonight will be relatively mild, mainly in the mid-40s to lower 50s. With high temperatures 10-20F warmer than average on Saturday, gusty west to southwest winds are expected due to very deep boundary layer mixing, especially over northeastern Wyoming on Saturday afternoon. The southwesterly downslope component to the winds will also lead to very low relative humidity over northeastern Wyoming and much of western South Dakota on Saturday afternoon. For Sunday night into Tuesday, the upper trough will cross the northern plains. The relatively quicker movement of the system will lead to less moisture return and precipitation over the forecast area than previously indicated. A sharp cold front will cross the area on Sunday night followed by potentially strong/gusty northwest winds. Thermal profiles suggest a chance of snow possible in the higher Black Hills with little to no accumulation. The second half of next week will feature seasonable, typical mostly dry Fall weather. && .AVIATION...(For the 00Z TAFS Through 00Z Saturday Evening) Issued At 534 PM MDT Fri Sep 17 2021 Smoke from a wildfire in Nebraska will reduce visibility in areas around KRAP this evening and Saturday, though visibilities should stay above MVFR. VFR conditions are expected through the period. && .FIRE WEATHER... Issued at 144 PM MDT Fri Sep 17 2021 Gusty southerly winds and minimum afternoon relative humidities in the upper teens to mid 20s will lead to elevated fire weather conditions. However, the relative humidity will drop around 15 percent over the western half of fire weather zones 314 and 315 in Campbell County Wyoming, leading to critical fire weather conditions in that area during the rest of this afternoon into early evening. On Saturday, gusty west to southwest winds, as well as very dry air, will create critical fire weather conditions over northeastern Wyoming and much of western South Dakota. Poor relative humidity recovery is also expected on Saturday night. Elevated fire weather conditions are possible on Sunday ahead of a cold front for Sunday night. This cold front will be followed by gusty northwest winds as well as a chance of showers. && .UNR WATCHES/WARNINGS/ADVISORIES... SD...Red Flag Warning from 10 AM to 9 PM MDT Saturday for SDZ319>333. WY...Red Flag Warning from 10 AM to 9 PM MDT Saturday for WYZ314>318. Red Flag Warning until 8 PM MDT this evening for WYZ314-315. && $$ Update...Dye DISCUSSION...10 AVIATION...Dye FIRE WEATHER...10