Unsettled Weather Yet to Come

The weather pattern across the U.S. will stay very unsettled the next week or so as a highly amplified pattern dominates. A weak H5 wave will rapidly shift through the Ohio and Tennessee valleys late tonight and early Thursday with another wave of scattered showers. Best coverge of these showers will be across the southeastern half of our viewing area and points south.

This will be a fast moving system though, so sunshine and mild temperatures will return for the afternoon hours on Thursday as short wave ridging builds into the Ohio Valley.

Another, more potent system will drop into the southern plains by late Friday. The warm advection pattern that sets up in advance of this system will likely reach the area later Friday or Friday night. Showers and elevated thunderstorms are possible across our region as a weak lead H5 vort vobe and a 30 to 40 kt LLJ intersects a frontal zone that will be sloped over the lower Ohio Valley.

The main upper H5 system and its associated sfc storm will impact the region later Saturday afternoon and Saturday evening. It still looks like there will be a decent chance for some severe weather with this system. We'll keep you posted...

Jay

Cloudy... Cold... Some Snow...

Overrunning patterm has set up across the Ohio and Tennessee Valleys. The column looks like it will have no problem saturating across the southern counties of the viewing area (i.e. south of the Western Ky and Bluegrass pkwys) but north closer to the Ohio River (including the metro) there is a ton of dry air in place in the low levels, and it appears the dry air is going to win out.

So this is what we re looking for... a wintry mix of rain/sleet/snow developing for the southern regions of the viewing area. Still the potential for a couple of inches of wet snow (keep in mind the ground temps are pretty warm) mainly on grassy areas. This would include places like... Greensburg, Campbellsville, Lebanon, Hodgenville etc... Closer to Louisville, a few flurries or even a period of light snow may make it to the ground - but overall the dry air looks like it's going to be just a little to much to overcome so little / no accumulation expected.

This pattern continue into weekend but the column will warm substantially so all precip will be in the form of liquid.

Check out both the 06z snowfall outputs from the GFS and NAM. Amounts vary some but the placement is pretty much the same.

stay warm all

Jay

Turn The Heaters Back On... Snow Chance Increasing Late Thursday ??

Wow... what a change from yesterday ! Cold high pressure continues to build in from the Plains states. The air with this system is very cold for this time of year as temperatures have been below zero across the northern U.S. !! The cold high will dominate at the sfc but aloft it'll be a different story. A broad southwest flow will result with weak H5 vort lobes passing through. This will mean the high pressure pattern for us will be a "dirty" high, i.e. lots of clouds will prevail. As a result, temperatures will be quite cold for nearly mid-March as the lowest levels (H9 & H95) will cool to the -3 to -5 C range. Folks that means temperatures holding steady today or slowly dropping and staying in the 30s for tomorrow !! Bundle Up.

Speaking of tomorrow... even though high pressure will dominate at the surface, a series of H5 vort maxima (weak shortwaves) will move through the broad southwest flow aloft towards the Ohio Valley. The first such wave will reach the area on Thursday resulting in some WAA in the mid levels. This will increase the moisture / lift in the atmosphere which will lead to some precipitation mainly for the southern half of the WLKY viewing area Thursday afternoon and night. Looking at model sounding data, p-type would be in the form of snow !! Almost 80 on Tuesday to a snow chance 48 hours later - ahhhhhh life in the Ohio Valley !!

Model QPFs are in coming in quite impressive.... However, keep in mind it is March and the ground is pretty warm so actual accumulations will likely be cut down some. At this time (and of course this is still subject to change based on the exact track) snowfall would range from 1 to 2 inches near the Ohio River (including Louisville) and points south witha heavier band of 2 to 4 Locally 5 inch amounts along and south of the Western KY and Bluegrass Pkwys !! There is a ton od dry air just to the north so there will be a very distinct cutoff to the snow as you go north. If there is a shift in the track... it'll likely be farther north as this has been the trend the last couple of model runs. Of course, if this northward trend continues... that would place Louisville in the heavier snow band. Stay tuned.... Bottom line, it looks like snow lovers may have another snowfall to smile about.

This cold high pressure / southwest flow aloft pattern will persist into Friday so expect lots of clouds and continued chilly temperatures to round out the work week!

We'll keep you posted

Jay

Record Warmth... More Storms... Much Cooler Weednesday.

Another huge warm up on the way today as strong southwest winds ahead of a deepening system deliver record warmth across many spots of our region this afternoon. The record high temperature in Louisville is 77 degrees. We are forecasting a high of 79 !! Winds should turn rather gusty though as LLJ strengthens and pressure gradient tightens over the area.

This very energetic storm - which by the way is producing blizzard conditions in the Dakotas where temps are hovering near or below zero, will continue to race northeast this afternoon and tonight. The associated cold front will sweep our area late tonight and likely after 6z Wed.

Although instability will be rather modest over our area, the increasing frontal forcing along with the very strong bulk shear will be enough to produce a band of showers and storms. Some of these storms could be severe with the very strong wind fields in place. Greatest severe weather threats will include; gusty, straight line winds and hail. Timing is expected to be from 03z in the northwestern counties to around 06 z in the Louisville area to 09z in the far southeast. In other words from 11pm to 5am across the viewing area (~2am in the metro). Much colder air tomorrow as temperatures drop quickly into the 40s

Check out the 10am sfc chart across the Plains... That is impressive !!

Also here is SPC's svr outlook and discussion...

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0758 AM CDT TUE MAR 10 2009

VALID 101300Z - 111200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE ARKLATEX NE INTO LWR
MI...

...SYNOPSIS...
PATTERN EXPECTED TO SOMEWHAT DEAMPLIFY OVER THE LWR 48 BEGINNING
THIS PERIOD AS FAIRLY POTENT CO SHORTWAVE IMPULSE ACCELERATES ENE TO
THE UPR GRT LKS...AND LARGER SCALE TROUGH CENTERED OVER THE CANADIAN
RCKYS RETREATS NE INTO CNTRL CANADA.

AT LWR LVLS...SFC WAVE NOW IN NRN MO SHOULD MOVE NE INTO NRN IL
LATER TODAY...BEFORE SUBSTANTIALLY DEEPENING AND ACCELERATING NNE
INTO ERN ONTARIO TONIGHT/EARLY WED. AS THIS OCCURS...TRAILING COLD
FRONT LIKELY WILL INTENSIFY AND SURGE SEWD...REACHING THE WRN SLOPES
OF THE APPALACHIANS...NRN AL...NRN LA...AND E TX BY 12Z WED. THE
FRONT SHOULD SERVE AS THE MAIN FOCUS FOR TSTMS THIS PERIOD.

...ARKLATEX NE THROUGH THE MID MS VLY INTO MI...
WARM ADVECTION SHOWERS/STORMS IN WAKE OF LEAD UPR DISTURBANCE NOW
OVER IND/MI EXPECTED TO PERSIST INVOF DIFFUSE WARM FRONT ACROSS
NRN/ERN MO AND PARTS OF IL/IND THROUGH MUCH OF THE DAY. STORMS
SHOULD ALSO DEVELOP SW ALONG MO COLD FRONT INTO NW AR AND PERHAPS NE
OK BY LATE IN THE DAY/EARLY THIS EVE. ALTHOUGH BOUNDARY LAYER
MOISTURE WILL CONTINUE TO SPREAD NE ACROSS REGION...CLOUDS AND
MODEST MID LVL LAPSE RATES WILL LIMIT DESTABILIZATION...WITH AVERAGE
MLCAPE LIKELY TO REMAIN AOB 500 J/KG.

THE GREATEST JUXTAPOSITION OF FAVORABLE INSTABILITY AND SHEAR FOR
SUSTAINED STORMS/SUPERCELLS LATE THIS AFTN SHOULD EXIST FROM NW
AR/SW MO NE INTO CNTRL IL. STORMS IN THIS CORRIDOR COULD YIELD A
COUPLE TORNADOES IN ADDITION TO LARGE HAIL/LOCALLY DMGG WIND.

BY EVE...THE EFFECTS OF WEAK INSTABILITY MAY BE PARTLY OFFSET BY
INCREASING UVV AS CO UPR TROUGH ASSUMES A MORE NEUTRAL OR SLIGHT
NEGATIVE TILT AND REACHES THE MID/UPR MS VLY. THE STRONGEST DPVA
WILL AFFECT WI AND UPR MI. BUT ASSOCIATED STRONG WIND FIELD /WITH
80-100 KT SW FLOW AT 500 MB/ WILL OVERSPREAD WARM SECTOR OF
DEEPENING SFC LOW. COUPLED WITH EXPECTED STRENGTHENING OF
ASSOCIATED COLD FRONT...SETUP SHOULD YIELD AN ENVIRONMENT
INCREASINGLY FAVORABLE FOR FORCED CONVECTION ALONG THE BOUNDARY FROM
SRN MI SW INTO IND...IL...SE MO...AND AR...AND AN ENHANCED RISK FOR
DMGG WIND/HAIL.

THE SVR THREAT SHOULD BEGIN TO DIMINISH LATE TONIGHT/EARLY WED AS
THE FRONT SURGES E BEYOND AXIS OF GREATEST LOW LVL MOISTURE OVER OH
VLY. THE SVR THREAT MAY LINGER A BIT LONGER FROM KY/TN SW TO THE
ARKLATEX...WHERE MARGINALLY UNSTABLE AIR WILL EXIST.

..CORFIDI/HURLBUT.. 03/10/2009

Have a great day..

Jay

Record Warmth... More Storms... Much Cooler Weednesday.

Severe Chances Later Today...

Potent H5 neg tilt wave will push from the Plains to the Great Lakes by tonight. Associated low pressure will track to our north as a trailing cold front sweeps east across the region later today and this evening.

Instability is rather modest but should be more than sufficient to sustain a line of storms - now to our west. Impressive 0 to 1 k shear values of 45 to 55 kts will be over the area as the line shifts east late this afternoon and early evening. SRH values will be off the charts as the line moves east so these storms will have the potential to produce damaging winds as well as isolated tornadoes. In addition, mid-level lapse rates that are quite steep just west of our area, should continue to advect east/northeast. This will also help sustain vigorous updrafts and potential for large hail....

Here's the morning SPC outlook...

Severe Chances Later Today...

Spring-Like Warmth Pushin' Our Way

Finally, warmer temperatures are pushing towards the Ohio valley the remainder of the work week and also into and through the weekend. A broad southwest flow will set up over our area as the "main action" shifts to the western U.S. A large trough will develop across the western U.S. allowing ridging to nose north from the Gulf of Mexico into our area. This will allow for big time warming across the Ohio Valley the next several days.
70s back in the forecast by Saturday and Sunday. For those of you running in the Anthem 5k... looks great this year - for a change !! Partly cloudy and warm - Enjoy !!

Precip wise....
Low level moisture returns really ramps up on Friday. Mid / upper levels dry and with overall ridging in place, just some spotty drizzle possible on Friday.
Sunday afternoon: approaching cold front and decent H5 energy passing through the upper midwest will mean decent chances for showers and storms for the second half of the weekend.

Bottom line... enjoy Saturday -it looks like a great day shaping up with a mix of clouds and sun, warm breezes and temperatures in the mid 70s.

Jay