Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/01/17

Southcentral and Southwest Alaska Forecast Discussion
National Weather Service Anchorage AK
459 PM AKDT Thu Aug 31 2017 .ANALYSIS AND UPPER LEVELS... Two upper level lows dominate the weather across the mainland with one low just south of the Seward Peninsula, and a second low over Kodiak Island. While the upper low near the Seward Peninsula is supporting light scattered showers across the Kuskokwim Delta. Across Southcentral, there is much more low level support for widespread showers with the remnants of a front, along with broad onshore and upslope flow. The afternoon sounding indicates fairly steep lapse rates and a saturated atmosphere, which is likely allowing for some spillover precipitation currently and preventing completely dry conditions in downslope areas. Meanwhile, fairly dry conditions persist across the Bering with broad northerly flow. && .MODEL DISCUSSION... The NAM remains the model of choice for both the east and west domains and models are in good agreement in the short term for synoptic conditions. The NAM and WRF are particularly doing a good job of capturing the gap winds through the Alaska Peninsula and associated mountain wave dynamics. The HRRR is capturing the low level convergent winds well and is therefore capturing the rain showers over Anchorage this afternoon. && .AVIATION... PANC...VFR conditions will persist even as light showers continue to fall into the evening hours. While strengthening down inlet flow has bent the surface southeasterly Turnagain arm winds away from PANC with light northwesterly surface winds taking over, wind shear may still be a concern on the approaches and departures. Southeast surface winds are likely to push back in to PANC late afternoon through the evening. && .SHORT TERM FORECAST SOUTHCENTRAL ALASKA (Days 1 through 3)... Rain showers will continue across the gulf coast and Susitna Valley through the majority of the overnight hours. In the meantime, cross barrier flow over the Chugach Mountains will weaken and allow for scattered showers to develop across Anchorage and the Matanuska Valley. By Friday morning, a combination of southeasterly winds out of Turnagain Arm will combine with southwesterly winds in Cook Inlet (up-Inlet flow) to create a convergent boundary over west Anchorage. Models are struggling on where the mesoscale banding will set up as the NAM and GEM show a negatively tilted upper level axis which would push the banding west of Fire Island. Regardless, early Friday morning looks wet with the potential that the morning hours could see steady light to moderate rainfall. A rapidly developing low pressure system will develop south of the Alaska Peninsula Saturday morning and quickly push a gale force front into the western gulf by Saturday afternoon. This front is expected to bring moderate to heavy rainfall to Kodiak Island and the gulf coast through the weekend. However, interior locations will remain largely on the dry side as impressive cross barrier flow (35-50 kts) should downslope much of the precipitation as it interacts with the coastal mountains. && .SHORT TERM FORECAST SOUTHWEST ALASKA (Days 1 and 2)... An upper level low centered over Bristol Bay, which is embedded within a longwave trough covering most of mainland Alaska, is bringing widespread cloud cover and rain to Southwest Alaska east of Bethel. This system will slowly move east bringing a quick break in the precipitation overnight into tomorrow. Cooler air filtering down from the north on the backside of this system combined with partial clearing will allow temperatures to dip below 40 degrees for most locations tomorrow morning, with low to mid 30`s expected for locations in the Kuskokwim River Valley. Another upper level low swings down the coast by Friday evening bringing another round of steady rain for the area starting in the Y-K Delta Friday night and spreading east and south through the day on Saturday. && .SHORT TERM FORECAST BERING SEA/ALEUTIANS (Days 1 and 2)... Strong northerly flow over the eastern Bering will begin to taper off tonight, though wind gusts may still reach gale force coming out of channeled terrain on the Pacific side of the eastern Aleutians and southern AKPEN. A major change in the overall pattern will begin to take shape tomorrow as a low over Kamchatka will move east into the Bering Sea by the afternoon. At the same time, a surface low will form to the south of the Western Aleutians and remnants from former Typhoon Sanvu will get pulled up into a strong North Pacific jet stream and ejected northeast towards the island chain. Models are showing these three systems merging together by Saturday night into a rapidly intensifying low pressure system about 250 miles southeast of Cold Bay. A strong 175 kt jet streak will aid in developing this system into a well developed extra-tropical cyclone by Sunday, with all models showing the surface pressure bottoming out at or below 970 mb on Sunday afternoon. Previous model runs were inconsistent with the low placement and track but seem to be coming into better agreement, at least through Sunday. Impacts from this system will be heavy rain along most of the central and eastern Island chain aided by upslope flow. Winds will also be very strong but, due to the distance of the low center from the AKPEN and warm air advecting up from the south, we are not expecting this to be a storm force low with sustained winds remaining below 48 kts across a majority of the area. Large swells are expected though, with long fetch southerly winds leading to seas above 20 ft for open water locations south of the AKPEN and southwest of Kodiak. && .LONG TERM FORECAST (Days 3 through 7)... The big question going into next week is what will happen with the rapidly intensifying low south of the Aleutians. Depending on how far south the trough digs it may tap into tropical moisture and bring a long fetch of moisture to southern Alaska. Most current operational runs and ensembles are indicating this to be the case which would mean Monday and Tuesday would see steady, heavy rain, primarily along the north Gulf coast. However, there are still differences in where the low will setup and the trough may not dig far enough south. && .AFC WATCHES/WARNINGS/ADVISORIES... PUBLIC...NONE. MARINE...NONE. FIRE WEATHER...NONE. && $$ SYNOPSIS AND MODEL DISCUSSION...ELN/JA SOUTHCENTRAL ALASKA...MC SOUTHWEST ALASKA/BERING SEA/ALEUTIANS...KVP LONG TERM...PS
Area Forecast Discussion
National Weather Service Wakefield VA
916 PM EDT Thu Aug 31 2017 .SYNOPSIS... A cold front will drop across the area late tonight, becoming stalled across North Carolina on Friday. The remnants of Harvey will shunt tropical moisture along the boundary, lifting it back north as a warm front Friday night through Saturday. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... 9 PM Update...Afternoon forecast handling things pretty well. Have made a few adjustments to POPs/Wx across NE NC where persistent showers have been more widespread than earlier thought. These showers are trending toward the coast, and look to be offshore before 03Z. Attention then turns to moisture trying to move northward ahead of the remnants of Harvey. Hi-res models have been inconsistent the last few runs regarding how quickly significant precip comes northward. Surge has been inhibited the last few hours by significant tstm development now exiting the Carolinas/GA coastline. So, current forecast of gradual increase in POPs after 06Z looks good and have not made changes after that time. One aspect of the precipitation that will need to be monitored is the suggestion from recent HRR runs that showers/tstms fire after 06Z as cold front reaches deeper moisture over SE VA/NE NC. This not covered well in afternoon forecast, and will monitor for another hour, and see if this trend persists before updating. Temps appear on track as most cooling expected late tonight after cold frontal passage. ...Previous Discussion...Latest weather analysis features weak high pressure in places along/just offshore of the Mid- Atlantic coast. To the north, a strong sfc cold front continued to drop across the northeast and Ohio River Valley toward the Mid- Atlantic region. Meanwhile, to the South, T.D. Harvey was located over the lower Miss Valley, sliding NE toward the mid- south region. Radar coverage has been quite light today, owing to weak forcing and dry mid-levels. Accordingly have dropped off pops a bit across much of the area through early evening. Slow increase in sky cover continues late this aftn into this evening, as better slug of overrunning moisture/WAA arrives from the SW out ahead of the lead shortwave from Harvey`s remnants. Pops will bump into 30-50% range south, 20% central VA. Given increasing PW values and likelihood of numerous weak disturbances pushing through, will go with areal coverage (iso-sct) wording through the night. Time-lagged HRRR and RAP are in general agreement of this solution through midnight. Showers become likely late along and south of the US-58 corridor. Lows ranging through the 60s to near 70 SE. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/... Weak cold front will drop down acrs the region early Fri morning, before becoming stalled south of the area acrs NC on Fri. Meanwhile, low pressure from the then post- tropical remnants of Harvey will lift NE fm nrn MS northeast into cntrl KY tonight into Sat morning, eventually lifting up into the northeast and getting absorbed into NE CONUS upper trough finally being shunted offshore late in the weekend. Overall, 12z models continue with a flatter and relatively progressive solution, with the lead shortwave and onset of rainfall. First batch of showers push offshore in the morning, before showers become more widespread from the late morning into Friday night, as increasing overrunning moisture pushes across the area as high. POP remains in likely range Fri morning (SW), before spreading NE across the rest of the local area into Fri aftn and evening. Most widespread rainfall looks to be later Fri aftn thru Sat morning, with rain potentially tapering off a bit quicker acrs the west on Sat. morning, as nose of mid- level drying nudges back in from the southwest. QPF in the 1.0 to 2.0" range likely acrs the region thru Sat night. Highs will range fm the lower to mid 60s NW, to the lower to mid 70s SE VA and NE NC on Fri, moderating a bit back closer to normal on Sat into the 70s to lower 80s. Concerned for potential for some clearing in the warm sector behind the system Saturday aftn. In the event of some partial clearing, weakening/sheared out remnants of Harvey along with veering low- level flow could provide enough support for isolated to scattered convection. Area of concern is across SE VA/NE NC, where a marginal risk remains in place. Highs in the 70s to low 80s across the SE. && .LONG TERM /SUNDAY THROUGH THURSDAY/... Overall, the GFS and the ECMWF are in pretty good agreement with the overall synoptic pattern from Sunday through Thursday. Both models show the low pressure system associated with the remnants of Harvey pulling away from the coast on Sunday morning and high pressure building into the region by Sunday night. The GFS is a little slower than the GFS and NAM and would suggest that there is still a chance for some shower as the upper trough cross the Delmarva. So have kept a slight chance of shower through midday for the upper trough passage. Temperatures should Sunday afternoon should be in the upper 70s to lower 80s Behind the trough, upper level ridging returns with the surface high. This high slowly retreats to the NE from Monday into Tuesday night, while providing dry weather through that period. Expect a slow warm up in temperatures with readings in the low to mid 80s Monday and mid to upper 80s on Tuesday. The next cold front will arrive later Tues night into Thursday. Ahead of this front, the models continue to show a good tropical plume of moisture sliding northward into the Mid-Atlantic states. This additional moisture could lead to some heavier showers as the front slowly moves into the region. With the cloudy conditions expect cooler temperatures in the 70s and depending on the size and extent of the rain shield, could even see readings maybe only in the upper 60s. From Thursday forward however the models diverge pretty dramatically as far as will the front move through the area like the GFS or stall and retrograde like the ECMWF. Some of this is also a factor in how the model deals with Irma and its approach, which the models are very different in handling. For now, have gone with a little more of a blend of the solutions and kept the front stalled along the coast on Thursday, keeping the chance for showers ongoing, but confidence at this point in time is much lower than the forecast for Sunday through Wednesday. && .AVIATION /01Z FRIDAY THROUGH TUESDAY/... VFR conditions conditions are expected through the first half of the night to start the forecast period. A stray shower or thunderstorm also cannot be ruled out overnight at ECG/ORF/PHF. MVFR ceilings and the threat for more widespread showers works in from the south by Friday morning. Expecting widespread MVFR to potentially IFR ceilings at all of the southern TAF sites, ECG/ORF/PHF, Friday morning lasting through the remainder of the forecast period. Sub- VFR conditions and showers will be possible at RIC by Friday afternoon. A cold front will drop across the region late tonight into early Friday with winds veering to the north/northwest overnight. Outlook: Sub-VFR conditions will be likely at all TAF sites late Friday through Saturday as moisture from Harvey pushes across a stalled frontal boundary. Dry weather and VFR conditions are expected Sunday afternoon through Monday as high pressure builds into the region. && .MARINE... Latest surface analysis centers high pressure offshore the Southeast coast with tropical depression Harvey located over the lower Mississippi River Valley. A cold front was stretching from the Upper Midwest eastward into the Northeast. Flow remains light and variable over the waters, generally at or below 10 knots. Seas have subsided to 2-4 feet. Waves 1-2 feet. The front drops over the waters late tonight into early Thursday morning as the remnant low of Harvey lifts over the Tennessee Valley. The pressure gradient strengthens as high pressure builds over the Great Lakes. As a result, a post frontal surge of north to northeast winds to ~20 knots with gusts of 25 to 30 knots is expected late tonight into Friday morning. Waves build to 2-4 feet and coastal seas again build back to 4-6 feet late tonight/early Friday morning. Only changes made to headlines in the Bay was to extend the upper Bay through early afternoon before high pressure builds southward over the waters. Have raised SCA headlines for the coastal waters, first north of Cape Charles Light late tonight, then south of Cape Charles Light mid morning Friday as seas build to 4-5 feet. The front stalls in the vicinity of northeast North Carolina Friday as the weakening remnant low of Harvey lifts into the Ohio Valley. High pressure extends off the Northeast coast Friday, as flow becomes more easterly with speeds around 15-20 knots in the lower Bay and southern coastal waters. Seas subside below 5 feet in the north Friday, but remain 4-5 feet in the south. Waves in the mouth of the bay 3-4 feet. Guidance still struggling to handle the frontal boundary Saturday as low pressure dissipates over the Ohio Valley. Based on the uncertainty, have held off on extending the SCA headlines into Saturday, but SCA conditions appear likely back in the upper Bay and northern coastal waters by Saturday afternoon as the gradient winds lift northward. Low pressure develops over the Mid-Atlantic Saturday night as a trailing cold front pushes across the waters. Conditions improve Sunday through early next week as high pressure builds in from the west. && .TIDES/COASTAL FLOODING... Water levels remain elevated in the upper Bay this afternoon, but are subsiding to around 1 foot. Additional minor flooding is not anticipated, but a coastal flood statement may be needed for Bishop`s Head as it will approach minor flooding during high tide this evening. Water levels will creep back upwards of 1 to 1.5 feet this weekend as a period of onshore flow is expected Friday through Saturday. Water levels will approach minor flooding thresholds in the Bay Friday and Saturday. Have kept the high risk for RIP currents Friday for Virginia Beach southward to the Outer Banks for shorebreak of 3-4 feet, shore normal wave directions, and northeast winds. Have lowered the Eastern Shore beaches to moderate risk for RIPs. && .CLIMATE... Very cool temperatures expected on Friday (Sep 1st). Record low maximum values may be challenged. One thing to note is that official climate is from 12am LST to 12 am LST (1am EDT-1am EDT) for the calendar date. Fri still appears to be a scenario in which the daily high occurs late tonight (* 1am EDT) with falling temperatures through the rest of the day. In that case, a record low max may not be set even if readings during the late morning and afternoon are below the record vales. The record low max data for Sep 1st is listed below for reference. * Richmond: 68 (1928) * Norfolk: 71 (1915) * Salisbury: 69 (2006) * Elizabeth City: 70 (1967) && .AKQ WATCHES/WARNINGS/ADVISORIES... MD...None. NC...None. VA...None. MARINE...Small Craft Advisory from 4 AM Friday to 6 AM EDT Saturday for ANZ632-634. Small Craft Advisory from 10 AM to 7 PM EDT Friday for ANZ633. Small Craft Advisory from 1 AM to 1 PM EDT Friday for ANZ630- 631. Small Craft Advisory from 7 AM to 1 PM EDT Friday for ANZ638. Small Craft Advisory from 4 AM to 4 PM EDT Friday for ANZ650- 652-654. Small Craft Advisory from 10 AM Friday to 6 AM EDT Saturday for ANZ656-658. && $$ SYNOPSIS...MAM NEAR TERM...MAM/WRS SHORT TERM...MAM LONG TERM...SAM AVIATION...AJB/MAM MARINE...SAM TIDES/COASTAL FLOODING... CLIMATE...
Area Forecast Discussion...Updated
National Weather Service Billings MT
858 PM MDT Thu Aug 31 2017 .UPDATE... An area of thunderstorms continues to push southeast out of southeast Montana and into South Dakota. Winds still look to increase tomorrow morning behind a tonight`s shortwave. Winds at 700mb with the 00z run of the NAM are still approaching 30 kts and with mixing during the day tomorrow could mix to the surface. The current forecast still looks on track. Reimer && .SHORT TERM...valid for Fri and Sat... HRRR model continues to indicate increased smoke moving in from the west behind a departing front this evening and hanging around through the day tomorrow. Today, we have already seen some unhealthy levels of smoke in eastern Montana due to several large fires in Powder River and Custer counties. Isolated to scattered showers and thunderstorms possible as an upper-level shortwave moves through southeastern Montana this evening. Increased northwest winds over the eastern Plains tomorrow has prompted the issuance of a Fire Weather Watch tomorrow afternoon and evening. Expecting humidity levels near 20 percent with gusts up to 30 mph during the afternoon in the Plains. Further west it will be dry and warm again with no appreciable chance of rain and winds look to be lighter than out east. Ridging moves in from the west on Saturday which will bump temperatures into the low to mid 90s, decrease winds, and keep the skies cloud free. Walsh .LONG TERM...valid for Sun...Mon...Tue...Wed...Thu... High pressure ridging will continue one more day Sunday. A strong cold front sweeps across the forecast area late Sunday which will shift the ridge and axis westward over the Pacific Northwest Monday and Tuesday. It is still a bit far out in time on the exact arrival of the front but right now it looks to arrive during the afternoon hours Sunday. Pre-frontal mixing ahead of the front will allow for temperatures be hot ahead of the front on Sunday with temperatures approaching or exceeding records for some locations. Temperatures will be much cooler on Monday and Tuesday, but these readings will actually be about normal for this time of year. Ridging begins to build once again by the middle to end of next week allowing for temperatures to return to above normal readings. Hooley && .AVIATION... Aside from mid and low level smoke moving into the region after 04z skies will be mostly clear through the night. VFR conditions will prevail but some reductions in visibility to MVFR levels due to smoke is possible through 15z. Did not warrant inserting into the TAFs due to low confidence. Northwest winds will increase across the region tonight from 05z to 15z as a front works its way through the region. Dobbs && .PRELIMINARY POINT TEMP/POPS... Fri Sat Sun Mon Tue Wed Thu ----------------------------------------------------------- BIL 061/088 058/093 060/099 059/079 053/080 052/084 055/087 10/K 00/U 00/U 00/U 00/U 00/U 00/U LVM 051/087 050/094 051/098 051/084 044/082 044/086 047/087 10/K 00/U 00/U 00/U 00/U 00/U 00/U HDN 057/088 054/095 057/097 055/082 049/082 048/086 051/089 00/K 00/U 00/U 00/U 00/U 00/U 00/U MLS 063/088 058/094 060/100 057/077 049/079 048/084 052/087 20/K 00/U 00/U 00/U 00/U 00/U 00/U 4BQ 061/087 055/094 059/099 055/078 049/078 048/083 051/087 30/K 00/U 00/U 00/U 00/U 00/U 00/U BHK 059/086 055/092 055/095 053/075 045/075 045/080 048/084 30/K 00/U 00/U 00/U 00/U 00/U 00/U SHR 055/085 052/093 054/099 053/080 046/078 044/082 047/086 20/K 00/U 00/U 00/U 00/U 00/U 00/U && .BYZ WATCHES/WARNINGS/ADVISORIES... MT...Red Flag Warning in effect until 9 PM MDT Friday FOR ZONE 117. Fire Weather Watch in effect from Friday afternoon through Friday evening FOR ZONES 131>133. WY...Fire Weather Watch in effect from Friday afternoon through Friday evening FOR ZONE 274. && $$
Area Forecast Discussion
National Weather Service Charleston SC
945 PM EDT Thu Aug 31 2017 .SYNOPSIS... A warm front will lift north of the region through Friday morning as Tropical Depression Harvey moves across the lower Mississippi Valley. A cold front will approach from the north this weekend. High pressure will then prevail early next week before another front approaches the region during the second half of next week. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... As of 925 PM: Stratiform rainfall was slowly dissipating over the SC Lowcountry, a few new clusters of showers were developing across inland SE GA. The new shower activity appears to be associated with the second round of rainfall, forced by LLVL isentropic lift. I will update the forecast to adjust PoPs, sky, and temperatures. As of 720 PM: Overall, convection has trended weaker across SC over the past half hour, with a few stronger cells along the SE GA coast. The GA activity should push over the coastal waters over the next one to two hours. SC activity should gradually fade. I will update the forecast to update POPs and WX. Previous discussion: Updated POP and Wx grids to account for observed trends with ongoing convection. HRRR and 12Z NSSL-WRF have generally prognosed the behavior and timing of this convection reasonably well, if not a little slower than reality as is typical. Based on trends, the convection should be weakening as it moves offshore of most zones by 01-02Z. Still cannot completely rule out an isolated tornado closer to the warm front and highest low-level helicity. After this line pushes offshore, mostly dry conditions are expected overnight. Increasing low-level jetting will keep temperatures warmer than last night, mainly mid to upper 70s. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/... Friday and Saturday: Southerly flow between the remnants of Harvey inland and Atlantic high pressure will continue to advect deep moisture into the region as a cold front extending from a low pressure system north of Maine sinks south into North Carolina. This pattern supports a chance of showers beginning early Friday, increasing to numerous showers and thunderstorms through the afternoon and evening. Sufficient surface-based CAPE and shear will support some strong to marginally-severe thunderstorms, with greatest potential in northern zones due to closer proximity to the front. Despite continual degradation of Harvey`s remnants, residual lower surface pressure and heights aloft will make it easy for a parent low pressure system in Canada to induce secondary, downstream low pressure formation over the mid-Atlantic states. Guidance suggests this low pressure will slide offshore into the mid-Atlantic coastal waters by Sunday evening as it races northeast. Divergence overhead under the right-entrance region of a passing upper level jet will contribute to the formation of numerous showers and thunderstorms over much of the area Friday night into Saturday, until the bulk of deep-layered moisture shifts offshore Saturday evening. Temperatures through the period will be within 1-2 degrees of normal. Sunday: A relatively drier atmospheric column is expected to fill in behind the low pressure as it departs the mid-Atlantic region. While the majority of precipitation will remain offshore, a few showers or isolated thunderstorms near the coast during the afternoon cannot be ruled out. Near-normal temperatures are anticipated. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Dry high pressure will build from the west early next week behind a low pressure system shifting off the Mid-Atlantic and Northeast coasts. However, a few showers and/or thunderstorms will be possible near coastal locations Monday, followed by slightly greater precip coverage on Tuesday as mid/upper lvl energy shifts along the western edge of a mid/upper lvl ridge axis over Florida. High pressure should prevail into mid week ahead of a large mid/upper lvl trough of low pressure expanding over the Central United States. A cold front associated with this feature should then sweep across much of the Eastern Conus during the middle of next week. Given the setup, a southerly flow ahead of the front should support increasing chances of showers and/or thunderstorms through Wednesday. High temps will be dependent on cloudy skies and precip coverage, but should peak in the upper 80s to around 90 degrees, warmest in Southeast Georgia. Overnight lows should range in the upper 60s/lower 70s Sunday night, then lower to middle 70s into the middle of next week. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... Thunderstorms east of KSAV at the onset of the KSAV 0z TAF should push east over the coastal waters. It is possible that lightning and thunder will be observed through 2z. Light rain should pass over KCHS through 2z, little to no impact on conditions. I expect that considerable debris clouds will remain over the terminals through most of tonight. Deep convection will be possible across the terminals again tomorrow by 20-21Z. Extended Aviation Outlook: Probabilities for periods of restrictions at either terminal due to direct impacts from showers/thunderstorms will generally increase each day into the weekend. Prevailing VFR conditions are expected early next week. && .MARINE... Tonight: Southerly winds to increase as a warm front passes north through the waters and a stronger low-level jet sets up. Speeds will increase to 15-20 kt for the Georgia waters with 15 kt across the South Carolina waters. Seas will increase as a result, reaching 2-4 ft nearshore waters with a solid 4 ft over the offshore waters. There could be a few gusts to 25 kt after midnight, mainly near the Gulf Stream, but do not anticipate the durations to be frequent enough to justify a Small Craft Advisory. Friday through Monday: The coastal waters will generally remain under the influence of Atlantic high pressure, with conditions expected to remain below Small Craft Advisory levels this weekend and early next week. In general, south winds will periodically veer southwest while peaking 15-20 knots early this weekend, before turning offshore and gradually diminishing to around 10 kts or less early next week. Seas will range 2-4 feet. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...NED/RJB SHORT TERM...JMC LONG TERM... AVIATION...JMC/NED MARINE...JMC/RJB
Area Forecast Discussion
National Weather Service Dodge City KS
530 PM CDT Thu Aug 31 2017 ...Updated aviation section... .SHORT TERM...(This evening through Friday) Issued at 227 PM CDT Thu Aug 31 2017 Some scattered thunderstorms will be possible early tonight near a surface boundary that will be located over eastern Colorado however these storms are expected to weaken as they move east/southeast. A few of the models do suggest that some light showers will spread into portions of far west central Kansas between midnight and 6 am. At this time am not overly excited about precipitation chances based on the NAM and RAP forecast soundings near the Colorado border between 06z and 12z Friday but still will favor a slight chance for something early this morning west/northwest of a Garden City should a few of these storms hold together. There will also be some mid to high level clouds spreading east from these storms during the overnight hours and given this increase in cloud cover do not anticipate that lows tonight will be as cool as the last few night. The previous forecast with lows around 60 still look on track for most of western Kansas. An upper level trough, located over the Pacific Northwest at 12z Thursday, will cross the Central Rockies during the day on Friday as the eastern Colorado surface boundary approaches the Colorado/Kansas border. Ahead of this surface boundary the southerly winds will increase into the 15 to 20 mph range as some mid and high level moisture spreads into western Kansas. The mixing depth Friday afternoon based on model soundings is forecast to be around the 850mb level and based on this the highs on Friday are expected to range from 85 to near 90. .LONG TERM...(Friday night through Thursday) Issued at 227 PM CDT Thu Aug 31 2017 An upper level trough will cross the western Kansas early Friday night. Based on the latest models earlier this afternoon it appears that the better moisture and lift ahead of this wave will be located across northern Kansas as this upper wave passes. Also the better instability early Friday evening will be focused near a surface boundary located from southeast Colorado into northwest Kansas. The storms that do develop along this boundary late Friday may briefly strengthen but as they move east/southeast they are expected to weaken as they cross western Kansas during the overnight hours. Early in this event as some of these storms strengthen a few of the stronger storms may be capable of producing hail up to quarters and some gusty winds. Once this upper trough passes a period of dry weather will return as temperatures warm into the 90s over the Labor Day weekend. The main question this weekend into early next week is how warm temperatures will climb ahead of a cold front that will be approaching southwest Kansas through Monday. All models agree with that the warmer air will be located just ahead of this surface cold front based on the 850mb thermal ridge axis, however where this front will be Sunday and Monday afternoon is unclear. The ECMWF is the most aggressive with this frontal boundary pushing the front into southern Kansas by late day on Monday. The GFS at 00z Tuesday has this surface boundary in northern Kansas. Given these differing solutions the temperatures on Monday will be a little tricky. On Sunday it still appears that guidance is too cool with the highs based on the 850mb temperature trends. Some highs in the upper 90s is not completely out of the question in west central or north central Kansas Sunday afternoon. Highs in the mid 90s likely further south. On Monday the highs again are will climb into the mid to upper 90s despite the uncertainty on the frontal boundary late day. This is based on the forecast 2M temps from the ECMWF and what the EKDMOS suggests for Highs on Monday. The only question is where the warmest temperatures will be located. There will also be a chance for overnight convection along and behind this surface boundary as a northern branch upper level trough approaches the Central Plains. Models today remain in good agreement with the better opportunity for convection across central Kansas being on Tuesday as the northern upper wave passes. As the precipitation ends and the cold front drops south into the Oklahoma on Tuesday some colder air will return to western Kansas. It currently appears that some fall like temperatures will briefly return mid week as a cool dome of high pressure builds across the Central Plains. For Tuesday will need to monitor the cloud cover and if we do not see any sun during the afternoon then highs Tuesday afternoon may struggle to get much warmer than the lower 70s. Wednesday will be warmer but still unseasonably cool. && .AVIATION...(For the 00Z TAFS through 00Z Friday evening) Issued at 529 PM CDT Thu Aug 31 2017 VFR conditions will prevail overnight with mostly clear skies. Winds will be light and from the southeast. && .PRELIMINARY POINT TEMPS/POPS... DDC 58 86 61 91 / 0 10 40 10 GCK 58 87 60 91 / 10 10 30 0 EHA 59 88 62 89 / 0 10 30 0 LBL 61 89 62 90 / 0 10 30 0 HYS 60 85 61 90 / 0 10 40 0 P28 60 87 64 89 / 0 0 50 10 && .DDC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Burgert LONG TERM...Burgert AVIATION...Hovorka_42
Area Forecast Discussion
National Weather Service Des Moines IA
707 PM CDT Thu Aug 31 2017 .SHORT TERM.../Tonight through Friday/ Issued at 200 PM CDT Thu Aug 31 2017 Stubborn stratus has been the main forecast challenge on the short term side today. The band of lower ceilings resides in the vicinity of a shallow backdoor front that is slowly sagging southwest. High-res models suggest the potential for a few showers and storms late this afternoon and early evening near the frontal axis in central Iowa. Latest RAP analysis indicates 1000-1500 J/kg of MLCAPE and weak theta-e convergence in the 925-850mb layer, but the spatial coverage of any convective activity will be sparse at best as favorable upper level kinematic support remains well west of the forecast area. Areas of fog are possible again early Friday morning, mainly from north central through southeast Iowa. NAM/GLAMP favor fog, while the HRRR-TL/SREF/RAP camps remain clear. Upwind obs show a slightly cooler and drier air mass filtering behind the front, which may be enough to limit the fog potential tonight. Any mention of fog has been left out of the grids for now due to low confidence. .LONG TERM.../Friday night through Thursday/ Issued at 200 PM CDT Thu Aug 31 2017 Primary focus of the long term period is temperatures with a warm up expected through the weekend followed by a strong cold frontal passage early next week. Weak ridging aloft will lead to quiet conditions through the weekend. Low level southerly flow ramps up by Sunday as an upper level trough digs southeast into the northern Rockies. Strong warm air advection pushes 850mb temps above 20C for Sunday and Monday with afternoon highs in the mid to upper 80s. Would not be surprised to see some places in southern Iowa break into the 90s. Euro and GFS have come into much better temporal agreement with the upper level low as it digs south and becomes highly amplified. This will shove a strong cold front through the area Monday night. Isolated to scattered storms are possible with the frontal passage, but the extent and strength of the activity will be limited by dry air and weak instability. Expecting highs to drop back into the 60s and 70s for the middle of the week. Overnight lows were adjusted a few degrees lower from the inherited Superblend to better match the lows favored by ECE/MEX guidance. This would be an early taste of fall as the Des Moines metro has not seen temperatures in the 40s since May. && .AVIATION.../For the 00Z TAFS through 00Z Friday evening/ Issued at 707 PM CDT Thu Aug 31 2017 Stratus continues to linger across north central Iowa this evening but should slowly diminish with drier air pushing in from the northeast. Otherwise, some light fog will remain a possibility overnight through sunrise. Widespread VFR conditions are expected into Friday with good weather for general aviation. && .DMX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...Martin LONG TERM...Martin AVIATION...Cogil
Area Forecast Discussion
National Weather Service Indianapolis IN
1121 PM EDT Thu Aug 31 2017 .UPDATE... The Aviation section has been updated below. && .SYNOPSIS... Issued at 224 PM EDT Thu Aug 31 2017 Low pressure and associated remnants from Harvey across northwest Mississippi will push northeast toward the Ohio Valley tonight. This will result in dry weather tonight for central Indiana...however showers are expected to arrive mainly across the southern parts of the Indiana on Friday and Friday Night. Harvey leftovers are expected to slowly exit the area on Saturday...and rain will end from southwest to east central parts of Indiana. Much of the north half of the state should remain dry. Dry weather is then expected to return for the end of the holiday weekend as High pressure builds across the middle Mississippi and Ohio river valleys. The passage of a cold front on Tuesday will usher in a blast of cooler fall-like air for the second half of next week. && .NEAR TERM /Tonight/... Issued at 1000 PM EDT Thu Aug 31 2017 Lowered min temps a bit based on latest near term guidance and wetbulb temp progs across the south where precip may arrive before daybreak. Additionally, increased wind speeds and gusts tonight into tomorrow per upstream obs and HRRR and BUFKIT guidance. Previous discussion follows. Issued at 224 PM EDT Thu Aug 31 2017 Surface analysis early this afternoon shows low pressure over Mississippi and High pressure was in place across the northern Great Lakes. GOES16 shows bands of clouds associated with Harvey remnants streaming across Central Indiana. A NE surface flow was in place with dew points in the upper 50s. National Radar Mosaics show precipitation contained relatively close to the center of circulation...over Arkansas and Mississippi. GFS and NAM suggest that the low will push in to the Tennessee River Valley late tonight...spreading rains across Tennessee...Kentucky and far southern Indiana. Forecast soundings and Time heights remain dry for tonight as best moisture has yet to arrive...and dry NE surface flow remains in place. We will expect increasing clouds tonight as the cloud shield with the low continues to thicken upon approach. As for temps...with with a tropical air mass arriving along with cloud cover...will trend lows at or above than the forecast builder blend. && .SHORT TERM /Friday through Sunday/... Issued at 224 PM EDT Thu Aug 31 2017 GFS and NAm both push the surface low farther northeast on Friday and Friday Night...spreading cyclonic circulation across Indiana and spreading moisture into the southeast half of the state. Time Heights and forecast soundings show deep moisture and strong lift arriving mainly south of Winchester-Vincennes line by Friday afternoon and Friday night. Strong pressure gradient across the area will also result in gusty winds on Friday afternoon and Friday Night. Given the favorable forcing will trend pops highs across the far SE...trending lower farther northeast. At this time locations like Lafayette and Kokomo may stay dry due to the expected path of moisture. Given the expected clouds and rain...will trend highs on Friday at or below the forecast builder blend. Will trend Friday Night lows at or above the blend. Models suggest that by Saturday the Center of circulation will have move to west Central Ohio. Time heights and forecast soundings show moisture across the eastern Half of the state during the morning hours...however dry air and subsidence begins to build across the western half of the state...denoting clearing. As Harvey leftovers get farther north...acceleration should increase also...ending precipitation quickly on Saturday afternoon from West to East. By 00Z Sunday...ridging and subsidence is quickly building across Indiana denoting dry weather. Thus will end pops on Saturday morning and trend them lower as the day progresses. Dry weather looks to remain in place on Sunday as GFS and NAm suggests surface high pressure in place as forecast soundings show a dry column with subsidence and a mid level inversion. Thus Partly cloudy/mostly clear and temps below seasonal normals given the expected NW flow in the wake of the departed low. && .LONG TERM /Sunday night through Thursday/... Issued at 233 PM EDT Thu Aug 31 2017 Dry weather will be in place to start the long term with broad high pressure sliding off to the southeast and warm southerly component flow into the area. By Monday afternoon and evening a cold front will approach from the northwest and bring chances for showers and isolated thunderstorms with it. The best chances with this front appear to be overnight Monday as the front moves through. Chances will continue through Tuesday as the upper trough axis moves through the area, but after that conditions should be dry and cool with another Canadian high pressure system building in over the area. Given some model differences in timing of the frontal system and upper trough passage, confidence is moderate. && .AVIATION /Discussion for the 01/06Z TAFs/... Issued at 1122 PM EDT Thu Aug 31 2017 VFR through the period, with the exception of some MVFR ceilings late in the period at BMG. Harvey remnants will move into the region during the period, and the predominant impacts will be some shower activity at IND and especially BMG, and gusty northeast winds across the area. Cannot rule out a rumble of thunder but this is far too low probability for inclusion. Winds be in the mid teens with gusts into the low to mid 20KT range generally out of the northeast much of the period. && .IND WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SYNOPSIS...Puma NEAR TERM...Puma/Nield SHORT TERM...Puma LONG TERM...CP AVIATION...Nield
Area Forecast Discussion
National Weather Service Elko NV
318 PM PDT Thu Aug 31 2017 .SYNOPSIS...Isolated to scattered thunderstorms will end later this evening. A strong ridge of high pressure will build in from the west beginning tonight and will bring much above normal temperatures to the area for Labor Day weekend and into next week. Sky conditions should be mainly clear Friday through Saturday. && .SHORT TERM...Tonight through Saturday Isolated to scattered pulse type thunderstorms are ongoing this afternoon in all but Humboldt county, where drier air has already moved in, but should quickly dissipate later this evening as a dry airmass continues to move into Nevada from the northwest. This will bring mainly clear skies the next couple of days for the start of the Labor Day weekend, with temperatures warming back well into the 90`s most valleys by Saturday. Winds will be on the lighter side under the building ridge of high pressure. The HRRR model continues the transport of smoke into our area and so continued areas of smoke through the night. .LONG TERM...Saturday night through next Thursday. Models agree on general pattern with strong upper ridge over the Great Basin through the period and Tropical Storm Lydia now over Cabo San Lucas heading up along Baja and then turning left into the Pacific. But..... The GFS and Euro differ completely on where the strung out moisture will go as it weakens. The Euro has it moving out to sea with the dying system. The GFS has a large slug of it moving up along the Sierra Nevada line and some slopping over into central Nevada. Have leaned toward a mix of the two, but probably a little heavy on the GFS. Pops increase into the extended over the entire forecast area but are still not impressive for the 20s at best. Temps will still be warm under the governing ridge, and so dry storms will cover central, eastern, and northern Nevada but in an isolated pattern. It is, after all, still summer. && .AVIATION...Thunderstorms becoming more common Thursday afternoon but still isolated. Some of the storms are on the strong side with small hail and gusty winds occurring. Best chance for VCTS around KEKO and KELY. Other storms en route from northeast of KTPH to KELY. Most storms are east of a line from around Owyhee to Austin to Round Mountain and moving slowly east. Ceilings and visibility will be VFR. Erratic cross winds could occur near runways. Smoke from fires in western Nevada covering large areas of the state. Not reducing surface visibility but may reduce slant visibility and possible obscure an occasional mountain peak. It`s hotter than normal, so density altitudes will be higher than normal. && .FIRE WEATHER...Isolated thunderstorms are ongoing this afternoon in Fire Weather Zones 469 and 470 which are on the drier side while thunderstorms in central Nevada fire zones are more scattered and on the wetter side with some heavier showers being reported as well as some small hail. Erratic wind gusts can still occur with any storm. All storms will taper off later this evening. Drier air moves into the region tonight through Saturday, lowering RH and bringing temperatures much above normal once again. Winds are expected to remain under critical conditions as high pressure builds in. && .LKN WATCHES/WARNINGS/ADVISORIES... None. && $$ 90/98/98/90
Area Forecast Discussion
National Weather Service Blacksburg VA
1146 PM EDT Thu Aug 31 2017 .SYNOPSIS... The remnants of Harvey will move into the Tennessee Valley Friday and into the Ohio valley Saturday as high pressure over the Great Lakes surges down east of the Appalachians. This will allow rain to develop across the region late tonight and continue through tomorrow. Showers will continue Saturday as Harvey moves northwest of the area, then end Saturday evening. High pressure will build into the region for Sunday and continue into the first part of next week. && .NEAR TERM /THROUGH FRIDAY/... As of 1140 PM EDT Thursday... Adjust temperatures, dewpoints and pops some to reflect latest trends and observations. Temperatures are cooling more in the west than the east. A blend of the HRRR, GLAMP25, and existing forecast yielded very reasonable values. Dewpoints needed less adjustment, but were too low in the southeast part of the CWA where dewpoints have come up to near 70F. Otherwise, adjusted pops down for the next few hours as radar trends showing precipitation well back to the southwest yet at this hour. Followed HRRR for overnight trends with pops ramping up toward categorical after 08Z. As of 745 PM EDT Thursday... No need for any significant changes at this time. One heavy shower moved through the Danville area this evening, otherwise only sprinkles or light showers dotting a few areas. Following latest HRRR, would not expect much precipitation until after midnight, spreading north from the southwest with time after that. As of 300 PM EDT Thursday... Late afternoon radar shows showers mainly along and south of route 460 ahead of a cold front sagging southward across the region. The showers will push off to the south this evening before the remnant circulation of Harvey moves up the Mississippi valley and combines with high pressure over the Great Lakes forming a strong wedge east of the Appalachians to buckle the front and create strong isentropic lift over the region. This will allow rain to surge back into the area from the south late tonight, then continue through Friday. Differences in timing and placement of features among guidance members are making things difficult, but still expect the heaviest rain to fall across the VA/NC piedmont and Southside VA, with some local enhancement due to orographic effects along the Blue Ridge, where amounts of 1.5 to near 2.0 inches are expected with lesser amounts further north and west of the Blue Ridge. Ensemble hydro models indicate the current low flow along area waterways will be able to absorb runoff without causing widespread hydro issues. However, the situation will continue to be monitored closely to see if locally higher amounts and/or training cells develop and cause local problems. Shear profiles along and south of the wedge boundary tomorrow continue to be robust with large looping hodographs. The limiting factor for severe weather will be how much instability can develop, and given the amount of shear expected it will not take large values of CAPE to support severe storms. The key will be how much instability can pool ahead of the boundary before it pushes far enough south and the cool stable wedge shuts down the threat. Believe the best chance for cells capable of tapping into the shear to develop will be far southwest from the Mountain Empire of VA to the mountains/foothills of NC where the wedge normally has difficulty penetrating, and extending further south into the NC piedmont. The situation will be monitored quite closely tomorrow. Temperatures tonight will be in the low to mid 60s east of the Blue Ridge, with readings around 60 to the west. Friday will be quite cool as the wedge builds down tomorrow with temperatures in the north likely falling throughout the day, and any heating in the south eventually shut off by the surging wedge. && .SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY NIGHT/... As of 325 PM EDT Thursday... Low pressure/Harvey will be in south-central KY Friday evening while a front situates itself east of this low into far SW VA, then southeast into central NC with high pressure wedging southward from the Northeast. The upper pattern favors a slow moving system, so inclined to keep categorical to likely pops in Friday night, then should see a dry slot work in from the NC foothills/piedmont Saturday, though with upper low still west and southwest flow aloft, plus moisture should still see a scattered coverage Saturday with higher chance in the mountains. Heading through Saturday night, the Harvey remnant moves into the mid-Atlantic, while the upper low opens to a trough and weakens. Low level flow turns west to northwest and could see residual showers in the mountains Sunday. Temps stay well below normal for highs Saturday, the slide back closer to normal Sunday as sunshine starts to return. Heaviest rainfall looks to occur Friday evening with best upslope and overrunning the wedge, where all 3 models showing two distinct areas of heavy rain, one across KY into northern WV and the other over the NC piedmont into southern VA. A shadow of sorts, where rain will be less is showing up in most models from the mountain empire of SW VA into the Alleghanys. Will have to watch for training of deeper convection over the piedmont especially into Friday evening for localized flood threat. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 325 PM EDT Thursday... Models are in agreement into developing a digging trough from the Great Lakes into the TN Valley through midweek, but some differences beyond Wednesday as too how far east the trough axis moves, in relation to strength/position of upper ridge over the western Atlantic. Needless to say should be fair and seasonably warm Monday. Frontal boundary will be pushing into the mountains by Tuesday evening with increasing chance of showers/some thunderstorms along/ahead of it. Ahead of it should be warm/humid Tuesday. Frontal boundary slows down per ridge offshore with waves of low pressure setting up along it. This should keep a good threat of showers around for our area Wed-Thu. Temps should fall back to or below normal, with highs more than likely cooler than normal ranging from mid 60s to lower 70s west, to mid to upper 70s east. && .AVIATION /04Z FRIDAY THROUGH TUESDAY/... As of 750 PM EDT Thursday... Poor aviation conditions expected through most of the TAF valid period. We will start with a period of mostly VFR ceilings, but that will quickly deteriorate after 06Z. Three synoptic situations that will drive the weather through the period. First, low pressure developing along the SC/NC coast and helping to pull a feeder band essentially associated with the remnants of Harvey, now across northern LA, from the AL/GA area toward the coast. Some of this moisture will work into the Piedmont late tonight/Friday morning before shifting eastward toward the coast. The next factor of importance is the development of a wedge as high pressure moves toward New England. The rain and coastal low pressure will help reinforce the wedge as well. Finally, the remnants of Harvey will be moving northeast through central and northeast KY Fri and Sat. The heaviest rainfall associated with this will remain to our northwest, but this will keep the weather unsettled with potential for a few feeder bands to affect the area, especially Saturday. Ceilings are expected to fall into the MVFR and even the IFR range as rain moves into the region late tonight/early Friday. Little to no improvement is expected during the day Friday. Visibilities will remain VFR through the evening, then fall mostly in the MVFR range late tonight and remain there through the day Friday. Some IFR visibilities can be expected in the higher terrain where the ceilings fall below 010. Winds will be mostly light and variable or southwest 3-5kts this evening, becoming northeast to east late tonight into Friday morning as the wedge develops and intensifies across the region. With the coastal low/front developing and high pressure strengthening across the northeast U.S., expect winds to become stronger and gusty. Sustained speeds of 10-12kts with gusts of 20-22kts are definitely not out of the question, especially at LYH, DAN, and BLF. Will definitely need to watch the winds at BLF as with this type of pattern, they could become quite strong and gusty in that region. The HRRR depicts quite strong/gusty winds by Fri afternoon across much of the region. Finally, isolated thunderstorms will be possible Friday afternoon across the Piedmont, mainly of NC. Will only include in the DAN TAF at this time. Medium to high confidence in ceilings through the TAF valid period. Medium to high confidence in visibilities through the TAF valid period. High confidence in wind speed and direction through the TAF valid period. Low confidence in thunderstorm potential Friday afternoon. Extended Aviation Discussion... The remnants of Hurricane Harvey will track northeast through KY and into eastern OH/western PA Saturday, then become absorbed in the general synoptic pattern moving toward the northern Mid- Atlantic Sun-Mon. Harvey will no longer be a factor in our weather after Saturday, and its main effects will remain northwest of our region. Widespread precipitation will decrease Saturday as the remnants of Harvey moves to our northwest and the coastal front shifts well southeast of the area. Some VFR ceilings may be possible Saturday, but expecting mostly MVFR conditions. Sunday into early next week will see improving conditions to mostly VFR as high pressure moves southeast into the region as Harvey exits to the northeast. The exception will be late night/early morning patchy dense fog at the usual locations, e.g., LWB and BCB. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...MBS NEAR TERM...MBS/RAB SHORT TERM...WP LONG TERM...WP AVIATION...AMS/MBS/RAB