Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/09/19


Area Forecast Discussion
National Weather Service Charleston SC
1030 PM EDT Mon Apr 8 2019 .SYNOPSIS... A storm system will affect the area through Tuesday night before shifting offshore. High pressure will then return into late week with a weakening cold front moving into the area late this week. Another storm system will affect the area early next week. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... As of 1020 PM: Temperatures off the CHS waters were observed in the upper 60s, matching the water temps. HRRR condensation pressure deficits across the CHS waters will remain near zero this evening into the late night hours. I will update the forecast to add a mention of patchy fog across AMZ350 and 352. As of 9 PM: I will issue a quick update to remove mention of TSRA west of the convection line this evening. In addition, I will align temperatures with recent observations. As of 815 PM: Latest SPC mesoanalysis indicated that area upstream of the band of showers and thunderstorms has develop SBCIN. However, lingering elevated instability and the passage of outflow boundaries should continue to develop rounds of convection through late evening. The area in the wake of the convection has been worked over and additional convection will be limited to isolated coverage. I will update to time the line to lift across the remaining forecast area, with only SCHC PoPs into the late night hours. Another round of convection is expected around sunrise Tuesday. As of 740 PM: KCLX indicated a band of showers and thunderstorms over the middle of the forecast area. The convection will pass across the northern CWA by late evening. The environment will not favor any strengthening of the convection, but the activity will hold together over the rest of the land zones. As of 610 PM: KCLX indicated a line of thunderstorms with pockets of 40 KT inbounds, approaching the Savannah River from the SW. Two fine line boundaries were starting to intersect over the Savannah River Valley, triggering a few new updrafts. Weak values of CAPE and DCAPE do not support any strengthening of the convection as it tracks NE. However, it does appear that the convection will persist across most of the forecast area. I will update the forecast to adjust PoP and WX. Previous Discussion: A trough, upper low, and associated surface low initially over the Southern MS Valley will move eastward, reaching Alabama by daybreak Tuesday. Deep moisture will be in place ahead of the front with PWATs exceeding 1.5". SPC Mesoscale Analysis shows instability in place with MLCAPEs 1,000 J/kg far inland. However, across a good chunk of our area, especially closer to the coast, there remains some CIN. This is verified by the lack of cumulus clouds on satellite imagery. So capping remains in place late in the day and could continue make it difficult for storms to initiate closer to the coast. Further inland, especially outside of our area, storms are ongoing and in a more favorable environment. CAMs still show this main line of showers and thunderstorms moving into our inland counties first, then gradually moving eastward towards the coast. It should make it towards the GA coast early in the evening and the SC coast later in the evening. The threat for severe thunderstorms with damaging wind gusts continues through this evening. Following sunset, a stabilizing atmosphere will cause the threat of storms to decrease. Though, showers could persist until daybreak Tuesday. It will be a mild night with low temperatures flirting with record high minimums at both KCHS and KCXM (see the CLIMATE section below). && .SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/... Moderate to high confidence this period. A cold front will approach from the west Tuesday and then shift through the area Tuesday night followed by drier high pressure Wednesday and Thursday. Abundant moisture and forcing will be in place ahead of the front Tuesday into Tuesday night to produce numerous showers and scattered thunderstorms given plenty of instability. Could see a round of showers and storms push through in the morning with another round later in the day. Some of the storms could even become severe with damaging winds and/or large hail, especially in the afternoon. Temperatures should be above normal through the period, especially lows. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... Models are in good agreement regarding the synoptic setup in the long term period. A weakening cold front will approach from the west on Friday and likely linger over or near the area Saturday. Meanwhile, another low pressure system will organize over the Deep South. As it approaches late weekend, the stalled front will lift back north as a a warm front. The low and an associated cold front are progged to cross the area on Monday. Highest rain chances will be Sunday into Monday. Temperatures through the period will be above normal. && .AVIATION /03Z TUESDAY THROUGH SATURDAY/... Prior to the 0z TAFs, remnants of a thunderstorm was over KSAV, I will initialize the TAF with -TSRA until 1Z. The line of convection upstream of KCHS is expected to pass over the terminal between 1Z-3Z, highlighted with a TEMPO for SHRAs and MVFR ceilings. Forecast soundings and MOS indicate the MVFR ceilings will develop during the pre-dawn hours and remain until mid-morning. The CAM consensus indicates that a round of showers and storms may reach KCHS after sunrise and a round reaching KSAV during the early afternoon, highlighted with a PROB30. I will time gusty SW winds to develop by mid to late morning. Extended Aviation Outlook: Restrictions likely Tuesday night, possibly IFR, due to showers/thunderstorms/low clouds. && .MARINE... Until Sunset: Wind gusts in the Charleston Harbor are occasionally reaching 25 kt late this afternoon. Since most of the gusts are remaining under this threshold and because conditions will improve in 2-3 hours, we`re opting to not issue a Small Craft Advisory. This Evening: Strong or potentially severe thunderstorms could impact the marine area this evening. Damaging winds can occur in a few of the storms, along with frequent lightning and very heavy rains. Overnight: A storm system will approach from the lower MS Valley. Conditions are expected to remain below Small Craft Advisory levels. Though, seas in the GA waters beyond 20 nm could approach 5 ft. Tuesday through Saturday: A cold front will approach Tuesday and then move through Tuesday night followed by high pressure through mid week. A weakening/stalling cold front will then move into the area Friday night/Saturday. Winds/seas will be elevated much of the time and could reach marginal Advisory levels for a portion of the waters at some point, especially beyond 20 nm. Sea fog and strong wind gusts from thunderstorms could be an issue into Tuesday night. && .CLIMATE... Record high minimums for April 9... KCHS...67F set in 1999. KCXM...68F set in 2015 and previous. KSAV...70F set in 1999. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...NED SHORT TERM... LONG TERM... AVIATION...NED MARINE...SPR CLIMATE...
Area Forecast Discussion
National Weather Service Grand Rapids MI
1001 PM EDT Mon Apr 8 2019 LATEST UPDATE... Marine .SYNOPSIS... Issued at 314 PM EDT Mon Apr 8 2019 - A shower or storm possible north of M-46 this evening. - Dynamic system to bring rain/snow/thunder to Lower Michigan Wednesday night through Thursday night. - Accumulating snow possible north of I-96 Wed night/early Thursday. - Thunderstorms possible Thursday night. && .UPDATE... Issued at 801 PM EDT Mon Apr 8 2019 A narrow line of thunderstorms continues to head toward the west shores of Lake Michigan (WI side of lake) as I write this. The HRRR and HRRRX show the line moving across the lake before slowly weakening as it moves inland of US-131. The showers get as far south as Grand Rapids just before midnight. The instability helping these storms is limited but this does have strong dynamic forcing. I increase the pop to likely north of Grand Rapids early tonight and to around 50 pct near Grand Rapids due to this. Another aspect to this is the high res models continue to show wind gusts to 30 to 40 mph just behind the cold front as it crosses our area after midnight so most areas will have gusty winds during the early morning hours. && .DISCUSSION...(This evening through next Monday) Issued at 314 PM EDT Mon Apr 8 2019 Several storm systems may lead to impacts around the region through the period. The first system arrives tonight. A deepening low pressure system will track eastward through Northern Lower Michigan tonight. This compact system will send a cold front southeastward through the CWA. The wind at 925mb/850mb increase considerably as the front drops in...potentially supporting several hours of gusty winds. We will maintain the localized powers outage risk in the hazardous weather outlook. With some leftover instability still around this evening a few storms could occur mainly to the northwest of Grand Rapids. Any stronger storm could support a risk for over 40 mph winds. A reinforcing shot of cold air arrives Tuesday afternoon with potentially a few rain showers. As the next low pressure system nears from the west on Wednesday a warm front will lift into the CWA and remain there for Wednesday night. Favorable upper level divergence is forecasted along this frontal zone as a couple jet is seen along with decent FGEN. Forecast soundings support snow with the steadier precipitation...although it may take a few hours to change it over to snow as it arrives Wednesday afternoon. With surface temperatures near or above freezing impacts should be limited somewhat but the precipitation could be moderate to heavy with stronger lift possible. This would allow for an increased risk for accumulations on the roads. Most models show several inches of accumulation possible especially along and north of a Muskegon to Grand Rapids to Lansing line and we will keep that in the forecast. We sent out a weather message earlier on this. South to southwesterly low level wind fields increase considerably Thursday into Thursday night with better than 50 knots likely up around 850 mb. Any deeper mixing could support rather gusty winds with some potential for impacts. Guidance supports the cold front pushing through Thursday night. Along and ahead of this front rather numerous showers and thunderstorms are likely to occur. Some of the rain could be heavy especially with PWAT values topping 1.25 inches...although the duration may limit the total amounts. Thus the flood risk looks somewhat limited at this point...especially with a mid level dry slot following this front. The low pressure system lifts through Lower Michigan on Friday. With a trowal pulling in from the west on the backside of this surface low...conditions should turn unsettled again. Another low pressure system is shown to track up the Ohio Valley on Sunday. Uncertainty exist with how far north and west the precipitation field will exist. Based on the latest model trends there is some potential for snow from this system. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 801 PM EDT Mon Apr 8 2019 There currently is a line of thunderstorms over eastern WI just ahead of the cold front heading this way for the overnight hours. I expect the line will hold together enough to impact the GRR and MKG taf sites but not the others. This would be in the 02z to 04z time frame. A thunderstorm is not expected but would not be out of the question either. The front will bring gusty winds behind it. The will likely be 12 hour or so period of winds gusting to around 25 knots behind the front (06z to 18z ) at all of the TAF sites. It would not be out of the question that at MKG (being close to the lake shore and the assoicated convection winds may gust to 35 knots briefly as the front comes through (03z-05z time frame). The low clouds (MVFR) are expected to mostly stay north of our TAF sites but MKG is on the south of edge of the lower clouds behind the front. So more than likely they would have several hours of MVFR cigs during the mid morning hours of Tuesday (as the really cold air moves back in). All TAF sites on the GRR CWA will see at least VFR cigs behind the cold front until enough dry air moves in during the mid to late afternoon to clear the clouds out. && .MARINE... Issued at 1002 PM EDT Mon Apr 8 2019 Based on the latest web cams and our nighttime microphysics image loops the fog has mixed out over our near shore waters so I have expunged the Fog Advisory. The small craft advisory looks good so I made no changes there. && .GRR WATCHES/WARNINGS/ADVISORIES... MI...None. LM...Small Craft Advisory until 8 AM EDT Tuesday for LMZ847>849. && $$ UPDATE...WDM SYNOPSIS...MJS DISCUSSION...MJS AVIATION...WDM MARINE...WDM
Area Forecast Discussion
National Weather Service Huntsville AL
851 PM CDT Mon Apr 8 2019 .NEAR TERM...(Tonight) Issued at 851 PM CDT Mon Apr 8 2019 Near-term focus is on the convection moving north along the MS-AL border. Although most of N AL is more stable than areas farther SW, SPC & RAP data suggest sufficient instability for the storms to maintain themselves (if not with a modest weakening trend). There is relatively little shear, especially in the low levels, so it will take some extra assistance in the form of a boundary to get tornadogenesis. So the severe weather threat appears focused on hail and wind. The forecast from this afternoon called for PoPs and storms to spread east overnight as the parent upper low swings NE towards the TN Valley. This still looks reasonable though near-term guidance is still not handling ongoing weather very well. The severe threat will diminish as storms spread east into markedly more stable air. .SHORT TERM...(Tuesday through Wednesday) Issued at 332 PM CDT Mon Apr 8 2019 Not much cold air is being brought south behind this storm system overnight, so highs tomorrow should still be very warm as sunshine returns in the afternoon hours. Mixing of very warm air aloft in the afternoon should allow highs to climb into the mid 70s to around 80 degrees west of I-65. The southern edge of an area of high pressure builds southward into the area Tuesday night into Wednesday. .LONG TERM...(Wednesday night through Sunday) Issued at 332 PM CDT Mon Apr 8 2019 Some drier air via northerly flow in the boundary layer, lighter winds overnight, and clear skies should allow temperatures to drop into the mid 40s to lower 50s by daybreak on Wednesday. During the day, strong ridging aloft and mixing of warm temperatures at 925 mb should allow highs to climb even higher on Wednesday into the upper 70s to lower 80s. Thursday looks warm as well, but high temperatures may be tempered by cloud cover a bit more. Highs in the upper 70s to lower 80s look reasonable. As strong storm system moves from the upper Midwest into the Great Lakes region, there may be enough moisture convergence and and lift to produce an area of showers and scattered thunderstorms along/ahead of a trailing cold front from this system. Models diverge a bit on how quickly this activity moves east of the area. Kept close to blend for now, but moved precipitation into Georgia Friday afternoon. Southwest flow continues behind this front, so not expecting much change in temperature trends into the weekend. However, another storms system might bring a more substantial round of showers and thunderstorms to the Tennessee Valley. This could be a round of heavier rainfall and stronger storms. However, this is too far out in the forecast to say much more. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 658 PM CDT Mon Apr 8 2019 Mostly light showers will stick around for the next few hours, moreso at KHSV than KMSL. It will take several hours for thunderstorms to reach both locations, if they hold together. Timing of storms is mostly based upon extrapolating the current storms over NE MS and W AL, so this could require additional amendments. Once the storms move through, expect a long period of IFR or near-IFR ceilings for most of the overnight into early Tuesday. Ceilings should lift somewhat mid to late morning as the low pressure system moves to the east. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...BCC SHORT TERM...KTW LONG TERM...KTW AVIATION...BCC For more information please visit our website at weather.gov/huntsville.
Area Forecast Discussion
National Weather Service Lubbock TX
605 PM CDT Mon Apr 8 2019 .AVIATION... VFR next 24 hours. && .PREV DISCUSSION... /issued 252 PM CDT Mon Apr 8 2019/ DISCUSSION... RAP IR analysis this afternoon shows a ridge of high pressure building over the Four Corners region and slowly moving eastward. This ridge will be impacting our temperatures tomorrow with a significant warmup expected. The ridge axis during the afternoon will generally be oriented diagonally across our forecast area, placing the highest temps across the southwestern South Plains. There`s not much more to say than it`ll be a mighty warm April day. So, let`s move on to the headliner of the week...Wednesday. In the wake of the ridge moving to the east, a potent upper level low is poised to take a similar track to our last major wind storm...right across southern CO into eastern KS. The GFS currently has this one pegged to reach a minimum central pressure of 539mb as it passes directly north of us. This is a classic high wind set-up. We`ll be mixing well in the afternoon - to around 600mb (roughly 65KT winds at that height, 60KT still at H700). A speed max of 100KT at H500 is set to pass right over us Wednesday afternoon and early evening, further supporting a high wind event. Thus, we have issued a High Wind Watch for Wednesday from 15Z until 3Z Thursday. The obligatory blowing dust has been included in the grids...it`s West Texas. The other unfortunate by-product of high winds this time of year is Fire Weather. We do acknowledge that we received wetting rains over the weekend, which helps, but by no means erases the fire threat with such high winds. A Fire Weather Watch has been issued for Wednesday from 16Z until 3Z Thursday. See more below in the Fire Weather Discussion. As the low departs, a strong cold front will be pulled through, which will not only bring us colder temps, but more winds. Pressure rises on the order of 3-6mb (5-7mb if you go with the NAM) will keep winds elevated, especially across our northeastern counties through mid-morning Thursday. Another system develops for the weekend that could bring precipitation to the area, and for now, we mostly went with the Blend output until models firm up more on the timing, track and strength of this system. FIRE WEATHER DISCUSSION... A Fire Weather Watch has been issued for all of the Lubbock Forecast Area beginning Wednesday 16Z until Thursday 3Z. Though substantial wetting rains were received across the Rolling Plains this weekend and transitional seasonal greening grass is present across eastern half of forecast area, ERC levels are high enough that initial attack fire activity is likely across at least the Rolling Plains. With cured grass across western half, significant fires become more likely with winds in the 50KT range, gusting 70mph. && .LUB WATCHES/WARNINGS/ADVISORIES... Fire Weather Watch from Wednesday morning through Wednesday evening for TXZ021>044. High Wind Watch from Wednesday morning through Wednesday evening for TXZ021>044. && $$ 99/99/26
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
923 PM EDT Mon Apr 8 2019 .SYNOPSIS... Weak low pressure will pass south of the area tonight. A cold frontal passage on Tuesday will yield to high pressure building back over the area by Wednesday and Thursday. Another area of low pressure will track toward the Great Lakes region once again, pushing a cold front on our doorstep Friday. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... A surface trough axis has moved off to the east this evening, taking convection with it. There`s still some mid level vorticity moving across the area, so while drying is taking place in the subsidence in the wake of the convection, some additional showers aren`t out of the question (one is located near Frostburg at this writing). Also, the HRRR and RAP have been indicating a weak low passing to our southeast could help spread a few showers back northward. However, these models have been backing off, and this may be the reasonable solution given the current organized and progressive nature of the convection. Southern Maryland would be most susceptible to additional showers. Some patchy fog is possible overnight, especially in locations that saw rain. However, am not seeing any strong signals for widespread fog...and continued mid/high level clouds overnight should help mitigate the threat as well. With minimal cold advection, it will be another very mild night, with most locations in the 50s. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/... A secondary cold front will cross the region Tuesday afternoon and evening. There will be less moisture associated with this frontal passage, however some gusty showers and a few isolated thunderstorms are possible, especially north/east of the Washington DC metropolitan area. Highs will range in the mid to upper 70s. High pressure will then begin building into the region Tuesday night and through Wednesday bringing dry conditions and seasonable temperatures. Highs Wednesday in the low to mid 60s. Lows in the 40s Tuesday night and Wednesday night. && .LONG TERM /THURSDAY THROUGH MONDAY/... A warm front will shift northward across the area on Thursday in response to an intense area of low pressure developing over the center of the country. No precipitation is expected as this front lifts northward, but some clouds will be possible. Seasonable temperatures are expected, with highs in the 60s for most locations. The aforementioned area of low pressure will track northeastward toward the Great Lakes Thursday Night into Friday. As the storm`s parent mid-upper level trough tracks eastward, forcing for ascent in advance of the trough will spark the development of showers and thunderstorms Friday afternoon and evening. Low-level moisture return in advance of the system will be relatively limited, with dewpoints only in the upper 50s. As a result, CAPE values will be relatively low, with most guidance showing under 500 J/kg of MLCAPE. However, the wind field looks very impressive, with a 40- 50 kt low-level jet and 60 kts of 0-6 km shear. Despite the meager instability, well organized thunderstorm activity is still possible (potentially in the form of a QLCS) given the strong forcing forcing for ascent and high shear environment. Some of these storms could potentially be on the stronger side, especially if we were to get more low-level moisture return than currently modeled. However, at four days out there is still plenty of time for things to change. Any leftover storms will exit the region Friday Night. High pressure will build in for Saturday and Saturday Night, bringing dry conditions. The next chance for rain will come Sunday into Sunday Night as a trough and associated area of low pressure approach from the southwest. This system will originate more from the southern stream, and have a higher moisture environment associated with it. As a result, higher precipitation totals may be possible compared to the system on Friday. && .AVIATION /01Z TUESDAY THROUGH SATURDAY/... The threat of thunderstorms is over at the TAF sites, and it`s possible the same can be said about rain, given subsidence and minimal low level moisture/forcing in the wake of the convective system. The only other threat for the remainder of the night will be patchy fog. However, there`s not a strong signal in model guidance, and continued mid-high level cloudiness may limit the potential as well. CHO (previous rain) and MTN (higher humidity near the water) may be slightly more susceptible. A secondary dry cold front will pass through the area Tuesday afternoon and evening with a few showers and isolated thunderstorms possible at DCA/MTN/BWI. High pressure will then build across the terminals through Tuesday night through Wednesday night, resulting in light northerly winds, dry conditions and VFR. VFR conditions are expected on Thursday. Conditions may deteriorate to sub-VFR on Friday as a system approaches from the west. && .MARINE... Winds are diminishing on the waters this evening as thunderstorms have exited the area. It`s looking likely the remaining Small Craft Advisory will be able to be cancelled early. Some patchy fog may develop overnight, and winds should remain 10 kt or less. A cold front will move across the area Tuesday afternoon and evening, and a SCA has been issued for the northern Chesapeake Bay for northerly winds behind the front. An extension in time and area is possible, with winds near threshold values much of Tuesday night into Wednesday morning. High pressure will settle over head Wednesday afternoon and Wednesday night, with lighter winds expected. SCA-level winds appear possible on Thursday and Friday in southerly flow. Special marine warnings may be needed Friday afternoon and evening as thunderstorms cross over the waters. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory from 3 PM Tuesday to midnight EDT Tuesday night for ANZ530>532-538>540. Small Craft Advisory until midnight EDT tonight for ANZ534-537- 543. && $$ SYNOPSIS...MM NEAR TERM...ADS SHORT TERM...MM LONG TERM...KJP AVIATION...ADS/MM/KJP MARINE...ADS/MM/KJP
Area Forecast Discussion
National Weather Service Nashville TN
751 PM CDT Mon Apr 8 2019 .UPDATE... FOR EVENING DISCUSSION. && .DISCUSSION... Many of the earlier showers that were affecting Middle Tennessee have dissipated, with only spotty echoes showing up on radar this hour. A surface low will slide by to our south as an upper trough pushes across the mid state overnight. The HRRR does show scattered activity the remainder of the overnight mainly south of I-40, which is consistent with the existing POP grids. We`ll keep the current forecast as is with no changes planned for now. && .AVIATION... 00Z TAF DISCUSSION. We`re currently dealing with the backside of another system, which is leading to lowered cigs and some light rain around Middle TN. MVFR cigs will give way to IFR cigs after 06Z tonight, including some VLIFR at KCSV around sunrise. The only wrench in that lower possibility would be rain, which might give IFR instead of those lower categories. Winds will be relatively light and variable overnight, but will be breezy on Tuesday afternoon out of the north. && .OHX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION......08 AVIATION........Unger
Area Forecast Discussion
National Weather Service Mount Holly NJ
935 PM EDT Mon Apr 8 2019 .SYNOPSIS... Low pressure will move into New England tonight then into the Canadian Maritimes Tuesday. Its associated cold front crosses our region Tuesday afternoon and evening. High pressure will then build in for Wednesday and Thursday. The next cold front arrives Friday night, followed by high pressure for most of the weekend. Another low pressure system may affect the region early next week. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... A remnant MCV is moving off the coast of Virginia this evening with widespread convection with it. Leftover showers now across much of Delmarva into far southern New Jersey are expected to move offshore later this evening. A good portion of our Delmarva zones and into southern New Jersey should get another round of showers overnight as a main short wave slides across. While a rumble of thunder cannot be ruled out there overnight, it appears that the earlier convection has reduced the instability enough to produce much of any additional thunder. For the 930 PM update, adjusted the PoPs based on radar and HRRR trends. Adjusted the hourly temperature, dew point and wind grids based on the latest observations and trends. Extensive mid to high clouds over the region this evening should thin some across the northern areas. There should be some fog development overnight, especially where the higher level clouds thin, and also where rain occurred. Thicker cloud cover across the southern areas may keep the fog potential more limited. There is a backdoor front sitting just to our northeast, over the NYC metro and then just south of Long Island. This may slide a bit farther southwestward overnight, however this is low confidence. It this boundary does shift more southwestward, then low clouds are more likely in its wake. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/... For the 930 PM update, made some adjustments to the PoPs and also temperatures, dew points and winds. While a cold front arrives from the west later in the afternoon, some guidance showing a backdoor front slipping southwestward with a wind shift from onshore at least across our northeastern zones. The NAM is more robust in bringing this boundary farther to southwest with the cooling and low clouds in its wake, however did not go full throttle with it at this time. The ECMWF also shows more cooling the farther northeastward one goes across our region. Otherwise, the surface low and associated upper trough will be crossing north of the area Tuesday. A cold front will cross the area during the afternoon and evening. Some showers are expected with possibly a few tstms with the front. The coverage may be mostly scattered but did place an area of low likely PoPs across the northern areas where forcing is stronger for a time. && .LONG TERM /TUESDAY NIGHT THROUGH MONDAY/... Summary: The long term will start off rather benign and mostly seasonable through mid week. Friday and Friday night brings the next significant chance for widespread rain. At this point most of the weekend weather looks quiet until the next system comes in late Sunday. Details: Wednesday and Thursday...surface high nudges down from the north, which should result in tranquil weather and temperatures near or just slightly below normal. The ECMWF is the only operational model depicting any precipitation over our area through this time, and light precipitation confined to far NW NJ and the southern Poconos at that. I have kept the forecast dry however, as it seems unlikely the warm front responsible for the precip would extend as far east as our region while the center of the surface low is still over the central Plains. Friday...We should start the day in southwesterly flow under the warm sector of the low pressure system that will by this point be lifting from Minnesota/Wisconsin into Ontario/Quebec. The cold front associated with this system (likely occluded by this point) should cross through our region Friday night. Showers and maybe some thunderstorms (depending on the timing of the front) will be possible ahead of and with the front. Saturday through Monday...Most models depict the cold front already off shore by sunrise Saturday. Once that front is off shore, we should have quiet weather for much of the remainder of the weekend. The next system we will be watching should be in the desert Southwest on Saturday, and models have it lifting over our region into New England by Monday. If this patter evolves, it would mean another chance of rain starting during the second half of the day on Sunday continuing into Monday morning. && .AVIATION /02Z TUESDAY THROUGH SATURDAY/... The following discussion is for KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY and surrounding areas. Overnight...VFR, however some low clouds and fog should develop after 06z especially south and east of PHL resulting in MVFR to locally IFR conditions. Some showers are expected from near the PHL area to the south and east. West to southwest winds diminishing to around 5 knots, then becoming locally light and variable. Lower confidence regarding the extent of low clouds and/or fog overnight. Tuesday...Any MVFR/IFR conditions should improve to VFR by 15z. West-southwest winds increasing to around 10 knots with gusts to 20 knots by late afternoon. Some showers (perhaps isolated thunder) by late afternoon could result in brief restrictions especially from ABE to TTN on northward. A front may slide in from the northeast, and if this were to occur then lower conditions will develop/persist longer. This is of low confidence at this time. Outlook... Wednesday and Thursday...VFR conditions are expected. Northwesterly winds on Wednesday may gust up to 20 kt. By Wednesday night however, expect light and variable winds. Friday...Conditions should start VFR, but MVFR or even IFR conditions will be possible as showers and thunderstorms are likely to move into the region later on Friday into Friday night. Southerly winds may gust up to 30 kt, especially close to the coast. Saturday...Mostly VFR conditions are expected. && .MARINE... The conditions overall are anticipated to remain sub-SCA through Tuesday with some showers across the southern waters tonight. Any thunder should end by midnight. On Tuesday, another chc for a shower or tstm during the afternoon. Some patchy fog will develop over the chilly waters late tonight and Tuesday morning. Outlook... Wednesday through Thursday...winds and seas are expected to remain below SCA criteria. Friday...Southerly winds will be increasing through the day, and wind gusts could exceed 30 kt by Friday evening. Seas should subsequently increase above 5 feet as well, primarily on the Atlantic coastal waters. Saturday...Elevated seas may linger for part or all of the day time hours on Saturday. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...None. NJ...None. DE...None. MD...None. MARINE...None. && $$ Synopsis...Gorse/Johnson Near Term...Gorse/O`Hara Short Term...Gorse/O`Hara Long Term...Johnson Aviation...Gorse/Johnson/O`Hara Marine...Johnson/O`Hara
Area Forecast Discussion
National Weather Service Sacramento CA
218 PM PDT Mon Apr 8 2019 .SYNOPSIS... Wet weather will gradually spread southward across the region late today and into tonight with most of the precipitation falling over the northern portion and mountainous regions. Thunderstorms with heavy rain remain a strong possibility over Shasta County this afternoon and evening potentially leading to flooding issues. Showers will decrease by Tuesday evening with dry weather expected Wednesday. Another system may bring some showers to the mountains Thursday. && .DISCUSSION... The forecast remains on track today as an upper level trough advances towards the west coast. Rain has been falling over the northern most areas of California so far, but will gradually spread southwards throughout the rest of the day and into the evening and overnight hours. Model guidance continues to trend towards thunderstorm activity for the northern half of the CWA, primarily over the Shasta County area. The HREF and HRRR ensemble continue to point toward the potential for strong thunderstorms with the main threat being heavy rain. This could lead to potential flash flooding given the saturated soils, deep available moisture, PWATs from local soundings, and strong south/southeasterly low- level inflow/ convergence. The latest HREF continues to highlight a high potential (> 50%) for hourly rainfall rates exceeding 0.5-1.0 inch an hour, and their ensemble even shows non- zero chances for 6 hour amounts to exceed 3 inches into this evening. Hail and a brief tornado remain possible, but given the convective ingredients and current cloud cover, confidence has lowered on these hazards. Moving on to the snow portion of the forecast, it continues to look rather unimpressive as snow levels will remain high throughout the rest of today. However, once the cold front moves through early Tuesday morning, snow levels are forecast to lower to around 5000 feet. Thus a few inches of new snowfall accumulation will possible across the higher passes before showers taper off late Tuesday. Behind this trough, we`ll have a brief period of dry but breezy weather as high pressure builds over head on Wednesday. Models then show a "slider" type system slipping over the ridge. This could bring some showers to our mountains on Thursday. && .EXTENDED DISCUSSION (Friday THROUGH Monday) EFP forecast begins with a low pressure system from the Aleutian Chain spilling over the neutral to positively-tilted Ern Pac ridge and diving Swd across Wrn Canada the first half of this week, and then the Pac NW and NV by the end of the week. Precip over Norcal (mainly the Sierra) expected to come to an end early Fri, but pressure rises in the wake of this system will create those annoying strong, gusty Nly winds right during allergy season. WAD (wind advisory) criteria may be met. Strong Wly flow over the Pac creates a very progressive wx pattern over the Ern Pac and Noam with none of the trofs/ridges establishing a blocking pattern. This continues a series of low pressure systems from the GOA (Gulf of AK) moving through the Pac NW and Norcal bringing chances of precip to our CWA. This is where the daily model runs have difficulty in keeping up with the timing of the individual systems, thus forecast confidence is low on the details of each system. There is reasonable agreement that the next system will affect our CWA from N to S late Sat into Sun, with much less certainty for Mon and Tue. With the RMOP for 5H heights trending slightly higher then, we could be dealing with the drier ECMWF solution than the wet GFS solution. The RMOP would give credence to the ECMWF 5H pattern with W or NWly flow over Norcal than the deep 5H cyclone the GFS develops off the Pac NW coast late in the period. JHM && .AVIATION... Pacific front moving across Norcal during afternoon with thunderstorm lines/short segments developing behind the front during afternoon and evening hours thru 03z. Convective activity moving Ewd into the higher elevations of the W Slope Sierra til 07z. Mostly VFR conditions in the Vly except for MVFR/IFR conditions at times in the northern Sacramento Valley due to +SHRA/+TSRAGS. Developing widespread MVFR conditions over the W Slope Sierra with local LIFR conditions in precip obscuring higher terrain. Sly wind gusts 15-25 kts continue across the northern half of the Sacramento Valley through 03Z with gusts to 30 kts, and winds over the southern Sacramento and northern San Joaquin Valley gusting to around 20 kts thru evening. Behind front, drier NWly flow will return VFR conditions to Norcal on Tue. && .STO WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch until 9 PM PDT this evening for Burney Basin / Eastern Shasta County-Mountains Southwestern Shasta County to Northern Lake County-Northeast Foothills/Sacramento Valley- Northern Sacramento Valley-Shasta Lake Area / Northern Shasta County-Western Plumas County/Lassen Park. && $$