Weather Blog: Topsy-turvy weather pattern finally fades...milder weather for Christmas!?

Our latest RPM futurecast model shows a pretty nice day on Tuesday after a cold start! With the wind shifting more out of the south thanks to a high-pressure moving towards our east, temperatures will rise to around 50 degrees with a good amount of sunshine. (WCHS/WVAH)

Good Sunday!

Wow. What a ride we've seen over the past 48-72 hours! It started on Thursday--when an Arctic airmass settled overhead, only allowing afternoon temperatures to reach the lower 20s. With a gusty wind, too, it felt more like the single digits for much of the day. That was followed up by an overnight low of 9 degrees, although brief, a little after midnight on Friday morning. Friday itself was probably the most 'normal' day within this time-frame--with high's reaching the mid to upper 30s under an increasing canopy of mid to high clouds. Overnight Friday into Saturday morning, a healthy band of precipitation--mostly a chilly rain for Charleston, but some freezing rain and sleet, too, further north and east of town--moved across a good chunk of the region, as a strong warm-front neared from the south. In fact, temperatures--after starting in the 30s--rose towards 50 degrees around dawn from I-64 and south, and the warming didn't stop there. Despite a mostly cloudy day on Saturday, a stout southerly breeze, behind the warm-front, catapulted our temps into the spring-like mid to upper 60s! Those numbers weren't done, either; as a strong line of showers and even a few thunderstorms--along the front--neared from the west after Midnight, temperatures spiked into the lower 70s early on Sunday morning! The front moved through around 3-4 AM, bringing 40-50 MPH wind-gusts, heavy rain and even some thunder and lightning. By dawn on Sunday, temperatures rapidly changed again; this time, they dove nearly 30 degrees to around 40F to start the 18th of December. By Sunday afternoon, after a band of chilly rain, sleet and even a little snow less than 12 hours after 70F (!), our numbers plummeted to around 30 degrees. Is that enough drama!? That brings us to tonight and the rest of your Christmas Weekend forecast!

TONIGHT: Mostly cloudy and chilly with some patchy freezing drizzle and/or a few flakes early on--especially east into the mountains. Watch for icy spots on untreated roads and sidewalks. Low: 25.

  • Tricky cloud and resultant temperature forecast tonight, as a strong high-pressure tries to nudge closer from the west late. Regardless of the exact overnight low's towards dawn Monday, temperatures area-wide will be below freezing. This is of some concern since our region saw over an inch of rainfall during the past 24 hours, plus there was no sunshine today to dry the ground out; almost any winter night can have some patchy black ice here and there, but given the aforementioned conditions, tonight's risk appears to be higher than usual. If driving overnight towards Monday morning, just use caution, slow down some and give yourself more time--better to be safe than sorry, especially along those back-roads. Precipitation-wise, a touch of freezing drizzle and/or a few flurries may be around early on given a moist, northwesterly, upslope flow--especially across the higher terrain--but models show the moisture depth turning increasingly shallow--so shallow that precipitation formation appears unlikely after 1-2 AM. Will the moisture be shallow enough to erode the remaining stratus clouds, though? If so, then my forecasted low of 25 may be too high; if not, then temperatures will stay a little 'warmer' in the upper 20s to around 30. Feel that the clouds, given the wind-flow veering more out of the north-northeast, will at least get some breaks in them late--so felt that the 'down the middle' approach should work best. Regardless, it's cold-enough for some icy spots--so just use caution if driving.

MONDAY: After a cold start with some clouds around, turning partly cloudy and chilly in the afternoon. High: 34.

  • Expecting some low stratus clouds to be around to start the day--but they should be breaking up some, as our wind will have shifted more out of the north-northeast and the moisture depth pretty shallow. This means a cold start to the day in the mid 20's for most. Watch for a few icy spots early on given the cold temperatures and leftover moisture from Saturday night's rainfall--which was above 1 inch for many communities. How much do those low clouds break down altogether, though, is an interesting question given a noticeable temperature inversion (warmer air up above) between the 5 and 3 thousand foot layer. Despite this warmer layer of air aloft, however, I think the moisture depth is simply too shallow and the wind direction/NNE/ not favorable enough to sustain this thin layer of stratus clouds. As a result, I do expect increasing sunshine during the late-morning and early afternoon. This temperature inversion makes me want to think that maximum temperatures may underachieve some in the afternoon due to weaker mixing from aloft; model guidance shows high's reaching 36 to 37 degrees, but I decided to cut a few off given a weaker and more stagnant boundary-layer flow. Furthermore, some high clouds should stream up from the south later in the afternoon--which may tamper insolation just enough to make this cooler trend more likely. It's a quiet day, though, with the high-pressure drawing closer and the deep moisture well towards our east! Winds will be very light.

TUESDAY: After a cold start, mostly sunny and milder in the afternoon with a slight breeze. High: 50.

  • Expecting a cold start to the day here--mostly in the lower 20s--as the night prior will have provided mostly clear skies, little, if any, wind in the lower atmosphere and dry air thanks to a high-pressure overhead. This bodes well for us in the afternoon, though! Model guidance shows the high-pressure moving towards our east and the Mid-Atlantic then--which will allow our low-level winds to shift more out of the south. This slight downsloping flow, along with a good amount of sunshine given a mostly dry atmospheric column, should yield temperatures higher than the current mos guidance numbers; they're suggesting high's around 47-48F. Only a few, high, cirrus clouds may pay us a visit late--as a fast-moving upper-air disturbance races across the northern Great Lakes region. Simply no deep moisture and/or lift from this system around here, however--so a quiet day!

WEDNESDAY: Mostly sunny and mild with a slight breeze. High: 55.

  • Expecting another chilly start here, as a high-pressure will be with us from the night prior. Like Tuesday, though, this new high-pressure building in means a very dry atmospheric column--which will yield bright sunshine again! Model guidance does show another quick-moving low-pressure scooting across Wisconsin and northern Michigan in the fast zonal flow aloft, but the most it would produce for our region would be a few, high, cirrus clouds. If anything, this low-pressure--in conjunction with the high-pressure moving towards our east--should allow for a southerly breeze to develop; this downsloping flow should be a bit more than Tuesday, so expecting high temperatures to reach the mid 50s--not bad!

THURSDAY: Increasing clouds and a bit breezy. Scattered rain showers, mixing with and changing to a little snow late, especially across northern and eastern counties. High: 48.

  • Models show a fast-moving low-pressure scooting across the Great Lakes and into New England here. As it does, it looks like a front will cross our region early in the day. While the best upper-level energy and deepest moisture will stay towards our north closer to the parent low, sufficient enough low-level moisture and some frontal forcing may allow for an isolated rain shower or two--especially further north and east. The warmest part of the day should occur early on out ahead of the front--that's when a southwesterly breeze may push us close to 50 degrees. By the afternoon, however, models show the front racing off towards our east--this will allow the wind to veer more out of the west-northwest; this upslope flow, along with good moisture in the lower atmosphere and a brief shot of colder air should allow for a few flurries and snow showers to occur across northern and mountain counties to end the day. Little, if any, accumulation is expected there at this time. Otherwise, skies will be mostly cloudy across the lowlands as temperatures fall into the upper 30s to lower 40's behind the front. A few flakes may fly at times for the lower elevations, but it looks minimal at best.

FRIDAY: Mostly sunny and fairly mild. High: 52.

  • After a chilly start, it looks like the perfect travel day for Christmas! Models show a large area of high-pressure planted over the Mid-Atlantic and Ohio Valley regions--which will promote a very dry atmospheric column given the strong sinking air associated with it. This means bright sunshine and a dry day! Better yet, winds will be very light, too, so not seeing any issues in the sky or on the ground. Projected high of 52 degrees may be a touch conservative when all set and done due to the progressive nature of the Jet-Stream and an upstream wave of low-pressure developing across the Central States. Some high cirrus clouds may stream in from the west by evening-time in response to this system--foretelling of some weather changes for Christmas Weekend.

CHRISTMAS EVE SATURDAY: Partly sunny, mild and a bit breezy. Scattered rain showers possible, especially late in the day. High: 57.

  • It looks like a mild day here before Santa's big night! With a large area of high-pressure off of the Mid-Atlantic, our wind should shift more out of the south, so expecting temperatures to rise further--despite some mid to high clouds increasing in a broad warm-air advection regime. This wind direction will also bring some moisture up from the south, too, and probably sufficient enough--especially given some upper-level disturbances crossing, too--for some rain showers later in the day. The speed of this system is in question, though--but I wouldn't be shocked if it trends faster given the zonal jet-stream flow that is foreseen by the long-range models currently. The rain, if it does happen, doesn't look torrential--sort of scattered and fairly light at this point. For late-December standards, it looks like a mild night for Santa in towards Sunday morning; with low clouds persisting and a light, southerly wind--overnight low's probably won't fall below the mid 40s. A few rain showers and some fog may be around given the abundant low-level moisture.

CHRISTMAS DAY SUNDAY: After morning clouds and rain showers, turning partly cloudy, warm and a bit breezy for the 2nd half of the day. High: 63.

  • As you would expect--model differences this far out, but the general consensus looks to be a warm one. This is especially true with the ECMWF (European model), which shows a deepening area of low-pressure across the Central Plains. This set-up would induce a broad southerly flow across much of the Eastern United States--that means unseasonably warm temperatures, but also an initial surge of moisture from the south with a warm-front. Based on this scenario, a band of rain showers--and possibly even some thunder with some elevated instability--would cross early in the day (nothing like last Christmas is expected, though--when flooding occurred!). This activity at this point looks pretty transient, though--mostly due to the fact that the low-pressure in the Central States deepens and tracks further northeast. In the wake of this warm-frontal arm of precipitation, a southerly wind--along with at least filtered sunshine--should cause temperatures to surge into the spring-like low to mid 60s! No White Christmas :( but at least pretty warm!

Have a great night and take care!

WCHS Meteorologist, Brandon Stover

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