Tuesday, April 15, 2014

No chase but a clearly defined frontal passage

I chose not to chase today given that the best setup for doing so is well east of where I would consider going. But...I was out and about the Roanoke valley this morning and got to experience the cold frontal passage. Here's what it looked like ~10:40 a.m. looking southwestward from the Hollins vicinity:

FROPA was very obvious as the wind suddenly swapped around from southerly to northwesterly and the thermometer plunged while I was outside my vehicle snapping photos. Now the question is how long the current pattern will take to reset and provide the next chasing opportunity. It may be a couple of weeks from now which would mean April is pretty much over for Virginia chasing.

Monday, April 14, 2014

Tax Day chase?

April 15th is notorious as Tax Day but could it also be a chase day in 2014? I haven't been impressed with the model solutions for my chase region altho' the SPC is calling for a 5% chance of severe storms over the far western Piedmont of Virginia:

I'm concerned that the heavy rainfall forecast ahead of the approaching cold front will squelch convection, impair visibility, and prevent discrete storms west of the I-85 corridor. And since I'm not willing to go to that far east (too far, too populated, too many trees, etc.) without a REALLY good setup this isn't tempting me much.

Of course if tomorrow's RAP and HRRR runs look good all bets are off...

Friday, April 04, 2014

The short answer for today's chase: B-U-S-T

Things started out well this morning when the SPC issued a Slight Risk for my target area, but when I combed through the models I didn't see anything to justify that designation either at the surface or upper air. Sure enough the midday update dropped the Slight Risk and went to a "See Text". I wasn't concerned since I have had luck with these low end setups previously...but such was not to be.

After waiting and watching multiple runs of the HRRR and RAP models I decided to head east to Burnt Chimney in Franklin county. This HRRR forecast graphic for 7 p.m. illustrated what I thought I could intercept before dark:
The line segment straddling the NC/VA line showed in several successive runs so I felt confident that I could see something.

Unfortunately a major mitigating factor was the persistent overcast which pretty much squashed the forecast CAPE values. Thus the line tried to form as shown in this Burnt Chimney (BC) view:
But nothing much became of this other than some very light sprinkles northeast of BC after I'd already called it a BUST and headed home. Oh well...at least I didn't stray very far from home base for this one.

Wednesday, April 02, 2014

Updates on severe weather this week

If I had been chasing out in the Plains today my initial target would have been just north of the OK/KS line and east of I-35...meaning I would be in the middle of a tornado watch and chasing a rotating storm east of Arkansas City at the moment. Unfortunately I'm not out there so I have to focus on Virginia chasing opportunities.

Friday still looks good for southern and southwestern Virginia. Here's the 18Z GFS supercell composite for 5 p.m.:
The 18Z NAM has a bit more CAPE and shear for this same timeframe but either way storms still look likely. 

Thursday - tomorrow - may be a sleeper chase as a stalled frontal boundary lifts back northward during the afternoon. That will provide a shear zone with backed surface winds to go along with a modest amount of CAPE which could fire off a couple of strong rotating storms. I'll have to keep an eye on the HRRR and RAP models plus radar tomorrow.

Tuesday, April 01, 2014

This week it's Friday

There may well be another Virginia chase opportunity this coming Friday on the heels of three successive days of SPC Slight Risks to the west. A cold front will cross Virginia Saturday morning but uplift ahead of a 500 mb shortwave could trigger storms late Friday afternoon. The NAM is currently showing this forecast graphic for MUCAPE (>500 j/kg) and bulk shear (>40 kts) along the I-81 corridor at 5 p.m. Friday:

At the moment the shear looks unidirectional and generally in the direction of storm movement so that sounds a lot like a pre-frontal squall line. Still, it's worth keeping an eye on as an early April chase in the Old Dominion.