Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 04/24/17


Area Forecast Discussion
National Weather Service Charleston SC
1007 PM EDT Sun Apr 23 2017 ...RECORD RAINFALL LIKELY MONDAY... .SYNOPSIS... A low pressure system will affect the area tonight through Tuesday. High pressure will then build into the area through the weekend. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... 24/01z mesoanalysis placed low pressure between KOKZ and KBNL, somewhere over Burke or Jefferson Counties in east-central Georgia. A sharp stationary front extends east of the low, roughly along a Waynesboro-Branchville-Holly Hill-Saint Stephen line with a cold front dropping south across south-central Georgia, through the central Florida Panhandle and into the northeast Gulf of Mexico. As expected, a line of strongly forced convection has developed in the warm sector ahead of the approaching surface low. Expect this line to slowly intensify over the next several hours and move across much of Southeast South Carolina and Southeast Georgia as deep layered forcing/mid-level height falls associated with upper low moving into northern Alabama overspreads the area. It still looks like the risk for severe tstms will be the greatest roughly along and north of a Millhaven-Aleda-Ashepoo-Hollywood-Folly Beach line, including the Charleston Metro Area where the better juxtaposition of instability, forcing and 0-6km bulk shear will be found. The approaching line will have the capability to produce localized damaging winds and some large hail, but the tornado risk looks the highest across northern parts of Colleton, Dorchester and Berkeley Counties where low-level winds are backed a bit more closer the stationary front. Several transient low-level rotational signatures have already been detected on KCLX and KCAE over the past hour. High resolution guidance has been consistent in showing the approaching convective line slowing down and possibly becoming stationary across the Charleston Tri-County area early Monday as the upper low digs into central Georgia and the region of strongest upper difluence becomes aligned along the I-26 corridor. Both the RAP and H3R show a "Joaquin-like" reflectivity signature over Charleston, Dorchester and Berkeley counties as high tide occurs. Opted to expand the Flash Flood Watch west to include Dorchester County and move the start time up to 2 am. High tide will occur in the Charleston Harbor just before 7 am. For the late evening update: * increased pops and expanded the mention of locally heavy rainfall to most zones. * made minor adjustments to sky cover as well as hourly temperatures and dewpoints. * increased QPF across far interior Southeast Georgia were radar already shows some areas seeing rainfall amounts >2 inches. && .SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/... Monday: The deep mid-level cut-off low pressure area will gradually end a digging phase and bottom out near east central GA during the morning and then move east toward the CSRA by late day. Surface low pressure will also translate from northeast GA into coastal SC by later in the day. While models are in relatively good agreement on major synoptic features, there remain subtle timing differences which could make or break some forecast elements, especially rainfall amounts. We have a Flash Flood Watch for Charleston and Berkeley Counties for Monday as deep moisture interacts with strong upper forcing. The main concerns for the watch were obviously the heavy rain likelihood in Downtown Charleston along with portions of upper Charleston County west to Moncks Corner and Jamestown where models continue to hone in on the axis of highest amounts. Temps aloft will be cooling during the day adding to the elevated instability pool to the north of the Savannah River. Severe weather potential Monday is strictly limited to the morning and early afternoon hours across the Charleston 4-county region and highly dependent on breaks in the clouds during the period where the most potent upper forcing is expected. We think the risk for isolated storms with large hail and damaging winds is isolated while the heavy rain threat remains paramount. Over southeast GA, rain chances will be lower and despite some colder temps aloft, tstm potential does not look too impressive either to the south of I-16. Monday Night: The upper low will begin to move away from the upper SC coast late while the conveyor of deep moisture pulls well to the north. Clouds will be variable at times as deep cyclonic flow prevails. Lows will be cooler in the 55-60 degree range. Tuesday: Upper heights continue to rise and mostly dry weather is expected. There could be a few instability afternoon showers across eastern SC, but coverage and amounts look sparse. Wednesday: A warm day is on tap as upper ridging dominates. Highs in the mid 80s. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... Deep layered ridging will result in dry weather and highs in the mid to upper 80s. A weak upper shortwave will approach early Friday but is expected to be deflected to the north. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... KCHS: Main concerns are low vsbys/cigs within TSRA. Corridor of greatest impacts looks to occur roughly 09-15z as a strong line of convection moves through. Opted to show prevailing MVFR with a tempo group with vsbys as low as 1 1/2SM, or just below Alternate Minimums. Briefly lower conditions will be possible as the main line moves through. The main line should move east of the terminal by 14-15z with improving conditions thereafter, although a secondary line could move through the cold front itself. KSAV: Right now, it appears the risk for tstms will remain just north of the terminal, but close enough for possible impacts. Will show TSRA from roughly 04-07z given latest model trends, but limited conditions to MVFR for now. Lower conditions could occur if tstms move farther south than expected. A secondary line of showers with the cold front itself will cross the terminal roughly 11-14z. Opted for VFR for now with this line, but lower conditions could occur depending on how much lingering instability is realized. Extended Aviation Outlook: Periods of flight restrictions, mainly low ceilings, possible through Tuesday morning as a low pressure system moves through. VFR conditions will return Tuesday afternoon into late week. && .MARINE... Tonight: A low pressure system will move into southeast SC/GA tonight with winds and seas expected to increase. Small Craft Advisory is in effect for the Charleston county waters and outer Georgia waters beginning at 02z. Elsewhere, conditions are expected to remain below advisory levels, although certainly could not rule out a few gusts nearing 25 kt. Seas on average will 3-5 ft nearshore, 4-6 beyond 20 nm. A wind shift from south/southeast to southwest will occur across SC waters on Monday as the strong upper low digs into GA. While the onshore flow will subside, a SCA will linger through the day into the early evening on Tuesday over AMZ350. Over the outer GA waters, seas will subside during the day but are expected to ramp up again Tuesday Night in jetting offshore flow. Modest offshore winds expected Tuesday behind the low pressure system with seas over the offshore GA waters possibly rising back above 6 ft for a brief period with a chance for periodic gusts to 25 KT from Grays Reef seaward. Southerly winds will return mid to late week as Atlantic high pressure prevails. && .CLIMATE... Record rainfall amounts for 24 April: KCHS: 0.81" set in 1943, KCXM: 1.12" set in 1937, KSAV: 1.55" set in 1941, && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...Flash Flood Watch from 2 AM EDT Monday through Monday evening for SCZ044-045-050-052. MARINE...Small Craft Advisory until midnight EDT Monday night for AMZ350. Small Craft Advisory until noon EDT Monday for AMZ374. && $$
Area Forecast Discussion
National Weather Service State College PA
1049 PM EDT Sun Apr 23 2017 .SYNOPSIS... A storm system over the southeastern states will begin to make slow progress northward along the coast over the next several days. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... High clouds continue to stream northward moisture swirling around a potent upper low over TN surges our way. They are thickest over the south, thinnest over the north. The HRRR shows light rain just beginning to creep up over the Mason-Dixon line counties shortly after sunrise, otherwise it will remain dry tonight with a ridge of high pressure holding on across the northern tier counties of PA, while the northern extent of deepening, moist easterly flow off the Atlantic advects north to near the Mason/Dixon line well after midnight. Broken to overcast mid/high clouds will help to curb the temp fall across the south. Mins will be mainly between 40-45 throughout the Central and Southern counties of the state. Clear to scattered thin high clouds will continue through most or all of the overnight over the Northern Mountains allowing lows to dip into the 30s with some patchy frost. && .SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/... The aforementioned upper low will deepen and cut off over the Southeastern states Monday before taking a left hand turn and drifting north along the Mid Atlantic Coast later Monday through Wednesday. The main core of the anomalously strong, moist southeasterly winds (approx -3 sigma U-component of the 850 mb wind), will move from VA and NC Late Monday, to Southern and Eastern PA by Tuesday afternoon. This translates into gradually lower and thickening clouds Monday and Monday night with some light rain or showers expected to spread in from the south during the mid to late afternoon hours across the far south, before reaching the Interstate 80 corridor around or shortly after midnight Monday night. Rainfall does not look heavy on Monday, as the best moisture/easterly wind anomalies pointed to the south of the state and the sfc low will still be down near Myrtle Beach. Similarly mild high temps are expected across the northern PA TAF sites, while temps cooler than Sunday by some 8-10 deg F are forecast across the south. Mid to upper 50 deg highs for the south Monday could be a few to several deg F on the high side. && .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/... The period of Monday Night to Tuesday Night will be dominated by the flow around a slow moving cut-off low which eventually will pass to our south and east. This system will bring clouds and light rain to the parts of our region for several days. The models are in fair agreement on timing and position of this low. However as we get into Tuesday around 12Z the ensembles begin to diverge. The bands of precipitation should begin to streak through the region, mainly the east Tuesday morning. Timing and position of the low will change whether or not different portions of central Pennsylvania get precipitation. Have adjusted the orientation and adjusted POPS accordingly. The gradient will be tight on any precipitation amounts. Once this system goes by it will get warm fast. It should feel like summer through the second half of the week. As the 500 hPa low fills and the attendant moves to our northeast the chance of rain should fall off Wednesday into Wednesday evening. Our 850 hPa temperatures will rise rapidly Wednesday and it should be noticeably warmer Wednesday relative to Monday and Tuesday. Thursday into Saturday the 850 hPa temperatures will be well above normal, mainly in the 14 to 16C range and we will be on the western edge of a rather impressive early season subtropical ridge. Thursday through at least Saturday should be very warm and humid. We should have several days with high temperatures around 80. Thursday into Friday will see the passage of large upper level trough. Have left broad POPS as this trough will move a corresponding front through. && .AVIATION /03Z MONDAY THROUGH FRIDAY/... High pressure and associated dry air mass over Pennsylvania will ensure widespread VFR conditions and light winds through tonight. Latest LAMP/downscaled NAM and SREF suggest there could be some patchy fog in vicinity of LNS early Monday morning. However, given the expected amount of mid and high level cloudiness, feel significant fog formation is unlikely. Low pressure lifting up the east coast will spread lowering clouds and spotty light rain into southern Pa Monday. Initially, dry air in the low levels should keep conditions VFR. However, model soundings and SREF prob charts suggest MVFR conditions will become likely by Monday evening across southern Pa, with IFR even possible at AOO/JST. Outlook... Tue...Rain/low CIGs likely. Wed...AM rain/low CIGs possible. Thu...AM fog possible. PM tsra impacts possible. Fri...PM tsra impacts possible. && .CTP WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...La Corte NEAR TERM...La Corte SHORT TERM...Lambert LONG TERM...Dangelo/Ceru AVIATION...Fitzgerald
Area Forecast Discussion
National Weather Service Green Bay WI
636 PM CDT Sun Apr 23 2017 Updated aviation portion for 00Z TAF issuance .SHORT TERM...Tonight and Monday Issued at 309 PM CDT Sun Apr 23 2017 The latest rap analysis and satellite/radar imagery show a cold front dropping southeast from Merrill to Oshkosh early this afternoon. As winds turned to the northeast behind the front, temperatures fell 5 to 10 degrees at Green Bay and Appleton. Meanwhile, scattered light rain and snow showers continue to pass over northern WI, north of Merrill and Antigo. Quite a temperature difference between Land O Lakes where clouds and precip have kept temperatures in the middle 30s, and Wautoma where the mercury has reach 70 degrees. As the front waffles first south tonight and then north on Monday, cloud trends and relative humidities are the main forecast concerns. Tonight...The cold front will settle across southwest Wisconsin to northern Illinois. However, this front will remain shallow, since moderate return flow will already start ramping up at 850mb during the evening. As a result, do not think the cloud cover will make it that much further south, and trended more optimistically with the sky cover. Regardless, the clouds should retreat north overnight as cirrus invades from the west. With a brisk east wind, temps falling to near 30 in the north to the upper 30s over the southern Fox Valley. Monday...The cold front will retreat northward as winds veer to the southeast with low pressure moving across the central Plains. Very dry air over the mid-Mississippi Valley will return northward, which should provide high temps in the 60s and low relative humidities. Mid and high clouds will increase in western areas through the afternoon, but the airmass is too dry below 12kft for precip chances. Winds, however, will become gusty, with some gusts up to 30 mph possible. .LONG TERM...Monday Night Through Sunday Issued at 309 PM CDT Sun Apr 23 2017 Active weather expected for the rest of the week, with potential for at least two significant synoptic scale weather systems. The jet energy for these systems is still out over the Pacific Ocean, so the models are still having some trouble coming up with a consistent track for these systems, which of course is important for bit precipitation type and amounts. The first system arrives Tuesday afternoon or evening as a strong upper jet lifts northeast from southeastern Colorado with some weaker jet energy moving across the northern Plains. These systems phase to some degree and produce several waves of low pressure that move northeast along a nearly stationary front from Oklahoma to Lake Michigan. The models are a bit further west with these systems than they were yesterday, which makes snow in northern Wisconsin less likely. There should be periods of significant rainfall Tuesday night through Thursday, which will probably result in some minor flooding, as several rivers and streams are currently near or above bankfull. Another system looks to arrive Saturday or Sunday, but there is even less model agreement with that system. The GFS and ECMWF do agree that it moves well west of the forecast area, which could bring some heavy rains and then a threat of severe storms if it unfolds as depicted. && .AVIATION...for 00Z TAF Issuance Issued at 630 PM CDT Sun Apr 23 2017 The precipitation band that impacted northern WI earlier in the day has lifted north, so the precipitation threat has ended. Patchy MVFR ceilings remained near the Upper Michigan border, but those should be short-lived. The cold front that arrived earlier today will lift to the north as a warm front on Monday. The main effect of this frontal passage will be increasing southeast winds, which will gust to 20 to 25 knots at most locations. Mainly middle and high level clouds are anticipated through the TAF period, along with VFR conditions. && .FIRE WEATHER... Issued at 309 PM CDT Sun Apr 23 2017 As the cold front lifts back north as a warm front across the western Great Lakes on Monday, warmer temperatures will return along with gusty southeast winds and low relative humidities. Near critical fire weather conditions are possible on Monday afternoon as temperatures rise into the 60s, winds gust to 20 to 30 mph, and relative humidities bottom out in middle to upper 20s. && .GRB WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM.....MPC LONG TERM......RDM AVIATION.......Kieckbusch FIRE WEATHER...MPC
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1043 PM EDT Sun Apr 23 2017 .SYNOPSIS... A deep and vigorous low pressure system moves across Georgia to the Carolina coast creating a lengthy period of moderate to heavy rainfall and below-normal temperatures that persists through Monday. Storm total rainfall accumulations of 2 to 5 inches are likely. A drying and warming trend begins Tuesday and continues through next weekend. A slight chance of diurnal mountain showers and thunderstorms returns Thursday and persists through the weekend. && .NEAR TERM /THROUGH MONDAY/... As of 1030 PM EDT: The Flood Watch has been expanded to include all of Upstate SC. Oconee and Pickens counties have been worked over late today and latest HRRR/RAP runs bring another two inches to this area overnight. Given the shower band feeding into the lower piedmont and wrapping occurring east of the 850 mb low center, this seems quite reasonable and could lead to flooding. Elbert County remains the primary question for GA counties, but there should be some additional eastward drift before the band becomes oriented more NW to SE across SC. Will thus keep the GA counties out of the Watch. Otherwise, water vapor imagery shows the cutoff upper low spinning slowly southeast across northern Alabama this evening, and the RAP height fields (which have handled this fairly well) bring the center of circulation slowly to the central GA/AL border by daybreak Monday. Strong upper divergence is already in place atop the region this evening and the low track will bring strengthening southeasterly 850 mb flow to the western Carolinas and yield continued isentropic upglide and upslope terrain flow into the Blue Ridge. Given the precipitable water values surging to +2 to +3 standard deviations above climo, the afore mentioned forcing, and the steepening 850 to 500 mb lapse rates overnight, anticipate improved precipitation rates through the nighttime hours and well into Monday. Hydro problems are likely to worsen quickly overnight. The hydro focus will increasingly shift northward into the NC foothills/piedmont and the I-77 corridor over time. Anticipate fairly solid 2 to 4 inch QPF amounts going forward, with localized totals near 6 inches possible with any training. Conditions will slowly improve from the southwest during the day on Monday as the entire system slides slowly east. Deformation banding north and northwest of the 850 mb circulation could keep localized maximum QPF stripes in our piedmont through late Monday. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/... As of 205 PM Sunday: Obviously the main short term concern will be timing the ending of the precip potential, especially across the eastern part of the forecast area, as upper low continues to wobble in the vicinity of the SC Coast. This will place the I-77 corridor in a good position to receive continued bands of rainfall associated with the deformation zone north and west of the cyclone. In fact, there`s a decent consensus in deterministic guidance that another .5-1 inch of rain will fall in this area Monday evening, and we will forecast as much. This amount of qpf would certainly warrant an extension of the Flood Watch, but that decision can be left to later shifts and further collaboration with WFOs to our east and south. Pops gradually taper off after midnight through Tuesday, really not dropping below 20 percent until Tue afternoon, in line with uncertainty regarding how quickly the upper low`s influence will end for our area. Temps will also be a bit problematic on Tuesday, as areas along the Upper Savannah River Valley will likely see clearing skies by afternoon, while locations along the I-77 corridor should underneath a cloud shield. Tuesday`s high temp forecast therefore ranges from around 80 across the USRV to mid/upper 60s across the northwest NC Piedmont. The remainder of the short term will be decidedly tame, as upper ridging builds along the Eastern Seaboard in the wake of the upper low, and downstream of large scale central Conus height falls. This will result in a return of much-welcomed dry conditions while Wed max temps are expected to return to the 80s in most locations east of the mtns. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... As of 215 PM Sunday: The medium range will see the establishment of a massive/broad upper trough encompassing much of the western 2/3 of the Conus, with ridging expected to dominate much of the East Coast. This will result in unseasonably warm temperatures continuing across our area through at least the end of the weekend. The first in a series of short waves ejecting from the western Conus trough will ride along the western periphery of the Eastern ridge Wed night through Thursday, passing well west and north of our area. Nevertheless, a weakening/occluding cold front is forecast top approach the southern Appalachians and vicinity by the end of Thursday. There will be a deep fetch of Gulf of Mexico moisture immediately ahead of this feature, resulting in a decent amount of pre-frontal instability. Despite the weakening forcing, this should provide decent chances for convection, mainly across our western areas Thu afternoon/evening. Shear is forecast to be adequate (but not much more than that) for organized convection, so the severe threat will depend substantially on the amount of buoyancy that is realized, and this is still quite uncertain. Warm sector air mass remains pretty much ensconced across the area late in the week through the weekend, with global model guidance depicting a summer-like pattern, with anomalously strong Bermuda high supporting plenty of heat/moisture/instability each afternoon. Diurnal deep convective chances (mainly in the 20-40% range) will therefore be advertised each day from Fri through the weekend. && .AVIATION /03Z MONDAY THROUGH FRIDAY/... At KCLT: Several cells moving northward from the Midlands have brought the potential for occasional cloud to ground lightning strikes despite the wedge layer in place. Still anticipate primarily heavy rain showers to grow and expand across the region as the backing 850 mb jet strengthens late this evening and overnight. Anticipate mainly IFR cigs this evening, transitioning down into the LIFR range with the heavier showers overnight. Very little variation is then expected through much of the rest of the period with gusty NE winds continuing along with IFR vsby and LIFR cigs. There should be a shear layer atop the wedge, but probably not low enough for LLWS conditions at present. Elsewhere: the expansive precipitation shield spreading into the terminal forecast area from the southwest this evening should stabilize ceiling conditions in the IFR range early, with LIFR ceilings likely overnight. The surface wedge appears deep enough to keep thunder out of the TAFs at present. Gusty northeast winds will continue across the foothills, but with more of a northerly component at KAVL. Some modest recovery is possible from KAND to KGMU late Monday as the deeper moisture pivots northward. Outlook: An area of low pressure will move slowly across the Carolinas toward the coast Monday night through Tuesday. Low clouds and precipitation will be slow to dissipate behind the departing system. Conditions should gradually improve later Tuesday through Wednesday morning as dry air works in behind the departing low. Return flow moisture ahead of the next system will develop late in the week. Confidence Table... 02-08Z 08-14Z 14-20Z 20-00Z KCLT Med 63% Med 62% Med 62% Med 70% KGSP High 82% Med 62% Med 61% Med 75% KAVL Med 72% Med 76% Med 65% Med 66% KHKY High 80% Med 70% Med 69% Med 70% KGMU Med 76% Low 58% Med 61% High 85% KAND Low 51% Low 54% Low 58% Med 66% The percentage reflects the number of guidance members agreeing with the scheduled TAF issuance flight rule category. Complete hourly experimental aviation forecast consistency tables and ensemble forecasts are available at the following link: www.weather.gov/gsp/aviation && .HYDROLOGY... The Flood Watch has been expanded to all of Upstate SC as feeder bands of heavier showers continue to develop upstream through GA and back into FL. Hydro conditions will steadily worsen overnight, with Flood Advisories becoming more common and Flood Warnings likely being needed late tonight through Monday, expanding in area and duration through the day on Monday as additional precip amounts of 2 to 4 inches, with isolated 6+, add up. None of the river forecast points are forecast to go into flood currently, but locations along the Catawba river chain will need very close monitoring through Monday as the heavy rain axis could pivot over the area. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...Flood Watch through Monday evening for NCZ033-035>037-048>053- 056>059-062>065-068>072-082-501>510. SC...Flood Watch through Monday evening for SCZ001>014-019. && $$ SYNOPSIS...JMP NEAR TERM...CDG/HG SHORT TERM...JDL LONG TERM...JDL AVIATION...CDG/HG HYDROLOGY...HG
Area Forecast Discussion
National Weather Service Marquette MI
731 PM EDT Sun Apr 23 2017 .SHORT TERM...(This evening through Monday) Issued at 343 PM EDT SUN APR 23 2017 12Z raobs/latest wv imagery and RAP analysis show a confluent wnw flow alf over the Upr Lks btwn nrn branch troffing centered over Hudson Bay and a zonal srn branch flow dominating the CONUS. The cold fnt which swung thru Upr MI late last ngt/early this mrng has pushed into scentral WI and stalled, but the frontal bndry at h85-7 is still nearly ovhd and supporting a bkn band of rain/snow showers over the wrn cwa. Sfc hi pres bldg into nw Ontario is extending a sfc rdg axis over Lk Sup, and the llvl drying/sharper acyc flow associated with this feature has brought some clrg to that portion of the cwa. Very dry air is also located to the s of Upr MI even over the stalled sfc fnt. Looking well upstream, a vigorous shrtwv that caused 12hr h5 hgt falls of nearly 100m in the srn stream flow is moving into the central Rockies. Tngt...As the srn branch shrtwv now moving into the Rockies aprchs the wrn Plains late, a sfc lo pres is fcst to deepen over the ncentral Plains while the hi pres over northern Ontario drifts slowly to the e. As the flow alf veers to the s in response to the falling mslp to the w, the fntl bndry that stalls to the s wl return to the n. The associated isentropic ascent best shown on the 290-295K sfcs (h8-7) wl support some lgt pcpn generally in the form of snow over mainly the nw half of the cwa away fm drier llvl air over the e, but the steady shift to the n of the warm fnt and influence of the llvl dry air wl limit pops/pcpn amnts. The presence of a good deal of lingering clds over the w and incrsg hi/mid clds over the e associated with the waa wl limit the diurnal temp drop despite the llvl dry air. Mon...The shrtwv/lo pres in the ncentral plains is fcst to drift ne toward nw MN late in the day, lifting the sfc warm fnt and band of waa pcpn to the n of Upr MI. The short range guidance shows quite a bit of mid lvl drying in the warm sector. With the prospect of at least some sunshine thru hi clds and h85 temps rising to arnd 5C, temps should rise well into the 50s, especially in the downslope areas influenced by the llvl se flow, where readings wl probably reach the 60s. Tended toward the hier end of guidance for temps. More clds/at least sct showers could arrive over the far w late in the day as the lo pres/deeper mstr and stronger forcing ahead of the shrtwv aprch. .LONG TERM...(Monday night through Sunday) Issued at 351 PM EDT SUN APR 23 2017 The main forecast highlights through the week remain the active pattern advertised by the medium range models, which will bring multiple chances for precipitation across the area. Winter weather is expected to make a return with freezing rain, sleet, and snow possible through the middle/end of the week. There is still quite a bit of uncertainty, so continue to monitor the forecast! Monday night into Tuesday, low pressure will continue to lift northeast towards western Upper Michigan as a couple of weak shortwaves lift northeast across the region. As the better lift and deeper moisture arrives, expect rain to begin across the west early Tuesday morning. Further to the east and south, mid-level air looks far too dry for any overnight precipitation. Through the day on Tuesday, precipitation will begin to wane across the west; however, a north to south oriented surface trough is expected to remain anchored across the central portions of Upper Michigan. This surface trough will become further enhanced Tuesday evening and overnight as additional shortwave activity lifts across the region, bringing back precipitation chances across much of the area. Precipitation type will also be an issue as the upper-level flow continues to remain quasi-parallel to the surface trough, making the Northern Great Lakes serve as a pivoting point between the colder Canadian air dropping southeast and warm, moist air lifting northeast. Tuesday evening into the overnight hours, precipitation is expected to remain all rain as surface temperatures through the low levels remain above freezing. However, there will be a transition over to freezing rain and sleet as colder Canadian air undercuts the warm moist air across the west on Wednesday morning and may push east into portions of central Upper Michigan. Forecast soundings show the potential for limited cloud ice at times; therefore, we could see more freezing drizzle than rain across the west. For simplicity and consistency have opted to leave it as freezing rain for now. Warming surface temperatures over the past few weeks will also complicate ice accumulations, albeit still possible, especially on elevated surfaces. Impacts from this wintry mix of precipitation will be highly dependent on the longevity and intensity of freezing rain. Precipitation is expected to linger through much of the day on Wednesday. However, confidence is much lower in how things will evolved on Wednesday with precipitation type across the central portions of the area. With the colder, shallow air continuing to move east with time, did opt to run with non-diurnal temperature which did push some mentions of freezing rain across portions of central Upper Michigan. Wednesday night through Thursday, as the main longwave trough beings to lift northeast out of the central Plains, the elongated surface trough draped across the region will transition from an open wave to a maturing system. As this occurs, there is the potential for locations across Upper Michigan to see accumulating system snow and freezing rain as this system tracks across the region; however, this will be highly dependent on the track of the system. The medium range models track the system anywhere from the western U.P. to eastern U.P. overnight Wednesday into Thursday. The further east track would be more favorable for system snow across the west and possibly central portions of the area. However, if the system were to take the western most track, much of the area may be dry slotted during the day Thursday. Considering the variety of plausible solutions, not comfortable pinpointing any specific amounts or areas that may see system snow at this time. However, this is definitely a time period that needs to be monitored as the system continues to develop and evolve over the next few days. Depending on when the track of the system, precipitation chances may linger through the day on Thursday before gradually coming to an end from south to north as the system finally exits the region and moves north of the Hudson Bay. Friday looks mostly dry as high pressure briefly moves overhead. This weekend the active weather will continue with additional chances for precipitation. The GFS is much more aggressive bringing precipitation back north on Saturday, whereas, the ECMWF is much slower. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 730 PM EDT SUN APR 23 2017 As warmer air aloft advances n tonight, some -sn may develop across the Keweenaw. However, right now potential appears quite low for any pcpn at KCMX, so only a VCSH was included in fcst. Otherwise, as drier low-level air continues to expand into the Upper Great Lakes, lingering MVFR cigs at KIWD should clear out to VFR conditions before 06z. VFR conditions will then persist thru Mon. At KCMX/KSAW, VFR conditions will prevail thru the fcst period. During Mon, winds will become gusty to 20-25kt at all terminals. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 351 PM EDT SUN APR 23 2017 N winds up to 20 kts over the e half of the lake will diminish this evening as a hi pres ridge builds over the Upper Lakes. As this ridge shifts to the e and a deepening lo pres in the Plains moves toward MN, expect winds to veer toward the e-se and increase up to 30 kts on Mon. Where the winds will be strongest over the ncentral, there could be a gale. Winds will veer southeasterly overnight at 20 to 30 knots before gradually diminish to 10 to 15 knots across the western half of the lake by Tuesday morning. Further central and east, expect the southeast winds of 20 to 30 knots to persist. A few gale force gusts to 35 knots are possible early Tuesday night. Northeast gales of 35 knots look likely across much of the lake as the pressure gradient increases behind an exiting surface trough late Tuesday night through Wednesday. It is possible these winds may hold on through Wednesday night into Thursday, especially across the central and eastern portions of the lake. By Friday morning, winds will back west-northwest and diminish to around 10 to 20 knots. These winds will continue through the weekend, but veer to the east- northeast. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...KC LONG TERM...Ritzman AVIATION...Rolfson MARINE...KC/Ritzman
Area Forecast Discussion
National Weather Service Spokane WA
629 PM PDT Sun Apr 23 2017 .SYNOPSIS... Expect cool, breezy, and showery weather this week. The most widespread precipitation will likely occur Tuesday night into Wednesday with the potential for a half inch or more of rain over portions of the Idaho Panhandle and southeast Washington. A ridge of high pressure next weekend has the potential to bring the region a day or two of drier weather. && .DISCUSSION... Evening update: The forecast has been updated for the rest of this evening based on radar trends. Satellite shows the region under a broad upper trough with the jet axis south of the region in northern California placing Washington and north Idaho on the cool and unstable side of the jet. As of 620 pm radar indicated a few thunderstorms approaching Walla Walla and some lightning is possible in the Blue Mountains and thus forecast was updated for this. Also increased POP`s for the Lewiston and Pullman areas this evening with HRRR holding together these showers as they come off the Blue Mountains with a passing weak wave providing added lift. Elsewhere showers are more isolated in nature with a somewhat dry boundary layer with dew points in the lower to mid 30s and temperatures mainly in the 50s. Latest HRRR shows showers a bit more isolated or widely scattered this evening over most of Central and NE Washington into the Idaho Panhandle with only weak incoming forcing and instability. Thus some lowering of evening POP`s were made. Increasing POP`s around midnight still on track however for NE WA/N idaho as the weak wave tracks across the area. JW && .AVIATION... 00Z TAFS: As of 23z this afternoon scattered showers were occurring mainly over NE WA/N Idaho mountains. The boundary layer was relatively dry at all TAF sites with temperature/dew points spreads of 15-25F. Thus VFR conditions are expected to continue through the evening despite a general increase in light showers as the next wave enters. By Monday morning as low level upslope flow occurs for the eastern TAF sites (KGEG/KSFF/KCOE/KPUW) and the boundary layer continues to moisten with light showers...MVFR conditions may develop. JW && .PRELIMINARY POINT TEMPS/POPS... Spokane 39 53 38 56 42 53 / 30 70 30 30 50 60 Coeur d`Alene 39 52 38 54 39 52 / 60 80 30 50 60 80 Pullman 40 52 38 55 42 53 / 60 70 50 30 60 80 Lewiston 43 57 42 60 46 58 / 60 50 50 30 70 60 Colville 38 55 36 57 41 54 / 40 40 20 50 60 80 Sandpoint 39 51 36 52 37 50 / 90 40 20 60 70 80 Kellogg 38 49 35 50 37 48 / 70 90 60 60 60 90 Moses Lake 43 59 39 62 45 61 / 20 20 20 10 40 20 Wenatchee 42 57 41 60 43 58 / 30 30 20 10 20 20 Omak 38 58 37 63 43 60 / 30 20 10 10 20 20 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...None. WA...None. && $$
Area Forecast Discussion
National Weather Service Blacksburg VA
957 PM EDT Sun Apr 23 2017 .SYNOPSIS... Expect wet weather at least through Monday night, with surface low in the Tennessee Valley slowly moving eastwards to the South Carolina coast by Tuesday morning, while upper low slowly traverse the same general area. && .NEAR TERM /THROUGH MONDAY/... As of 950 PM EDT Sunday... Forecast update will reflect the addition of Rockbridge and Ahmerst County, VA to the Flood Watch. Latest qpf guidance from WPC offers a solutions of around two inches of rain falling within an area of increasing upslope flow, especially late tonight into early Monday. Have attempted to depict a small decrease in the coverage of the precipitation for a few hours after midnight tonight, before increasing again close to 300 AM or 400 AM. Total rainfall amounts now may be close to four inches along the crest of the Blue Ridge south of Roanoke, VA, and eastward into the Piedmont of North Carolina and neighboring parts of Southside Virginia. Have adjusted hourly temperatures and dew points based upon the latest observations and expected trends into the early morning hours. As of 635 PM EDT Sunday... The forecast update for early this evening will reflect mainly one notable change. A gap of a few hours in the widespread rainfall, to more of a scattered coverage, is expected across the southeast portion of the area. This gap will translate northward from near the NC/SC border before additional precipitation fills the gap back in later in the evening. Have also made minor adjustments to the hourly temperatures based upon the latest observations and expected trends through the evening. Some rain-cooled areas across the Mountain Empire region of southwest Virginia are already cooler than the overnight forecast low. Have adjusted the forecast low accordingly. As of 327 PM EDT Sunday... Flood Watch continues for most of the region through Monday evening. Positively titled upper level trough will deepen as it pivots to the southeast with a closed mid level low eventually traveling across the Southeast States. This pivoting will result in increasing difluent mid and upper level flow and associated divergence to the northeast of the low. A dual upper level jet structure may enhance upper level divergence over western North Carolina this evening into Monday morning. Rain, heavy at times will spread northeast across the region this evening into tonight and continue into Monday. Moderate to heavy rain is expected in the flood watch area, with 1.5 to 3 inches likely through Monday night. Locally higher amounts likely near the Blue Ridge, south of Roanoke. Initially the northern edge of the rain shield is sharp and utilized the 16z HRRR which captured the rain placement on the WSR-88d the best, then used a blend of GFS and NAM. The Day 1 excessive rainfall outlook placed an moderate risk across southwest portions of forecast area. This is supported by the better lift, jet dynamics, upper difluence and terrain enhancement. Models are hinting at higher qpf to our south across North Carolina and South Carolina. This may be suggesting potential for elevated convection to our south. Not expecting any thunderstorms or deeper convection for our area with wedge in place, and this should keep hourly rainfall rates limited. However, long duration rains will create a flood threat especially for creeks/streams and rivers. The flash flood threat will be isolated but cannot rule out some pockets across the southern Blue Ridge this evening into tonight. In contrast, for late tonight, there is some potential for dry slot to work toward the Mountain Empire before the easterly fetch off the Atlantic pulls rain back to the west Monday. Complex forecast tonight, but models agree in general weather of cloudy and rain. Low temperatures tonight will range from around 40 degrees in the mountains to near 50 degrees in the Piedmont. Increased pops on Monday in the west as vertically stacked cyclone slowly pinwheel southeast. Timing looked a tad slower on the movement. Good moisture transport continues Monday with PWAT around 1.25" along/east of the Blue Ridge and into the Piedmont. Stable thermodynamic profiles owing to residual wedge should hinder any thunderstorms. Northeast to north winds especially in the east will increase in speeds Monday afternoon into Monday night. This is a result of the strengthening pressure gradient between high pressure over the Northeast and low center over the Carolinas. Played high temperatures a little cooler with rich cloud cover and rain with readings from the mid 40s in the mountains to the mid 50-s in the Piedmont. && .SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/... As of 320 PM EDT Sunday... Wedge is gone on Monday night as surface and low level winds respond to approaching low. Bufkit guidance showed easterly flow and a saturated sounding 6 to 9 thousand feet deep. This strong upslope and Atlantic inflow will prolong widespread moderate to locally heavy rain. Axis of 850MB jet crosses northern North Carolina and southern Virginia Monday night and will be pointing toward Maryland and northern Virginia on Tuesday morning. Little variation in GFS/NAM forecast track and timing of surface and upper low. Upper low moves off the southeast coast Monday night then tracks northeast, very close to the coast, passing over the Outer Banks on Tuesday night. On Wednesday the 500 mb low is far enough away from Virginia that moisture wrapping around the west side of the system will be retreating from the Virginia, West Virginia and North Carolina. Will be slowing down the clearing on Tuesday. Similar to current forecast will have a low probability of showers in the Virginia piedmont on Tuesday night and a dry forecast for Wednesday. Stayed on the cooler side of guidance for maximum temperatures on Tuesday since more cloud cover is expected. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... As of 300 PM EDT Sunday... 500MB heights rise Thursday and Friday over the southeast United States but with an overall deepening upper trough over the central United States. A deep closed low develops over the Rockies by the end of the week which will keep much of the east downstream in broad southwest flow. At the surface a low pressure system tracks into the Great Lakes. The front with this system stalls in the Ohio and Tennessee Valleys on Thursday and Friday. 850MB temperatures increase to as high as +18 on the ECMWF on Friday over southern Virginia and northern North Carolina. Will have Saturday and Sunday with continued above normal temperatures. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... As of 725 PM EDT Sunday... Only the area generally along and north of a KLWB-KLYH line remains VFR this evening. The remainder of the area is experiencing IFR/MVFR ceilings with some pockets of LIFR. Visibilities have been variable between VFR and MVFR. Through the overnight hours, light to moderate rain will be across the region along with primarily LIFR/IFR ceilings and VFR/MVFR visibilities thanks to the rain and light fog. Little change in prevailing conditions is expected through the day on Monday. Winds will generally be from the northeast across the central and eastern sections of the region at 5 to 10 kts, with western sections having more of an easterly wind and similar speeds. Higher elevations will have slightly higher prevailing winds with some gusts in the 20 to 25 kt range. Extended Aviation Discussion... Poor aviation conditions expected to continue through Monday night, and at times into Tuesday, thanks to the slow moving upper low and attendant sfc system. Look for gradual improvement sometime Tuesday from west to east with better flying wx for by midweek, though another front may bring scattered MVFR showers/storms toward late Thursday in the mountains. Drier weather will return for Friday. && .HYDROLOGY... As of 300 PM EDT Sunday... No changes to the flood watch, with still some model differences in placement of highest rainfall threat. High-res models and analogs along with pattern recognition favor the southern Blue Ridge from Roanoke to Boone, east to the piedmont of VA/NC as those areas which appear to be in line to receive 2-3" through early Tuesday. This amount of rain combined with the 1 to 2+ inches that has already fallen since Friday should lead to hydro issues on rivers, as well as smaller creeks and streams. Looking at the analogs this pattern favors April 5th, 1993, and March 27th, 1993 which produced some minor to moderate flooding along portions of the Dan and Roanoke River mainly downstream of Danville and Altavista. Still will have to see how this sets up as we had been dry prior to this event. WPC has kept the moderate risk of FFG exceeded over the southern Blue Ridge. As mentioned in the near term, deep convection seems limited, thereby will have to rely on upslope component to enhance rainfall rates, so isolate flash flooding is possible, but more longer term >6hr flooding is more likely. Saturated ground may also result in downed trees and rock or mud slides. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...Flood Watch through Monday evening for VAZ007-009>018-022>024- 032>035-043>046-058-059. NC...Flood Watch through Monday evening for NCZ001>006-018>020. WV...Flood Watch through Monday evening for WVZ042. && $$ SYNOPSIS...KK/WP NEAR TERM...DS/KK SHORT TERM...AMS LONG TERM...AMS AVIATION...DS/KK/WP HYDROLOGY...KK/MBS/WP
Area Forecast Discussion
National Weather Service Tampa Bay Ruskin FL
854 PM EDT Sun Apr 23 2017 .UPDATE (Overnight and Monday)... 00z water vapor and H4 RAP analysis shows southern stream shortwave energy that crossed the southern half of the Florida peninsula today beginning to exit into the Atlantic, with deep layer subsidence and drying overspread the Florida peninsula in its wake. Further upstream, a large closed upper low feature can be seen spinning over the TN valley this evening. Associated with this system, a surface cold front trails southward into the northeast Gulf of Mexico. Regional radars show that this front is supporting areas of showers and storms across the the Carolinas/Georgia and into the FL panhandle. However, further south from here, the shower activity becomes very limited over the NE Gulf as the convection becomes removed from the best synoptic lift/Qvector convergence ahead of the upper low, and the updrafts encounter fairly hostile thermodynamic conditions above 10,000 feet. This situation looks to hold through the overnight into Monday morning as the whole system shifts eastward and the front approaches the FL west coast. A few scattered showers can not be ruled out, and the forecast will show 20-30% rain chances through Monday morning, however, the hostile conditions aloft and the continued main synoptic influence staying along and north of the I-10 corridor suggests that measurable rainfall for all is highly unlikely, and those that do see a showers will certainly not consider the amounts a drought-buster. Those down toward the Fort Myers area were lucky enough to see some good rainfall earlier Sunday associated with the passing shortwave trough mentioned above, but not much more additional rain should be expected with this next system. The last of the widely scattered showers will exit the region toward midday as the cold front moves into the Atlantic. Much of Monday will be characterized by more clouds than sun and a developing gusty NW wind. The most clouds should be closer to the coast as conditions appear to favor quite a bit of statocu migrating onshore. The further inland one goes, and the further into the diurnal heating cycle we get, these stratocu should transition to a sct-bkn cumulus field. Little chance of any diurnal showers Monday afternoon...as the synoptic flow will far overpower/prevent any defined sea-breeze, and the moisture layer will become ever more squeezed/shallow from above. Those with boating plans on Monday, either on the eastern Gulf, or an inland lake, should be prepared for rather gusty NW winds, sustained in the vicinity of 15 knots with gusts likely over 20 knots at times. So, rather choppy conditions developing Monday on the water as we head through the morning hours and through the entire afternoon. && .AVIATION (24/00Z through 25/00Z)... Potential for any isolated sea-breeze showers seems to be diminishing. Will have prevailing VFR through the remaining evening hours. Good potential for developing/lowering cigs late overnight, and have included all terminals with MVFR cigs between 09-14Z. Some potential KLAL/KPGD might see a period of IFR, however, confidence too low to include in this TAF package. Cold front slides through region Monday morning with winds increasing and becoming gusty during the mid/later morning hours. Gusts over 20kts are likely through a good portion of the day out of the W and NW behind this front. Post-frontal setup would suggest quite a bit of statocu off the Gulf through the day. Therefore, continued periods of MVFR 2-3KFT bases will be possible after 14Z through at least the early afternoon. && .MARINE... A COLD FRONT CROSSES THE EASTERN GULF OF MEXICO LATE TONIGHT INTO MONDAY MORNING. A FEW SCATTERED SHOWERS ACCOMPANY THE FRONTAL PASSAGE...BUT NO WIDESPREAD RAINFALL OR THUNDERSTORMS EXPECTED. WINDS INCREASE BY LATER MONDAY MORNING AND REMAIN AT 0R NEAR CAUTIONARY LEVELS THROUGH MONDAY EVENING. HIGH PRESSURE BUILDS IN TUESDAY...PROVIDING LIGHTER WESTERLY WINDS. && Prev Discussion... /issued 258 PM EDT Sun Apr 23 2017/ SHORT TERM (Rest of today-Monday)... An upper low near the south-central Mississippi Valley this afternoon tracks southeast to the GA/SC border. A short wave trough over southern FL lifts northeastward and is absorbed into troughing from the upper low. At the surface a low in northern GA trails a cold front south across the FL panhandle then southwestward over the Gulf of Mexico. The surface low move to the Carolina coastal waters by late Mon afternoon with the front sweeping into the east Gulf tonight then across the state Mon. In response to the front and the upper level short wave trough...a surface trough over the straits from western cuba to the northern Bahamas lifts northeast and merges in the Carolina surface low. The deepest moisture...model PWAT values at 2 inches or more... which resulted in some record rainfall in the south has shifted away. However enough residual moisture...PWAT in the 1.5 to 2 inch range...and instability remain which along with sea breeze convergence and limited day time heating to support a chance of showers and a slight chance of thunderstorms through the rest of the afternoon. There should be a break in rainfall from late afternoon or early evening through the later night hours. But expect some cloudiness along with patchy late night fog...especially in areas that received rain. Slightly deeper moisture returns with the front but limited with PWAT in the 1 to 1.5 inch range...enough for scattered showers or a few thunderstorms. The front and associated weather begin to impact...the Nature Coast in the pre-dawn hours...the Tampa Bay area around sunrise...Southwest Florida around mid-afternoon...then exits by late afternoon. Winds will pick noticeable with the front but will mainly be of concern for aviation/marine interests. MID TERM/LONG TERM (Monday Night-Sunday)... Monday night into Wednesday the mid/upper level shortwave trough will continue to move up along the eastern seaboard away from the region followed by ridging gradually build over Florida as a deepening trough sets up over the western half of the CONUS late in the week through the weekend. At the surface weak high pressure will be over the area for Monday night through Thursday, then late in the week into the weekend a stronger high pressure will build in from well out in the Atlantic Ocean. For Monday night into Tuesday night a low level west to northwest flow will be in place bringing some cooler and drier air into the region under fair skies. During Wednesday and Thursday the flow will shift to south to southwest with limited moisture continuing across the region so expecting mostly clear to partly cloudy skies with rain chances less than 10 percent. For Friday through Sunday the low level flow will shift to southeasterly with moisture gradually increasing leading to some additional clouds. There will be a slim chance, less than 20 percent, for a light shower/sprinkle Friday, then over the weekend some more moisture could move into the region leading to a few showers, but will keep rain chances at around 20 percent at this time as moisture does not look that deep. Temperatures will be close to normal for Monday night and Tuesday then as the ridging builds aloft we`ll see a gradually warm up a couple of degrees each day reaching the mid 80s coast to the lower 90s inland for Friday through Sunday. FIRE WEATHER... Recent heavy rainfall...especially in the south...along with more limited rain as a cold front moves through late tonight and during Mon will provide enough moisture to preclude any low RH concerns for the next few days. $$ && .Preliminary Point Temps/PoPs... TPA 70 77 65 80 / 10 20 0 0 FMY 69 80 65 82 / 10 20 0 0 GIF 67 79 60 83 / 20 20 0 0 SRQ 70 76 64 80 / 10 20 0 0 BKV 66 76 56 81 / 20 20 0 0 SPG 70 76 65 79 / 10 20 0 0 && .TBW WATCHES/WARNINGS/ADVISORIES... FL...None. Gulf waters...None. && $$ UPDATE/AVIATION/MARINE...Mroczka PREVIOUS DISCUSSION...RUDE/CLOSE