Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 08/01/18


Area Forecast Discussion
National Weather Service Denver/Boulder CO
722 PM MDT Tue Jul 31 2018 .UPDATE... Issued at 720 PM MDT Tue Jul 31 2018 Clouds moving in from the NNW over the foothills and from Wyoming over the next few hours. This will slowly bring in a FEW to SCT deck for the morning and into the afternoon. Maintained current temp forecast but added some patchy smoke to the forecast for areas of Summit and Grand county with increased smoke produced by the Silvercreek fire. I suspect this smoke to continue into the morning hours and tomorrow if intensity continues. && .SHORT TERM...(This evening through Wednesday) Issued at 332 PM MDT Tue Jul 31 2018 It will be a quiet night tonight with low temperatures reaching a few degrees below average. Some upper level clouds may develop off the higher mountains similar to what is occurring across the western part of the state. Winds are gusting up to 25 mph out of the north on the east side of Denver right now and these winds will begin to settle down around sunset. Otherwise, there are no POPs in the forecast through 12z Wednesday. A small vort max will track southeastward out of Wyoming tomorrow afternoon reaching our CWA by about midday. This feature, along with some weak instability, may be enough to create a few showers and thunderstorms that begin over the mountains and foothills and move southeastward onto the urban corridor and plains. With low relative humidities in the low levels and forecast DCAPE values near 1000 J/kg, these showers and storms will be capable of producing winds up to 35-45mph. However, the HRRR smoke model suggests high values of vertically integrated smoke to move over our CWA by mid morning and this may limit the already low instability in the area. Therefore, there is low confidence in the strength of the thunderstorms and associated wind gusts. With this smoke, skies may be hazy tomorrow as high temperatures will be around average. .LONG TERM...(Wednesday night through Tuesday) Issued at 332 PM MDT Tue Jul 31 2018 As the calendar turns the page to August we will continue with the mid-summer weather pattern that brings warm temperatures and a chance of afternoon and evening thunderstorms to northeastern Colorado. Early on, the center of the upper high will be centered over Arizona and the northwest corner of Mexico with weak northwesterly flow over northern Colorado. Over the last couple days, satellite imagery has shown an increase in convective activity over the mountains of northwest Mexico. The forecast models are showing the results this as elevated specific humidity levels across the desert southwest. This moisture will make its way over Colorado as the weak west-northwest flow continues. On Friday, the flow over northern Colorado becomes more westerly and weakens as the upper high shifts westward toward the Pacific. A weak upper disturbance embedded in the flow is forecast to cross over the state Friday evening. This will drive a round of showers from the mountains out onto the plains. Locally heavy rain will be possible with these showers as model soundings indicate that precipitable water values in the Denver area will be up near 1.00 inches. Medium range models indicate that this will be the day with the most widespread precipitation over the next week. The rest of the forecast period should see showers and thunderstorms confined mainly to the mountains. Each evening may see a few thunderstorms come out over the adjacent plains. The ECMWF shows the next upper level ridge will develop over Colorado and New Mexico by Monday morning and then remaining over the southern plains through the week. If the center of the upper circulation moves more eastward, this will increase the chances for moist southwest flow to begin transporting monsoonal moisture into the state. This would lead to an eventual increase in shower activity and intensity. For the time being will stick with the afternoon shower activity over the mountains through the middle of the week with plains locations being warmer and a little drier. Highs on the plains should make it into the lower 90s by Friday and then remain at that level through Wednesday. && .AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon) Issued at 332 PM MDT Tue Jul 31 2018 VFR conditions will continue through tomorrow evening. Winds have increased this afternoon out of the north at DEN and APA and will sustain these speeds or slightly less until roughly around sunset. Overnight, winds will tend toward drainage. A shortwave moving through northern Colorado tomorrow may provide enough forcing to create showers and storms that move off the mountains. Some of these showers and storms could produce gusty and variable winds up to 40 knots with the next chance between 20-00Z. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...Bowen SHORT TERM...Danielson LONG TERM...Dankers AVIATION...Danielson
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
659 PM EDT Tue Jul 31 2018 .AVIATION... Bands of showers and an occasional thundestorms can be expected into the overnight with a steady expansion of coverage in the 02z-04z time frame as low pressure lifts north-northeast into the area. Best coverage of rain will focus from KPTK SSE with best low level FGEN. Further NNW, there will be a sharp decline in coverage/intensity of activity from KFNT to KMBS. VFR to spotty MVFR cigs will drop to MVFR/IFR late tonight as this low skirts the area with a return to lower VFR on Wednesday as drier westerly flow develops in the wake of this system. For DTW...spotty showers early in the forecast will increase in coverage/intensity after 02z as low pressure lifts into the area. A few thunderstorms should also be embedded with this activity. Cigs will trend from lower VFR to MVFR with this convection and perhaps drop to IFR for a time late tonight/early Wednesday before lifting midday Wednesday. .DTW THRESHOLD PROBABILITIES... * High for cigs aob 5kft into Wednesday morning, lower by midday. * Moderate for occasional tstorms in KDTW airspace late this evening into tonight && .PREV DISCUSSION... Issued at 548 PM EDT Tue Jul 31 2018 UPDATE... FLASH FLOOD WATCH NOW IN EFFECT FOR DETROIT METRO AND OUTLYING AREAS THROUGH TONIGHT... As of 545 PM EDT...Have continued to monitor the latest trends in model guidance with respect to the heavy rainfall potential this evening and into tonight across portions of southeast Michigan. The latest runs of the HRRR and 18z NAM3km have only added further confidence to the heavy rainfall solution already proposed by 12z runs of the SPC 4km WRF and Hi-res ARW. As a result, have issued a short-fused Flash Flood Watch for Wayne, Oakland, Macomb, St. Clair, Washtenaw, Monroe, and Lenawee counties through 4am tonight. Bands of heavy rainfall with embedded thunderstorms, associated with a compact area of low pressure tracking northeast into southwestern Ontario later tonight, are expected to primarily impact these areas, with a particular concern for the greater Detroit metro area. Timing of heaviest rainfall looks to occur between roughly 8pm and midnight. Rainfall rates during this time will be heavy to intense at times where banding persists for the longest, with rainfall totals of 1-3 inches possible in as little as less than 3 hours, with the potential for localized amounts of 3-5 inches. These rainfall rates and totals will pose a heightened risk for flash flooding in the Detroit metro and outlying urban areas, as well as susceptible low lying and poor drainage areas in the watch area. Additionally, rapid river rises will also be possible and may further exacerbate the flooding threat. Previous discussion highlights the meteorological setup in greater detail and is below. PREV DISCUSSION... Issued at 400 PM EDT Tue Jul 31 2018 DISCUSSION... Focus for this forecast will be the heavy rainfall potential across portions of southeast Michigan this evening and into tonight. Upper low over eastern MO and western IL will drive a surface low pressure northward from the Ohio River Valley this afternoon and through portions of southeast Michigan. Trends have been towards a more amplified wave with increasing precipitation moving from south to north as a shortwave rotates around the low. The center of the surface low looks to track up through the Detroit and St Clair Rivers. This will place southeast Michigan in an area of deformation and a favorable location for likely precipitation. Precipitable Water values will be reach around 1.75 inches, which is in the upper 10 percent of climatology and will provide some confidence for heavy rainfall potential. Deformation forcing and the presence of some instability will allow for pockets of higher rain rates with embedded thunder as system lifts northward. Afternoon precipitation will make way for heavier precipitation potential by the evening as stronger forcing arrives. Timing for the heaviest rainfall potential will begin around 7-8 pm for Detroit Metro and areas along the I- 94/I-96 corridors then slowly work its way northward towards the Thumb by midnight. There will be lingering precipitation chances with heavy rainfall potential overnight as system lifts north. The general higher rainfall amounts will reside roughly along and southeast of an Howell to Bad Axe line, but latest hi-res guidance is leaning towards Wayne, Oakland, Macomb and St. Clair Counties seeing some of the higher rainfall amounts where the greatest deformation forcing may line up. Main concern is for urban flooding if heavier precipitation bands set up over any of urban areas, as 1 inch per hour rainfall rate or greater will be possible. The upper level trough will begin to weaken throughout tomorrow with the trough axis remaining west of the area and good moisture remaining in place. This will keep low chances for showers and thunderstorms in the forecast as the initial wave shears within the troughing pattern over Michigan. Lack of shear will keep activity unorganized and coverage should be scattered. Temperatures tomorrow in the upper 70s and low 80s with a brief break in precipitation chances tomorrow night. Troughing pattern persisting over the region will again bring some precipitation changes for Thursday, but this will reside mostly over central Michigan where the better forcing will be. At the moment, areas affected by rain chances will be towards the northern CWA across the Tri-Cities. An slight increase in instability and lapse rates will keep potential for thunderstorms in the forecast. Temperatures will increase slightly with most areas reaching into the low to mid 80s. Upper-level troughing will continue to remain in place across the Great Lakes heading into Friday. Dewpoints remaining in the 60s will promote the potential for diurnally-driven isolated to widely scattered showers and thunderstorms. Increased downstream ridging over the Mid-Atlantic region will lead to drier and more capped conditions for much of the weekend as 700 hPa temps increase into the 8-10 C range. Weather will then become increasingly unsettled early next week as potent northern stream energy ejects out of the northern Plains towards the Great Lakes with scattered to potentially numerous showers and thunderstorms. Hot and humid conditions will persist through much of the long term period with temperatures near to slightly above average and surface dewpoints well into the 60s to near 70. MARINE... Light to moderate wind through the week with no significant events on the horizon. Low chance for thunderstorms will exist in the nearshore zones through the end of the week. HYDROLOGY... Bands of heavy rainfall with embedded thunderstorms are likely this evening and into tonight. Confidence has increased that the greatest threat for heavy rainfall will occur across the Detroit metro and outlying areas. A Flash Flood Watch has been issued for Wayne, Oakland, Washtenaw, Macomb, St. Clair, Lenawee, and Monroe counties through 4am tonight. The potential exists for rainfall totals of 1-3 inches in the watch area, with localized areas of 3-5 inches possible where banding persists the longest. Much of this rain may fall in less than a 3 hour period. These rainfall rates and totals will pose a heightened risk for flash flooding in the Detroit metro and outlying urban areas, as well as susceptible low lying and poor drainage areas in the watch area. Additionally, rapid river rises will also be possible and may further exacerbate the flooding threat. The heavy rain threat will be highest between 8pm this evening through midnight tonight. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...Flash Flood Watch until 4 AM EDT Wednesday for MIZ063-069-070-075- 076-082-083. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....DG UPDATE.......IRL DISCUSSION...AA/IRL/OV MARINE.......JVC HYDROLOGY....JVC/IRL You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.
Area Forecast Discussion
National Weather Service Grand Forks ND
705 PM CDT Tue Jul 31 2018 .UPDATE... Issued at 700 PM CDT Tue Jul 31 2018 Cold front located from NW of Bemidji to near Mahnomen to just NW of Fargo to Lisbon. Just enough shear aloft and upper level energy for storms to form the last 2 hours in Beltrami county on the SW edge of a line of storms that extended into Ontario. In the past 15 min have noticed CU field is growing via vsbl satellite pic along the front to north of Fargo and we are starting to see t-storms get going. SPC analysis shows surface CIN increasing already in SE ND with little CIN yet in MN fcst area. The one storm NW of Bemidji became supercellular with large hail but as line of broken storms form it is not clear how strong the new storms will get as the environment become unfavorable for intensification soon. Scattered light rain showers Grafton/Grand Forks area moving slowly east. Updated pops to reflect current conditions and fcst idea of a risk of a few storms thru the night along the front into WC MN, but not severe. && .SHORT TERM...(This evening through Wednesday) Issued at 253 PM CDT Tue Jul 31 2018 Convection chances and strength tonight will be the main issue for the period. Northwesterly flow aloft with a digging shortwave trough has helped push a cold front into our northern counties. As of 19Z, the front had passed through DVL and GAF over to BDE. So far the CAPE along the front has been very limited, and only a few rain showers have been moving into northwestern MN. SPC meso analysis has the northern counties near the front well capped. However, ML CAPE values are in the 1000-1500 J/kg across parts of southeastern ND. Several of the high res runs such as the HRRR and a couple of HopWRF members have storms blossoming along the front between 22 and 00Z as the front pushes south into the area of high instability. The instability area is pretty narrow, and deep layer bulk shear is rather marginal with 25 to 30 kts. However, shear is more than we have seen lately, and some high based thunderstorms with the potential for large hail and damaging winds are not out of the question for a few hours this evening. The main band of thunderstorms will push southeastward by 03Z, although several of the CAMs have additional activity developing behind the surface cold front. Will continue to keep some POPs going for much of the night into tomorrow morning. High pressure will be building in behind the cold front tomorrow, with north winds bringing continued cold air advection for much of the day. Temps should stay mainly in the low 70s, although some upper 60s will be possible in the southeast with clouds hanging around a bit longer. .LONG TERM...(Wednesday night through Tuesday) Issued at 253 PM CDT Tue Jul 31 2018 Northwest flow aloft prevails Wednesday night in the wake of a shortwave trough. Surface flow shifts as we head into Thursday morning, becoming southerly and allowing moisture to advect into the region. The surface to 850mb flow continues to increase through the day on Thursday with enhanced long-fetch moisture flow into the region. A shortwave ridge will be building into the area at the same time, thus allowing temperatures to climb into the mid to upper 80s on Thursday and into the upper 80s to lower 90s on Friday with increasing humidity. A relatively weak cold front will push across the CWA on Friday with a reinforcing cold front Saturday evening. Given the increased moisture in place, instability will be elevated ahead of the front, with CAPE in the 3000 to 4500 J/Kg range. This, combined with bulk shear of 30 to 50 knots, will be favorable for severe thunderstorm development Friday afternoon with potentially strong thunderstorms on Saturday. For Sunday and Monday, several weak shortwaves will move through the area along northwest flow aloft. This will allow several opportunities for scattered showers and thunderstorms each afternoon and evening. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 700 PM CDT Tue Jul 31 2018 MVFR stratocu deck in S Manitoba extends into far NE ND at 23z/00z. Unsure how far south it makes it though as the main 500 mb cold pool is moving more east-southeast and models indicate 850 mb moisture weakens as it drops south. Better chc of MVFR cigs in to NW MN tonight into Wed AM. && .FGF WATCHES/WARNINGS/ADVISORIES... ND...None. MN...None. && $$ UPDATE...Riddle SHORT TERM...JR LONG TERM...Lynch AVIATION...Riddle
Area Forecast Discussion
National Weather Service Grand Junction CO
240 PM MDT Tue Jul 31 2018 .SHORT TERM...(Tonight through Wednesday night) Issued at 240 PM MDT Tue Jul 31 2018 With high pressure sitting to the west, the western slope is sitting on the eastern periphery of the high with a drier north to northwest flow overhead. There is no shower or thunderstorm development yet this afternoon with a few cumulus clouds forming over the southern ridges. Do not anticipate much in the way of precipitation due to the more stable atmosphere present today, helping to suppress the cumulus growth. A bit more cloud cover is anticipated tonight with an increase in high level moisture, so not expecting temperatures to be quite as cool as they were this morning. The morning started off a bit smokey as smoke from the wildfires in California is making its way around the high pressure and down into our CWA for widespread hazy and smokey skies. The several wildfires burning across our state are allowing for localized heavier smoke nearby, as seen on radar and satellite this afternoon. The HRRR smoke model shows this trend continuing through at least Wednesday night/Thursday morning, so kept smoke in the forecast through that period. Wednesday will be a transitional day as the high pressure begins slowly shifting eastward, allowing for a little more moisture to infiltrate from the west. Precipitable water (PW) values rise towards 0.75 inches across eastern Utah and extreme western Colorado, which will result in isolated to scattered thunderstorms over the higher terrain Wednesday afternoon. Storms are expected to be high based with gusty outflow winds and lightning the main concerns. A weak shortwave looks to rotate around the periphery of this high, which does remain to the west, but it seems that this shortwave will impact locations more downstream over the Front Range as it interacts with better moisture. Overall though, anticipating a mostly dry, smokey and hot day. Afternoon temperatures overall have been trending warmer than guidance in this type of regime, so inched those numbers a bit above statistical guidance. .LONG TERM...(Thursday through Tuesday) Issued at 240 PM MDT Tue Jul 31 2018 The high pressure ridge will begin a more eastward shift on Thursday as a trough pushes into the Pacific Northwest, allowing the flow to lay over to the west. This will also advect in better moisture as PW rises above 0.75 towards an inch near the Four Corners and eastern Utah. Anticipating a dry start to Thursday as the better moisture and associated stronger shortwave do not arrive until Thursday evening. This will carryover into Friday, which is looking like the better day in terms of thunderstorm chances and coverage, as well as better moisture, with PW values above an inch across portions of eastern Utah and western Colorado. The regime will transition on Thursday from drier, high based thunderstorms towards better chance of heavy rainers heading into Friday. The valleys even look to be impacted late Thursday into Friday as this better moisture push is supported by a more robust shortwave and better upper level support. Due to the heavy rain potential increasing for Friday, future shifts will have to look at potential for localized flash flooding on any recent burn scars. This is still a few days out so models can change, but something to keep in mind. Temperatures will be hot on Thursday and a bit cooler Friday due to increased clouds and showers. Still trended above guidance as periods of sun still expected to heat things up despite the increase, but it will not feel as noticeably hot. Confidence decreases this weekend into early next week as the models become out of phase with each other. Expecting enough residual moisture to hang around this weekend for afternoon storms focused over the higher terrain and drifting into some valleys late in the day with the high shifting a bit eastward but still having its influence over our region. An embedded shortwave looks to move through the flow late Sunday, for another potential uptick in storm activity through the evening. By early next week, the GFS is now indicating the high pressure building back to the west over the Great Basin, bringing much drier air into the region from the north-northwest which is quite the polar opposite from the model runs 24 hours ago. The EC, however, is still holding onto the ridge placement east of the divide with a decent continued push of moisture from the southwest. The trend so far this summer has been to shift the high back west after a decent moisture push so trending towards the drier forecast for next week, until models come into better agreement. Temperatures are also anticipated to make a rebound late this weekend into next week due to the drier trend. && .AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon) Issued at 109 PM MDT Tue Jul 31 2018 Drier air on northerly flow will bring VFR conditions to the region over the next 24 hours. Visibility may be impacted by smoke that settles into the valleys with possible MVFR conditions in isolated places. Will continue to monitor this impact. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && $$ SHORT TERM...MDA LONG TERM...MDA AVIATION...TGJT
Area Forecast Discussion
National Weather Service Wilmington NC
908 PM EDT Tue Jul 31 2018 .SYNOPSIS... Deep tropical moisture will shift inland through mid-week as ridge builds westward from the Atlantic. This will push most active weather farther inland with a return to more localized shower and thunderstorms, especially along the coast. The trend toward more localized thunderstorm activity will continue into early next week as high pressure takes residence over the Carolinas. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... As of 910 PM Tuesday...well the big change is GOES-East water vapor channels is showing the atlantic ridge building westward. This is seen from the dry air moving in on all three layers of the water vapor. The precipitable at MHX fell from 2.3" to 1.96" in the past 12 hours. The 18 UTC run of the GFS is showing the relatively drier air shifting over the area but is a tad to slow shifting the dry air into the area. The lower levels are still very moist and the southerly flow continues over the forecast area. The HRRR 00 UTC continue to show shower developing overnight along the coast especially after midnight. With the drier air expecting the rainfall intensity to be less tonight and early in the morning than the last few days. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... As of 300 PM Tuesday...A subtle change in the pattern is forecast this period as ridge of high pressure sitting offshore will ridge more significantly to the west. This will bring a drop in PWAT as well as a reduction in convective potential, finally. That being said, the period is not forecast to be dry, but the best rain chances and heaviest QPF should shift westward into the central and western Carolinas. Continued warm and humid air on deep southerly flow will maintain instability and a good chance for tstms, but in a more typical summertime diurnal fashion, although i-95 counties will likely see widespread convection lingering into the night thanks to deeper moisture there. PWATs will feature a reverse gradient from many of the past several days, with lower values, around 1.7 inches near the coast, rising to 2.1 inches inland. This supports still the potential for heavy rainfall and some training of tstms, especially across the Pee Dee on Thursday, with nocturnal decrease in coverage and intensity expected both nights. Highs will climb into the mid/upper 80s on Thursday, warmest in the middle part of the CWA which will be both away from ocean influence and experience less cloud cover than further west. Mins will drop into the low and mid 70s both nights as the muggy southerly flow persists. && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 300 PM Tuesday...This period should finally see a return of more seasonal weather as a building ridge aloft limits shower and thunderstorm activity to a scattered nature more typical of summer by Saturday through Tuesday. On Friday, an upper low passing by to the east will enhance shower and thunderstorm chances. Overall, temperatures will be near normal through the period with maximums in the upper 80s to lower 90s and lows in the low to mid 70s. && .AVIATION /01Z WEDNESDAY THROUGH SUNDAY/... As of 00Z...it seems like a week but for now the area and all TAF sites are free of showers and thunderstorms. The mid-level water vapor imagery shows dry air has moved over the area has curtail the convection for this evening. The HRRR is showing convection forming again along the coast around 04 UTC so will bring in the mention of VCSH to the coastal TAFs of KILM, KMYR, and KCRE. VFR conditions are expected overnight with a hint of MVFR visibility restrictions from fog. Introduced PROB30 for inland sites mainly after 16 UTC for thunderstorms as the deeper moisture will be available. Extended Outlook...MVFR/IFR from scattered to numerous SHRA/TSRA each afternoon and evening across all sites through Friday. Lesser chances for showers and storms over the weekend. && .MARINE... NEAR TERM /THROUGH WEDNESDAY/... As of 910 PM Tuesday...southerly winds of 15 knots continue to blow around the western periphery of the Atlantic high pressure. The seas currently are 4.6 feet at Frying Pan Shoals light tower. The seas should be slowly weakening through the night and the exercise caution maybe dropped overnight. SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/... As of 300 PM Tuesday...High pressure offshore will gradually ridge westward into the coastal waters, slowly causing the gradient to ease. Southerly winds will persist through the period, with speeds of 15-20 kts early, falling to 10-15 kts Thursday night. Wave heights may fall a bit through Thursday night as the winds ease causing the wind-wave component to relax, but this wind wave combined with a persistent 8 sec 2-3 ft SE swell will keep significant seas at 3-4 ft. LONG TERM /FRIDAY THROUGH SUNDAY/... As of 300 PM Tuesday...S winds of 10 to 15 KT Fri will diminish to about 10 KT for Saturday and Sunday as they become more southwesterly. Seas of 3 to 4 FT Friday will subside to 2 FT by Sunday. Chances for showers and storms with locally higher winds and seas remain through the period. However, rain chances over the water should be higher overnight than during the day as is more typical of summer than conditions have been of late. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...Beach Hazards Statement from 6 AM EDT Wednesday through Wednesday evening for SCZ054-056. NC...Beach Hazards Statement from 6 AM EDT Wednesday through Wednesday evening for NCZ106-108. MARINE...None. && $$ NEAR TERM...RH SHORT TERM...JDW LONG TERM...RAN AVIATION...RH
Area Forecast Discussion
National Weather Service North Platte NE
639 PM CDT Tue Jul 31 2018 .SHORT TERM...(This evening through Wednesday) Issued at 322 PM CDT Tue Jul 31 2018 The RAP indicates dry air will remain across western and north central Nebraska tonight with very little return moisture and high pressure across KS. This should support another night of radiational cooling. Southwest winds will probably limit the potential for moisture pooling and fog formation in the valleys. The guidance blend plus bias correction suggests lows in the 50s. A back door cold front will drop through ncntl Nebraska Wednesday. The model consensus suggests isolated afternoon showers and thunderstorms across the Sandhills. Only the NAM12 and NAMnest develop appreciable convection; the HREF is dry and the NMM is very sparse developing just two showers. There is also a disturbance across the Bitterroots in Idaho this afternoon that will be dropping through the Panhandle and swrn Nebraska. The NAM12 suggests and isolated chance but this disturbance might track too far west to affect the Panhandle so just an isolated chance is in place for the Sandhills Wednesday afternoon. .LONG TERM...(Wednesday night through Tuesday) Issued at 322 PM CDT Tue Jul 31 2018 Warm air will continue build into western and north central Nebraska this week and remain in place over the weekend and beyond. This is in response to a long wave trof developing off the West Coast which will drive hot desert air into the Great Plains. Temperatures aloft will return to seasonable levels across Nebraska with -5C to -7C at 500mb and 12C-14C at 700mb. The latest model consensus continues to suggest highs in the upper 80s to mid 90s with dew points in the 50s and 60s. Chance thunderstorm POPs are in place Friday afternoon through Sunday night, mainly in the evening and at night. Dry weather is expected Monday and Tuesday. Precipitable water peaks Friday night between 1.5 and 1.75 inches with the passage of a weak short wave trof. Rain chances Saturday night appear to be directed more across the Dakotas and MN where the better forcing will be located. Sunday night is more interesting with the ECM and Canadian model favoring SD for storm development and the GFS and GEF models favoring northern Nebraska. This will be the one to watch as winds aloft at h500mb increase to 40-50kt supporting strong to perhaps severe storm development. Ordinary storm development would be more likely Friday and Saturday night with weak winds aloft. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 637 PM CDT Tue Jul 31 2018 VFR conditions will prevail through Wednesday evening. Winds will remain fairly light and variable through tonight. A frontal boundary will move across north central Nebraska switching the winds to the north northeast near 10 knots for Wednesday. && .LBF WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...CDC LONG TERM...CDC AVIATION...Gomez
Area Forecast Discussion
National Weather Service Louisville KY
802 PM EDT Tue Jul 31 2018 ...Updated Aviation Discussion... .Forecast Update... Issued at 640 PM EDT Tue Jul 31 2018 Latest HRRR and data from the 12Z HREF continue to argue for a sharp increase in rain chances east of the I-65 corridor later this evening. By daybreak, the 12Z ARW and 18Z NAM were showing a secondary band right along I-65 forming. Will have to watch for training of cells in this area, where local peak rainfall totals of 2-3 inches are not out of the question, similar to this morning. One- (Six-) hour flash flood guidance is still above 2 (3) inches in the Lake Cumberland area, so they should be able to handle it, assuming it comes spread out. Have blended the forecast toward the latest guidance and will send out new products with only minor tweaks shortly. && .Short Term...(This evening through Wednesday) Issued at 342 pM EDT Tue Jul 31 2018 Lower level dry slot and entrainment limiting new convection going for the rest of this afternoon and into this evening. However, the 12z ECMWF/CMC (Canadian)/NAM guidance suggest that the lower rain chances will be short-lived overnight, as the trough axis/low sharpens from Lake Michigan down through the Lower Mississippi Valley. This will advect in deeper layer moisture and channeled vorticity over the southeast half of the WFO LMK forecast area (generally east of Bowling Green to Shelbyville line) after midnight. With the anticipated sharper gradient of lift, enhanced PoPs to likely category centered from Cynthia to Campbellsville and Glasgow overnight. With the upper trough expected to move little eastward during the day on Wednesday, kept chance or better PoPs over the eastern third of the WFO LMK forecast area. Made little change to temperatures into Wednesday, except for raising temperatures slightly in the western third of the forecast area where lower rain chances are anticipated. .Long Term...(Wednesday night through Tuesday) Issued at 342 pM EDT Mon Jul 30 2018 There will continue to be general ridge (southwest U.S.), trough (central U.S. / Mississippi Valley), ridge (eastern U.S. seaboard) blocking pattern in place through at least Saturday with mainly diurnal chances for showers and thunderstorms from Thursday through Saturday. The best chances for rain will be centered east of a Louisville to Bowling Green line onward to the remainder of central Kentucky. At this time, the ECMWF/Canadian/NAM are somewhat consistent with the persistence of this blocking pattern, so have moderate forecast confidence with the PoP/Weather. Beyond Saturday, forecast confidence is lower, as the blocking pattern shifts to a split flow with ridging expanding across the southern U.S. and the WFO LMK forecast area moving toward a diffluent pattern ahead of a faster zonal flow in the upper Midwest. Kept close to the regionally initialized model blend for general weather conditions. Temperatures outside rain areas should return closer to normals for this time of year early next week, especially in the western half of central Kentucky and southern Indiana. && .Aviation...(00Z TAF Issuance) Issued at 800 PM EDT Tue Jul 31 2018 Low level clouds have scattered out this evening with radar mostly quiet this hour. Plenty of high cloud cover will continue to stream overhead, but a bit more clearing was noted over southwest Indiana. Fog may become an issue overnight at HNB, especially after 08z. Went with 3SM for now, but some potential for IFR fog as well. Expect more BKN/OVC cloud cover for the other three TAF sites. After 03z, a round of showers and thunderstorms is expected to lift NNE out of Tennessee, roughly on a Glasgow to Lexington axis. Prevailing showers are likely at LEX early Wednesday, with BWG likely seeing some of this activity as well. Lower MVFR stratus will also be more common further east during the first half of Wednesday. SDF should stay just west of the steady rains. A line of scattered thunderstorms should develop between 18-00z tomorrow, again with BWG and LEX the most likely sites to be impacted. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Update...RJS Short Term...WFO PAH Long Term...WFO PAH Aviation...EBW
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
719 PM CDT Tue Jul 31 2018 .SHORT TERM...(This evening through Wednesday) Issued at 338 PM CDT Tue Jul 31 2018 The main concern in the short term period is the frontal boundary expected to move through the region from Northwest to southeast and associated showers and thunderstorms. As of this afternoon, the aforementioned frontal boundary was draped across southern Canada and an amplifying upper level trough from near Hudson Bay to the southwest. South of the front, high pressure has taken hold over the high plains, with our region on the northern extent. The weak cold front will push south through much of central MN late tonight, primarily from 07-10Z for places like Alexandria and St. Cloud. Scattered thunderstorms along the front are expected, but severe weather is not expected and the storms should generally be decaying as they progress southeastward. By the time they reach the Twin Cities metro, it`s very possible they`ll just be scattered showers with no thunder remaining in the 11-14Z time frame. There is a marginal risk of severe weather for tomorrow afternoon for along and east of the front, which by the afternoon will be from northwest WI to the southwest, the Mankato area and toward northwestern Iowa. A scattered thunderstorms are likely east of the front, with a few of the storms strong. Instability will be marginal, but shear will be rather limited hence the threat for severe weather is low. .LONG TERM...(Wednesday night through Tuesday) Issued at 338 PM CDT Tue Jul 31 2018 The cold front will be south of the area by Wednesday night with clearing skies and drier air behind the front leading to a relatively chilly morning, with some 40s expected in spots across central MN and west-central WI. One last cool & pleasant day with highs in the 70s is expected Thursday, before a pattern change comes Friday. Flow aloft becomes more zonal on Friday as the upper trough flattens out and the persistent southwest ridge begins to build back to the east. Our flow becomes southerly at the surface behind a warm front with dewpoints surging back into the mid-upper 60s and temperatures in the mid-upper 80s. Multiple vorticity lobes passing over the area will create rain chances beginning overnight Friday, and continuing into next week. When we see our best shot will depend on the timing and location of the frontal boundary extending south over the area from a surface low over central Manitoba. With the juicy dewpoints at the surface SBCAPE will have no problem approaching 3000 J/kg and the stronger flow aloft will allow for deep layer shear of 30-40 kts. Storm coverage will likely be limited to near the front as there isn`t much else in terms of surface forcing so will have to watch the threat for severe weather this weekend if the front sets up over our area during the afternoon/evening. Beyond the weekend, models really begin to diverge in handling the upper air pattern so there is little confidence in the forecast. Precip chances look to linger into Monday as the front remains in the vicinity of the area, with a cooler/wetter pattern next week favored by the 12Z GFS & a warmer/drier under continued ridging from the 12Z Euro. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 719 PM CDT Tue Jul 31 2018 Uncertainty remains with coverage of storms we will see as cold front pushes through Wednesday. Timing of the front remains similar to 18z TAF, but HRRR and other models are all over the place on how much activity we`ll see, though that trend is a downward trend, so pulled back any precip mentions to VC. Frontal position in afternoon looks to be far enough southeast where EAU is the only airport with a good chance at seeing afternoon storms. Behind the front, forecast soundings, LAV guidance, and HRRR cig forecast all show a band of MVFR, possibly IFR up toward AXN/STC moving through. KMSP...Shower chance still looks best between 11z and 15z as the front is working through, though those chances look rather meager. Front looks far enough southeast in the afternoon to where afternoon storm development will be well southeast of MSP. For post frontal MVFR, HRRR is starting to really thin out it`s MVFR field at the end of the run, so wouldn`t be surprised if residence time in MVFR cigs is even shorter than the 4 hours we currently have. /OUTLOOK FOR KMSP/ Thu...VFR. Wind E bcmg S 5 kt. Fri...VFR. Wind S 10-15 kt. Sat...VFR. Chc -TSRA. Wind SW 10-15 Gusts 20-25 kt. && .MPX WATCHES/WARNINGS/ADVISORIES... WI...None. MN...None. && $$ SHORT TERM...SPD LONG TERM...ETA AVIATION...MPG
Area Forecast Discussion
National Weather Service Morristown TN
1049 PM EDT Tue Jul 31 2018 .DISCUSSION... A very late evening update here, mainly to account for trends in precipitation over the last hour or two. Guidance has struggled greatly to latch on to how the evening would play out, but it seems a bit of a consensus has been reached. Trended the rest of the overnight hours heavily in the direction of the most recent RAP runs, which will favor some continued high chance or likely PoPs along the western CWA boundary over the plateau region. The RAP seems to be handling the trends well over the last few hours, so there`s increased confidence there. Lowered, but did not get rid of, pops over the central and northern valley, southwest Virginia, and the eastern Tennessee mountain areas. Otherwise, no significant changes were made to the forecast. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 71 80 71 80 / 80 80 70 60 Knoxville McGhee Tyson Airport, TN 69 77 69 78 / 50 90 70 80 Oak Ridge, TN 69 78 69 79 / 60 80 60 60 Tri Cities Airport, TN 67 77 67 79 / 70 90 70 80 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...Flash Flood Watch from 8 AM EDT Wednesday through Thursday evening for Cherokee-Clay. TN...Flash Flood Watch from 8 AM EDT Wednesday through Thursday evening for Blount Smoky Mountains-Cocke Smoky Mountains- East Polk-Sevier Smoky Mountains-Southeast Carter-Southeast Greene-Southeast Monroe-Unicoi. VA...None. && $$ CD
Area Forecast Discussion
National Weather Service Mount Holly NJ
1146 PM EDT Tue Jul 31 2018 .SYNOPSIS... A warm front will lift north across the region overnight and Wednesday morning. High pressure will stay anchored off the East Coast while a surface trough remains entrenched over the eastern seaboard through the early part of the weekend. The high begins to break down over the weekend and the surface trough finally moves offshore late Saturday. Another surface trough may develop across the region Sunday through early next week. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... As of late evening, an area of showers is moving across parts of Delmarva and southern New Jersey. This has been weakening however with a northern extent as it outruns the instability. The greatest instability remains south of the warm front. Some lightning strikes are occurring at times just to our south, and this could get into Delmarva at times overnight. Hi-res models such as the HRRR and NAM-nest are not representing this very well, so don`t know whether to believe their trend to diminish the precip coverage. The short term PoP grids were adjusted to fit the radar-observed precip. Otherwise not much change to the going forecast. Otherwise, clouds are expected to remain overhead for tonight. As the warm front approaches from the south with a mid level impulse passing overhead from the southwest should result in an increasing chance of showers and isolated thunder overnight. Low temperatures are forecast to favor the upper 60s in the Poconos and in far northern New Jersey. They should be mainly in the lower 70s in the Lehigh Valley, southeastern Pennsylvania, much of New Jersey, Delaware and northeastern Maryland. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/... We expect showers and isolated thunder, associated with the warm front in our region, during the morning hours. The boundary should lift through eastern Pennsylvania, and central and northern New Jersey on Wednesday. Once the front moves to the north, and our region will get into the warm sector. The focus of the shower and thunderstorm activity is expected to shift to areas mainly along and to the northwest of the Interstate 95 corridor. Precipitable water values will rise in excess of 2 inches. As a result, there will be an increasing threat of locally heavy downpours as we get into the afternoon hours. Also, mixed layer CAPE values are expected to build into the 1000 to 2000 J/kg range with a fair amount of shear present. Most of our region is under the Storm Prediction Center`s marginal risk designation for severe weather. Parts of eastern Pennsylvania and northern New Jersey are one category higher and under the slight risk designation. The wind should become south to southwest in the wake of the warm front. Wind speeds will likely increase around 10 MPH with gusts near 20 MPH, especially on the coastal plain. Maximum temperatures are anticipated to be mainly in the 80s. && .LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/... An unsettled forecast is still expected for much of the long term period, although it will not rain the entire time. A southwest flow will strengthen across the area as high pressure begins to build westward into the area from the Atlantic at the beginning of the long term period. This high is expected to remain offshore through Friday. Meanwhile, a cold front is expected to dissipate Wednesday night as it approaches and a surface trough develops across the eastern seaboard. With the high offshore, this surface trough will remain stationary through the end of the week. A ridge aloft will remain offshore of the east coast while a trough remains in place to our west as well. This will all keep a steady southwest flow across the area, which will allow moisture to continue to pump into the region through the week. This is evident from PW values increasing to 1.75- 2.00 inches across the area and remain in place through the end of the week. So there will be a chance of showers and thunderstorms each day from Wednesday night through Friday. Much of the activity will likely be diurnally driven and focused during times of short wave/vorticity impulse passages. Latest guidance has been trending the precipitation generally to the west, so will continue to monitor future runs for consistency. By Saturday, the high pressure at the surface begins to break down as the ridge aloft begins to shift westward across the deep south. This will allow for the surface trough to move across the area later Saturday, while the flow aloft becomes more westward or nearly zonal. There will remain a enhanced chance of showers and thunderstorms on Saturday with the passage of the surface trough and any short wave/vorticity impulse passages. There is some discrepancy between the GFS and ECMWF as to the amplitude of the short wave/surface trough and associated precipitation. By Sunday, another surface trough may develop across the east coast and remain in place through at least Tuesday as another short wave moves around the ridge to our south. The flow aloft remains more westerly, or shifts more northwesterly by Tuesday, while PW values lower to 1.5-1.75 inches. The shower/thunderstorm chances decrease for Sunday into Monday, but do not drop off completely as there could be some weak short waves/vorticity impulses move across the area. However, the GFS suggests a stronger short wave could move across the area on Tuesday, which could lead to an enhanced chance of showers and thunderstorms. The ECMWF does comply as it suggests continued zonal flow across the north-central U.S. Overall, temperatures are expected to remain near to slightly above normal through the weekend. && .AVIATION /04Z WEDNESDAY THROUGH SUNDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Overnight...Ceilings lowering to MVFR and IFR with some showers expected, and with isolated thunder possible. Southeast wind 8 knots or less. Wednesday...MVFR and IFR in the early morning, improving to VFR ceilings. A chance of showers and thunderstorms. The rain may be locally heavy in the afternoon. Wind becoming south to southwest 8 to 12 knots with gusts near 20 knots. OUTLOOK... Wednesday night-Friday night...Showers and thunderstorms possible each day, most likely during the day and early evening. Lower ceilings and visibilities possible with the showers and thunderstorms. However, outside of any shower and thunderstorm activity, generally VFR conditions are expected. Winds generally from the south to southwest 5-10 knots, with gusts 15-20 knots during the day. Higher gusts in thunderstorms. Saturday...Chance of showers and thunderstorms continue with lower ceilings and visibilities associated with the showers and thunderstorms. Otherwise, generally VFR is expected. A surface trough pushes offshore late Saturday, shifting winds to the west to northwest for Saturday night and Sunday. && .MARINE... A warm front will lift slowly northward across the coastal waters of Delaware and New Jersey tonight and Wednesday. The wind should be from the east and southeast around 10 knots into tonight. The wind is forecast to shift to the south and increase to 15 to 20 knots on Wednesday in the wake of the warm front. Gusts around 25 knots are possible on our ocean waters on Wednesday afternoon. The Small Craft Advisory remains in place. Waves on our ocean waters should be 3 to 4 feet tonight, and 4 to 6 feet on Wednesday. Waves on Delaware Bay are expected to be 2 feet or less tonight, and 2 to 3 feet on Wednesday. OUTLOOK... Wednesday night-Friday night...Small Craft Advisory conditions may continue through the end of the week as southwest flow could keep seas around 5 feet and winds could gust 25-30 knots at times. Saturday-Sunday...Conditions may fall back below advisory levels, but winds may still gust near 20 knots at times and seas could remain near 4 feet. RIP CURRENTS... Increasing southerly winds and building waves, along with an underlying 9-second southeast swell, should result in a high risk for the development of dangerous rip currents along the New Jersey shore on Wednesday. A moderate risk is forecast for the Delaware beaches, where the coastline orientation should result in a slight offshore component to the prevailing wind. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...High Rip Current Risk from 8 AM EDT Wednesday through Wednesday evening for NJZ014-024>026. DE...None. MD...None. MARINE...Small Craft Advisory from 8 AM Wednesday to 6 PM EDT Thursday for ANZ452>455. Small Craft Advisory from noon Wednesday to 6 PM EDT Thursday for ANZ450-451. && $$ Synopsis...Miketta Near Term...AMC/Gorse/Iovino Short Term...Iovino Long Term...Davis/Miketta/Staarmann Aviation...Iovino/Miketta Marine...AMC/Iovino/Miketta
Area Forecast Discussion
National Weather Service Pocatello ID
237 PM MDT Tue Jul 31 2018 .DISCUSSION...Today Through Next Tuesday. Heat will be the main story today across SE Idaho, as high temperatures are projected to reach the upper 90s across lower elevations from the central Snake Plain southward. HeatRisk guidance is brushing near Heat Advisory criteria today into tonight, but concur with the overnight shift that the need for an advisory is marginal, with qualifying values covering less than half of any given forecast zone. In addition, quite a bit of smoke and haze remains across the region per surface observations and GOES-16 satellite imagery, and some scattered high-level cloud cover is starting to push into the western half of the forecast area. How much these factors might influence high temps is uncertain, but if anything it nudges our confidence further away from considering a Heat Advisory. See the CLIMATE section below for more on our ongoing heat wave. We do also carry a slight chance (15-25%) of isolated showers/t-storms this afternoon and tonight across the Central Mntns, Upper Snake Highlands, and western Southern Highlands. High-res HREF ensemble CAMs are carrying some echoes, but are generally not showing significant cores with very limited activity on the 40 dBZ paintball plot, reinforcing our thinking that activity will be quite isolated with limited t-storm potential. With very dry air in the low levels and strong inverted-V soundings/modest DCAPE values, but otherwise unimpressive instability and shear, greatest threats from any storms today/tonight will be gusty winds and lightning strikes, with very little precip expected to reach the ground. Greater monsoonal moisture will surge into ID Wed, with a chance of showers/t-storms everywhere. The two corridors most favored by the HREF ensemble and even NAM/GFS guidance are across the Central Mntns, Upper Snake Plain, Island Park region, and Teton Valley, and then across the Southern Highlands and Bear Lake region. For these two zones we`ve added scattered t-storm coverage, isolated in between. NAM forecast soundings show PWAT values rising into the 0.75 to 1.00 inch range, indicative of that increasing mid- level moisture, while soundings continue to show inverted-V signatures with LCLs at or above the melting layer and impressive DCAPE values reaching 1,000 to 1,500 J/kg. Thunderstorms should still be somewhat dry, but heavy downpours will be possible with the stronger cells, and strong downdraft/outflow winds in excess of 50 MPH will still be the greatest threat along with perhaps some hail. Some increased deep-layer wind shear up to 35 knots (best to the north) may aide in a bit in storm organization and longevity. A severe thunderstorm cannot be ruled out with strong damaging winds the greatest threat, although meager surface instability may be a limiting factor. Lightning and gusty winds will remain key concerns for fire weather partners, and with scattered coverage expected, we have issued Red Flag Warnings for large portions of the area. See the FIRE WEATHER section below for details. We will have to monitor morning cloud cover, as this could limit afternoon instability. We hold on to a chance of some showers/t-storms for some of our mountain ranges Thurs afternoon/eve, but otherwise Thurs kicks off a drying trend as a weak cold front crosses the region. This will usher in much drier air/low RH values along with higher winds Thurs and Fri afternoons, both of which may reach critical thresholds to necessitate additional Red Flag Warnings. Beyond Fri, we currently hold the forecast dry, but it should be noted that this is a low- confidence forecast with both the GFS/ECMWF hinting at a disturbance Sun. The models then diverge significantly as the GFS builds a ridge over the region with continued dry conditions, while the EC and Canadian bring a strong low pressure system/attendant trough across the northern Rockies. Expect adjustments to the forecast as we watch how the models trend with these features. - KSmith/DMH && .AVIATION... Upper ridge beginning to shift east across the region today. Moisture streaming east from Oregon producing light radar returns in mainly upper level cloud shield. Expect any convection that could develop today to be dry with little precipitation reaching the ground. Thus, VFR conditions expected to continue, though wind gusts >40 MPH will be possible. Best chances of this activity impacting terminals will be at KSUN early, transitioning east through the evening with VCSH for KDIJ. Cannot rule out weak convection continuing overnight, but much better chances occur during the day Wednesday. KPIH currently appears to have the least chance to be affected by thunder, but do anticipate threat is enough to have VCTS for that terminal during the afternoon. - DMH && .FIRE WEATHER... Moisture beginning to work into the region under the apex of upper level ridge. Isolated dry thunderstorms remain possible through the evening for almost all but the Snake Plain. Depth of moisture increases tonight through Wednesday, with greater coverage of thunderstorms expected during the day. Storms transition to hybrid wet/dry, though limiting factor could be early cloud cover. Have pulled early trigger on Red Flag Warning for Wednesday afternoon and early evening for widely scattered or better thunderstorm coverage. Upper trough transitions east across the panhandle into Montana on Thursday, dragging surface frontal boundary with it. Thunder expected to remain a potential threat mainly ahead of the surface boundary. Much drier air pushes into the region behind the front, and combined with deep mixing, expect winds and humidities to exceed critical thresholds. These conditions continue into Friday. Thus once thunder threat decreases, both days look to be another Red Flag day just for different criteria, and anticipate that will be issued or extended on upcoming shifts. Model trends continue to shift toward East Idaho remaining under the influence of weak Pacific energy. There is not a lot of confidence in an increased threat of thunder across the region, so forecast remains dry. Winds however do appear to be stronger, and this may be a concern depending on the humidities moving toward the weekend. - DMH && .CLIMATE... A historic long-duration heat wave continues into yet another week across SE Idaho. Pocatello Airport (KPIH) continues to add to it`s all-time record for longest streak of high temperatures at or above 90 since records began in 1939 that started back on July 4th, now sitting at 28 consecutive days as of today. Pocatello also continues to sit in 10th Place for highest July mean average temp as of Mon 07/30/18 at 73.5 degrees, which dropped just slightly and is holding us shy of the 9th Place value of 73.8 degrees from July of 1975. Burley Airport (KBYI) is sitting at 20 consecutive days at or above 90 as of today, holding it in 4th Place for longest streak since records began there in 1948. 3rd Place is 21 days ending August 20th, 1981. It is possible that some of our other non-climate sites have broken into the Top 10 for longest streaks at or above 90 as well this month. This heat wave has been historic in it`s persistence and duration, but not necessarily for extreme values. Only a few days have approached 100 degrees, and only a couple record high temps have been tied this month at our climate sites. As discussed in the DISCUSSION section above, today is slated to be one of the hottest days we have observed so far this summer, with high temperatures forecast to reach the upper 90s in lower elevations from the Snake Plain southward. Even with a light haze of smoke hanging over large portions of the region today and some high clouds observed on satellite pushing east across western ID, temperatures at Pocatello and Burley have already exceeded 90. Tomorrow will provide a slim shot to break the streak, with increased cloud cover due to showers and t-storms. Cooler temps Fri and Sat following a frontal passage may provide a slightly better chance of breaking the heat wave. Stay tuned. - KSmith/DMH && .AIR STAGNATION... Varying degrees of degraded air quality are expected to continue across SE Idaho for at least the next several days due to numerous wildfires burning across the Pacific Northwest. Haze/smoke remains evident today on both GOES-16 satellite imagery and surface observations, with local diurnal wind trends governing which areas will see the most smoke at any given time. The Sharps fire continues to be our greatest local contributor, but the HRRR smoke model clearly shows large smoke plumes advecting in from CA, OR, and NV as well. The Idaho Department of Environmental Quality (ID DEQ) currently rates air quality "Moderate" across the lower Snake Plain and eastern Magic Valley, meaning that air quality is acceptable, however, for some pollutants there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution. Air quality is now rated "Unhealthy for Sensitive Groups" in the Central Mntns. In general, the greatest smoke pooling will occur at night in valleys/lower elevations, and this is when the greatest impacts may be noticed. Have maintained mention of areas of smoke in the weather grids through at least Thurs morning. Some relief is possible by Thurs/Fri as a weak cold front ushers in stronger afternoon/eve winds across the region. - KSmith/DMH/NP && .PIH WATCHES/WARNINGS/ADVISORIES... Red Flag Warning from noon to 9 PM MDT Wednesday for IDZ410-413- 427-475-476. && $$
Area Forecast Discussion
National Weather Service Great Falls MT
847 PM MDT Tue Jul 31 2018 .UPDATE... Evening update has been published, with only minor adjustments made to POPs to account for latest radar trends and Hi-Res model guidance. In addition to minor tweaks to POPs, also added smoke and haze for areas south and west of a Cut Bank, to Great Falls, to Lewistown line to account for observations and latest HRRR smoke guidance. A weak wave embedded within the upper level southwest flow will rotate across the ridge axis tonight and across portions of Central and Southwest Montana. This disturbance is expected to bring isolated-to-scattered showers and even a few isolated thunderstorms to areas generally along and south of a Helena to White Sulphur Springs line. Otherwise, left the Fire Weather Watch for Fire Weather Zone 112 for Wednesday afternoon/evening as is so that the midnight shift can re- evaluate with the latest model sweet. - Moldan && .SYNOPSIS... Temperatures trend warmer Wednesday into Thursday. Scattered thunderstorms are possible across southwest Montana Wednesday and Thursday afternoons. Breezy west winds develop later on Thursday into Friday as a dry cold front moves through the state. && .AVIATION... Updated 2330Z. VFR conditions are expected to prevail across Southwest and North Central Montana beneath scattered to broken high cloud cover. A weak disturbance moving across Idaho/Southern Montana/Wyoming this evening may spark off a few isolated thunderstorms south of the Interstate 90 corridor and along the Continental Divide, however, confidence was to low to put any mention of TS in this TAF package for the KEKS, KBZN, and KHLN terminals. Haze from fires originating further west will continue to impact the region, which will lead to reduced visibilities and potentially some mountain obscuration. Finally, variable winds will gradually increase and turn to the southwest/west tomorrow as a disturbance develops over Southern Alberta Canada. - Moldan && .FIRE WEATHER... Hot and dry weather returns on Wednesday as an upper level ridge settles over the region. Low pressure develops Wednesday afternoon over southern Alberta. This will create gusty winds, combined with low afternoon relative humidity. A Fire Weather Watch has been issued for Wednesday afternoon across western portions of zone 112. Isolated to scattered dry thunderstorms are possible Wednesday and Thursday afternoon over the central mountains into southwest Montana. A dry cold front is expected to arrive later Thursday evening, possibly producing critical fire weather conditions across North-central Montana Thursday afternoon through Friday. && .PREV DISCUSSION... /ISSUED 530 PM MDT Tue Jul 31 2018/ Tonight through Wednesday Night... Very warm air will move back over the entire forecast area again on Wednesday, as many lower elevation areas warm well into the 90s. The airmass will become unstable once again with the warming temperatures and another disturbance will bring another round of isolated thunderstorms during the afternoon and evening hours. Thursday through next Tuesday...The high pressure ridge aloft breaks down over our CWA on Thursday as a Pacific cold front sweeps eastward over our region and a shortwave trough approaches from the west. Isolated showers and thunderstorms remain possible along and ahead of this front on Thursday. The shortwave trough then traverses our area on Friday into Saturday morning, allowing the potential for a few showers and thunderstorms to persist. An overall drying trend is then expected the rest of the weekend as a shortwave ridge builds from the west. A longwave trough aloft and embedded disturbances then overspread our CWA from the west Monday and Tuesday of next week, renewing the potential for a few showers and thunderstorms. The above pattern and diurnal mixing of the boundary layer will promote breezier southwesterly to westerly surface winds, mainly this Thursday/Friday and perhaps again on Monday/Tuesday of next week. These winds will contribute to the likelihood of critical fire weather conditions developing this Thursday and Friday. Please see the fire weather discussion for further details. Low temperatures trend near-normal through next Tuesday. After slightly above-normal highs on Thursday, high temperatures will trend near or slightly below-normal for the balance of the period. - Jaszka && .PRELIMINARY POINT TEMPS/POPS... GTF 58 96 60 94 / 10 0 10 0 CTB 54 93 54 89 / 0 0 0 0 HLN 58 93 60 91 / 10 10 10 10 BZN 53 90 55 90 / 20 10 10 20 WEY 39 80 42 81 / 20 30 30 20 DLN 53 86 53 87 / 20 20 20 20 HVR 58 97 60 96 / 0 0 0 0 LWT 55 89 58 89 / 10 0 10 10 && .TFX WATCHES/WARNINGS/ADVISORIES... Fire Weather Watch from Wednesday afternoon through Wednesday evening Deerlodge/Western Beaverhead National Forest...Eastern Beaverhead National Forest. Fire Weather Watch from Wednesday afternoon through Wednesday evening Eastern Glacier/Toole/Central/Eastern Pondera/Liberty. && $$ http://www.weather.gov/greatfalls