Storm Forecast
Valid: Sat 30 Jul 2016 06:00 to Sun 31 Jul 2016 06:00 UTC
Issued: Sat 30 Jul 2016 06:22
Forecaster: TASZAREK

A level 2 was issued for NW Russia mainly for large hail, severe wind gusts, excessive precipitation and tornadoes.

A level 2 was issued for N Spain mainly for large hail, excessive precipitation and severe wind gusts.

A level 1 was issued for the belt extending from N Spain to SW Poland, mainly for excessive precipitation, large hail and in lesser extent for severe wind gusts.

A level 1 was issued for Estonia, Latvia, NE Lithuania, N Belarus and parts of W Russia mainly for excessive precipitation and in lesser extent for large hail and severe wind gusts.

A level 1 was issued for parts of W Russia mainly for the large hail, excessive precipitation and in lesser extent for severe wind gusts.

SYNOPSIS

Long wave covering area from British Isles up to NW Russia with a low centred over W Scandinavia induces a zonal flow in the most of the W and CNTRL European area. Polar air mass is located in the NW Europe while the tropical one covers S, SE and E Europe. The belt of highest instability with a quasi-stationary frontal boundary stretches from N Spain, through S France, S Germany, S Poland up to NW Russia where a cyclogenesis with an active cold front takes place. On the eastern flank of the developing low an advection of warm and moist airmass up to White Sea will proceed. Main jet streak zones stretches from N France up to Denmark, and from Canary Islands to E Iberian Peninsula, and both are out of main instability zones (or with strongly capped CAPE areas). However slightly increased mid-level flows (on the edges of jets) surging DLS up to 15-20 m/s are located in N Spain, CNTRL and S France, and Alpine area. Mid and low level wind shear and helicity increases in the afternoon hours in NW Russia along with developing low. Severe thunderstorms are expected in the both aforementioned areas in the afternoon hours.

DISCUSSION

... belt from N Spain to SW Poland...

A developing instability in a warm sector and along quasi-stationary frontal boundary, all-together with 11-13 g/kg MIXR, > 7 K/km lapse rates and a diurnal heating provides CAPE up to 1500 J/kg (locally 2000-2500 J/kg). In N Spain, CNTRL and S France, CAPE zones overalp with 15-20 m/s DLS providing conditions for multicell and supercell thunderstorms capable of producing large hail and severe wind gusts. Given locally enhanced PW values to 35-40mm, an excessive precipitation and local flash flooding cannot be ruled out as well. Although storm and CAPE coverage in N Spain will not be large, a level 2 was issued for N Spain mainly for the chances of 5 cm hail given steep lapse rates and 20 m/s DLS. Most of the storms will develop in the afternoon hours, except S and E France where CI with DMC is expected in the late afternoon/evening hours thanks to the passage of the shortwave. Although MCS during evening and night-time in this area is not ruled out, a level 2 is not issued mainly due to dominating elevated convection where a risk for severe weather is limited. The main threat should refer to excessive precipitation and possible severe wind gusts. On the E flank of the lvl 1 area, a DLS will be lower (~ 10-15 m/s) that lowers the possibility of supercells with large hail. However, due to CAPE up to 1500 J/kg and slow storm motion, a threat for excessive precipitation and local flash flooding will exist. Thanks to elevated values of delta theta-e, a local downburst/microburst severe wind events are possible as well. Thunderstorms in the belt from SE France to Czech Republic may remain electrically active until night-time hours.

...Estonia, Latvia, NE Lithuania, N Belarus and parts of W Russia...

Similiar as in CNTRL Europe, a CAPE up to 1000-1500 J/kg covered in weak mid-level flow (DLS ~ 10 m/s) will pose a threat of multicell/pulse thunderstorms capable of producing excessive precipitation and severe wind gusts within downbursts/microbursts. Due to weak shear but moderate CAPE, a threat for large hail will be limited to 2-3cm hailstones. Thunderstorms should develop along with diurnal heating and fade in the evening hours when instability drops.

...W Russia...

Along with the northward warm and moist air advection and a passage of the shortwave, instability in the warm sector will develop to 2000-3000 J/kg. CI is expected in the afternoon hours thanks to diurnal heating, cyclogenesis and PVA lobes. Most of the S and CNTRL area in lvl 1 will be covered with 10-15 m/s DLS that with moderate to high CAPE will create a threat for large hail, downburst/microburst severe wind gusts and an excessive precipitation. A developing low on the edge of NW Russia will surge helicity and mid to low level wind shear (LLS > 10 m/s). On its eastern flank in a warm sector, a supercell thunderstorms capable of producing large to very large hail, severe wind gusts and tornadoes are possible. MCS propagating to White Sea in the late afternoon hours is possible. Thunderstorm activity in the rest of the area should drop in the evening hours.