Forecast Discussions mentioning any of "HRRR" "RAP" "RUC13" "RUC" "RR" received at GSD on 12/28/21

Area Forecast Discussion
National Weather Service Amarillo TX
600 PM CST Mon Dec 27 2021 .AVIATION...VFR conditions will prevail at all TAF sites over the next 24 hours. Winds and wind shear will be the main focus for the time. Winds will be mainly out of the south and shift southwest towards the end of the TAF period. Low level jet in place will bring 40-50kt winds around 2kft agl out of the south, then southwest as we move closer to 12z. By 15z low level wind shear should be done and winds will be 15-25kts out of the west. Weber && .PREV DISCUSSION... /Issued 335 PM CST Mon Dec 27 2021/ SHORT TERM...Tonight through Tuesday night Southwesterly flow aloft tonight through Tuesday night. Upper trough over the Intermountain West tonight will allow for some perturbations out ahead of the main trough to track north and east out of the southern U.S. Rockies and southwestern states during the late evening and early morning Tuesday hours and across the Panhandles. Considerable high and mid level cloudiness expected tonight across the forecast area and into early Tuesday. Main upper trough holds back to the west near the Four Corners region Tuesday into Tuesday night which will continue to allow for some passing high level cloudiness Tuesday into Tuesday night. Upslope southeasterly surface flow 10 to 20 mph this afternoon will become southerly and then southwesterly tonight. Low level 850 mb nocturnal southerly and southwesterly jet 40 to 50 knots tonight. With upper level support from upper trough to the west and slight increase in low level moisture tonight with dew points rising into the 20s, cannot completely rule out some sprinkles or very light rain later this evening between about 03Z and 09Z Tuesday across mainly the south-central and southeast/far eastern Texas Panhandle. NBM forecasting some 15 to 20 percent POPs tonight across this area and HRRR also showing precip across this same area. TTU WRF also forecasting some light precip mainly over the far southern and southeastern Texas Panhandle. With the dry air in place, virga more likely which may reach the surface where the dew points are higher. This will also allow for some of the stronger winds just off the surface to mix down overnight resulting in some breezy to windy conditions overnight tonight. Will back off on the 15 to 20 percent NBM POPs and go with the 10 POP rule and keeping the POPs just under 15 percent for now. Breezy to windy conditions likely Tuesday as downsloping southwesterly winds continue from the overnight hours tonight into Tuesday. Winds may possibly briefly decouple just before daybreak Tuesday but then quickly increase again after 13Z to 15Z Tuesday. Low level southwest to west nocturnal 850 mb jet develops again Tuesday night after 03Z Wednesday 40 to 50 knots. Dry conditions expected Tuesday and Tuesday night with only occasional high level clouds across the Panhandles. Schneider FIRE WEATHER... Tuesday... Widespread elevated fire weather conditions will be possible on Tuesday across much of the Panhandles. Cannot completely rule out the possibility for some low end critical fire weather conditions, especially across the southwest Texas Panhandle, mainly between about 11 AM to 3 PM CST Tuesday afternoon. Max RFTIs are forecast be 1 to 3 with the highest across the southwest Texas Panhandle and ERC values remaining in the 90th to 96th percentile with some 97th or greater over the Oklahoma Panhandle and possibly the northeast Texas Panhandle. Lowest afternoon relative humidity values will be around 15 to 20 percent and 20 foot westerly winds 15 to 25 mph with higher gusts which could increase to around 20 to 30 mph with higher gusts across the southwest Texas Panhandle. Wed, Thu and Fri will all be near critical with winds being the main contributer to RFTIs of 1-4. RH values are expected to be limiting factor, as they are forecast around 16-25 percent Wed and Thu (little higher Fri). If RH drops a bit more, solid Red Flag conditions will occur rather than elevated to marginal. Schneider/Gittinger LONG TERM...Wednesday through Monday... The period will start with troughing from Central Canada to SW US with strong SW-NE oriented jet from NM to the Great Lakes. Weak lee-side cyclogenesis will occur near NE NM and the OK Panhandle on Wed along a frontal boundary leading to gusty WRLY flow and windy conditions south of the low before it moves ENE as a s/wv crosses the area. There will be sharp temp gradient near the far north along the front and there is pretty significant chance for much cooler temps there if the front sneaks further south which is very possible. SFC low will quickly reform on Thu but more in WRN CO. SFC low will shift a little further south for Friday, but general idea of breezy to windy SW winds, warm and dry conditions will occur both Thu and Fri. Generally ran with 90th percentile or 50th/90th percentile bend for winds during the daytime periods Wed-Fri to achieve breezy to windy forecasts. Another s/wv will drop down the backside of the WRn US trough sharpening up the trough across the four Corners through early Saturday. This will force the coldest airmass of the season towards the region. Positively tilted upper trough and very cold airmass favor faster models for fropa early Saturday and leaned to 25th percentile NBM for highs along with 90th for winds behind the front and if front is fast enough the entire area could experience a daytime high that is below freezing (not just the north. The trough is forecast to swing across the area through the day on Saturday bringing the best chance of precipitation that we have seen in a long while. While the big 3 med range models are currently in good agreement showing precip (mainly snow), the models and especially the ensemble members differ wrt moisture availability and track/evolution of the upper trough. In fact more GEFS members are currently dry than show precip. Because of this the NBM is only showing 20 POPs and will stick with that for now (esp given the ongoing drought). That said, yes, if the stars align, we could get several inches of accumulating snow. The higher confidence part of the forecast is that cold temperatures are on the way and NBM is already indicating lows of 6 to 13 degrees for Sunday. While the cold is significant, the pattern does shift and it doesn`t look like below normal temperatures will be around more than 2 days before warming to near normal on Monday. Gittinger && .PRELIMINARY POINT TEMPS/POPS... Amarillo TX 59 42 61 35 59 / 10 10 0 0 0 Beaver OK 51 39 61 23 57 / 5 0 0 0 0 Boise City OK 49 32 55 25 54 / 5 0 0 0 0 Borger TX 59 44 63 36 62 / 5 5 0 0 0 Boys Ranch TX 61 40 60 34 59 / 10 5 0 0 0 Canyon TX 60 40 61 34 58 / 5 10 0 0 0 Clarendon TX 60 46 65 36 62 / 5 10 0 0 0 Dalhart TX 56 33 57 29 55 / 5 0 0 0 0 Guymon OK 50 38 60 26 58 / 5 0 0 0 0 Hereford TX 61 39 60 33 58 / 5 10 0 0 0 Lipscomb TX 54 43 63 27 62 / 0 5 0 0 0 Pampa TX 56 43 60 34 60 / 5 10 0 0 0 Shamrock TX 59 45 66 34 65 / 5 10 0 0 0 Wellington TX 62 46 68 35 67 / 0 10 0 0 0 && .AMA Watches/Warnings/Advisories... TX...None. OK...None. && $$ 89
Area Forecast Discussion
National Weather Service Detroit/Pontiac MI
650 PM EST Mon Dec 27 2021 .AVIATION... VLIFR flight categories in dense fog remains in place across Southeast Michigan at taf issuance time. Upstream surface observations do show improvement as wind speeds increase with deeper mixing. Went with a persistence forecast the first hour of the period then IFR conditions through mid evening. May still be too optimistic with timing of MVFR but will monitor. A weak ridge of surface high pressure will then build into the state tonight. Forecast soundings support a very dry boundary layer early Tuesday. Did begin to time out start time of IFR snow at 21Z for the Detroit terminals and 23Z at KFNT. .DTW THRESHOLD PROBABILITIES... * High for ceiling at or below 5000 feet this evening. * High for visibility at or below 1/2SM the first hour or two of the period. * High for precipitation type of snow Tuesday afternoon. * Low confidence in visibility restrictions of 1/2SM late Tuesday afternoon. && .PREV DISCUSSION... Issued at 401 PM EST Mon Dec 27 2021 DISCUSSION... Deep moisture remains anchored underneath a sharp inversion with a frontal triple point now in place across eastern Ohio. This will continue to promote widespread stratus heading into the evening, while the passage of an occluded front brings the chance to see drizzle to light showers this evening, favored towards the Thumb. Areas of fog is also likely leading into the early evening for the north Metro region down to the MI/OH border, given the closer proximity to the focal point. Strong deep layer subsidence and very dry air at h850 to h650 have resulted in rapid clearing trends across the Midwest and will build in across the Great Lakes between 00Z-06Z tonight. The extensive stratus deck is expected to erode and push east with the intrusion of drier air, bringing clearing trends and dry weather overnight. Weak caa coupled with these clearing trends will result in overnight lows in the mid 20s for the northern third of the cwa, trending more towards 30 degrees closer to the MI/OH border. An upper-level disturbance over coastal California will traverse across the Plains and Midwest overnight and into Tuesday afternoon, weakening along the way, before arriving over Michigan by Tuesday evening. This will bring the next wintry weather event to SE MI centered Tuesday evening into Wednesday morning. Prior, moist isentropic ascent in the mid-level ahead of this feature will start to bring in expansive mid and upper-level clouds throughout Tuesday morning. Top-down saturation will moisten the low-levels through the afternoon, but with dew point depressions to 30C in place at h850, it will take time for any hydrometeors to reach the surface. Thus, have pushed back the timing of precipitation to 18Z onwards, with a south to north expansion. Plenty of moving pieces to work with in regards to precip type and snow potential... The stronger forcing/isentropic ascent will reside across the southern Metro region after 18Z to ~00Z, along with the better moisture with specific humidity values holding between 3-4 g/kg. While temperatures are forecasted to be above freezing at the onset of precipitation, sufficient wet-bulbing should take place to produce snow. The RAP lowers surface temperatures to or just below freezing, while the warmer HRRR sufficiently lowers wet-bulb zero heights to or below 1 kft. Model soundings do show temperatures turning near isothermal around the -1 to -2C line up to 10 kft with higher DGZ heights, thus not expecting snow ratios to be overly impressive -- at or below 8:1. Working out the intricacies between forcing and lower snow ratios, snowfall ranging between 1-2 inches is a reasonable early estimate along and south of I-94. Locations north... A dry slot is expected to fill in across SE MI between 0-6Z, soon after the better moisture arrives in the low- levels for the northern half of the cwa. It looks plausible at this time to again see the onset of precipitation as snow, but the stripping away of ice nucleation will offer an either an early transition to drizzle/freezing drizzle or could result in a quick end point to winter precipitation. Likewise, the delayed start to precipitation also may hamper precipitation/snow totals given the weaker forcing taking longer to overcome the dry air. Overall will maintain snow totals under an inch at this time. All precipitation chances look to end early Wednesday morning with the dry air filling in. Mid-level southwest flow regime will bring additional chances for wintry weather as another upper-level disturbance clips the region late Wednesday into Thursday. NBM mean QPF holds below .10 inch at this time. A potential bigger system is being eyed for the Saturday- Sunday time frame as ensemble solutions are starting to converge on a low pressure system impacting the Ohio Valley. Still plenty of divergence noted within EPS cyclone centers, so it is way too soon to start talking about any winter weather impacts. WPC Day 4 paints Michigan (and a large portion of the Midwest and Northeast, owing to model divergence) with a 10-30 percent chance of observing .25" liquid equivalent of snow, while CPC clusters still have about half of its 100 ensemble model suite holding .25" liquid equivalent south of the state line. MARINE... Elongated trough of low pressure stretching from northern Minnesota down to Ohio will push east of the Great Lakes by tonight. High pressure will fill in behind it tonight lasting into Tuesday. Winds will start off out of the southeast ahead of the trough, but will flip around to west-northwest behind the trough. There will be a gradient between the two systems tonight which will keep gusty winds around. Northern Lake Huron will see wind gusts around gale force immediately behind the front, and will drop off quickly Tuesday. The next system will lift up into the Ohio Valley Tuesday evening. This will spread a mix of rain and snow across the southern Great Lakes while flipping the winds around to the southeast. Waves will increase along the shore of the Thumb Tuesday night but look to remain below advisory level at this time. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. Lake Huron...Small Craft Advisory until 4 AM EST Tuesday for LHZ421-441. Small Craft Advisory until 7 PM EST this evening for LHZ442. Gale Warning from 10 PM this evening to 7 AM EST Tuesday for LHZ361>363. Lake St Clair...NONE. Michigan waters of Lake Erie...NONE. && $$ AVIATION.....CB DISCUSSION...AM MARINE.......DRK You can obtain your latest National Weather Service forecasts online at
Area Forecast Discussion
National Weather Service Quad Cities IA IL
924 PM CST Mon Dec 27 2021 .UPDATE... Issued at 924 PM CST Mon Dec 27 2021 latest guidance has slowed down with the warm air advection into the area. The RAP started this trend during the afternoon and the 00z guidance kept this as well. This will lead to slightly higher snow accumulations and an increased threat of freezing rain as surface temps look to be slower to warm as well. With this affecting the I80 corridor near the AM commute, decided to pull the adv further south. This is mainly for impacts from any fzra along with sleet or snow. The transition may be quick on the southern end of the adv, however since this is our first real event this season, decided an adv was warranted. && .SYNOPSIS... Issued at 258 PM CST Mon Dec 27 2021 The latest water vapor loop was indicating tomorrow`s storm system was currently acrs the west central coast of CA. This wave will quickly embed in progressive west-southwesterlies and produce a warm air advection mixed precip event for the local area Tuesday. This active flow will then possibly produce another light precip event Wed evening acrs portions of the area, then eyes turn to a larger storm system potential for the weekend. && .SHORT TERM...(This Evening through Tuesday) ISSUED AT 258 PM CST Mon Dec 27 2021 The approaching sfc low acrs western KS by 12z, with increasing leeside warm air advection again on nose of southerly 35-45+ KT LLJ action. Fcst soundings show a lot of dry air layers to over come, but a PWAT feed of 0.50 to 0.70 of an inch and the robust flow should overcome this to fuel a moderate precip event acrs portions of the area. Fcst soundings and thermal profiles suggest a wintry mix creeping up acrs the southern CWA just before 12z. Saturation and evapo-cooling profiles then suggest mainly snow spreading northward Tue morning, and northwest saturation jump for precip breaking out 12-14z acrs eastern IA north of I80. Drier east- southeast lower level flow may delay snow developing further east into northwest IL until after 15z Tue morning. The snow to continue north of I80 into early afternoon, while ongoing strong WAA changes the southern flank of precip to mainly rain. Of course, there will be a transition band of freezing rain and sleet migrating northward 1-2 hours acrs any one spot. This would produce a ice glaze of 0.10+ or so mainly on elevated sfcs with marginal pavement temps, and maybe some light sleet accums. Then the rain takes over from south- to-north. Overall, will advertise 1-2 inches of snow north of I80, with strips of 0.10" or less of ice glaze acumms. The Hwy 20 corridor may have some areas of 2-3 inches of snow. Total precip amounts of rain/sleet/snow/freezing rain should range from 0.25 to half inch liquid equivalent by 00z Wed, taking into account the extent of forcing, system speed and saturation. With minimal winter events this season so far, will issue a winter wx advisory for wintry mix generally north of I80 or along and north of Hwy 30. Will use two sectors, the west including CID and DBQ starting earlier at 12z, and Clinton into NW IL starting at 15z Tue morning. Both sectors go to 00z with the idea of canceling from south-to-north as precip transitions and stays mainly rain. A very uncertain and challenging fcst still at this point, and all the above takes into account a progressive and robust warm air advection(WAA) winning out scenario. Some concern that if the WAA stalls or slows for 1-3 hours, there could be higher icing amounts of 0.10 to over 0.20". And for snow, could be areas doubling what we are advertising, such as one scenario that the 12z ECMWF is showing producing 3-5+ inches of snow northeast of a line from Cedar Rapids, to Sterling IL. This and icing/sleet swaths further south may warrant an expansion of the headline further south of the I80 corridor to at least Fairfield IA over to Monmouth IL. The night shift will have to assess the developing system and make the changes if needed. .LONG TERM...(Tuesday Night through next Monday) ISSUED AT 258 PM CST Mon Dec 27 2021 Key messages: 1) Mixed pcpn ending Tuesday evening. 2) Light snow Wednesday afternoon/evening. 3) Possible snowstorm New Years Day. Details: Tuesday evening: I will walk out the mixed pcpn in our far ne cwa as the strong WAA/forcing pushes off to our north and east. Northwest winds will usher colder air into the area with lows bottoming out in the teens nw to the mid 20s se. Wednesday afternoon/evening: Weak wave quickly moves west to east across the cwa. This should produce some light snow in the cold air with accumulation less than an inch. Chilly with highs in the mid 20s nw to the mid 30s se. Thursday through Friday: Deep trough in the southern Rockies re- loads as an arctic front slides southeast across the upper Midwest. With a southwest flow aloft temperatures moderate ahead of the advancing arctic front. Highs on Friday should push into the 30s north and 40s south. New Years Day: Potential snow storm for all or portions of the dvn cwa but low confidence in the track of the system. The 12z/27 ECMWF has shifted the track of the surface low much farther nw compared to the previous run, taking the low from the southern Plains to the Ohio Valley. This would bring the potential for a plowable snow event to much of the area. On the other hand, the GFS takes the low from Colorado to Chicago, keeping the heavy snow northern IA/southern MN/central WI. Some accumulation would be possible in our nw cwa. Still low confidence in the track but hopefully there will be consensus among the models during the next couple of days to bring our confidence level much higher. One thing is for certain, even colder air to follow in the wake of this system with below zero readings possible early Sunday. Of course, any snow cover would allow temperatures to be colder. Haase && .AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening) ISSUED AT 613 PM CST Mon Dec 27 2021 VFR conditions expected for the next 10 to 12 hours before MVFR and then IFR conditions move in with a wintry mix affecting all TAF sites. A snow to sleet to fzra to ra transition is expected after daybreak and will move north through the period. Rain is expected at all sites late in the period. && .DVN WATCHES/WARNINGS/ADVISORIES... IA...Winter Weather Advisory from 9 AM to 6 PM CST Tuesday for Clinton-Jackson. Winter Weather Advisory from 6 AM to 6 PM CST Tuesday for Benton- Buchanan-Cedar-Delaware-Dubuque-Iowa-Johnson-Jones-Linn- Louisa-Muscatine-Scott-Washington. IL...Winter Weather Advisory from 9 AM to 6 PM CST Tuesday for Carroll-Jo Daviess-Stephenson-Whiteside. Winter Weather Advisory from 6 AM to 6 PM CST Tuesday for Bureau- Henry IL-Mercer-Putnam-Rock Island. MO...NONE. && $$ UPDATE...Gibbs SYNOPSIS...12 SHORT TERM...12 LONG TERM...Haase AVIATION...Gibbs
Area Forecast Discussion
National Weather Service Wilmington NC
710 PM EST Mon Dec 27 2021 .SYNOPSIS... High pressure offshore will bring near record warmth for the next several days. Rain chances will accompany a weak cold front Thursday. Warm weather continues heading into the weekend. A stronger cold front is expected Sunday into Monday. && .UPDATE... No major updates planned with the evening forecast issuance. Other than some developing stratocumulus overnight into Tuesday morning, and batches of cirrus passing in the westerly flow aloft, winds should remain up enough to prevent any significant fog formation. The winds will also aid in atypically warm minimum temperatures tonight. Lows this time of year are normally in the mid 30s, yet the forecast is for lows in the mid to upper 50s most locations (normal high temperatures are mid 50s for late December)! && .NEAR TERM /THROUGH TUESDAY NIGHT/... High pressure will ridge back into the area for the balance of the period resulting in generally fair weather though patchy fog is possible, especially Tuesday night. Mins tonight and Tuesday night will fall to the mid to upper 50s. Highs Tuesday will reach the mid to upper 70s. && .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/... High pressure both at the surface and aloft will be centered east of the Bahamas through the period. And while there will be a small increase in moisture it will all be confined to the lowest levels thus any model showing QPF looks highly suspect. Temperatures will once again approach record levels but the slight increase in cloud cover should keep highs a few degrees shy. Wednesday night`s lows in the low 60s impressively a few degrees above climatological highs. && .LONG TERM /THURSDAY THROUGH MONDAY/... Much more pronounced moisture advection slated for Thursday ahead of a cold front. The resulting cloud cover will try to cap the unseasonable warmth by a few degrees but according to most guidance not have much luck. A few showers appear likely later Thursday into Thursday night but low amplitude aloft will preclude any more substantial drought-relieving rain amounts. Friday looks to be rain- free but rain should spread north across the area with a warm front Friday night. Minor rain chances may linger on Saturday should the frontal moisture have difficulty progressing northward. A fairly dynamic system will be approaching Sunday into Monday, some timing differences noted between various guidance. Once the timing uncertainty diminishes with time we may be able to introduce thunder into the forecast as dynamics appear sufficient should even meager instability develop. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... MET/MAV guidance diverge significantly with the prospects of IFR/MVFR conditions developing during the overnight at a few of the area terminals. However, HRRR and other tools/guidance suggest that the more optimistic MAV is the plausible solution with VFR conditions prevailing. Enough of a pressure gradient should prevent any significant fog formation, while the exception may be some TEMPO MVFR at KCRE in particular toward daybreak. Otherwise, could see BKN stratocumulus deck develop and impact KFLO/KCRE/KMYR generally after 08Z but with cloud bases mostly above 3kft. After 14Z SWly winds will increase and with heating cloud bases will increase during the day. Extended Outlook... Low ceilings and scattered convective showers Thursday and into Sunday could cause flight category restrictions. && .MARINE... Through Tuesday night, Expect W to SW winds at 15 to 20 KT for much of the period though there could be lulls at times, mainly late at night and early in the morning due to reduced thermal contrast between land and sea. Seas will generally run 2 to 4 FT. Wednesday through Saturday... A slight westward shift of the offshore high Wednesday will bring winds into the 15-20kt range across most of the area. Wind and seas both approaching but generally staying blow advisory thresholds. Whether or not flags will be needed by Thursday may hinge upon the frequency of the gusts to 25kt, which is a bit difficult to determine this far out. Decreasing and veering slated for Friday is association with a weak cold front that lifts back to the north on Saturday. The warm sector of the next system later in the weekend may yield advisory-worthy winds and seas. && .ILM WATCHES/WARNINGS/ADVISORIES... SC...None. NC...None. MARINE...None. && $$ SYNOPSIS...ILM UPDATE...29 NEAR TERM...31 SHORT TERM...MBB LONG TERM...MBB AVIATION...29 MARINE...ILM
Area Forecast Discussion
National Weather Service Jackson MS
959 PM CST Mon Dec 27 2021 .UPDATE... Updated for evening discussion. && .DISCUSSION... No major changes to the forecast tonight. Sfc southerly flow will allow moisture to trickle in and cause a sprinkle or some light precip overnight into the early morning. By morning, rain chances will increase as a warm frontal boundary is stalled to our north. Overnight lows will remain in the lower to mid 60s. /AJ/ Prior discussion below: Tonight and Tuesday: Warm conditions continued today as plenty of sunshine and gusty southerly winds contributed to temperatures reaching the upper 70s and lower 80s across the region. To our north, a frontal boundary is stalled but will remain to our north as several surface lows track along or near it from the Central Plains to the Ohio Valley. The upper ridge that has been entrenched over the region will finally push east and we will be under southwest flow aloft. Our region will continue to be in the warm sector as gusty southerly winds will bring continued warm, moist air into the region through tomorrow. Hi- res guidance indicates more potential for some warm advection showers beginning later tonight and continue through teh day tomorrow. There is some potential for some storms to develop across the southern sections of the forecast area tomorrow but no severe weather is expected. Overnight lows will continue to be on the warm side with readings in the 60s, with mid to upper 60s in the west. Highs tomorrow will again be similar to today with readings in the 70s and lower 80s. /28/ Tuesday night through Sunday: Warmer than normal temperatures and moisture will continue areawide into Wednesday ahead of a second cold front that will be approaching our CWA from the northwest. Our PWATs are expected to pool above and inch and a half with low to mid 60F surface dew points. Although deep layer shear looks to increase to 50kts Wednesday morning, MLCAPE is expected to remain less than 400J/kg prior to 18Z and little to no deep convection is expected in our CWA prior to 18Z per the latest 18Z HRRR run. As the day progresses and convection shows an uptick isolated severe storms capable of damaging wind gusts will be possible especially across the northwest half of our CWA where the best instability and shear are progged to reside into the evening. The cold front will be nearly parallel to the flow aloft leaving it to drift into the northwest portions of our CWA toward sunrise Thursday. With the winds aloft remaining southwesterly, the cold front is expected to stall across our southern zones Thursday afternoon. The stalled front will remain the focus for precipitation development along and south of it into Friday when it moves back north of the CWA as a warm front. By Saturday morning our whole CWA will be back in the warm sector with PWATs back above an inch and a half along with mid to upper 60F dew points. An upper level trough digging southeast of the Four Corners region and over the southern Plains will help generate a surface low to the west of our CWA. There are significant differences in the models with whether or not a closed low develops and the position and track of the surface low but widespread rain chances are expected to develop across our CWA Saturday into Saturday night. Considering the expected environmental parameters, severe storm develop will be possible mainly Saturday night into Sunday morning across our whole CWA. There will also be some heavy rainfall with this system but flooding issues are not a concern due to the dry antecedent conditions. A return to cooler and drier conditions are still expected Sunday in the wake of the cold front. /22/&& && .AVIATION... 00Z TAF discussion: Blending much of the previous forecast with persistence and the SREF as far as timing of the MVFR stratus that will develop later tonight and through the morning. VCSH possible in far NW and SE...with conditions slowly improving by midday tomorrow. && .PRELIMINARY POINT TEMPS/POPS... Jackson 62 79 65 79 / 7 50 58 85 Meridian 61 78 65 78 / 6 52 81 79 Vicksburg 64 81 66 80 / 12 35 42 87 Hattiesburg 61 80 65 80 / 12 57 82 74 Natchez 64 81 66 80 / 15 39 49 81 Greenville 65 77 64 76 / 11 29 34 93 Greenwood 65 78 66 77 / 10 40 45 94 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...None. LA...None. AR...None. && $$ AJ
Area Forecast Discussion
National Weather Service Paducah KY
800 PM CST Mon Dec 27 2021 .MESOSCALE DISCUSSION... Issued at 800 PM CST Mon Dec 27 2021 Just completed a early evening update to reflect smaller scale convective trends and larger scale isentropic lift on rainfall evolution across the WFO PAH forecast area. The HRRR guidance appeared to be a good proxy for the amplification of storm scale updrafts over extreme southeast Illinois and west Kentucky late this afternoon, with a couple of cells even generating a few lightning strikes. Any notable HRRR updraft helicities disappear this evening, but do pick up around midnight from a Cairo IL...Paducah and Sacramento KY line, lasting only still around 3 am CST. The most CAPE available from the HRRR is less than 250 J2/kg2, however this may be enough to support local lift and instability for slightly higher rainfall rates. Overall, the rest of tonight will be more associated with isentropic lift (maximized around the 300k isentrope plus or minus 5k). The main rainfall zones will be in two areas. The first area will be centered along and north of a Perryville MO to Owensboro KY line, gradually moving northward between 3 am and 8 am Tuesday to the I-64 corridor in southern IL and southwest Indiana. The second area will move rapidly from the AR/MO and KY/TN state line around 2-3 am CST Tuesday and expand rapidly north covering most of the rest of the WFO PAH forecast area by 8 am CST Tuesday. The best rains will likely be focused along the Crawley`s ridge/Shawnee Hills area northward between 8 am and noon on Tuesday, generating better rainfall amounts. Would not be surprised to see a transition from overrunning to more upright convection and a few thunderstorms in southwest Illinois between 9 am and noon. This area will be more focused with the return of the stalled out frontal zone this evening northward as a warm front. Overall, will see a roller coaster of temperatures and dewpoint back northward along the southern 1/3rd of the WFO PAH forecast area this evening, bracketed by adiabatic and advective thermodynamics along the frontal zone. && .SHORT TERM...(Tonight through Wednesday night) Issued at 230 PM CST Mon Dec 27 2021 The primary near term forecast challenge is with the mid week rain event/forecast qpf. After the cold fropa today, surface dew points will drop into the more seasonal 30s-40s over most of the area tonight, before they climb again with the pivoted boundary that will make its return as a warm front. Dew points will punch back up thru the 50s tmrw, and deeper swlys will likewise moisten the column atop. Looking at the ensemble situational tables for both the ECMWF and the NAEFS, specific humidity, precipitable water, and integrated vertical water vapor transport all top out the chart, with upwards to 10 year return intervals on the climo. This moist tongue will be tapped by basically two waves of energy, one coming Tuesday, the other Wednesday, and should produce an average storm total qpf over that time of just shy of an inch. We`re in the marginal risk for qpf exceeding FFG according to WPC, and that`s accepted because thunder chances both time periods may enhance rain totals and contributed to a localized flooding hazard. Because of the location of that boundary and a little better rain chances north, we`ll see a pretty large temp range across the CWA. Highs will be in the 50s north, and near 70 south. Similarly, lows will be in the upper 30s north, and near 50 south. The only other component not yet discussed is wind. There could be some gustiness in the returning warm sector tmrw, with gusts in the south (far SEMO into western KY) pushing 25-30 mph in the afternoon. .LONG TERM...(Thursday through Monday) Issued at 230 PM CST Mon Dec 27 2021 A storm system is poised to move through our region Friday night into Saturday night. There are significant model differences concerning the strength and track of the surface system. These differences will factor into precip amounts and thunder potential. There is general model agreement that a 500 mb shortwave will move from the northern Plains to the Great Lakes this weekend, while a second stronger shortwave tracks across the southern Plains to the lower Mississippi Valley. Split flow patterns such as these often result in significant model differences. In this case, the 12z gfs and its ensemble mean are stronger and further north with the surface low than the ecmwf guidance. The operational 12z gfs takes a sub-1000 mb surface low from the Plains to the Great Lakes, resulting in a narrow corridor of marginal instability ahead of the cold front as it moves through our region Saturday. Given very strong shear, this would be sufficient for isolated but potentially intense convection. However, the ecmwf ensemble mean and 12z operational run depicts a weak surface wave moving east along a stalled east-west frontal boundary over or just north of our region. The ecmwf solution indicates little or no surface-based instability, but it indicates a favorable environment for widespread rainfall and training elevated storms with heavy rainfall totals. Although the operational gfs appears to be a bit of an outlier, it is still a viable solution. The potential for organized convection cannot be ruled out, depending on whether the gfs remains consistent. Heavy rainfall potential is moderate to high. Once the surface cold front passes through, the persistent warm December temps will end. Temps will fall below freezing Sat night and hover in the 30s on Sunday. Drier air will move in behind the cold front, however there is a chance precip will linger into Sunday. A surface low may develop in the vicinity of the southern Appalachians Sunday, throwing moisture back northwest. If this occurs, a mixture of snow and rain could occur Sunday. A coating of slushy snow cannot be ruled out, but sub-freezing wind chills are a certainty. This will be in sharp contrast to the 70 degree temps of late. Monday of next week looks sunny but cold as the storm system moves away. Highs will be around 40. && .AVIATION... Issued at 528 PM CST Mon Dec 27 2021 Just prior to the 00z Tuesday WFO PAH TAF issuance, convection associated with the passage of the cold front moved through the KPAH TAF site and developed just south of the KOWB TAF location. Through the first six to nine hours of the the 00z Tuesday TAF forecast period VFR conditions with mainly middle and upper level cloud bases and ceilings will exist for the TAF sites along and north of the KCGI-KEVV line. KPAH and KOWB may see lower VFR ceilings in the 4-6kft agl range through the evening. Winds for these aformentioned TAF locations will veer from north to east with time. Overrunning rainfall will move north of the stalling front and work back into all of the TAF locations in the 06z-09z Tuesday time frame with a reduction in ceilings to VFR. In the 11z-15z Tuesday time frame, a more rapid reduction from VFR to MVFR and IFR ceilings will occur as the previous cold front begins to work back north as a warm front. KPAH will be the only location to return back from MVFR to VFR late in the forecast period (Tuesday afternoon) as the front will be north of that site. The TAF sites along and north of a KCGI to KOWB line will hold in the upper IFR and very low MVFR ceiling categories from roughly 15z to 17z Tuesday onward as the warm front slows it northward progress through these TAF locations. MVFR visibilities will be most likely over the KMVN TAF locations Tuesday afternoon. There was some consideration in leaving a mention of Low Level Wind Shear (LLWS) during the transition time of the front into the TAF sites around 15z Tuesday, given the sharp directional and speed shear, but given the uncertainty in timing and location, decided to omit for now. However, it may be something to monitor for IFR rated carriers planning takeoffs between 14z-17z Tuesday. && .PAH WATCHES/WARNINGS/ADVISORIES... IL...None. MO...None. IN...None. KY...None. && $$ MESOSCALE...Smith AVIATION...Smith
Area Forecast Discussion...CORRECTED
National Weather Service Phoenix AZ
544 PM MST Mon Dec 27 2021 .UPDATE... Updated Aviation discussion. && .SYNOPSIS... An unsettled winter weather pattern will continue through the week as a series of fast moving weather systems pass through the region. Precipitation chances will occur on multiple days with the best chances on Tuesday and Friday. The highest precipitation amounts will be focused over the higher terrain of central Arizona. Temperatures will remain below average through the entire week. && .DISCUSSION... GOES WV imagery and RAP H5 analysis shows a very moist jet streak and SW flow aloft ahead of an upper level trough and PVA anomalies dropping through coastal CA. Additional PVA anomalies were moving through AZ ahead of the trough axis. IR METSAT imagery depicts widespread cloudy conditions with a large high and upper- middle cloud shield with and ahead of the low pressure system. Radar has been showing a large area of mostly just virga signatures south of Phoenix. The moisture profile in the latest Phx ACARs soundings showed elevated moisture lingering in the lower BL up through ~850 mb with an inversion cap of dry air above that up to the moist upper-middle cloud base barely above H5, with PW near 0.55" Still under the heavy influence of a long-lived unsettled weather pattern, models and ensembles agree on the next 2-3 shortwave disturbances passing through our area from this evening through Wed morning or possibly even Wed evening. The first of these passes through SE CA this evening and tonight and will bring breezy to locally windy conditions across parts of SE CA from this afternoon through tonight. As a result a wind advisory remains in effect for gusty winds with gusts up to 45 mph including JTNP and W Imperial Cty and I-8. Another fast wave(s) tomorrow into Tue night/Wed. will dramatically increase the chance of precipitation on Tuesday to 70-80%, mainly for Phoenix and the surrounding deserts and e-ward to the high country. The Grand Ensembles and the NBM are in excellent agreement on a high POP, modest QPF scenario for Phoenix on Tue- early Wed with total rainfall for Phoenix near ~0.1-0.25". However orographic upslope conditions will enhance the QPF totals across the high country NE-E of Phx as a modest and fleeting IVT plume accompanies the system. Models depict a nicely elevated moisture levels from just under 850 mb to just above H7. As a result high country QPF could range from 0.25-1.00" and locally higher in moderate rain showers. For Phoenix and the lower deserts the HREF family and the HRRR depict scattered light rain showers for Tue-Tue evening. The NBM and HRRR and other models have also been consistently increasing the amount forecast snow amounts for elevations above ~4.5-5 Kft. Although an overly dry layer from -10 to -13 degrees C and higher may inhibit dendritic production. However the NBM prob of snowfall accumulations >4" approaches 40% ending 12Z Wed for the Hwy 60/Hilltop area of S Gila Cty. Therefore the benefit of the doubt has been granted to the models and a winter weather advisory has been hoisted for Tue morning through Wed morning for high country/S Gila Cty elevations above 4,500` for snow accumulations up to 7". As a result hazardous winter driving conditions in the higher elevation passes are expected. By Thursday an elongated low pressure trough digging through offshore CA maintains strong SW flow and a jet streak across the region. Then for Friday at least two clusters and >50% of the members are very bullish on ejecting at least the first of a possible pair of pronounced troughs through the region on Fri and into the weekend. These two clusters also depict widespread and locally heavy precip across the entire CWA, especially for Phoenix and eastward. Various IVT ensemble forecasts for the late week period favor the main moisture plume surge to be centered further SE of the CWA with only the N fringes of the plume over the CWA. However the NBM and Grand Ensemble QPF are in very good agreement on Phx QPFs for the New Year`s Eve Friday at an elevated range of 0.5-1.25" and typically even much higher amounts near 1-2" across the high elevation burn scar country. Models are also showing some early confidence in sharply colder temps by Sun morning with lows across the lower deserts in the mid 30s in Phx and the upper 20s in across the open deserts. && .AVIATION...Updated 0040Z. South-Central Arizona including KPHX, KIWA, KSDL, and KDVT: A series of passing weather disturbances and subtle cold fronts over the next 24-36 hours will lead to periods of ceilings below 6kft AGL. A subset of that time will also see light showers - mainly Tuesday afternoon which is also when MVFR conditions are most likely. Before then, there may some spotty light showers between 09Z-17Z. Surface winds should favor southwest directions this evening but it would not be surprising to see southeast or variable conditions. Above the surface, deep moderate to strong southwesterly flow will continue. Southeast California/Southwest Arizona including KIPL and KBLH: A series of passing weather disturbances and subtle cold fronts over the next 24-36 hours will lead to windy conditions this evening and again Tuesday afternoon (favoring southwesterly directions) with lighter southwesterly winds in between. Above the surface, strong southwest and west winds will continue. In addition to the winds, there will be an increase in the lower tropospheric humidity such that scattered cumulus can be anticipated during the day Tuesday (if not sooner) and possibly some ceilings of BKN050 Tuesday afternoon (more likely at KIPL than KBLH). Shower activity is not expected. && .FIRE WEATHER... Wednesday through Sunday: Temperatures will continue in a below normal range through the week as a moist environment results in periodic chances for precipitation. Some eastern districts could see another round of heavier accumulation late in the week. Snow levels in eastern districts may fall as low as 4500ft during the middle of the week before increasing late in the week. Minimum afternoon humidity levels will struggle to reach 40% although some drying may arrive over the weekend. Overnight recovery should be excellent in a 60- 100%. Wind speeds appear fairly typical for the season with potentially some enhancement of northerly winds behind a front over the weekend. && .PSR WATCHES/WARNINGS/ADVISORIES... AZ...Winter Weather Advisory from 3 AM Tuesday to 5 AM MST Wednesday for AZZ557-558-563. CA...Wind Advisory until 3 AM PST Tuesday for CAZ560-562-566. && $$ DISCUSSION...Sawtelle AVIATION...AJ FIRE WEATHER...18
Area Forecast Discussion
National Weather Service Pueblo CO
828 PM MST Mon Dec 27 2021 .UPDATE... Issued at 820 PM MST Mon Dec 27 2021 CDOT cameras showing a faster accumulating snowfall for the South Fork area, as well as model guidance suggesting a higher concentration of areas that could receive measurable snowfall over the eastern San Juan Mountains below 10000 feet, has prompted the issuance of a Winter Weather Advisory additionally for Zone 67, which includes these areas. -Stewey && .SHORT TERM...(This evening through Tuesday) Issued at 302 PM MST Mon Dec 27 2021 Key messages: 1) Snow and strong winds continue along the Continental Divide tonight into Tuesday. 2) Winds increase again tonight over the southern Sangre De Cristos but should stay below high wind criteria. Currently, occasional light snow observed along the Continental Divide this afternoon, while strong w-sw winds continued to produce blowing and drifting snow, especially near/above timberline. Generally dry/breezy and cool elsewhere, though RH has held up enough to keep fire danger mostly in check, with only some brief critical conditions possible until sunset across Las Animas County from Trinidad eastward. Tonight, next upper wave approaches wrn Colorado this evening, then moves briskly across the state by early Tue morning. Increase in upper forcing and continued favorable w-sw mid level flow should keep Continental Divide snow machine going, with several more inches of accumulation over higher west facing slopes, especially around Wolf Creek Pass. Strong winds will persist as well, with blowing/drifting over Monarch/Wolf Creek/Cumbres Passes through the night. Some spillover showers will reach the Sangres and perhaps Pikes Peak overnight, with some light accums over the higher peaks, especially across the srn Sangres. Still some hints in model cross sections and HRRR surface wind gust fields of strong overnight winds in the lee of the srn Sangres, though window looks too small for a highlight, and will keep gusts in the 60-70 mph range, just short of criteria. On Tuesday, lull in snowfall during the morning as wave moves away from the state, though orographic flow will keep snow showers going over the higher west facing slopes of the ern San Juans and Sawatch Range for much of the day. Will let lower elevation/Leadville area advisories expire on schedule Tue morning, and hold onto warnings/advisories for higher elevations through the day. Suspect snowfall will begin to increase in intensity late afternoon over the ern San Juans, as mid level flow becomes more swly in response to next wave moving through the Great Basin. Breezy/dry/cool conditions elsewhere on Tue, with surface front lurking near the Palmer Divide during the afternoon. Expect most of the I-25 corridor/ern plains to stay south of the boundary through the day, though colder air could get into nern El Paso County and Kiowa County late, and thus nudged max temps downward just a couple degf in these areas. .LONG TERM...(Tuesday night through Monday) Issued at 302 PM MST Mon Dec 27 2021 Key Messages: 1) Snow continues along the Continental Divide sporadically through Saturday morning 2) Much colder over the weekend, with the coldest temperatures expected Saturday through Sunday morning Tuesday night and Wednesday...Upper shortwave will be crossing the area, with the trough axis crossing the forecast area right around 12z Wed. Therefore, significant snowfall is expected across the higher terrain Tue night through early Wed morning with another 10 inches for the sw mts and 2 to 4 inches for the remaining peaks. Once the trough axis crosses at 12z and the wind flow switches to a northwest direction, a rapid decrease in snowfall is expected and ongoing highlights may currently be in place about 6 hrs too long. However, will make no changes to the highlights as of yet since this upper system may slow a bit and change everything. Plan on high temps Wed in the 30s for the high valleys, and mid 30s to mid 40s for the plains. Wednesday night and Thursday...An upper closed low breaks off from the main flow aloft and pushes just off the CA coast Wed. While the upper flow across western CO will be more west to northwest, lighter snow will continue along the Continental Divide through this 36 hour period and could add up to as much as 10 inches of fresh snow for the sw mts, and around 5 inches for the central mts. However, the Sangres are forecast to remain dry and this will still be the "lull" before a more significant snowfall event this weekend. As for high temps Thu, readings across the high valleys will remain in the 30s, while the plains will warm by 10 degrees, into the mid 40s to mid 50s. Friday and Saturday...The main upper trough of low pressure begins to finally move southeast out of the Pacific NW, while the closed low off the CA coast weakens and start to move north. Latest model runs indicate that these two features will merge over the desert SW late Fri, and cross the Four Corners as a closed low on Sat. Latest runs also show this system to be stronger and further south, successfully pulling in much colder air for the area by Sat but a questionable amount of pcpn for the eastern plains. As for the higher terrain, potential new snow amounts range from 18 to 20 inches for the sw mts, 10 to 12 inches for the central mts, and around 3 inches for the peaks of the eastern mts. Look for high temps Fri in the 30s for the high valleys and upper 40s to upper 50s for the plains, then 20s for most areas on Sat. Saturday night through Monday...Dry and cooler as weaker westerly flow aloft settles in, and the temperature roller coaster continues. It will be exceptionally cool Sat night into Sun morning as the mercury is forecast to drop to lows of 5 above to 15 below for the entire area. Temperatures are expected to rebound, with the high valleys remaining cool in the 20s to mid 30s for Sun, then 30s to around 40F for Mon. The plains will warm to around 40F for Sun, then mid 40s to lower 50s for Mon. Moore && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 302 PM MST Mon Dec 27 2021 VFR at all taf sites the next 24 hrs, with a low risk of a vcsh and some lower VFR cigs at KALS from 07z until 15z Tue morning as a few snow showers spill over the eastern San Juans. SW winds at KALS will gust 20-30 kts into early evening before diminishing. At KCOS and KPUB, s-se winds persist into the evening, then turn more w-sw overnight. Gusty w-sw winds return to all sites after 18z-19z Tue. && .PUB WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 5 PM MST Wednesday for COZ066. Winter Storm Warning until 5 PM MST Wednesday for COZ060-068. Winter Weather Advisory until 8 AM MST Tuesday for COZ058-059- 061-067. && $$ UPDATE...STEWARD SHORT TERM...PETERSEN LONG TERM...MOORE AVIATION...PETERSEN
Area Forecast Discussion
National Weather Service San Diego CA
200 PM PST Mon Dec 27 2021 .SYNOPSIS... A low pressure system from the northwest will bring precipitation again, including snow in the mountains, along with strong gusty west winds this afternoon and evening. Additional precipitation is possible at times from Wednesday through Friday from a closed upper level low pressure system off the coast of southern California. Heavy snow will be possible in the mountains from this storm. Well below average high temperatures will warm slightly late this week. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Mostly cloudy skies prevail as precipitation was starting to move into the area, especially northern Orange County and the western part of the Inland Empire. The track of the next wave is a little slower than what the models were showing Sunday, so most of the precipitation should begin in most areas late this afternoon. The HRRR and local WRF are showing hourly maximum hourly precip rates below 1/2" per hour, so debris flow concerns in the burn scars are minimal for today/tonight. Precipitation amounts should stay moderate as the models/ensembles have trended downward a bit, including a bit of a downward trend to the snow in the mountains. HREFv3 has the probability of greater than 6" of snow in 6 hours down to 70-80 percent versus 90 percent in yesterday`s runs in the San Bernardino/Riverside County mountains. Overall, 4-8" of snow looks good for the mountains above about 5000 feet, with the possibility remaining of over 1" of snow per hour in the heaviest time period late this afternoon/early this evening. Strong winds will prevail in the mountains/deserts due to the strong height gradients aloft and associated 50-55 knot winds at 700 MB. High- resolution models show gust potential of over 70 MPH locally on the upper desert mountain slopes late this afternoon and this evening. Due to the slower track of the system, the San Diego County part of the winter storm warning was extended to 3 AM Tuesday, but areas farther north will still expire at midnight tonight. The big picture continues to be the winter broad deep long-wave trough over the western US through Fri/Sat followed by some weak ridging over the weekend as the trough shifts east. Tue should have a few showers, mostly light, due to the next wave, but the key point will be the unusually cold high temperatures, with the chance that all locations west of the mountains and perhaps even in the lower deserts remaining below 60, with some locations in the far inland valleys maybe not even reaching 50! Due to cloud cover and ground moisture, we at least avoid a freeze at lower elevations the next few nights. The storm system Wed-Fri from the north will be slower moving, partly due to the upper low closing off to our west. This will be accompanied by deep moisture, with saturation at times possibly approaching/reaching 500 MB. Timing of the precipitation is still uncertain, but there is the potential of an inch or more of rainfall Wed-Fri near the coast (best chances Wed-Thu). Orographics might not be as good as with previous systems in the mountains, but ENS is showing a lot of members with heavy snowfall in the San Bernardino Mountains, specifically 13" on average among the members 18Z Wed-18Z Thu in the grid box containing Big Bear, and since that includes some lower elevations, that is a bit conservative. A few locations above about 7500 feet could get 2-3 feet of snow Wed-Fri. The atmosphere does warm some, with 700 MB temps rising to around -5 C by Thu, so snow levels should be a little higher, but not high enough to preclude snow above about 5500-6000 feet. The closed low should go inland around Fri, but the track will determine what happens with our precipitation then, with a more southerly track in northern Baja meaning less here but a more northerly track across SoCal could prolong signification precipitation. Next week has a lot of uncertainty with GEFS solutions generally showing more troughing off the coast which would result in more precipitation over the West Coast, including SoCal, and ENS solutions showing more of less zonal flow and mostly drier weather. Cluster analysis shows about 50/50 odds for either solution. && .AVIATION... 272100Z...SCT-BKN030-050 through 23Z with isolated -SHRA. Clouds thickening and lowering to BKN-OVC020-030 between 23Z-09Z with more widespread showers moving in from the northwest. CIGS down to 015 and vis lowering to 2-5 miles in the heaviest showers tonight. Mountain slopes becoming obscured in clouds/fog/pcpn tonight. W-NW winds 25-35 kt in the mtns and desert slopes with gusts to 60 kt and moderate to strong up/downdrafts and LLWS. Showers ending most areas tonight except isolated showers Tuesday in the mountains and in San Diego County. Mountain occasionally obscured in clouds and fog Tuesday. && .MARINE... A Gale Warning is in effect through 4 PM Tuesday. West winds increasing to 20-30 kt with gusts to 35 kt this afternoon and continuing tonight and Tuesday. The strongest near-gale force winds will occur tonight, decreasing a bit on Tuesday but remaining at Small Craft Advisory levels through mid-afternoon. Scattered showers through Tuesday, most widespread tonight. && .HYDROLOGY... Precipitation will increase from northwest to southeast late this afternoon, with a little bit of a delay in timing compared with previous forecasts. Precipitation should peak this evening then decrease from the northwest overnight. Rainfall is expected to range from 0.2 to 0.3 inch near the coast, to 1 to 1.5 inch in the mountains with one-tenth inch or less in the deserts. Snow levels will rise to 4500 to 5000 feet in the afternoon, then fall to 3500 to 4000 feet late tonight. This system will be moving fairly quickly but could locally produce brief rainfall rates of 0.25 to 0.45 inch per hour. An upper level low pressure system off the coast of southern California will likely bring additional precipitation Wednesday through Friday. Confidence remains lower with timing and amounts given uncertainties in the track of this upper low, but amounts could be substantial, with more than an inch near the coast likely. The greatest potential of greater precipitation amounts would be for Wednesday into Thursday. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Winter Storm Warning until midnight PST tonight for Riverside County Mountains-San Bernardino County Mountains. Winter Storm Warning until 3 AM PST Tuesday for San Diego County Mountains. High Wind Warning until 3 AM PST Tuesday for Apple and Lucerne Valleys-Coachella Valley-San Diego County Deserts-San Gorgonio Pass Near Banning. PZ...Gale Warning until 4 PM PST Tuesday for Coastal Waters from San Mateo Point to the Mexican Border and out to 30 nm-Waters from San Mateo point to the Mexican Border Extending 30 to 60 nm out including San Clemente Island. && $$ PUBLIC/HYDROLOGY...Maxwell AVIATION/MARINE...Moede