Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 01/26/21

Area Forecast Discussion
National Weather Service Columbia SC
1001 PM EST Mon Jan 25 2021 .SYNOPSIS... A warm front over the central Midlands this evening will lift northward through the northern Midlands overnight. A cold front will push into our area on Tuesday and stall. Surface low pressure will develop over the Southeast and bring more widespread showers Wednesday into Wednesday night. High pressure will build into the southeastern states late in the week into the weekend bringing cool, dry weather. && .NEAR TERM /UNTIL 7 AM TUESDAY MORNING/... Update: Warm front making little progress through the central Midlands this evening. As a result visibilities have deteriorated across the eastern Midlands. Have included portions of the eastern Midlands in the Dense Fog Advisory. Both the HRRR and RAP indicated the warm front slowly lifting north through the early morning hours. Low visibilities may linger across the northern Midlands and Pee Dee Region through the predawn hours. Previous Discussion: A warm front, bisecting the Midlands this evening will move northward overnight. Wedge-like conditions affecting the Northern Midlands and Pee Dee Region will hold low clouds and fog in place until the warm front lifts north. No significant rainfall is expected for most of the night given weak isentropic lift. However, may see the chance for showers return across the Piedmont and western Midlands toward dawn as a cold front approaches from the west. A non-diurnal temperature trend is expected with temperatures actually warming across the north Midlands as the warm front lifts north. Low temperatures should range from around 50 near the SC/NC border to the lower 60s across our southern counties. && .SHORT TERM /7 AM TUESDAY MORNING THROUGH WEDNESDAY/... A weak cold front move into the forecast area (FA) on Tuesday. It will be a warm day with ridging aloft and warm advection ahead of the front. Expect highs to generally be in the mid 70s. As the main surface low shifts further north, the front will slow and eventually stall near or over the southern forecast area. Possibly along a line from AGS to MYR. Warm, moist low-levels and weak convergence along the front will support shower activity, the bulk of which will shift southward during the day with the front. Coverage should be rather scattered with westerly 850 mb flow and little upper level support. Thunderstorms will be possible given the warm, moist conditions near the surface. SFC LI values around -1 to -3 with SFC based CAPE values around 500+. The highest thunderstorm chances will be in the southern FA which will be in the deepest part of the sector for much of if not the entire day. Weak conditional instability and lack of upper level support will limit the severe weather threat. The stalled front will be picked up by an upper level trough moving into the eastern US on Wed. In response, an area of low pressure will develop along the frontal boundary across the Carolinas during the day on Wednesday. Increasing moist south/southwest flow will develop across the are Tuesday night into early Wednesday. Showers are expected to be more widespread with this system than the one on Tuesday. Rainfall is likely from early Wednesday morning into the late afternoon hours. Showers may be heavy at times with PW values approaching 1.5 inches Accumulations should generally range from 0.5 to 1.0 inches will locally higher amounts. Models suggest the warm sector should remain south of the area in southern GA and possibly into the Lowcountry. In addition, overcast skies and rain should keep temperatures in the mid to near 60 degrees. Depending on the timing of the colder drier air behind the system on Wednesday/Wednesday night. Parts of the Midlands and Central Savannah River could experience record high low temperatures for Tuesday the 26th. The record high low temperature at Columbia is 60 degrees set in 1943. The record high low temperature at Augusta is 63 degrees set in 1943. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... The area will get a reprieve from clouds and rain from Wednesday night through Saturday. Behind the system on Wednesday night, seasonably chilly high pressure will settle southward from central Canada into the OH Valley and into the Carolinas through Saturday. This pattern supports dry weather with temperatures near or below normal Thursday through Saturday. Another vigorous system will eject from the southwest part of the country and move northeast toward the Great Lakes Sat into Sun. This will bring another chance for showers Sat night into Sunday. Temperatures will warm slightly so that most locations will see temperatures around/slightly above normal for Sunday and Monday. && .AVIATION /03Z TUESDAY THROUGH SATURDAY/... 03z Update: Made a couple of minor tweaks to the 03z amendment. 1, I pushed the arrival of the low MVFR cigs back an hour everywhere. Guidance is a bit slower than it was earlier. It has developed across Alabama and Georgia ahead of the front, so confidence is high that it`ll move into the area late tonight. Additionally, added VCSH to all the TAF sites. I may be a bit slow to bring that everywhere but OGB, but I didn`t want to complicate the TAFs. CAMs generally bring showers into the area between 12z and 15z, and a bit later at OGB. Otherwise, the forecast is on track. Previous Discussion: Slow moving warm front that was bogging us down in restrictions earlier today has now progressed north of all TAF sites, albeit only marginally. This has allowed warm air to filter into the region, and has helped to lift cigs into VFR (generally in the 4000-6000 foot range). This is expected to continue as we head into this evening. Uncertainty develops overnight, as most guidance hints at the redevelopment of cig restrictions across the area. This looks to occur as more moisture advects into the region ahead of an approaching surface cold front. The severity and duration of these restrictions is up for debate, though, and guidance is very inconsistent on those two things. Still, almost all bring cigs down again for some time tonight. The best overlap is for low MVFR cigs at all sites, beginning at AGS/DNL around 07z and at CAE/CUB/OGB around 09z-10z, and lasting through early afternoon. Some guidance (such as the HRRR) only keeps restrictions in through 14z, but has them as IFR cigs. Others (GFSLamp/CONSShort) have a longer duration event (through 19z-21z) with cigs around 1200-1500 feet. I tried to split the difference as much as possible, and trend towards IFR cigs in case more guidance latches onto that idea later. Either way, it looks like cigs restrictions will be the main issue during the period. Towards the end of the period, the passage of the cold front should help alleviate any restrictions we still have. I have a feeling OGB will be a tough one tomorrow, as the cold front will be arriving later there, and will be slowing down quite a bit. Winds ahead of this front will be breezy beginning later tonight. Expect generally southwest flow, with 6-10 knots rising to 10-14 knots by mid morning. Gusts of upwards of 20 knots can be expected. This will wind down towards the end of the period as the front passes and the sun sets. EXTENDED AVIATION OUTLOOK...Periods of restrictions expected through Wednesday night as additional systems move through the region. && .CAE WATCHES/WARNINGS/ADVISORIES... GA...None. SC...Dense Fog Advisory until 4 AM EST Tuesday for SCZ016-022-029- 031-038-115-116. && $$ SYNOPSIS...99 NEAR TERM...99 SHORT TERM...99 LONG TERM...99 AVIATION...99
Area Forecast Discussion
National Weather Service Cheyenne WY
735 PM MST Mon Jan 25 2021 .UPDATE... Issued at 731 PM MST Mon Jan 25 2021 Updated forecast for tonight to extend the coverage of fog for the high valleys west of the Laramie Range. Rawlins, Elk Mountain, and Arlington are all reported fog with visibilities below one mile. Will continue to monitor webcams for visibilities dropping below one half mile, but do not expect a considerable coverage & duration of dense fog at this time. Otherwise, current forecast looks. Lowered POP a bit with across the eastern plains with accumulating snowfall looking unlikely at this time given very low snowfall rates. A better chance for snow is possible Tuesday afternoon and Tuesday evening, but amounts will be light. && .SHORT TERM...(This evening through Thursday) Issued at 140 PM MST Mon Jan 25 2021 Current conditions...Cold front analyzed on surface analysis from Cody to Rawlins to Laramie...south into central Colorado this afternoon. Widespread low clouds in upslope easterly flow being seen on satellite imagery across much of the CWA. Panhandle airports still IFR/LIFR in stratus and fog...while Cheyenne just came down as winds shifted northeasterly. These low clouds may stay in for a while as HRRR Aviation product showing widespread solid low conditions through at least Tuesday morning. Latest HRRR and Hires NMM mesoscale guidance for PoPs mixed on snow through the afternoon and overnight. HRRR showing only scattered snow...while Hires NMM showing fairly widespread snow across the Panhandle. Decided to keep going PoPs going as they are through the overnight hours. Either way...not a lot of accumulations expected and the NAM guidance has really backed off on accumulations over the Panhandle. No winter headlines expected. Light QPF seen on ECMWF along the I-80 Corridor for Tuesday with heavier snow south in central Colorado. Would foresee conditions similar to today with low clouds and cold temperatures as southeasterly upslope flow continues. Winds don`t shift west until Tuesday afternoon after 00Z. For Wednesday...upper ridge begins to build into southeast Wyoming with increasing 700mb westerly winds. Craig to Casper 850/700mb height gradients up to 52/40mtrs respectively Wednesday afternoon with elevated winds for our wind prone areas. Right not think high wind headlines are needed as 700mb winds only get to 40kts across southeast Wyoming...but bears watching. .LONG TERM...(Thursday night through Monday) Issued at 140 PM MST Mon Jan 25 2021 Mild conditions across the CWA Friday with an upper ridge slipping to the east of the area. Weekend looks to see a return to cooler and blustery conditions as a potent shortwave moves across the southern Rockys into the southern and central plains. Pressure gradients get in the 60-70m range Saturday morning so wind-prone areas may see some strong winds. Not much in the way of pcpn with this system here given its southerly track. Sunday and Monday look to be dry and mild with upper ridging moving across in a progressive flow pattern. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 421 PM MST Mon Jan 25 2021 Wyoming TAFS...VFR at Rawlins, with occasional MVFR until 03Z, then IFR from 10Z to 15Z, then MVFR until 19Z, then VFR. Occasional IFR at Laramie until 04Z, then MVFR until 16Z, then VFR. IFR at Cheyenne until 16Z, then MVFR. Nebraska TAFS...IFR until 18Z, then MVFR. && .FIRE WEATHER... Issued at 140 PM MST Mon Jan 25 2021 Minimal fire weather conditions expected through at least Thursday as cold temperatures remain in place. Some areas east of the Laramie Range expected to receive at least a half inch of snow...with portions of the Nebraska Panhandle receiving 1-2 inches. Warmer...drier and windier conditions to end the week with temperatures climbing into the 50s in the Panhandle and mid 40s to near 50 in southeast Wyoming. Still...afternoon humidity expected to stay well above critical levels into the weekend. && .CYS WATCHES/WARNINGS/ADVISORIES... WY...None. NE...None. && $$ UPDATE...TJT SHORT TERM...GCC LONG TERM...RE AVIATION...RUBIN FIRE WEATHER...GCC
Area Forecast Discussion
National Weather Service Des Moines IA
725 PM CST Mon Jan 25 2021 ...Winter Storm Update... .UPDATE... Issued at 725 PM CST Mon Jan 25 2021 Moderate to heavy snowfall has been steady across much of central into southern Iowa as strong lift through the dendritic growth zone continues to make this event an efficient snowfall producer. As of early evening the axis of heaviest snowfall has contracted a little bit over central Iowa, but is still dumping snow at 1-1.5 inches per hour over locations in and around the DSM metro. RAP model suggests a few more hours of these heavier rates are possible with robust lift and supersaturation with respect to ice through the DGZ. Peak snowfall intensity wanes by later this evening, but light to moderate snow will linger overnight into Tuesday morning as the forecast area remains under a zone of mid- level confluence and positive PV advection aloft as the parent upper low is slow to push through. Dry air entrainment into the southern flank of the low may lead to a loss of ice in the cloud layer over far southern into southeast Iowa, which could flip ptypes over to freezing rain/drizzle. Short term model soundings barely hang on to snow, but will continue to monitor and update as needed. The heaviest storm totals will be focused from southwest Iowa to near the I-80 corridor in central Iowa. SLR reports suggest a higher SLR snow in this area compared to further south and east. The higher snowfall rates this evening mostly overlap the same locations that have seen heaviest snowfall so far, so expecting that we will see reports of a foot or more in some locations by Tuesday morning. Dry air continues to eat into the northern edge of this system, drastically limiting snowfall potential in northern Iowa. Some snowfall may eventually make it as far north as Algona and Mason City, but amounts will be light compared to the rest of the area. && .DISCUSSION.../Tonight through Monday/ Issued at 242 PM CST Mon Jan 25 2021 ...Impossible Travel at Times into Tonight over Southern and Central Iowa as Major Winter Storm Impacts the State... Highlights: -- Major winter storm bringing severe impacts including impossible travel -- Light snow over southern Iowa Tuesday night/early Wednesday] -- Very cold conditions Thursday morning -- Another round of precipitation next weekend Details: GOES-East upper level water vapor imagery shows the shortwave trough lifting over the western Plains this afternoon. A warm conveyor belt is into the Ohio Valley while the cold conveyor belt extends back through Iowa into Nebraska. At the surface, flow is from the northeast advecting in dry air into the low levels. 12z RAOBS from GRB, MPX, and ABR have a wealth of dry air in their profiles. The 12z DVN RAOB was becoming saturated, but still had dry air in the 800 to 500mb layer. Farther west and southwest, OAX and TOP soundings were saturated with precipitation ongoing at 12z. Warm air advection ahead of low pressure moving out of central Oklahoma and lifting toward St. Louis by late today will help to saturate the atmosphere gradually from south to north. High resolution soundings have shown the dry air being eroded from top to bottom in the profile with saturation and snow beginning late this afternoon or this evening along the Highway 20 corridor and likely after midnight along the Highway 9 corridor. Once saturation does occur, snow rates will be intense with cross sections showing deep layer of saturation with moderate to strong lift within the dendritic growth zone. Snow rates from the 9z SREF and 12z HREF show high probabilities of greater than 1"/hour snow rates moving in from our southwest early this afternoon into the Des Moines metro fizzling over central Iowa this evening. HREF snowband probability is also showing this as well, though the demise of the band and high rates is a bit sooner. This timeline of snow rates lowering overnight seems reasonable given the decreasing lift shown in the model cross sections. Last night`s trend with the 00z suite of models was to lift the snowfall northward. This trend has held this morning with the alignment of the highest snow axis from southwest into central and east central Iowa. The tight gradient remains over northern Iowa with parts of our northern counties likely to have little if no accumulation as dry air continues to advect in at low levels. Farther south, National Blend was indicating some mixed precipitation in our far southeast after midnight tonight. Deterministic sounding data does not support this change over. However, it is possible that some of the ensemble soundings do lose their ice introduction if they bring the dry slot farther north and into southeast Iowa. Observational trends will need to be monitored for possible lower snow totals over the far south and a change over away from snow. Overall, impacts will remain severe with travel likely impossible late this afternoon into tonight over southern and central Iowa with the high snow rates with visibility reduction being enhanced and lowered due to blustery winds blowing the snow. Snow totals have not greatly changed, but with snow lingering tomorrow morning have pushed the advisory and warning out until midday/18z. It is possible western portions of these headlines can be cancelled early as snow ends from west to east across the state, but travel impacts will likely linger longer. The shortwave trough dropping into the western US trough today will advance eastward and pass through the central US around midweek. While the bulk of the QG convergence will pass south of the state, enough lift and saturation will occur over southern portions of the state for some light snow. Accumulations are looking around or under an inch for those areas. High pressure moves across the northern and central Plains Wednesday night into Thursday. This will create one of the colder mornings with Des Moines right around 0 degrees. By late this week, a longwave trough will be moving ashore the western US. Lee side cyclogenesis will occur by Friday and this will help to aid in milder air moving into the region along with a deep fetch of moisture from the southern Plains/Gulf of Mexico. There are hints of light QPF amounts as early as Thursday night into Friday as isentropic lift increases over the state. More consensus that precipitation, whether rain, wintry mix, or snow, will start Friday night or early Saturday lasting through much of the day Saturday. && .AVIATION.../For the 00Z TAFS through 00Z Tuesday evening/ Issued at 527 PM CST Mon Jan 25 2021 Moderate to heavy snowfall will significantly impact flight categories over the southern half of Iowa through the evening into the overnight hours. Lighter intensity snow to the north may only result in IFR to MVFR restrictions, but tempo LIFR cannot be ruled out. Gradually improving conditions are expected as the snow steadily moves out Tuesday morning and afternoon. && .DMX WATCHES/WARNINGS/ADVISORIES... Winter Storm Warning until noon CST Tuesday for IAZ033>039- 044>050-057>062-070>075-081>086-092>097. Winter Weather Advisory until noon CST Tuesday for IAZ016-017- 023>028. && $$ UPDATE...Martin DISCUSSION...Ansorge AVIATION...Martin
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
957 PM EST Mon Jan 25 2021 .UPDATE... After a few hours of delay during the late night, snow remains on track to affect the morning commute in the Detroit metro area while spreading quickly northward toward Flint, the Tri Cities, and northern Thumb during the morning. A period of higher rate snowfall is expected to limit visibility and produce hazardous driving conditions. Observations during the evening indicated some flurries managed to drift north of the Ohio border only to be driven back by dry air in the low levels. This is expected to delay onset of meaningful snowfall until later in the night in our area. Meanwhile, the combination of upstream observations and incoming model data is building a more impressive case for a burst of heavier snow for SE MI during the morning until early afternoon. Ongoing activity over the Midwest is a combination of very respectable mid level deformation acting on a well-developed 850 to 700 mb trowal producing generous areal coverage of 1/2 to 3/4 sm snow in Iowa. Incoming model data maintains the strength of this configuration through Lower MI during the morning, sweeping through the Detroit area then primarily affecting locations along and north of I-69. Cross sections indicate a textbook profile of theta-e exhibiting low stability within the trowal axis and convective potential along the south flank centered on 15Z. This matches up with a broad area of higher vertical motion in the 850-500 mb layer reaching 10-15 ub/s in the latest 00Z NAM and RAP solutions. Low level moisture is plentiful with 3 g/kg specific humidity reaching as far north as Saginaw after 12Z. That being said, and as highlighted in the 4 PM discussion, there is concern regarding snow to liquid ratio in this case and the latest model soundings continue to support these concerns. A shallow DGZ near the top of the moist layer, riming and fracturing in a warmish low level thermal profile and a strong wind profile below 700 mb are limiting factors for confidence in double digit ratios. In-house probability guidance also points to lower expectations on ratio, rate, and accumulation. Balancing the observed dynamic forcing with ratio limitations suggests a cautious boost in snowfall totals into the 3 to 5 inch range centered on I-69 northward along with inclusion of some stronger wording in the advisory for higher snowfall rate. After an early morning burst, intrusion of the dry slot still cuts off activity in the Detroit area by 10 AM or so followed by pockets of freezing drizzle until temperatures inch above freezing by early afternoon. && .PREV DISCUSSION... Issued at 705 PM EST Mon Jan 25 2021 AVIATION... Low level dry air makes a fragile push from Ontario into SE MI which acts to break up MVFR ceiling briefly during the evening. The dry air also helps hold off the onset of snow for a couple hours longer after midnight with some virga indicated on radar over the region. However upstream observations depict an impressive pattern of snow moving in from the Midwest which is expected to reach the southern MI border after 06Z and then spread northward during the late night. At least borderline LIFR/IFR visibility is expected at the peak during early to mid morning. Conditions for freezing drizzle also continue to look favorable as dry air surges into the mid levels over the DTW corridor during Tuesday morning. It will be light using MVFR visibility as a proxy for intensity until observations can offer some additional guidance and before temperatures creep above freezing by Tuesday afternoon. IFR ceiling and visibility hold otherwise as the band of snow shifts northward toward FNT and MBS and lasts into Tuesday evening. For DTW... VFR below 5000 ft to occasionally MVFR is the condition for this evening before ceiling lowers and snow begins 07-08Z. The peak of the event occurs toward sunrise with visibility dropping to around 1 mile a times and with accumulation around 2 inches most likely before a transition to freezing drizzle occurs by mid morning. Only very light icing is expected on top of freshly fallen snow until temperatures rise slightly above freezing by Tuesday afternoon. DTW THRESHOLD PROBABILITIES... * High for ceiling below 5000 feet tonight. * High for snow tonight and early Tuesday. * Moderate for freezing drizzle mid to late Tuesday morning. * Low for ceilings or visibilities to drop below 200ft or 1/2SM respectively. PREV DISCUSSION... Issued at 354 PM EST Mon Jan 25 2021 DISCUSSION... Subtle height increases today in the wake of a passing cold frontal boundary. This is leading to subtle upper height rises with dry and stable conditions under lower level easterly flow through the remainder of the daylight hours. Increasing mid to high clouds in advance of the next system along with the resident thermal profile is bringing temperatures this afternoon at or near the freezing mark, which is right around seasonal averages. Main focus for this forecast is on the upcoming winter system expected to pass through southeast Michigan starting tonight and continuing into tomorrow. The upper low in the lee of the Rockies can be seen on satellite pushing the central plains this afternoon with low level warm frontal zone producing widespread precipitation across the Ohio Valley. This area of greater moisture and warm frontal zone is expected to hold south of Michigan. However, a zone of modest moist isentropic ascent is expected along a 800-700 mb frontal zone that will cross through southeast Michigan tonight. There will still be decent moisture feeding this frontal slope with specific humidity values generally around 3 g/kg. Guidance leading into this event has slowed the progression across the area with later arrival times throughout tonight. Anticipate the snowfall to lift across the OH/MI this evening sometime between the 8 pm to 10 pm time frame. Snowfall will then slowly expand northward through the early morning hours with higher rate snowfall possibly not moving over the I-69 corridor until about 3 am or shortly after. Survey of forecast soundings through the event depicts somewhat underwhelming thermal profiles in the moist layer (~925-600 mb) with temperatures residing around -4 to -5 C across southern areas and areas to the north at around -8 to -9 C. This would lean towards snow to liquid ratios on the wet to normal side (8:1 to 12:1 range) throughout this event. QPF totals through the event mostly come in around the 0.20 to 0.35 inch range, which would result in snowfall amounts mostly in the 1 to 4 inch range. The mid level dry slot remains a concern with this event, which is forecast to push northward Tuesday morning. This would effectively compromise the higher end snowfall amounts and also bring a period of light freezing drizzle as the mid level dry air strips moisture from the DGZ. The light freezing drizzle scenario is especially true for the southern portions of the forecast area, but impacts expected to be limited given it will fall onto earlier snowfall. This has also lead to latest guidance directing greater moisture/forcing and axis of higher snowfall amounts along portions of the I-69 corridor and points northward. Have made minor adjustments to the previous forecast snowfall amounts with most of the area remaining under 4 inches. The overall character of this event at the moment remains a borderline Winter Weather Advisory event with most locations receiving 1 to 4 inches snowfall over 8 to 12 hours. The wintry mix in the form of light freezing drizzle across the I-94 corridor and to the south will bring minimal ice accumulations. Have opted to just go forth with issuing a Winter Weather Advisory with the potential impacts to the morning commute. The synoptic forcing will weaken throughout the day Tuesday leading to decreasing precipitation and lower rate snowfall as the wave begins to shear out. A weakening frontal zone along with northeasterly winds off Lake Huron will allow for some lighter snowfall and additional light accumulations into the late afternoon and evening time frame, especially across Saginaw Bay and shorelines of the Thumb region. Lingering snowfall eventually comes to an by Tuesday night. The mid to late week time frame places southeast Michigan between southern and northern stream waves with generally dry conditions. Some colder temperatures push into the region bringing a stretch of below normal temperatures. High temperatures generally in the 20s and overnight lows in the teens to single digits. MARINE... Northeast winds will continue to be on the increase this evening as low pressure moves into the Ohio Valley. Winds gusts still expected to reach around 25 knots over Western Lake Erie, but with precipitation drag issues tonight, 30 knots will probably not occur. Even so, with the longer fetch, some 4 foot waves should brush the nearshore zone. As the low continues north, northeast winds over Lake Huron will also reach 25 knots tonight into Tuesday, especially over Saginaw Bay where the fetch is maximized. The prolonged onshore flow should have no problem with waves aoa 4 feet impacting the nearshore waters, and small craft advisories remain in effect, with the exception of inner Saginaw bay due to ice cover. In addition to the increased wind and waves, snow will overspread the region from south to north this evening into Tuesday, with visibilities reaching 1 mile or less at times. As the low exits east, winds become northerly Tuesday night into into Wednesday, but should mostly hover around 15 knots before increasing again Wednesday evening into Thursday as cold blast leads to increased mixing depths. Thus, there remains a good chance the small craft advisory will need to be reissued or extended as waves look to remain elevated through the end of the work. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...Winter Weather Advisory from 1 AM to 4 PM EST Tuesday for MIZ047>049-053>055-060>063-068>070-075-076-082-083. Lake Huron...Small Craft Advisory until 5 AM EST Thursday for LHZ421-441>443. Lake St Clair...NONE. Michigan waters of Lake Erie...Small Craft Advisory until 10 AM EST Tuesday for LEZ444. && $$ UPDATE.......BT AVIATION.....BT DISCUSSION...AA MARINE.......SF You can obtain your latest National Weather Service forecasts online at
Area Forecast Discussion
National Weather Service Huntsville AL
819 PM CST Mon Jan 25 2021 .NEAR TERM...(Tonight) Issued at 819 PM CST Mon Jan 25 2021 02Z mesoanalysis shows a CAPE axis just west of the MS-AL line, near where a broken line of showers is firing over NE MS, and where a cyclic supercell is ongoing near the MS Golden Triangle. Farther to the east, a band of showers and storms has been ongoing between Huntsville and Birmingham for the last several hours--perhaps along a warm front of sorts--but these storms appear to have been mostly elevated in nature. MU/MLCAPE and low-level lapse rates drop off rapidly as you progress east, but mid-level lapse rates steepen somewhat, shear is more than enough, and convergence is sufficient to keep storms going. There were a few reports of penny to dime size hail over Sand Mtn with earlier storms. On the other hand, despite better convergence and a relative CAPE max, the NE MS storms have struggled to intensify. The band of storms to the south may be interrupting the inflow of rich high theta-e air into the NE MS storms, limiting their potential. Additional scattered showers (such as those developing over NW AL) may continue to cut off the inflow. The most recent HRRR run weakens the NE MS storms in favor of the southern band as the evening wears on. It is also interesting that the HRRR resolves a swath of 0-3km updraft helicity near where the cyclic supercell is located in eastern MS, and brings it up into far southern Cullman County late this evening (around 05Z). So while storms across the southern CWA have been mostly elevated so far, it is still possible that they will become more surface-based later tonight--and the wind threat (and yes, tornado threat) may not be over until later. .SHORT TERM...(Tuesday through Wednesday night) Issued at 205 PM CST Mon Jan 25 2021 Tuesday will be another mild day, but with sunshine as the frontal band shifts to the Gulf Coast through southeast GA. Expect highs in the middle to upper 60s. A shallow cold front will drop in Tuesday evening as the area remains beneath strong southwest flow at 7-5h in advance of the next wave ejecting from the desert Southwest. The frontal band to the south will begin lifting northward as a low level jet develops. However, much of this moisture transport will shift through south AL into central GA/SC Wednesday morning into the afternoon. Our area may see a few showers as the upper trough quickly swings east and deamplifies through the TN valley during the afternoon. Cold advection will increase by late afternoon and evening, but not before subsidence and drying ends precipitation. Thus, not expecting snowfall at this point in our area, but to our northeast along the Cumberland Plateau. Much colder temperatures in the 20s are expected Tuesday night into early Wednesday morning. .LONG TERM...(Thursday through Sunday) Issued at 205 PM CST Mon Jan 25 2021 Heading into the end of the workweek, a ridge will amplify across the Plains as a trough deepens as it heads into the West coast. This will leave us in NW flow aloft and the sfc high pressure building in from Canada will bring a chill to the TN Valley. Look for daytime highs on Thursday to be 10-15 degrees colder than Wednesday only reaching the low to mid 40s. Despite plentiful sunshine, with breezy northwesterly flow ~10kts gusting slightly higher, it will make it feel even colder. Overnight lows will be chilly in the lower 20s. Dry conditions will persist into Friday but with lighter winds as high pressure moves in. The increase in heights and sfc winds becoming southerly will help daytime highs reach the lower 50s. The dry pattern won`t last long as a the previously mentioned West Coast trough will weaken as it swings towards the region this weekend but return showers to the forecast. With overnight lows Friday night/Saturday morning hovering around freezing, we could see a brief window around sunrise of a rain/snow mix before precip becomes, and stays, all liquid. Breezy southerly flow will provide an increase in moisture and push daytime highs into the mid 50s on Saturday. As a sfc low lifts into the Midwest, we will see showers increasing in coverage through the day, becoming numerous by Saturday night ahead with an increase of isentropic lift ahead of a warm front lifting northward. Showers will persist into Sunday before the cold front moves through and brings precip to an end by sunset. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 550 PM CST Mon Jan 25 2021 A bit of uncertainty exists for the TAF sites through the first 6 hours of the forecast period. Showers and thunderstorms ahead of a cold front will move across the area this evening. Cigs are expected to lower to MVFR over the next hour and cigs around 800 feet are possible as the storms move through. At this point, uncertainty is high as to the exact timing of storms and therefore have a TEMPO for the KMSL between 01 and 04Z and at KHSV between 03 and 06Z. Amendments may be necessary if storms develop sooner than expected. Gusty winds and hail will be possible in any storm that impacts the area. These storms will move east of the area by 06Z, with conditions expected to improve to VFR by 09Z. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...BCC SHORT TERM...17 LONG TERM...JMS AVIATION...73 For more information please visit our website at
National Weather Service Jackson KY
907 PM EST Mon Jan 25 2021 .UPDATE... Issued at 907 PM EST MON JAN 25 2021 Showers and thunderstorms continue to move rapidly eastward across the region, and the forecast still has this covered. Have adjusted temperatures through Tuesday morning based on obs and latest model guidance, but the changes are rather minor. Readings are expected to be nearly steady in our southern counties tonight, and rising in the north. && .SHORT TERM...(This evening through Tuesday night) Issued at 541 PM EST MON JAN 25 2021 Surface low pressure over the Ozarks will shift eastward through the overnight, riding up the Ohio River Valley. This slow moving system will lift a warm front northward through eastern Kentucky during the overnight period and then a cold front through the area by Thursday morning. WPC maintained an area of a marginal threat of excessive rainfall for the Commonwealth through tonight. Additional convection is firing upstream and short term high resolution models show that activity riding northeast into and through our area during the overnight. SPC mesoanalysis shows an upstream environment of 250-500 J/kg MUCAPE and effective shear of 35-60 kts. RAP forecasts show this environment lifting northeast into our area and SPC HREF suggests that mean 250-500 MUCAPE and shear will lift into eastern Kentucky over the next several hours. Thus maintained thunder through the evening as yet another round of precipitation pushes through the region. Already seeing a few stronger cells being highlighted by upstream WFOs. So an isolated strong storm with mainly gusty winds can not be completely ruled out. Brief, locally heavy rainfall will also be possible. Excessive runoff will cause local streams and rivers to swell through the day Tuesday. The current HWO has this handled. Once we get through tonight, sensible weather settles down considerably. Tomorrow, dry weather and sunshine will lift temperatures to around 60 across the south, and in the 50s across our north, where lingering clouds will help keep temps slightly cooler. .LONG TERM...(Wednesday through Monday) Issued at 541 PM EST MON JAN 25 2021 We begin the extended portion of the forecast Wednesday in a brief period of modest ridging aloft across the eastern Ohio Valley. Just to our west, a shortwave trough rides over the Middle Mississippi Valley. Ridging across the Rockies and western Plains separates this shortwave trough from a deeper trough of the northwestern US coast. The system at the surface that is currently bringing the widespread rainfall in the near term will have moved well off to our east at this point. Meanwhile, another area of low pressure will be beginning to develop in the deep south. The shortwave trough to our west will beginning to move over our area through the day Wednesday, while the surface low will continue to travel east and northeast across the Southeast, sending precip towards our area. Generally, precip is set to begin impacting the area not too long after 18z Wednesday afternoon. Most guidance is in fair agreement over the pattern evolution, other than the Canadian keeping the shortwave further to the west a little longer, consequently delaying the initial onset of precipitation. However, given that this solution is not as favored in ensembles, have elected to put less stock in it. With the surface low passing to our south, our area is kept in the cooler sector, allowing for some snow to mix its way in. Generally this change over will happen as a gradual transition from northwest to southeast, with the exception of the higher terrain generally transitioning earlier. Accumulations look to be modest, generally less than an inch, though higher amounts are possible in the higher terrain. Generally the precip will exit out to the east by Thursday morning as the surface low pushes east off the coast. Heights aloft will be on the rise through the day as ridging moves in from the west, while high pressure dominates at the surface. All combined, conditions will stay clear and dry through the first part of the weekend. However, the dry weather does not last. Another upper level trough will work its way towards the region over the second half of the weekend, supporting the development of a low at the surface over the Plains. This sends along our next round of precip, generally beginning Saturday afternoon. However, while there is more agreement over the general pattern, the specifics around the evolution of both the features aloft and at the surface are still not well resolved. So, have kept more in line with the thinking of the previous forecaster and kept the PoPs constrained to just likely given all the uncertainty. && .AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon) ISSUED AT 907 PM EST MON JAN 25 2021 Conditions at the start of the period ranged from VFR to LIFR, with the better conditions generally in our southern counties, and the worst in the north. Showers and a few thunderstorms continued to move rapidly east over the region. Strong winds just off the surface were bringing a threat of low level wind shear as well. The precipitation will persist this evening, but is expected to mostly move out to the southeast overnight. Wind shear should also subside overnight. However, flight categories are expected to worsen, with most places becoming IFR or worse overnight. Improvement is forecast on Tuesday morning, with a return to VFR for everywhere but north of I-64, with that scenario carrying over through the remainder of the period. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...HAL SHORT TERM...RAY LONG TERM...HAS AVIATION...RAY
Area Forecast Discussion
National Weather Service Louisville KY
629 PM EST Mon Jan 25 2021 ...Updated Aviation Discussion... .Short Term...(This evening through Tuesday) Issued at 345 PM EST Mon Jan 25 2021 Upper low over the Plains with an occluded 998mb sfc over SW Missouri this afternoon. Triple point is near the Bootheel, with the most solid precip shield north of the warm front in mainly central Kentucky. We have had a few strong to marginally severe storms across south-central Kentucky in a slightly better mixed environment, but that has been worked over and the unstable air mass is now confined to Tennessee. Main concern through this evening will be just how much additional rain falls, especially where the heaviest rain already fell across south central Kentucky. We could be looking at 1-2 inches of additional rainfall, and if it remains focused near the Western Kentucky and Bluegrass Parkways as currently progged, impacts should be limited to nuisance flooding. However, if heavy rain falls farther south where we are now fairly saturated, there could be more impactful flooding. Spotty convection is developing over western Kentucky and western Tennessee, and that pushes through late this evening. Latest HRRR actually takes that batch of rain across south-central Kentucky, which could raise flood concerns. Precip ends after midnight as the dry slot cuts in, but temps will remain nearly steady overnight. Sharp temp gradient expected to persist Tuesday as southern Kentucky clears out under the stronger westerlies aloft, while north central KY and southern IN remain fairly socked in. Better temp recovery in the south, where we could touch 60 again, while southern Indiana will be stuck in the mid 40s. .Long Term...(Tuesday night through Monday) Issued at 252 PM EST Mon Jan 25 2021 Upper level ridging along the eastern seaboard and deep troughing across south central CONUS will place the OH Valley under deep SW flow at the beginning of the long term. A 5H closed low over central US will continue tracking eastward, filling as it tracks over the southern OH Valley and northern TN Valley. Best chances of precip will begin Wednesday afternoon and continue through early Thursday morning. Sounding profiles would suggest mostly rain south of the Parkways and transitioning to mostly snow towards the I-64 corridor, but a rain/snow mix is likely between the two. EPS/GEFS members continue to show agreement on minor accumulations with up to 1 inch possible along our northernmost counties in Indiana and most locations receiving a half inch or less. Temperatures will fall into the low to mid 20s in the cold air behind the front, so impacts will likely include some slick spots on any untreated roads for the Thursday morning commute. Large amplitude ridging and Canadian high pressure moves over the region Thursday through the start of the weekend bringing cold but dry weather. Thursday will be the coldest with highs only reaching into the low 30s across southern Indiana and mid 30s across central KY. Friday morning will likely be the coldest morning of the week with lows in the upper teens to low 20s, but afternoon temps will recover nicely with the aid of WAA along southerly winds with highs in the 40s. Our next chance of rain will come Saturday as system approaches from the Central Plains. This looks to be an all-rain event lasting through Sunday. Finer details will come later as long range models reconcile differences. && .Aviation...(00Z TAF Issuance) Issued at 625PM EST Mon Jan 25 2021 KLVX radar showing another round of showers and storms working through the central Kentucky region. Expect to see ongoing RA or TSRA through the evening hours as the warm front lifts northward. By 06z tonight, most precip should be exiting the region, but the low ceilings and visibilities will stick around through the overnight hours. Guidance is strong on fog development and low ceilings keeping IFR or even LIFR possible during the 06-12z time period for SDF, LEX, and HNB. Wouldn`t rule out some VLIFR conditions either if vis drops below 1/2SM for some time. We will continue to monitor and amend if needed. Ceilings will finally start to break up mid/late Tuesday morning. Winds become more southwesterly tonight as the cyclonic flow spins out of the region. Winds will be gusty tomorrow, but mostly around 20kts for all terminals. && .LMK WATCHES/WARNINGS/ADVISORIES... IN...None. KY...None. && $$ Short Term...RAS Long Term...CG Aviation...CJP
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
935 PM EST Mon Jan 25 2021 .SYNOPSIS... Low pressure will pass through the area on Tuesday. An upper level disturbance is expected to pass through the area Thursday morning while low pressure develops well southeast of the area. High pressure will gradually build toward the area early next week. A storm system may impact the area next Monday. && .NEAR TERM /THROUGH TUESDAY/... EVENING UPDATE... As noted in the 00Z upper air from KIAD, a warm nose has developed around 850-mb which has led to more of a mixed wintry precipitation event than earlier suspected. A mixture of rain/snow was anticipated during the first phase of this system. Thus, expect some of the snow totals to be cut down given the widespread sleet reports from local spotters. 1 to 2 inches of snow will be the more likely outcome across the region. There currently is a brief lull in the action while upstream radar imagery shows another healthy band of precipitation heading across West Virginia. With the warm nose continuing to push northward based on HRRR solutions, expect a mix of sleet/freezing rain to be the main precipitation types during the overnight hours. This will lead to hazardous travel, especially on any untreated road surfaces. PREVIOUS DISCUSSION... There have been some notable trends in the 12Z model cycle today, more importantly, for a colder solution and also less QPF tonight with the heaviest precip aimed at the upslope areas of the Appalachians. Observational trends support this colder solution with sfc ridging still in place and current dewpoints still in the upper teens at BWI and lower 20s at DCA. It`s difficult to get all precip to be all rain when dewpoints are still so low. To add to the uncertainty is a deep isothermal layer right at freezing seen on model soundings. Only a degree or two degree difference could make a big difference in p-type and specific snow/ice amounts. Please refer to our snow and ice forecasts at Definitely expecting a period of wintry precip tonight before precip turns lighter overnight and Tue as mid-level dry slot moves in. Precip should end or if not exit the area by 18Z Tue, although some drizzle may persist across northeast MD longer. && .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... Tranquil conditions Tue night through Wed. Next upper level trough will swing through the area Wed night into Thu morning with light snow possible for areas south of U.S. Route 50. && .LONG TERM /THURSDAY THROUGH MONDAY/... For Thursday, models continue to suppress most of the wintry precip probabilities further south of our CWA. Any potential for bombogenesis would be later than the onset moisture/decreasing temperatures for our area to cause much of an issue. Still could see a period of rain/snow mix early on Thursday with any moisture that makes its way into the area along with temperatures forecasted to be below freezing for most areas west of I-95. Conditions will continue to cold and windy for the area Thursday night into Friday. A system to our NE Friday could continue to allow the chance for a few flurries to be mixed in with these gusty NW winds. Not expected much in terms of impacts for this time period but a northern shift in the track of the low pressure system could inhibit higher threat levels for impacts Thursday into Friday. High pressure builds in from the west Friday night and pushes offshore by early Sunday morning. This will allow for our next potential wintry system to take aim. With temperatures currently forecasted to be in the upper 30s to low 40s across most of the area Sunday, impacts for this system appear minimal currently. Onset precip may start out wintry before moving over to all rain for most of the duration of the event. With it still be 7 days out, conditions and impacts may change with any shift in parameters. Should be something to continue to monitor as we head closer to this event. && .AVIATION /03Z TUESDAY THROUGH SATURDAY/... IFR with occasional LIFR conditions developing this evening with a wintry mix of precip. Improving cigs Tue afternoon as precip ends. VFR conditions likely Thursday and Friday with some gusty NW winds on Thursday before diminishing as high pressure begins to move overhead for our area. Could see a few flurries and reduced instances of visibility but it will be brief in nature. && .MARINE... Light and variable winds through Tue evening. Possible SCA Wed in NW flow. Possibility for gales for the water between a low pressure system to our SE and an incoming high pressure from the west on Thursday. SCAs likely Thursday and Friday with that mentioning of gales possible. Winds will decrease Friday as high pressure briefly settles overhead. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...Winter Weather Advisory until 9 AM EST Tuesday for DCZ001. MD...Winter Storm Warning until 7 AM EST Tuesday for MDZ001-501-502. Winter Weather Advisory until 9 AM EST Tuesday for MDZ013-014. Winter Weather Advisory until 10 AM EST Tuesday for MDZ003>006- 008-011-503>508. VA...Winter Storm Warning until 7 AM EST Tuesday for VAZ503-504-507- 508. Winter Weather Advisory until 9 AM EST Tuesday for VAZ053-054. Winter Weather Advisory until 7 AM EST Tuesday for VAZ025>031- 038>040-501-505-506. WV...Winter Storm Warning until 7 AM EST Tuesday for WVZ050-055- 501>506. Winter Weather Advisory until 10 AM EST Tuesday for WVZ051>053. MARINE...None. && $$ SYNOPSIS...LFR NEAR TERM...LFR/BRO SHORT TERM...LFR/JMG LONG TERM...ADM AVIATION...LFR/BRO/ADM MARINE...LFR/ADM
Area Forecast Discussion
National Weather Service Marquette MI
658 PM EST Mon Jan 25 2021 .SHORT TERM...(This evening through Tuesday) Issued at 221 PM EST MON JAN 25 2021 Water vapor imagery and RAP analysis show a mid-upper level trough over the western U.S. and a low amplitude ridge downstream over the se portion of the U.S. Around a strong positive height anomaly/500mb anticyclone just n of Hudson Bay, mid-level troughing wraps from nw Canada se across northern Ontario and then off the east coast of Canada. Between the troughing to the n and the se U.S. ridge, confluent flow extends from the northern Plains eastward into the Upper Great Lakes. This confluence is supporting sfc high pres ridging extending from the Arctic through Saskatchewan southeast into the Upper Mississippi Valley and Upper Great Lakes. As a result with the slow progression eastward of this ridge, nw winds today will veer n-ne tonight into Tue. Light snow/flurries have been reported at KCMX, KIWD and KERY and noted on webcams out west and east today. Expect little if any snow accumulation through this afternoon based on very dry upstream 12z KINL sounding and fcst soundings showing inversion hgts 2-3 kft with dry air blo it. Northerly flow late today will veer to the nne to ne tonight. Fcst soundings indicate that inversions will remain low tonight into Tuesday at around 3kft. Combination of the low-inversion height and dry upstream air advecting over the lake will continue to be negatives for LES. However, the DGZ is fcst to dominate the cloud layer, so SLRs should be on the higher side with the developing - shsn/flurries. Light shsn/flurries will shift to the nne wind snowbelts and remain that into Tue morning before winds become a bit more northerly late Tue. Coverage will increase gradually tonight into Tue morning into the north central U.P. as the low-level flow becomes more cyclonic and convergent over eastern Lake Superior mainly due to the development of a land breeze off Ontario. Still, snow accumulations will be light tonight into Tue given the more dominant negatives previously mentioned. Expect snow accumulations out west to be generally a dusting to an inch tonight into Tue, with maybe 1-2 inches of accumulation possible into Baraga and Marquette counties where -shsn are more persistent and could be aided by convergent flow. Lows tonight should range from around 5F above interior w, where there will still be some breaks in the clouds, to mainly the teens elsewhere. Winds may veer sufficiently to the ene due to the Ontario land breeze for lower clouds to scatter out over the far e, so temps there may fall into the single digits as well. Highs Tuesday under mostly cloudy skies and a northeast to north flow will range from the upper teens west to the lower to mid 20s east half and south central. .LONG TERM...(Tuesday night through Monday) Issued at 252 PM EST MON JAN 25 2021 Little to no change in the longterm forecast from the past few cycles as Upper Michigan will see a prolonged period of light lake- effect snow with temperatures trending slightly abv normal by the weekend. Troffing in the west with slight ridging to the eastern CONUS is leading to active southern stream as a train of shrtwvs impacts the CONUS this week and into the weekend. An arctic high will extend a ridge towards Upper Michigan as light northerly flow will bring persistent, albeit light, lake-effect snow showers through Wednesday night. This high pressure moves overhead Wednesday night into Thursday, bringing some clearing skies and cooler night. By Friday, this high will be to the east of the UP as return southerly flow, brings a building ridge over Upper Michigan with slightly abv normal temperatures Friday and Saturday. Another shrtwv will move on shore in the desert SW Saturday, before lifting through the Central Plains Saturday night into Sunday. There is a non-zero chance that this system shifts north and moves through the UP, but so far deterministic and ens means are keeping it to the south and relatively weak. On Tuesday night, first wave on the train will be exiting across the northeast as the next wave ejects from the Rockies and into the Central Plains. A closed mid-level low will be dropping south from Ontario ahead of an arctic high pressure system as light northerly flow continues over Lake Superior. With model 850mb temps between - 17 to -19C, and saturation in the DGZ, some LES will be seen. Dry, Canadian air will be moving over the lake, though, as seen by the inverted V expect this to limit accums. Under the split flow regime, this closed mid-level low is slow to shift eastward as the Central Plains wave shifts through the Appalachians. This will bring a prolonged period of 60 hrs or snow of light lake-effect snow. This lake-effect snow will come to an end Wed night across the east as ridging and rising heights start to build into the west. This may bring some clearing, and with 850mb temps near -18C, could be in store for a colder night as high pressure shifts overhead. This high will slowly shift east through Thursday as LES comes to an end across the east Thursday aftn. A whopping 2 to 4 inches could be seen in the northerly wind snowbelts through Thursday, as snow showers will be hindered by the drier air. NAM has some run to run consistency on a convergent wind field across the east for Wednesday, which could bring just slightly higher snow totals, but not seeing anything close to advy levels. As the ridge moves overhead Friday and Saturday, temps climb to around 30 for some spots with some clearing skies. Models have some differences, but some WAA ahead of the next shrtwv could bring some light snow across the UP on Saturday as well as the increased cloudiness. Otherwise UP will remain unscathed for the most part from this shrtwv as models and their ens means show the wave remaining to the south through the Ohio River Valley, as the UP may pick up some lake-effect snow on the backside of the low. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 654 PM EST MON JAN 25 2021 Expect persistent MVFR cigs through the forecast period with n to nne winds off of Lake Superior bringing lake effect clouds and flurries into the TAF sites. As slightly colder air moves in late tonight into Tue morning, a brief period of IFR conditions may be possible. && .MARINE...(For the 4 PM Lake Superior forecast issuance) Issued at 221 PM EST MON JAN 25 2021 High pres will slowly build toward Lake Superior over the next several days with the ridge axis drifting across Lake Superior Thu into Fri. Until the ridge passes, expect northerly winds to prevail, though direction will vary between northwest and at times northeast. Wind speeds will be mostly under 20kt, but expect some periods with winds gusting up to 25kt. After the ridge passes, southeast winds will be on the increase Fri night into Sat with the approach of another low pressure trough from the Plains. Southeast winds will increase to 20 to 30 knots, highest over eastern and north central Lake Superior. && .MQT WATCHES/WARNINGS/ADVISORIES... Upper Michigan... None. Lake Superior... None. Lake Michigan... None. && $$ SHORT TERM...Voss LONG TERM...JAW AVIATION...JLB MARINE...Voss
Area Forecast Discussion
National Weather Service Nashville TN
535 PM CST Mon Jan 25 2021 .UPDATE... FOR 00Z AVIATION DISCUSSION. && .DISCUSSION... A line of heavy showers is currently moving across Middle Tennessee mainly north of I-40. These showers earlier produced some strong winds at the surface, but they have since diminished somewhat. An ACARS sounding for BNA taken at 1709Z shows very little CAPE with nearly total saturation from the surface up to about 650 mb. There is some speed and directional shear in the low-levels, but at this time helicities aren`t excessive. A warm front that moved northward through Middle Tennessee overnight has become quasi-stationary near the TN/KY border, so most of Middle Tennessee is now in the warm, moist sector. A pre-frontal trough will swing through the mid state later this afternoon and evening, and this will provide some focus for the expected storms. The HRRR does suggest some convective organization along this boundary, but given the lack of instability in this air mass, it still appears that the primary threats are going to be wind-related. SPC currently gives us a 5% risk of damaging winds and a 2% risk of tornadoes in the marginal/slight risk area, which covers nearly all of Middle Tennessee. Even though the bulk of the active weather will move across and exit the mid state overnight, the cold front won`t actually arrive until Wednesday. That`s going to be our next chance of rain, with perhaps some snow for the Cumberland Plateau Wednesday night. (It`s going to be another battle of cold air vs. moisture.) After that, look for cooler temperatures the remainder of the week, with perhaps a weekend cold front representing our next chance of rain. && .AVIATION... 00Z TAF DISCUSSION. Showers and occasional storms will impact BNA/MQY/CSV through the evening which will reduce vis to IFR conditions periodically. A surface front will move through the area from west to east which will shut off rain chances by 07z. Cigs will gradually improve to VFR for the remainder of the taf period by the morning. Behind the surface front winds will shift to the WSW. && .OHX WATCHES/WARNINGS/ADVISORIES... NONE. && $$ DISCUSSION......08 AVIATION........Reagan
Area Forecast Discussion
National Weather Service Pueblo CO
730 PM MST Mon Jan 25 2021 .UPDATE... Issued at 724 PM MST Mon Jan 25 2021 Based on latest HRRR and 00z NAM, plus persistent snow over nrn El Paso County, will expand Winter Wx Advisory to include the entire I-25 corridor and also the srn Sangres. Snow amounts on the low end of the advisory range, but with heavier snow falling over much of the area during/near the morning commute, impacts could be more significant. Other than adding the advisory and making some minor adjustments to snow amounts, forecast is in pretty good shape and won`t be making any major changes. && .SHORT TERM...(This evening through Tuesday) Issued at 250 PM MST Mon Jan 25 2021 ...More snow expected across southern Colorado tonight and Tuesday... First storm has pulled east of the area with wrap around snow continuing across the northeast portions of the forecast area...across Kiowa county. Roads have stayed fairly clear in spite of some moderate snowfall at times. This band will pull off to the northeast late this afternoon through the evening. Meanwhile, convective snow showers have developed across the mountains this afternoon which will continue to expand and become more widespread as southern Colorado comes under the influence of the next upper low across southern CA, which will lift northeastward through the Desert Southwest towards the 4 corners region tonight, then across southern Colorado on Tuesday. System develops 2 circulation centers as it crosses the mountains Tuesday morning and the leading impulse tightens up again across east central CO by mid day. Once again, the timing and exact track of this intensification will play a big role in snowfall amounts. Overall, this storm looks a little weaker than the last as far as upglide and development of the wrap around snow band/trowal. But this system will also be colder with persistent light snow expected to continue through Tuesday as trailing energy moves across. This could lead towards greater travel impacts for the urban corridor of southern Colorado. Overall, snowfall amounts are coming out on the light side of advisory range, so will issue Winter Weather Advisory for the southeast mountains and adjacent I-25 corridor from roughly Walsenburg northward. With some southeast to easterly upslope flow, expect some snow to spread up the Arkansas River Valley of Fremont county and perhaps into southern Chaffee county. Current advisories do not include the Sangre De Cristo mountains as of yet but an earlier storm intensification, or stronger upslope could necessitate upgrades. Northern El Paso county is another area to watch but for now we are keeping higher totals on the southern slopes of the Palmer Divide. A tad farther south track and the southern I-25 corridor down to Raton could also get in on the action, but with less of an upslope component down that way, have left them out for now. Expect some improvement Tuesday afternoon as focus for the heavier snow shifts eastward across the plains. Tuesday will be much colder with persistent cloud cover across southern Colorado. High temperatures will likely stay in the 20s across the lower elevations with teens and single digits across the higher terrain. .LONG TERM...(Tuesday night through Monday) Issued at 250 PM MST Mon Jan 25 2021 Tuesday night... The major shortwave with very cold air associated with it will be exiting the CWA with only a few lingering snow showers over the highest elevations of all mountain ranges. Some snow will still be possible over the plains as well due to the wrap-around moisture overrunning cold surface temperatures in the deformation zone. All precipitation should completely exit the region by midnight with clearing throughout early Wednesday morning. Wednesday through Friday... High pressure is going to dominate the area once the low pressure system exits the region by early Wednesday morning. Both of the GFS and ECMWF models are picking up on a weak upper level low from the subtropical ridge to the southwest over the Pacific Ocean that will absorb into the ridge and could allow for some higher level precipitous clouds over the region on Friday, while the mid and lower levels remain very dry. Friday night through Sunday... All of the deterministic models are in relative agreement with the timing of the next major shortwave trough to influence the CWA late friday night, except that the ECMWF has this system moving into the region about 3 hours earlier late Friday night. Due to the orientation of this trough, most of the precipitation will be confined to the mountainous areas of the CWA, especially for Saturday morning, where the greatest amounts of snowfall will be located on the southwestern facing slopes of the San Juan Mountains. The low pressure center associated with this trough will propagate quickly out over the Great Plains and not provide much in the way of any snowfall for the plains within the CWA. Sunday night through Tuesday... A ridge will begin to build back in with warmer and drier conditions for a majority of the CWA with only a few snow showers over the Sawatch range due to some troughing to the northwest of the region. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 250 PM MST Mon Jan 25 2021 VFR conditions are currently dominating at all locations for the moment. As the next low pressure system approaches, expect CIGs and vis to drop into IFR criteria for COS as early as 01Z due to -SN/BR, for PUB as early as 02Z, and for ALS as early as 03Z...and expect these conditions to prevail throughout the rest of the forecast period. && .PUB WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 5 PM MST Tuesday for COZ068-074- 075-084-088. Winter Weather Advisory until 8 PM MST Tuesday for COZ076-077- 079>083-085>087. && $$ UPDATE...PETERSEN SHORT TERM...KT LONG TERM...STEWARD AVIATION...KT