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Pattern Reversal...About To Turn Wet


FoothillsNC

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I started noticing the GFS hinting at this a few days ago and all the models are in rock solid agreement that a weakness will linger in the 5H height field over the lower Miss. Valley, and this means the Southeast will be sandwiched between 2 main ridges. One out west and one offshore (Bermuda Ridge) that grows stronger and more pronounced with each day next week.

First, we have to deal with a couple more brutal days of heat, and its worse the further north you are (Ky, Tn, VA, NC) but as the front approaches and squeezes this hot airmass or pinches it, deep easterlies will begin in SC, GA and work westward, eventually winding up with a lot of low level moisture situated in the Tenn. Valley down through Texas. Actually, that process is about to begin here soon. So by Sunday, the front it coming in and will come to a stall, intercepting the moisture and work on the dropping and lowering height fields, so storms and showers are going to erupt in broad fashion, beginning in Mo, Ok, Ark and west Tn/Ky, then by next week, the pattern will be stalled.

There's a chance of a weak mid level low cutting off somewhere in east Texas, La or the Gulf region, but even without that, the pattern is definitely changing. Temps will drop to more normal readings, but more importantly the Gulf is going to open up completely. Dewpoints are going to be in the 70 to 75 degree range, day and night, over most of the Southeast and Tenn. Valley by Tuesday so the afternoons will see the moisture bubble up into puffy cumulus, against a rich blue sky, and once the LCL’s are reached, the skies open up and downpours are unleashed. A similar pattern to what’s on tap is June 2005, where there was major rain totals in the Southeast. Daily showers and even small showers well into the night, in a rich, soupy airmass, so these won't be Garden variety afternoon pop-ups neccessarily.

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June 2005:

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Atleast briefly , we're heading back to some 1971-2000 climo type of maps at the surface and aloft. Lately, we just can't keep this type of look going long enough to ever really pull most of us out of the drought. I don't remember many Summers since after 1998 that we have this look, but before 1998, I remember almost all of them being "climo" like this. Typical southerly flow. Its also the reason east Alabama , through the heart of Georgia and western, central SC can't get any meaningful rains. By far, we've mostly been under ridging or the troughs have been right along the east coast, which isn't good for keeping precip going. Thats because more often than not, the Summers since 1998 in the Southeast have been dominated by higher than average heights, and winds aloft and at the surface from some component of westerly. West and northwest winds aren’t good for rain chances since theres a large landmass west of this region, and the mountains create a block to intercept what moisture there is, and also further dries out the region downstream in Georgia and especially the Carolinas. Depending on where any specific ridge is at any specific time changes which region is the dryest. Currently, the mega ridge that has sweltered the Plains favors extreme dryness and northwest flow that blocks most of eastern Alabama, the heart of Georgia and South Carolina from receiving much rain, especially compared to climatology.

July (mean flow 1971-2000)

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There’s strong reason to believe (for this forecaster) that the pattern will actually bring extensive moderate rains, and in some broad areas possibly some flooding rains by late week. The long lived nature of the southerly flow and weakness aloft in the lower Mississippi Valley could evolve into a weak upper low that gets caught and remains stationary between Louisiana and Alabama. This type of 5H flow, combined with the big Bermuda Ridge to the east, pumping in moisture all the way from the Caribbean, the cooler upper temperatures and the flow from the warm, rich Gulf will most likely ensure a drought-busting wet pattern for a broad region from Texas through the heart of the Southeast up into the MidAtlantic region.

As we get into next week, we can look closer at exact locations for the heaviest rain totals. Usually the north Ga mountains and southeast slopes of the Apps in sw NC, nw SC do very well in this flow, with flooding a concern at some point. Most of the Southeast can handle 3 to 6" of rain next week, but a few folks will get too much, probably over 10" by the end of next week. (with more yet to come if GFS is right). I think many folks forgot how common rain used to be, and this upcoming pattern reminds me of the end of the 2002 drought when in August, it began raining here, and never really stopped. A true record setter in 2003 began Fall of 2002. I'm not saying we're going to be that lucky though.

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Only time will tell if this is the beginning of a long lasting change, or it's just a diamond in a coalfield. With El Nino looming, I do think we're atleast due for an average wet Winter (remember rain averages dropped several inches per year though in some places as of the new climate norms).

More info at the site wxsouth.com

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GSP is on board with Robert. Here are parts of the overnight.

.SYNOPSIS...

AN UPPER LEVEL HIGH WILL KEEP HOT TEMPERATURES AND AFTERNOON

THUNDERSTORM CHANCES ACROSS THE WESTERN CAROLINAS AND NORTHEAST

GEORGIA THROUGH THE WEEKEND. SOME RELIEF MAY BE ON THE WAY FOR NEXT

WEEK AS A COLD FRONT IS EXPECTED TO DROP DOWN FROM THE NORTHWEST ON

SUNDAY NIGHT AND MONDAY. THE FRONT WILL BECOME STATIONARY ACROSS THE

AREA THROUGH THE MIDDLE PART OF NEXT WEEK.

THE DEVELOPING UPPER TROF OVER THE OH/MS VALLEY WILL

RESULT IN AN INCREASE IN MID/UPPER FORCING OVERNIGHT. ON MONDAY...

DEEPENING MOISTURE AND IMPROVING SUPPORT FOR CONVECTION AS A FRONTAL

BOUNDARY LAYS DOWN ACROSS THE CAROLINAS/MID ATLANTIC SUGGESTS THAT

PRECIP WILL BE LIKELY ACROSS AT LEAST THE MTNS AND FOOTHILLS. THE

BETTER COVERAGE AND EXTENSIVE CLOUD COVER SHOULD KEEP TEMPS A

CATEGORY OR TWO COOLER THAN SUNDAY. HAVE KEPT A CHANCE OF PRECIP

ACROSS THE ENTIRE FCST AREA THROUGH MONDAY NIGHT AS ADDITIONAL

DEVELOPMENT COULD HAPPEN AT ANY TIME.

THE NEW GUIDANCE THROUGH THE MEDIUM RANGE

CONTINUES TO SUGGEST A PERIOD OF RELATIVELY COOL TEMPS WITH A GOOD

CHANCE OF PRECIP FOR TUESDAY THROUGH FRIDAY. THE UPPER PATTERN SHOWS

A WEAKNESS BETWEEN A HIGH AMPLITUDE RIDGE OVER THE INTERMOUNTAIN

WEST AND RIDGE OFF THE EAST COAST. THE POSITION OF THE TROF AXIS

SHOULD GIVE THE CAROLINAS A STEADY SUPPLY OF WEAK SHORT WAVES AND

KEEP THE RIGHT ENTRANCE REGION OF THE UPPER JET NEARBY. DEEP

MOISTURE AND PERIODIC FORCING SHOULD TRANSLATE INTO A THREAT OF

SHOWERS AND STORMS AT ANY TIME THROUGH THE PERIOD. NOT A COMPLETE

WASHOUT...BUT A PERIOD WHERE JUST ABOUT EVERYBODY WILL GET DECENT

RAINFALL A FEW TIMES AT SOME POINT TUESDAY THROUGH FRIDAY.

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Good post robert. By God, I'm going to pin it ;)

Preliminary HPC 5 day forecast looks good for NC. Now if it could only shift south a bit. 0z euro though looks real encouraging. Showing a rather wet pattern all the way through day 10. 06z gfs also has the front/wettest area right over north ga, into the upstate, and foothills of nc/piedmont up to greensboro into va...with 96 hour precip totals over 5 inches in spots via hour 192. I think we deserve it.

p120i12.gif

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Good post robert. By God, I'm going to pin it ;)

Preliminary HPC 5 day forecast looks good for NC. Now if it could only shift south a bit. 0z euro though looks real encouraging. Showing a rather wet pattern all the way through day 10. 06z gfs also has the front/wettest area right over north ga, into the upstate, and foothills of nc/piedmont up to greensboro into va...with 96 hour precip totals over 5 inches in spots via hour 192. I think we deserve it.

p120i12.gif

The HPC must also agree with Robert since they put an "X" in his back yard... :flood:

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Good post robert. By God, I'm going to pin it ;)

Preliminary HPC 5 day forecast looks good for NC. Now if it could only shift south a bit. 0z euro though looks real encouraging. Showing a rather wet pattern all the way through day 10. 06z gfs also has the front/wettest area right over north ga, into the upstate, and foothills of nc/piedmont up to greensboro into va...with 96 hour precip totals over 5 inches in spots via hour 192. I think we deserve it.

p120i12.gif

If I get a 1/5 of that I will be happy

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Wow, look at that max right over Nashville, TN, almost 10 inches of rain in a 120 hour window.

Yep...Canadian has a precip max over Central Tennessee...got a weak cutoff low developing curently over Memphis which will help focus precip in that region. The low should drift around the Mid-South and Southeast most of this week.

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GSP mentions flooding concerns in part of the overnight!

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...

AT 3 AM EDT MONDAY...A POSITIVELY TILTED UPPER TROUGH WILL EXTEND

FROM EASTERN CANADA TO THE LOWER MS RIVER VALLEY ON TUESDAY AND

WEDNESDAY. A VERY SLOW MOVING COLD FRONT ALREADY OVER OUR AREA ON

TUESDAY WILL BECOME STATIONARY BY WEDNESDAY...AND WITH ELEVATED

MOISTURE LEVELS ALONG THE FRONT...IT WILL SERVE AS A FOCUS FOR

PRECIPITATION. ALTHOUGH THE BEST INSTABILITY IS SOUTH OF THE

BOUNDARY...ENOUGH CAPE EXISTS ALONG THE LENGTH OF THE FRONT TO

SUPPORT CONVECTION OVER OUR AREA. GENERALLY THERE IS A LACK OF

ISENTROPIC UPGLIDE OVER THE FRONT...AT LEAST UNTIL WEDNESDAY

NIGHT...WHEN THE NAM FORMS A WAVE OVER THE TN VALLEY. INITIALLY LOW

LEVEL FLOW WILL BE FROM THE NW...BUT BY WEDNESDAY WINDS BECOME

UPSLOPE FROM THE ESE. AS CONDITIONS HAVE BEEN DRY LATELY...AND THIS

APPEARS TO BE A LONG DURATION EVENT...HYDROLOGICAL PROBLEMS MAY

DEVELOP GRADUALLY. MAXIMUM TEMPERATURES WILL RUN A BIT BELOW

NORMAL...WHILE MINIMUM TEMPERATURES WILL BE NEAR NORMAL.

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Ready for the rain! Going to get in a quick mowing this morning before the heat cranks up, knowing (and hoping) that if the forecast holds true, the grass is going to be too wet all week to even think about it. :)

MONDAY

scttsra60.png

Thunderstorms

Likely

High: 92 °F

MONDAY

NIGHT

ntsra60.png

Thunderstorms

Likely

Low: 70 °F

TUESDAY

tsra60.png

Thunderstorms

Likely

High: 85 °F

TUESDAY

NIGHT

ntsra60.png

Thunderstorms

Likely

Low: 69 °F

WEDNESDAY

tsra60.png

Thunderstorms

Likely

High: 82 °F

WEDNESDAY

NIGHT

ntsra60.png

Thunderstorms

Likely

Low: 68 °F

THURSDAY

tsra60.png

Thunderstorms

Likely

High: 81 °F

THURSDAY

NIGHT

ntsra60.png

Thunderstorms

Likely

Low: 67 °F

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Ready for the rain! Going to get in a quick mowing this morning before the heat cranks up, knowing (and hoping) that if the forecast holds true, the grass is going to be too wet all week to even think about it. :)

I did too. I figured if I didn't do it today, it wasn't going to happen for another week. But, boy, was it hot outside, even when I started at 8 AM!! I was sweating buckets out there.

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nothing's changed, as I can tell. All systems go. In fact, a minor damming event will help out some parts of Va, NC, SC and GA on the east side of a very weak 850 low in the Tenn Valley Wednesday night and Thursday, with a weak high and some 850 upslope. GFS has temps remaining in the 70s in much of VA and the Apps, even some 60's which is hard to buy really considering the airmass to the north isn't anything remotely cool....just goes to show you the model shows a pretty good setup for saturating the airmass totally. If there are breaks of sun, then that area won't remain quite that cool, but damming usually works out , esp. when GFS shows it lately. Either way, lots of rain and periods of showers. It's hard to trust HPC maps or stratiform looking maps as those this time of year are for just very general purposes. In Winter, those stratiform maps work out much better but in this setup up, I'd take them with a grain of salt. I generally think one part west of the Apps on the nw side of an upper low will be a max (possibly 5 to 10" total) and again somewhere in the Apps and foothills *maybe* the piedmont, but I've never seen a flood forecast work out at all in my neighborhood, so i'd wait to call for that. But the overall setup is pretty wet for most folks, with a max over the Apps and northwest NC, west VA especially. (including ne GA).

Just had a nice storm, dropped .48". Now the sun is out. Wed night/Thursday there is a potential for extremely heavy rains in GA/Carolinas on the east side of the broad weak circulation, combined with slight damming, but it will come down to meso scale effects as to which areas truly get the train going. I still think this will evolve into too much rain for some places (over 10" this week) and lots of 5" to 8" totals over a very broad region, possibly making this the wettest period overall in the Southeast since El Nino 2010.

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