Category: Arctic Cold

Jan 18

Times Are Changing, Or Are They?

January-to-date is running milder than normal across the region- to the tune of 3.3 degrees (F).  This is after a frigid open to the month, as you recall.

conus_mtd_t2max_anom_2017The second week of the month warmed significantly and continues, overall, for the next week.

ncep_cfsr_noram_t2m_week_anomThe mid-January warmth is attributed to a roaring PAC jet which is currently helping flood the country with temperatures much more like spring than the dead of winter.  We continue to forecast 60+ this weekend across central IN.

Winter lovers, have no fear as changes appear to be in the offing as we go through the last few days of January and head into February.  The winter so far has featured conflicting signals that continue to try and compete with one another to take hold of the pattern.  Can we get these drivers to align in a way that would pull a more persistent trough into the east for the second half of the winter and, ultimately, set-up a sustained cold pattern helping make up for lost time in the snowfall department?  Time will tell, but we do note the following late month:

  • (+) PNA pattern
  • Sudden stratospheric warming event
  • High latitude blocking

All are encouraging for a shift back towards a wintry regime.  As always, the devil is in the details and we’re skeptical as to the longevity of these signals.  “Cautiously optimistic” would be the way to sum up our current feel longer-term into the month of February, but we’re not as bullish on lock and hold cold, wintry conditions at this time as what you may hear from some of our national compadres.  Understanding that various drivers can have a different impact mid and late winter as opposed to early is one thing.  It’s also important to note that long term modeling has been abysmal as of late and we want to tread through the next couple of weeks with caution to see whether or not the cold drivers can finally take hold.

Needless to say, at least through late month, one can see the significant changes take place at 500mb.

Thursday:

ecm_eps_z500a_noram_2This Weekend:

ecm_eps_z500a_noram_5Next Thursday:

ecm_eps_z500a_noram_9Next Weekend:

ecm_eps_z500a_noram_11The pattern begins in the short-term with a look that will power anomalous warmth through the weekend, along with renewed rain chances Thursday night into Friday (another 1″+ for most), but begins to shift next week towards the colder look.  The 2nd (weekend) storm system will be significant and poses a severe risk to the southeast region.  Modeling has backed away on the heavy rain threat Sunday, but showers will be around early next week along with very windy conditions (40+ MPH gusts).  Blocking is forcing the low south.  By the time we get to next weekend, the pattern has done a 180 and in a position to drill unseasonably cold air back into the central and eastern portions of the country.

As far as storms go later in the period, it’s far too early to discuss specifics, but the pattern seems to be one that will promote the chance to get into the act on high-ratio producing clippers.  It’s the first time we can say that this year.  Time will tell…

Permanent link to this article: https://indywx.com/times-are-changing-or-are-they/

Jan 12

Weekend Ice And Heavy Rain Next Week…

Screen Shot 2017-01-12 at 7.08.19 AM

Highlights:

  • Turning colder
  • Freezing rain develops Friday night
  • Wet times continue

Active Times; Excessive Rainfall Risk Next Week…The overall weather pattern remains very active AND very wet.  By the time all is said and done, an additional 3″ of rain is possible for a widespread portion of the region by the middle of next week, with locally heavier amounts.  Lets time it out.

The focus in the shorter-term is for colder air to build in.  Temperatures today will fall (after a spring-like feel during the wee morning hours).  We’ll be in the 30s by mid to late afternoon and below freezing later this evening.  Arctic high pressure will continue to force cold, dry air south across central IN as we wrap up the work week.  At the same time, warm, moist air aloft will ride over the cold air trapped at the surface and trouble looms by Friday night.  We expect light freezing rain to develop after dark and continue into Saturday morning.  As disturbances move along the arctic boundary, additional precipitation (mostly light) will overspread central Indiana from time to time over the weekend.  We want to continue to reiterate that a 1-2 degree temperature difference will mean a tremendous difference between additional ice accumulation and plain ole cold rain.  Thinking is that the freeze line will shift north of the I-70 corridor Saturday afternoon before settling south towards I-70 again Saturday night and Sunday morning.  We still have time to fine tune things, but as of now it seems likely that anywhere from 0.10″ to 0.20″ of glaze (freezing rain) will be possible across most central IN communities Friday night into Saturday.

We’ll get rid of the freezing rain early next week and bust back into a warm southwesterly air flow.  Models are struggling with the precise details of how things evolve in the early-mid week period, but confidence remains very high on continued wet times.  In fact, the GFS pulls a slug of 1.5″ precipitable water values (PWATs) north into the state the middle of next week and suggest the heavy rain threat remains Tuesday and Wednesday.  By the middle of next week, we have to start becoming concerned for flood potential across the region.

Hang in there, we’ll see the sunshine return…some day.

Upcoming 7-Day Precipitation Forecast:

  • Snowfall: 0.00″
  • Rainfall:  2.50″ – 3.00″ 

Permanent link to this article: https://indywx.com/weekend-ice-and-heavy-rain-next-week/

Jan 11

Icy Set-Up This Weekend…

Unfortunately, a strong arctic high still looks like it’ll descend into the upper Mid West Friday before moving east over the Great Lakes (Saturday) and into the northeast (Sunday).  This will help shove a cold front south to the upper TN Valley Friday and dense, cold air will bleed south to encompass central Indiana as we wrap up the work week.  As we progress into the weekend, warm moist air will override the shallow cold air locked in place at the surface.  Ripples of energy will move along the boundary and periods of more concentrated, steadier precipitation will fall.  Significant ice accumulations (greater than one quarter inch) will be possible for portions of central Indiana.

gefs_ptype_ens_ky_14GFS ensemble members above show the overall good agreement on a central IN ice set-up for portions of the weekend.

Timing:  As of now, I think most of Friday is dry and cold before moisture overspreads the region late Friday night into Saturday.  Additional waves of moisture will push through the region during the second half of the weekend, as well.

Confidence:  We have very high confidence on at least light to moderate icing in the Friday night – Saturday time frame, but confidence on additional icing thereafter begins to drop, thanks to disagreement in modeling.  The GFS is warmer for the second half of the weekend and would reduce the threat of significant ice build-up as some brief thawing would be in place in between waves of moisture thanks to temperatures rising into the middle 30s.  However, the European model is much colder and keeps IND below freezing Saturday and Sunday, with nearly half an inch of liquid during that time frame.  That’s downright concerning and would result in significant issues with potentially downed tree limbs and power lines.

We do have concern the European could have a better handle on things right now.  Modeling is notorious for underestimating the strength and depth of the cold air with these arctic highs and similar overrunning events of the past.  Stay tuned.

Impacts:  Greatest concern right now is for icing on exposed and elevated surfaces (bridges, tree limbs, power lines, etc.).  With the milder air of midweek, along with marginally cold air, it’s possible crews will be able to keep roads passable during this event.  Additionally, something else to consider is the rate of precipitation.  While bad for elevated ice build-up, if precipitation rates are heavy enough, this can help reduce ice build-up on roadways.

Summary:  We still have concern for the potential of an impactful ice event this weekend through central Indiana.  Winter Storm Watches (and potentially Ice Storm Warnings) may be hoisted by the National Weather Service later this week for this event.  Despite an overall high confidence in at least some icing impacting the region, questions do remain in regards to the temperature profile later in the forecast period this weekend, and caution the slighted deviation in surface temperature can make all the difference to impacts.  At the very least, low pressure should pull out of the southern Plains early next week and this will serve to push enough warm air northeast to change everything over to plain ole rain early next week as we rise into the 50s.

Permanent link to this article: https://indywx.com/icy-set-up-this-weekend/

Jan 10

Prolonged Stretch Of Gloomy Weather…

screen-shot-2017-01-10-at-7-25-16-amHighlights:

  • Active stretch of weather begins
  • Moderating trend into midweek
  • Ice concerns Friday-Saturday

Sunglasses NOT Required…We’re entering the beginning of an active stretch of weather, with an extended period of overcast skies and gloomy conditions.  Let’s dive in and take the challenges one-by-one:

Showers develop this afternoon as a cold front moves into the state.  Ahead of the front, strong southwest winds will gust upwards of 45 MPH+.  A “big hair warning” is in effect.  🙂

A brief shot of colder air will arrive late tonight into Wednesday, but just as soon as it arrives, it’ll leave and temperatures will approach 60 Wednesday night as showers return.

Thursday will be a wet day with periods of rain and slowly falling temperatures during the afternoon/ evening.

Friday is much colder as the arctic front will be to our south, but most of the day looks dry.  Moisture will lift north Friday afternoon and evening and with cold air in place, the precipitation should take the form of a mixture of freezing rain and sleet.  Periods of freezing rain likely continue Saturday.  It’s far too early to discuss amounts and we also want to reiterate the difference of 1-2 degrees will mean a world of difference between areas dealing with ice versus a cold rain.  The “battle zone” looks to take place across central IN.  If you have travel plans Friday night and Saturday, please keep abreast of later forecasts and updates.

Regardless of whether or not we’re dealing with icy conditions across central IN during the first half of the weekend, temperatures will warm during the second half of the weekend and change any frozen/ freezing precipitation over to plain ole cold rain Sunday into Monday.

Upcoming 7-Day Precipitation Forecast:

  • Snowfall: 0.00″
  • Rainfall: 1.50″ – 2.00″

Permanent link to this article: https://indywx.com/prolonged-stretch-of-gloomy-weather/

Jan 09

Busy Weather Week; Ice Storm Potential Friday Into The Weekend…

screen-shot-2017-01-09-at-7-26-23-amHighlights:

  • Late night light freezing rain develops
  • Milder and wet through mid week
  • Ice storm potential on the rise late week

Feeling Downright Balmy Out…Temperatures this morning (writing this at 7a) are running close to 20 degrees above where we were this exact time Sunday.  20 degrees has never felt so warm!  🙂  This moderating trend will continue into mid week, including temperatures that approach 60 Thursday.  That said, we have a mini “speed bump” to go over tonight and that’s the opportunity for light freezing rain late tonight into the wee morning hours Tuesday.  Temperatures should go above freezing just before the morning rush Tuesday, but plan to leave additional time as slick spots may remain.  Once we clear the “speed bump,” it’s off to the races in the temperature department through mid week: around 50 Tuesday afternoon and around 60 by Thursday (that’s a late night high Wednesday in the upper 50s).  Periods of showers will come with the milder air, centered on Tuesday and late Wednesday into Thursday.

Unfortunately, the milder times don’t last long and we still forecast “trouble” late in the week.  The set-up remains unchanged as a big, sprawling arctic high pushes into Wisconsin Friday.  This will help “shove” the arctic front through Indiana before stalling along the Ohio River Friday into Saturday.  As this is happening, ripples of energy will help ignite periods of precipitation Friday into the weekend.  With cold air locked in at the surface, we expect the potential of a rather prolonged period of freezing rain developing late Friday and continuing into the weekend.  We still have time for things to change, but from this distance, the predominant precipitation type, unfortunately, appears to be freezing rain.  Stay tuned as this could be a high impact event.

Upcoming 7-Day Precipitation Forecast:

  • Snowfall:  0.00″
  • Rainfall:  1.50″ – 2.25″

Permanent link to this article: https://indywx.com/busy-weather-week-ice-storm-potential-friday-into-the-weekend/