Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/21/17

Area Forecast Discussion
National Weather Service Buffalo NY
1015 PM EDT Wed Sep 20 2017 .SYNOPSIS... Warm temperatures and dry conditions will persist through the remainder of the week and the coming weekend, as high pressure will remain in place across the region. && .NEAR TERM /THROUGH THURSDAY/... Skies have cleared out this evening outside of some high thin clouds clipping Central New York and the Eastern Lake Ontario region. The clear skies and light winds will set the stage for another foggy night for many areas later tonight and into early Thursday morning, particularly in river valleys and near lakes/ponds. Similar to last night, fog and low stratus is likely to develop along the south shores of Lake Ontario. This cloud cover will linger into Thursday morning before dissipating by Thursday afternoon. With ideal conditions for radiational cooling and slightly lower dewpoints, we should see cooler temperatures as compared to Tuesday night, with lows in the 50s, with a few lower 60s near Lake Erie. Thursday will be another near carbon-copy of today with perhaps the only differences being the mid-level ridge strengthening to 588dm and 850mb temps warming a degree to +17C. The high pressure surface and aloft will keep dry and warm weather in place with high temps again warming into the low to mid 80s or 10-15 degrees above normal September levels. Dewpoints holding in the 60s will keep a humid feel to the airmass. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/... The calendar will remain turned back a couple months through this an anomalously strong 590dm sub tropical ridge will remain anchored over the Ohio Valley and Lower Great Lakes. This prodigious ridge will be accompanied by equally exceptional warmth. H85 temps tat will start off in the mid teens C Thursday night will further warm to the upper teens C for the weekend. This will encourage additional day to day warming so that by Saturday...max temps will be in the mid to upper 80s F. Given the increasingly dry antecedent conditions...its not out of the question that select locations in the Genesee Valley (ie. Dansville) and in the typically warmer valleys of the Southern Tier would reach 90. If this were mid summer (when the sun angle would be more than 20 deg greater) then we would possible be talking about some oppressive heat. Luckily for us...the Gulf of Mexico will be cut dew points that will start off in the upper 50s to lower 60s will not climb past 65 by late in the weekend. Meanwhile the nights will feature mainly clear skies with the resulting favorable radiational cooling producing fog in open... outlying areas...and particularly in the Southern Tier valleys. Mins will range from the mid and upper 50s across the Southern Tier and parts of the North Country to the low to mid 60s across the lake plains. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... A very high confidence forecast remains in place for the unseasonable warmth to continue during this three day a high amplitude ridge will remain intact across the eastern third of the country. The only problem will be the possible effects from Hurricane Maria...which by Wednesday will likely be churning northward of the mid Atlantic coast. While the ridge will keep us rain free through at least Tuesday...there have been some medium range ensembles that are suggesting that some Atlantic moisture could work back across the region late Tuesday night and Wednesday. From this vantage point though...the odds favor continued dry weather...but will introduce slgt chc pops as we end the seven day period. && .AVIATION /02Z THURSDAY THROUGH MONDAY/... VFR conditions are in place late this evening, however these will deteriorate as light winds and clear skies promotes the development of radiation fog. Tonight should be somewhat similar to last night, except that the northeasterly flow will be stronger across the eastern half of Lake Ontario rather than the western half. Stratus and fog is again likely to form along the south shores of Lake Ontario. Following HRRR guidance which had a good handle last night, this should be most widespread from Rochester to Syracuse which is downwind of a NNE surface flow. Fog will also form in the river valleys, impacting Jamestown. Elsewhere fog will be patchy, but it is difficult to rule out at any given location. Visibility will vary in radiation fog, but there is a potential for VLIFR conditions in dense fog at times. This has the greatest chance to impact ROC/JHW, but cannot completely be ruled out at any terminal location. Stratus will linger south of Lake Ontario during the morning hours Thursday, with lingering IFR conditions in low cigs. This will dissipate by Thursday afternoon with VFR conditions. Outlook... Thursday night through Monday...VFR. Local IFR conditions each late night and early morning with fog. && .MARINE... High pressure will remain in place across the Lower Great Lakes right through next weekend. This will provide a long stretch of very light winds and flat wave action for the rest of the week and weekend with ideal boating conditions, but not much wind for sailing. && .BUF WATCHES/WARNINGS/ADVISORIES... NY...None. MARINE...None. && $$ SYNOPSIS...CHURCH/SMITH NEAR TERM...APFFEL/SMITH/WOOD SHORT TERM...RSH LONG TERM...RSH AVIATION...APFFEL MARINE...HITCHCOCK/THOMAS
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
1155 PM EDT Wed Sep 20 2017 .AVIATION... Cirrus canopy from Wisconsin convection is expanding steadily east into area. This should limit fog potential tonight and the current forecast of MVFR to occasional IFR vsbys late seems reasonable. A few showers may survive the trip into southern lower Michigan and brush KMBS with some small chance of formation later in the day on boundary left along northern fringe of upper ridge. There is still a hint or two that at least a scattered deck in the 3-5kft range will try to formation late tonight (coinciding with best time for BR) on nose of higher theta-e air working into area. For DTW...Period of patchy fog on the edge of MVFR/IFR possible by late tonight/early Thursday morning with perhaps a period of sct or bkn 3500-4500 foot clouds as deeper moisture also works back east into area. //DTW THRESHOLD PROBABILITIES... * Low for ceilings aob 5kft late tonight, ~09z-13z. && .PREV DISCUSSION... Issued at 409 PM EDT Wed Sep 20 2017 DISCUSSION... Most important item to communicate is long stretch of summerlike warmth and humidity that will begin tomorrow and run through Monday. High confidence exists in daytime temperatures running in the middle to upper 80s with dewpoints in the 60s to near 70. With negative PNA in place, the central Great Lakes will remain nestled right along the interface between equally large wavelength eastern Conus ridging and deep PAC NW and Western Canada PV reservoir. The peculiar aspect of this particular setup, and what provides a reasonable amount of uncertainty during the next 24 to 36 hours, is that while the upper level ridge will begin to reamplify aggressively in response to at least partially all of the tropic activity offshore, the ridge itself is one that does not have an overwhelming amount of support for downward vertical motion below 500 mb. Rather, much of the model data suggests that pesky low shower and thunderstorm chances Thursday and Thursday night will hinge upon the ability of pre-existing convective shortwave energy to survive downstream off of Rossby wave breaking. This afternoon and tonight. NWP matches up well with most recent Water Vapor imagery in showing corridor of deep drying associated with strong anticyclonic vorticity that is now pushing into southeastern Michigan this afternoon. Associated subsidence bubble in the 3.0 to 9.0 kft agl layer has been very efficient in eroding low cloud today. All that remains is a bkn boundary layer cumulus that resides in much of the eastern cwa. Some congestus exists in the lake convergence axis along the Lake Huron shoreline. So while a sprinkle or brief shower will be possible in the eastern Thumb this afternoon, there is very little signal to support anything more than that. Regarding fog potential tonight. Plan view perspective of forecasted theta e fields strongly supports that higher lower tropospheric moisture content that had been in place last night as been squeezed out of the cwa to the east. Surface pressure condensation pressure deficits out of the HRRR suggests that best potential for fog will exist within this air mass over southwestern Ontario. There is some signal that suggests fog could bleed back westward around daybreak and impact portions of the eastern thumb down into Macomb County. Otherwise, additional drying from the subsidence mentioned above should limit formation. Time of year and warmer dewpoints still supports carrying a patchy fog mention for shallow radiational fog potential. Thursday. Interesting forecast with alot of moving parts. First thing will be watching for is the relatively strong elevated mixed layer plume that will fold over from Wisconsin/Northern Plains today into southeastern Lower Michigan Thursday. This folding over of the higher theta e ridge will be caused by incredibly strong 1000-500mb geopotential height rises occuring over the upper Mississippi River Valley and Western Lake Superior tonight. The increasing lower column high pressure, complete with a mesohigh, and rapid change to anticyclonic curvature will shove the warm and humid air into the region. Model data continues to support some convective shortwave energy and pre-existing shower and thunderstorm activity surviving within the EML across northern Lower Michigan and pushing into the Saginaw Bay after daybreak. With the strong ridging, only be looking at remnant elevated thunderstorm activity above 8-10 kft agl layer. Overall, just looking at some shallow isentropic lift wash with no upper level jet support, no low level jet. Confidence in showers and thunderstorm during the morning across the north is low. The second item to watch for will be exactly where the exact edge of an internal surface ridge structure develops. Model guidance suggests the main axis will develop to the east of the cwa with at least a part of the western edge back into the area. This local maximum to the ridge appears to set up directly under the corridor of the strong anticyclonic vorticity that was discussed earlier. The importance of this ridge is twofold as it will directly impact to what degree temperatures will reach Thursday, but also set a hard edge to the capping of any thunderstorm chances. Definitely will be very warm and humid with temperatures pushing middle to upper 80s. One certainly needs to stress the warmth as heat indices in many areas will likely push to and exceed 90. Really dont think we will see runaway highs in here in southeastern Michigan with such rich moisture, some residual southeasterly flow trajectories, and lack of mechanical mixing or southwesterlies. Thunderstorm chance for Thursday is the tricky forecast. Models including the ECMWF and regional GEM remain steadfast in keeping a persistent scattered shower and potential thunderstorm chances in play across the north particularly in and near Saginaw Bay. This positioning is curious because this would be along the west edge of the surface meso-ridge. The uncertainty is a result in the complete lack of any synoptic scale lift. The eye-raising aspect of the thermodynamic environment Thursday is the steep 800-600mb lapse rates that will result in SBCAPES in the 2000-2250 J/KG range. There will be a complete lack of shear with 0-6km bulk shear at less than 10 knots. As a result, not expecting any severe weather potential. Expectations for any thunderstorm activity would be pulse type activity with at least an entry chance for hail. Heavy rainfall will also be possible with very little cell movement. Friday...Large scale pattern will become very conducive for retrograding upper level high pressure closing off over the western and central Great Lakes. High confidence exists in dry weather Friday. Temperatures Friday will again be very warm in the middle to upper 80s, readings some 15 degrees above averages. An expansive surface high pressure system sitting over the eastern third of the U.S. along with an amplified upper-level ridge will continue to bring hot, dry conditions to Michigan throughout the weekend and into early next week. Long range models continue to support 850 mb temperatures that average 17 - 18 degrees Celsius. Warm air aloft along with southerly flow and generally clear skies will support daytime highs that peak in the mid to upper-80s. For reference, record highs range from the upper 80s to low 90s across Southeast Michigan for this time frame. The next chance for precipitation and closer to seasonal temperatures will return on Wednesday, as a cold front acts to produce the slight chance for rain and thunderstorms. Cooler air behind the front will act to keep daytime highs capped in the mid to upper 70s. While too early to say with high certainty, seasonal temperatures will look to stick around into next weekend. MARINE... High pressure will dominate the area through the next several days with south to southeast winds generally under 15 kts. Lake St Clair and Lake Erie winds will be more generally out of the southeast and lighter than the winds in the open waters of Lake Huron. Winds are expected to remain generally under 15 kts through the weekend as high pressure drifts in over Lower Michigan. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....DG DISCUSSION...CB/AM MARINE.......CB You can obtain your latest National Weather Service forecasts online at
Area Forecast Discussion...UPDATED
National Weather Service Jackson MS
841 PM CDT Wed Sep 20 2017 .UPDATE... Updated for evening discussion. && .DISCUSSION... Most of the convection has died down now and skies continue to clear. Those areas that saw rainfall today are already seeing temperatures in the low 70s. Those other locations are still in the upper 70s. Overall, temps will fall to the upper 60s and low 70s tonight. Some patchy fog will again be possible tomorrow morning. Cleared out most of the pops in the forecast with this update. /10/ Prior discussion below: Tonight through Thursday... Latest RAP satellite imagery showed a weak shortwave moving into the region. This combined with some cooling aloft and low level moisture had triggered scattered showers and some thunderstorms across the region. With 6-7c lapse rates we may see a few strong storms with some gusty winds for the remainder of the afternoon. Expect the weak shortwave to exit the region by late tonight. For early this evening the last of the showers will end across the northwest and south. For later tonight expecting another round of patchy fog prior to dawn which will lift by 14z. Another weak shortwave from the west will push through on Thursday. Return flow ahead of this feature will trigger isolated to scattered showers and thunderstorms mainly during the afternoon. Once again midlevel lapse rates will be from 6- 7C with weak flow. This could bring a few strong storms with some gusty winds during the afternoon. As far as temperatures are concern readings will continue to be above normal. Lows will be in the upper 60s to lower 70s. Highs will be in the upper 80s to lower 90s. Heat indices will range from the middle 90s to around 100./17/ Thursday night through Wednesday... The period will start out with a highly amplified pattern over the CONUS as a deep longwave trough digs across the western portion of the US. This will in turn amplify downstream ridging over the mid- Mississippi River Valley and Midwest. This ridging will keep the warmest temperatures in place through the weekend with highs in the low 90s before an upper low retrogrades beneath the ridge and into the ArkLaMiss by the start of next work week. These lower heights will help keep temperatures a few degrees cooler with highs topping out in the upper 80s through the middle of the week. A cold front is progged to move through the area next Thur/Fri with a stout shortwave diving through the Northern Plains helping to reinforce a more fall like airmass across the area. In terms of precipitation, isolated to scattered diurnally driven afternoon showers and storms can be expected through the weekend with the greatest coverage along and south of I-20. While some isolated activity could linger into early next week, drier air wedging in from the east will help to cut back on coverage with any isolated showers and storms confined mainly to the Delta. /TW/ && .AVIATION... 00Z TAF discussion: Isold TSRA were noted just north of GTR and between I-20 and HWY 84 at 2330Z. This activity wl dissipate by 21/02Z and VFR conds wl prevail areawide until 10Z. After 10z MVFR vsbys wl be psbl areawide until 14Z. After 14Z VFR conds wl prevail until Isold to Sct TSRAs develop Thu aftn and cont into early evng. /22/ && .PRELIMINARY POINT TEMPS/POPS... Jackson 70 93 71 91 / 9 30 9 27 Meridian 70 93 69 90 / 11 30 16 30 Vicksburg 71 92 71 91 / 8 21 5 18 Hattiesburg 69 91 69 90 / 15 29 17 34 Natchez 70 91 70 90 / 15 25 11 29 Greenville 71 93 70 92 / 8 17 5 17 Greenwood 71 93 71 91 / 8 19 5 17 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...None. LA...None. AR...None. && $$
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
625 PM CDT Wed Sep 20 2017 .SHORT TERM... 1246 PM CDT Through Thursday afternoon... Concern is on convective development late this afternoon/early evening and how far east/south it will make it, along with hot and humid conditions that look to persist for the coming days. It is indeed hot and humid for mid September, and ORD/MDW are already almost at 90 degrees today. Warm south winds and little cloud cover will allow most locations to get close to 90 today. Convective temperatures on the RAP are in the 90s across IA, which looks to delay any initial convective development near the cold front until late this afternoon. There is pretty good agreement though that thunderstorms will develop between 5 and 6 pm near the Mississippi River. The question will be with the upper forcing being a bit weaker farther east, and with the convection arriving around sunset or so, that should limit the eastward thunder concerns with this initial development. There could be some sprinkles that get closer to Chicago but the forcing does not appear to overcome dry mid levels. While west/northwest IL is favored at this time, the low level jet will ramp back up in this high PWAT environment, which could lead to an uptick in showers and storms late this evening/early overnight hours. PWATs near the front remain elevated and do increase, so if showers and storms do get a bit closer, some modest rain rates could occur in the far northwest. Upper level heights rebuild tomorrow, and continued deep layer southerly flow will lift the effective frontal boundary back northward. The lower level airmass will be on par with today`s if not a bit warmer, and thus many areas will likely tag 90 or even the lower 90s. These are near record levels for mid to late September. With continued upper 60s to around 70 dewpoint, this places heat indices in the middle or even upper 90s. KMD && .LONG TERM... Thursday night through Wednesday... 155 pm...A warm frontal boundary will lift back north of the area Thursday night with hot and humid conditions continuing into this weekend. Bumped up high temps both Friday/Saturday to near guidance which is generally in the lower 90s Friday and around 90 Saturday. Given high temps today/currently are around 90...these forecast high temps for Friday and Saturday may end up being a few degrees too cool. Not expecting much change to dewpoints either... in the mid/upper 60s thus heat index readings could reach the mid/upper least for a few hours during peak heating in the early/mid afternoons. Thermally...conditions cool slightly Sunday/Monday but its possible that with little change to this pattern the models may trend warmer into early next week. No change to highs in the 80s Sunday/Monday...but these could also end up too cool. Dry conditions expected until a cold front arrives Tuesday night next week which will bring the next best chance of rain. Much cooler air will spread into the region behind this frontal boundary by Wednesday afternoon/evening. There may also be an isolated shower Sunday/Monday but chances are below mentionable from this distance. cms && .AVIATION... For the 00Z TAFs... Primary aviation concern this TAF cycle is with SHRA/TSRA chances. Storms have developed from eastern IA north into WI ahead of a weak cold front. All indications are that this activity will dissipate before reaching the immediate Chicago terminals, with best chance of impacts being at RFD. Have maintained a short tempo at RFD this evening to cover this threat. Otherwise, where skies clear overnight, could see some light fog/MVFR vsby, especially in the more rural areas like GYY/DPA. Otherwise, look for VFR conditions and light to moderate south winds through the TAF cycle. - Izzi && .MARINE... 155 pm...Strong low pressure over western Manitoba will slowly weaken tonight and Thursday as a weak trailing cold front moves south across Lake Michigan tonight into Thursday morning. This front is expected to stall over central portions of the lake then move back north as a warm front by Thursday night. A large trough of low pressure will remain nearly stationary across the plains through early next week which will maintain southerly flow across the lake. This trough/front will move across the Great Lakes region Tuesday night next week shifting winds to the northwest when a period of 15-25kts is expected. cms && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ VISIT US AT HTTP://WEATHER.GOV/CHICAGO (ALL LOWERCASE) FOLLOW US ON FACEBOOK...TWITTER...AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSCHICAGO WWW.TWITTER.COM/NWSCHICAGO WWW.YOUTUBE.COM/NWSCHICAGO
Area Forecast Discussion
National Weather Service Miami FL
809 PM EDT Wed Sep 20 2017 .AVIATION... Showers and thunderstorms will continue in the interior through the evening hours. they are not currently forecast to impact any of the TAF sites across South Florida. Tomorrow will see another round of convection. However, there is too much uncertainty as to the coverage and if they will impact any TAF sites to include in the forecast attm. && .PREV DISCUSSION... /issued 424 PM EDT Wed Sep 20 2017/ DISCUSSION... Latest IR satellite imagery shows a band of scattered low level cumulus stretching east to west across central Florida. In addition, a line of of building cumulus can also be noted around 10 miles inland from the Atlantic coast, where the sea breeze has managed to penetrate. Light overall flow will allow for sea breeze collisions to develop, similar to yesterday. The HRRR is hinting that the associated slow moving showers and isolated thunderstorms will continue over the interior through this evening. Besides a couple showers remaining over Palm Beach county tonight, where most of enhanced instability and moisture resides, expecting relatively dry conditions elsewhere. Maximum temperatures are topping out in the upper 80s along the east coast and low 90s inland, typical for this time of year. Thursday through Saturday: Synoptically little changes tomorrow with both ridging to the north and surface high pressure dominating. Light easterly winds and a modest amount of moisture will lead to a chance of showers and isolated afternoon thunderstorms, mainly over the interior where the sea breeze collision occurs. From Friday through this weekend, Hurricane Maria will edge toward the southern Bahamas then northward over the open mid Atlantic Ocean. There appears to be no direct impact to South Florida at this time. However, the aforementioned Hurricane will help to advect deeper tropical moisture into our region, as well as increase deep northeasterly flow. Thus, expect better coverage of showers and storms Friday into Sunday, especially along the eastern portion of the peninsula. Early next week: As Hurricane Marine continues to barrel northward over the Atlantic, drier air will be pulled down into our CWA. GFS PWATs drop to between 1.5" and 2.0". Subsidence aloft should suppress much of the convection, leading to a drier long term forecast. MARINE... Long period northeasterly swell from distant Hurricane Jose will continue to filter into the local Atlantic waters keeping cautionary conditions in the waters off Palm Beach County into Thursday. Light and variable winds today will allow both seabreezes to form this afternoon. Winds will gradually increase out of the east on Thursday and become turn more northeast or northerly by this weekend. BEACH FORECAST... Long period northeasterly swell from the distant Hurricane Jose will continue to filter through the local Atlantic waters. A high risk of rip currents will continue for all the Atlantic beaches through this evening, and likely remain moderate to high into late week. && .PRELIMINARY POINT TEMPS/POPS... West Palm Beach 76 90 77 90 / 30 30 30 50 Fort Lauderdale 79 91 79 89 / 20 30 30 50 Miami 78 92 78 90 / 20 30 30 50 Naples 76 92 75 91 / 20 30 20 40 && .MFL WATCHES/WARNINGS/ADVISORIES... FL...None. AM...None. GM...None. && DISCUSSION...27/JT MARINE...27/JT AVIATION...13 BEACH FORECAST...27/JT