Archive for March, 2011

SPC has region in outlook now

March 31, 2011

– the ECMWF run this morning was faster which leaves less of a window for some of the elements to come into one Monday for severe weather.

– the SPC has placed the region in an outlook for Monday

Day 4-8 Convective Outlook Graphics Issued on Mar 31, 2011

go back to previous post which shows the GFS putting all the pieces in a puzzle favorable for severe weather Monday.

Time for SPC to see the threat for Monday

March 31, 2011

This in my view for 4 days out looks pretty clear cut on the modeling and overall set-up were in for a severe outbreak. It’s 4 days out things can and do change with the most likely weather that far out. The memo to the SPC is the threat is present why no outlook, you have a 4-8 day severe outlook USE IT. Maybe by the time many of you read this there will be outlook we shall see.

Let’s look at some of the indices for BWG  on the 00z GFS ( the ECMWF has a close representation to this at least at the surface and with CAPE values on several of the model runs)

CAPE- 1798 ( unstable atmosphere)

CAP ( CIN)- 72 ( just enough to keep from to much convection forming)

LI/Showwalter -7 ( very unstable)

TT- 59 ( severe storms, tornadoes)

K-index- 37 ( favorable for thunderstorm delevopment)

SWEAT- 575 ( 400 is threshold for tornadic storms)

modeled storm type- supercells

LLJ- 58 kts, storm motion 56 kts ( both of which suggest gusty winds in excess over severe criteria  are possible)

Helicity- 515 ( very sheared environment which promotes rotation with storms, may however be to sheared)

This is by far the best combination of shear and instability we have had in quite some time if the modeling is correct. Dewpoints over 70*F and decent lapse rates should contribute as well. As far I’m concerned the risk is already a moderate for the region if all holds this could be a rare high risk day. Although odds of this set-up on this run holding are not good.

All eyes on Monday, Going warmer for Saturday

March 29, 2011

The only change I have from yesterday’s forecast (read below)  is to progress the trough further east on Saturday this means higher thickness values, NVA and clearing conditions. Skies should be mostly sunny with highs well into the 50’s much better than was outlined yesterday.

As for Monday it is the anniversary of one of the most noteworthy severe events back in 1974. The 12z GFS did it’s best to show a enviroment favorable for a widespread severe outbreak Monday. However the ECMWF after being more bullish has backed off on the instability. We’ll see how this plays out over the next few days. I was surprised not to see our region out looked for day 6, I expect an outlook for day 5 (Monday) to be issued Wednesday for our region by the SPC.

more cold wet weather

March 28, 2011

– a few places overnight saw the snow band, However convection robbed the moisture needed to produce this snow band

1. The next in a series of systems will bring another increase in clouds and a period of rain Tuesday night. Some areas in the far north may mix with snow as lows there will be in the mid 30’s, no impact expected with any wintry precip. Overall expecting precip totals around 1/4 inch of liquid. Highs should get into the 50’s Tuesday and around 50 Wednesday. I expect the rain to end early Wednesday with cloudy skies the remainder of the day.

2.  A blocking pattern will continue with high pressure over the great lakes providing cold flow with storms moving  from the  northwest diving southeast into the southern plains and off the east coast. The next one Brings a chance of rain for Thursday with lows in the 30’s and highs near 50.  Also this will be watched for a mix.  As for a big storm I think this will be similar to several times this past winter, to many systems will be competing over the same region, only so much energy over a given area.

3. Disturbances will continue to move through the region into the weekend. A disturbance Friday morning brings a chance of rain or snow with lows near 32 and highs in the 40’s. Saturday doesn’t much better with similar temps and a chance for rain or snow showers. I see many forecasts going in line with the ECMWF or even warmer later this week umm. I’m seeing sub-540 thickness overcast skies, nw flow and precip. As the LMK discussion says a lot will do with trough position . After this I do see one last false warm-up for a few days that is followed by another chill then spring by Apr 10th. My thinking is we are baking by easter.

Snow overnight again!

March 27, 2011

Right now the NAM and the short term HRRR and RUC models are showing  a band of snow overnight across southern KY. Thunderstorms are moving northeast from Arkansas and another period of precipitation is moving east from MO. These two along some lift should produce a heavy band of snow across portions overnight from 3-11 am. Evaporational cooling should allow for any mix to change to snow. A coating to 2 inches of snow could accumulate on grass in the circled region.

here’s a look at the NAM