MCS thunderstorm complex threat increasing for the next few days

1. On Friday a complex of thunderstorms known as a MCS clipped northern parts of the region with strong winds. This tracked on the edge of the heat ridge which has provided a hot and dry airmass and heat wave over our region. This airmass has resulted in sinking air and the development of a cap due to the hot and dry airmass and the prevention of thunderstorm formation. Along the edges of the heat ridge week disturbances and fronts can use the difference in airmasses to create clusters of storms. I expect this to be a threat over the next few days. However I still think the strength of the ridge keeps my optimism in check. Like today any thunderstorm cluster will have to come from the northwest and will struggle to move south being blocked by the strong ridge. Though by Sunday I could see the track of any MCS become more favorable regionwide for rain to dent the heat. Overall I’m going 40% northeast for rain chances and 25% for the rest of the region. Sunday 50% north and 40% elsewhere. This is higher than my forecast a few days ago. I’ll track any MCS’s as needed. The MCS’s may present a high wind threat due to a considerable amount of instability in the region.

Major Heat Wave Starting

Remember those heat tips off to the side.

1. Thursday highs should be well into the 90’s with sunny skies. humidity values will be very low with red flag warnings in effect as well. Burn bans are in effect. Strong winds will make for ideal fire conditions. Heat advisories are in effect for parts of the region as well.

2. For Friday Once again sunny skies. Morning lows will fall to around 70 due to the low humidity and clear skies but temperatures will rebound to around 100.

3. Saturday and through Monday may feature a additional slight chance for a storm but continued very hot with highs near 100 possible.

4. The heat wave breaks down slightly with chances of scattered storms Tuesday and for July 4th taking temps down into the 90’s. Looks like about 10 days before the heat shifts from over us back to the central plains.

5. The cold PDO is really throwing a curve ball in seasonal forecasting right now. This will influence any forecasting for fall and winter. The cold PDO is the main cause in the main ridge of heat further east than expected so far this summer. We may be looking at winters like 51-52 than 76-77 for winter analogs now since the PDO is not turning around like ENSO. This point would require more research.

Same old Hot and Dry, Does Debby Provide a Different Tune?

1. Tropical storm Debby has formed in the gulf. My timetable for development is off a bit but it continues the fast start to the Hurricane season. This is also the first system of the season which has a chance to influence our weather in about 5-7 days.

2. Monday a front will provide a glancing shot around a cooler airmass. This may knock highs down into the 80’s for some with low 90’s south. However moisture appears limited with the best lift well north of our region, only slight rain chances. Monday night with clear skies and low dewpoints, lows in the 50’s may be common.

3. Tuesday will be dry with highs in the 80’s. Perhaps a few northeast stay in the 70’s.

4. A very strong ridge of high pressure builds in for the remainder of the week. This should send highs back into the 90’s for the remainder of the week with lots of sun. Lows will gradually warm as well into the 60’s and even 70’s. The good news is humidity should stay low. Though highs Friday and Saturday could reach the upper 90’s, 100? Heat indices should only be slightly higher. High pressure ridges mean sinking air and a lack of convection till a front can break down the ridge. However tropical storm Debby is a player as well.

5. Right now modeling has three tracks on Debby.

A: Into South Texas- NOGAPS, JMA

B: Central Gulf coast hit, moisture spreads into our region next weekend. – ECMWF, yesterday’s CMC, UKMET

C: Up the east coast and out to sea- GFS, today’s CMC

Why the difference in track?

– Path C provides the early week trough picks the system up. I do not think this will happen and is a common bias in the GFS to do this with tropical systems.

– The movement is very slow and the system still sheared. This makes it hard for models to gauge what’s going on. I expect a slow organization in the next few days.

– The slight northward movement over the next day or so due to a more limited influence of the early week trough may make an almost westward track more in line with path B

– Frontal boundary next weekend may interact with a decaying center of Debby and break down the ridge. Path A provides the ridge holds firm over the south sending the storm due west.

For now much uncertainty exists regarding increased chances of needed rain from Debby. I want to see how the pattern evolves before committing to a forecast track.

This week? Summer as a Whole?

1. A few areas did better than expected getting some rain Sunday. I continue to think rain chances are few and far between. Perhaps a few stray storms Thursday and Friday. A stronger front should have limited moisture to work with early next week, not much better with rain chance. Rainfall deficits should increase by another inch in many areas this week. The drought in Western Kentucky is changing up my summer forecast a bit.

expected temperatures compared to normal for summer.

The EC weeklies agree with this through the middle of July. Previous forecast has more details.

Another heat wave coming

1. With that being said we’re three degrees below normal for the month. This should get us close to normal temperature wise. A lack of rainfall will continue to be the story due to a strong ridge of high pressure from the southern plains to northeast.

2.  Saturday and Sunday mostly sunny lows in the 60’s and highs in the upper 80’s. A week front may be enough for a stray storm, I think the ridge holds and suppresses most anything that could form.

3. Monday Through Friday will be hot and dry lows in the 60’s and highs in the low to mid 90’s.

4. For next weekend I’m anticipating a front to move through and cool the region. This week our rainfall deficit will continue to grow getting over 5 inches for BG and Lexington. However a tropical system this week has the potential to develop in the western gulf and may interact with the front to provide a chance for a good rainfall next weekend. I’m discounting the extreme solution of the 00z ECMWF which builds the ridge even further and sends highs into the 100’s. The 12Z is more realistic. and in line with other guidance.