Storm Forecast
Valid: Sun 04 Mar 2007 06:00 to Mon 05 Mar 2007 06:00 UTC
Issued: Sat 03 Mar 2007 17:39
Forecaster: TUSCHY

SYNOPSIS

Latest IR images ( 3d March 07 at 16Z ) already indicated a well developed depression SW of Ireland, moving rapidly towards the NE.
00Z OPC analysis bring this system to a powerful 958 hPa low at ~58N / 12W with an impressive wind field, covering most parts of western and northwestern Europe.
Strong WAA on its downstream side will bring very warm conditions to Spain and France, while cool and stable conditions can be found over eastern and northeastern Europe.

DISCUSSION

...W / NW Turkey...

Same scenario like yesterday. Thermodynamic profilers will become favorable for some low-end instability release mainly during the daytime hours. The focus for isolated to scattered thunderstorm development will be a southward racing cold front and attendant forcing should support a few thunderstorms even far inland over W / NW-CNTRL Turkey.
Gusts could locally reach severe criteria, but slim instability release will preclude the development of more organized storms.

...Parts of France...

First area to look for will be western France during the early afternoon - early evening hours.

Models agree pretty well in developing some low-end instability west of the Massif Central between 15-18Z. The main difference between the models looks like to be the degree of boundary layer moisture.
Will go with the somewhat more aggressive GFS, which did a good job yesterday regarding dewpoint forecast in this area . Yesterday's synop reports ( 16z ) support the more robust PBL moisture scenario with readings of 11-14°C.
Surface temperatures will probably reach 20°C and mid-level lapse rates will increase markedly during this time frame. Such strong diabatic heating could be enough for an isolated storm to overcome the pretty warm lower atmosphere layer.
Shear would be fine for storm organisation but confidence regarding the exact storm evolution / coverage is too low right now for issuing higher probabilities.

Thunderstorm chances will increase during the evening and night hours over western, northwestern and later-on over northern France.
Strengthening PVA and a cold front from the west will create a favorable environment for a few storms to form. The main inhibiting factor for more widespread thunderstorm development will be the very limited instability release.
This could be another dryslot event, but uncertainties regarding the PBL moisture and the strength of the forcing are still pretty high so will stick with a general thunderstorm area for the moment.
The main threat with each storm would be an isolated severe wind gust / marginal hail threat.

...W / SW / S United Kingdom...

The main focus for some thunderstorm activity will be between 18Z - 06Z, when a pool of pretty cold mid-level temperatures will cross UK from the SW.
Instability release will be very low and hence only a few thunderstorms will evolve, mainly over S / SW and W-UK.
An overlap of minimal instability / enhanced LL shear along the coastal areas of aforementioned regions will pose an isolated tornado risk, but expected storm coverage will be too low for warranting any higher probabilities.