Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 09/21/16


Area Forecast Discussion
National Weather Service La Crosse WI
633 PM CDT Tue Sep 20 2016 .SHORT TERM...(This evening through Wednesday) Issued at 325 PM CDT Tue Sep 20 2016 Main concerns are on heavy rainfall tonight through Thursday and the possibility for flash flooding. This could potentially be a serious flooding situation! Ongoing showers and isolated thunderstorms will weaken this afternoon then severe thunderstorms are expected to develop late this evening into the overnight hours with the main threat of heavy rainfall. Some of the storms may also produce damaging winds and perhaps large hail if updrafts are rotating. A warm front lifts north into the area tonight brining a tropical airmass into the area with precipitable water values climbing to 1.5 to 1.8. These values combined with warm cloud depth of 3.5 to 4 km will set the stage for a potential flash flood event. The nose of the low level jet focuses into the front tonight with 850 mb moisture transport of 300 to 500 units slamming into the front. All of this combined with 30 day mean precipitation values of 200 to 300 percent over the mean, primes the area for flash flooding. Storms look to initiate over portions of southeast Minnesota into west central Wisconsin along the front and then edge southward with time. So, the storms/heavy rainfall may build south into northeast Iowa and southwest Wisconsin. The storms will capable of producing very heavy rainfall, 2 inch per hour rates are possible. Damaging winds are also possible. Storms will be ongoing by sunrise on Wednesday then are expected to gradually taper off through the morning hours. Round two of heavy rainfall takes aim on the area late in the day on Wednesday into the overnight hours. This is when some of the most serious flooding could develop, especially if this rain falls over the same areas as Tuesday night into Wednesday morning. A few forecast models attempt to push this second round of heavy rain to the north. Not really buying into that given that outflow from the storms will help to drive the warm front south...potentially closer to the interstate 90 corridor. The heavy rain threat finally tapers off by Thursday evening. .LONG TERM...(Wednesday night through Tuesday) Issued at 325 PM CDT Tue Sep 20 2016 For Thursday night into Friday...shower and thunderstorm chances continue, its just a questions of forcing for the storms. The warm front meanders in the neighborhood so there is the chance of seeing more rain...potentially heavy. Will continue to monitor closely since this would only worsen any ongoing flooding issues. Friday night through Tuesday.... A deep upper-level trough will be in place over the Rockies for the start of the weekend. Ahead of the trough, lower-level WAA/isentropic lift will provide forcing for a broad band of showers, possibly with isolated thunder, stretching from the central Dakotas into southeast Minnesota/southern Wisconsin Friday night. 20.12z GFS/20.00z ECMWF are in agreement with lifting the thermal gradient northward into Saturday, temporarily clearing our CWA of rain chances. Models become increasingly divergent thereafter. As an upper-level cut-off low detaches itself from the main flow over the Four Corners region, the GFS becomes much more progressive, racing the upper-level trough the Great Lakes region by Monday night. Meanwhile, the ECMWF holds the trough over the Northern Plains until Tuesday. This will be the determining factor for the timing and duration of another round of rain Sunday into Monday. After this system departs the region, high pressure is progged to build in. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 633 PM CDT Tue Sep 20 2016 The latest runs of the hi-res meso models continue to indicate the warm front over central Iowa will lift north toward the area this evening. Convection is expected to form north of this front as the low level jet starts to impinge on it late this evening. The 20.22Z run of the HRRR is the first to bring this activity in and have gone with a VCTS on its faster timing and then gone with categorical showers and storms for much of the overnight. Initial VFR conditions should drop down to MVFR in the convection with some IFR possible in the heavier rains. This activity should continue into Wednesday morning until the low level jet weakens allowing for a break in the rain. Guidance is mixed on whether ceilings will drop to IFR behind the rain or go up to VFR and opted to stay with persistence from the previous forecast with VFR. The front will still be in the area for Wednesday afternoon with another round of convection expected to develop in the afternoon. For now, will show a VCTS at both sites all afternoon but this could hold off until mid afternoon once the low level jet starts to increase and interact with the front again. && .HYDROLOGY...Tonight through Thursday Issued at 325 PM CDT Tue Sep 20 2016 A potentially serious flooding situation is taking shape for tonight through Thursday. Two main rounds of heavy rainfall. The first, tonight into Wednesday morning. The second round is expected Wednesday evening into the overnight hours. Rainfall amounts of 2 to 3 inches with locally higher amounts in excess of 7 inches possible. Given the very wet conditions across the region flooding could develop quickly. If these two rounds of heavy rainfall occur over the same area the flooding could be some of the worst experienced by many. Stay weather aware and be ready to move to higher ground! Several rivers could go into flood. Minor to major river flooding is possible. && .ARX WATCHES/WARNINGS/ADVISORIES... WI...Flash Flood Watch from 1 AM CDT Wednesday through Thursday evening for WIZ017-029-032>034-041>044-053>055-061. MN...Flash Flood Watch from 1 AM CDT Wednesday through Thursday evening for MNZ079-086>088-094>096. IA...Flash Flood Watch from 1 AM CDT Wednesday through Thursday evening for IAZ008>011-018-019-029-030. && $$ SHORT TERM...WETENKAMP LONG TERM...WETENKAMP AVIATION...04 HYDROLOGY...WETENKAMP
Area Forecast Discussion
National Weather Service Bismarck ND
947 PM CDT Tue Sep 20 2016 .UPDATE... Issued at 948 PM CDT Tue Sep 20 2016 Near term high res models doing fairly well this evening. Made some adjustments to better reflect latest radar imagery otherwise the forecast is on track with no major edits from the previous issuance. UPDATE Issued at 659 PM CDT Tue Sep 20 2016 The inherited forecast remains mainly on track. Main edit for the early evening forecast issuance was to tweak POPs based on latest regional radar and near term guidance along with cloud cover. Hard to say anything is reaching ground underneath weak radar returns about the region, but Sidney MT did report light rain an hour or two ago so inserted a greater coverage of low POPs northwest and north central. Will maintain slight thunderstorm chances through tonight with both the NAM12 and RAP indicating several hundred J/KG of MUCAPE southwest into far south central now and through the overnight. Had thunderstorms this morning under a similar environment so cannot justify removing. && .SHORT TERM...(This evening through Wednesday) Issued at 302 PM CDT Tue Sep 20 2016 A split flow regime will develop across the western CONUS and Canada leading to the eventual development of a closed low over the Great Basin by Thursday. During this development, southwest flow aloft will become predominant over the northern plains allowing both shortwave energy and mid to high level moisture to stream north into the region. This will set up a scenario that will support both precipitation efficiency due to the tropical plume, and due to the slow movement of the closed low, a rather extended period for rain chances. For the short term period, rain showers and scattered thunderstorms will develop across western and North Dakota late this afternoon and tonight as the first in a series of weak shortwaves move through the region. The CAM models all are in agreement with the best chances across the north tonight. With Cape very limited will generally go with showers across the north tonight. By Wednesday the wave moves through and scattered showers and a isolated thunderstorms will linger. Highs on wednesday will be cooler, in the 60s. .LONG TERM...(Wednesday night through Tuesday) Issued at 302 PM CDT Tue Sep 20 2016 Main feature in the long term will be the negatively tilted h500 low forecast to move from the Great Basin region Thursday eventually merging into the northern stream trough over the northern and central plains by Saturday-Sunday. While both the GFS and ECMWF are in general agreement the ECMWF is definitely more progressive in merging this upper low with the northern stream on Saturday. With a fair amount of uncertainty on the track and timing will end up focusing the highest pops west Thursday and Friday where there is more certainty. Then Saturday a good push of moisture should swing through the central sections of the region as the upper low swings through. Storm total rainfall is forecast to be nearly 2 inches far northwest to around a half an inch south central. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 659 PM CDT Tue Sep 20 2016 Increasing sky cover with rain showers moving in across western into parts of north central North Dakota tonight with KISN and possibly KMOT being impacted with rain. CIGS and VIS should remain VFR through the 00Z period with a low VFR (4-6K Feet AGL) the lowest cloud deck expected. && .BIS WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...NH SHORT TERM...WAA LONG TERM...WAA AVIATION...NH
Area Forecast Discussion
National Weather Service Denver/Boulder CO
843 PM MDT TUE SEP 20 2016 .UPDATE... Issued at 824 PM MDT Tue Sep 20 2016 Satellite pictures show a significant batch of mostly upper level cloudiness moving over the CWA in southwesterly flow aloft. Some of cloudiness is lower upstream with radars showing some showers over the CWAs to the west and southwest. Models keep the extensive mid and upper level cloudiness over the CWA overnight and much of Wednesday. Will increase the cloud cover on the sky grids. Pops overnight look okay. Will keep them out of the dry plains for sure. Temperatures will stay pretty warm with all the cloud cover overnight. && .SHORT TERM...(This evening through Wednesday) Issued at 257 PM MDT Tue Sep 20 2016 For the remainder of today it will unseasonably warm and will remain dry area-wide other than an isolated storm or two for the Central Colorado Rockies. This evening and tonight the remnants of Tropical Storm Paine off the coast of Mexico will phase with a cut off low off the coast of southern California. Zonal flow at 500 mb exists across the northern Rockies, while the 500 mb ridge is centered over Oklahoma. The result for Colorado is SW mid and upper level flow across Colorado with considerable upper level moisture continuing through the short term. The moisture from the is advected for the next 36 hours and should keep us mostly cloudy. A subtle short wave trough crosses Colorado before sunrise Wednesday and both the NAM and the HRRR initiate light precipitation in the mountains and sustains the showers across the Denver metro area. It`s still quite dry in the low levels so have low confidence in rain reaching the ground, but have seen enough in the high res model signal to raise PoPs after 3 AM local time to slight chance for the metro area. Minimum temperatures tonight will stay in the low 60s across the Denver metro area and eastern Plains, and in the 40s in the mountains given the warm temperatures this afternoon and expected cloud cover tonight. Throughout the day on Wednesday, a deep/strong trough will dig south along the Pacific Northwest coast. This will continue to advect upper level moisture across Colorado keeping the area mostly cloudy. The low-levels will continue to be dry with surface dewpoints will be in the lower and mid 40s across the Plains, 30s in the mountains. Once again the best chance for afternoon thunderstorms will be over the central Colorado Rockies. In terms of temperatures, the warm overnight lows coupled with the dry low- level air means temperatures should still have little trouble getting into the mid 80s east of the mountains despite the mid and high cloud cover. However, the cloud deck should be thicker than today as so temperatures will be a few degrees cooler than Tuesday, but still well above average for this time of year. .LONG TERM...(Wednesday night through Tuesday) Issued at 257 PM MDT Tue Sep 20 2016 For Wednesday evening, could see just a couple showers and an isolated storm drift northeast across the mountains, but overall the airmass will be too stable and subsident to support much precipitation. Lower elevations should remain dry. Temperatures will stay quite mild but a cold front is expected to push into the northeast plains toward Thursday morning. This front may usher in some stratus across the northeast plains and lead to some cooling especially on the northeastern plains for Thursday. The airmass will destabilize in the afternoon but mainly over the mountains as the boundary layer cools slightly on the plains. Could still see a couple storms drift off the higher terrain or develop on the plains toward late in the day if slight cooling aloft occurs ahead of the deep upper level low dropping into the Great Basin. It appears the best chance of precipitation may occur Friday as the upper level low approaches from the west. Right now, all medium range models are pointing to a piece of energy rotating out of this low and across the forecast area. This along with cooling aloft should effectively destabilize the atmosphere so will have the best PoPs then. Winds are also expected to increase from the mountains eastward across the Palmer Divide and most of the plains with strong southerly flow and pressure gradient in place. Temperatures expected to get cold enough in the mountains for some snow potential but appears we`ll be getting into the dry slot so threat for much accumulation appears quite limited into Friday night. By Saturday, the upper level trough will begin to fill and gradually shear. We will still be under the cold pool aloft so will continue to keep a chance of showers and a few storms in the forecast. Temperatures will turn considerably cooler with highs mostly in the 60s on the plains and 40s/lower 50s in the mountains. The cooler weather will remain in place through Sunday, Monday, and Tuesday as the trough weakens and/or shears southward into the Desert Southwest. The chance of precipitation will likely decrease through this period. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 824 PM MDT Tue Sep 20 2016 Normal drainage winds are in place at DIA this evening. They should continue with pretty weak speeds. There will be plenty of mid and upper level cloudiness all night and most of Wednesday. There should be no precipitation or ceilings under bkn-ovc100. && .BOU Watches/Warnings/Advisories... None. && $$ UPDATE...RJK SHORT TERM...Schlatter LONG TERM...Barjenbruch AVIATION...Meier
Area Forecast Discussion
National Weather Service Grand Rapids MI
758 PM EDT TUE SEP 20 2016 LATEST UPDATE... Update/Aviation .SYNOPSIS... Issued at 330 PM EDT Tue Sep 20 2016 After a quiet overnight period, scattered showers and thunderstorms will become possible on Wednesday and linger through Thursday night. The most commonplace rainfall will occur over Central Lower, with less rain as one heads south. Very little, or even no rain may occur toward I-94 through Thursday night. The scattered rain may linger until Friday evening before we finally dry out for a what looks like a quiet weekend. Another chance of rain moves back in for Sunday night. Wednesday and Thursday will remain warm, with highs in the upper 70s to lower 80s, but then we will cool down. Highs will mainly be in the upper 60s to lower 70s Friday through Tuesday. && .UPDATE... Issued at 747 PM EDT Tue Sep 20 2016 The update reflects more in the way of cloud cover tonight. Also...I included a potential for showers up north for tonight. The elevated showers developing in northeastern Wisconsin are shown to build southeast with some of the HRRR runs...into Big Rapids and eventually Mount Pleasant. Satellite imagery also shows cloud building on top of us...so more in the way of cloud cover is likely to occur for tonight. && .SHORT TERM...(This evening through Thursday night) Issued at 330 PM EDT Tue Sep 20 2016 Rain chances return early Wednesday and linger into Thursday night as a surface boundary hangs up over the region. High pressure will drift off to the east overnight as a slow moving front sags SE across the U.P. We will begin to see moisture advection by daybreak and an increase in mid level clouds. We may even see an isolated shower or storm advance toward the lakeshore by daybreak Wednesday. The front stalls over Northern or Central Lower Wed and Thu before finally drifting a bit south Thu night. Much of the pcpn will be concentrated near the front. Upper waves will travel along it, but they appear to weaken as they head our way, being much stronger over MN/WI/IA. Will continue to feature highest POPs across Central Lower with placement of the front, but a bit more widespread rain should be seen late Thursday night with the front advancing a bit south. Also expect to see an enhanced rain late Wednesday afternoon into Wednesday night across Central Lower with moderate upper divergence sliding across from the upper jet. High temps will be tricky over the next couple of days, largely depending on the amount of sun that occurs. Mid 80s are certainly possible with enough sun, which may occur in the far south. But overall expect more upper 70s to around 80 to occur with a fair amount of clouds around. Therefore I did lower max temps for Wed in most places. .LONG TERM...(Friday through Tuesday) Issued at 330 PM EDT Tue Sep 20 2016 Plains cyclogenesis may increase mid level warm advection/isentropic ascent enough to bring showers Friday night into Saturday. This is followed by shortwave ridging ahead of the western CONUS upper trough and generally fair weather Saturday into Sunday. Precip chances increase again Sunday night and Monday as heights fall and sfc cold front/prefrontal trough moves in. There is still low confidence here as ensemble spread continues to be large and the precip may hold off until Monday night and Tuesday as indicated by the slower solutions. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 747 PM EDT Tue Sep 20 2016 Will need to monitor the thunder risk for late tonight and Wednesday morning for KMKG and KGRR. Convection is expected to become widespread over in Wisconsin tonight. The storms should build east later tonight and eventually reach into MI for primarily Wed AM. Thus I added this to the forecast. Showers currently in northern WI will likely build southeast and could reach KGRR and KLAN in the middle of the night. The storms should dissipate by noon...with a break expected then. The risk for storms will increase again after 00z Thu. && .MARINE... Issued at 330 PM EDT Tue Sep 20 2016 Winds will be fairly light through the short term and will become offshore. So no headlines are expected. However 2-3 foot waves will be possible Wed afternoon north of Grand Haven with a south flow around 15 knots. && .HYDROLOGY... Issued at 330 PM EDT Tue Sep 20 2016 Hydro impacts through this weekend will be limited. Rain and thunderstorm chances will exist Wednesday and Thursday, mainly north of I-96. A frontal boundary draped across Central Lower Michigan will be the focus for diurnally-driven shower/storm activity. Total rainfall amounts will likely exceed half an inch (0.50 inches) well to the north of I-96, affecting the Upper Muskegon River basin and Pere Marquette River basin. Mostly within bank river rises are expected. && .GRR Watches/Warnings/Advisories... MI...None. LM...None. && $$ UPDATE...MJS SYNOPSIS...JK SHORT TERM...JK LONG TERM...Ostuno AVIATION...MJS HYDROLOGY...EBW MARINE...JK
Area Forecast Discussion
National Weather Service Wilmington NC
1055 PM EDT Tue Sep 20 2016 .SYNOPSIS... An upper cutoff low across the eastern Carolinas, will catch the remnants of Julia during Wed. This conglomerate will meander across the eastern Carolinas through the end of this week before finally getting drop kicked off to the ne late Fri. This will accelerate it away from the carolina coasts early this weekend. Weak high pressure will temporarily build into the area on Sat. A strong cold front will move across the area during Sunday followed by strong high pressure in its wake bringing the first hint of Autumn early next week. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... As of 945 PM Tuesday...The cutoff upper low meandering across the Carolinas has finally been able to wrap, counter clockwise, the Atlantic moisture from off the northern Outer Banks, back to the southwest which is now falling as light rainshowers across the western portions of the ILM CWA...via latest mosaic radar trends. The HRRR, RAP and the HighResWrf, all 3 illustrate this potential increase in the wraparound moisture falling across the FA overnight into the next period. The forcing from the cutoff low is aiding the generation of pcpn tonight. If the low clouds areable to scour out some after sunrise Wed, then instability will be added to the equation. This will result in a further increase in convection, with thunder being added to the mix during Wed mid to late morning. As for cloudiness, increased the low stratus coverage to mostly cloudy or just plain cloudy phraseology for sky conditions overnight. For temps, will stay on the milder side of model Mos Guidance for tonights lows. Overall POPs tonight will remain in the low to modest chance categories, with the overall hier chances across the western 1/2 of the ILM CWA. With PWs in the 1.75 to 2.00 inch range, moisture availability will not be the problem for pcpn development. Previous......................................................... As of 300 PM Tuesday...An upper low spinning around in theACarolinas will continue to provide unsettled weather across the area through tonight. Low clouds and spotty light showers or drizzle were covering much of the area into this afternoon. A moist northerly flow was wrapping around the remnant low from Julia as some drier air aloft wraps around the back of the upper low. Sounding data and time height sections show drier air aloft from h70 and above which looks like it may mix down enough to produce a few breaks in the clouds especially across inland. This all makes for a tricky forecast as the clouds will hamper heating and therefore instability while areas that see any sunshine will become more unstable and should see some convective development this aftn. The cool pool aloft will drift south over the area helping to sharpen lapse rates and promote some convection associated with differential heating or low level convergence. It looks like the best upper level energy and support will ride around the upper low and combine with best convergence associated with sfc low to produce best chc of shwrs from N-NE to S-SW across the area through tonight. HRRR shows pcp mainly aligned along I-95 corridor and west with only spottier shwrs to the east closer to the coast. With such a cool pool aloft, you can not rule out isolated thunderstorms, but temps were struggling to make it much past the mid 70s limiting the sfc heating needed to steepen lapse rates. Temps will hold in the mid 70s in most places and will not drop too much tonight under a very moist air mass with plenty of cloud cover. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/... As of 300 PM Tuesday...The remnants of Julia or a broad area of low pressure/trough will remain up the Carolina coast through mid week. Initially the circulation will drift southwest as it continues to be pulled by upper low. This will leave a moist northerly flow across much of the area through Wed into Thurs. The models are not in total agreement with evolution of this low/trough but it looks like it will be pulled back westward briefly on Wed which may produce a period of on shore flow and possibly enhance low level convergence but also may enhance thunderstorm activity along the coast. It will depend on the exact location of the low, both at the surface and aloft, to determine where the best convergence, lift and upper level support will be, but the potential will exist with a decent cool pool aloft. Overall, expect a good deal of clouds and showery weather through much of the period with isolated thunderstorms possible. o && .LONG TERM /FRIDAY THROUGH TUESDAY/... As of 300 PM Tuesday...Remnant mid-level circulation of Julia will still be overhead by Friday, before finally lifting off to the NE as high pressure builds across the area on Saturday. Friday will be near seasonable temperatures with periods of clouds of showers, but as subsidence develops behind the departing upper impulse, Saturday will likely rise to above climo again with mucho more sunshine. This warmth will be short-lived however, as a deep trough then digs into the northeast driving a back door type cold front into the Carolinas Sunday, with much cooler temperatures lasting into the beginning of next week. Increased clouds and showers are possible Sunday into Monday with the FROPA, but the forcing is weak and moisture is limited to the lowest part of the column. This suggests more clouds/drizzle into Monday than true showers, but will carry low-end POP before drying out by Tuesday. Temps Sun-Tue will drop to more seasonable levels, and our first taste of fall-like temperatures may occur early next week. && .AVIATION /02Z WEDNESDAY THROUGH SUNDAY/... As of 00Z...Pretty ugly aviation conditions tonight through the overnight hours with IFR conditions becoming widespread due to stratus. Likewise visibilities will lower below two miles at times due to drizzle. Conditions will be at their worst from 06Z-13Z, with slowly improving conditions after 15Z. North northwest flow is expected through Wednesday morning, becoming more easterly in the afternoon. If we get any sun on Wednesday (which is pretty unlikely), we could see some heavier convection in the afternoon. EXTENDED OUTLOOK...Isolated to scattered afternoon and early evening convection possible underneath the cutoff upper low through Friday. MVFR/IFR morning stratus/fog possible each day thru Sunday. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 1000 PM Tuesday...The cutoff low across the eastern Carolinas this evening is progged to capture whats left of Julia at the sfc and become partly barotropic. The sfc pressure pattern overnight will result in a nw to n wind directions. The resultant wind speeds will only be around 10 kt due to a somewhat relaxed sfc pg. Significant seas overnight will run only 2 to 3 ft. Dominant periods will run 7 to 8 seconds due to a pseudo swell from the ese around 1 foot. Wind waves at 4 second periods will at times dominate the significant seas overnight. Previous.............................................. As of 300 PM Tuesday...Northerly winds will back a little overnight as low pressure gets pulled southward, but overall expect N-NW 10 to 15 kts. Winds will diminish a bit and become more variable overnight. Seas will remain less than 3 ft. SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGoHT/... As of 300 PM Tuesday...Northerly winds may become quite variable as remnant low of Julia gets pulled southward and possibly inland late Wed. This should produce a more on shore flow on Wed. Overall winds and seas will be determined by the exact fate of this remnant low/trough through mid week. A longer period up to 12 second SE swell will mix in by Wed night into Thurs. LONG TERM /FRIDAY THROUGH SUNDAY/... As of 300 PM Tuesday...A mostly weak gradient with N/NW winds will persist Friday and Saturday ahead of a back door type cold front which will sag across the waters during Sunday. Wind speeds Fri/Sat will be light, 5-10 kts or less, before steadily increasing behind the front to 10-15 kts from the NE during Sunday. WHile the wind will provide littloe contribution to the sea spectrum, a 3-4 sec/11 sec SE swell from Tropical Cyclone Karl will exist both Friday and Saturday, producing seas of 2-4 ft. On Sunday, this swell will slowly wane but a NE 5-6 sec wave will quickly amplify, producing wave heights of 3-5 ft the latter portion of the extended. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...JDW NEAR TERM...DCH/RGZ SHORT TERM...RGZ LONG TERM...JDW AVIATION...DL
Area Forecast Discussion
National Weather Service Lincoln IL
837 PM CDT TUE SEP 20 2016 .UPDATE... Issued at 837 PM CDT Tue Sep 20 2016 No significant updates needed this evening as high pressure axis into central IL combined with westerly flow remaining north of the area should keep convection forming over the upper Midwest from moving into central IL overnight. Lows should reach the lower 60s east of I-57 ranging up to the upper 60s west of I-55 where higher dewpoints and slightly higher southerly winds prevent as much cooling. && .SHORT TERM...(This evening through Wednesday) ISSUED AT 239 PM CDT Tue Sep 20 2016 Weak boundary a bit tough to pick out this afternoon on surface obs, but best estimates are that it extends from near Macomb to just north of Danville. Cumulus field continues to expand along the boundary to near the I-70 corridor this afternoon. No sign of any convection yet, but SPC mesoanalysis shows CAPE`s are now in the 3000 J/kg vicinity and the cap is eroded. Latest HRRR has now started hinting at some isolated development, and will maintain the isolated PoP`s for this afternoon, mainly between the Illinois River and I-70. Main steering flow will remain to our north through Wednesday, and overnight MCS which is progged to develop over southern Minnesota and northern Iowa will track into Wisconsin and extreme northern Illinois on Wednesday. Local impacts would mainly be some cirrus blowoff across the northern CWA, but skies should again be mostly sunny. With little air mass change going on, have bumped up highs for tomorrow a couple degrees and mainly went around 88-89 degrees over the entire forecast area. .LONG TERM...(Wednesday night through Tuesday) ISSUED AT 239 PM CDT Tue Sep 20 2016 Somewhat flat ridge will remain anchored over the southern part of the US for the last part of the week and then begin to build into the northern Miss valley for the weekend, as an upper level trough pushes east into the plains. This pattern will bring dry and very warm conditions to the CWA through the rest of the week and into the weekend. With 850 temps reaching to between +18C and +20C, expecting highs in the mid to upper 80s through most of the forecast period. The extended models remain different in their timing of the upper level trough for the latter part of the weekend. The ECMWF has been the most consistent and slowest over the last several days so will lean toward that solution and have gone several degrees warmer than guidance for highs for Sun and Mon. The associated frontal system finally gets into the state Sunday night and this will be the next real chance of precip in the area. The chance of precip will diminish as you go east and southeast, so chance pops will be in the northwest for Sun night/north and northwest Monday/and small area in the northeast for Monday night. By Tue, dry weather should return to the area. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 636 PM CDT Tue Sep 20 2016 VFR conditions expected the next 24 hours as high pressure keeps the track of convective systems to the north. Winds generally S-SE through the period. Speeds generally under 6 kts overnight, then 8-10 kts after 16Z. && .ILX Watches/Warnings/Advisories... NONE. && $$ UPDATE...Onton SHORT TERM...Geelhart LONG TERM...Auten AVIATION...Onton
Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
911 PM CDT TUE SEP 20 2016 .UPDATE... 911 PM CDT Main forecast concern continues to be with shower and thunderstorm potential in the late overnight through Wednesday morning. 00z RAOBs across the region sampled ample elevated instability. On the nose of a 30-40 kt 850 mb low level jet, convection is beginning to fire over southern Minnesota as expected. There is likely to be an expansion of coverage into extreme NE IA and western WI, with shear/MUCAPE supportive of some severe storms. The main question is evolution of this convection later overnight. High-res guidance has been insistent on clustering/merging into at least a loosely organized MCS. Mid and upper level thickness and mean wind pattern, along with Corfidi vectors would argue for a east- southeast propagation, which could keep it north of our area. Overall, convection would likely be on a weakening trend with slightly lower MUCAPE and weakening veered LLJ over our area, though cannot completely rule out a stronger embedded storm northwest of Rockford. Another wild card is if there is any cold pool propagation which could force storms farther south and/or serve as a focus for additional convection, something that the HRRR and a few other hi-res models have been trying to hint at. With variation in guidance and competing factors for how far south convection may make it into the CWA by the early morning, confidence is low. Largely maintained previous forecast PoPs, with some minor tweaks to slow them to predawn hours in far north areas. RC && .SHORT TERM... 306 PM CDT Through Wednesday... Main forecast concerns/challenges are with thunderstorm chances very late tonight into Wednesday morning, with a definite possibility for for an upstream MCS to move southeast into northern Illinois Wednesday morning. In the near term, high pressure has settled in across the region, helping for some quieter weather today. Under sunny skies, temperatures have rebounded back into the 80s once again with upper 80s temps being reported across the southern CWA. The potential for isolated thunderstorms this afternoon is appearing to quickly lower despite instability and moisture pooling along remnant boundary over east central Illinois and northwest Indiana. Increased CU in the zone being observed, but once again, don`t really anticipate any precip this afternoon into the evening. Clearer skies this afternoon into the early evening will be replaced with current upstream cloud cover over the Upper Midwest, while low temps once again fall to the 60s. Will see the air mass change significantly tonight into Wednesday as mid to upper 60s dewpoint air pushes north over the entire CWA. This higher dewpoint air combined with upper 80s will bring humid conditions back on Wednesday. Focus will be on how expected upstream convection over MN/IA/WI will evolve later tonight. Guidance varying with the evolution of this thunderstorm development with one scenario keeping this precip to the north of the CWA through Wednesday morning. However, short term and hires guidance beginning to really key in on these thunderstorm diving southeast into northern Illinois early Wednesday morning. This is beginning to be a very probable solution, and have trended the forecast in this direction. Guidance consistent with instability/moisture axis shifting well north across much of the region by Wednesday morning. With this pattern in place, it would make sense that these thunderstorms would follow moisture/instability axis southeast into the CWA. High instability/steep mid level lapse rates are expected to also be in place that would support this scenario. So once again, trended forecast this way and increased pops with coverage wording. Did not go overly high on pops, given the possibility for this precip to not go as far south, but could see the evening shift increasing pops this evening once a better handle is grasped. If this precip does reach northern Illinois, timing would be 5-7 AM CDT for the Rockford area and then 8-10 AM CDT for the Chicago area. Would anticipate this precip to be on a decaying trend, but there is the possibility for some isolated stronger storms. If more robust development is present, large hail and strong winds would be the main threats. Precip chances should diminish by midday and early afternoon, but will also need to monitor any possible outflow boundary, which could support additional development in the afternoon. Rodriguez && .LONG TERM... 229 PM CDT Wednesday night through Tuesday... Wednesday Night through Friday: Broad 500mb ridging persists across the Southern Plains as an upstream trough is steadily digging south through California. This setup will keep the main channel of stronger vorticity oriented along a Central Plains to Northern Great Lakes. Surface ridging remains rather diffuse but positioned downstream of the Great Lakes, which could provide some weak steering of precip back north of Northern Illinois. In the near term for Wed ngt, the boundary will be setting up along or just north of I-80 in Northern Illinois, so have higher POPs in those areas meanwhile maintain dry conds to the south. Guidance tries to develop a shortwave along the lee-side of the Rockies in Colorado Thur morning, as the downstream southerly flow is poised to strengthen, this should help push the quasi- stationary boundary further north into Wisconsin. Thursday evening operational solutions continue to push the main frontal boundary north; however, there is some indications that a weak mid-lvl trough at 500-700mb may dip over Southern Wisconsin, which could bring some weakening showers/storms southeast towards Northern Illinois late Thur/early Fri. Then heading towards the end of the week the upstream 500mb trough will transition towards a cutoff low across the Southwest CONUS, as ridging downstream over the Great Lakes tries to amplify. Depending on cloud cover and precip chances over the next few days will dictate how warm surface temps become, but with the several days in the past being dry, afternoon highs will likely rebound to above climo conditions in the middle 80s and mild overnight temps in the low/mid 60s. Saturday through Tuesday: Dry conditions look to persist through the first half of the weekend, as the upstream cutoff low remains over the Central Rockies. Meanwhile downstream areas will continue to be influenced by an amplified ridge. Surface ridge over Ontario is progged to push a surface boundary south across Lower Michigan Saturday, which could bring slightly cooler air to Northern Illinois for Sun/Mon. Then ensembles are in good agreement with a trough sliding east across the High Plains early next week, as a large ridge develops over the Western CONUS and transitions the Great Lakes region towards a quasi northwest flow for next Tue. Beachler && .CLIMATE... Record highs and warm lows: Chicago Rockford High Low High Low Wed 9/21 92(1970) 76(1931) 94(1920) 70(1895) Thu 9/22 92(1956) 73(1895) 93(1937) 65(1959) Fri 9/23 91(1937) 71(1891) 92(1937) 66(1920) && .AVIATION... For the 00Z TAFs... Primary concern is with the potential for a round of showers and thunderstorms Wednesday morning. Despite dry and stable conditions at the surface, strong instability will form aloft over the region tonight. Clusters of TSRA are expected to develop over the Upper MS Valley tonight and then form at least a loosely organized complex that tracks east-southeast or southeast. Main uncertainty lies with whether the SHRA/TSRA move mainly across southern WI by morning, clipping far northern IL, or are able to propagate farther southeast and impact the terminals. Guidance remains somewhat split on how things evolve, keeping confidence low. Thus opted to maintain PROB30 for direct impacts. Did introduce a VCTS to the RFD TAF. Should the SHRA/TSRA do make it farther south into the area, shown on recent runs of the HRRR, then the potential also exists for a wind shift to the north- northeast, which would delay a return to the overall south- southwest regime favored tomorrow. Furthermore, cannot rule out any lingering outflow from serving as a focus for additional convection during the afternoon. This is a very low confidence scenario, so after the morning PROB30s, left the TAFs dry. With better moisture streaming northward at the surface and aloft tonight, some low clouds in the 2500-3000ft range developing overnight. MVFR BR is possible as well, though given how dry conditions are early this evening, confidence is low in occurrence and opted to pull VSBY restriction from the ORD/MDW/GYY TAFs. RC && .MARINE... 229 PM CDT High pressure centered over Southeast Ontario and the Eastern Great Lakes with a continued light gradient over much of Lake Michigan through Wednesday; however, as a low pressure develops across the Southern Plains Wed evening, a frontal boundary will be strengthening over the Northern Portions of Lake Michigan. This will bring southeast to south winds stronger over the southern half of the lake, meanwhile northeast winds increase to the north of the boundary. Current expectation is that speeds will hover between 15-20 with gusts around 25 kt. This boundary will meander from the northern half of the lake to central through Thur/early Fri, before pushing further south as a area of high pressure builds across western Ontario Fri evening. This will help to increase the gradient across the central/southern portions of the lake with southeast to south winds. Beachler && .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 Marquette MI
726 PM EDT TUE SEP 20 2016 .SHORT TERM...(This evening through Wednesday) Issued at 414 PM EDT TUE SEP 20 2016 WV imagery and RAP analysis indicated a zonal pattern across most of the nrn CONUS with a trough moving into the Pacific Northwest. A weak shortwave trough and area of 800-600 mb fgen supported some light showers or sprinkles from near KDLH into wrn Upper Michigan. Very dry air below 700 mb will limit the extent of the pcpn with only slight chance pops mentioned late this afternoon. Otherwise, mid clouds were thickening over the area with a broad area of 300-310k isentropic lift in advance of sfc low pres over South Dakota. Tonight, expect mid clouds to linger over the region in the waa pattern with the 850-700 baroclinic zone lingering over the area. Shra/tsra are expected to remain south of the cwa, closer to the 850mb front and higher MUCAPE values. Otherwise, the clouds will keep min temps mainly in the 50s. Wednesday, pcpn chances will increase from s to n as the 850 mb front gradually lifts to the north. Additional weak shortwaves in the fast zonal pattern will likely also support shra/tsra development. However, with the relatively dry low level ne flow north of the front, the pcpn into the nrn cwa will be slow with likely pops south and only chance pops north. With MUCAPE values fcst into the 500-1000 J/Kg over the far south some TS will also be possible. The thickening clouds will limit highs to the upper 60s to lower 70s. .LONG TERM...(Wednesday night through Tuesday) Issued at 311 PM EDT TUE SEP 20 2016 Still on track to see zonal flow aloft mid week transitioning to more amplified flow by this weekend as sharp ridge develops over the central Conus between upper trough over eastern Canada and trough crossing western Conus. At the sfc, a stationary front will lift across the Upper Great Lakes Wed night through Thu Night, then slowly settle south on Fri. Waves of low pressure tracking along the front will help enhance rain chances. Models have been locked on to overall scenario with pwats upward of 1.25 inches lifting into the stationary front and along/ahead of the waves of low pressure and large scale lift over entire area enhanced by right entrance region of jet over northern Ontario across Quebec and any shortwaves that will be sliding through. Heavier rain likely sets up farther south of Upper Michigan closer to main sfc front and where MLcapes over 1000 j/kg are located, but some heavy rain could affect south half of cwa as that area is on gradient of h85 theta-e. Overall there is fair agreement from the models in this scenario, though exact placement of heavier rain remains uncertain. Bigger question still remains on how quickly the front slips south of area to bring dry weather on Fri. There has been little run-to- run consistency in all models in whether front and associated showers will be south of Upper Michigan or still lingering over at least southern parts of cwa. At this time, GEM is most aggressive in hanging onto qpf while last two runs of GFS and ECMWF would point to mostly dry conditions as large Canadian high pressure builds in from Manitoba and northern Ontario. More differences for Sat as ECMWF continues to indicate qpf over far west and southwest cwa. Seems these showers are tied to shortwave/q-vector convergence and h85 frontogenesis on edge of h85 thermal ridge. Trouble is that ECMWF is not consistent with the solution as it has been back and forth on this the last couple days. Ribbon of higher h85 RH quite narrow even on the ECMWF focused over northern WI into sw Upr Michigan so think it is overdone in showing broadbrushed and light qpf across much of Upper Michigan in the 06z-18z time frame on Sat. Temps late this week probably end up near to blo normal in the low to mid 60s, coolest near Lk Superior with persistent northeast winds btwn the high pressure over northern Ontario and sfc front to the south. High pressure builds across the Great Lakes Sat and Sat night. Given such an amplified pattern aloft, the sfc high may not move out of at least eastern half of Upper Michigan until later Sun or Sun night. Though timing is not set, the approaching upper level trough and sfc trough along with low-level return flow on west side of retreating high help will bring rain back to the area. Could be dealing with moderate to heavy rain as pwats in the return flow regime are forecast to top out over 1.75 inches as deep moisture flows north off the western Gulf of Mexico. There are differences in how quickly the sfc trough and axis of higher pwat cross Upper Michigan. This is tied to how quickly shortwave trough moves across Upper Great Lakes and what extent of shortwave energy is left out across the Central Plains on Mon. Similar to late this week, run-to-run consistency on these details in the models is lacking and agreement among the models is also poor. Will keep using a consensus, which tilts slightly toward quicker GFS, until these differences can be sorted out. Though a slower solution would result in max temps Sun and possibly Mon above normal in the 70s, will keep with consensus temps mainly in the 60s due to the uncertainty in the timing for the front. Front should be east of here on Tue leaving a breezy day with some clouds and a few light showers eventually giving way to decreasing clouds as high pressure begins to build back in from the west. && .AVIATION...(For the 00Z TAFS through 00Z Wednesday evening) Issued at 725 PM EDT TUE SEP 20 2016 Although there wl be a good deal of mid clds at times, dry llvl air wl ensure VFR conditions prevail at all 3 TAF sites this fcst period. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 414 PM EDT TUE SEP 20 2016 West southwest winds to 25 knots will diminish to 20 knots or less tonight into Wed as the pres gradient weakens with the Canadian low lifting farther ne across Hudson Bay. Winds will remain blo 20 kts into Saturday under a weak pres gradient across the Upper Lakes. Southerly winds will increase Sunday to 20 knots as a low pressure trough approaches from the west. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...JLB LONG TERM...JLA AVIATION...KC MARINE...JLB
Area Forecast Discussion
National Weather Service Phoenix AZ
Issued by National Weather Service Tucson AZ 730 PM MST TUE SEP 20 2016 .SYNOPSIS... Tropical moisture continues to cover the region resulting in extensive cloud cover and some areas of light rain. This scenario will through Wednesday with slow clearing into Thursday. A strong low pressure system will develop over the Great Basin during the latter half of the week bringing cooler air over the region and just a slight chance for showers. && .DISCUSSION... WV imagery and objective analysis depicts several distinct shortwaves impacting (or about to impact) the SW conus this evening. The first such synoptic wave has lifted into northern AZ with a secondary trailing wave hovering off the srn CA coast. Lastly, the circulation of Tropical Depression Paine was creeping north up the Baja peninsula. In between all these features, much of cntrl AZ has fallen within a region of subsidence albeit with extensive daytime cloud cover which has limited instability. Some MLCape has been noted along the international border where isolated deep convection has blossomed though northward progression of echoes shows rapid deterioration into a less favorable environment. While a few showers could potentially survive into central AZ, the main focus for the remainder of the night will align with the wave lifting though SE CA. Based on radar reflectivity, HRRR trends seem a bit aggressive on shrinking areal coverage of light rain. Therefore, have kept greatest POPs through the western CWA while cutting POPs through the eastern 2/3rds slightly (towards isolated coverage). Light showers may eventually translate eastward into AZ towards Wednesday morning, though model support for more extensive coverage is still slim. Otherwise, minor adjustments were made to capture current observational trends, but nothing astounding overall. && .PREVIOUS DISCUSSION... /210 PM MST TUE SEP 20 2016/ Visible satellite imagery is reflecting copious moisture from Tropical Storm Paine moving over the region, moving towards the northeast. The western and north portions of our forecast area remain under overcast skies but we are seeing some breaks in the overcast, especially in eastern Yuma County and portions of Maricopa and Pinal counties. This could actually cause a bit of extra heating which might help promote possible shower and thunderstorm development. At this time, however, we are not seeing any lightning strikes so far so this may not come to fruition. Rainfall amounts have been mostly on the light side. The largest amounts we have seen so far have been along and near the Colorado River valley with radar estimates in the 0.6 inch range near Parker and north of Quartzsite. Still, amounts have been low enough and slow enough to not lead to any significant flooding concerns. Rain chances will continue through Thursday but slowly decreasing across the region as the remnants of the tropical storm will be swept away in as a short wave. At the same time a developing strong low pressure system will drop into the Great Basin. This will bring cool area through the area with just a slight chance of some light showers possible. Over the weekend dry air will move in. Temperatures will keep on the cool side, staying below normals for this time of year. && .AVIATION... South-Central Arizona Including KPHX, KIWA, and KSDL: Much of the night should remain dry for Phoenix area terminals, through some light showers may enter airspace Wednesday morning, then again Wednesday afternoon. Confidence is good that cigs will remain above 8-10K ft through much of the night, however there is a slim chance sct cloud bases near 6K ft could form around the area partially obscuring surrounding mountains later Wednesday morning. Otherwise, a northerly cross wind will be common through midnight before backing to a more traditional easterly direction, though speeds should remain below 12kt. Southeast California/Southwest Arizona including KIPL and KBLH: Isold/sct light showers will continue to impact much of SE CA, though much of the time frame will remain dry (especially during daylight hours Wednesday). Cigs could briefly fall towards a 6K ft level, however will hover in an 8-10K ft range for much of the period. Sfc winds will generally favor a northerly component through Wednesday morning before becoming more southerly or variable Wednesday afternoon. Aviation Discussion not updated for amended TAFs. && .FIRE WEATHER... Thursday through Monday... Much drier air will begin moving in Thursday followed by breezy winds Friday through Monday. Minimum humidity values will fall into the 10-15 percent range. Critical thresholds may be touched at times Saturday through Monday, especially across southeast California and the Lower Colorado River Valley. && .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...None. CA...None. && $$ Visit us on Facebook...Twitter...and at weather.gov/phoenix DISCUSSION...MO/Waters AVIATION...MO FIRE WEATHER...Iniguez
Area Forecast Discussion
National Weather Service Gaylord MI
255 AM EDT WED SEP 21 2016 .SHORT TERM...(Today and tonight) Issued at 255 AM EDT Wed Sep 21 2016 High pressure continues to exit east away from Michigan as a warm front/inverted trough lifts northward into the Upper Mississippi Valley and far Western Great Lakes region. Main area of convection associated with this feature is currently impacting SE Minnesota and SW Wisconsin. Another area of much weaker convection/shower activity has made some eastward progress out of the Green Bay area across Lake Michigan into our SW CWA...but is having some difficulty overcoming the dry low level air entrench over our CWA. Both MBL and FKS have reported some light rain periodically reaching the ground early this morning...but no thunder has occurred due to a serious lack of instability attm. Latest HRRR and RAP13 both depict this light precip across our SW CWA attm...while the latest NAM12 shows nothing. HRRR/RAP13 solution steadily dissipates this light precip by around sunrise early this morning...as focus for convective development remains further to the SW along the nrn periphery of the instability axis and 850 mb theta E ridge. All of the latest runs of the short term models continue to favor this area for best convective development throughout the day around the northern extent of the inverted trough. They do lift this favored are into our SW CWA later this afternoon and evening... suggesting our better chance for POPs will be during this time. MUCAPES increasing to near 2000 J/kg and 0-3 kg bulk shear values increasing to around 30 kts would also suggest a marginal risk of a few strong to possibly borderline severe storms during this time as well (in agreement with latest SPC Day 1 outlook). Have backed off just a bit on pops for much of today...opting to develop higher pops from late afternoon into tonight as better instability and moisture finally begin to push NE into our CWA along the northern edge of the inverted trough axis. Will certainly maintain the chance of thunder as well...but latest model trends have delayed the possibility for heavy rainfall until Thursday. Above normal temps will continue today despite increasing clouds...with afternoon highs ranging from the lower 70s in Eastern Upper Michigan to the mid to upper 70s across Northern Lower Michigan. Low temps tonight will cool back into the mid 50s to lower 60s. .LONG TERM...(Thursday through Tuesday) Issued at 255 AM EDT Wed Sep 21 2016 Thursday through Friday night... High impact weather potential: Embedded thunderstorms and locally heavy rain possible through Thursday evening. Pattern synopsis/Expected evolution: A strong 130+ kt northern stream jet streak is draped across southern Canada, nearly encompassing the entire width of North America. The main focus will revolve around two pieces of energy converging toward the Great Lakes region midweek. The first is expected to pinwheel from western Canada toward southern Ontario by Thursday. The second, currently ejecting from the four corners region toward northern Michigan during the same timeframe. The second wave is progged to continue to trek northeastward toward the Great Lakes, resulting in low pressure development across the central plains, bringing increased precip chances across the MS Valley and Great Lakes region Wednesday afternoon through at least the first half of Friday. Guidance continues to suggest a rather impressive baroclinic zone setting up across the northern Great Lakes into southern Ontario by Wednesday night through the end of the week into the upcoming weekend as the aforementioned weakly organized low pressure slides toward the northeast, draping a warm front across the region. As a result, potentially locally heavy rainfall will be the main concern. Thursday - Thursday night: By Thursday morning, deep layer moisture is nearing its maximum for the event across northern Michigan with PWs approaching 1.75 inches. As mentioned yesterday, if a value of 1.75 inches were to verify, it would be 1.00 inch higher than the daily mean and ~0.50 inch greater than the highest recorded PW for Sept. 22 via SPC`s sounding climatology for APX. With nearly unidirectional flow through roughly 200mb, the threat for locally heavy rainfall remains a concern. By Thursday night, surface high pressure noses into the northern Great Lakes from Canada allowing drier air to filter in and gradually diminishing precip chances from north to south late Thursday night through the first half of Friday. Friday - Friday night: Precip continues to diminish as northern Michigan lies on the southern periphery of an expansive area of high pressure centered over northern Ontario. It could end up feeling like a rather brisk fall day with occasionally gusty winds, mostly cloudy skies, and much cooler temperatures filtering into the region (high temps for many locations struggling to top the mid-60s). Saturday through Tuesday... Despite a similar flavor to the overall pattern, global model guidance varies beyond Friday night in terms of sensible weather across the area. At this point, will hedge the forecast toward the drier of the two solutions with Canadian high pressure moving very little through the end of the weekend. Toward the very tail end of the extended period, low pressure moves from the northern plains into the southern Canada resulting in increasing precipitation chances Monday night-Tuesday as a cold front swings through the Great Lakes. High temperatures in the 60s throughout the extended period, which falls within a degree or two on either side normal for the last week of September. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 1138 PM EDT Tue Sep 20 2016 VFR conditions expected with slowly lowering cigs in intial stages of top-down saturation regime (even a few light showers to impact KMBL for the next few hours). Cigs may lower enough later today to kick off some additional showers, particularly during the afternoon hours. Will tentatively cover with vcsh wording. Showers to become more numerous later this evening, although with limited cig and vis restrictions. Light winds through this taf period. && .MARINE... Issued at 255 AM EDT Wed Sep 21 2016 Winds and waves will remain below SCA criteria thru Thursday night. However...chances of showers and thunderstorms will increase today and especially tonight and Thursday as an inverted trough/warm front slowly lifts into the Western Great Lakes region. Best chance for precip will initially be over Lake Michigan today...with better chances spreading eastward tonight into Thursday. && .APX Watches/Warnings/Advisories... MI...NONE. LH...NONE. LM...NONE. LS...NONE. && $$ SHORT TERM...MLR LONG TERM...Gillen AVIATION...MSB MARINE...MLR
Area Forecast Discussion
National Weather Service Columbia SC
420 AM EDT WED SEP 21 2016 .SYNOPSIS... A surface pressure trough near the coast and upper low over the area will continue through Thursday. These features will weaken Friday with ridging more dominate Saturday. A cold front will approach from the north Sunday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Upper level low over eastern North/South Carolina this morning. Surface trough along the coast. Current radar at 08z indicating showers drifting south from the Pee Dee across the central and east Midlands. HRRR Model suggest showers may increase across the area later this morning as moisture flux and weak insentropic lift increases around 15z...so showers may spread further to the west. Increased pops during the mid morning through early afternoon....although should be a sharp moisture gradient in the west and south...so lower pops in the CSRA. Showers may decrease later this afternoon although weak to moderate instability may develop although stronger lift associated with upper level low should remain northeast of the region. Cloudiness may keep temperatures down a bit...expect temperatures a few degrees cooler than yesterday especially north. Although air mass moist with precipitable water above 2 inches in the east...guidance qpf lower than previous runs and threat for heavy rain appears diminished due to weak instability. However...if training develops a few areas could have locally higher qpf amounts mainly in the Pee Dee where lift stronger associated with upper level trough. && .SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/... The models display surface troughing near the Southeast coast with an H5 cut-off low over the area continuing through Thursday..although upper trough appears weaker over the area and moisture more shallow. Highest pops in the east...expect scattered coverage. Slightly warmer temperatures thursday with more insolation expected. Followed the consensus for the minimum temperature forecast. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... The GFS and ECMWF show the h5 low and surface trough weakening Friday. A remnant of the features linger into Saturday but ridging is shown more dominate. A backdoor cold front is forecast to move into the area Sunday or Sunday night with the front just south of the area Monday. Another front may be in the area Tuesday. The GFS has been faster with the timing of these fronts. The GFS and ECMWF MOS have pops around 20 percent Friday, less than 20 percent Saturday, and 10 to 30 percent Monday and Tuesday. The MOS indicates above normal high temperatures ahead of the cold front through Sunday lowering to about normal Monday and Tuesday. && .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/... Upper low will remain over the area through the period with restrictions possible in stratus. Upper low will remain just northeast of the TAF sites through the period with surface low pushing moisture onshore from the NC coast. This will keep showers across the area with stratus developing around daybreak through the late morning hours. Shower intensity currently not expected to be heavy enough to impact vsbys. Have remained with VCSH for the afternoon hours through the end of the period as onshore flow will continue the threat of showers...however confidence in coverage and timing remain low. Winds through the period will be northerly at 9 knots or less. EXTENDED AVIATION OUTLOOK...Restrictions possible in showers and thunderstorms as well as late night/early morning stratus and fog Thursday through Saturday. && .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. && $$
Area Forecast Discussion
National Weather Service Cheyenne WY
238 AM MDT WED SEP 21 2016 .SHORT TERM...(Today through Thursday night) Issued at 230 AM MDT Wed Sep 21 2016 Mid to high level clouds continue to stream across the southeastern half of the CWA. Although the global models do not show much precip through midday, the HRRR does show light showers in areas along the Colorado Border. Thus, maintained slight chance pops through the morning. With the dry llvls, not expecting much more than sprinkles or very light rain showers. Temps today will be 5-10 degrees cooler than Tuesday in most locations. A cold front will back into the Nebraska Panhandle overnight with widespread low clouds developing after 06-09Z over much of the Panhandle and extreme southeast WY. Put some patchy fog into the northern Nebraska Panhandle with upslope northeasterly sfc winds along the Pine Ridge. Low clouds will be persistent across portions of the plains through the morning on Thursday. The coolest highs (mid to upper 60s) will be over the northern Nebraska Panhandle where some low clouds could persist through the entire aftn. South to southeasterly winds will become breezy by the aftn and early evening over much of the CWA. Kept 20-40 percent pops mostly confined to areas west of the Laramie Range through the aftn as the atmosphere will be capped/stable over the plains. Could see a slightly better coverage of showers and isolated tstms into Thursday night as the better forcing ahead of the upper trough arrives. Another round of stratus over the Panhandle is expected by Thursday night. .LONG TERM...(Friday through Tuesday) Issued at 230 AM MDT Wed Sep 21 2016 Unsettled in the long term as low pressure tracks across the area. Best chances for rain will be Friday and Saturday as the low tracks across the area. By Saturday evening, the low will be east of us in North Dakota with chances for precip ending. It will be cold Sunday as 700mb temperatures fall to -4C across the area. May not get out of the 50s for highs for many areas with low temperatures in the 30s for many areas. Warmer weather returning for the beginning of next work week. Forecast looks dry as high pressure builds back into the area. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 1105 PM MDT Tue Sep 20 2016 VFR conditions for the most part. Could start seeing lowering conditions in the northern Panhandle but confidence is not high. Will wait and see what happens overnight. && .FIRE WEATHER... Issued at 230 AM MDT Wed Sep 21 2016 No fire weather concerns through the end of the week. Temperatures will cool over the next few days, and especially after Friday behind a cold front. Minimum afternoon humidity values will fall into the 20-30 percent range this afternoon. Further moistening will occur on Thursday and Friday along with an increasing chance of showers across portions of the region. && .CYS Watches/Warnings/Advisories... WY...None. NE...None. && $$ SHORT TERM...ZF LONG TERM...GCC AVIATION...GCC FIRE WEATHER...ZF
Area Forecast Discussion
National Weather Service Marquette MI
518 AM EDT WED SEP 21 2016 .SHORT TERM...(Today and tonight) Issued at 515 AM EDT WED SEP 21 2016 WV imagery and RAP analysis indicated a zonal pattern across most of the nrn CONUS with the exception of a trough digging into the Pacific Northwest. A shortwave riding along the 850 mb warm frontal boundary and instability/strong moisture transport gradient at nose of 30-35 kt 850 mb jet max has supported strong to severe t-storms over western and central WI early this morning. Some stray showers from this convective complex have made it into far south central Upper Mi with MNM reporting some sprinkles/light showers last evening into early this morning. Another weak shortwave rounding the broad mid-upper level ridge has triggered a few t-storms over ern MT and wrn ND. With the exception of the light -shra over the scntrl, the rest of Upper Mi has remained dry early this morning under influence of a sfc high pressure ridge over the area. Very dry airmass over our area reflected in 00z APX and INL soundings with very dry air noted from sfc up above 700 mb, and this will need to be overcome before pcpn can occur over Upper Mi today and tonight. Mid and high clouds have kept overnight temps warmer than last night, generally in the mid 50s to lower 60s. Today and tonight, Shortwave rounding the ridge over the Northern Plains will work its way into the Upper Great Lakes this afternoon. Models do show a corresponding increase in 305K isentropic ascent and 850 mb moisture transport with gradual northward movement of the 850 mb warm front in response to the shortwave passage, especially late in the afternoon into tonight which will likely support shower development. However, with the relatively dry ne flow developing north of the warm front below 850 mb, models (particularly the high- res models) are trending slower with the northward advance of developing pcpn and showing a sharper cut-off to pcpn over the nrn sections of Upper Mi deeper into the dry air. As a result have confined slight chc to low chc pops over the scntrl and wi border counties this morning with a gradual increase in pops toward the ne by late afternoon/evening. By late evening/overnight tonight generally have likely to categorical pops over the south half of the cwa with chc pops for the north half. Wouldn`t be surprised if the Keweenaw Peninsula stayed mostly dry through period as some of the models suggest as they will be farthest away from better convergence/isentropic ascent along 850 mb warm frontal boundary and from better 850 mb moisture transport. With MUCAPE values fcst into the 500-1000 J/Kg over the far south late afternoon into this evening some TS will also be possible and possibly a strong storm or two with up to dime-sized hail given strong deep layer shear present. The thickening clouds and developing ne low-lvl flow will limit highs today to the mid 60s to lower 70s, warmest south and east. Lows tonight will generally be in the 50s under persistent cloud cover. .LONG TERM...(Thursday through Tuesday) Issued at 432 AM EDT WED SEP 21 2016 An increasingly amplified pattern is still on track to develop across N America for the remainder of this week into the weekend. Ridge/positive height anomaly currently moving into nw Canada will strengthen as it shifts across the Northwest Territories to Nunavut by the end of the week. The magnitude of the positive height anomaly at 500mb will reach 3 standard deviations above the long term late Sept avg. To the s of this anomaly, a trof will amplify over the western CONUS over the next few days, and the building downstream ridge over the central CONUS will then link up with the n central Canada positive height anomaly, leading to a sharp mid continent ridge for a brief time. In response, trof over se Canada will deepen and expand into the ne CONUS this weekend. This suggests that after wet weather into Thu, a drier period should mostly dominate Fri/Sat and potentially thru Sun as sfc high pres associated with the sharp upstream ridge builds se into northern Ontario and the Upper Great Lakes. Early next week, a more progressive flow regime should begin to take shape again. Initially, building of a ridge into western N America will send a shortwave se into the Upper Lakes later Mon/Tue. This wave will incorporate at least some of the energy in the western CONUS trof with the remainder dropping s. A period of shra will accompany this shortwave across the area at some point Sun/Mon with drying following for Tue. As for temps, readings will probably not stray far from late Sept normals during this period. Beginning Thu, last in a string of weak shortwave energy lifting ne thru the western Great Lakes will move e of the area by late aftn. Meanwhile, downstream of the western Canada ridge, a stronger shortwave will drop into northern Ontario during the day and then into Quebec Thu night. Following this wave, sfc high pres associated with the sharpening mid/upper ridge in central Canada will build se into northern Ontario Thu night, pushing frontal boundary extending from the Plains to the Great Lakes southward. As a result, expect a trend for shra Thu morning to diminish and/or end from nw to se during the aftn thru Thu night. With sfc high pres dominating northern Ontario on Fri and frontal boundary/baroclinic zone shifted farther s and sw, expect a dry day. Will need to watch development of pcpn into the northern plains where strengthening southerly flow/isentropic ascent ahead of western CONUS trof leads to an expanding pcpn area. Right entrance upper divergence with a reoriented upper jet in a nw-se direction across northern Ontario to New England could aid the expansion of pcpn toward Upper MI late Fri or Fri night. ECMWF has been most insistent on pcpn briefly streaking se into at least western Upper MI Fri night into Sat underneath right entrance of upper jet and within an eastward extension of isentropic ascent from the northern Plains. GFS/CMC have been more varied on whether or not the pcpn will reach the area, but since majority of GFS/CMC ensembles support the streak of pcpn, fcst will reflect chc pops spreading into the far w Fri night and expanding e into central Upper MI Sat morning before pcpn area dissipates. Fcst for Sun thru Tue is highly uncertain, much more than is typically the case at this time range and no different from the last few days. Over the last 4 days, medium range guidance has shown considerable spread in what happens with the western CONUS trof and how the flow evolves across southern Canada this weekend thru early next week. The 00z GFS is back to showing a mid level low closing off over the Upper Mississippi Valley/western Great Lakes early next week, a solution that appeared once days ago though it got to that solution in a different manner. At this point, consensus of recent days guidance is for a shortwave which incorporates at least some of the energy in the western CONUS trof to reach the area early next week, but wouldn`t be surprised at all if something completely different occurs. Maintaining some continuity with previous fcst, will show chc pops spreading slowly e across the area Sun/Sun night, lingering Mon then trending dry on Tue. && .AVIATION...(For the 06Z TAFS through 06Z Wednesday night) Issued at 153 AM EDT WED SEP 21 2016 Although there wl be a good deal of mid clds at times and perhaps a few -shra especially this aftn, dry llvl air wl ensure VFR conditions prevail at all 3 TAF sites this fcst period. Thicker clds and more numerous showers will arrive by this evng. While lingering near sfc dry air wl likely maintain VFR conditions even if some showers occur, MVFR conditions wl probably dvlp after 22/06Z. && .MARINE...(For the 4 AM Lake Superior forecast issuance) Issued at 515 AM EDT WED SEP 21 2016 Developing ne flow over Lake Superior with sfc trough moving into Upper Mi and sfc ridge over Ontario could support some higher wind gusts to 25 knots over the wrn half of the lake this afternoon into Thu and across the entire lake Thu night into Fri. As the Canadian high builds more over the Upper Lakes winds will dip blo 20 kts Friday night into Saturday night. Southerly winds will increase late Sunday into Sunday night to 25 to 30 knots over mainly the north central and eastern part of the lake as a low pressure trough approaches from the west. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...Voss LONG TERM...Rolfson AVIATION...KC MARINE...Voss
Area Forecast Discussion
National Weather Service Omaha/Valley NE
339 AM CDT WED SEP 21 2016 .SHORT TERM...(today through Friday) Issued at 330 AM CDT WED SEP 21 2016 Thunderstorm chances this afternoon through Thursday are the primary forecast concerns this period. Warm temperatures to continue as well. Upper flow pattern was beginning its change as strong westerlies across the Northern Plains were progressing east as strong low/trough dropped into the Pacific Northwest early Wednesday. Southwest mid level flow will remain over the Central Plains through tonight, then shortwave ridging will build into our region later Thursday into Friday. Shortwave within southwest flow aloft is shown currently by RAP analysis moving through eastern Colorado, heading toward Nebraska and Iowa later today and tonight. Meanwhile quasi- stationary surface front extended from northeast Colorado into southeast South Dakota and western Wisconsin. This boundary will not move a whole lot much of the day as upper flow parallels front, waiting for surface low tied to upper shortwave to develop and move from central Nebraska into northern Iowa this evening. Increased low level convergence ahead of the low will help ignite storms this afternoon, then southward drift of front will occur in its wake helped along by convection. Expect storms to take some time to get going later today as inhibition is slowly eroded and where low level convergence is maximized in northeast Nebraska and southeast South Dakota ahead of surface low. Instability increases markedly from near 1500 j/kg of MLCAPE in northeast Nebraska to closer to 2500 j/kg in northwest Iowa as per GFS, so we may miss initial development northeast of our area around 00Z. As the evening progresses, southward drift of surface front behind low combined with increasing moisture transport over that boundary as low level jet kicks up will bring our best chance for convection. Appears the best conjunction of those parameters will lie somewhere between Columbus and Norfolk, northeast to between Wayne and Tekamah, and into Monona County Iowa. Expect storms to fire somewhere in this zone by 03Z, then expand east and west with time. Continued moisture feed into south and southwest flank will lead to some propagation southward toward Interstate 80 overnight, but storms south of the Interstate may be hard to come by. Certainly could see severe storms given degree of instability but overall bulk shear is modest at best. Storms becoming more outflow dominant and loaded with precipitation suggests damaging wind gusts or microbursts are possible as well. Heavy rain is also likely given high precipitable water values near 1.75 inches shown by GFS, and potential for training storms. Bulk of overnight activity will be pushing off to the east Thursday morning. Overall mid level pattern of building shortwave ridge across our area will support northward propagation of frontal boundary, but will not clear our northern border until later Thursday night. Thus redevelopment of convection appears likely Thursday afternoon where models support 2000 j/kg of ML and SB CAPE and Bulk Shear is near 30kt. By Friday morning building heights and front lifting north should leave most of eastern Nebraska and western Iowa under capping mid level temperatures. Surface temperatures should reach the upper 80s again most spots Friday afternoon. In fact much of eastern Nebraska and western Iowa will average mid and upper 80s for highs each afternoon today through Friday. While highs Tuesday reached the 90s all areas, more cloud cover today will likely hold temps down a tad, though areas along and south of Interstate 80 could top 90 again. And Thursday afternoon northeast Nebraska will be north of retreating front and may not reach 80 in some areas. .LONG TERM...(Friday night through Tuesday) Issued at 330 AM CDT WED SEP 21 2016 GFS and ECMWF are fairly consistent in showing upper low rotating into the Northern Plains on Saturday with trough axis extending into New Mexico. They are also fairly close in depicting plume of tropical moisture streaming into our region Saturday then being shoved east by Sunday evening. Those models then diverge quite a bit beyond that, with GFS offering a deep closed cyclone over Wisconsin solution by Tuesday, and ECMWF maintaining general trough over our region. As far as sensible weather in concerned, we will be on the cool side of the system with pockets of cold air aloft rotating across the region. Some of these may spark some showers from time to time, but the main weather story appears to be temperatures in the 60s or lower 70s for highs to start next week. Leading up to that, we will see periods of showers and thunderstorms Saturday into Sunday when moisture plume is on top of us. GFS again is painting precipitable water values of 1.75-2.00 inches across our area Saturday. Thus heavy rain remains a concern Saturday and Saturday night before bulk of activity pushes off to the east. && .AVIATION...(06Z TAFS for KOFK...KLNK and KOMA.) Issued at 1215 AM CDT WED SEP 21 2016 High-level clouds will continue to spread east ahead of a low- amplitude short-wave trough moving into the central Rockies. Meanwhile, a nocturnal LLJ will strengthen through daybreak Wednesday from the southern High Plains to mid Missouri Valley, yielding LLWS through about 14z Wednesday at all three TAF sites. Gusty south winds will once again materialize by Wednesday afternoon ahead of a surface low developing from central into northeast Nebraska. By Wednesday evening, the chance of thunderstorms will increase at across eastern Nebraska. && .OAX Watches/Warnings/Advisories... NE...None. IA...None. && $$ SHORT TERM...Dergan LONG TERM...Dergan AVIATION...Mead
Area Forecast Discussion
National Weather Service Pocatello ID
305 AM MDT WED SEP 21 2016 .DISCUSSION...Moisture from a few different sources will work its way into our region today, tomorrow and Friday. Moisture from a shortwave trough is currently the dominant feature over our area, and is providing isolated showers over Nevada. Additional moisture includes tropical moisture and remnants from what was once Hurricane Paine in the Eastern Pacific Ocean. Our widespread rain/snow event will begin today with isolated and scattered rain showers over the central mountains with increasing coverage by the afternoon. Rainfall amounts will top out around 1/4 inch in these areas for today, with 1 to 2 inches of snowfall at highest elevations (of which is expected to increase to 2 to 4 inches through Friday). For the Snake Plain areas and elsewhere, coverage will increase greatly later this afternoon with lighter rainfall amounts expected. Instability will be marginal this afternoon but the greatest likelihood for thunderstorms looks to be over the Eastern and Caribou Highland locations with a similar pattern setting up for Thursday afternoon. As we go into the overnight hours, rainfall will shift focus a bit to the east and south where a decent chance, about 50%, to obtain 1/4 inch of rainfall exists across the Southern Highlands. Thursday morning shows another 50% chance for 1/4 inch of rainfall in portions of the Southern Highlands, especially across the southern Caribou-Targhee NF. For the rest of Thursday, look for continued rain showers with a chance for thunderstorms with increased coverage expected overnight into Friday morning. Overall, for our area, highest rainfall accumulations look to be setting up along the Idaho/Utah border including the cities of Preston, Mink Creek, Malad City, Soda Springs. Rainfall amounts will continue to be amended as rain begins to fall and the event unfolds. Right now forecasts are calling for 2 to 4 inches across this area over a 3-day period starting this afternoon. Snow may fall at highest elevations in these areas as well Thursday with 1 to 3 inches possible through Friday. Other areas in Southeast Idaho will see 1 to 2 inches of rainfall but we are pretty confident everyone in the region will see a drop or two of rainfall over this event. A rather drastic temperature drop will occur Thursday and continue into Friday. Be in store for 10 for 15 degree cooler high temperatures tomorrow and an additional 5 to 10 degrees cooler on Friday. Gradual recovery will occur over the weekend and next week as high pressure builds into our region and the low exits to the east. Lingering showers are forecast Saturday for the Eastern Highland locations before ending Sunday. NP/RS && .AVIATION...There is some convection developing in Nevada this morning which the HRRR would move into KSUN around 14z this morning and KBYI about 16Z. Less confidence in timing at KPIH but little embedded bands in satellite imagery are moving east pretty quick, gave the NAM the benefit of doubt. Moisture deepens and ceilings lower quickly to MVFR tonight 05-07z time period for TAF sites along the Snake Plain with the first lobe off the H7 low. There may be a little period early morning with lighter rain, then the next band develops mid to late morning with a second lobe coming up, followed by a third Thursday afternoon. RS && .FIRE WEATHER...Strong low pressure system is entering the Oregon coast this morning and will track through north Nevada/Utah, then NE into Wyoming. Isolated thunderstorms are expected this afternoon and again on Thursday. The central mountains and Caribou should be favored, but with the system moving across this area, forecast is generally broad brushed with the potential. Models are consistent with timing of heavier rain developing this evening and the pattern remaining quite unsettled through about noon Saturday. Moderate to heavy rain expected for all of Thursday and most of Friday. Widespread 1 to 2 inches of rain is expected over the Wed night to Sat afternoon time period and may be locally higher in the mountains. RS && .PIH Watches/Warnings/Advisories... None. && $$
Area Forecast Discussion
National Weather Service Tucson AZ
905 PM MST TUE SEP 20 2016 .SYNOPSIS...There is a chance of showers with a few thunderstorms through Wednesday. A drying trend will begin Thursday and continue into this weekend. However, a low pressure system over the southern Rockies may generate a few showers and thunderstorms mainly east of Tucson. Cooler temperatures will also occur this weekend. && .DISCUSSION...Isolated showers and thunderstorms were moving northward across the Tohono O`odham Nation west of Tucson at this time. This area of showers and thunderstorms associated with a perturbation moving northeastward into the area from northwest Sonora as per water vapor satellite imagery has decreased in coverage and intensity during the past hour. Otherwise, dry conditions prevailed elsewhere this evening under mostly clear skies to mostly cloudy skies. The main forecast challenge into Wednesday is regarding precip potential, and forecast confidence is not the highest due to some recent hi-res model solutions. Have noted that HRRR solutions during the past several hours depicted no rainfall west of Tucson this evening, which was clearly not reality. For example, the Sells RAWS has recorded 0.33 inch of rain since mid-afternoon. The AWIPS version of the NAM12 also depicted no measurable rainfall thru midnight. Have put slightly more credence in the 21/00Z Univ of AZ WRF-NAM that does depict some measurable rainfall to occur west of Tucson later tonight. At any rate, given at least a marginally unstable environment as per the 21/00Z KTWC sounding (MUCAPE of 484 J/kg) and similar values as via the SPC Mesoscale Analysis, have maintained at least a slight chance of showers and isolated thunderstorms the rest of tonight. A chance of showers and isolated thunderstorms exists Wed especially east of Tucson. This scenario is similar to the Univ of AZ WRF-NAM and to some extent the NAM12. High temps Wed will be quite similar to temps achieved this afternoon, or perhaps a few degs warmer depending upon location. Please refer to the additional sections for further detail. && .AVIATION...Valid through 22/06Z. Scattered -SHRA and isolated -TSRA with cloud decks generally from 8k-12k ft msl into Wednesday evening. Surface wind will be variable in direction mostly less than 12 kts. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...There is a chance of showers and isolated thunderstorms through Wednesday. A drying trend will start Thursday and continue into this weekend. However, moisture will be sufficient for a slight chance of showers and thunderstorms east of Tucson. 20- foot winds will be mainly terrain driven less than 15 mph through Wednesday, then west to southwest breezes to occur Thursday and Friday afternoons. && .PREV DISCUSSION /210 PM MST/...Water vapor imagery continues to show high pressure well to our east and is now over west Texas, with the ridge extending northeast into northern Texas and southwest Oklahoma. Meanwhile, a weak trough resides just off the southern California coast. Tropical storm Paine continues to move up the west coast of the Baja peninsula and is expected to continue to weaken as it eventually is expected to move inland across the north central Baja peninsula by late Wednesday afternoon as a remnant low, based on the latest official track/forecast from the NHC, which was issued at 8 AM PDT. IR satellite imagery shows extensive cloudiness across much of the Desert Southwest, although the most enhanced cloudiness is currently over southern Utah, northern Arizona and into southern California. Taking a look at radars from KIWA, KEMX and KYUX indicate that the bulk of the showers extend from coastal areas of southern California into west central Arizona and towards the Flagstaff area. There are some showers extending a bit farther south across the southwestern deserts between Gila Bend and and Yuma, but all of this activity is moving generally north. That said, it is looking like we will struggle to see even scattered type POPs for my forecast area for the remainder of this afternoon and perhaps even into the late evening as the focus currently remains well to the west and north of my forecast area. However, there is some enhancement in IR imagery well to the northeast of Paine over the north central Baja peninsula and the northern Gulf of California. With plenty of moisture to our south we should eventually see shower development, but I pushed it back to mainly after midnight tonight. Even then, think we will only see isolated to low end scattered activity during that time, so the bulk of shower activity for my forecast area should occur overnight tonight and during the day Wednesday as the weak trough moves through Arizona. Once the remnants of Paine become absorbed into the weak trough and eject northeast Wednesday, another upstream major trough will be over the Pacific Northwest and will dive into the Great Basin by late Thursday. As a result, expect a lingering threat for mostly isolated showers and thunderstorms for deserts/valleys and low end scattered type POPs for mountains on Thursday. By late in the day Friday this system is progged to be over the central Rockies, with the tail end of this system into northern Arizona. So, expect slight chance of showers/thunderstorms continuing Friday. By Saturday the low should be in the general vicinity of the four corners or northern New Mexico with enough dry air punching in behind it for a dry forecast. However, beyond Saturday the models begin to show significant differences, such that the GFS is quite wet just to our east and along the New Mexico border whereas the ECMWF has the trough/low farther south and east, instead of a closed low over Arizona. For now I kept or included a chance of showers and thunderstorms along the border with New Mexico for Sunday into early next week. For Tucson, high temperatures will be near normal for Wednesday and Thursday, then 5 to 7 degs below normal each day thereafter. Low temps will be 2 to 4 degs above normal, although the warmest morning will be tonight/Wednesday morning. For Saturday through Tuesday mornings, lows will range from 4 to 6 degs below normal. && .TWC WATCHES/WARNINGS/ADVISORIES...None. && $$ Visit us on Facebook...Twitter...YouTube...and at weather.gov/Tucson
Area Forecast Discussion
National Weather Service Las Vegas NV
927 PM PDT TUE SEP 20 2016 .SYNOPSIS...Weather will remain cool and unsettled through the end of the week as remnant tropical moisture interacts with a trough pushing in from the west. As the trough moves in Thursday...increasing winds and the arrival of drier air will aid in dangerous fire conditions for some areas along with strong Thunderstorms in Northwest Arizona and eastern Nevada. Temperatures will remain cool through Friday before returning to near normal over the weekend. && .UPDATE...The remains of the weak circulation center from what was once a southern California upper low was moving across southern Nevada this evening. The inland progression of this feature has helped enhance a band of light to moderate rain showers extending from near Twentynine Palms up to southern Clark County. Precipitation amounts were generally less than 0.10". The latest HRRR composite reflectivity forecast indicates the potential for isolated to scattered light showers extending up across Lake Mead into northern Mohave County. We could still see a few sprinkles in the Las Vegas Valley before midnight. However...it will be most favorable for measurable rain generally from I-40 southward. The PoP/WX grids were updated to reflect the latest trends and remove the general mention of thunderstorms through Wednesday morning. -Adair && .PREV DISCUSSION... 220 PM PDT TUE SEP 20 2016 SHORT TERM...Through Tonight. Three systems are currently affecting the southwestern U.S. The first is the rapidly dying Tropical Cyclone (TC) Paine, with moisture from it streaming well north of its center west of the Baja Peninsula. The second is an upper-level low slowly moving northeastward onto the Pacific Coast near San Diego. The third is an elongated vorticity maximum to the northeast of this upper low stretching from San Bernardino County northeast to southern Utah and southwest Colorado. Much of the precipitation in our CWA today has been associated with this elongated vort max, aided by the moist advection from TC Paine. However, this afternoon, precipitation has developed/increased in intensity in closer proximity to the upper low near San Diego. A quasi-zonally oriented band of rain showers has developed in southwest Mohave County and southern San Bernardino County in advance of this upper low. Precipitation rates have increased somewhat within this band. The HRRR has not handled this band particularly well this afternoon. Only recently has it caught onto the idea of its persistence/somewhat stronger intensity, and it continues to waver on its evolution through this evening. The latest run shows more convective-type showers continuing northeastward through southern Mohave County through 00Z Wednesday before rapidly progressing out of the area. Meanwhile, the western portion of the band remains anchored to the San Bernardino Mountains and Coachella Valley before rapidly progressing northeastward and diminishing somewhat in association with the track of the upper low. This seems to be a reasonable solution given the proximity to the two vort maxima; however, given the variability seen with this evolution simulation to simulation -- not overly confident of this. PoPs were tweaked but remain consistent with this morning`s update, in general. Think outside of a few sprinkles, the Las Vegas Valley will probably not see rain, so kept PoPs confined to south/east of I- 15 through the night. Most of the heavier precip in Mohave County should end by midnight with lighter showers possible thereafter. Instability has been meager to nonexistent today, so even an isolated lightning strike is not particularly likely. Nevertheless, the increasing precipitation intensities this afternoon and the stronger lift associated with the passing upper low led me to keep slight thunder chances in through the night. && LONG TERM...Wednesday through Monday. Remnant moisture from Tropical depression Paine will remain in play across the region on Wednesday beneath a broad southwesterly flow aloft. Some cooling aloft and slightly greater sunshine potential should allow for some marginal destabilization tomorrow afternoon which will support the probability of greater thunderstorm coverage across the region tomorrow as opposed to the more stratiform precipitation event we are observing today. However, instability will still not be very impressive and the greatest chance for thunderstorms will be across the great Basin closer to the approaching trough...and across Northwest Arizona. On Thursday, a strong and dynamic trough will push into the Great Basin region with the base of the trough dragging across our forecast area. The impacts with this system will be two fold, strong winds and fire danger will be one concern. While Heavy rain and thunderstorm potential will be another concern. As far as wind and fire goes, a dry slot in the lower levels and subsidence on the back side of the trough will promote strong drying and downward momentum transport to support widespread winds across much of the Mojave Desert and low relative humidity values. Winds may require their own headlines in subsequent updates but felt confident enough in the fire danger to go out with a fire weather watch for much of San Bernardino county and Clark County, as well as the Colorado River for Thursday afternoon. We may see wind gusts exceeding 40 mph across much of the same areas during this time. As usual with wind events, blowing dust can be expected as the winds pick up during the day Thursday. Meanwhile....across Northwest Arizona and mainly eastern Lincoln county, strong thunderstorms will be a possibility on the west edge of remnant moisture and instability from Paine. Southwesterly shear will be quite impressive with over 65kts of shear forecast at 500mb and a fairly unidirectional profile. This would favor both strong convection as well as training convection ahead of the trough. Some models are suggesting the potential for fairly significant QPF across northern Mohave county Thursday afternoon so flash flood potential will need to be monitored as the event approaches. Conditions will improve Friday as the trough pushes eastward and high pressure attempts to build back in but temperatures will remain cool...averaging 10 to 15 degrees below normal. Less confidence in the longer range period extending from this weekend into next week as the ECMWF builds a large ridge into the region while the GFS retrogrades some trough energy into Arizona which would keep us cooler with possible north winds especially down the Colorado River. For now maintained a dry forecast with temperatures gradually returning to near normal. && .FIRE WEATHER...Strong winds and low humidity will combine forces to create a period of critical fire weather conditions Thursday afternoon. Fuels remain very dry especially north of I-40 which will see little benefit from the remnant moisture of tropical depression Paine. Fire weather watches are in effect for the San Bernardino County deserts, much of the lower elevations of Clark County, the lower Colorado River valley and Lake Mead NRA. Improving conditions are expected friday as the winds relax. && .AVIATION...For McCarran...Winds will be light and diurnally driven overnight and Wednesday morning until stronger SW winds kick in by late Wednesday afternoon. A slight chance of storms tomorrow afternoon/evening. For the rest of southern Nevada...northwest Arizona...and southeast California...Showers and ceilings near/below 10 kft will continue this evening for eastern San Bernardino and southern/eastern Mohave Counties. Some ceiling improvement is expected by late tonight. Scattered showers and mountain obscurations are possible in the Sierra this evening. Winds look to be predominantly S/SE through tomorrow morning, with speeds generally below 12 kts. Chances of storms exist tomorrow afternoon, especially near higher terrain, with stronger S/SW winds commencing by late afternoon. && .SPOTTER INFORMATION STATEMENT...Shower and thunderstorm chances continue through Thursday. Strong winds are also expected in much of the area Thursday afternoon and evening. Spotter activation may be required Wednesday afternoon through Thursday. && $$ Short Term/Aviation...Shafer Long Term/Fire Weather...Outler For more forecast information...see us on our webpage: http://weather.gov/lasvegas or follow us on Facebook and Twitter
Area Forecast Discussion
National Weather Service Gaylord MI
1055 AM EDT WED SEP 21 2016 .UPDATE... Issued at 1055 AM EDT Wed Sep 21 2016 Overview: Surface low pressure analyzed over the central plains with a warm front arcing across southern Minnesota then down into the lower lakes region. EML/plume of very steep mid level lapse rates (pushing 8C/KM) stretches from the central plains and just into the northern plains and upper Mississippi River Valley. Strong low level moisture transport/pooling along and south of the front has pushed dewpoints into the 70s across parts of the Midwest and a few thousand J/KG of MLCAPE. Instability decreases rapidly heading into northern Michigan with just a few hundred J/KG MUCAPE poking into the far S/SW counties. Ongoing MCS/squall line that developed in srn Minnesota overnight now diving ESE through lower Michigan with the northern fringe of a well defined MCV skirting the M-55 corridor. But heart of convection is diving S/E away from this CWA along the aforementioned instability gradient. Another batch of showers/storms has developed over srn Wisconsin but will also stay well south of our area. Rest of today and tonight: Northern Michigan once again sitting in "no mans land" with ongoing convection to the south and lighter precip ongoing across the far northern plains along tight baroclinic zone on the southern side of the upper jet. Upstream warm front will very slowly lift northward through tonight with moisture/instability plume slowly nosing into the region. But by far, best moisture/instability and low level convergence remains to our west. There will be renewed showers/storms across the upper Mississippi River Valley later today through tonight that will eventually get into our area. But that`s several hours away. So, after this mornings precip, have diminished pops for the afternoon into early evening and reworked the Hazardous Weather Outlook. && .SHORT TERM...(Today and tonight) Issued at 255 AM EDT Wed Sep 21 2016 High pressure continues to exit east away from Michigan as a warm front/inverted trough lifts northward into the Upper Mississippi Valley and far Western Great Lakes region. Main area of convection associated with this feature is currently impacting SE Minnesota and SW Wisconsin. Another area of much weaker convection/shower activity has made some eastward progress out of the Green Bay area across Lake Michigan into our SW CWA...but is having some difficulty overcoming the dry low level air entrench over our CWA. Both MBL and FKS have reported some light rain periodically reaching the ground early this morning...but no thunder has occurred due to a serious lack of instability attm. Latest HRRR and RAP13 both depict this light precip across our SW CWA attm...while the latest NAM12 shows nothing. HRRR/RAP13 solution steadily dissipates this light precip by around sunrise early this morning...as focus for convective development remains further to the SW along the nrn periphery of the instability axis and 850 mb theta E ridge. All of the latest runs of the short term models continue to favor this area for best convective development throughout the day around the northern extent of the inverted trough. They do lift this favored are into our SW CWA later this afternoon and evening... suggesting our better chance for POPs will be during this time. MUCAPES increasing to near 2000 J/kg and 0-3 kg bulk shear values increasing to around 30 kts would also suggest a marginal risk of a few strong to possibly borderline severe storms during this time as well (in agreement with latest SPC Day 1 outlook). Have backed off just a bit on pops for much of today...opting to develop higher pops from late afternoon into tonight as better instability and moisture finally begin to push NE into our CWA along the northern edge of the inverted trough axis. Will certainly maintain the chance of thunder as well...but latest model trends have delayed the possibility for heavy rainfall until Thursday. Above normal temps will continue today despite increasing clouds...with afternoon highs ranging from the lower 70s in Eastern Upper Michigan to the mid to upper 70s across Northern Lower Michigan. Low temps tonight will cool back into the mid 50s to lower 60s. .LONG TERM...(Thursday through Tuesday) Issued at 255 AM EDT Wed Sep 21 2016 Thursday through Friday night... High impact weather potential: Embedded thunderstorms and locally heavy rain possible through Thursday evening. Pattern synopsis/Expected evolution: A strong 130+ kt northern stream jet streak is draped across southern Canada, nearly encompassing the entire width of North America. The main focus will revolve around two pieces of energy converging toward the Great Lakes region midweek. The first is expected to pinwheel from western Canada toward southern Ontario by Thursday. The second, currently ejecting from the four corners region toward northern Michigan during the same timeframe. The second wave is progged to continue to trek northeastward toward the Great Lakes, resulting in low pressure development across the central plains, bringing increased precip chances across the MS Valley and Great Lakes region Wednesday afternoon through at least the first half of Friday. Guidance continues to suggest a rather impressive baroclinic zone setting up across the northern Great Lakes into southern Ontario by Wednesday night through the end of the week into the upcoming weekend as the aforementioned weakly organized low pressure slides toward the northeast, draping a warm front across the region. As a result, potentially locally heavy rainfall will be the main concern. Thursday - Thursday night: By Thursday morning, deep layer moisture is nearing its maximum for the event across northern Michigan with PWs approaching 1.75 inches. As mentioned yesterday, if a value of 1.75 inches were to verify, it would be 1.00 inch higher than the daily mean and ~0.50 inch greater than the highest recorded PW for Sept. 22 via SPC`s sounding climatology for APX. With nearly unidirectional flow through roughly 200mb, the threat for locally heavy rainfall remains a concern. By Thursday night, surface high pressure noses into the northern Great Lakes from Canada allowing drier air to filter in and gradually diminishing precip chances from north to south late Thursday night through the first half of Friday. Friday - Friday night: Precip continues to diminish as northern Michigan lies on the southern periphery of an expansive area of high pressure centered over northern Ontario. It could end up feeling like a rather brisk fall day with occasionally gusty winds, mostly cloudy skies, and much cooler temperatures filtering into the region (high temps for many locations struggling to top the mid-60s). Saturday through Tuesday... Despite a similar flavor to the overall pattern, global model guidance varies beyond Friday night in terms of sensible weather across the area. At this point, will hedge the forecast toward the drier of the two solutions with Canadian high pressure moving very little through the end of the weekend. Toward the very tail end of the extended period, low pressure moves from the northern plains into the southern Canada resulting in increasing precipitation chances Monday night-Tuesday as a cold front swings through the Great Lakes. High temperatures in the 60s throughout the extended period, which falls within a degree or two on either side normal for the last week of September. && .AVIATION...(For the 12Z TAFS through 12Z Thursday morning) Issued at 645 AM EDT Wed Sep 21 2016 Chances of showers and thunderstorms will slowly increase from west to east today and tonight as a warm front/inverted trough and associated instability and deep moisture gradually edge into Lower Michigan over the next 24 hrs. Low levels remain rather dry...so this process will take some time. Overall conditions will remain VFR despite increasing chances of precip...but cigs and vsbys will temporarily decrease to MVFR/possibly IFR within heavier showers and storms. Overall wind regime will remain light...lending to lake breeze development this afternoon. && .MARINE... Issued at 255 AM EDT Wed Sep 21 2016 Winds and waves will remain below SCA criteria thru Thursday night. However...chances of showers and thunderstorms will increase today and especially tonight and Thursday as an inverted trough/warm front slowly lifts into the Western Great Lakes region. Best chance for precip will initially be over Lake Michigan today...with better chances spreading eastward tonight into Thursday. && .APX Watches/Warnings/Advisories... MI...NONE. LH...NONE. LM...NONE. LS...NONE. && $$ UPDATE...Adam SHORT TERM...MLR LONG TERM...Gillen AVIATION...MLR MARINE...MLR
Area Forecast Discussion
National Weather Service Cheyenne WY
506 AM MDT WED SEP 21 2016 .SHORT TERM...(Today through Thursday night) Issued at 230 AM MDT Wed Sep 21 2016 Mid to high level clouds continue to stream across the southeastern half of the CWA. Although the global models do not show much precip through midday, the HRRR does show light showers in areas along the Colorado Border. Thus, maintained slight chance pops through the morning. With the dry llvls, not expecting much more than sprinkles or very light rain showers. Temps today will be 5-10 degrees cooler than Tuesday in most locations. A cold front will back into the Nebraska Panhandle overnight with widespread low clouds developing after 06-09Z over much of the Panhandle and extreme southeast WY. Put some patchy fog into the northern Nebraska Panhandle with upslope northeasterly sfc winds along the Pine Ridge. Low clouds will be persistent across portions of the plains through the morning on Thursday. The coolest highs (mid to upper 60s) will be over the northern Nebraska Panhandle where some low clouds could persist through the entire aftn. South to southeasterly winds will become breezy by the aftn and early evening over much of the CWA. Kept 20-40 percent pops mostly confined to areas west of the Laramie Range through the aftn as the atmosphere will be capped/stable over the plains. Could see a slightly better coverage of showers and isolated tstms into Thursday night as the better forcing ahead of the upper trough arrives. Another round of stratus over the Panhandle is expected by Thursday night. .LONG TERM...(Friday through Tuesday) Issued at 230 AM MDT Wed Sep 21 2016 Unsettled in the long term as low pressure tracks across the area. Best chances for rain will be Friday and Saturday as the low tracks across the area. By Saturday evening, the low will be east of us in North Dakota with chances for precip ending. It will be cold Sunday as 700mb temperatures fall to -4C across the area. May not get out of the 50s for highs for many areas with low temperatures in the 30s for many areas. Warmer weather returning for the beginning of next work week. Forecast looks dry as high pressure builds back into the area. && .AVIATION...(For the 12Z TAFS through 12Z Thursday morning) Issued at 502 AM MDT Wed Sep 21 2016 VFR for all TAF sites through the day. Tonight though, we see northeast upslope winds that will begin to bring lowering ceilings into the Panhandle. Started off MVFR at KCDR, KAIA and KBFF. Later shifts may need to lower to IFR as the event draws closer. && .FIRE WEATHER... Issued at 230 AM MDT Wed Sep 21 2016 No fire weather concerns through the end of the week. Temperatures will cool over the next few days, and especially after Friday behind a cold front. Minimum afternoon humidity values will fall into the 20-30 percent range this afternoon. Further moistening will occur on Thursday and Friday along with an increasing chance of showers across portions of the region. && .CYS Watches/Warnings/Advisories... WY...None. NE...None. && $$ SHORT TERM...ZF LONG TERM...GCC AVIATION...GCC FIRE WEATHER...ZF
Area Forecast Discussion
National Weather Service Lincoln IL
949 AM CDT WED SEP 21 2016 .UPDATE... Issued at 936 AM CDT Wed Sep 21 2016 Convective issues causing a challenging forecast for today. Outflow boundary, from the earlier line of storms which passed through Chicago, is currently approaching Galesburg, Peoria and Bloomington from the northeast. This caused the line to weaken rather quickly as it began to outrun the line. However, convection from Wisconsin has now settled into far northern Illinois in an west-east configuration in the border counties. HRRR has been struggling to handle the storms over the last several hours, and has this secondary line weakening as well before reaching us. Forecast was updated earlier to add some 20-30% PoP`s across the far northern CWA for a few hours this morning, which appears sufficient for now. Will monitor the secondary line for a couple hours to see if any additional PoP`s need to be added for midday or afternoon. Temperatures will also be a challenge as well, between the outflows and the cirrus shield from the decaying MCS to our north. Already up to 80 degrees across the far southwest CWA, which is in line with the previous forecast. Have made some adjustments to the hourly trends across the north to reflect the outflows and increased cirrus, but the remainder of the forecast area still expected to get to near 90. && .SHORT TERM...(Today and tonight) ISSUED AT 325 AM CDT Wed Sep 21 2016 The recent stretch of unseasonably warm weather will persist across central and southeast Illinois today (and several more days actually). These warm conditions will be supported by persistent southerly low-level flow and the continued building locally of a flat upper-level ridge. Based on yesterday`s high temperatures and minimal airmass change, boosted today`s highs into the 90s areawide. The airmass has become more humid over the past 24 hours and may not heat quite as quickly today, suggesting going even warmer for highs today would not be prudent. Aside from the heat, only other concern of note this period is the threat for showers/storms across the north. A storm complex is currently chugging across the upper Midwest, and it has shown some tendency to turn toward the right into the richer moisture/instability. Some guidance suggests outflow from this complex may fire off a few storms across our far northern counties later today or this evening. At this point, think it will be a close call, but favor keeping forecast dry with any activity staying just north of the area. Convective trends will need to be monitored closely today in any event. .LONG TERM...(Thursday through Tuesday) ISSUED AT 325 AM CDT Wed Sep 21 2016 Forecast remains unseasonably warm and dry for the rest of the week in Central Illinois. Temps in the mid to upper 80s through the weekend. With the persistent delaying of onset of precip with the next system...think the guidance is actually going a little low on the max temps this weekend and think the forecast will trend to near 90 in some locations for Fri/Sat. Main issue with the forecast remains the trof that moves into the west coast on late Thu/Fri. The models have been modulating back and forth btwn phasing the wave into the northerly synoptic stream and producing a more cut off low over the SW, delaying the onset of precip to the Midwest. Latest GFS and ECMWF runs are more of a hybrid, progressing a weakly phased wave across the Plains, and almost stalling in the mid Miss River Valley for late in the weekend/beginning of next week. As a result, the pops start up Sun night and continue through at least Tuesday at this point. With the models struggling with the pattern shift overall, pops are confined to 20-30 percent for now. After the system arrives Monday...temps cool off considerably with the trof. && .AVIATION...(For the 12Z TAFS through 12Z Thursday morning) Issued at 635 AM CDT Wed Sep 21 2016 Generally quiet/VFR aviation weather conditions expected across the central Illinois terminals through the 12Z TAF valid time. The only potential exception would be if some convection manages to fire across parts of the area along an approaching outflow boundary from northern Illinois. This would mainly be a threat at KPIA, KBMI, or KCMI, but feel chances of TSRA are too low to mention at this time. && .ILX Watches/Warnings/Advisories... NONE. && $$ UPDATE...Geelhart SHORT TERM...Bak LONG TERM...HJS AVIATION...Bak
Area Forecast Discussion
National Weather Service Northern Indiana
1154 AM EDT Wed Sep 21 2016 .SYNOPSIS... Issued at 318 AM EDT Wed Sep 21 2016 Above normal temperature will continue into at least Thursday with highs well into the 80s both days. Shower and thunderstorm chances may return by Sunday as a frontal boundary to the north sinks into the area and a slow moving front moves towards the area from the west. More seasonable temperatures can be expected next week. && .UPDATE... Issued at 1146 AM EDT Wed Sep 21 2016 Upstream convective complex fell apart as expected with just a few showers entering the northwest. 14z HRRR is now trying to develop some convection across NW Indiana with outflow from convection. SPC Mesoanalysis does show a capped but slightly unstable environment and any outflow could spark a storm or two if weak capping erodes. Have updated to include slight chance pops from the US 30 corridor northward over at least central and western CWA for this afternoon. Once debris cloudiness thins temps should rebound later this afternoon to near 80 north and lower to middle 80s south. && .SHORT TERM...(Today and Tonight) Issued at 318 AM EDT Wed Sep 21 2016 Another warm day will be in store for the region as frontal boundary re-establishes itself across southern Lower Mi and eventually shifts north. As advertised, convection quickly blossomed across SE Minnesota and quickly went upscale. 40 to 45 kt LLJ was focused ahead of the convection allowing for continued maintenance of a bowing segment taking aim on La Crosse WI as well as a large area of rain/embedded storms across central WI. Convection across central WI should continue east and likely weaken as it outruns best low level support. Storms over SE MN/WCtrl WI into NE IA will continue to drop SE and remain elevated keeping overall severe threat minimal. For our area specifically it would appear that any convective threat has been nearly eliminated. Only lingering concerns is unstable atmosphere across W/NW areas where CAPE values will push into the 1500 to 2000 J/KG range. If an outflow boundary emanates from the convection and moves into this area this afternoon, could see some isolated convection. However confidence very low in this scenario so no addition of storms with punt to day shift to monitor trends. Highs will reach into the lower to middle 80s with somewhat higher humidity values. && .LONG TERM...(Thursday through Tuesday) Issued at 318 AM EDT Wed Sep 21 2016 Proximity of key features would tend to suggest that the forecast area will remain high and dry into at least Sunday with highs well into the 80s Thursday and possibly Friday. Frontal boundary will remain draped north of the area with complexes of storms moving along it through Friday before main focus shifts to the west with stout trough and cutoff low that will meander towards the region next week to bring increasing chances for precipitation and what appears to be the potential for a shot of colder air with MEX guidance showing highs only in the lower to middle 60s by Wednesday. Grids to not reflect that drastic a difference as ECMWF remains slower and not quite as deep on the trough. After several days of above normal temps certainty exists on a return to near if not below normal temps next week. How fast this occurs remains to be seen. && .AVIATION...(For the 12Z TAFS through 12Z Thursday Morning) Issued at 655 AM EDT Wed Sep 21 2016 Wk/ill defined frontal zone will refocus through cntrl lower MI this afternoon northward of surface ridge centered just north of the OH river. Expect surface winds to veer southerly by mid morning and remain blo 10 kts. Otherwise vfr conditions through the period. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ UPDATE...Lashley SYNOPSIS...Fisher SHORT TERM...Fisher LONG TERM...Fisher AVIATION...T Visit us at www.weather.gov/iwx Follow us on Facebook...Twitter...and YouTube at: www.facebook.com/NWSNorthernIndiana www.twitter.com/nwsiwx www.youtube.com/NWSNorthernIndiana
Area Forecast Discussion...UPDATED
National Weather Service Baltimore MD/Washington DC
1013 AM EDT Wed Sep 21 2016 .SYNOPSIS... High pressure will build over the region through Thursday. A cold front will move through the area Saturday. High pressure builds again over the region early next week. && .NEAR TERM /THROUGH TONIGHT/... GFS not doing particularly well with extent of high clouds this morning. ECMWF and HRRR simulated cloud imagery doing much better and have followed their output closely. Expect current extent of high clouds to remain pretty much as is through midday with thining of high clouds in the afternoon and clouds shifting south and east by evening. Adjusted temps a bit based on model trends from ECMWF indicating a 2-3 deg rise from yesterday in the east with temps west of the Blue Ridge not showing any trend at all from yesterday. Showers to graze southern St. Marys county through the day with precip shifting south tonight. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... Onshore NEly flow persists Thursday with above normal temperatures, mid 80s, under mostly sunny skies as cloud shield looks to be along southern periphery of the CWA. Surface high pressure settles south over the area Friday with sunny skies and light/variable winds. Maxima mid to upper 80s. && .LONG TERM /SATURDAY THROUGH TUESDAY/... A transition to autumn weather will occur over the weekend after a cold front tracks down from the north Saturday afternoon. This is a dry trajectory...so don`t expect much if any rainfall with this system. After reaching 80 degrees Saturday it does not appear the area will be seeing that for the next several days. Sunday highs will likely only reach the mid 70s but the real story will be Sunday night/Monday morning when lows east of the mountains will drop into the lower 50s...and likely 40s in the Highlands. By Tuesday some warming to the atmosphere should take place ahead of a cold front. This will likely provide the next chance for rain to the Mid Atlantic. In somewhat of a coincidence..at IAD both since Sep 1 and Jan 1 the precipitation departure from normal is -2.21". && .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/... High cloud shield persists over the area from low pressure lingering along the NC coast. This is limiting fog development across the DC metros. Best fog chance through sunrise is at MRB though high clouds are currently over that area too. VFR conds prevail through Friday high pressure slowly settles south over the area. VFR conditions expected this weekend. && .MARINE... NEly flow 10-15kt down the main portion of the Bay through Thursday as low pressure lingers along the Carolina coast. Weak Nly flow Thursday night through Friday as high pressure settles south over the area. Winds could increase to near SCA values near/behind a cold front Saturday into Sunday. && .TIDES/COASTAL FLOODING... Elevated water levels persist through the rest of the week due to low pressure off the Carolina coast. Coastal flooding threat is low through Friday. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ PRODUCTS...BAJ/WOODY!/LFR
Area Forecast Discussion
National Weather Service Marquette MI
655 AM EDT WED SEP 21 2016 .SHORT TERM...(Today and tonight) Issued at 515 AM EDT WED SEP 21 2016 WV imagery and RAP analysis indicated a zonal pattern across most of the nrn CONUS with the exception of a trough digging into the Pacific Northwest. A shortwave riding along the 850 mb warm frontal boundary and instability/strong moisture transport gradient at nose of 30-35 kt 850 mb jet max has supported strong to severe t-storms over western and central WI early this morning. Some stray showers from this convective complex have made it into far south central Upper Mi with MNM reporting some sprinkles/light showers last evening into early this morning. Another weak shortwave rounding the broad mid-upper level ridge has triggered a few t-storms over ern MT and wrn ND. With the exception of the light -shra over the scntrl, the rest of Upper Mi has remained dry early this morning under influence of a sfc high pressure ridge over the area. Very dry airmass over our area reflected in 00z APX and INL soundings with very dry air noted from sfc up above 700 mb, and this will need to be overcome before pcpn can occur over Upper Mi today and tonight. Mid and high clouds have kept overnight temps warmer than last night, generally in the mid 50s to lower 60s. Today and tonight, Shortwave rounding the ridge over the Northern Plains will work its way into the Upper Great Lakes this afternoon. Models do show a corresponding increase in 305K isentropic ascent and 850 mb moisture transport with gradual northward movement of the 850 mb warm front in response to the shortwave passage, especially late in the afternoon into tonight which will likely support shower development. However, with the relatively dry ne flow developing north of the warm front below 850 mb, models (particularly the high- res models) are trending slower with the northward advance of developing pcpn and showing a sharper cut-off to pcpn over the nrn sections of Upper Mi deeper into the dry air. As a result have confined slight chc to low chc pops over the scntrl and wi border counties this morning with a gradual increase in pops toward the ne by late afternoon/evening. By late evening/overnight tonight generally have likely to categorical pops over the south half of the cwa with chc pops for the north half. Wouldn`t be surprised if the Keweenaw Peninsula stayed mostly dry through period as some of the models suggest as they will be farthest away from better convergence/isentropic ascent along 850 mb warm frontal boundary and from better 850 mb moisture transport. With MUCAPE values fcst into the 500-1000 J/Kg over the far south late afternoon into this evening some TS will also be possible and possibly a strong storm or two with up to dime-sized hail given strong deep layer shear present. The thickening clouds and developing ne low-lvl flow will limit highs today to the mid 60s to lower 70s, warmest south and east. Lows tonight will generally be in the 50s under persistent cloud cover. .LONG TERM...(Thursday through Tuesday) Issued at 432 AM EDT WED SEP 21 2016 An increasingly amplified pattern is still on track to develop across N America for the remainder of this week into the weekend. Ridge/positive height anomaly currently moving into nw Canada will strengthen as it shifts across the Northwest Territories to Nunavut by the end of the week. The magnitude of the positive height anomaly at 500mb will reach 3 standard deviations above the long term late Sept avg. To the s of this anomaly, a trof will amplify over the western CONUS over the next few days, and the building downstream ridge over the central CONUS will then link up with the n central Canada positive height anomaly, leading to a sharp mid continent ridge for a brief time. In response, trof over se Canada will deepen and expand into the ne CONUS this weekend. This suggests that after wet weather into Thu, a drier period should mostly dominate Fri/Sat and potentially thru Sun as sfc high pres associated with the sharp upstream ridge builds se into northern Ontario and the Upper Great Lakes. Early next week, a more progressive flow regime should begin to take shape again. Initially, building of a ridge into western N America will send a shortwave se into the Upper Lakes later Mon/Tue. This wave will incorporate at least some of the energy in the western CONUS trof with the remainder dropping s. A period of shra will accompany this shortwave across the area at some point Sun/Mon with drying following for Tue. As for temps, readings will probably not stray far from late Sept normals during this period. Beginning Thu, last in a string of weak shortwave energy lifting ne thru the western Great Lakes will move e of the area by late aftn. Meanwhile, downstream of the western Canada ridge, a stronger shortwave will drop into northern Ontario during the day and then into Quebec Thu night. Following this wave, sfc high pres associated with the sharpening mid/upper ridge in central Canada will build se into northern Ontario Thu night, pushing frontal boundary extending from the Plains to the Great Lakes southward. As a result, expect a trend for shra Thu morning to diminish and/or end from nw to se during the aftn thru Thu night. With sfc high pres dominating northern Ontario on Fri and frontal boundary/baroclinic zone shifted farther s and sw, expect a dry day. Will need to watch development of pcpn into the northern plains where strengthening southerly flow/isentropic ascent ahead of western CONUS trof leads to an expanding pcpn area. Right entrance upper divergence with a reoriented upper jet in a nw-se direction across northern Ontario to New England could aid the expansion of pcpn toward Upper MI late Fri or Fri night. ECMWF has been most insistent on pcpn briefly streaking se into at least western Upper MI Fri night into Sat underneath right entrance of upper jet and within an eastward extension of isentropic ascent from the northern Plains. GFS/CMC have been more varied on whether or not the pcpn will reach the area, but since majority of GFS/CMC ensembles support the streak of pcpn, fcst will reflect chc pops spreading into the far w Fri night and expanding e into central Upper MI Sat morning before pcpn area dissipates. Fcst for Sun thru Tue is highly uncertain, much more than is typically the case at this time range and no different from the last few days. Over the last 4 days, medium range guidance has shown considerable spread in what happens with the western CONUS trof and how the flow evolves across southern Canada this weekend thru early next week. The 00z GFS is back to showing a mid level low closing off over the Upper Mississippi Valley/western Great Lakes early next week, a solution that appeared once days ago though it got to that solution in a different manner. At this point, consensus of recent days guidance is for a shortwave which incorporates at least some of the energy in the western CONUS trof to reach the area early next week, but wouldn`t be surprised at all if something completely different occurs. Maintaining some continuity with previous fcst, will show chc pops spreading slowly e across the area Sun/Sun night, lingering Mon then trending dry on Tue. && .AVIATION...(For the 12Z TAFS through 12Z Thursday morning) Issued at 649 AM EDT WED SEP 21 2016 Although there wl be a good deal of mid clds at times and perhaps a few -shra late this aftn, dry llvl air wl ensure VFR conditions prevail at all 3 TAF sites into early evening. Thicker clds and more numerous showers will arrive late this evening into overnight as conditions lower to MVFR at IWD by late evening and at SAW after 06Z. CMX may stay mostly dry through the period but they could also see MVFR conditions develop late tonight with increasing low-level moisture and developing upslope easterly flow. Look for IWD to lower to IFR by around 06z. && .MARINE...(For the 4 AM Lake Superior forecast issuance) Issued at 515 AM EDT WED SEP 21 2016 Developing ne flow over Lake Superior with sfc trough moving into Upper Mi and sfc ridge over Ontario could support some higher wind gusts to 25 knots over the wrn half of the lake this afternoon into Thu and across the entire lake Thu night into Fri. As the Canadian high builds more over the Upper Lakes winds will dip blo 20 kts Friday night into Saturday night. Southerly winds will increase late Sunday into Sunday night to 25 to 30 knots over mainly the north central and eastern part of the lake as a low pressure trough approaches from the west. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...Voss LONG TERM...Rolfson AVIATION...Voss MARINE...Voss
Area Forecast Discussion
National Weather Service Omaha/Valley NE
616 AM CDT WED SEP 21 2016 .SHORT TERM...(today through Friday) Issued at 330 AM CDT WED SEP 21 2016 Thunderstorm chances this afternoon through Thursday are the primary forecast concerns this period. Warm temperatures to continue as well. Upper flow pattern was beginning its change as strong westerlies across the Northern Plains were progressing east as strong low/trough dropped into the Pacific Northwest early Wednesday. Southwest mid level flow will remain over the Central Plains through tonight, then shortwave ridging will build into our region later Thursday into Friday. Shortwave within southwest flow aloft is shown currently by RAP analysis moving through eastern Colorado, heading toward Nebraska and Iowa later today and tonight. Meanwhile quasi- stationary surface front extended from northeast Colorado into southeast South Dakota and western Wisconsin. This boundary will not move a whole lot much of the day as upper flow parallels front, waiting for surface low tied to upper shortwave to develop and move from central Nebraska into northern Iowa this evening. Increased low level convergence ahead of the low will help ignite storms this afternoon, then southward drift of front will occur in its wake helped along by convection. Expect storms to take some time to get going later today as inhibition is slowly eroded and where low level convergence is maximized in northeast Nebraska and southeast South Dakota ahead of surface low. Instability increases markedly from near 1500 j/kg of MLCAPE in northeast Nebraska to closer to 2500 j/kg in northwest Iowa as per GFS, so we may miss initial development northeast of our area around 00Z. As the evening progresses, southward drift of surface front behind low combined with increasing moisture transport over that boundary as low level jet kicks up will bring our best chance for convection. Appears the best conjunction of those parameters will lie somewhere between Columbus and Norfolk, northeast to between Wayne and Tekamah, and into Monona County Iowa. Expect storms to fire somewhere in this zone by 03Z, then expand east and west with time. Continued moisture feed into south and southwest flank will lead to some propagation southward toward Interstate 80 overnight, but storms south of the Interstate may be hard to come by. Certainly could see severe storms given degree of instability but overall bulk shear is modest at best. Storms becoming more outflow dominant and loaded with precipitation suggests damaging wind gusts or microbursts are possible as well. Heavy rain is also likely given high precipitable water values near 1.75 inches shown by GFS, and potential for training storms. Bulk of overnight activity will be pushing off to the east Thursday morning. Overall mid level pattern of building shortwave ridge across our area will support northward propagation of frontal boundary, but will not clear our northern border until later Thursday night. Thus redevelopment of convection appears likely Thursday afternoon where models support 2000 j/kg of ML and SB CAPE and Bulk Shear is near 30kt. By Friday morning building heights and front lifting north should leave most of eastern Nebraska and western Iowa under capping mid level temperatures. Surface temperatures should reach the upper 80s again most spots Friday afternoon. In fact much of eastern Nebraska and western Iowa will average mid and upper 80s for highs each afternoon today through Friday. While highs Tuesday reached the 90s all areas, more cloud cover today will likely hold temps down a tad, though areas along and south of Interstate 80 could top 90 again. And Thursday afternoon northeast Nebraska will be north of retreating front and may not reach 80 in some areas. .LONG TERM...(Friday night through Tuesday) Issued at 330 AM CDT WED SEP 21 2016 GFS and ECMWF are fairly consistent in showing upper low rotating into the Northern Plains on Saturday with trough axis extending into New Mexico. They are also fairly close in depicting plume of tropical moisture streaming into our region Saturday then being shoved east by Sunday evening. Those models then diverge quite a bit beyond that, with GFS offering a deep closed cyclone over Wisconsin solution by Tuesday, and ECMWF maintaining general trough over our region. As far as sensible weather in concerned, we will be on the cool side of the system with pockets of cold air aloft rotating across the region. Some of these may spark some showers from time to time, but the main weather story appears to be temperatures in the 60s or lower 70s for highs to start next week. Leading up to that, we will see periods of showers and thunderstorms Saturday into Sunday when moisture plume is on top of us. GFS again is painting precipitable water values of 1.75-2.00 inches across our area Saturday. Thus heavy rain remains a concern Saturday and Saturday night before bulk of activity pushes off to the east. && .AVIATION...(12Z TAFS for KOFK...KLNK and KOMA.) Issued at 616 AM CDT WED SEP 21 2016 Mesoanalysis as of 11z showed a surface low over southwest Nebraska with an associated stationary front stretching northeast through far northeast Nebraska into northwest Iowa. Aloft, considerable high cloudiness was present over the mid Missouri Valley, downstream from a mid-level impulse moving through the central Rockies. LLWS will likely persist at all three TAF sites for the next couple of hours, prior to the cessation of the nocturnal LLJ. Thereafter, deeper boundary-layer mixing will yield gusty south winds which should subside by evening. The above-mentioned mid-level impulse will combine with the surface front to foster scattered thunderstorms this evening into tonight. Considerable uncertainty still exists with respect to the exact location of this convection. Therefore, only PROB30 groups have been included at this juncture. && .OAX Watches/Warnings/Advisories... NE...None. IA...None. && $$ SHORT TERM...Dergan LONG TERM...Dergan AVIATION...Mead
Area Forecast Discussion
National Weather Service Pueblo CO
416 AM MDT WED SEP 21 2016 .SHORT TERM...(Today and tonight) Issued at 343 AM MDT Wed Sep 21 2016 Currently... Abundant moisture associated with remnants of TC Paine were moving over the southwest CONUS. Several bands of showers were noted in the radar mosaics (Note: KGJX is out for scheduled long term maintenance upgrade). It was still quite mild at 4 am as temps were still mostly around 70F across the plains with cooler temps over the higher terrain. Some snow was likely falling well above treeline. Today... The combination with a tightening 500 mb gradient associated with a major trough moving onshore from the Pacific and the remnant moisture of TC Paine will allow for lots of mid and high level clouds over the region today. On and off showers will occur over the higher terrain with the southwest mountains being favored. Areas from the La Garitas to the Salida region may also see an enhanced area of showers as per latest HRRR guidance. Isolated showers and storms will also occur over the plains...especially along a trough axis which will extend from roughly Trinidad to Lamar. Some locally heavy showers will be possible. Another warm day will occur across the plains although temps should be tempered a bit due to the cloudiness over the region. Breezy southwest winds will occur at times over the plains. It will be windy across the mountaintops today...especially this morning. Tonight... Somewhat drier air will move into the region and precip chances will significantly decrease across most of the region as the evening progresses. Breezy conditions will continue over the higher elevations and over the plains mainly south of a line from Lamar to Trinidad. Another mild night is likely across the plains due to the breezy conditions and clouds...and lows will likely remain in the 50s to around 60. .LONG TERM...(Thursday through Tuesday) Issued at 343 AM MDT Wed Sep 21 2016 Models in good agreement through the extended period. Much cooler temperatures are on the way after a few more warm days. Thursday and Friday...a strong upper level low is forecast to develop over the Great Basin, forcing high pressure to build across the central plains. This will bring continued moist southerly flow to southern Colorado. Expect to see showers and thunderstorms develop over the mountains on Thursday afternoon, and spread northeast across the Palmer Divide into northeast Colorado Thursday evening. Gusty winds are also expected across the plains on Thursday, however, humidity values are expected to remain in excess of 15 percent, with near critical fire weather conditions expected. Models are also developing scattered showers and thunderstorms over the far eastern plains Thursday evening, which will move east into Kansas overnight. Severe weather and dangerous fire weather conditions are possible on Friday. The upper low is forecast to shift east into Utah on Friday with increasing southerly flow across Colorado. Models develop a surface low over northern Colorado by Friday afternoon with a dryline extending south across our plains. Decent moisture, strong shear and modest instability should allow for thunderstorm development Friday afternoon along the boundary. Strong to severe storms are possible, with strong out flow winds in excess of 60 mph and 1 inch diameter hail being the main threats. Current model projections have the greatest threat for severe weather east of a Fowler to Trinidad line, but much will depend on how far east/west the dryline sets up. Strong southwesterly winds and drier air is expected west of the dryline, generally in the lee of the eastern mountains into the I-25 corridor. Humidity values look to fall right near 15 percent Friday afternoon producing dangerous fire weather conditions. This will need to be monitored closely. Temperatures will remain warm Thursday and Friday with upper 80s to mid 90s expected across the lower elevations. Saturday into Sunday...the upper low is forecast to lift into the northern plains over the weekend with energy splitting over the desert southwest. Saturday looks to be generally dry across the area as the upper system splits. Temperatures will be much cooler with mostly 70s across the area. A strong cold front will drop south Saturday night with a northerly wind shift by Sunday morning. Models agree on the front, but not with precipitation chances. The GFS is dry behind the front on Sunday. Meanwhile, the ECMWF develops widespread showers across the area behind the front due to better upslope flow and moisture. For now have low pops for upslope favored areas of the plains. Reduced afternoon highs on Sunday to the upper 60s to lower 70s, however, a few solutions are indicating temperatures may not get out of the upper 50s. If precipitation does fall over the mountains this weekend, a few inches of snow are possible above 10 kft. Monday into Tuesday...the upper system will continue to lift into the Great Lakes region while high pressure builds over the western states into Colorado. This should bring drier conditions along with a warming trend early next week. Any precipitation should remain confined to the higher terrain and be diurnally driven. Temperatures will rebound back into the 70s to lower 80s. Mozley && .AVIATION...(For the 12Z TAFS through 12Z Thursday morning) Issued at 343 AM MDT Wed Sep 21 2016 VFR conditions are expected during the next 24h at all 3 taf sites...kpux...kals and kcos. Breezy 20ft sfc winds will prevail this afternoon. An isold shra.-tsra will be possible but any precip will likely be brief. Lots of clouds will prevail but they will be mid and upper lvl clouds. && .PUB Watches/Warnings/Advisories... NONE. && $$ SHORT TERM...HODANISH LONG TERM...MOZLEY AVIATION...HODANISH
Area Forecast Discussion
National Weather Service Blacksburg VA
905 AM EDT Wed Sep 21 2016 .SYNOPSIS... An upper low will meander about eastern North Carolina and South Carolina through late week before finally shifting out into the Atlantic ocean. High pressure will gradually build in from the west during the latter half of the week. A backdoor cold front drops south through the area later Saturday followed by cooler high pressure Sunday into Monday. && .NEAR TERM /THROUGH TONIGHT/... As of 905 AM EDT Wednesday... Made some minor adjustments in temperatures shaping towards sfc obs and lamp guidance for this morning, then allowing for a rise in the east this afternoon. (Clouds cover and scattered showers will hold temperatures down this morning in Southside.) Also, modified pops for this morning with latest WSR- 88d trends and push isolated chances a little further west for this afternoon. The Hiresw-arw-east, WRF-arw-rnk and HRRR support the mention of isolated to scattered showers across the southeast portions of forecast area. Expecting a nice day under sunshine in the west and northwest portions of forecast area. More changes later this morning. As of 315 AM EDT Wednesday... Looking at lingering low pressure from Julia combined with upper low over Eastern NC to keep the eastern half of the forecast area in clouds for most of the day today. Models in general agreement in showing a sharp gradient to showers, mainly keeping them southeast of a line from Farmville to Yadkinville. The 00z ECM is a little more broad in coverage as far west as the Blue Ridge. The 00z NAM actually seems to have a good handle of ongoing showers east of our forecast area, but is showing some higher qpf later today across the northwest piedmont of NC east of Reidsville into Halifax county Virginia. For the forecast today, am leaning toward a drier scenario from the foothills west into the mountains with high chance pops in the extreme southeast cwa to slight chance/20 pops toward Lynchburg/Martinsville and Yadkinville. High level clouds will obscure the sunshine at times as far west as the I-81 corridor with more sunshine in Southeast WV and generally cloudy in the east. Highs will still be warm with mid 70s to around 80 expected, but possibly warmer toward Abingdon and Richlands in the lower 80s. The gradient today will also tighten to allow a breeze of 10 mph with gusts to 20 mph especially along and east of the Blue Ridge. Tonight, the upper low remains fixed across the coastal Carolinas. At the surface the low jogs somewhat southwest. Orientation for best shower coverage will wrap tighter toward the coast, so will dry things out overnight with lingering low chance pops in the evening in the far southeast from South Boston VA to Reidsville, NC. Otherwise will be clearing in west but remains mostly cloudy in the piedmont south of Lynchburg, as well as across the NC mountains and foothills. Lows should stay mild in the east with mid 60s, with upper 50s to lower 60s west, which is still about 5 to 10 degrees above normal. && .SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/... As of 230 AM EDT Wednesday... During this portion of the forecast, a upper low over South Carolina will make slow progress to the southeast, all while an upper ridge builds over the Ohio and Mississippi Valleys. Concurrently, a broad upper trough will reside over southeast Canada, and southerly flow on its west side will propel a backdoor cold front into our region Saturday into Saturday night. The result of this transition will be even less coverage of isolated showers across the south and southeastern portion of the region. Only the Canadian solution at this point has more of a glancing blow of precipitation for this portion of the forecast area. The forecast will reflect the last isolated showers departing the far southeastern sections Thursday evening. High pressure will provide for limited cloud cover on Friday into Friday night with no precipitation forecast. The backdoor cold front at this point is progged to have little if any precipitation associated with in Saturday into Saturday night, but an increase in cloud cover is anticipated. Lower dew point air will start moving into northern sections of the area by late Saturday night. Temperatures will continue to average about ten degrees above normal through Saturday night. && .LONG TERM /SUNDAY THROUGH TUESDAY/... As of 130 PM EDT TUESDAY... Strong upper ridging centered along the Mississippi River to start the weekend will gradually get pinched back to the southwest as a rather high amplitude troughing regime develops over the northeast U.S. by early next week. This will allow increasing northwest flow aloft to take shape across the region between the departing 500 mb ridging and eventual upper level low pressure over New England. Cooler high pressure expected Sunday into Monday. This before yet another cold front arrives from the northwest on Tuesday with the next stronger mid level shortwave. However deeper moisture looks quite limited with both frontal passages given a dry west/northwest flow aloft so only including slight shower pops later Saturday west and again Tuesday. Low level flow turning more east/northeast behind the initial boundary, per the developing wedge could allow for a slight uptick in shower coverage southern sections Saturday night, although iffy for much more than clouds/sprinkles at this point per lower amplitude/drier ensembles. Subsequent rounds of decent cool advection look to arrive with each frontal passage into late Tuesday with potential for Sunday into Monday to remain quite cool if clouds are more widespread. This timing continues to vary between solutions as each may be too strong, although thinking highs mostly 70s Sunday-Tuesday, with 50s for lows and possible 40s valleys Monday morning with high pressure overhead. && .AVIATION /13Z WEDNESDAY THROUGH SUNDAY/... As of 735 AM EDT Wednesday... MVFR ceilings to affect DAN and at times LYH early then become VFR. A few showers are possible near DAN but coverage is such that it was not considered to be mentioned in the tafs. The fog never developed at LWB, and we should be seeing VFR for most of the taf period. Winds will be breezy along and east of the Blue Ridge with the gusts reaching 20kts at times between 16-22z. Tonight the skies will clear from northwest to southeast to a point, but remain broken at the high cloud level overnight in the DAN area. Model forecast soundings with easterly flow suggest potential for low cloud development or advecting in from the east along with patchy fog. Will keep it optimistic and go no lower than MVFR at LYH/DAN/BLF/BCB on vsbys with IFR at LWB late tonight. Extended aviation discussion... Thursday and Friday, outside of late night/early morning fog/low clouds, expect mainly VFR conditions. The slight chance of showers will remain just east of KLYH and KDAN through Thursday night. GFS/ECMWF have been consistent in filling and lifting out the low to the northeast on Friday. A back-door cold front will come through the Mid-Atlantic region on Saturday. High pressure will build in for Sunday. The chance of precipitation or any sub VFR conditions will increase through the day Sunday and into Sunday night. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...RAB/WP NEAR TERM...KK/WP SHORT TERM...DS LONG TERM...JH AVIATION...AMS/RCS/WP
Area Forecast Discussion
National Weather Service Las Vegas NV
845 AM PDT WED SEP 21 2016 .SYNOPSIS...Weather will remain cool and unsettled through the end of the week as remnant tropical moisture interacts with a trough pushing in from the west. The trough will bring increasing winds and and drier air which will aid in dangerous fire conditions for some areas along with the possibility of strong thunderstorms in northwest Arizona and eastern Nevada. Temperatures will remain cool through the weekend before inching back to near normal early next week. && .UPDATE...Made some adjustments to the grids this morning to increase the PoPs across northern Mohave county where persistent rain continues this morning. Best chances for showers will again be across areas south of I-15 today though chances will increase across our Northwestern zones this afternoon as a trough begins to approach the region. -Outler- && SHORT TERM...Through Friday night. At 4 am, showers continue to stream up from the south moving across western San Bernardino, far southern Clark and central and northern Mohave counties. Radar return intensity and rain gauges suggest mainly light and occasional brief moderate rain. The latest HRRR forecasts spotty shower activity today tied primarily to the mountains. The NAM and GFS forecast better coverage with the best chances in Mohave County. Abundant moisture remains in place through the day and models forecast weak instability for a better shot at embedded thunderstorms this afternoon. The trough advances into central California and western Nevada tonight with a cold front pushing into the northwestern regions of the CWA. A period of stronger winds are forecast across the Sierra with some potential for winds to reach the lower western slopes of the Owens Valley. Issued a Wind Advisory for these areas beginning late this afternoon and continuing through noon Thursday. The front continues to move south through the area on Thursday creating strong southwest to west winds ahead of it and gusty north winds behind it. Wind Advisories were also issued for portions of southeast California, southern Nevada and northwest Arizona beginning at noon Thursday. The cold front will push moisture to the east as it advances through the area Thursday with showers and storms limited to mainly the eastern portions of the forecast area. There is some concern for training storms and the potential for flash flooding in Mohave County Thursday prior to the decrease in moisture. Model forecasted instability is not overly impressive so will let the day crew take a look at it. The trough moves agonizingly slow and it not forecast to be east of the area until late Friday. However, dry air is solidly in place and no precipitation is expected on Friday. Breezy north to northeast winds and cooler temperatures are expected. High temperatures Friday will be 10-15 degrees below normal with a chilly morning low Friday around 10 degrees below normal. .LONG TERM...Saturday through Tuesday. Forecast confidence is above average for Saturday and Sunday as what little spread the models show would be of little impact on our sensible weather, then confidence quickly deteriorates Monday and Tuesday as spread increases and also begins to focus in and around our area. For Saturday and Sunday, the low pressure system which affected the area in the short term will have moved away to the east, with Pacific high pressure nearing the coast. This puts our area in northerly flow aloft with very dry air in place. The main foci for this period will be gusty northerly winds down the Colorado River Valley and a substantial warming trend area wide. For Monday and Tuesday, as the low and its associated trough roll east across the Plains, a significant number of model perturbations break a piece of energy out of the base of the trough over Texas, and then retrograde it west as a closed low around the southern periphery of the Pacific high. A smaller number of these perturbations /including the operational GFS20/ ingest tropical moisture into this closed low and pull it into our area late in the week. This is a long way off, and would be an unusual pattern evolution to say the least. Will keep an eye on Thursday and Friday as they move into the seven-day forecast period. && .FIRE WEATHER...Strong winds and low humidity will combine forces to create a period of critical fire weather conditions Thursday afternoon. Fuels remain very dry especially north of I-40 which will see little benefit from the remnant moisture of tropical depression Paine. Red Flag Warnings are in effect for the San Bernardino County deserts, much of the lower elevations of Clark County, the lower Colorado River valley and Lake Mead NRA. Improving conditions are expected friday as the winds relax. && .AVIATION...For McCarran...Winds will be light and diurnally driven this morning then stronger SW winds kick in by late this afternoon. A slight chance of storms tomorrow afternoon/evening. For the rest of southern Nevada...northwest Arizona...and southeast California...Primarily S/SE winds this morning increasing in the afternoon. An increasing chance of storms by this afternoon. Strong winds will develop over the Sierra tonight and possibly into the lower western slopes of the Owens Valley. Westerly winds could reach as far as KBIH with gusts up to 20 kts possible tonight. && .SPOTTER INFORMATION STATEMENT...Shower and thunderstorm chances continue through Thursday. Strong winds are also expected in much of the area Thursday afternoon and evening. Spotter activation may be required Wednesday afternoon through Thursday. && $$ Short Term/Aviation/Fire Weather...Salmen Long Term...Morgan For more forecast information...see us on our webpage: http://weather.gov/lasvegas or follow us on Facebook and Twitter
Area Forecast Discussion
National Weather Service Albuquerque NM
319 PM MDT WED SEP 21 2016 .SYNOPSIS... Scattered showers and thunderstorms will move northeast across New Mexico through Friday. Some of the stronger storms may produce brief strong wind gusts and perhaps some small hail. Temperatures will be above normal in many areas through Friday before a strong cold front surges through the state by late in the day. Low temperatures will be the coldest since last spring for much of the state. Lows will range from the 20s and 30s across the northern and western high terrain to the 40s and 50s across the eastern plains. Temperatures will likely stay cooler through early next week with a chance for some showers across the eastern half of the state. && .DISCUSSION... The remnant upper level wave from what was formerly Hurricane Paine is shifting quickly northeast across NM this afternoon. It`s low level center dissipated off the northern Baja and any moisture that was associated with it has been washed out across a vast area of the southwest CONUS. Enough forcing is present aloft to combine with afternoon heating for a decent crop of storms around the central and western high terrain. Activity is cruising along and has potential to tap stronger winds aloft. Strong outflow winds and perhaps some small hail are possible with any of the stronger storms. The latest HRRR and SPC SSEO merges convection into an area over the San Juan Mts and the RGV this evening. Thursday is expected to be a repeat of today with perhaps a better focus along and west of the Cont Dvd. Friday will be a dynamic day across NM as a potent Pacific cold front surges southeast through the area. High temperatures will still be quite warm ahead of the front. Veering wind profiles and abundant moisture still in place over the region should allow for at least a thin line of storms along the main frontal forcing. 12Z guidance is still paltry with precip development and has actually trended drier than previous runs. Will maintain chance POPs for now. 700mb temps fall from near +14C to around +4C behind the front. This strong cold advection along with impressive dry air advection will lead into the coldest night since last spring for much of the state. Folks around Farmington will want to keep a close eye on the min temp forecast as we are currently advertising 35F. Sheltered areas that are typically colder may see their first freeze. Overall Saturday appears to be a tranquil day with cool northwest flow over the state. Max temps will be 10 to 20F colder than Friday. The upper level trough is now shown by most of the 12Z guidance to push slowly east away from the area while developing into a large scale upper low over the Great Plains. This is yet another change in the outlook so confidence remains low. Nonetheless, temps will stay cooler through early next week with the greatest potential for any precip over the east. Guyer && .FIRE WEATHER... Moisture levels surface and aloft considerably higher today than on Tue thanks in large part to moisture shunted northeast from the remnants of once Hurricane Paine. Enough sunshine has materialized to generate some spotty showers and thunderstorms across roughly the nw half of the fcst area. More isolated activity struggling to keep going just east and ne of the Sacramento mtns. Majority of the storms should be able to manage wetting rainfall. On Thu this moisture will begin to yield a bit to a drier sw flow out ahead of a deepening trough aloft moving into the Great Basin. Winds through a deep atmospheric layer over NM will be picking up as the upper trough and associated Pacific cold front approach. Lee side surface troughing across the east Thu will encourage development of breezy to locally windy conditions most areas by aftn. Despite some modest drying in the atmosphere Thu there will still be a decent chance of a few showers and storms mainly to the west of the eastern plains thanks to the dynamic forcing of the approaching trough. The main Pacific front should push into and through NM between late Thu night and Fri but moisture will be less Fri than Thu so fewer wetting showers and storms are expected, especially east of the Continental Divide. High temps behind the front across nw and west central NM will be a few to around 10 degrees below seasonal normals. With passage of a pretty healthy back door front Sat night and Sun daytime temps will be below normal pretty much all across the area. Chances for wetting rain later in the weekend and early next week still look to be less than what appeared would be the case a day or two ago, though eastern areas still have a pretty good chance. a developing closed low over to just west of the state looks a little less likely now than was the case over 24 hours ago. In fact by mid to late week next week daytime temps may head back well above normal. The Canadian fcst model though is still holding to a somewhat weaker upper low or deep trough hanging out over the state so dry and warmer for this time period not certain yet by any means. 43 && .AVIATION... 18Z TAF CYCLE VFR conditions will remain the rule across most of the fcst area, however the nw third of the area may still see a few instances of relatively brief MVFR cigs in stronger TSRA that develop this aftn into this eve. KGUP and KFMN still have a small risk of this occurring into this eve, but generally kept their fcst above the MVFR category. Elsewhere there will also be isold to occasionally sct SHRA/TSRA coverage mostly from the AZ line east to the highlands immediately to the east of the central mt chain. Some mt obscurations likely as well, especially over the north. The activity will diminish to far fewer in number between 03Z and 07Z, but a few patches of MVFR conditions could redevelop late tonight across roughly the nw third of the fcst area along with a few instances of mt obscurations redeveloping late also. 43 && .PRELIMINARY POINT TEMPS/POPS... Farmington...................... 57 82 52 68 / 20 20 40 30 Dulce........................... 49 78 47 65 / 50 60 60 60 Cuba............................ 51 76 48 65 / 40 40 30 50 Gallup.......................... 50 80 49 66 / 20 20 30 30 El Morro........................ 49 78 46 63 / 30 20 30 40 Grants.......................... 52 82 48 70 / 30 30 30 30 Quemado......................... 52 80 50 72 / 20 20 20 30 Glenwood........................ 59 84 56 75 / 20 20 10 30 Chama........................... 47 71 45 59 / 60 60 60 60 Los Alamos...................... 55 78 53 69 / 40 40 30 40 Pecos........................... 53 78 52 72 / 60 40 40 30 Cerro/Questa.................... 49 76 50 68 / 30 30 30 40 Red River....................... 45 70 43 66 / 30 30 30 40 Angel Fire...................... 41 72 42 68 / 40 50 30 40 Taos............................ 50 79 50 71 / 30 30 30 30 Mora............................ 52 76 52 70 / 40 50 30 30 Espanola........................ 58 83 57 77 / 30 20 30 30 Santa Fe........................ 57 77 54 72 / 50 30 40 30 Santa Fe Airport................ 56 82 54 77 / 40 20 30 30 Albuquerque Foothills........... 61 83 59 77 / 40 30 30 20 Albuquerque Heights............. 62 86 59 80 / 40 20 20 20 Albuquerque Valley.............. 60 87 59 82 / 40 20 20 20 Albuquerque West Mesa........... 61 87 58 81 / 40 20 20 30 Los Lunas....................... 59 88 56 83 / 40 20 20 20 Rio Rancho...................... 61 87 58 81 / 40 20 20 30 Socorro......................... 62 89 59 85 / 30 30 20 20 Sandia Park/Cedar Crest......... 57 79 54 73 / 50 30 40 30 Tijeras......................... 58 83 55 77 / 40 30 30 30 Moriarty/Estancia............... 54 80 53 79 / 50 30 30 20 Clines Corners.................. 54 80 52 76 / 40 30 20 20 Gran Quivira.................... 57 80 56 76 / 30 30 20 20 Carrizozo....................... 61 86 60 82 / 20 20 20 20 Ruidoso......................... 54 78 54 74 / 30 30 20 30 Capulin......................... 56 81 56 77 / 20 30 10 20 Raton........................... 54 83 54 78 / 20 30 10 20 Springer........................ 56 84 55 80 / 20 30 10 10 Las Vegas....................... 53 81 54 76 / 30 30 20 20 Clayton......................... 61 87 60 83 / 20 20 10 20 Roy............................. 59 83 58 79 / 20 20 10 20 Conchas......................... 66 90 64 86 / 20 20 10 20 Santa Rosa...................... 62 90 61 85 / 20 20 10 20 Tucumcari....................... 65 93 63 90 / 10 10 5 20 Clovis.......................... 61 88 60 87 / 10 5 5 10 Portales........................ 62 88 62 87 / 10 5 5 10 Fort Sumner..................... 63 88 61 87 / 10 10 5 20 Roswell......................... 62 90 62 90 / 10 10 5 10 Picacho......................... 59 84 59 83 / 10 20 10 20 Elk............................. 57 80 57 78 / 10 20 20 20 && .ABQ WATCHES/WARNINGS/ADVISORIES... None. && $$
Area Forecast Discussion
National Weather Service Denver/Boulder CO
322 PM MDT Wed Sep 21 2016 .SHORT TERM...(This evening through Thursday) Issued at 322 PM MDT Wed Sep 21 2016 The strong mid and upper level trough we have been watching for the past several days is currently located across the Pacific Northwest. It will dig south and west over the next 36 hours and by Thursday evening it will be located over the northern half of Nevada. The trough continues to advect mid level moisture into Colorado while the low levels remain dry until overnight tonight. The moist southwest flow will provide a slight chance of thunderstorms in the mountains and across parts of the Plains the remainder of the day. Early this evening the HRRR and NAM generate showers over the mountains and and the HRRR has been consistent in sustaining the showers across the urban corridor and then further east across Morgan, Lincoln, and Elbert Counties. Both models did the same thing yesterday under similar atmospheric conditions yet nothing materialized. Will introduce 10-20 percent PoPs in those areas but not expecting much if anything to reach the ground. Tonight a cool front brings mid 50s dewpoint air in through the backdoor across northeast Colorado after 3 AM. Stratus is possible if not likely across northeast Colorado. Less confidence in the stratus making it to metro Denver but it could come close to Denver International Airport. On Thursday strong southwest flow aloft continues and the atmopshere is fairly moist with PWATs east of the Rockies in the 0.75-1.00 inch range. The good news is that surface dewpoints east of the Rockies will be the highest they have been in many days. The bad news is that the moisture is shallow, short lived, and there is too little instability available to generate convection of any significance. As the trough approaches Colorado the low to mid level flow turns more south-southwest and will act to dry out the lower levels from west to east starting Thursday evening. Best chances for afternoon thunderstorms will be across the mountains. Temperatures should be in the mid 80s most areas though if stratus hangs on as long as expected, the north and northeast corner of Colorado may stay in the 70s. .LONG TERM...(Thursday night through Wednesday) Issued at 322 PM MDT Wed Sep 21 2016 For Thursday night, we could see a couple high based showers/ storms drift northeast out of the mountains onto portions of the adjacent plains, but overall airmass on the plains is still rather dry and stable so only low PoPs warranted if at all. By Friday, the unseasonably deep upper level low in the Great Basin is expected to lift northeast across Utah. Upper level support will increase but latest runs indicate some splitting of this energy, and a couple models including the GFS are very aggressive with the dry slot moving across the plains. At this time it`s looking like the drier airmass should prevail as a very strong and deep southerly flow develops across much of the forecast area. Winds will increase with lowering humidities increasing fire danger...see Fire Weather discussion below. There is still enough lift for a few high based afternoon showers and thunderstorms. Again, the best chance would be over the mountains and far northern sections of the forecast area where a little more moisture should hold in place. Friday night, the upper level trough or at least a piece of it and the cold front will move across the state. This will usher in cooler temperatures and also bring some snow to the mountains. At this time, looks like mainly light snow but some accumulation would be possible mainly over the far northern mountains from Rabbit Ears to Rocky Mountain National Park where deeper moisture and stronger orographics exist. That same general weather pattern will remain in place through Saturday with highs mainly in the 60s on the plains and 40s/lower 50s in the mountains. By Sunday, a few of the models are now indicating a second wave of energy now dropping across the area in Northwest flow aloft. That is in contrast to the shearing trough noted in yesterday`s model suite. In any case, will maintain the low PoPs but trend temps a bit cooler. If ECMWF verifies then we could see snow down through most of the foothills. For Monday and Tuesday, again in contrast to yestereday`s runs, models now show the deeper upper level low developing into the Midwest. Not sure exactly how this will eventually play out but will keep temperatures cooler than normal with only a slight chance of showers returning by Tuesday only if another wave drops into the area on northwest flow. Wednesday should see a return to near normal temperatures as long as upper trough moves to the east. && .AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon) Issued at 322 PM MDT Wed Sep 21 2016 |There is a slight chance of showers across the terminals this evening that would temporarily cause shifting and gusty winds. Around 12Z a backdoor front approaches KDEN. Winds behind the front will be light but with high low-level moisture in place, stratus is a concern. Not confident the stratus will make it to KDEN but put in a TEMPO group to provide a heads up for the potential. Aside from the low but nonzero chance of IFR ceilings between 12 and 15Z, VFR conditions should prevail with diurnal winds under 10 kts until late Friday afternoon when winds will pick up from the south. && .FIRE WEATHER... Issued at 322 PM MDT Wed Sep 21 2016 Fire danger will increase in all areas Friday as strong southerly flow results in gusty winds. Anywhere from the Mountains east across the Denver/Palmer Divide area onto the plains could see gusts around 40 mph due to the strength of low level flow and pressure gradient. Humidity is still marginal but if latest GFS trends continue we`ll have to upgrade to a Fire Weather Watch. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Schlatter LONG TERM...Barjenbruch AVIATION...Schlatter FIRE WEATHER...Barjenbruch
Area Forecast Discussion
National Weather Service Cleveland OH
658 PM EDT WED SEP 21 2016 .SYNOPSIS... High pressure will remain in control of the weather across the region into Thursday. A cold front will move into the Great Lakes on Friday then sag south of the area by Friday night. A cooler Canadian high pressure will arrive Saturday into Sunday. && .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... Only minor changes to cloud cover and hourly temperatures were made to reflect current trends. Previous Discussion... A few clouds around this evening...primarily across northern OH and nw PA. Some of this is afternoon cumulus which will fade quickly late this afternoon. The mid/high clouds emanated from a decaying MCS across MI this morning. They should drift across the lake this evening. Although it cannot be ruled out entirely...current satellite trends do not look favorable for shower/ts development across southeast MI...so Toledo and across the lake should stay dry. HRRR only guidance showing development early this evening. Otherwise another quiet night with high pressure overhead. Temperatures will be running above normal tonight...but still a number of inland locations will get into the 50s. && .SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY NIGHT/... Pattern begins to amplify for the remainder of the week. While an upper low takes up the Rockies/West Coast and ridge will build across the Mississippi Valley. Precipitation Thursday will remain north of the area along stalled frontal boundary across the Great Lakes. This will provide yet another day with temperatures well above normal. For reference...normals have now dropped into the lower 70s. A shortwave across central Canada will carve a trough across New England and bring the Great Lakes front southward. This front has the cooler weather bottled up to its north...so with its passage Friday temperatures will be brought back closer to normal going into the weekend. We will still likely reach and top 80 degrees Friday. Saturday all will be in the 70s with some upper 60s likely for highs across nw PA and a north-northeast flow. Little has changed with the outlook for precipitation with this front. Moisture and lift limited. Will continue with silent 20 percent chances Friday into Saturday. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... A rather substantial shift in the long range models is noted over the last 24 hours with a trend towards an upper level low closing off over the plains states. This blocking pattern would support a high amplitude ridge building back into the Great Lakes Region with temperatures trending warmer through the extended. Models had shown this blocking pattern last weekend and feel the shift back to it is supported by the strong upper jet over the North Pacific. With that said, started trending the forecast drier and warmer during the early part of next week. This pattern shift will need to continue to be monitored on later model cycles. && .AVIATION /18Z Wednesday THROUGH Monday/... VFR conditions with only cirrus will continue through the overnight. expect patchy mvfr br toward daybreak. OUTLOOK...Some MVFR possible Saturday night in scattered shra/tsra. && .MARINE... A ridge over the eastern Great Lakes will shift south and weaken through the end of the week. A weak area of low pressure will pass north of Lake Erie on Thursday with a weak cold front settling south across the lake on Friday. Northeast winds of 10-20 knots will develop behind the front Friday afternoon and night causing waves to build to 2 to 4 feet into Saturday morning. High pressure will strengthen over the eastern Great Lakes over the weekend maintaining easterly winds on the lake. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. MARINE...None. && $$ SYNOPSIS...Oudeman NEAR TERM...Mullen/Oudeman SHORT TERM...Oudeman LONG TERM...KEC AVIATION...DJB MARINE...KEC
AREA FORECAST DISCUSSION
National Weather Service Des Moines IA
344 PM CDT Wed Sep 21 2016 .SHORT TERM.../This evening through Thursday/ Issued at 344 PM CDT Wed Sep 21 2016 The primary concern into tonight is obviously convective trends include heavy rain and severe potential. The current Grinnell-Forest City outflow boundary from morning convection continues to try and initiate new convection but is having little luck sustaining anything or anchoring to it. A detailed look at the cells and radar fineline notes development on either side of the boundary suggesting this is mainly elevated. Thus even though uncapped 3000 j/kg MLCapes are in place just west of the feature there seems to be lRegarding rainfall potential, precipitable water and warm cloud depth values are not extreme, but seasonally high vs climatology promoting efficient rainfall rates. The outflow boundary has reduced confidence in high resolution solutions, but the HRRR, RAP and HopWRF had the best handling on earlier Upper MS Valley convection and suggest the northern few tiers of IA, eastward to the MS river could get hit with heavy rains overnight with 15z ESRL HRRR amounts up to an alarming 5-10 inches and the 15z HopWRF showing high neighborhood probabilities of at least 5 inches over NE IA out of our forecast area. Other models only show a few inches however, which is possible if the stronger Corfidi vector movement makes the convection too progressive north to south. So again it needs to be emphasized that a very high impact event is certainly possible but with somewhat diminished confidence due to model spread and uncertainties. Remember that this uncertainty is also carried over into the current river forecasts which include 48 hours worth of QPF rather than the typical warm season 24 hours. Current QPF depicts a widespread but middle of the road 2-3 inches of rainfall affecting the Winnebago and Cedar basins which results in moderate flooding in several locations. Changes in location or rainfall amounts on either side of that spread could result in lower or higher forecast stages. This is why Hydrological Outlooks rather than warnings have been issued until confidence in locations and magnitude increases.ow chances of anything getting rooted surface based at the moment. Convergence is shallow per the lack of 0-2km moisture convergence and surface winds east of the boundary are veering suggesting a downward trend in overall convergence. Some strong to severe elevated storms are still possible however with higher effective shear and ESRH still in place north and east of the boundary. The question into tonight then turns to where new MCS development will occur and its movement. Confidence is not the highest however as none of the models are handling the strength of the outflow boundary well. Examination of 305K isent surfaces show the NAM and GFS focusing 30-40kts of flow and convergence from the Mason City area into southern MN while the latest Rap washes this out more and highlights MN. The latest objective analysis shows the 925/850mb fronts and associated frontogenesis into MN so this would appear to be the favored MCS genesis region. It does not mean IA will be spared however. The strength of the inflow results in Corfidi vectors with a pronounced southern motion suggesting the MCS will eventually be drawn into IA. MUCapes of a few thousand should persist into the night with around 30kts of effective shear suggesting severe storms would remain possible with favorable shear orientation north to south into IA. .LONG TERM.../Thursday night through Wednesday/ Issued at 344 PM CDT Wed Sep 21 2016 Little change in going forecast for the next few days. Confidence in overall trends for heavy rainfall potential remains high...but details still debatable due to daily mesoscale interactions. By early Thursday morning still expecting ongoing convection across the north with old outflow boundary still the focus for some thunderstorm activity over the north half of the forecast area. Though the better forcing will be in the overnight period tonight...there will still be enough instability during the morning and afternoon hours to promote thunderstorms with locally heavy rainfall potential over the north half of the forecast area. Will maintain FFA across the area through tomorrow afternoon. Through the night another strong push of thetae advection will precede the next upstream wave propagating northeast by 12z Friday. Most of any convection should be confined to the north third Thursday night and north into Minnesota. With the boundary holding on there will still be the potential for additional locally heavy rainfall across the north. If trends continue... there may be a need for an extension of headlines there. By 12z Friday models push the warm front well into southern Minnesota. This will temporarily limit convection over our area as all of the forcing will be moving north. With the warm sector fully realized once again Friday...highs will move back into the upper 80s to lower 90s during the afternoon hours. Surface dew points will again remain rather uncomfortable in the mid to upper 60s...with heat indices well into the 90s by late afternoon. With the approach of an upper level trough over the northern Plains Saturday a cool front will move into the area by 12-18z. Models have advanced the front a bit faster...though the boundary begins to slow as it crosses the region from Sunday through Monday morning. Unfortunately... the tropical moisture feed will remain intact just along and east of this boundary. There is some uncertainty but if the boundary is hung up long enough additional moderate to locally heavy rainfall amounts of 1 to 2 inches may occur over the region between Saturday evening and Monday morning...especially east of I35. The GFS and Euro diverge thereafter...with the GFS focusing the boundary southeast of the region from Monday through Wednesday. The Euro holds the boundary over eastern Iowa and with a more northerly track of the northern Plains system into midweek next week as well as a rather strong southern stream H500 system developing by 12z Monday. The GFS has the northern system looping back southeast by 00z into the Central Plains with virtually no southern stream component at H500 at that time. The result here is that the surface boundary and rain is pushed out of the region by the GFS. For comparison...the GEM is even slower and farther west than the Euro. At this time...will have to weight the Euro/GEM solutions a bit higher and will need to closely monitor trends through the weekend. If the latter proves a better solution...the resultant rainfall over the region could additionally add several more inches of precipitation on top of what is projected through Monday. The reason...both the direct fetch from the Gulf and potential for another old tropical system being injected into the area from the southern Plains. Highs next week should be cooler with extensive cloud cover and chances for rainfall. && .AVIATION.../For the 18Z TAFS through 18Z Thursday afternoon/ Issued at 1259 PM CDT Wed Sep 21 2016 VFR conditions are in place area wide with main feature an outflow boundary along KMPZ-KFXY line at 17z with a sharp discontinuity from SW to SE wind. Convection is expected to develop near this feature into the evening and also along a NE/SD warm front. Thus expect periods of convection to affect KFOD/KMCW/KALO into the night. Timing, location and duration of MVFR or less conditions and thunder is still in question however so have nothing more than vicinity wording and VFR for now. && .HYDROLOGY... Issued at 344 PM CDT Wed Sep 21 2016 Regarding rainfall potential, precipitable water and warm cloud depth values are not extreme, but seasonally high vs climatology promoting efficient rainfall rates. The outflow boundary has reduced confidence in high resolution solutions, but the HRRR, RAP and HopWRF had the best handling on earlier Upper MS Valley convection and suggest the northern few tiers of IA, eastward to the MS river could get hit with heavy rains overnight with 15z ESRL HRRR amounts up to an alarming 5-10 inches and the 15z HopWRF showing high neighborhood probabilities of at least 5 inches over NE IA out of our forecast area. Other models only show a few inches however, which is possible if the stronger Corfidi vector movement makes the convection too progressive north to south. So again it needs to be emphasized that a very high impact event is certainly possible but with somewhat diminished confidence due to model spread and uncertainties. Remember that this uncertainty is also carried over into the current river forecasts which include 48 hours worth of QPF rather than the typical warm season 24 hours. Current QPF depicts a widespread but middle of the road 2-3 inches of rainfall affecting the Winnebago and Cedar basins which results in moderate flooding in several locations. Changes in location or rainfall amounts on either side of that spread could result in lower or higher forecast stages. This is why Hydrological Outlooks rather than warnings have been issued until confidence in locations and magnitude increases. && .DMX WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch through Thursday evening for IAZ004>007- 015>017. Flash Flood Watch from 7 PM CDT this evening through Thursday evening for IAZ023>028-033>039-044>048. && $$ SHORT TERM...Small LONG TERM...REV AVIATION...Small HYDROLOGY...Small
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
657 PM EDT WED SEP 21 2016 .AVIATION... Recent satellite data indicates localized subsidence across Lower Mi, which is currently causing the convection across Wisconsin to diminish as it moves east. Overnight, showers and thunderstorms are expected to eventually expand east into the northern Great Lakes along a frontal boundary, while some degree of subsidence holds across Se Mi. The subsidence is expected to keep convection north of the terminals through the night and well into Thursday. While MBS will be closer to the better feed of moisture/instability along the frontal boundary draped across the nrn Great Lakes, the probabilities of TSRA at MBS are still rather low, too low to include in the terminals attm. Satellite trends have shown enough thinning/decrease in high clouds working into Se Mi to suggest some periods of decent radiational cooling overnight. Given that sfc dewpoints are well in the 60s, a chance of some MVFR type visibilities in fog toward daybreak will be added to the TAFs. For DTW...Metro Detroit will remain far enough removed from the region of moisture and instability to the north and west to provide little to no chance for TSRA through the TAF period. The thicker cirrus will likely remain north of metro, so radiational cooling potential may support a brief period of light fog early Thurs morning. //DTW Threshold Probabilities... * None && .PREV DISCUSSION... Issued at 344 PM EDT Wed SEP 21 2016 DISCUSSION... Energetic upper levels continue through mid week as a nearly zonal 140+ knot jet streaks across the US/Canada border. Weak southern stream jet lifting northeast out of the developing west coast upper level trough, will send a series of shortwaves through the plains and into northern MI. The pattern has also resulted in a broad surface developing over the central plains with a warm front taking shape across the Central Great Lakes. This pattern will deviate very little now through the end of the week as the strong Hudson Bay low remains in place. Area should remain dry through the rest of the evening and into the overnight hours as subsidence in the wake of the early afternoon MCS settles over southern MI. Hires HRRR and RAP advertise some redevelopment this evening along I94 on the sinking outflow boundary but confidence is low in the occuring. The current cap will make it hard for anything to develop, even with a bit of late afternoon heating. Radar trends through the day have shown the convection struggling to advance much further west than Chicago away from the stronger height falls. Without any forcing locally and no shortwaves to speak of during the evening, think convection will struggle even with peak heating as skies begin to clear out somewhat. Tonight through Friday will focus on the warm frontal positioning and shortwaves/MCSs that will ripple along the front for possible showers and thunderstorms. Models have shifted north with the positioning of the surface front which in turn refocuses the developing isentropic forcing north. A brief shortwave ridge rounding the base of the Hudson Bay low will allow the jet to arch northward as well which will steer the approaching shortwaves further north as well. All this leads to shifting the pops north which really only leaves the Saginaw Valley and northern Thumb with a short at precip through Thursday. Will highlight the period from 09-15Z Thursday for the best opportunity as the shortwave lifts through northern lower aided by nocturnal low level jet and next surge of theta e. The rest of the afternoon will likely dry out for everyone again but with the front just to the north will leave a slight chance for the extreme north. The front will start to sag southward into mid MI Thursday night as a strong trough rotates around the Hudson Bay low giving it a push. It should passing through southeast MI by Friday afternoon which will be the next chance for showers and thunderstorms. Should see a good thermal gradient across southern MI on Friday with the front draped across the region. This will mark the end of the current stretch of 80 degree days as highs north of I69 will struggle to reach 70 with strengthening northeast flow off Lake Huron. Timing of the front will decide just how warm the Metro Detroit area can get before cooling back off. High pressure over Ontario will keep surface flow with an easterly component locally over the weekend. Sharp NW/SE low-mid level theta-E boundary across SE MI, and cannot totally rule out some light showers Saturday with weak positive theta-E advection and PWAT around 1.5 inches, but at this point expect most of the weekend to be dry. Low predictability early next week with guidance indicating a cutoff low taking shape somewhere to our west over the Northern Plains/Upper Midwest, with meridionally-oriented moisture plume ahead of it. Eastward progression of these features will determine rain chances early next week, and not a whole lot of model consensus at this point, so chance PoPs early next week will suffice for now. Despite rather warm mid-level temps, easterly surface flow is expected to keep temps in check near or slightly above normal. MARINE... A front will remain stalled over the northern Great Lakes tonight through Thursday. An active pattern of showers and thunderstorms will be the primary marine weather impact, mainly over northern Lake Huron, while wind and waves remains light/low over other marine areas. That will change Thursday night and Friday as the front settles southward into Ohio and opens moderate northeast flow over all areas. The long fetch of onshore, unstable flow over southern Lake Huron and into Saginaw Bay will likely produce waves exceeding SCA levels through Friday night before high pressure settles in Saturday. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...NONE. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....SC DISCUSSION...DRK/DT MARINE.......BT You can obtain your latest National Weather Service forecasts online at www.weather.gov/detroit.
Forecast discussion for routine afternoon forecast issuance

.SHORT TERM...Tonight and Thursday Issued at 226 PM CDT Wed Sep 21 2016 The latest RAP analysis and satellite/radar imagery show a surface warm front snaking from southern Minnesota to northern Illinois early this afternoon. Showers and thunderstorms continue to fire along the boundary over the same areas that received heavy rainfall last nite, namely southeast Minnesota and southern Wisconsin. Additional storms are firing over western Wisconsin in a region of low level moisture convergence. These storms will likely continue to develop and push into the I-39/route 51 corridor later this afternoon. An isolated severe storm will be possible from Lincoln to Waushara counties with mu capes above 1000 j/kg and 0-6 km shear of 45-50 kts. As a weak shortwave lifts across the Plains and into the western Great Lakes tonight, thunderstorm trends and potential for heavy rain/severe weather are the main forecast concerns. Tonight...An active period of weather, with an atmosphere conducive for heavy rainfall. A weak shortwave, currently over southwest Nebraska will lift northeast and across the region late tonight. Ahead of the shortwave, a strengthening 30-40 kt low level jet is anticipated to ride over the slowly northward advancing warm front later this afternoon into this evening. With ample instability and shear as shown on mesoanalysis imagery, showers and thunderstorms are expected to develop and expand upstream of the current thunderstorm activity over southern and central Minnesota, before sliding east through the night. Elevated capes of 1000-1500 j/kg suggest a severe storm cannot be ruled out through the evening, especially over areas from west of the Fox Valley and south of route 29. In addition, long duration of forcing combined with plentiful moisture (pwats of 1.75 to 2.00) continues to imply that a flood or flash flood threat is possible. The latest guidance shows that central WI from Lincoln to Waushara counties have the most risk for receiving heavy rainfall, with amounts of 1-3 inches possible (locally higher). Though concerns are not as high for flooding further east within the flood watch, potential for heavy rain will remain, especially over the southern Fox Valley where rainfall over an inch has already fallen early this morning. Temps ranging from the mid 50s north to mid 60s south. Thursday...Model guidance continues to show that the front will remain stalled over central and northeast Wisconsin. Though weak shortwave impulses will be passing to the east during the morning, periods of showers and storms will likely continue through the day. Weaker forcing and instability suggests rainfall only has a limited potential to be on the heavy side, so thinking additional amounts of a quarter to a half inch will be possible, locally higher in storms. With the rainfall and clouds, temps will remain cooler in the mid 60s to mid 70s. .LONG TERM...Thursday Night Through Wednesday Issued at 226 PM CDT Wed Sep 21 2016 A frontal boundary that was just to the southwest of Wisconsin early this afternoon is the main concern through the end of the week before a surface low pressure system brings a cold front into the state. The approaching warm front will keep at least a chance for showers and thunderstorms in the forecast through Saturday morning. Central and east central Wisconsin will be the main concern for heavy rainfall since the front is expected to be in that general area before it finally makes a stronger push to the northeast and clears the state late in the week. Looks like there could be a period of dry weather, with not even a slight chance POP, Saturday afternoon but confidence in timing is low. Have shower and thunderstorm chances returning with the approach of a cold front from the west, which may take a while to clear the state. The 12Z GFS, ECMWF and Canadian all started to exhibit significant differences for early next week but all looked quite wet through the end of the forecast period. Highs during the day should be within a couple of degrees of normal, and lows should be warmer than normal due to all of the clouds and rain. && .AVIATION...for 18Z TAF Issuance Issued at 1204 PM CDT Wed Sep 21 2016 Periods of showers and storms will impact the region later this afternoon through Thursday morning as a warm front lifts northward. Though storms are not expected to be severe, a few strong storms could move across the central WI taf sites, and produce small hail and gusty winds to go along with heavy rainfall. Cigs and vsbys are expected to deteriorate as the showers and storms arrive this evening, and only expected very slow improvement on Thursday morning. && .GRB WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch through Thursday evening FOR WIZ018>020-030- 031-035>040-045-048>050. && $$ SHORT TERM.....MPC LONG TERM......MG AVIATION.......MPC
Area Forecast Discussion
National Weather Service Wilmington NC
606 PM EDT Wed Sep 21 2016 .SYNOPSIS... The remnant circulation of former Tropical Storm Julia will maintain scattered showers through Friday. Drier weather should develop Saturday as high pressure pokes in from the north. A cold front will move through early Sunday, followed by several days of onshore winds and slightly cooler temperatures next week. && .NEAR TERM /THROUGH TONIGHT/... As of 300 PM Wednesday...Low pressure over southeast NC will drift slowly SW becoming more elongated along the SC coast by this evening with a trough extending northward from center of low. An easterly on shore flow will exist on the front end of low/east side of trough along the coast and continued NE-N flow inland, on back end of low/west side of trough. This pseudo warm front/trough will provide a warmer easterly flow and will allow for some drying and thinning of the clouds. At the same time energy will continue to rotate around this upper low combining with deeper layer moisture inland to produce showers and isolated thunderstorms wrapping around to the S-SE into Northeast SC. Pcp water values show a plume of deeper layer moisture with values over 2 inches running from VA/NC coast around to the SW to S through central NC/SC. Coastal NC will have some drier air wrapping around from the S to SE with pcp water values down closer to 1.7 inches this aftn. Overall, instability will remain marginal due in part to significant cloud cover, so although clouds will blanket most of the area, expect modest QPF amounts of most areas with greatest amounts aligned inland mainly just west of I-95 corridor. If areas break out along the coast, expect some heating and differential heating to produce some further convective development mainly across central portions of forecast area inland from the coast. As this deep low drifts S-SW toward the GA/SC coast through tonight, some deeper layer moisture will wrap back around over the Cape Fear region and should increase shwr activity over the eastern portions of the forecast area overnight as moisture and showers spread from the coastal waters along the coast in a deeper E-SE flow. Expect mainly light to moderate rain but some embedded heavier rain amounts are possible. Overall the cool pool aloft and continued moist flow will produce plenty of clouds and potential for pcp through tonight. Temperatures inland in northerly flow on back side of low will remain in the mid 70s this aftn while temps along the coast will reach over 80 especially where some breaks or thinning in the clouds occurs. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 300 PM Wednesday...The persistent mid to upper low will become more elongated and may drift westward before opening up into a trough along the east coast and moving off shore by Fri night. The center of the low will remain south of the area with trough extending northward maintaining a deeper on shore flow through the period. The trough looks like it will be just along or off shore which will keep a N-NE flow over much of the area but should see more of an E-SE flow at times along the coast and off shore as trough and diurnal shifts take place. Pcp water values will remain up above 1.75 inches through much of the period in a very moist air mass. With such deep layer moisture and a deep low/trough over the region through the period, expect unsettled weather to continue. While POP areal coverage should remain scattered most of this period, there will be bands of showers with more moderate to heavy rain across portions of the area associated with upper level energy rotating around over the region. Drying will finally take place late Fri into early Saturday as trough finally moves off to the east. Skies will begin to clear from west to east leaving partly cloudy skies by Fri night over most places. Max temps will reach near or around 80 during the afternoons overnight lows near 70 Thurs night but slightly lower Fri night as some clearing occurs. && .LONG TERM /SATURDAY THROUGH THURSDAY/... As of 300 PM Wednesday...The upper levels will certainly not look anything like summer with a very amplified trough-ridge-trough pattern expected to develop across North America. Models have struggled to form a consensus over the past few days with details, however the new 12z GFS may be on to something with its depiction of an Omega block developing by Tuesday. Due to this blocked pattern, the potential of a strong cold frontal passage late this month is now in jeopardy and we may remain in the tropical/subtropical humidity through the remainder of September. A 500 mb ridge centered across the Mississippi Valley on Saturday will only slowly work east into the Carolinas by Tuesday and Wednesday. A deep upper level low moving across the Canadian Maritime provinces will push a cold front southward along the East Coast, reaching the Carolinas early Sunday. The surface high behind this front won`t dive south, and in fact may only reach coastal New England by late Tuesday or Wednesday. This will create an extended period of onshore winds and the potential for scattered showers as a band of convergence behind the old front could settle across the area, coincident with at least shallow Atlantic moisture. && .AVIATION /00Z THURSDAY THROUGH MONDAY/... As of 00Z...A low level convergence boundary will affect LBT and FLO through about 01Z, with most of the convection dissipating after that. Overnight, fairly high confidence for IFR conditions at all locations with abundant low level moisture. Surface low pressure will have convection on the increase toward morning at ILM, well depicted by the HRRR model. This precip will likely continue through early afternoon, spreading inland after that. Light mainly northeast flow through midday on Thursday. EXTENDED OUTLOOK...Isolated to scattered afternoon and early evening convection possible underneath the cutoff upper low through Friday. MVFR/IFR morning stratus/fog possible each day through Sunday. && .MARINE... NEAR TERM /THROUGH TONIGHT/... As of 300 PM Wednesday...A deep low over the Cape Fear region will drift southwest through tonight. This will result in a weak pressure gradient with winds 10 knots or less through the day. Wind direction will also be somewhat variable, but in general, an onshore flow will continue as the low center drifts southwest. It should kick back to a more northeasterly direction close the coast on the back end of the low and more E-SE farther off shore on the front end of low. Mid- level dry air over the waters is expected to limit storm development today, but should increase overnight in deeper on shore flow. Seas will remain less than 3 ft mixing in with some longer period SE swells arriving tonight. SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... As of 300 PM Wednesday...Low pressure will weaken south of the waters with trough aligned up the coast through the period. This will keep an on shore flow through the period and depending on the exact position of the trough, the winds will fluctuate between E-SE to E-NE over the waters...remaining 10 kts or less. Winds will turn more northerly and pick up a bit by Fri night as low finally moves off to the east. Showers and isolated TSTMS will remain in the mix. Seas will basically remain 3 ft or less with a slight, slow and steady rise as a longer period up to 12 second SE swells mix in. LONG TERM /SATURDAY THROUGH MONDAY/... As of 300 PM Wednesday...Julia`s remnants should be long gone from the weather map by Saturday. High pressure dropping southward from the southern portion of Hudson Bay will push a cold front through the Carolinas early Sunday. This front will sink to coastal Georgia Monday with easterly winds developing across the Carolinas. Scattered showers should develop mainly behind the front beginning Sunday night. Wave heights of 2-3 feet are expected south of Cape Fear Saturday into the first half of Sunday, with the potential for 3-4 foot seas near and north of Cape Fear due to residual swells emanating from distant Tropical Storm Karl. By Sunday night modest onshore winds will create the potential of shorter period 2-4 foot waves away throughout the area, continuing into Monday. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...TRA NEAR TERM...RGZ SHORT TERM...RGZ LONG TERM...TRA AVIATION...43
Area Forecast Discussion
National Weather Service Northern Indiana
329 PM EDT Wed Sep 21 2016 .SYNOPSIS... Issued at 326 AM EDT Wed Sep 21 2016 There is a slight chance of a thunderstorm early this evening over northwest Indiana and southwest Lower Michigan. Otherwise it will be dry and warm again. Low temperatures tonight will drop into the lower 60s. Partly to mostly sunny skies are expected Thursday with highs once again rising well into the 80s. A weak cold front is expected to drop south later Friday and Friday night. This will bring slightly cooler temperatures for the weekend...but highs are still expected above normal in the middle 70s. The next chance for a widespread rain will not be until early next week. && .SHORT TERM...(This Evening through Thursday) Issued at 324 PM EDT Wed Sep 21 2016 So far upstream convection has behaved as advertised and continues to weaken as it moves east out of deeper instability and away from stronger synoptic forcing. HRRR still wants to occasionally develop an isolated cell in our north through 00z with modest instability and decent mid level lapse rates. So far outflow boundaries have not been strong enough to force any development. Vis sat loop does show some cu trying to develop over the northwest in vicinity of where HRRR has tried to convect. Also watching remnant convection sliding southeast from northern Illinois. Will carry the slight chance pops over the north and northwest through 00z followed by dry conditions for the overnight period as main front lifts north. This boundary now looks to reside far enough north on Thursday that pcpn chances will be 10 percent or less and upstream convective complex tonight over WI to stay north of our area tomorrow. Should still see some cloud debris but expect more sun than today and temps will once again recover nicely well into the 80s. ECE MOS kicking out upper 80s over parts of the region but will hold shy of this in the mid 80s with the potential for the debris clouds at times. && .LONG TERM...(Thursday Night through Wednesday) Issued at 324 PM EDT Wed Sep 21 2016 Upper level pattern to transition from zonal to a meridional flow through the period. This will complicate forecast by early next week with various model solutions revolving around cut off upper low and an occluded front. Backdoor front will begin to slide into the area later Friday and Friday night. Moisture limited and not much synoptic forcing. Slight chance pops continue in the northeast. This boundary will bring northeast winds and cooler temps through the weekend but still above normal for late September. Highs in the middle to upper 70s still expected. More uncertainty exists with potential frontal boundary early next week. GFS and ECMWF continue to have differences with respect to a cut off upper low over the central CONUS and how an occluded front associated with it will translate east. GFS continues to be faster model while ECMWF remains slower. These differences being dictated by large trough off the northeast CONUS and stout ridge between that trough and the developing upper low over northern Plains. GFS wants to push sfc boundary through the ridge while ECMWF stalls this boundary to our west. For now will be using the Superblend init until more certainty develops. Preference is toward ECMWF as GFS has a bias of breaking down ridges and seems to be doing that here as well. Temps remain mild in the 70s but should trend closer to normal next week. && .AVIATION...(For the 18Z TAFS through 18Z Thursday Afternoon) Issued at 135 PM EDT Wed Sep 21 2016 Focus for convection should remain primarily north and west of the local area this period as effects of broad mid level ridge and capping issues persist. Outflow/convective vorts from upstream convection may be enough to support an isolated shower or storm at KSBN late this afternoon, but confidence remains too low for inclusion at this time. Otherwise, light south/southeast winds to become light and variable tonight, and then south-southwest 5 to 10 knots Thursday. Some potential of some shallow fog once again early Thursday morning, but not expecting significant impacts at this time. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ SYNOPSIS...Lashley SHORT TERM...Lashley LONG TERM...Lashley AVIATION...Marsili Visit us at www.weather.gov/iwx Follow us on Facebook...Twitter...and YouTube at: www.facebook.com/NWSNorthernIndiana www.twitter.com/nwsiwx www.youtube.com/NWSNorthernIndiana
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
449 PM EDT Wed Sep 21 2016 .SYNOPSIS... High pressure will build over the region through early Thursday then weaken through Friday. A cold front will move through the area early Saturday. High pressure builds again over the region early next week. && .NEAR TERM /THROUGH THURSDAY/... A few light showers are seen on radar over southern MD and the Fredericksburg area, but these are expected to dissipate early tonight as high pressure builds in and air mass dries out. Biggest question for tonight is whether high clouds will thin out and skies become clear. Latest 12Z ECMWF and HRRR simulated cloud IR imagery show high clouds sticking over the area around much longer than earlier runs with clearing not indicated now until after midnight or early Thu. Fog is not expected as models show sfc dewpoints dropping tonight. A few high clouds still possible Thu if the ECMWF is correct, but any high clouds are likely to be thin enough for a mostly sunny day. High pressure will be in control, although it will be weakening. && .SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/... Weak high pressure in control during this period. Temperatures are expected to warm up into the upper 80s and possibly reach 90F in a few spots on Fri. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... Surface cold front will likely have passed south of the region by Saturday morning, behing pushed along by a 1030+ mb high pressure center originating near Hudson Bay Canada. The center of this high and coolest air will pass over New England, but much cooler weather is expected over the Mid-Atlantic as well especially during the second half of the weekend into early next week. Onshore flow may result in elevated humidity and low clouds and drizzle especially early next week. The operational GFS runs have been the quickest with an approaching cold front next week but have been trending slower towards a GEFS/EC blend. A slower solution seems more likely given the large blocky nature of the high pressure center that will be stationed just northeast of the region next week. This should keep more substantial rain chances at a minimum through much of the forecast period. && .AVIATION /21Z WEDNESDAY THROUGH MONDAY/... VFR conditions next 24 hrs, except for possible 3-5SM mist at KCHO. Mainly VFR expected Saturday with northerly winds 10 to 15 knots. Sub-VFR possible later in the weekend with lower clouds as winds become easterly around 10 knots. && .MARINE... Winds will gust to around 15kt in the lower Bay through midday Thu before they begin to diminish. A pressure surge, aided by northerly channeling, will likely push winds into Small Craft Advisory territory on Saturday. Winds should gradually diminish and veer to the east Saturday night into Sunday. && .TIDES/COASTAL FLOODING... Water levels running less than a foot above astronomical normals, but departures are on the rise. Nonetheless this is proving to be enough to flirt with minor inundation thresholds at senstive locations. Have issued Coastal Flood Advisory for St. Marys and Anne Arundel Counties. We still have a couple of hours to ensure that the current forecast remains on track in the upper tidal Potomac. If it does, we will need to issue for DC/Alexandria as well. Elevated water levels persist through the rest of the week due to low pressure off the Carolina coast. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...Coastal Flood Advisory from 8 PM this evening to midnight EDT tonight for MDZ014. Coastal Flood Advisory until 8 PM EDT this evening for MDZ017. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...LFR NEAR TERM...LFR SHORT TERM...LFR LONG TERM...DFH AVIATION...LFR/DFH MARINE...LFR/DFH TIDES/COASTAL FLOODING...HTS/LFR
Area Forecast Discussion
National Weather Service Twin Cities/Chanhassen MN
411 PM CDT WED SEP 21 2016 .SHORT TERM...(This evening through Thursday) Issued at 326 PM CDT Wed Sep 21 2016 The next 12 hours will feature widespread showers and thunderstorms across a large portion of Minnesota and western Wisconsin. While a few straight-line wind gusts and a weak tornado are not impossible, the two greater threats this evening are heavy rain with the potential for flash flooding and hail between 1-2" in diameter. You don`t have to be a meteorology major to find the main warm front this afternoon in Minnesota. North of a line from roughly Granite Falls, to the southern Twin Cities metro, to Eau Claire there is overcast skies temperatures in the 60s and northwest surface winds. South of this line, the winds are southerly and temperatures are in the 70s and 80s with dewpoints in the 70s. The instability gradient is stretched out along this line with max values near 3500-4000 J/kg (SBCAPE and MLCAPE) in far south central MN and near 0 J/kg in the far northern TC metro. Good elevated instability and steep mid-level lapse rates extends well north of the surface boundary. In addition to the building instability, the 925-850mb moisture transport and warm advection have increased quite a bit over the past couple hours. The FGEN in this area has also increased since mid afternoon. The result has been the expansion of thunder along or north of the boundary. Storms have been efficient rainfall producers with rain rates between 2-3". The storms have also been efficient hail producers as well, not too much of a surprise given the instability in the hail growth zone, shear profile, and due to the fact that the surface temperatures are in the 60s along and north of the boundary. We expect the radar scope to continue to expand in coverage this evening. The placement of the Flash Flood Watch is still looking good, although some of the convective allowing models are developing convection back farther to the southwest. Though the HRRR has admittedly struggled with the short term trends. Settle in, its going to be a busy night for weather in MN/WI over the next 12 hours. There will likely be elevated hail and heavy rain north of the front that move east northeast, but there will also likely be a broken line of storms that form along the boundary and sag south with time. .LONG TERM...(Thursday night through Wednesday) Issued at 326 PM CDT Wed Sep 21 2016 Highly amplified flow in the extended will evolve into a cut off low which is a pattern that has high uncertainty. For that reason and given the high impact weather expected in the next 24 hours, did not stray from blended guidance in the extended period. There`s a few highlights below. The warm front responsible for the heavy rain will be laid out somewhere along I-90. Storms should continue to Thursday night. On Friday the warm front will lift northward and showers and thunderstorm chances will be tied to the front. There will be warm and dry conditions in the warm sector, but this will be short-lived as a cold front moves in Saturday and brings a few showers and thunderstorms. Beyond this period, the upper level wave will cut off and bring a prolonged period of clouds and light rain. As mentioned above, there is uncertainty in this pattern, so would not be surprised if the forecast changes. The GFS is a bit quicker with the cutoff low, but the ECMWF catches up by the middle of next week. && .AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon) Issued at 113 PM CDT Wed Sep 21 2016 This is a messy weather pattern with a lot of moving parts. There is a strong warm front across the area. This runs east to west from KRWF to KMSP to KEAU...along and north of this line winds are out of the northeast and there is MVFR/IFR ceilings. South of this line winds are out of the southeast, conditions are VFR and there is even sunshine. We expect thunderstorms to become more numerous across MN and WI this evening. Thunderstorms with heavy rain are likely at KRNH/KEAU/KMSP and possible at KAXN/KSTC/KRWF. KMSP... Besides the scattered to broken low clouds in the metro. It will be quiet for the next couple hours at the airport. However, we expect a busy evening with widespread storms developing in eastern MN. /OUTLOOK FOR KMSP/ Fri...MVFR/SHRA possible. Wind E 5-15kts. Sat...VFR with MVFR/TSRA likely. Wind SE at 10g15kt. Sun...VFR. Wind W-SW 10g20kt. && .MPX Watches/Warnings/Advisories... WI...Flash Flood Watch through Thursday evening for WIZ024-026-028. Flash Flood Watch through Thursday morning for WIZ014>016-023- 025-027. MN...Flash Flood Watch through Thursday evening for MNZ067-069-070- 074>078-082>085-091>093. Flash Flood Watch through Thursday morning for MNZ051>053- 059>063-066-068. && $$ SHORT TERM...CLF LONG TERM...JRB AVIATION...CLF HYDROLOGY...CLF
Area Forecast Discussion
National Weather Service Portland OR
259 PM PDT Wed Sep 21 2016 .SYNOPSIS...An upper level trough extends from southern BC to the Oregon coast, keeping cool and somewhat unsettled weather across the forecast area. This system will continue to dig south into northern CA tonight before moving across the Sierra Nevada Thursday. A few showers and perhaps a thunderstorm will linger into the evening, but most showers should decrease tonight with the loss of daytime heating. A few lingering showers are possible in the Cascades Thursday, but Thursday should be dry for the most part. The next good chance for widespread rain comes Friday as another moist Pacific frontal system aims toward the Pacific Northwest. High pressure rebuilds over the region for the start of next week. && .SHORT TERM...(Tonight through Saturday)...Visible satellite imagery shows cumulus buildups forming over the higher terrain. This due to an upper trough extending from southern BC to the coastal waters near the OR/CA border, providing relatively cool air aloft for a little bit of instability. 21z RAP surface analysis shows a couple hundred J/kg of sfc-based CAPE across much of NW Oregon, with only a small amount of CIN - mainly closer to the north coast. With little to no convective inhibition, expect showers to continue to develop mainly over the higher terrain this afternoon. Convective allowing models suggest there is a chance that a couple of these showers could form or drift over the Willamette Valley, so we left a mention of showers into this evening for all but our northern coastal zones. With some model soundings showing the potential for deeper convection with tops >20kft, cannot rule out a couple lightning strikes from the heavier showers. Kept the thunder mention limited to the higher terrain south of a Newport-Mt Hood line, where instability should be most ripe for convection. With model soundings showing very little wind up to 500mb, expect little to no storm motion with any cells that develop. As a result, it appears any convection would be the pulse variety, lasting 30-60 min or less and dumping a localized burst of rain. In other words, expect hit-or-miss showers this afternoon with the better chance being in the higher terrain south of Portland. Most showers should diminish quickly with the loss of daytime heating, though there is some potential showers or rain will continue over the Cascades as the upper trough axis passes through later tonight. If skies remain clear enough, expect another cool morning with areas valley fog Thursday...similar to the past couple mornings. Models then show decent agreement that our upper trough will evolve into a closed upper low over the Great Basin by Thursday afternoon. Drier northerly flow behind this system will likely result in less shower coverage Thursday, and mainly over the Cascades. Temperatures could be a bit tricky Thursday afternoon, as a lot may depend on how quickly any valley fog/low clouds can burn off. The air mass aloft remains cool...with 850 mb temps generally around +5 deg C across the forecast area per the latest NAM/GFS runs. Suspect that either way, temperatures will struggle to break out of the 60s Thu... perhaps a couple spots will reach the lower 70s. Thursday night should start off clear to partly cloudy and cool due to shortwave ridging, so some valley locations could see some fog develop before high clouds increase in advance of the next Pacific frontal system. This could result in a dreary day Friday with temps struggling to get much above 60 degrees. The incoming system is showing a good tap into tropical moisture at the moment, with precipitable water (PW) values in excess of 2 inches embedded within. While the splitty flow pattern will probably keep the deepest moisture plume from affecting our area, it does appear enough moisture will hang on to provide some decent isentropic lift over our existing cool air mass. This should be enough for at least some rain, so we bumped up our PoPs into the likely category Friday. Rainfall amounts will probably be modest, as the split-flow pattern will keep the best jet dynamics out of our forecast area. 18z NAM does still hold the front together enough for some gusty winds on the beaches and headlands Friday morning. Any rain should gradually come to an end Friday night and Saturday as models show good agreement in having a strong upper ridge build north across the Pac NW from California over the weekend. While 850mb temps warm up very quickly in this pattern, we will need to keep an eye on valley inversions possibly keeping temperatures cooler than they otherwise would be. Especially if we receive additional rainfall, night and morning valley fog may be stubborn... we are getting to that time of year. Autumn starts at 7:21 am local time tomorrow morning. Weagle .LONG TERM...(Saturday night through Wednesday)...Ridging and high pressure will dominate Sunday and Monday, with offshore winds keeping Southwest Washington and Northwest Oregon sunny and dry. We`ll see temperatures jump up above normal as well, with highs in the low-to-mid 80s in the Willamette Valley and 70s along the Coast. By Tuesday, the ridge starts to flatten as it starts to get pushed off to the east by an approaching trough. Tuesday will probably be a transition day with clouds returning to the Coast, but inland should remain mostly sunny a bit cooler. Trough should at least bring cooler, more typical Fall weather for later next week, if not a little bit of rain to far northern portions of our area. -McCoy && .AVIATION...Upper low will gradually shift over the region tonight and early Thu, but not much in way of moisture. Will see cumulus clouds and even a few isolated showers, mainly over Oregon Cascades and Coast mtns. Instability not great, but could be enough to trigger an isolated thunderstorm over the Oregon Cascades until 03z tonight. Mix of clouds and clear skies tonight but think will see increasing MVFR along the coast and the interior again later tonight as onshore flow increases a bit. KPDX AND APPROACHES...VFR with a few cumulus, May see an isolated shower or two, but best threat will be to east over the Cascades. Generally dry overnight and Thu, but will have increasing MVFR after 10z as onshore flow increases.Rockey. && .MARINE...Weak high pressure over the coastal waters will maintain overall northerly winds at 15 kt or less through Thursday, with west swell 4 to 6 ft. A moderately strong cold front will approach later Thu night and Fri, and move across the waters late Fri am into the early afternoon. Will see southerly winds increase, with gusts 25 to 35 kt expected. No advisory for those winds at this time, but will likely hoist Small Craft Advisory or possibly a Gale Watch on Thu. Winds and swell will push combined seas to around 10 ft on Fri, with seas gradually subsiding Sat. High pressure returns for the rest of the weekend, with northerly winds generally 10 to 20 kt. && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...None. && $$ Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland This discussion is for Northwest Oregon and Southwest Washington from the Cascade crest to 60 nautical miles offshore. The area is commonly referred to as the forecast area.
Area Forecast Discussion
National Weather Service Pueblo CO
332 PM MDT WED SEP 21 2016 .SHORT TERM...(This evening through Thursday) Issued at 255 PM MDT Wed Sep 21 2016 ...A Warm and Breezy Thursday... Current water vapor imagery and upper air analysis is indicating moist southwest flow aloft across the state, as remnant moisture from tropical system Paine continues to lift out across the region. Water vapor imagery is also indicating drier air embedded within the flow across the Desert Southwest moving into western New Mexico and western Colorado, ahead of an upper trough digging across the West Coast at this time. Regional radars indicating isolated to scattered showers lifting north and east across the region, with a few thunderstorms across northwestern New Mexico at this time. Tonight and tomorrow...Latest models remain in fairly good agreement with southwest flow aloft slowly increasing across the region through the day tomorrow, as digging upper trough across the West Coast carves out an upper low across the Great Basin tomorrow afternoon. With that said, should continue to see showers with a few embedded thunderstorms moving across the area through the rest of the afternoon and into the early evening, with HRRR remaining consistent with the best coverage of storms being across the Pikes Peak region and the Raton Mesa region into Baca County. Showers and storms to diminish through the late evening, with loss of solar heating. However, could see some showers developing across the ContDvd and especially the southwest mountains, into early tomorrow morning, with increasing orographic flow. Overnight lows to be at or above seasonal average, especially across the eastern plains, where lee troughing will keep breezy southerly winds across the far se plains overnight. Will see more sun across the area early tomorrow, and with the increasing flow aloft and lee troughing across the plains, should see breezy southerly winds mixing across the area through the late morning and afternoon. Mid and upper level moisture slowly increases across the area again ahead of the Great Basin system, along with southerly low level winds across the plains keeping low level moisture in place, owning to another round of isolated to scattered afternoon showers and storms, with the best coverage over and near the higher terrain. Models continue to suggest near record high temperatures in the 80s to lower 90s across the plains for tomorrow, with highs in the 60s and 70s across the higher terrain and mainly 40s and 50s at the peaks. Current records for tomorrow are 85F at ALS...88F at COS and 93F at PUB. .LONG TERM...(Thursday night through Wednesday) Issued at 255 PM MDT Wed Sep 21 2016 ...Critical Fire Weather conditions I-25 corridor...Severe thunderstorm potential eastern plains...and snow possible higher mountains Friday... Western U.S. upper low will move across the Great Basin Thursday night before lifting northeastward into WY and MT Friday and Friday night. Deep southerly flow across the plains will advect 50 dewpoints northward into the southeast plains Thurs night into Friday morning. Initially will see some showers confined to the mountains Thurs night and Fri with snow levels down to around 12kft at times along the continental divide. Dry air moves in Friday afternoon as the trof axis moves across...which shallows out the moisture along the continental divide. By this time...westerly winds will be spreading eastward into the plains...sharpening up a dry line just east of the I-25 corridor. All areas will see gusty west to southwest winds west of the dry line...and gusty southerly winds to the east of the dry line. CAPE values could be up to around 1000 J/kg (according to the NAM12) with deep layer shears around 30-40 kts. This will lead to a potential for severe thunderstorms across the eastern counties including...Kiowa... Bent...Prowers and Baca. Severe wind gusts and large hail will be the primary storm threats. To the west...RHs dropping to around 15 percent...and the dry fuels will combine with gusty winds up to 40 mph to create the potential for critical fire weather conditions Friday afternoon and evening along the I-25 corridor. There are still some questions as to the position of the dry line and how low surface dew points will drop...however NAM12 seems too moist which is its bias...and have leaned grids towards the drier GFS and EC solutions for locations west of the dry line. For now have restricted the Fire Weather Watch to the southern I-25 corridor and a couple counties bordering to the east...but its possible that the watch may need to be expanded northward and eastward a bit more. Will let later shifts make any needed adjustments. As the trof axis lifts out to the north Friday night...should see drying conditions from west to east overnight. Any snowfall into the mountains looks brief and relatively light...with spotty amounts of an inch or two possible above 12kft. The San Luis Valley could see a fairly widespread hard freeze Friday night. While the main upper low lifts off to the northeast...more energy digging into the base of the trof across CO will keep generally unsettled weather over the region through the weekend. A cold front will drop through the region on Saturday with another surge of colder air for Saturday night. Models keep majority of precipitation across the southeast mountains and adjacent plains where H7 temperatures dropping to 0 to -2C could drive snow levels down to 9kft or a tad lower Sat night and again Sunday night. EC and GFS differ with QPF during these periods...with EC on the wetter side. Hard to say at this point how much snow will fall across the southeast mountains...but at this point a few inches of wet snow across the higher elevations look possible as GFS has trended back towards a wetter solution. Models shift the upper low eastward into the plains early next week...though differ with the track as GFS keeps the upper low center to the north across the Dakotas through Wed...while ECs track is farther south. Either way...CO is on the back side of the system with drier but cooler northerly flow. This will keep below normal temperatures across the region through the longer ranges. -KT && .AVIATION...(For the 00Z TAFS through 00Z Thursday evening) Issued at 255 PM MDT Wed Sep 21 2016 VFR conditions expected to persist at COS, PUB and ALS over the next 24 hours. Monsoonal moisture embedded within the west to southwest flow aloft will keep scattered showers and thunderstorms in the forecast across the higher terrain with more isolated storms possible across the lower elevations through the evening, though probability of storms affecting terminals too low to include in TAFs. Breezy south to southwest winds of 15-20kts expected at terminals through the evening. Less cloud cover expected tomorrow morning, with breezy south to southwest winds and isolated afternoon showers and storms again possible at the terminals. && .PUB Watches/Warnings/Advisories... Fire Weather Watch from Friday afternoon through Friday evening for COZ227>232. && $$ SHORT TERM...MW LONG TERM...KT AVIATION...MW
Area Forecast Discussion
National Weather Service Blacksburg VA
303 PM EDT Wed Sep 21 2016 .SYNOPSIS... An upper low will meander across the eastern Carolinas through Thursday before finally weakening and shifting offshore by the end of the week. High pressure will gradually build in from the west Friday into Saturday. A backdoor cold front drops south through the area late Saturday into Saturday night followed by cooler high pressure Sunday into early next week. && .NEAR TERM /THROUGH THURSDAY/... As of 245 PM EDT Wednesday... Closed low over the Southeast Coast will continue to interact with the Post tropical remnants of Julia during the period. As been the case for a couple of runs, the ECMWF and NAM remain slightly west of the GFS. One of the forecast challenges is the western edge of the moisture and the sharp gradient in showers. The HiResw-arw-east, wrf-arw-rnk, RAP and HRRR support the mention of isolated to scattered showers in southeast portions of forecast area this afternoon into tonight. The upper low remains fixed across the coastal Carolinas tonight into Thursday morning. believe that shower coverage may wrap tighter towards the coast tonight with drier air pushing into northwest portions of forecast area. Cloud cover tonight will vary from clear in the northwest to cloudy in the southeast. Lows tonight will range from the mid 50s in the northwest mountains to the mid 60s in the east. The closed upper low will slowly weaken and lift northeast on Thursday. The result of this transition will be even less coverage of isolated showers across the south and southeastern portion of the region. High temperatures Thursday will vary from the mid 70s in the mountains to the lower 80s in the Piedmont. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/... As of 230 PM EDT Wednesday... Persistent upper low will finally open up and shift northeast Thursday night in response to ridging nudging east from the Midwest. However may still be enough moisture around with the deformation axis on the back of the coastal system to produce a few added showers far southeast so left in an isolated mention early. Otherwise expecting a drier northerly flow to take shape under weak high pressure later Thursday night into early Saturday. This should bring clearing/sunny skies for late week into the weekend. However passing 500 mb trough well to the north by Saturday will propel a backdoor cold front toward the area Saturday afternoon and into parts of the region Saturday night. This a bit slower than previous given strong upper ridging overhead and warmth ahead of the front that should slow it down until Saturday night. Other than perhaps some developing post frontal low level cloudiness by late Saturday per the GFS, deep moisture to remain limited so not including any pops with the boundary for now. Given gradual 850 mb warming Friday and weak compression ahead of the front Saturday, looks like will return to above normal highs with mostly low/mid 80s both days with most surface based cool advection holding off until Saturday night at this point. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 130 PM EDT Wednesday... High amplitude blocky pattern looks to evolve later in the weekend into next week as potential cut off upper lows develop off New England and across the upper Midwest. This could basically sandwich the area within a sharp shortwave ridge axis between these two features pending exactly where the upper block develops. Differences between models continue in regards to strength of the upper systems and subsequent speed of surface features in this setup. However still appears will see a rather significant backdoor cold front drop south into the region by Saturday night/early Sunday before the boundary fades crossing into the Carolinas. Guidance still suggests some spotty shower potential Sunday with the front aloft nearby and developing onshore flow. Thus thinking more clouds and spotty shower pops Sunday and southern sections Sunday night with a shallow moisture axis lingering but iffy. Lots of uncertainty to take shape early next week as model spread remains large in just how fast a second cold front to the west will be able to slide east given eastern ridging in place. Latest 12Z GFS has continued to make a shift toward the slower ECMWF from overnight in keeping this slow moving front west of the mountains through midweek. However these solutions remain much slower and stronger than the GEFS which looks too weak/fast in lifting support out to to the north, while spilling the front quickly east. Overall the slower scenario would keep the area in more or less a more stable low level wedge formation per high pressure to the north under ridging aloft. Tendency in this setup likely to lead to more clouds and spotty showers/drizzle including much cooler temperatures into midweek. Therefore have trended in this direction with highs below Mos, but still mostly 70s and lows 50s- mid 60s, although highs by early week could be only in the 60s if more widespread low clouds do materialize. && .AVIATION /19Z WEDNESDAY THROUGH MONDAY/... As of 108 PM EDT Wednesday... Scattered to broken MVFR clouds with patches of showers mainly east of the blue ridge this afternoon into tonight. Northeast winds may be breezy this afternoon into this evening with gusts to 20kts along and east of the Blue Ridge Mountains. Winds will become light easterly tonight into Thursday morning. Tonight the skies will clear from northwest to southeast to a point, but remain broken at the high cloud level overnight in the DAN area. Model forecast soundings with easterly flow suggest potential for low cloud development or advecting in from the east along with patchy fog. Will keep it optimistic and go no lower than MVFR at LYH/DAN/BLF/BCB on vsbys with IFR/LIFR at LWB late tonight. Morning fog and low clouds will lift by mid morning, return all taf sites to VFR conditions by Thursday afternoon. Winds Thursday afternoon will be light and variable. Medium to high confidence in ceilings,visibilities and winds during the taf period. Extended aviation discussion... The slight chance of MVFR showers will remain just east of KLYH and KDAN through Thursday night. VFR conditions will prevail Thursday night outside of late night/early morning fog/low clouds. GFS/ECMWF have been consistent in filling and lifting out the low to the northeast on Friday. VFR conditions will prevail on Friday. A back-door cold front will come through the Mid-Atlantic region on Saturday. High pressure will build in for Sunday. The chance of precipitation or any sub VFR conditions will increase through the day Sunday and into Sunday night. Next cold front arrive by Midweek with potential for MVFR/IFR conditions. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH/RAB/WP NEAR TERM...KK SHORT TERM...JH LONG TERM...JH AVIATION...KK/WP