Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/15/17

Area Forecast Discussion
National Weather Service Albany NY
957 PM EDT Mon Aug 14 2017 .SYNOPSIS... High pressure will be moving east of New England tonight, as a weak disturbance will approach from Pennsylvania and New Jersey with some isolated to scattered showers. An upper level disturbance and a cold front will bring a chance of showers and thunderstorms tomorrow into early tomorrow night. High pressure will build back in for the mid week with fair and dry weather with seasonable temperatures for mid August. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... 10pm update continues theme for earlier update...Latest runs of the HRRR, RAP, and NAM all bring an area of SHRA activity across the southern CWA during the overnight hours. Forcing is subtle with this feature, but with all three models on board, I maintain pops in the chance category for the southern 1/3 of the region during the overnight hours. The latest RAP shows Showalter indices dropping to 1C during the time of precipitation. Still did not add thunder. Otherwise, only other changes were to bring forecast in line with current observations. There is some weak elevated instability with Showalter stability indices values in the 0 to -2C range drifting across over the western Mohawk Valley and southern Adirondacks. We placed a slight chance of thunderstorms in there. With the increase of clouds and the low-level advection of moisture and theta-e increasing we are expecting low temps to be in the upper 50s to mid 60s with the warmer readings over the mid-Hudson Valley/Capital District/NW CT. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/... Tomorrow...Variable cloudiness and isolated to scattered showers will open the day with the weak disturbance moving through. Attention shifts to a short-wave trough approaching from the central and eastern Great Lakes Region. The GFS/NAM/ECMWF/CAN GGEM all indicated some scattered showers and potentially some thunderstorms impacting the forecast area with some timing differences. Some weak height falls occur ahead of the trough with sfc dewpoints increasing into the lower to mid 60s. SBCAPES on both the 12Z NAM and GFS are generally 500-1500 J/kg with 0-6 km bulk shear values of 35-50 kts. Some convection organization is possible if enough heating occurs ahead of the short-wave and it attendant cold front. The mid level lapse rates are not particularly steep across most of the region, except northeast of Albany where they may dip into the 6.5-7 deg C/km range over portions of southern VT and the Lake George Region. PWATS are 1-1.50". Some localized bursts of rain are possible. We did place some gusty winds in the grids for the eastern Adirondacks, Lake George Region and southern VT. These stronger storms will be conditional to the timing of the disturbance, and if enough instability is realized. The SPC Marginal Risk looks fine northeast of Albany in these areas. They are also a little bit closer to better upper jet dynamics, although northern New England looks even better outside of our area. The latest 3-km NAM shows limited isolated convection tomorrow. This will continue to be monitored. High temps should be similar to today with upper 70s to lower 80s in the lower elevations, and upper 60s to mid 70s over the higher terrain. Tue night...Any isolated to scattered showers ahead of the short-wave and sfc trough should quickly weaken in the early evening. A weak cold front moves across the region with weak cold advection. We placed some isolated to scattered showers with the cold front mainly west of the Hudson Valley into the early morning hours. Some patchy fog may occur from the Hudson River Valley eastward, especially where any showers or thunderstorms occur. Lows will generally range from the mid 50s to lower 60s. Wed to Wed night...Broad cyclonic flow at the sfc and aloft will impact the region with a cool and dry air mass for the mid week. A sfc anticyclone will build in from southeast Ontario. Sunshine will mix with a few cumulus clouds, but overall expecting partly to mostly sunny conditions due to strong subsidence with the sfc high building in. H850 temps will be in the +9 to 14C range from northwest to southeast across the region. Expect highs to be in the mid 60s to mid 70s over the mountains, and upper 70s to lower 80s in the valleys and over the hills. Humidity levels will be very comfortable with sfc dewpts in the 40s and 50s. Fair and tranquil conditions continue Wed night with the sfc high in control. Lows will be in the 50s except for some 40s over the srn Dacks, southern VT, northern Berks, and eastern Catskills. Some high clouds may move in from the south and west towards daybreak. && .LONG TERM /THURSDAY THROUGH MONDAY/... High pressure starts off the long term period on Thursday with seasonable temperatures for mid - August around 80 and comfortable dew points thanks to NW flow. While we should start off with some sun, we`ll likely see increasing clouds through the day as our high shifts into eastern New England leading to return flow. A warm front associated with a low in the Great Lakes starts advancing towards our area as well Thursday night into Friday with warm air advection increasing ahead of the frontal boundary. BUFKIT soundings suggest that sufficient dry air could be in place so that initial warm air advection could be spent just saturating the column and thus leaving most of our CWA dry at least for the first half of Thursday night. However, most of the global models are in agreement that decent isotherm packing sets up to our SW with H850 and H925 winds shifting SW which could lead to showers later in the night. Thus introduced chance POPs overnight with the highest probabilities in the SW CWA. The slow moving warm front should be our weather on Friday leading to a muggy day (dew points in the 60s) under mostly cloudy skies. We increased the threat for showers in eastern NY to chance/likely POPS as the warm front should reach into the Capital District during the day. In addition, the increased humidity could lead to CAPE values rising to 500 - 1000J/kg so have also introduced thunder chances. Just how far northeast the front travels is still uncertain as the models hint at our high pressure wedge remaining stubbornly in place over our western New England counties. Eventually, guidance shows the warm front pushing through our entire region sometime Saturday so continued chance POPs overnight Friday. We know from experience that the models this far in advance struggle with the timing of warm fronts so this is still a rather low confidence forecast. While we should be in the warm sector on Saturday with H850 isotherms at +14-16, only increased highs a bit compared to Friday as we should be partly to mostly cloudy. If more breaks of sun occur will have to increase temperatures. Humidity levels remain high again so kept the thunder threat in place, especially SW counties. A shortwave trough from the Great Lakes will move into Northeast with the models showing it shifting from positively tiled to neutrally tiled as it heads our way so continued chance POPS for all of Saturday due to PVA. The system`s cold front should then move through our area sometimes late Saturday/Saturday night. High pressure follows for Sunday/Monday bringing more comfortable humidity levels and seasonable temperatures around or just over 80. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... VFR conditions prevail at all terminals through at least 06Z. From previous discussion...lower clouds may develop and/or spread northward later this evening, with MVFR Cigs developing between 08Z-11Z/Tue, along with the possibility of embedded IFR, especially at KPSF. MVFR/IFR Cigs should gradually trend back to VFR between 14Z- 16Z/Tue. Latest runs of the HRRR, RAP, and NAM all bring an area of SHRA activity across the southern CWA during the overnight hours. Forcing is subtle with this feature. So have covered with VCSH. RAP shows Showalter indices getting close to 0, but given low confidence any SHRA activity will develop, much less thunder, have omitted thunder. Isolated/scattered rain showers may approach from the west after 08Z/Tue, especially at KGFL/KALB. These showers may linger until around 12Z-14Z/Tue. Additional showers and possible thunderstorms, isolated to scattered in areal coverage, are expected to develop mainly after 18Z/Tue. Again, with confidence low, have opted for VCSH for all terminals. Outlook... Tuesday Night: Moderate Operational Impact. Chance of SHRA...FG. Wednesday: No Operational Impact. NO SIG WX. Wednesday Night: No Operational Impact. NO SIG WX. Thursday: No Operational Impact. NO SIG WX. Thursday Night: Moderate Operational Impact. Chance of SHRA. Friday: Moderate Operational Impact. Likely SHRA. Friday Night: Moderate Operational Impact. Chance of SHRA. Saturday: Moderate Operational Impact. Chance of SHRA. && .FIRE WEATHER... High pressure will be moving east of New England tonight, as a weak disturbance will approach from Pennsylvania and New Jersey with some isolated to scattered showers. An upper level disturbance and a cold front will bring a chance of showers and thunderstorms tomorrow into early tomorrow night. High pressure returns with dry weather for the mid week. The RH values increase to 85 to 100 percent Tuesday, and Wednesday mornings, and lower to 50 to 60 percent tomorrow afternoon. The winds will be light from the south to southwest at less than 10 mph tonight, and 5 to 10 mph tomorrow. The winds will shift to the west to northwest at 5 to 10 mph Tuesday night into Wednesday morning. && .HYDROLOGY... No widespread hydro problems are expected the next several days. There will be a chance for isolated to scattered showers and thunderstorms between tonight and tomorrow, but not all areas will see rainfall. The rainfall amounts will vary, with some areas only seeing a few hundredths of an inch and other spots receiving heavier amounts. At this point, no flooding of rivers and streams is anticipated, but any thunderstorms will be capable of producing locally heavy downpours. After dry weather Wednesday into Thursday, some additional showers and thunderstorms are possible Thursday night into the weekend. Rainfall amounts are still variable from the guidance, though the northern half of the hydro service area could receive and inch or more of rainfall Thu night through Fri. For details on specific area rivers and lakes, including observed and forecast river stages and lake elevations, please visit the Advanced Hydrologic Prediction Service /AHPS/ graphs on our website. && .EQUIPMENT... The KENX radar will be down into Wednesday due to an azimuthal gearbox and motor problems. A Radar Operations Center technician will potentially arrive to assist the ALY tech staff repairing and further diagnosing the radar on WED. In addition, KGFL ASOS continues to experience intermittent outages. && .ALY WATCHES/WARNINGS/ADVISORIES... CT...None. NY...None. MA...None. VT...None. && $$ SYNOPSIS...Wasula NEAR TERM...OKeefe/Wasula SHORT TERM...Wasula LONG TERM...Speciale AVIATION...KL/OKeefe FIRE WEATHER...Wasula HYDROLOGY...Frugis/Wasula EQUIPMENT...
Area Forecast Discussion
National Weather Service Amarillo TX
626 PM CDT Mon Aug 14 2017 .AVIATION... For the 00z TAFs: We will begin the period in VFR, but KAMA and KDHT (possibly KGUY) will have thunderstorm chances later this evening which could being about MVFR conditions for mainly ceilings. Visibilities could also be reduced with the heavier precipitation thunderstorms. Recent trends have shown slightly less chance for thunderstorms, but felt KAMA and KDHT warranted a TEMPO group to account for these chances. Models were suggesting some fog/mist around during the overnight/morning hours as well, but these chances appear less likely at this time. This could be an addition to the next set of TAFs if conditions look favorable again. Unfortunately, KDHT has lost its visibility sensor due to recent thunderstorm damage from debris, so this TAF site will be without amendments until it becomes fixed. Guerrero && .PREV DISCUSSION... /Issued 416 PM CDT Mon Aug 14 2017/ DISCUSSION... Trend for the forecast continues with numerous periods of thunderstorm chances, especially the overnight periods. We seem to be in a perpetual pattern of increased night time precipitation chances. Otherwise, temperatures look to be right around normal for this time of year. Satellite imagery shows a cumulus field located across central parts of the Texas Panhandle basically aligned just ahead of a surface trough axis. West of this axis across eastern parts of New Mexico thunderstorms have already developed. Convective allowing models all have these storms pushing east into our forecast area late this afternoon/early evening. Ample instability will be around the Panhandles this afternoon and evening, but the wind pattern through the atmosphere doesn`t have much turning/shear with only 20-30 knots at most for 0-6km shear. Lower level wind speeds are especially weak. Storms will be very slow movers. Chances are some of these storms could be strong, but widespread severe weather does not look likely. Downdraft CAPE from the RAP shows values around 1000-1300 which could lead to some strong wind gusts. Overall, strong wind gusts appear to be the main threat as models indicate a linear segment developing and pushing through the Panhandles. Cells are discrete at the moment across New Mexico. In the upper levels there is a jet streak over the area with the left exit region over western parts of the forecast area leading to divergence aloft which should aid in thunderstorm development/support so rain chances look decent across portions of the forecast area, especially the Texas Panhandle. Trend continues to show chances continuing into the night, with thunderstorms pushing east of the forecast area by sunrise if dissipation doesn`t occur before then. For Tuesday, thunderstorm chances continue as well, but again widespread severe weather does not look likely. Ample CAPE will be around again but shear parameters are weak. Strong storms will again be possible tomorrow, and chances are wind will be the main threat for Tuesday. Through the next couple of days there will be a chance for moderate to heavy rainfall, especially localized within the stronger thunderstorms given the higher precipitable water values forecast. This is of course in addition to the slow storm movement anticipated the next couple days. Multiple thunderstorm chances are in the forecast through the extended. At this time, it does not look like severe weather is too likely Wednesday, and beyond this its too early to determine the potential for severe weather. Guerrero && .AMA Watches/Warnings/Advisories... TX...None. OK...None. && $$
Area Forecast Discussion
National Weather Service La Crosse WI
1031 PM CDT Mon Aug 14 2017 .UPDATE... Issued at 1032 PM CDT Mon Aug 14 2017 You know what they say about "the best laid plans". Such is the case with stratus sometimes, and the forecast has done a 180 regarding how much stratus is expected to develop, given a rapid loss of upstream stratus earlier this evening. As of a few hours ago, have steered the forecast heavily toward the idea of more dense fog development than stratus overnight, given the combo of clearing skies, light winds, and already very low temp-dew point depressions. In fact, already seeing the usual suspect sites dip below 1 mile for visibility, and per trends and the setup, believe we are headed toward a Dense Fog Advisory type of event later tonight. The one thing to watch remains a smaller patch of lower stratus developing southward out of the I-94 corridor of central Wisconsin. Based on RAP soundings and trajectories, looking like that axis of low clouds may expand for areas east of the Mississippi River, leaving plenty of real estate farther west to fog in. However, just where said clouds end up will make a huge difference regarding fog potential. Simply put, where stratus exists, fog won`t, and vice versa. Should be a good night to "test out" GOES-16 fog imagery. && .SHORT TERM...(This evening through Wednesday night) Issued at 213 PM CDT Mon Aug 14 2017 Local and regional radars still showing a few showers over portions of central Wisconsin in the cyclonic flow of the departing short wave trough over the Upper Great Lakes. These showers could possibly hold onto into the early evening over the far eastern portions of the area, otherwise the rest of tonight and into Tuesday look to be dry as high pressure over Minnesota and western Ontario briefly builds in over the area and as upper level ridging moves across the region. The ridging aloft and at the surface will get pushed east of the area starting Tuesday night. Water vapor satellite imagery currently shows the next system was over Oregon and northern California and will quickly move east toward the region. There looks to be several short wave troughs embedded in the mean trough with this system. The first of these short wave troughs will move across the region Wednesday with another for Wednesday night. As these waves move across the area they look to produce periods of weak to moderate pv advection in the 500-300 mb layer. The low level moisture transport looks respectable with these waves, but never looks to be overly strong. The leading and convergent edge of this moisture transport looks to start spreading in very late Tuesday night or early into Wednesday morning and then starts to diminish Wednesday evening as the first short wave troughs moves past the region. The warm air advection ahead of the short wave troughs looks to produce a period of 1 to 3 ubar/s (at times a little higher) of up glide on the 305K isentropic surface. The surface front currently across northern Iowa and southern Wisconsin will continued to get pushed south as the surface high builds in tonight. This front will start to return back to the area Wednesday and how far north is gets will determine how much instability and the coverage of storms that will occur. It currently appears that the general consensus from the 14.12Z models is that the front may get back into the southern portions of the forecast area Wednesday afternoon. Recent runs of the GFS brought in the most amount of CAPE, but the 14.12Z run now only shows 500-1000 J/Kg of ML CAPE south of about Interstate 90. The deep shear still looks to be lacking with maybe around 30 knots of shear in the 0-3 km layer. This could be enough for a strong storm or two but would not anticipate much severe weather. A larger concern is with the possiblity of some heavy rain. The models remain consistent in showing the warm cloud depths in the 3.5 to 4 km range with precipitable waters approaching 2 inches. This should allow for some locally heavy rain but with the recent dry stretch, the area should be able to take some rain and not concerned about any flooding issues at this time. .LONG TERM...(Thursday through Monday) Issued at 213 PM CDT Mon Aug 14 2017 The last of the short wave trough with this system will move across the area Thursday. By this time, the best low level support will be well past the area, being tied to the lead short wave troughs, so only expecting some lingering showers and storms to be around. Northwest flow aloft looks to set up behind this system which should allow another short wave trough to move across the Upper Midwest for late in the week into the start of the weekend. Differences between the GFS and 14.12Z ECMWF on how strong this wave may be and how much rainfall that could occur. Either way, enough to include a small rain chance for Friday and Saturday. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 641 PM CDT Mon Aug 14 2017 Scattered showers continue along a cold front slowly drifting east through the region, but just about to clear LSE by 00Z. Behind that front, confidence is very low regarding redevelopment of low clouds, as earlier expectations for widespread stratus have dwindled somewhat as clouds upstream have really mixed out. Gut feeling based on the setup is we may be dealing more with a fog setup for RST as skies clear out quite a bit overnight, with a period of VLIFR in dense fog now expected, centered either side of sunrise. LSE is much more tricky, as current low clouds over central Wisconsin could be shoved back southwest as the low level flow turns northeasterly overnight. Should that occur, a period of MVFR or even briefly IFR ceilings is likely. However, should clouds fail to materialize, as suggested by recent runs of the RAP model, a fog threat could develop in LSE. For now, have split the difference with some light fog and lower stratus centered either side of sunrise, but will really need to watch trends through the night. Fog and/or stratus should gradually lift through the morning hours, with scattered to perhaps broken ceilings into the afternoon with cumulus redevelopment as some thicker cirrus also arrives. Winds will remain under 10 knots through the period, shifting from the north to the east with time. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. IA...None. && $$ UPDATE...Lawrence SHORT TERM...04 LONG TERM...04 AVIATION...Lawrence
Area Forecast Discussion
National Weather Service Taunton MA
1012 PM EDT Mon Aug 14 2017 .SYNOPSIS... High pressure moves offshore overnight, allowing some scattered showers to move into the region late, especially along the south coast. The risk for showers lingers tomorrow, with an isolated thunderstorm possible before improvement arrives again tomorrow night. Dry conditions follow Wednesday and Thursday. A warm front approaches Friday, bringing increasing clouds, and scattered showers. Showers and Thunderstorms are possible Saturday as a cold front enters the region. A drying trend likely follows Sunday and Monday along with near seasonable temperatures. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... 1030 PM Update... Overall trend in the forecast remains on track for this evening. Did go ahead and increase precipitation chances across southern New England after 2 AM. Appears higher moisture and in the upper level jet dynamics will result in more widespread precip chances across the interior. Several runs of the HRRR have indicated this and it is shown in the 18z GFS as well as the 00z NAM. Otherwise dense fog remains on track for tonight across the CAPE and the Islands. Will have to continue to watch its northward progression to see if dense fog adv will need to be expanded. ================================================================ High pres remains in control this evening even as the column moisture loads along a strengthening WSW-ENE upper lvl jet in the form of CI. Filtered sunshine has still allowed temps to reach near their seasonal normal values except where sea breezes kicked in late this morning. Weak S flow already developing and as such noticed an area of marine fog/stratus already infiltrating Nantucket and sliding NNE. Will watch this for mainly the remaining Islands and Cape Cod for late this evening/overnight. Dense fog advisories may be needed for these areas. Further inland, while some low clouds are possible, less inclined to go with fog given the modest S flow and slow rise of overnight dwpts in comparison to direct marine influenced airmass over the Cape/Islands. Otherwise, will continue to watch band of light-mod rainfall attendant to the developing S shortwave/increasing jet sliding along the stalled front. Heights do dip late tonight and suggested modest overrunning N of the front attempts a lift N itself late. PWAT plume reaches 1.50-2.00 inches mainly along and S of the Mass Pike, but deeper moisture/instability associated with Gert will remain well S of the front, closer to the mid Atlantic states. Therefore, will cap POP increase to chance overnight, but could see some SCT light SHRA develop especially W MA/CT (closer to the right entrance region of the upper lvl jet) and along the immediate S coast (closer to the stalled frontal boundary. In any case only light totals of a quarter inch or less are expected at this time. Overnight mins will be milder than previous nights, mainly in the 60s even in coolest spots thanks to an increase in moisture and cloud cover preventing radiational cooling. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... Tomorrow... As upper lvl jet-streak becomes more refined it shifts its equatorward entrance region mainly SSE of New England later in the day even as secondary shortwave energy moves out of the Great Lakes and into central and N New England. This should allow initial round of SHRA to dissipate through the morning and shift offshore, focused more intently on the strengthening Gert and the front offshore which looks to capture it. Will maintain slight chance POPs mainly along the immediate S coast with particular focus on the Islands, closer to where the best synoptic support will focus later in the day. PWATs remain in the 1.50-2.00 inch range, supporting this area. Otherwise, with the secondary shortwave moving in from the W initially rising heights will give way to slight cooling aloft, enhancing mid lvl lapse rates from around 5.0C/km to start, closer to 6.0C/km by late afternoon mainly across NW MA. With modest moisture plume (still focused only on the S coast), this could lead to a period where CAPE values reach 700-1200j/kg but with a very tight gradient toward the E due to influence of mid lvl dry air and capping. This should limit focus for late day convection to mainly the most extreme W/NW zones, and most likely in N and central New England where diurnal heating will be better maximized. Shear will be the once enhancing component, as 0-6km shear values during the afternoon reach 45kt. Not expecting much in the way of severe due to these limiting factors, particularly the fact we remain split between two areas of synoptic lift to the NW and S. This agrees with latest SWODY2 which keeps marginal risk focused mainly across N New England. Highs a bit cooler than normal given a fair amount of early cloudiness. Tomorrow night... Weakening shortwave/front and upper lvl jet axis shift further offshore and become entangled in the future ET process of Gert. This will allow W flow and drier air to entrain through the remainder of the column even where mid lvl drying has not already occurred. Although a mild/moist start, trend will be toward clearing and gradual fog dissipation toward the early morning hours. Although dwpts will begin dropping, they are likely to remain in the 60s through sunrise, and with early cloud cover and continually W flow, lows should not dip below the low-mid 60s even in coldest spots. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... Highlights... * Pleasant summer weather Wednesday and Thursday * Risk for showers/Thunderstorms Friday and Saturday * Improving trend Sunday into Monday Synoptic overview... Persistent and anomalous northeast Pacific jet continues to eject numerous short wave troughs across the Canadian/US border resulting in the risk of showers/T-storms at times. In between systems, many hours of dry weather. As for temps, active northern stream jet suppresses subtropical ridge and its associated excessive heat and humidity across the southern states, resulting in temps here near normal for mid Aug. Temperatures... As mentioned above, active northern stream jet suppresses subtropical ridge and its excessive heat and humidity south of New England. Overall this pattern supports temps near normal thru the period. The warmest day in this stretch is likely Wednesday in the post frontal airmass with WNW winds providing some additional downslope adiabatic warming and keeping seabreeze offshore. Thus most beaches will warm into the low 80s Wed with mid to upper 80s in the coastal plain /including Boston-Providence corridor/ and the CT river valley. The core of this dry airmass settles over the area Wed ngt into early Thu, which will result in cooler but very pleasant temps Wed ngt into Thu morning with lows in the 50s, possibly upper 40s across northwest MA. Given this airmass and potential radiational cooling sided with the cooler MOS mins Wed ngt/Thu morning. Seabreeze and cooler airmass Thu will keep highs in the upper 70s and low 80s. In fact dew pts could be in the 40s! Quite comfortable. Cloud cover and convective chances Fri and Sat will also limit highs to the upper 70s and low 80s. A drying trend along with post frontal WNW flow Sun and Mon may result in slightly warmer temps. Precipitation... Post frontal airmass overspreads the region Wed and lingers into Thu. Thus dry weather both days. Then next short wave approaches Fri with increasing clouds and warm frontal rain/showers likely. Trough is slow to exit so risk of convection Sat ahead of the approaching cold front. PWATs climb to +1 to +2 standard deviations above climo so some heavy downpours are possible. Ensembles and deterministic guidance both suggest trough begins to exit around Sunday so a drying trend is possible Sun/Mon. Beach Forecast... Swells from tropical storm Gert are expected to arrive into our coastal waters Tue ngt and then peak Wed with southerly swells up to 7 ft possible. Therefore surf will become quite rough Wed along with increasing rips. Beachgoers will definitely need to exercise caution especially at south facing ocean beaches where surf and rips will be strongest. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. 1030 PM update... Dense fog continues across the Cape and the Islands. Will have to watch to see if LIFR conditions impact SE MA and portions of RI. ================================================================== Short Term /through Tuesday Night/... Tonight and tomorrow...Moderate confidence. Mainly VFR except extreme SE MA/RI terminals which could experience a period of IFR conditions in low CIGS with low vsby fog possible especially Cape/Islands. This burns off after sunrise. Some showers possible late tonight, mainly Islands. Otherwise, a few showers and isolated T-storms mainly W MA during the afternoon tomorrow. Tomorrow night...Moderate confidence. VFR gives way to another mix of IFR/MVFR mainly CT/RI and SE MA while the remainder stays mostly VFR, then as winds shift around to the W, transition back to VFR everywhere toward the morning. KBOS Terminal...Moderate confidence in TAF. Low probability for a few hours of MVFR conditions around 09z. KBDL Terminal...High confidence in TAF. Outlook /Wednesday through Saturday/... Wed and Thu...VFR likely along with dry weather. Light WNW winds Wed becoming onshore Thu. High forecast confidence. Fri and Sat...marginal VFR-MVFR in scattered showers/T-storms both days. Low risk for IFR conditions Fri night into early Sat. Forecast confidence high on trends but lower on specific details. && .MARINE... Forecaster Confidence Levels... Low - less than 30 percent. Moderate - 30 to 60 percent. High - greater than 60 percent. Short Term /through Tuesday Night/...High confidence. Through tomorrow... S winds develop with gusts to around 20-25 kt on the E waters during the day tomorrow, but brief. Otherwise, they remain below small craft thresholds through the day tomorrow. Seas will increase late tomorrow, but should remain below 5 ft through tomorrow evening. Otherwise, mix of fog and showers, particularly on the S ocean waters and waters surrounding Cape Cod during the overnight and early morning. Tomorrow night... Continued risk for showers early, but then dissipating late. The main issue will be a gradually increasing southerly swell which could reach as high as 7 ft on the southern open ocean waters by daybreak on Wed. Therefore, will likely a round of small craft advisories for mainly the southern waters. Outlook /Wednesday through Saturday/... Wed and Thu...fine boating weather both days, good vsby and dry weather. Only issue will be across the ocean waters especially south shore where large southerly swells up to 7 ft Wed, then eroding Thu. Forecast confidence is moderate to high. Fri and Sat...scattered showers/T-storms expected along with light to modest southerly winds. Vsby may lower in precip and esp Fri night in areas of fog. Mainly southerly wind waves with swells from Gert likely well offshore. && .BOX WATCHES/WARNINGS/ADVISORIES... CT...None. MA...Dense Fog Advisory until 10 AM EDT Tuesday for MAZ022>024. RI...None. MARINE...None. && $$ SYNOPSIS...Nocera/Doody NEAR TERM...Doody/Dunten SHORT TERM...Doody LONG TERM...Nocera AVIATION...Nocera/Doody/Dunten MARINE...Nocera/Doody
Area Forecast Discussion
National Weather Service Dodge City KS
700 PM CDT Mon Aug 14 2017 ...Updated Aviation Section... .SHORT TERM...(This afternoon through Tuesday) Issued at 1255 PM CDT Mon Aug 14 2017 Plentiful sunshine and boundary layer moisture (dewpoints in the 60s) will keep instability in place through this evening. 12z NAM forecasts CAPE of 2000 J/kg widespread by peak heating, locally higher. The problem is the triggering mechanisms necessary for convection are nebulous, weak and hard to identify. HRRR has shown some consistency developing thunderstorms along an outflow boundary along the I-70 corridor by peak heating. In the absence of strong forcing, orographic forcing and the higher terrain will become the primary focusing mechanism through this evening. Confident that convection will fire in the vicinity of the Raton Mesa soon, with subsequent propagation SE toward the TX/OK Panhandles. SPC`s marginal 5% wind/hail probabilities for this scenario just SW of SW KS look reasonable. 12z NAM also shows this solution, which would keep impacts limited to nil in SW KS. With moderate high CAPE and little shear/forcing, can`t rule out a thunderstorm at any location, but the odds are very low. Kept pop grids limited and conservative in the 20-30% range. Lows tonight in the 60s (probably holding near 70 SE of Dodge City). Tuesday...Stronger S/SE surface winds (averaging 15-25 mph) will maintain boundary layer dewpoints in the 60s. Southerly 850 mb flow increases progressively through the afternoon, near 25 kts, increasing further to near 40 kts with a modest low level jet Tuesday evening. NAM responds to this by forecasting stronger instability late Tuesday, with CAPE of 3000-3500 J/kg. During daylight Tuesday, forcing is still progged to be weak and less than obvious, so kept slight chances for most locales. Convection appears much more likely Tuesday night into early Wednesday, as as a midlevel trough approaches from the central Rockies, and a frontal boundary sinks south into SW KS. NAM/GFS MOS pops show a unanimous increase Tuesday evening, with ECMWF solutions strongly hinting at MCS generation over at least central Kansas through Tuesday night. Given the largely nocturnal timing of Tuesday and Wednesday`s expected convection, primary expectation is one of strong to severe multicell convective clusters producing marginally severe hail/wind. Highest risk will be near and NW of our NW zones, as SPC slight risk delineates. Temperatures Tuesday afternoon very near mid-August normals, within a few degrees of 90. .LONG TERM...(Tuesday night through Monday) Issued at 230 PM CDT Mon Aug 14 2017 Long term likely to start out active, as ECMWF shows strong forcing (for mid-August standards) arriving with a Colorado shortwave Tuesday night. MCS generation over central Kansas is anticipated, and storms are most likely across the NE zones near the I-70 corridor. Pop grids offered by the forecast blend are in the 50% range, and will need to be increased into the likely category over the next couple shifts. Areas of heavy rain and severe weather are expected. The cold front associated with the shortwave will usher in a northerly wind for Wednesday, effectively scouring the instability and pushing most of the CAPE into Oklahoma. Pops are very low Wednesday afternoon/evening, and confined to the eastern/SE zones. A few degrees of cooling expected Wednesday, in the mid to upper 80s, versus the lower 90s on Tuesday. Much of Thursday appears dry, but another round of thunderstorms is expected Thursday evening/night. 12z ECMWF suggests heavy rain from this probable MCS would favor the southern zones. 12z GFS in good agreement, with another shortwave in the NW flow aloft triggering a strong MCS along the Oklahoma border Thursday evening. Scattered thunderstorms still expected mainly across eastern sections late Friday. 12z MEX guidance suggests a notable warming trend this weekend, with afternoon temperatures into the mid 90s. With such wet ground across much of KS, and more MCSs probable between now and then, forecast grids only show a very gradual warmup this weekend (climbing to near/slightly above normal) by Sunday and Monday. It is still summer..... && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 657 PM CDT Mon Aug 14 2017 Latest TAF will reflect convection-free forecast with probability of thunder impacting terminals too low to include. Prevailing wind will remain out of the south with no significant wind shift forecast. Nocturnal wind speeds will be 6 to 9 knots with late morning to afternoon wind speeds 12 to 15 knots sustained. There will be a better opportunity for thunderstorms at the very end of this forecast period late tomorrow afternoon/evening. && .PRELIMINARY POINT TEMPS/POPS... DDC 68 92 69 88 / 10 30 50 30 GCK 67 91 65 86 / 20 30 40 10 EHA 65 91 64 85 / 20 30 50 10 LBL 68 94 68 87 / 20 30 50 10 HYS 68 89 68 86 / 10 20 50 40 P28 70 93 71 91 / 10 30 40 30 && .DDC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Turner LONG TERM...Turner AVIATION...Umscheid
Area Forecast Discussion...UPDATED
National Weather Service Austin/San Antonio TX
647 PM CDT Mon Aug 14 2017 .AVIATION.../00Z TAF CYCLE/ VFR conditions prevail across the region as of 2345Z and are expected to continue through at least 09Z overnight. However, greater low- level moisture is indicated to infiltrate north per NAM soundings and HRRR cross-sections by early Tuesday morning. Given the patchy nature of MVFR decks this morning and the suggested greater moisture content modeled for Tuesday morning, have placed MVFR decks for all sites. MVFR should appear in the 09-10Z range for KSAT/KSSF/KAUS and remain intact through 15-16Z. Even KDRT may see some patchy/brief MVFR ceilings for a few hours from 12-14/15Z. VFR conditions are expected thereafter for all sites through Tuesday afternoon. Surface winds will remain south to southeast at 5-10 knots overnight and then increase to near 10-14 knots with gusts to near 20 knots in the afternoon Tuesday. && .PREV DISCUSSION... /ISSUED 334 PM CDT Mon Aug 14 2017/ SHORT TERM (Tonight through Tuesday Night)... The latest water vapor satellite loop shows a plume of moisture stretched from northern Mexico across southwest Texas and into far northeast Texas. This plume of moisture is captured well by looking at model-derived 700-500 Theta-e values. The models agree in keeping this Theta-e ridge axis confined to the southern Edwards plateau and adjacent portions of the Rio Grande plains through the short term portion of the forecast. This should result in mainly isolated showers and thunderstorms for areas mainly north of a Del Rio to Rocksprings line. Coverage of showers and storms should be fairly low, so we will keep rain chances in the 20-30% range in the latest forecast. Otherwise, dry and hot conditions will continue across south central Texas. Daytime highs will range from the mid 90s to near 100, with overnight lows in the 70s. We may be close to Heat Advisory levels on Tuesday for areas along and east of I-35 as southeast winds will not allow much lowering of afternoon dewpoints. LONG TERM (Wednesday through Monday)... The heat will continue through the long term portion of the forecast. On Wednesday, we may very well be near Heat Advisory levels along and east of I-35 as afternoon dew points will likely not decrease much given continued southeast flow in the low-levels. Hi-res models continue to suggest the sea breeze could become active and we will mention a low chance for showers and thunderstorms for the coastal plains and Highway 77 corridor. In addition, we will continue a low chance for showers and storms across Val Verde county, where a mid- level moist axis will persist. For the remainder of the forecast period, the mid-level subtropical ridge axis will remain the dominant weather feature across south central Texas. Temperatures will continue to remain above normal across all areas. Highs will remain in the mid 90s to near 100 with lows generally in the 70s. With daytime heating and low-level mixing, we should see enough lowering of dewpoints in the afternoon to keep Heat Index values largely below Advisory levels. However, we continue to stress heat safety during this period of above normal temperatures. Opportunities for rainfall appear very limited and we will keep the forecast dry for Friday through Monday. && .PRELIMINARY POINT TEMPS/POPS... Austin Camp Mabry 77 99 78 99 78 / 0 0 - - 10 Austin Bergstrom Intl Airport 76 99 77 98 77 / 0 - - - - New Braunfels Muni Airport 75 100 76 99 76 / 0 - - - - Burnet Muni Airport 74 96 74 96 74 / - 0 - - 10 Del Rio Intl Airport 79 101 80 101 80 / - - 10 20 - Georgetown Muni Airport 76 98 77 97 76 / - 0 - - 10 Hondo Muni Airport 75 101 76 101 75 / 0 0 - 10 - San Marcos Muni Airport 75 100 77 99 76 / 0 - - - - La Grange - Fayette Regional 77 99 78 98 78 / - 10 - 20 - San Antonio Intl Airport 76 100 77 99 77 / 0 0 - - - Stinson Muni Airport 76 99 77 99 77 / 0 0 - 10 - && .EWX WATCHES/WARNINGS/ADVISORIES... None. && $$ Mesoscale/Aviation...Allen Synoptic/Grids...17 Public Service/Data Collection...Treadway
Area Forecast Discussion
National Weather Service Fort Worth TX
958 PM CDT Mon Aug 14 2017 .UPDATE... The isolated thunderstorms that develop during the afternoon dissipated after sunset. The thunderstorms over the Texas Panhandle don`t look as good as the complex did last night. In addition, the low level jet which helped keep the complex going overnight into this morning is much weaker than it was 24 hours ago. Thus feel more confident that those Panhandle storms will not make it across the forecast area tonight. The HRRR does indicate that some isolated warm advection showers may develop toward/shortly after daybreak west of I-35. At this time will just leave 10 percent PoPs with no mention of rain. 58 && .AVIATION... /Issued 642 PM CDT Mon Aug 14 2017/ VFR conditions will prevail at the Metroplex TAF sites through 06z Wednesday. There may be a few hours of MVFR ceilings at Waco as indicated by the TEMPO BKN015 between 11 and 15z. South winds at 6 to 9 knots tonight will increase to 12 to 15 knots Tuesday morning. 58 && .SHORT TERM... /Issued 343 PM CDT Mon Aug 14 2017/ /Tonight through Tuesday Night/ Afternoon satellite imagery shows some clearing in the wake of earlier morning convection across a good portion of North Texas with the exception of a narrow band of thicker mid level cloud cover right across the central part of the CWA. This is associated with a narrow ribbon of much higher 800-700mb RH that is streaming across the area from the west. At the surface, temperatures have warmed into the mid 90s where the sun has come out and remain in the mid to upper 80s under thicker cloud cover. There still remains an area of localized stronger surface convergence from near Abilene eastward to Mineral Wells. Over the last couple of hours, there has been an uptick in convective activity, likely aided by some weak forcing aloft in the westerly flow. Much of this activity is expected to remain across the far western counties and we`ll keep some 20% PoPs out there through the late evening. Otherwise, skies should be partly cloudy overnight will generally low rain chances. On Tuesday, we will have a little more influence from shortwave ridging as a trough deepens over the western U.S. This will result in strengthening southerly flow and likely will limit rain chances to 10% or less across the region. Tomorrow night, as the upper forcing spreads into west Texas, a complex of showers and thunderstorms is expected to develop over the Panhandle southward. This complex will likely move northeast with time and may impact some of our areas west of I-35, particularly our northwest counties. The upper flow won`t be quite as favorable for the complex of storms to move across the entire area. Dunn && .LONG TERM... /Issued 343 PM CDT Mon Aug 14 2017/ /Wednesday through Monday/ A somewhat unsettled flow will continue for our area mid week as a broad trough sits over the western CONUS and a series of impulses move overhead in southwest flow. Will likely see some lingering rain/storms to start off the day Wednesday and additional storm chances Wednesday night into Thursday morning, with higher chances over our northern counties. Temperatures on Wednesday and Thursday will be near seasonal norms for highs and slightly warmer for lows due to the expected overnight cloud cover. By Thursday, the upper ridge that has been parked over the Southeast U.S. should begin shifting westward...far enough to notice a drop in rain chances and an increase in temperatures across North and Central Texas for the end of the work week into the weekend. && .PRELIMINARY POINT TEMPS/POPS... Dallas-Ft. Worth 78 98 79 96 80 / 10 5 10 10 20 Waco 78 99 79 98 79 / 5 5 5 10 5 Paris 74 91 75 91 76 / 20 10 10 10 30 Denton 77 97 78 95 78 / 20 5 10 20 20 McKinney 77 96 78 94 78 / 20 5 10 10 20 Dallas 79 98 80 96 80 / 10 5 10 10 20 Terrell 77 96 78 95 78 / 10 5 5 10 10 Corsicana 77 98 78 96 78 / 5 5 5 10 10 Temple 76 98 78 98 77 / 5 5 5 10 5 Mineral Wells 76 97 76 96 76 / 10 5 20 20 20 && .FWD WATCHES/WARNINGS/ADVISORIES... None. && $$ 58/24
Area Forecast Discussion
National Weather Service Green Bay WI
819 PM CDT Mon Aug 14 2017 Updated aviation portion for 00Z TAF issuance .SHORT TERM...Tonight and Tuesday Issued at 233 PM CDT Mon Aug 14 2017 The latest RAP analysis and satellite/radar imagery show shortwave troughing moving across the western Great Lakes early this afternoon. Showers have been most widespread over northern WI so far today, though the mesoanalysis indicates 200-400 j/kg of surface based instability developing over central to eastern WI. Therefore, cannot rule out scattered showers and isolated storms developing in these areas later this afternoon. Latest HRRR also indicates this remains a possibility. Looking upstream, broken clouds remain over western WI and Minnesota, and it looks rather difficult to see these clouds mixing out through the afternoon. Forecast concerns revolve around precip trends through the evening, then cloud trends. Tonight...The shortwave trough will continue to move east across the region this evening before departing overnight. Area of deepest moisture suggests that northern WI will continue to see the greatest coverage of showers, but higher res models also show isolated to scattered activity lingering elsewhere through late in the evening or early overnight. In general though, the chance of precip will be diminishing from west to east tonight. Plenty of lower cigs upstream over Minnesota, so kept sky conditions in the mostly cloudy range through 12z. If any holes in the clouds develop, fog could develop, but confidence in location is rather low. With the cloud cover, temps ranging from near 50 in the north to low 60s in the south. Tuesday...Mostly cloudy conditions look to start out the day, then models indicate skies will partially clear into a cu field with the heat of the day. Otherwise, high pressure will ensure a dry and seasonable day. Highs ranging from the mid to upper 70s. .LONG TERM...Tuesday Night Through Monday Issued at 233 PM CDT Mon Aug 14 2017 High pressure over Lake Superior is expected to shift into eastern Ontario Tuesday night, but should still have enough influence to maintain a dry forecast over northeast WI. The previous shift mentioned that the current system had trended slower over the past several days, and a similar trend seems to be setting up for the midweek system. Models are have backed off on the arrival of precipitation on Wednesday, with WAA and a short- wave trof only bringing a chance of showers to our southwest counties in the afternoon. The stronger dynamics are set to arrive Wednesday night, with a couple short-wave trofs, a H8 warm front and the RRQ of an upper jet (late). In addition, precipitable water values are forecast to increase to 1.6 to 2.0 inches, so moisture will be plentiful. Plan to carry likely pops over the entire forecast area. Likely pops will continue in eastern WI ahead of a cold front on Thursday, but precipitation should become more scattered elsewhere as a dry slot arrives. Marginal instability and shear support a low-end severe weather threat ahead of the cold front, but only if the surface low tracks far enough north to bring the warm sector into the forecast area. The ECMWF supports a low track farther to the south, which would suggest more of a heavy rainfall threat than a severe threat. Significant CAA will occur in the wake of the low late Thursday into Thursday night, with H8 temperatures falling to +9 to +10 C. The cool NNW flow could lead to some lake-enhanced showers in far north central WI and over Door county. High pressure will bring a period of mainly dry weather and gradually moderating temperatures through the weekend. An approaching frontal boundary may trigger scattered showers and thunderstorms early next week, but there are timing differences in the medium-range models, so details will need to be ironed out later. && .AVIATION...for 00Z TAF Issuance Issued at 819 PM CDT Mon Aug 14 2017 SHowers and isolated thunderstorms will exit eastern Wisconsin late this evening, with some clearing expected across the northcentral and central portions of the state. Dense fog may form where skies clear, and conditions below minimums possible at D25, LNL, ARV, EGV, RHI, TKV, and RRL possible later tonight into early Tuesday morning. MVFR/IFR conditions elsewhere later tonight. Skies should clear by midday Tuesday. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM.....MPC LONG TERM......Kieckbusch AVIATION.......RDM
Area Forecast Discussion
National Weather Service Grand Rapids MI
1001 PM EDT Mon Aug 14 2017 LATEST UPDATE... Update .SYNOPSIS... Issued at 243 PM EDT Mon Aug 14 2017 A few spotty showers and storms will remain possible for areas mainly east of U.S.-131 this afternoon. These are not expected to be too strong. Additional showers and storms are expected to move in late this evening and overnight tonight. The best chance for more widespread rain will be along and south of I-96. Again, storms are not expected to become severe. Rain will move out early Tuesday, with clearing then taking place. The next chance of rain will then come Wednesday night through Thursday as the next system moves through the area. Showers will linger into early Friday before conditions dry out and cool down. && .UPDATE... Issued at 1001 PM EDT Mon Aug 14 2017 I have not significantly changed our going forecast for the overnight period. There as that northern stream shortwave that moves through this area during the early morning hours of Tuesday. We get into the right entrance region of the upper jet and that helps strengthen the low level jet (as shown by the RAP model and the HRRR run after run tonight). The current radar and surface observations support both of those models so I have little reason to question that they suggest. It should be noted however that the ESRL HRRR is much drier for SW MI tonight, showing nearly no precipitation at all. Given the jet entrance region lift that comes through and that the showers the other models are forecasting to move in are there, I see no reason to change the forecast. It should be noted the instability shown on the model soundings overnight is not impressive, I could see this being more of a shower event than a thunderstorm event. I have put isolated thunderstorms instead of thunderstorms likely. && .SHORT TERM...(This evening through Wednesday night) Issued at 243 PM EDT Mon Aug 14 2017 Our main items of interest include residual storms this afternoon, rain potential tonight, and then rain trends for Wed/Wed night. Our main changes in the forecast include higher rain chances tonight down south, and a delay in rain chances Wed/Wed night. A few showers and storms have gone up this afternoon as expected across interior portions of Central Lower. These have fired along a convergence zone where the lake breeze/shadow from Lake Michigan is meeting up with the srly flow inland. Storms are pulsing up and down, likely due to the thin CAPE profile evidenced by fcst soundings. These will continue to be possible along this convergence line, and will likely gradually shift east until they diminish toward sunset. We have increased the rain chances for areas along and south of I-96 for tonight. Models are in fairly good consensus in bringing a swath of rain, some decent amounts, late this evening and overnight. This is the result of a stronger surge of moisture transport via a 30 knot llj, aimed at the srn half of the area. These storms will be elevated in nature, with thin CAPE profiles once again. Some heavier downpours will be possible, but we are not expecting much wind or hail with these. Rain will come to an end early Tuesday, with clearing taking place as the system moves east of the area. The next chance of rain then comes very late Wed afternoon, and Wed night. We will see ridging move by just north of the area from late Tue into Wed giving us dry weather and seasonable temperatures. Return flow will start to increase on Wed behind the front, but this has been trending slower with time. The slower trend is likely as a result of the system organizing to our west being a bit stronger. We will have chances Wed night, but the latest trends would even push the best rain chances to Thu. .LONG TERM...(Thursday through Monday) Issued at 243 PM EDT Mon Aug 14 2017 During the extended period...the flow pattern in the middle atmosphere will transition from a blocking pattern with a low over Quebec to a more summerlike pattern...with a high over Texas and most of the significant short wave energy well north into Canada. This will result in above normal temperatures for West Michigan... especially next week. The best chance for precipitation locally will be Thursday into Thursday night. Severe potential continues with this system as it rotates through the region. High pressure will be in control for most of the weekend...with another system poised to move into the region later Monday into Tuesday. Highs will range from mid 70s north to lower 80s south on the mid and upper 70s Friday and Saturday...warming to lower 80s by Monday. Lows will range through 60s on Thursday the lower 60s Friday...and from the middle 50s to near 60 Saturday and Sunday. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 736 PM EDT Mon Aug 14 2017 At this point all TAF sites are VFR and anticipate they will remain so till around 06z or so. There is a northern stream shortwave currently moving through WI/MN with showers and some thunderstorms. This area will move through our TAF sites between 06z and 12z. Looking at an ensemble of most of the high resolution models it looks like all of our TAF sites will see showers overnight. It is questionable if there is enough instability for thunderstorms, so I put VCTS and called that good for now. There is also a cold front pushing south behind the surface wave that moves through this area early Tuesday morning. The combination of the rain and the cold front will more than likely result in some MVFR or even IFR cigs around sunrise Tuesday. The push of cooler and dry air is strong enough so that skies should clear by late morning at all of our TAF sites. The bottom line is VFR till 06z, MVFR with showers and isolated thunderstorms from 06z till around 12z, then clearing by 16z. && .MARINE... Issued at 243 PM EDT Mon Aug 14 2017 No marine headlines expected through Wednesday at this time. Winds should remain fairly limited through most of Wednesday, except for a brief possible uptick Tue afternoon/evening on the backside of the system moving through tonight. We expect winds should stay below 20 knots with that increase. && .HYDROLOGY... Issued at 1144 AM EDT Mon Aug 14 2017 Isolated to scattered showers may result in a brief dampening of the ground in localized spots this afternoon. Better chances for rain will come in overnight tonight and early Tuesday morning. Measurable rainfall of around one-tenth of an inch may fall. Some locations could receive a couple of tenths of beneficial rainfall. A more active pattern is expected to setup for the midweek period as a result of a strengthening wave that passes over the Great Lakes Region. A deepening trough may result in showery activity toward next weekend. It is possible for 5-7 day totals to approach an inch or more in spots. Given recent dry weather, growing moisture deficits, and near/below normal river levels, flood concerns remain low. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...None. && $$ UPDATE...WDM SYNOPSIS...NJJ SHORT TERM...NJJ LONG TERM...MWS AVIATION...WDM HYDROLOGY...JAM MARINE...NJJ
Area Forecast Discussion
National Weather Service Gray ME
939 PM EDT Mon Aug 14 2017 .SYNOPSIS... A cold front will move south out of Canada Tuesday triggering showers and thunderstorms by late morning. High pressure builds in Wednesday before another low pressure system affects the region Thursday night and Friday with the potential for a period of heavy rain. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... 940 pm Update: Quiet night with latest temps from obs on track. No changes needed. 655 pm Update: Another quiet night. The veil of high clouds over southern areas will gradually exit to the east over the next several hours based on extrapolation of h7 trajs. Input mesonet data with only minor tweaks needed to temps. Made some adjustments to sky cover based on satellite to reflect clear conditions across the north and mountains with the solid area of high clouds only in southern areas. Previous Discussion: Water vapor imagery shows moisture streaming in from the southwest in the mid to upper levels of the atmosphere. Temperatures had warmed into the 70s and 80s and this combined with low humidity has resulted in a very pleasant day. A sea breeze has formed and will be pushing inland shortly capping highs near the coast. High pressure dominates the region through tonight before being shunned offshore. Tropical moisture moving into the region from TS Gert from the south will result in higher dew points and more clouds overnight. The increasing low levels will result in patchy fog in the valleys and other sheltered areas with denser areas of fog and very low stratus over the Mid Coast. The latest SREF and HRRR runs support denser fog in this area. Overnight lows will drop into the 50s north to the lower 60s south. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... On Tuesday the upper low over northern Canada will drop south and stall north of the Great Lakes. A lead vorticity maxima currently over northern Minnesota will will eject push a cold front through New England. A the same time Gert will begin to eject into the Atlantic somewhere near the Carolinas, pushing additional moisture northward. Scattered showers and thunderstorms should form generally ahead and along the frontal boundary tomorrow. Precipitation will spread from north to south along with decent frontogenetical forcing. Ample heating (highs should warm into the upper 70s to lower 80s) should take place ahead of the boundary which will result in decent instability. This along with the approaching short wave will allow convection to blossom and contribute to a few strong storms. Small hail and gusty wind terminology was included in the forecast in agreement with SPC`s day two outlook which has much of NH and western Maine in a marginal risk for severe thunderstorms tomorrow. A few stronger rotating cells are likely with about 50 kts of shear in the 0-6km layer. Individual supercells will move ENE with the potential for heavy rain, marginally severe hail, and damaging winds. Expect this activity to die out with the loss of heating and as forcing for ascent moves away. The front itself should move offshore by Wednesday morning bringing an end to precipitation. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... The models have come into better agreement over the past 24 hours with decent agreement on the long wave pattern into next weekend. The omega block centered across the Canadian Prairies...with the eastern anchor trough found across eastern Canada and New England...will break down early in the extended period. We`re left with shortwave ridging for Wednesday and Thursday. The next shortwave impulse and associated surface reflection will then approach from the Great Lakes for Thursday night and the ECMWF has come into much better agreement with the remainder of the model suite on a slower arrival time with this system. Unfortunately...shortwave energy now carves out a trough axis to our west by the start of the weekend. This promises a period of onshore flow and unsettled weather for the weekend as a complex area of low pressure slowly traverses New England. In the dailies...A ridge of high pressure will build into the region for Wednesday and Thursday. Low pressure approaches from the Great Lakes for Thursday night and Friday. This slow-moving system is then expected to linger into the upcoming weekend. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... Short Term...Low clouds and stratus will form tonight, mainly on the Mid Coast of Maine but also for LEB and HIE as moisture increases and forcing for ascent nears. Otherwise RKD and AUG look to be hardest hit. VFR conditions are expected on Tuesday after any stratus and fog burns off, but a few showers and thunderstorms may bring briefly lower ceilings in heavy rain. LEB and HIE will be the first and most likely to experience -TSRA. There will be a wind shift to the west northwest late Tuesday night as the front moves offshore. Long Term... Thu night - Sat...Areas of MVFR in shra/tsra with lcl IFR conditions psbl in fog. && .MARINE... Short Term...Conditions are expected to remain below small craft thresholds through Wednesday morning. Long Term... Wed PM...Winds and seas may briefly approach small craft outside the bays. Fri PM - Sat...Winds and seas may approach small craft on all waters. && .EQUIPMENT... The weather radar at Gray (GYX) will be down for maintenance until approximately Tuesday, August 14th. During that time technicians will be installing important upgrades. This work has been scheduled to minimize any potential impacts to office operations. During the outage, radar coverage is available from adjacent radar sites including Burlington-Vermont (KCXX), Taunton- Massachusetts (KBOX), and Hodgdon-Maine (KCBW). Also, the radar at Albany (KENX) suffered a failure that has been attributed to azimuthal motor/gear issues. It is expected to be down for several days. && .GYX WATCHES/WARNINGS/ADVISORIES... ME...None. NH...None. MARINE...None. && $$
Area Forecast Discussion
National Weather Service Houston/Galveston TX
1009 PM CDT Mon Aug 14 2017 .UPDATE... Radar imagery show showers have dissipated across Montgomery and Harris counties this evening, leaving clear skies across much of SE TX. Low temperatures tonight will remain above normal for this time of year, with low 80s along the coast and upper 70s further inland. Minor changes were made to the forecast this evening. Expecting a small break Tuesday from the dominant 500 mb ridge which weakened and shifted west this afternoon, leaving us in an area of weakness throughout the day tomorrow. Went ahead and raised PoPs slightly to account for the better coverage indicated by the 00Z HRRR and RAP13 short term guidance. With the seabreeze, bay breeze, and potential pocket of positive vorticity (as indicated by the 18Z GFS) moving across the region acting as possible forcing mechanisms for tomorrow`s activity, scattered shower and thunderstorm development will be possible mainly along the coast and southeastern counties of the CWA. Tomorrow still looks to provide the best chance of precip through the rest of the week. Although tomorrow will once again be another warm day, areas that see the convection tomorrow could result in their high temperatures being a degree or two cooler than what we`ve seen over these last few days. Therefore, forecast high temperatures along the coast and eastern counties are in the upper 80s to mid 90s. Regions that do not see precip tomorrow will still be battling the heat with high temperatures reaching up into the mid to upper 90s once again. By Tuesday 00Z, upper level ridging begins to build back in from the east and should shift overhead, parking itself over SE TX through the remainder of the week. Hathaway && .PREV DISCUSSION... /ISSUED 657 PM CDT Mon Aug 14 2017/ AVIATION... Other than some (vicinity) thunder in and around CXO this evening...VFR will prevail through the sunrise hour. Periodic short-lived MVFR ceilings over far interior hubs...scattering out to a FEW-SCT cumulus field tomorrow afternoon. An analogous scenario with light onshore winds and isolated late day shower activity. 31 PREV DISCUSSION... /ISSUED 313 PM CDT Mon Aug 14 2017/ DISCUSSION... The main driver of the forecast over the next several days appears to be the strength and location of ridging aloft, which will nudge temperatures modestly up or down, and determining whether there will be potential for scattered showers and storms, or a more suppressed atmosphere. Day to day changes will likely be rather small into the weekend, with only subtle changes. Thus, the focus will almost certainly continue to be the characteristic hot, humid summer of Southeast Texas. Luchs NEAR TERM [Through Tonight]... Through 2 pm, the radar has been pretty quiet, outside of a couple isolated showers in Liberty County. Though some subtle features could be seen in the low level GOES-16 water vapor imagery, subsidence under the ridge appears to largely be winning out, except in the vicinity of Galveston Bay (which likely explains the isolated showers in Liberty County). Meanwhile, after a fast start, temperature rises this afternoon have leveled out somewhat. The idea of a hot, humid day that sees the heat index near the coast top out just below heat advisory thresholds still seems safe. This evening, any showers that do manage to initiate today should wind down very quickly. However, despite the loss of solar heating, temperatures aren`t likely to go into a tailspin. With overnight dewpoints in the middle 70s to around 80, low temperatures tonight will again be very warm. Houston, Hobby Airport, and Galveston are all currently at least tied for their record warm mins today, and though it may be close, there`s a strong chance all of them hold on. SHORT TERM [Tuesday Through Wednesday Night]... The upper ridge looks to briefly weaken Tuesday, and both the GFS and Euro suggest some subtle midlevel vorticity slides across Southeast Texas. But don`t want to sell out too hard on PoPs, as the NAM modestly lowers heights, but doesn`t show any vort lobes and as a consequence looks pretty dry. Put the highest PoPs in that subtle Galveston/Gulf seabreeze convergence zone, which may benefit most from the lower heights aloft. Temperatures may be a touch (read: a degree or two) cooler, but with such a brief, modest change in the column and such a warm start to the day, there should be little to no change in temps. After that, look for things to settle back down Wednesday as ridging attempts to build in yet again from the east. Again, we`re only looking for modest changes in heights and surface pattern, so changes will be minimal, but may ultimately lock in Tuesday as the best potential for rain, as Wednesday backs down to isolated or widely scattered development. Both days again look to have heat index values that are on the fringe of the heat advisory threshold again. Whether an advisory is necessary will likely depend on sky cover and the state of boundary layer moisture, determining if dewpoints will mix out or stay high enough to boost the heat index past 108. Both aspects are very difficult to forecast from much range, so it seems calls on any advisories will be a day to day call. Expect this trend to continue through the week. LONG TERM [Thursday Through Monday]...Discussion Pretty good agreement in the guidance for a 595-ish midlevel high stacked over a surface high to develop over the northern Gulf coast and drift westward late in the week. This seems likely to clamp down on rainfall potential pretty well for the late week, with only modestly better potential this weekend on the backside of the high. Another thing to watch for this weekend that`s emerged in the 12Z guidance is a TUTT moving across the Gulf behind this ridge. This may help to boost rainfall potential by lowering heights and increasing vorticity advection over the region. However, this is a relative newcomer with this morning`s model runs and we`re looking nearly a week out, so it`s probably best not to commit too much to a specific scenario. Though a ridge in the area of 595 dm isn`t astoundingly strong by the area`s standards, we should see response in temperatures from subsident warming over time as it moves slowly along. It may not be quite as apparent near the coast with the moderating water, but do introduce isolated triple digit temps in the northwest towards College Station late in the work week. MARINE... Moderate onshore winds (mainly from the south) will persist for the next several days with caution level speeds expected during the overnight hours. Winds will gradually weaken toward the end of the week and over the weekend. 42 CLIMATE... Houston Hobby is on track to break a record high min temp today. Low so far is 81, record is 80 (2015). Both Galveston and City of Houston (IAH) are on track to tie their previous records. Galveston with 84 in 2010 and Houston with 81 in 1951. && .PRELIMINARY POINT TEMPS/POPS... College Station (CLL) 77 98 78 98 78 / 10 10 0 20 10 Houston (IAH) 79 95 81 94 81 / 10 40 10 20 10 Galveston (GLS) 84 90 85 89 85 / 10 30 20 20 10 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 9 AM CDT Tuesday for the following zones: Coastal waters from Freeport to the Matagorda Ship Channel out 20 NM...Coastal waters from High Island to Freeport out 20 NM...Galveston Bay...Matagorda Bay...Waters from Freeport to the Matagorda Ship Channel from 20 to 60 NM...Waters from High Island to Freeport from 20 to 60 NM. && $$ Update...08
Area Forecast Discussion
National Weather Service Lincoln IL
838 PM CDT Mon Aug 14 2017 .UPDATE... Issued at 832 PM CDT Mon Aug 14 2017 The latest surface map indicates a weak cool front over east central Iowa early this evening. This boundary is expected to slowly edge southeast into our area but not until tomorrow morning based on the latest HRRR model. Shower development has been few and far between late this afternoon into early this evening as the upper wave and forcing has shifted off to our northeast. Latest ILX and DVN soundings indicating rather weak mid level lapse rates and a lack of deep moisture in the sounding profiles. Will continue to carry the isolated wording across the north as the front settles into our area Tuesday morning. With the boundary in our area on Tuesday combined with some daytime heating, isolated to widely scattered convection will be possible in the afternoon, but again, large scale forcing will not be present, so coverage looks to be rather limited with any convection that does develop, and that would be tied closer to where the front sets up tomorrow. Other than some minor tweaks to the early evening temperatures, no other changes were made to the grids that would require a forecast update at this time. && .SHORT TERM...(This evening through Tuesday) ISSUED AT 250 PM CDT Mon Aug 14 2017 19z/2pm surface analysis shows 1009mb low over southeast Minnesota with weak cold front trailing into Nebraska. As the low moves slowly eastward over the next 12-24 hours, the frontal boundary will sink southward and eventually stall across central Illinois by Tuesday morning. While boundary layer moisture has been on the increase today resulting in surface dewpoints rising into the middle to upper 60s, deep-layer moisture will remain sparse through the period. As a result, areal coverage of convection associated with the boundary will be low. Based on 12z NAM and latest HRRR, have included slight chance PoPs along/north of a Macomb to Bloomington line tonight. The front will become stationary near the I-72 corridor on Tuesday, with isolated to widely scattered convection developing in its vicinity. Have therefore carried low chance PoPs across all but the far SE KILX CWA by Tuesday afternoon. Low temperatures tonight will be in the middle to upper 60s, while highs on Tuesday reach the middle 80s. .LONG TERM...(Tuesday night through Monday) ISSUED AT 250 PM CDT Mon Aug 14 2017 A short-wave trough will cross the Rockies on Wednesday, invoking an increasingly moist southwesterly flow downstream across the Midwest. As a result, showers and thunderstorms will become more prevalent across central Illinois by Wednesday afternoon, with 30-40 PoPs warranted across the board. The best rain chances of the entire forecast period will materialize Wednesday night into Thursday morning as the upper wave and its associated cold front approach from the west. Thanks to deeper moisture profiles, this system will produce widespread showers/thunder, warranting likely PoPs everywhere Wednesday night...then just across east-central Illinois by Thursday morning. The front will pass through the KILX CWA by midday Thursday, resulting in rapidly diminishing rain chances by afternoon. A slightly cooler/drier airmass will arrive in the wake of the front Thursday night into Friday, with lows dropping into the lower to middle 60s and highs on Friday staying mostly in the lower 80s. After that, both the 12z GFS and ECMWF suggest the next short-wave will arrive by Saturday. The GFS remains more aggressive with its QPF, while the ECMWF indicates much less precip with this feature. At this time, will increase cloud cover and go with just a slight chance for showers/thunder on Saturday until better model consistency is achieved. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 605 PM CDT Mon Aug 14 2017 VFR conditions through this evening then we will need to watch for the potential for MVFR conditions (cigs & vsbys) after 09z, especially across the north, as a frontal system slips south into our area. Isolated showers and TSRA will be possible across our northern TAF sites but coverage appears to be too limited to include in the forecast. Any MVFR cigs across the north will gradually lift after 15z on Tuesday with sct-bkn cumulus expected during the afternoon across most of the area. Once again, with a frontal boundary stretching across central IL, we could see an isolated TSRA develop during the afternoon. Surface winds tonight will be light south to southwest with winds shifting into a northerly direction at PIA and BMI, while winds at SPI, DEC and CMI will be westerly at 5 to 10 kts during the day. && .ILX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...Smith SHORT TERM...Barnes LONG TERM...Barnes AVIATION...Smith
National Weather Service Jackson KY
1038 PM EDT Mon Aug 14 2017 .UPDATE... Issued at 1037 PM EDT MON AUG 14 2017 Have continued to tweak pops throughout the evening based on latest radar trends and hi-res guidance. Currently scattered to numerous showers are located over far the far SE portion of the CWA, with lightning/thunder continuing to wane. Have thunder diminishing completely over the next few hours. Otherwise, reduced pops to only scattered for the rest of the night based on latest hi-res model trends. Also updated the forecast through tomorrow to change to coverage wording in the weather grids instead of probabilities. Finally, freshened up the near term grids for temps, dew points, and winds to make sure they were on track with current conditions. All changes have been published and sent to NDFD/web. A new set of zones was also sent out to reflect latest changes in pops/weather for overnight. UPDATE Issued at 717 PM EDT MON AUG 14 2017 Made a couple updates, mainly to pops and weather, over the last few hours. Tried to get pops more on track with current radar trends. Lended a bit towards the HRRR for model guidance as it seemed to be initializing well and has thus far panned out pretty well. However, some continued adjustments and updates are expected throughout the rest of the evening as things evolve. Also updated the near term forecast for temps, dew points, and winds, to make sure they were on track with current conditions. All updates have been published and sent to NDFD/web. A new forecast package was sent out to reflect updated weather earlier in the afternoon. A new HWO will be sent out later this evening once remaining thunder has tapered off. && .SHORT TERM...(This evening through Tuesday night) Issued at 347 PM EDT MON AUG 14 2017 ...Locally heavy rains possible this afternoon and overnight... Scattered thunderstorms with very heavy rains have moved into the southwest part of the forecast area. These will continue to move northeast but should decrease in intensity as we move into the evening. Will mention locally heavy rains in the updated hazardous weather outlook for the remainder of the afternoon and evening. As we move into the overnight period another wave of showers should affect the southern and central part of the forecast area as a subtle short wave ripples through the mean flow. The GFS and NAM MOS guidance as well as the blended forecast guidance point towards likely to high chance rain probabilities for the overnight period. Will follow that idea for tonight. A concern is locally heavy rain tonight. The excessive rainfall outlook does not include SE KY, but with the marginal risk right along the TN and VA border this will be something to watch especially with precipitable water right around 2 inches. We also received a spotter report of 1 inch of rain in Floyd County this morning with showers, and this corresponded well with radar estimates for a small part of the county. This helped highlight the efficient rain production of showers in the current warm moist air mass. The NAM continued its trend of trying to pinpoint an area of heavy rain tonight on the order of 2-3 inches, and is still trying to point towards the west central part of the forecast area. Pinpointing the location of such a local high rain amount cannot be relied upon, and as noted by the midnight forecast shift the NAM has been rather inconsistent and an outlier when compared to the other models in recent runs. This continued with the 12z runs. Despite that, with the rainfall report this morning of 1 inch, the current radar trends, the efficient rain production of the shower and storms we`ve already seen, and the expected efficiency of showers and storms this evening into the overnight, any showers and storms will need to be monitored for excessive rain. On Tuesday more showers and thunderstorms will be possible, but chances will be on a downward trend through the day. .LONG TERM...(Wednesday through Monday) Issued at 347 PM EDT MON AUG 14 2017 Warm humid conditions and a daily threat of showers and storms will continue through the remainder of the week. The best chances for showers and storms will come Thursday night into Friday with the passage of a slow moving cold front. Slightly cooler and less humid air will arrive for the weekend with dewpoints falling into the lower to middle 60s. While it is still a week away, current indications are that viewing of the partial eclipse here in eastern KY will be okay, with no rain or extensive cloud cover in the Monday forecast at this time. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) ISSUED AT 826 PM EDT MON AUG 14 2017 Scattered showers are continuing to affect eastern Kentucky this evening, with at least some chance for all TAF sites to be impacted. Coverage may possibly increase near dawn in the far SE portion of the state. Loss of instability should prevent any new thunder development throughout the overnight, so just went with VCSH at all TAF sites. By tomorrow, warming temps could lead to more thunderstorm development in the afternoon, but given uncertainty whether any particular TAF site will be impacted, kept with VCTS at this time. Winds will remain light and variable throughout the period. The main concern for this TAF is the potential for fog development as well as lower clouds. With abundant moisture across the region, still leaning towards LIFR or conditions late tonight through dawn tomorrow. However, can`t rule out some brief drops below this CAT. Conditions should begin improving by daybreak tomorrow, but expected BKN cloud cover in the low end VFR range through the afternoon. Any showers/thunderstorms that impact a TAF site could also have temporary adverse impacts on the visibility. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...JMW SHORT TERM...SBH LONG TERM...SBH AVIATION...JMW
Area Forecast Discussion
National Weather Service North Platte NE
719 PM CDT Mon Aug 14 2017 .SHORT TERM...(This evening through Tuesday) Issued at 314 PM CDT Mon Aug 14 2017 The HRRR, HRRR EXP and GFS were the basis for rain chances tonight and Tuesday. Two or more MCS`s should form. One tonight and a second or third Tuesday. The system tonight is spawned off the Big Horns and Laramie range this afternoon. This storm activity is expected to grow upscale, mainly affecting SD this evening. Some of the HRRR solns show isolated activity over the Sandhills late this afternoon ahead of the WY storms. There is considerable variability in the extent of upscale growth across Wrn Neb this evening with some solns showing more storm coverage than others. POPS are limited to 30 percent for this reason. Isolated showers and thunderstorms are possible in many areas Tuesday morning. The extent of upscale growth tonight could deeply influence the sfc focus Tuesday across Neb. The consensus of the HRRR EXP, NAM and GFS suggested storms firing on a frontal boundary laying somewhere across the cntl Sandhills...perhaps near or along highway 2. The NAM nest and HRRR EXP show upscale storm growth across the ern Sandhills which drops south into Custer Co. where a flash flood watch will be posted. Rain activity should continue well into Tuesday night, generally along and east of highway 83. The model consensus shows sfc dew points in the upper 60s to around 70 with deep moisture aloft supporting storms capable of heavy rainfall. WPC suggested the increasing low level jet could support back building or train storm behavior. .LONG TERM...(Tuesday night through Monday) Issued at 314 PM CDT Mon Aug 14 2017 Rain activity should continue well into Tuesday night, generally along and east of highway 83. The model consensus shows sfc dew points in the upper 60s to around 70 with deep moisture aloft supporting storms capable of heavy rainfall. WPC suggested the increasing low level jet could support back building or training storm behavior. The models then show a second, post-frontal, disturbance moving through Wednesday morning. Dry weather is expected Wednesday evening and Thursday with cool temperatures. A northwest flow disturbance may produces showers and thunderstorms Thursday night. Dry weather is in place Friday through Monday with just an isolated rain chance. This is the result of a warming trend as H700mb temperatures rise toward 14C by Monday which should cap most opportunities for thunderstorm development. Still, a blend of bias corrected model temperatures and the National blend of model data produces highs in the upper 80s to around 90. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 651 PM CDT Mon Aug 14 2017 Isolated thunderstorms are possible across portions of southwest Nebraska this evening, then later tonight a cluster of thunderstorms is expected to move out of the panhandle into north central Nebraska. Those could move across the KVTN TAF site, but for now no thunder is expected at KLBF. Winds tonight into Tuesday morning will be southeast around 10 KTS. && .HYDROLOGY... Issued at 314 PM CDT Mon Aug 14 2017 3-hour flash flood guidance has fallen to around 2 inches across parts of Southwest and Ncntl Neb. The key feature could be the 7-day rain totals across parts of Custer and Frontier Counties of 3 to 7 inches. Conditions will become favorable for thunderstorms and heavy rainfall Tuesday afternoon-Tuesday night. Ambient precipitable water increases to over 1.5 inches and winds aloft are fairly weak and unidirectional. The models show a frontal boundary dropping into Ncntl Nebraska Tuesday night which could be the focus to storm development. The forecast places Custer County in a flash flood watch Tuesday afternoon through early Wednesday morning. && .LBF WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch from Tuesday afternoon through Wednesday morning for NEZ038. && $$ SHORT TERM...CDC LONG TERM...CDC AVIATION...Taylor HYDROLOGY...CDC
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
936 PM CDT Mon Aug 14 2017 .UPDATE... 936 PM CDT For Evening Update... Have continued to lower pops/thunder potential this evening and overnight, with weak mid-level lapse rates and weak low level convergence apparently working against favorable large scale forcing and resulting in little shower/thunderstorm development. Weak surface low pressure was analyzed over far northeast IA late this afternoon, with a subtle quasi-warm frontal feature extending southeast into northern/central IL. Despite fairly strong mid- level short wave digging southeast across the Upper Mississippi Valley during peak diurnal heating, and MLCAPE values 500-1000 J/kg (around 700 J/kg per DVN 00Z sounding), little organized convection developed across the region. While broad areas of modestly enhanced cu were noted in GOES-16 vis imagery, low level convergence remained fairly weak, and mid-level lapse rates of 5.5-6 C/km resulted in little development other than a few isolated cells over northeast IA. A few isolated showers were noted over parts of northern IL as boundary layer cooled and instability become a bit elevated above with sunset, but these too have fizzled for the most part over the past hour or so. High-res convection allowing guidance has been significantly overdone in developing convection across northern IL since this afternoon, and successive runs continue to back off on coverage overnight. While current radar depiction would suggest little threat of precip overnight, weak but persistent theta-E advection above subtle warm frontal feature may continue to produce some festering weak convection at times overnight beneath the southern periphery of the aforementioned mid-level wave just to our north. Thus not comfortable going dry, though have limited pops to 30 percent or less and many areas will likely see no rain. Trailing weak surface cold front/trough is progged to sag across central IL Tuesday. Guidance continues to indicate some light qpf in the vicinity of this boundary into the afternoon hours, though mid-level ridging develops and suggests little support beyond a little convergence right near the boundary. Based on this have also lowered or removed pops except for south of a VYS-VPZ line, and lowered pops slightly there. Updated digital forecast/zfp available. Ratzer && .SHORT TERM... 234 PM CDT Through Tuesday... Debris clouds from early morning thunderstorms kept temperatures a bit cooler than expected this morning. However, those clouds are dissipating as they push east, and temperatures are rebounding nicely. Weak low pressure over Iowa will pass over southern Lake Michigan tonight. Scattered storms are expected to form across north-central IL this evening. Guidance has been struggling with convection most of today and many models are already overdoing thunderstorm coverage. Therefore, while I expect scattered storms, I am uncertain about coverage and exactly when thunderstorms will form. The latest RAP guidance suggests the atmosphere is in the process of destabilizing, but surface CIN remains. Therefore, expecting scattered storms to form near the Rockford area between 00-02Z/ 7-9PM CDT. Storms will shift east through the evening. A couple of storms may become strong, but I am not expecting widespread severe weather. CAPE values should be 1000 J/kg or less and 0-6km shear will be around 40 kt. The strongest storms may produce gusty winds. Weak winds and recent rainfall will probably lead to patchy fog in outlying areas tonight. The low`s cold front pushes south early Tuesday morning with winds becoming north to northeast behind it. 12Z guidance has the cold front stalling across central IL, a bit further south than previous runs. As such, thinking the focus for thunderstorms Tuesday will be further south. Kept up to a chance of showers and storms south of I-80, but the main focus may even be further south across WFO ILX`s forecast area. Temperatures Tuesday will be similar to today except for cooler along the lake. JEE && .LONG TERM... 255 PM CDT Tuesday night through Monday... With Tuesday looking drier than previously anticipated, weak ridging should be in place and a diffuse stationary front parked just south of the area by late Tuesday night and early Wednesday. Northeasterly low level flow Tuesday night will transition to south to southeasterly by midday on Wednesday as the stationary front lifts through as a warm front and starts feeding higher dewpoints into the area. The GFS and ECMWF disagree on how quickly to develop showers during the day Wednesday, apparently in part due to differences in the degree of low level convergence in the warm sector, afternoon destabilization, and supporting shortwaves aloft. Using the NAM as a tiebreaker would support the much slower ECMWF solution and keep much of the area dry until evening. For now will plan to carry slight chance to chance POPs for most of Wednesday and go with likelies for the evening and overnight. Somewhat better model agreement supports hanging onto at least chance POPs for most of Thursday as well. A cold frontal passage was previously expected a bit earlier in the period but now looks to be on track for the middle of the day Thursday. Friday looks dry and cooler with northwest winds but residual low level moisture and steep midlevel lapse rates likely will support increasing cloudiness in the afternoon along with the possibility of a few sprinkles. The picture for the weekend is of course far less certain but current trends suggest Saturday could see scattered showers with a passing small amplitude trough aloft, while Sunday presently looks dry under the influence of increasing heights aloft and ridging at the surface. And then there is the question for Monday and the eclipse. A very early look gives hope that the ridge anticipated to be overhead Sunday may still be blocking moisture return and providing large scale subsidence through the first part of Monday. Or perhaps the pattern will slow down a bit and not move the ridge into the area until Sunday night or Monday. It remains too early to have much confidence in any specific solution, but for now we will start with a dry forecast and partly cloudy skies. Lenning && .AVIATION... For the 00Z TAFs... South-southwest winds continue this afternoon, and the winds were strong enough to keep the lake breeze east of ORD and MDW. Scattered thunderstorms have developed over nwrn IL/swrn WI and are still expected to progress ewd across the area through the evening. The high res model guidance is struggling to handle the thunderstorm activity and latest trends have been slower than previously anticipated. So, have backed off TS mention to vcts at the terminals since confidence, especially in timing and coverage is relatively, low. Through the night, high pressure will build across the region and winds will diminish to light and variable. Some mvfr br development is possible at RFD/DPA and generally sheltered , low lying locations. Expect that ORD/MDW should remain vfr, or possibly a brief period of 4-5sm br. A cold front is expected to sink south early Tuesday morning and with winds becoming north to northeast. Low cigs are also possible in the marine-cooled environment behind the front when winds turn off of Lake Michigan. Cloud cover should scatter out with daytime warming and mixing. && .MARINE... 255 PM CDT A weak cold front dropping across the lake tonight will turn winds northeast and then north. The front will stall well south of the lake Tuesday before lifting back north as a warm front on Wednesday with strengthening south and southeast winds behind it Wednesday night and Thursday. A stronger cold front then crosses the lake Thursday and returns winds to a more northwesterly direction. Lenning && .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 Lubbock TX
618 PM CDT Mon Aug 14 2017 .AVIATION... The potential exists again tonight for a thunderstorm complex to roll across the region. Will hold off on introduction of TS at this time, but models are zeroing in on threat at KPVW and KLBB between 06z and 09z and at KCDS after 09z. Otherwise, VFR and light south winds are likely to prevail through Tuesday morning. South winds are expected to pick up some Tuesday afternoon. && .PREV DISCUSSION... /issued 241 PM CDT Mon Aug 14 2017/ DISCUSSION... RAP and satellite analysis showed a longwave trough pushing into the Great Basin region this afternoon. A small shortwave appeared to be developing on the lee-side of this trough in southern CO, which will be a focus for convection later this afternoon and evening. Short term models also show afternoon convection developing over the high terrain of NM and pushing eastward. A CAPE-rich environment will be available, on the order of 1500-2000 J/kg, and plenty of moisture is in place with PWATs around 1.2 inches. The HRRR has done well with the past several events, and tonight, it is developing yet another complex of storms to bring through much of the forecast area. With the abundant moisture, heavy rainfall is a threat, which could lead to damaging downburst winds. For Tuesday, the longwave trough pushes further east with another shortwave affecting the region. Upper level support looks to be favorable for sustained convection with low- and mid-level moisture still plentiful. This should be our last day of widespread storms as high pressure over the SE US begins to retrograde towards the central Southern US. Moisture will not completely disappear, though, so a few afternoon thunderstorms are possible. Afternoon highs will remain fairly steady around seasonal norms. && .LUB WATCHES/WARNINGS/ADVISORIES... None. && $$ 07
Area Forecast Discussion
National Weather Service Nashville TN
913 PM CDT Mon Aug 14 2017 .DISCUSSION... Have made some minor adjustments to overnight POP and weather grids, keeping chance of rain relatively low and trending toward thunder-less precip. Otherwise, little change. && .AVIATION... 00Z TAF DISCUSSION. BNA/MQY/CKV/CSV...Scattered showers continue moving across Middle Tennessee late this afternoon, with the strongest activity remaining south of I-40. HRRR shows mainly light showers lasting well into the evening, so will cover this with VCSH remarks, except TEMPO showers at CSV. Look for ceilings to drop considerably this evening and overnight, with MVFR and possibly IFR conditions developing. This will limit the radiational cooling and should keep fog from becoming particularly dense. Showers are once again possible tomorrow, mainly south of I-40. Will handle these with PROB30 remarks. && .PRELIMINARY POINT TEMPS/POPS... Nashville 72 88 73 91 75 / 40 30 20 30 20 Clarksville 71 86 71 88 74 / 20 20 20 30 20 Crossville 70 81 69 84 72 / 40 30 20 30 20 Columbia 71 87 73 90 74 / 40 30 20 40 20 Lawrenceburg 71 86 72 89 74 / 40 30 20 40 20 Waverly 71 86 73 89 75 / 20 30 20 30 20 && .OHX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION......19 AVIATION........08
Area Forecast Discussion
National Weather Service Blacksburg VA
814 PM EDT Mon Aug 14 2017 .SYNOPSIS... The approach of an upper level disturbance through Tennessee will help draw a stalled frontal boundary back into our region overnight. The interaction of the front and system will allow for increasing coverage of showers, and a few storms, across mainly western sections of the region. On Tuesday, the front will buckle back south with the departure of the upper system, returning the focus for additional showers, and a few storms, to the southeastern sections of the region. && .NEAR TERM /THROUGH TUESDAY/... As of 800 PM EDT Monday... A stationary front extended from Georgia to the eastern North Carolina. An area of low pressure was moving east through Tennessee. This low will help buckle the stationary front back north as a warm front this evening as the low makes progression east toward our region. Have focused the highest probability of precipitation across southern Virginia and northwest North Carolina between 11PM and 8AM based in the timing of the precipitation currently in the Tennessee Valley as depicted by the last few HRRR runs and other high resolution guidance. More fog is expected for tonight due to the light surface winds, dew points in the mid 60s to lower 70s and the expected precipitation. The fog is expected to dissipate by mid- morning Tuesday. During the day Tuesday, the front will have slipped back south a bit, but not too far outside of our region that it won`t act as a focus for for additional showers and storms to develop along it during the heating of the day. Anticipate the southeast sections of the forecast area to have the best coverage of precipitation on Tuesday. Low temperatures tonight will be comparable to those of this morning given limited change in our airmass. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/... As of 312 PM EDT Monday... We`ll finally be able to rid ourselves of cloudy, rainy wedge conditions Tuesday evening. With mid-level heights generally rising and a steady stream of southwesterly warm and moist advection Wednesday night into Thursday, it portends a return to warmer and more humid conditions. As far as rainfall chances go, though a limited chance should exist Wednesday, the better chance for showers and thunderstorms is later Thursday and Friday associated with a upper-level disturbance and related surface low/cold front, each of which passes well to our north. First in a series of weak disturbances in broad mid-level southwest flow advances eastward before midnight Tuesday evening, with clearing expected from northwest to southeast. Lingering periods of showers, with a couple embedded thunderstorms should remain possible through the evening with the best chance in the east and south early. Steady NW -> SE decrease in PoPs after midnight. As clearing begins after midnight, should also see periods of radiation fog in the western river valleys with weak ridge of surface high pressure gradually nosing southeastward. All in all still a rather mild night with lows in the mid to upper 60s, though lower 60s in the Greenbrier Valley and along the southern Blue Ridge into the NC high country. For Wednesday, at least the first part of the day should be on the dry side. Today`s 12z guidance does show a mid-level vorticity max embedded in broader mid-level height rises that rotates from the Cumberland Plateau into western NC. The NAM shows a weaker disturbance and also less of an impact for our area, while the GFS and the ECMWF would warrant at least slight to lower end Chance PoPs Wednesday afternoon and early evening across the southern half of the county warning area for showers and garden-variety storms. Sided toward the global models in showing PoPs in the 20-30% range from a line along and south of Bluefield to Rocky Mount to Appomattox, highest furthest south. With weak wind flow leading to slow storm motion, could see some heavier downpours in spots. Coverage should diminish by mid-evening with forecast trending dry for Wednesday night. In the wake of this disturbance, warm advection commences Wednesday night leading the first of a couple mild and muggy nights. Highs mainly in the 80s with lows in the mid 60s to lower 70s. Today`s model guidance continue to show a frontal system and associated upper-level disturbance passing across the Ohio Valley and into the northern mid-Atlantic Thursday afternoon into Friday. On Thursday, the best co-location of stronger convective instability/deep-layer shear is more in IN/OH, which suggests a more organized scattered severe threat away from the Appalachians and Piedmont. Under modest height falls aloft and model-derived surface winds indicating surface convergence axis/pre-frontal trough along the western Appalachians, surface-based CAPEs of under 1500 J/kg with surface heat should generate scattered thunderstorms during the afternoon primarily in that area, with more isolated coverage elsewhere. Greater potential for more widespread showers and isolated embedded thunderstorms for the evening, this being essentially remnants from Ohio Valley storms. On Friday, a considerable amount of early-day cloudiness casts enough question on convective instability - if not limiting it entirely - ahead of the cold front aloft/850 mb wind shift. With limited deep-layer shear to values under 30 kts, thunderstorms would not likely be strong based on current indications from guidance. Warmest day would be Thursday with highs in the mid 80s to low 90s, and with dewpoints in the 60s to low 70s it leads to heat indices in the upper 90s in the Piedmont away from Smith Mountain Lake. More cloudiness supports highs in the 80s. && .LONG TERM /FRIDAY THROUGH MONDAY/... As of 312 PM EDT Monday... Cold front finally moves across the forecast area Friday night. A considerable amount of variance exists in the 12z GFS and ECMWF solutions for the weekend, particularly on if the front makes a full clear across VA or if it hangs around/stalls and picks up tropical moisture keeping our eastern and southern counties wet. Adding to this uncertainty is the timing of a mid-level disturbance in the northern stream across the Great Lakes region. Therefore, kept at least 15-30% PoPs east of the Blue Ridge for the weekend until less variability in guidance becomes apparent. Stayed close to a blend of guidance for highs and lows which keep temperatures near typical mid- August levels. A potentially warmer period is indicated by the GFS and ECMWF early next week as a broad heat ridge dominates much of the Plains and into the Ohio Valley. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... As of 800 PM EDT Monday... Stratus in the foothills and piedmont of Virginia and North Carolina dissipated late today for a brief break in sub VFR conditions at KLYH and KDAN but a short wave tracking out of the Tennessee Valley will spread numerous showers and scattered thunderstorms across southwest Virginia, northwest North Carolina and southeast West Virginia overnight. MVFR ceilings will fill back in across the region before midnight with IFR to LIFR clouds over the mountains and in any pockets of very heavy rain. Medium confidence that a majority of the precipitation will cross through the region between 03Z/11PM and 12Z/8AM. South to southeast winds will remain light at the surface. Combined with dew points around 70 and all the precipitation high confidence that areas of fog will develop this evening. Visibilities will be in the MVFR range. On Tuesday, medium confidence of slow improvement of ceilings and visibility. Once a weak surface low crosses into eastern Virginia, and surface winds become more west and northwest, conditions will improve, especially east of the Blue Ridge. This may not be until after 18Z/2PM at KROA, KLYH, and KDAN. Extended Aviation Discussion... Widespread fog is again expected on Tuesday night. Wednesday into Thursday the frontal boundary to our south will meander north and south for a bit until such time the departure of T.S. Gert allows the front to be shunted to the southeast. While the front is in our proximity, daily scattered precipitation and rounds of sub-VFR conditions are probable. Late night/early morning mountain and river valley sub-VFR fog will be possible. Friday into Saturday, we look to our northwest for our next approaching upper level system. This one will bring a cold front into and through the area Friday night. Look for an increase in precipitation on Friday with storms possible during the afternoon and evening. Sub-VFR conditions will accompany the heavier showers and storms, and also persist in the form of late night and early morning fog heading into Saturday morning. && .EQUIPMENT... As of 755 PM EDT Saturday Aug 12th... KFCX doppler radar will continue to be down for the rest of the month due to a failing bull gear. It will only be operational during this time frame for brief periods if an imminent significant widespread severe weather and/or hydrologic event occurs. Operating the system for any amount of time until the bull gear is replaced risks a catastrophic failure that would further extend system downtime. From the 17th through the 27th the radar will most likely be down completely as the repairs are expected to be made during this period. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...DS NEAR TERM...DS SHORT TERM...AL LONG TERM...AL AVIATION...AMS/DS EQUIPMENT...RAB/WERT
Area Forecast Discussion
National Weather Service San Angelo TX
630 PM CDT Mon Aug 14 2017 .AVIATION... /00Z TAFS/ Storms near KABI (Abilene) will continue into the early evening hours, and although the strongest part of the storm should stay south of the terminal, some drop in visibility and/or ceiling is still possible. Elsewhere, hit and miss storms will continue across the area, but nothing look like it will be approaching any of the terminals soon. Will leave out of the forecast for now. Otherwise, mainly VFR conditions will prevail with south to southeast winds of around 10 knots continuing. && .PREV DISCUSSION... /issued 254 PM CDT Mon Aug 14 2017/ SHORT TERM... (Tonight and Tuesday) Weak upper level disturbances moving across West Central Texas and old outflow boundaries will set the stage for late afternoon and evening isolated to scattered thunderstorms through Tuesday. Water vapor satellite seems to show a disturbance moving east across Far West Texas at 18Z. HRRR and Texas Tech WRF shows some isolated to scattered precipitation developing across the area this afternoon. Have continued slight to chance Pops mainly west of a line from Junction to Brady this afternoon and again on Tuesday. Any one of these storms can produce strong gusty winds and very heavy rain. Highs on Tuesday should warm into mid and upper 90s, with a few low 90s near Eldorado, Ozona and Sonora. LONG TERM... (Tuesday night through Monday) West Central Texas will be in southwest flow aloft, Tuesday night into Wednesday night, as an upper level trough develops across the western CONUS and an upper level ridge remains across the Southeast United States. Models are indicating an upper level disturbance tracking across West Texas late Tuesday afternoon/evening, resulting in isolated to scattered shower and thunderstorms development. Some of this activity may approach our western counties during the evening hours. Chance PoPs were continued across our western counties, decreasing as you head south and east. Overnight lows will mainly be in the mid 70s. The main concern with these storms will be locally heavy rainfall and strong gusty winds. Isolated showers and thunderstorms are once again possible Wednesday afternoon and evening, although coverage should be less than what is forecast on Tuesday. Above normal temperatures are once again forecast, with highs in the mid to upper 90s. Upper level ridging is forecast to build back into the area by the end of the work week and into the weekend. A few showers and thunderstorms are possible Thursday and Friday, although coverage is forecast remain very isolated. Rain chances will drop to near zero by this weekend, as the upper level ridge strengthens over the area. Temperatures through the period will be above normal, in the mid to upper 90s, with a few locations approaching the century mark. && .PRELIMINARY POINT TEMPS/POPS... Abilene 75 98 77 97 / 20 20 30 20 San Angelo 75 97 75 97 / 20 20 20 20 Junction 74 97 75 96 / 5 0 10 10 Brownwood 74 98 76 97 / 5 5 20 10 Sweetwater 75 95 75 96 / 30 20 40 20 Ozona 74 93 75 95 / 20 20 20 20 && .SJT WATCHES/WARNINGS/ADVISORIES... None. && $$ 07